components manufacturing methods [Archive]

jim beam

01-03-1970, 08:50 AM

bicycle_disciple wrote:
> I speculate this topic may have been beaten to death. I'm lazy to go
> over the innumerable archives of RBT, so let me shoot out the
> question.
>
> What manufacturing methods are being used in high end components these
> days and how do each one affect strength, failure due to fatigue,
> stiffness etc? I wonder if cranksets are cast at all in these days
> where cnc machining and so on is rampant technology to cut costs. Most
> cranksets I read about (Stronglight, Zero Gravity,FSA) talk about CNC
> machining and I've also heard some folks who think these methods don't
> produce enough strength and durability as forging or casting and so
> on. These days theres carbon every here and there, especially in
> carbon cranksets, so what kind of manufacturing is done here to make
> these parts? I'm not only looking for an answer to high end components
> which could be mostly made in-house, but also the ones that people
> with an average budget ride everyday, and whose parts are outsourced
> to Taiwan, China etc...
>
>
> -BD
>

you seem to be confused about how cnc is different from casting or
forging. cnc is simply a machining process that's used for finishing,
not for basic form creation like casting or forging.

briefly, forgings are much better in fatigue than castings. a subset of
casting is thixoforming, which is better than straight casting, but
still not as good as forging. thixoforming is very fashionable with
certain manufacturers like avid.

for fatigue, high quality carbon fiber is best, followed by cold
forging, then hot forging, then thixoforming, with casting a distant
runner-up. carbon that is basically a veneer on top of an aluminum
substrate is debatable.

Chalo

01-03-1970, 08:50 AM

bicycle_disciple wrote:
>
> What manufacturing methods are being used in high end components these
> days and how do each one affect strength, failure due to fatigue,
> stiffness etc?

There are more factors than manufacturing method that dictate the
properties of a part.

Know first of all that stiffness is a product of basic material type
and part dimensions, not manufacturing technique. A cast stem made
from weak, soft aluminum would be as stiff as a cold-forged and
machined stem made from 7075-T6 alloy, if they both had the same
shape, size, and weight. So for stiffness, you are concerned about
gross categories of material (e.g. steel vs. titanium vs. aluminum vs.
magnesium), part weight, and part form. It makes no difference how
the part is made.

For the purposes of the discussion, I am going to exclude frames,
forks, rims, etc-- things that can be considered structures unto
themselves. Such parts have more in common with each other than they
do with components that function as mechanisms.

The highest quality components these days are either cold forged from
metal or laid up and cured from carbon/epoxy. (I'm not going to talk
about carbon parts because I think they're goofy.) Forging is
basically smashing material into the desired shape between tools or
forms made of harder stuff. It makes the metal stronger and reduces
the size and effect of internal flaws, as well as being a material-
efficient way of making parts. The tradeoff is that the dies (shaped
tools) for forging are very expensive, and the finish quality of parts
in as-forged condition can be pretty crude.

Forging can be done on "cold" metal (in the same microcrystalline
state as at room temperature), which causes work hardening--
strengthening-- of the metal itself. It can also be done hot, with
metal that is softened and easier to smash into shape. Hot forged
parts have the structural advantages of "grain" that follows the shape
of the part and diminished internal flaws, but the metal will be in a
relatively soft state after the part cools. Thus it will be both
weaker and more ductile (bendable; the opposite of brittle) in
comparison to a cold forged part made from the same alloy. You can't
usually tell just by looking whether a forged part was cold- or hot-
forged.

The most common sort of stem I see on new bikes is forged from
aluminum around a mandrel (making the finished product hollow):

http://www.sheldonbrown.com/harris/images/stem-dimension-thless-sm4523.jpg

Most aluminum brake arms, seatpost heads, crank arms, pedal bodies,
and hub shells on decent quality bikes are also forged.

Casting allows the the same sorts of complex shapes as forging, with
even more detail and finer surface finish. (Castings can also be
incredibly crude and poorly finished.) Cast metals tend to be softer
and weaker than cold-forged metals, but much more brittle than hot-
forged metals. They also contain the largest flaws from which cracks
can propagate. Casting dies are very expensive, but the incremental
unit cost of cast parts is tiny compared to most other processes. As
a result, cast parts are common on cheap pedestrian bikes which are to
be sold in great numbers-- think Huffies and other bicycle-shaped
objects.

Machining is the term for cutting material away from a casting,
forging, or blank of raw metal. Any bike part with threads for screws
in it has been machined to some degree. Machining parts from plain
bar stock is one of the most economical ways to make small numbers of
a part, but one of the most expensive ways to mass-produce parts. It
produces a huge amount of swarf (chips) which must be recycled or
discarded.

Machining includes milling (which would be used to make a crank or
fancy chainring) and turning (which would be used to make a hub shell
or pedal spindle), as well as other processes like drilling, tapping
(making threads), broaching (making splines and keyways), flycutting,
and surface grinding. CNC stands for "computer numeric control",
meaning the machine runs under the command of a computer which has
been programmed with toolpaths by its operator. CNC machining allows
shapes and finish quality which were not feasible when the machines
were controlled exclusively by hand cranks and levers.

It's common these days for forgings to be machined on all exposed
surfaces. This accomplishes two primary things: It brings the part
to a very uniform shape and finish, and it makes the part shiny and
attractive to the consumer without the need for much more surface
treatment.

Stamping is another process that can be seen in some metal bike
parts. Stamping uses punches and dies to strike flat forms from metal
sheet or plate, sometimes bashing curved surfaces into the parts in
the same process or a subsequent step. Cheap steel single-pivot
calipers are probably the best-known stampings used in bikes, though
there are plenty of other examples. Seat guts are stamped, as are
some brake levers. Steel chainrings, sprockets, derailleurs, and hubs
are almost always stamped. Lots of steel stems are made by stamping
or a combination of stamping and welding. Pedal cages are stamped.

The benefit of stamping is entirely in its low manufacturing cost.
Parts made this way usually lack rigidity for their weight, owing to
their thin, flattened and mostly open sections.

Welding is used for some parts, like stems and a few cranks and
seatposts. Welding from sections of tube results in a naturally stiff
and efficient structure with all its mass close to the part surface,
where the material can best resist stresses. The drawbacks are
relatively high labor cost and significant variations in uniformity
and quality control. Almost all welded parts will need some amount of
machining before and after welding.

I may have left out some noteworthy processes, but at the moment I
think that's about all the common metalworking techniques used in the
manufacturing of bike parts.

Chalo

raamman@gmail.com

01-03-1970, 08:51 AM

On Jul 27, 3:39 pm, Sheldon Brown <CaptB...@sheldonbrown.com> wrote:
> Good cranks are always forged, but then there is CNC finishing work
> done on the forged blanks...threading, milling the spider lands, etc.
>
> Some Cranks have hollow construction, generally with a forged u-
> section outer part, and a flat section welded to the backside.
>
> Sheldon "Grain Matters" Brown
> +--------------------------------------------------------------+
> | Wherever there is sufficient space for a motor vehicle |
> | there must be sufficient space for a bicycle, |
> | because the bicycle is smaller. Is that not obviously so? |
> | -- John Forester |
> +--------------------------------------------------------------+
>
> Harris Cyclery, West Newton, Massachusetts
> Phone 617-244-9772 FAX 617-244-1041
> http://harriscyclery.com
> Hard-to-find parts shipped Worldwidehttp://captainbike.com http://sheldonbrown.com

any idea what size press (tonnage) they would use for cranks ?

jim beam

01-03-1970, 08:52 AM

raamman@gmail.com wrote:
> On Jul 27, 3:39 pm, Sheldon Brown <CaptB...@sheldonbrown.com> wrote:
>> Good cranks are always forged, but then there is CNC finishing work
>> done on the forged blanks...threading, milling the spider lands, etc.
>>
>> Some Cranks have hollow construction, generally with a forged u-
>> section outer part, and a flat section welded to the backside.
>>
>> Sheldon "Grain Matters" Brown
>> +--------------------------------------------------------------+
>> | Wherever there is sufficient space for a motor vehicle |
>> | there must be sufficient space for a bicycle, |
>> | because the bicycle is smaller. Is that not obviously so? |
>> | -- John Forester |
>> +--------------------------------------------------------------+
>>
>> Harris Cyclery, West Newton, Massachusetts
>> Phone 617-244-9772 FAX 617-244-1041
>> http://harriscyclery.com
>> Hard-to-find parts shipped Worldwidehttp://captainbike.com http://sheldonbrown.com
>
> any idea what size press (tonnage) they would use for cranks ?
>

probably more than 1, less than 10. depends [among other things] on the
temperature, size, and degree of forming sought on each strike. most
producers suck it to see.

Chalo

01-03-1970, 08:55 AM

jim beam wrote:
>
> you seem to be confused about how cnc is different from casting or
> forging. cnc is simply a machining process that's used for finishing,
> not for basic form creation like casting or forging.

That's not exactly true. The CNC machined parts that brought this
technique into the bike world were all machined from billet, and many
still are. Paul Components, White Industries, Ringlé, Avid, Grafton,
IRD, Kooka, Cook Bros, and others machined parts from plain bar
stock.

The reasons that many of them no longer do so has as much to do with
cost of production as it does with the superiority of forgings. Many
of the aforementioned manufacturers used 7075-T6 alloy, for example,
which is much stronger than the aluminum alloys used in the vast
majority of forged parts.

Chalo

Johnny Sunset aka Tom Sherman

01-03-1970, 08:55 AM

"jim beam" who? wrote:
> ...most producers suck it to see.

Huh?

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

datakoll

01-03-1970, 08:55 AM

the road bike frame i ride is 20 years old. Slowly over time and
replacement, all parts were upgraded to contemporary Shimano Deore and
now resin MTB grips.
I accumulated and used three salvedged sets of 20 year old SunTour and
generic Tiwanese parts sharing a common end-the parts cracked.
The contemporary Deore parts show no signs of cracking or metal
fatigue but slowly, progressively wear out.
Is that difference alloy or forged vs cast?

jim beam

01-03-1970, 08:55 AM

Chalo wrote:
> bicycle_disciple wrote:
>> What manufacturing methods are being used in high end components these
>> days and how do each one affect strength, failure due to fatigue,
>> stiffness etc?
>
> There are more factors than manufacturing method that dictate the
> properties of a part.
>
> Know first of all that stiffness is a product of basic material type
> and part dimensions, not manufacturing technique. A cast stem made
> from weak, soft aluminum would be as stiff as a cold-forged and
> machined stem made from 7075-T6 alloy, if they both had the same
> shape, size, and weight. So for stiffness, you are concerned about
> gross categories of material (e.g. steel vs. titanium vs. aluminum vs.
> magnesium), part weight, and part form. It makes no difference how
> the part is made.
>
> For the purposes of the discussion, I am going to exclude frames,
> forks, rims, etc-- things that can be considered structures unto
> themselves. Such parts have more in common with each other than they
> do with components that function as mechanisms.
>
> The highest quality components these days are either cold forged from
> metal or laid up and cured from carbon/epoxy. (I'm not going to talk
> about carbon parts because I think they're goofy.) Forging is
> basically smashing material into the desired shape between tools or
> forms made of harder stuff. It makes the metal stronger and reduces
> the size and effect of internal flaws, as well as being a material-
> efficient way of making parts. The tradeoff is that the dies (shaped
> tools) for forging are very expensive, and the finish quality of parts
> in as-forged condition can be pretty crude.
>
> Forging can be done on "cold" metal (in the same microcrystalline
> state as at room temperature), which causes work hardening--
> strengthening-- of the metal itself. It can also be done hot, with
> metal that is softened and easier to smash into shape. Hot forged
> parts have the structural advantages of "grain" that follows the shape
> of the part and diminished internal flaws, but the metal will be in a
> relatively soft state after the part cools. Thus it will be both
> weaker and more ductile (bendable; the opposite of brittle) in
> comparison to a cold forged part made from the same alloy. You can't
> usually tell just by looking whether a forged part was cold- or hot-
> forged.
>
> The most common sort of stem I see on new bikes is forged from
> aluminum around a mandrel (making the finished product hollow):
>
> http://www.sheldonbrown.com/harris/images/stem-dimension-thless-sm4523.jpg
>
> Most aluminum brake arms, seatpost heads, crank arms,

it seems a good amount of low end stuff these days is cast
[thixoformed], including crank arms.

> pedal bodies,
> and hub shells on decent quality bikes are also forged.
>
> Casting allows the the same sorts of complex shapes as forging, with
> even more detail and finer surface finish. (Castings can also be
> incredibly crude and poorly finished.) Cast metals tend to be softer
> and weaker than cold-forged metals, but much more brittle than hot-
> forged metals. They also contain the largest flaws from which cracks
> can propagate. Casting dies are very expensive, but the incremental
> unit cost of cast parts is tiny compared to most other processes. As
> a result, cast parts are common on cheap pedestrian bikes which are to
> be sold in great numbers-- think Huffies and other bicycle-shaped
> objects.
>
> Machining is the term for cutting material away from a casting,
> forging, or blank of raw metal. Any bike part with threads for screws
> in it has been machined to some degree. Machining parts from plain
> bar stock is one of the most economical ways to make small numbers of
> a part, but one of the most expensive ways to mass-produce parts. It
> produces a huge amount of swarf (chips) which must be recycled or
> discarded.
>
> Machining includes milling (which would be used to make a crank or
> fancy chainring) and turning (which would be used to make a hub shell
> or pedal spindle), as well as other processes like drilling, tapping
> (making threads), broaching (making splines and keyways), flycutting,
> and surface grinding. CNC stands for "computer numeric control",
> meaning the machine runs under the command of a computer which has
> been programmed with toolpaths by its operator. CNC machining allows
> shapes and finish quality which were not feasible when the machines
> were controlled exclusively by hand cranks and levers.
>
> It's common these days for forgings to be machined on all exposed
> surfaces. This accomplishes two primary things: It brings the part
> to a very uniform shape and finish, and it makes the part shiny and
> attractive to the consumer without the need for much more surface
> treatment.

surface finish is also a primary consideration in fatigue initiation.
"shiny" has significant fatigue benefits, not just consumer attraction.

>
> Stamping is another process that can be seen in some metal bike
> parts. Stamping uses punches and dies to strike flat forms from metal
> sheet or plate, sometimes bashing curved surfaces into the parts in
> the same process or a subsequent step. Cheap steel single-pivot
> calipers are probably the best-known stampings used in bikes, though
> there are plenty of other examples. Seat guts are stamped, as are
> some brake levers. Steel chainrings, sprockets, derailleurs, and hubs
> are almost always stamped. Lots of steel stems are made by stamping
> or a combination of stamping and welding. Pedal cages are stamped.

stamping imparts additional cold work, which in turn can increase
strength - it's not all bad. especially in applications like sprockets.

>
> The benefit of stamping is entirely in its low manufacturing cost.
> Parts made this way usually lack rigidity for their weight, owing to
> their thin, flattened and mostly open sections.

there are additional benefits though - see above.

>
> Welding is used for some parts, like stems and a few cranks and
> seatposts. Welding from sections of tube results in a naturally stiff
> and efficient structure with all its mass close to the part surface,
> where the material can best resist stresses. The drawbacks are
> relatively high labor cost and significant variations in uniformity
> and quality control. Almost all welded parts will need some amount of
> machining before and after welding.

it's also harder to make a welded part behave well in fatigue.

>
> I may have left out some noteworthy processes, but at the moment I
> think that's about all the common metalworking techniques used in the
> manufacturing of bike parts.

not bad... but you could write theses on this stuff if you want to be
pedantic.

Johnny Sunset aka Tom Sherman

01-03-1970, 08:55 AM

Chalo Colina wrote:
> ...
> I may have left out some noteworthy processes, but at the moment I
> think that's about all the common metalworking techniques used in the
> manufacturing of bike parts.

Chalo neglects to mention the drinking of beer [1] by the machinist
after the work is done.

[1] The skill of the machinist can be correlated to the quality of the
beer.

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

Johnny Sunset aka Tom Sherman

01-03-1970, 08:55 AM

Nate Knutson

01-03-1970, 08:55 AM

On Jul 27, 6:15 pm, Chalo <chalo.col...@gmail.com> wrote:

> I may have left out some noteworthy processes, but at the moment I
> think that's about all the common metalworking techniques used in the
> manufacturing of bike parts.
>
> Chalo

Chalo,

Thanks contributing this! Bravo!

Lou Holtman

01-03-1970, 08:55 AM

Chalo wrote:
> bicycle_disciple wrote:
>> What manufacturing methods are being used in high end components these
>> days and how do each one affect strength, failure due to fatigue,
>> stiffness etc?
>
> There are more factors than manufacturing method that dictate the
> properties of a part.
>
> Know first of all that stiffness is a product of basic material type
> and part dimensions, not manufacturing technique. A cast stem made
> from weak, soft aluminum would be as stiff as a cold-forged and
> machined stem made from 7075-T6 alloy, if they both had the same
> shape, size, and weight. So for stiffness, you are concerned about
> gross categories of material (e.g. steel vs. titanium vs. aluminum vs.
> magnesium), part weight, and part form. It makes no difference how
> the part is made.
>
> For the purposes of the discussion, I am going to exclude frames,
> forks, rims, etc-- things that can be considered structures unto
> themselves. Such parts have more in common with each other than they
> do with components that function as mechanisms.
>
> The highest quality components these days are either cold forged from
> metal or laid up and cured from carbon/epoxy. (I'm not going to talk
> about carbon parts because I think they're goofy.) Forging is
> basically smashing material into the desired shape between tools or
> forms made of harder stuff. It makes the metal stronger and reduces
> the size and effect of internal flaws, as well as being a material-
> efficient way of making parts. The tradeoff is that the dies (shaped
> tools) for forging are very expensive, and the finish quality of parts
> in as-forged condition can be pretty crude.
>
> Forging can be done on "cold" metal (in the same microcrystalline
> state as at room temperature), which causes work hardening--
> strengthening-- of the metal itself. It can also be done hot, with
> metal that is softened and easier to smash into shape. Hot forged
> parts have the structural advantages of "grain" that follows the shape
> of the part and diminished internal flaws, but the metal will be in a
> relatively soft state after the part cools. Thus it will be both
> weaker and more ductile (bendable; the opposite of brittle) in
> comparison to a cold forged part made from the same alloy. You can't
> usually tell just by looking whether a forged part was cold- or hot-
> forged.
>
> The most common sort of stem I see on new bikes is forged from
> aluminum around a mandrel (making the finished product hollow):
>
> http://www.sheldonbrown.com/harris/images/stem-dimension-thless-sm4523.jpg
>
> Most aluminum brake arms, seatpost heads, crank arms, pedal bodies,
> and hub shells on decent quality bikes are also forged.
>
> Casting allows the the same sorts of complex shapes as forging, with
> even more detail and finer surface finish. (Castings can also be
> incredibly crude and poorly finished.) Cast metals tend to be softer
> and weaker than cold-forged metals, but much more brittle than hot-
> forged metals. They also contain the largest flaws from which cracks
> can propagate. Casting dies are very expensive, but the incremental
> unit cost of cast parts is tiny compared to most other processes. As
> a result, cast parts are common on cheap pedestrian bikes which are to
> be sold in great numbers-- think Huffies and other bicycle-shaped
> objects.
>
> Machining is the term for cutting material away from a casting,
> forging, or blank of raw metal. Any bike part with threads for screws
> in it has been machined to some degree. Machining parts from plain
> bar stock is one of the most economical ways to make small numbers of
> a part, but one of the most expensive ways to mass-produce parts. It
> produces a huge amount of swarf (chips) which must be recycled or
> discarded.
>
> Machining includes milling (which would be used to make a crank or
> fancy chainring) and turning (which would be used to make a hub shell
> or pedal spindle), as well as other processes like drilling, tapping
> (making threads), broaching (making splines and keyways), flycutting,
> and surface grinding. CNC stands for "computer numeric control",
> meaning the machine runs under the command of a computer which has
> been programmed with toolpaths by its operator. CNC machining allows
> shapes and finish quality which were not feasible when the machines
> were controlled exclusively by hand cranks and levers.
>
> It's common these days for forgings to be machined on all exposed
> surfaces. This accomplishes two primary things: It brings the part
> to a very uniform shape and finish, and it makes the part shiny and
> attractive to the consumer without the need for much more surface
> treatment.
>
> Stamping is another process that can be seen in some metal bike
> parts. Stamping uses punches and dies to strike flat forms from metal
> sheet or plate, sometimes bashing curved surfaces into the parts in
> the same process or a subsequent step. Cheap steel single-pivot
> calipers are probably the best-known stampings used in bikes, though
> there are plenty of other examples. Seat guts are stamped, as are
> some brake levers. Steel chainrings, sprockets, derailleurs, and hubs
> are almost always stamped. Lots of steel stems are made by stamping
> or a combination of stamping and welding. Pedal cages are stamped.
>
> The benefit of stamping is entirely in its low manufacturing cost.
> Parts made this way usually lack rigidity for their weight, owing to
> their thin, flattened and mostly open sections.
>
> Welding is used for some parts, like stems and a few cranks and
> seatposts. Welding from sections of tube results in a naturally stiff
> and efficient structure with all its mass close to the part surface,
> where the material can best resist stresses. The drawbacks are
> relatively high labor cost and significant variations in uniformity
> and quality control. Almost all welded parts will need some amount of
> machining before and after welding.
>
> I may have left out some noteworthy processes, but at the moment I
> think that's about all the common metalworking techniques used in the
> manufacturing of bike parts.
>
> Chalo
>
>

Excellent post! Thanks.

Lou
--
Posted by news://news.nb.nu (http://www.nb.nu)

RonSonic

01-03-1970, 08:55 AM

Please consider for the FAQ. Answers a lot of common questions well.

Well said.

Ron

On Sat, 28 Jul 2007 01:15:44 -0000, Chalo <chalo.colina@gmail.com> wrote:

>bicycle_disciple wrote:
>>
>> What manufacturing methods are being used in high end components these
>> days and how do each one affect strength, failure due to fatigue,
>> stiffness etc?
>
>There are more factors than manufacturing method that dictate the
>properties of a part.
>
>Know first of all that stiffness is a product of basic material type
>and part dimensions, not manufacturing technique. A cast stem made
>from weak, soft aluminum would be as stiff as a cold-forged and
>machined stem made from 7075-T6 alloy, if they both had the same
>shape, size, and weight. So for stiffness, you are concerned about
>gross categories of material (e.g. steel vs. titanium vs. aluminum vs.
>magnesium), part weight, and part form. It makes no difference how
>the part is made.
>
>For the purposes of the discussion, I am going to exclude frames,
>forks, rims, etc-- things that can be considered structures unto
>themselves. Such parts have more in common with each other than they
>do with components that function as mechanisms.
>
>The highest quality components these days are either cold forged from
>metal or laid up and cured from carbon/epoxy. (I'm not going to talk
>about carbon parts because I think they're goofy.) Forging is
>basically smashing material into the desired shape between tools or
>forms made of harder stuff. It makes the metal stronger and reduces
>the size and effect of internal flaws, as well as being a material-
>efficient way of making parts. The tradeoff is that the dies (shaped
>tools) for forging are very expensive, and the finish quality of parts
>in as-forged condition can be pretty crude.
>
>Forging can be done on "cold" metal (in the same microcrystalline
>state as at room temperature), which causes work hardening--
>strengthening-- of the metal itself. It can also be done hot, with
>metal that is softened and easier to smash into shape. Hot forged
>parts have the structural advantages of "grain" that follows the shape
>of the part and diminished internal flaws, but the metal will be in a
>relatively soft state after the part cools. Thus it will be both
>weaker and more ductile (bendable; the opposite of brittle) in
>comparison to a cold forged part made from the same alloy. You can't
>usually tell just by looking whether a forged part was cold- or hot-
>forged.
>
>The most common sort of stem I see on new bikes is forged from
>aluminum around a mandrel (making the finished product hollow):
>
>http://www.sheldonbrown.com/harris/images/stem-dimension-thless-sm4523.jpg
>
>Most aluminum brake arms, seatpost heads, crank arms, pedal bodies,
>and hub shells on decent quality bikes are also forged.
>
>Casting allows the the same sorts of complex shapes as forging, with
>even more detail and finer surface finish. (Castings can also be
>incredibly crude and poorly finished.) Cast metals tend to be softer
>and weaker than cold-forged metals, but much more brittle than hot-
>forged metals. They also contain the largest flaws from which cracks
>can propagate. Casting dies are very expensive, but the incremental
>unit cost of cast parts is tiny compared to most other processes. As
>a result, cast parts are common on cheap pedestrian bikes which are to
>be sold in great numbers-- think Huffies and other bicycle-shaped
>objects.
>
>Machining is the term for cutting material away from a casting,
>forging, or blank of raw metal. Any bike part with threads for screws
>in it has been machined to some degree. Machining parts from plain
>bar stock is one of the most economical ways to make small numbers of
>a part, but one of the most expensive ways to mass-produce parts. It
>produces a huge amount of swarf (chips) which must be recycled or
>discarded.
>
>Machining includes milling (which would be used to make a crank or
>fancy chainring) and turning (which would be used to make a hub shell
>or pedal spindle), as well as other processes like drilling, tapping
>(making threads), broaching (making splines and keyways), flycutting,
>and surface grinding. CNC stands for "computer numeric control",
>meaning the machine runs under the command of a computer which has
>been programmed with toolpaths by its operator. CNC machining allows
>shapes and finish quality which were not feasible when the machines
>were controlled exclusively by hand cranks and levers.
>
>It's common these days for forgings to be machined on all exposed
>surfaces. This accomplishes two primary things: It brings the part
>to a very uniform shape and finish, and it makes the part shiny and
>attractive to the consumer without the need for much more surface
>treatment.
>
>Stamping is another process that can be seen in some metal bike
>parts. Stamping uses punches and dies to strike flat forms from metal
>sheet or plate, sometimes bashing curved surfaces into the parts in
>the same process or a subsequent step. Cheap steel single-pivot
>calipers are probably the best-known stampings used in bikes, though
>there are plenty of other examples. Seat guts are stamped, as are
>some brake levers. Steel chainrings, sprockets, derailleurs, and hubs
>are almost always stamped. Lots of steel stems are made by stamping
>or a combination of stamping and welding. Pedal cages are stamped.
>
>The benefit of stamping is entirely in its low manufacturing cost.
>Parts made this way usually lack rigidity for their weight, owing to
>their thin, flattened and mostly open sections.
>
>Welding is used for some parts, like stems and a few cranks and
>seatposts. Welding from sections of tube results in a naturally stiff
>and efficient structure with all its mass close to the part surface,
>where the material can best resist stresses. The drawbacks are
>relatively high labor cost and significant variations in uniformity
>and quality control. Almost all welded parts will need some amount of
>machining before and after welding.
>
>I may have left out some noteworthy processes, but at the moment I
>think that's about all the common metalworking techniques used in the
>manufacturing of bike parts.
>
>Chalo
>

Michael Press

01-03-1970, 08:55 AM

In article
<1185585344.170983.242980@z28g2000prd.googlegroups. com>
,
Chalo <chalo.colina@gmail.com> wrote:
>
> There are more factors than manufacturing method that dictate the
> properties of a part.
>
> Know first of all that stiffness is a product of basic material type
> and part dimensions, not manufacturing technique. A cast stem made
> from weak, soft aluminum would be as stiff as a cold-forged and
> machined stem made from 7075-T6 alloy, if they both had the same
> shape, size, and weight. So for stiffness, you are concerned about
> gross categories of material (e.g. steel vs. titanium vs. aluminum vs.
> magnesium), part weight, and part form. It makes no difference how
> the part is made.

[...]

>
> I may have left out some noteworthy processes, but at the moment I
> think that's about all the common metalworking techniques used in the
> manufacturing of bike parts.

Thanks for this, Chalo.

--
Michael Press

jim beam

01-03-1970, 08:55 AM

Chalo wrote:
> jim beam wrote:
>> you seem to be confused about how cnc is different from casting or
>> forging. cnc is simply a machining process that's used for finishing,
>> not for basic form creation like casting or forging.
>
> That's not exactly true.

i know - i'm simplifying for the context of the op's question.

> The CNC machined parts that brought this
> technique into the bike world were all machined from billet, and many
> still are. Paul Components, White Industries, Ringlï¿½, Avid, Grafton,
> IRD, Kooka, Cook Bros, and others machined parts from plain bar
> stock.

right - because for a small production run, it's cheaper than setting up
a forge and /then/ machining. but quality product when machining from
billet requires material to be much more expensive than would otherwise
be necessary. and in volume, unit costs are much higher.

>
> The reasons that many of them no longer do so has as much to do with
> cost of production as it does with the superiority of forgings. Many
> of the aforementioned manufacturers used 7075-T6 alloy, for example,
> which is much stronger than the aluminum alloys used in the vast
> majority of forged parts.

indeed. see above.

Chalo

01-03-1970, 08:55 AM

On Jul 27, 8:47 pm, datakoll <datak...@yahoo.com> wrote:
> the road bike frame i ride is 20 years old. Slowly over time and
> replacement, all parts were upgraded to contemporary Shimano Deore and
> now resin MTB grips.
> I accumulated and used three salvedged sets of 20 year old SunTour and
> generic Tiwanese parts sharing a common end-the parts cracked.
> The contemporary Deore parts show no signs of cracking or metal
> fatigue but slowly, progressively wear out.
> Is that difference alloy or forged vs cast?

It probably has more to do with designs arising out of stress
simulation and analysis than anything. I don't know whether new Deore
parts are hot forged or cast, but they are shaped quite a bit
differently than the 20-year-old state of the art. I really doubt
that Shimano uses better materials that Suntour did in days of yore.
Taiwanese parts of those days were pretty junky, though, and
metallurgy may have played a part in their eventual failures.

Chalo

jim beam

01-03-1970, 08:55 AM

datakoll wrote:
> the road bike frame i ride is 20 years old. Slowly over time and
> replacement, all parts were upgraded to contemporary Shimano Deore and
> now resin MTB grips.
> I accumulated and used three salvedged sets of 20 year old SunTour and
> generic Tiwanese parts sharing a common end-the parts cracked.
> The contemporary Deore parts show no signs of cracking or metal
> fatigue but slowly, progressively wear out.
> Is that difference alloy or forged vs cast?
>
it can be, yes. from my experience, a lot of cast bike parts are softer
and less wear resistant. certainly less fatigue resistant.

01-03-1970, 08:55 AM

"datakoll" <datakoll@yahoo.com> wrote in message
news:1185587275.466992.284760@d55g2000hsg.googlegr oups.com...
> the road bike frame i ride is 20 years old. Slowly over time and
> replacement, all parts were upgraded to contemporary Shimano Deore and
> now resin MTB grips.
> I accumulated and used three salvedged sets of 20 year old SunTour and
> generic Tiwanese parts sharing a common end-the parts cracked.
> The contemporary Deore parts show no signs of cracking or metal
> fatigue but slowly, progressively wear out.
> Is that difference alloy or forged vs cast?

Alloy means the base metal has other elements mixed with it to alter it's
properties.

Forging is a manufacturing method where a metal is hammered into a base
shape. This produces one of the strongest shapes possible because the
metal's grain is lined up in a common direction. Think of a piece of wood
that comes directly from a tree, all the grain of the wood runs parallel to
the growth of the tree.

Casting is simply molted metal poured into a mold and allowed to cool,
compare it with particle board in wood.

I haven't thought much about it but would think a lot of bicycle parts
especially derailler and shifter components all start life as "investment
castings". This is where they have a mold and cast a wax part, the wax
part is coated with a ceramic type material and furnaced, hardening the
ceramic and melting the wax (hence the name "lost wax" casting. Molten
metal is poured in the ceramic mold which is broken away after the metal
cools. This produces a very accurate part with close tolerances and a
surface finish much like plastic. It's also possible to cast metals like
aluminum, stainless steel, and titanium.

raamman@gmail.com

01-03-1970, 08:56 AM

On Jul 27, 10:01 pm, jim beam <spamvor...@bad.example.net> wrote:
> Chalo wrote:
> > jim beam wrote:
> >> you seem to be confused about how cnc is different from casting or
> >> forging. cnc is simply a machining process that's used for finishing,
> >> not for basic form creation like casting or forging.
>
> > That's not exactly true.
>
> i know - i'm simplifying for the context of the op's question.
>
> > The CNC machined parts that brought this
> > technique into the bike world were all machined from billet, and many
> > still are. Paul Components, White Industries, Ringl?, Avid, Grafton,
> > IRD, Kooka, Cook Bros, and others machined parts from plain bar
> > stock.
>
> right - because for a small production run, it's cheaper than setting up
> a forge and /then/ machining. but quality product when machining from
> billet requires material to be much more expensive than would otherwise
> be necessary. and in volume, unit costs are much higher.
>
>
>
> > The reasons that many of them no longer do so has as much to do with
> > cost of production as it does with the superiority of forgings. Many
> > of the aforementioned manufacturers used 7075-T6 alloy, for example,
> > which is much stronger than the aluminum alloys used in the vast
> > majority of forged parts.
>
> indeed. see above.

Not quite; you can buy a cnc for $50G; with that you can make all the
fancy parts you want, starting in your garage; the forging requires
designing and building the dies, and you are already at the cost of a
cnc; then when you start to go into production your dies get smashed
and need to be fixed etc. and you are at least twice the cost of a cnc
to prototype your forged parts. it's economics.

Chalo

01-03-1970, 08:56 AM

jim beam wrote:
>
> Chalo wrote:
> >
> > The most common sort of stem I see on new bikes is forged from
> > aluminum around a mandrel (making the finished product hollow):
>
> >http://www.sheldonbrown.com/harris/images/stem-dimension-thless-sm452...
>
> > Most aluminum brake arms, seatpost heads, crank arms,
>
> it seems a good amount of low end stuff these days is cast
> [thixoformed], including crank arms.

I guess it would be fair to characterize thixoforming as "cold
casting", analogous to cold forging in its subtle but significant
advantages over "hot casting".

> > It's common these days for forgings to be machined on all exposed
> > surfaces. This accomplishes two primary things: It brings the part
> > to a very uniform shape and finish, and it makes the part shiny and
> > attractive to the consumer without the need for much more surface
> > treatment.
>
> surface finish is also a primary consideration in fatigue initiation.
> "shiny" has significant fatigue benefits, not just consumer attraction.

I'd say that "uniform shape and finish" is what gives good fatigue
resistance. Parts produced by other means (HIP casting for example)
can have a smooth finish that resists cracking but possesses no luster
to speak of. The asperities in an attractive shiny machined surface
can be aligned unfavorably and notched deeply enough to cause problems
in some cases.

> stamping imparts additional cold work, which in turn can increase
> strength - it's not all bad. especially in applications like sprockets.

That's a good example of where the localized perimeter "forging"
effected by stamping does some good. Mostly, stampings have to be
designed to deliver adequate stiffness, which naturally makes them
both heavier and stronger than would otherwise be necessary.

Chalo

jim beam

01-03-1970, 08:56 AM

Johnny Sunset aka Tom Sherman wrote:
> "jim beam" who? wrote:
>> ...most producers suck it to see.
>
> Huh?
>

"suck it and see" is a common expression hereabouts. but maybe that's
because i live in san francisco.

raamman@gmail.com

01-03-1970, 08:56 AM

On Jul 27, 10:33 pm, Johnny Sunset aka Tom Sherman
<sunsetss0...@yahoo.com> wrote:
> Chalo Colina wrote:
> > ...
> > I may have left out some noteworthy processes, but at the moment I
> > think that's about all the common metalworking techniques used in the
> > manufacturing of bike parts.
>
> Chalo neglects to mention the drinking of beer [1] by the machinist
> after the work is done.
>
> [1] The skill of the machinist can be correlated to the quality of the
> beer.
>
> --
> Tom Sherman - Holstein-Friesland Bovinia
> The weather is here, wish you were beautiful

or the dope smoked while it is done

Ozark Bicycle

01-03-1970, 08:56 AM

On Jul 27, 9:37 pm, jim beam <spamvor...@bad.example.net> wrote:
> Johnny Sunset aka Tom Sherman wrote:
>
> > "jim beam" who? wrote:
> >> ...most producers suck it to see.
>
> > Huh?
>
> "suck it and see" is a common expression hereabouts. but maybe that's
> because i live in san francisco.

AFAICT, it's origin is the UK. I first encountered the phrase in a
book about engine carburation, where "suck it and see" was (literally)
the only way to test new carb jetting.

Johnny Sunset aka Tom Sherman

01-03-1970, 08:56 AM

Ozark Bicycle wrote:
jim beam wrote:
>
> > Johnny Sunset aka Tom Sherman wrote:
>
> > > "jim beam" who? wrote:
> > >> ...most producers suck it to see.
>
> > > Huh?
>
> > "suck it and see" is a common expression hereabouts. but maybe that's
> > because i live in san francisco.
>
> AFAICT, it's origin is the UK. I first encountered the phrase in a
> book about engine carburation, where "suck it and see" was (literally)
> the only way to test new carb jetting.

And the S.U. carburetor gave way to Lucas fuel infection (sic)...

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

jim beam

01-03-1970, 08:56 AM

raamman@gmail.com wrote:
> On Jul 27, 10:01 pm, jim beam <spamvor...@bad.example.net> wrote:
>> Chalo wrote:
>>> jim beam wrote:
>>>> you seem to be confused about how cnc is different from casting or
>>>> forging. cnc is simply a machining process that's used for finishing,
>>>> not for basic form creation like casting or forging.
>>> That's not exactly true.
>> i know - i'm simplifying for the context of the op's question.
>>
>>> The CNC machined parts that brought this
>>> technique into the bike world were all machined from billet, and many
>>> still are. Paul Components, White Industries, Ringl?, Avid, Grafton,
>>> IRD, Kooka, Cook Bros, and others machined parts from plain bar
>>> stock.
>> right - because for a small production run, it's cheaper than setting up
>> a forge and /then/ machining. but quality product when machining from
>> billet requires material to be much more expensive than would otherwise
>> be necessary. and in volume, unit costs are much higher.
>>
>>
>>
>>> The reasons that many of them no longer do so has as much to do with
>>> cost of production as it does with the superiority of forgings. Many
>>> of the aforementioned manufacturers used 7075-T6 alloy, for example,
>>> which is much stronger than the aluminum alloys used in the vast
>>> majority of forged parts.
>> indeed. see above.
>
> Not quite; you can buy a cnc for $50G; with that you can make all the
> fancy parts you want, starting in your garage; the forging requires
> designing and building the dies, and you are already at the cost of a
> cnc; then when you start to go into production your dies get smashed
> and need to be fixed etc. and you are at least twice the cost of a cnc
> to prototype your forged parts. it's economics.
>

not sure i understand how this is different from what i was saying.
except that an experienced forge shop won't "smash" dies. they wear and
need to be replaced in the course of normal operations, but that's way
cheaper than the tooling replacement necessary for cnc given the
production volumes.

jim beam

01-03-1970, 08:57 AM

Chalo wrote:
> jim beam wrote:
>> Chalo wrote:
>>> The most common sort of stem I see on new bikes is forged from
>>> aluminum around a mandrel (making the finished product hollow):
>>> http://www.sheldonbrown.com/harris/images/stem-dimension-thless-sm452...
>>> Most aluminum brake arms, seatpost heads, crank arms,
>> it seems a good amount of low end stuff these days is cast
>> [thixoformed], including crank arms.
>
> I guess it would be fair to characterize thixoforming as "cold
> casting", analogous to cold forging in its subtle but significant
> advantages over "hot casting".

indeed - the majority is solid when formed. it's just like a slurpee -
lots of solid particles with a little liquid in between them.

>
>>> It's common these days for forgings to be machined on all exposed
>>> surfaces. This accomplishes two primary things: It brings the part
>>> to a very uniform shape and finish, and it makes the part shiny and
>>> attractive to the consumer without the need for much more surface
>>> treatment.
>> surface finish is also a primary consideration in fatigue initiation.
>> "shiny" has significant fatigue benefits, not just consumer attraction.
>
> I'd say that "uniform shape and finish" is what gives good fatigue
> resistance. Parts produced by other means (HIP casting for example)
> can have a smooth finish that resists cracking but possesses no luster
> to speak of.

right, but much superior microstructure - which is a big deal.

> The asperities in an attractive shiny machined surface
> can be aligned unfavorably and notched deeply enough to cause problems
> in some cases.

with inferior microstructure, yes. but if you have superior
microstructure /and/ a superior finish, you have much superior fatigue
performance.
http://www.flickr.com/photos/38636024@N00/340348242/

>
>> stamping imparts additional cold work, which in turn can increase
>> strength - it's not all bad. especially in applications like sprockets.
>
> That's a good example of where the localized perimeter "forging"
> effected by stamping does some good.

it's not forging, it's simply localized cold work from the shearing process.

> Mostly, stampings have to be
> designed to deliver adequate stiffness, which naturally makes them
> both heavier and stronger than would otherwise be necessary.

that's not true! stampings can capitalize on the material having been
extensively cold worked previously and therefore be lighter and stronger
than other fabrication routes. nervex lugs vs. investment cast lugs for
example. if additional stiffness is required, simple features like
corrugations help considerably with almost zero weight penalty. design
and material should /always/ go hand in hand from inception. material
should /never/ follow after design - a point seemingly absent from the
the majority of engineering syllabuses.

Tommy

01-03-1970, 08:59 AM

On Jul 28, 4:32 pm, jim beam <spamvor...@bad.example.net> wrote:
> Chalo wrote:
> > jim beam wrote:
> >> Chalo wrote:
> >>> The most common sort of stem I see on new bikes is forged from
> >>> aluminum around a mandrel (making the finished product hollow):
> >>>http://www.sheldonbrown.com/harris/images/stem-dimension-thless-sm452....
> >>> Most aluminum brake arms, seatpost heads, crank arms,
> >> it seems a good amount of low end stuff these days is cast
> >> [thixoformed], including crank arms.
>
> > I guess it would be fair to characterize thixoforming as "cold
> > casting", analogous to cold forging in its subtle but significant
> > advantages over "hot casting".
>
> indeed - the majority is solid when formed. it's just like a slurpee -
> lots of solid particles with a little liquid in between them.
>
>
>
> >>> It's common these days for forgings to be machined on all exposed
> >>> surfaces. This accomplishes two primary things: It brings the part
> >>> to a very uniform shape and finish, and it makes the part shiny and
> >>> attractive to the consumer without the need for much more surface
> >>> treatment.
> >> surface finish is also a primary consideration in fatigue initiation.
> >> "shiny" has significant fatigue benefits, not just consumer attraction.
>
> > I'd say that "uniform shape and finish" is what gives good fatigue
> > resistance. Parts produced by other means (HIP casting for example)
> > can have a smooth finish that resists cracking but possesses no luster
> > to speak of.
>
> right, but much superior microstructure - which is a big deal.
>
> > The asperities in an attractive shiny machined surface
> > can be aligned unfavorably and notched deeply enough to cause problems
> > in some cases.
>
> with inferior microstructure, yes. but if you have superior
> microstructure /and/ a superior finish, you have much superior fatigue
> performance.http://www.flickr.com/photos/38636024@N00/340348242/
>
>
>
> >> stamping imparts additional cold work, which in turn can increase
> >> strength - it's not all bad. especially in applications like sprockets.
>
> > That's a good example of where the localized perimeter "forging"
> > effected by stamping does some good.
>
> it's not forging, it's simply localized cold work from the shearing process.
>
> > Mostly, stampings have to be
> > designed to deliver adequate stiffness, which naturally makes them
> > both heavier and stronger than would otherwise be necessary.
>
> that's not true! stampings can capitalize on the material having been
> extensively cold worked previously and therefore be lighter and stronger
> than other fabrication routes. nervex lugs vs. investment cast lugs for
> example. if additional stiffness is required, simple features like
> corrugations help considerably with almost zero weight penalty. design
> and material should /always/ go hand in hand from inception. material
> should /never/ follow after design - a point seemingly absent from the
> the majority of engineering syllabuses.

Plastic forming, as used on the most advanced airframes,
is the way the ultimate components could be made.
It is usually in titanium.
Pro teams could use them, like formula 1, do.
Say they made a chainset £25K each for a batch of 30 i.e. for one team
it would give an advantage.
However, because the component manufacturers' wish to sell similar
parts to those of us keen enough to pay a grand for a group set, they
could not justify the initial development cost, say £0.5M.
They want to sell thousands of sets on the open market like it does
for Shimano when they release a new chainset for £250.

Has any one used plastic Forming on a component yet?
They look fantastic as the shape is not constrained by die strength.
A frame would be a dream. With aero dynamics to die for and so rigid.

I find the dialogue on Components fascinating but would add one spoke.

Heat treatment is a fundamental issue when manufacturing components in
Light Alloys.
Unfortunately it is the most difficult process to control.

For instance High spec Alloy is normally
A) 'solutionised' prior to machining from the billet.
If this is not done then the material can become stressed and weakened
by the heat and stress of machining.

B) After M/c'ing it will then be precipitated at a lower temp for say
5 Hrs.
If this is not done the material ages slowly and without going too
deep in to the metallurgy- it develops a course crystalline structure
which will be brittle and prone to fatigue.

I have worked on aircraft inspection and detected items had not been
treated even with "fool proof quality checks" .
( It was a quality check post production and is done by using a test
process involving pushing a diamond point into the metal and measuring
how deep it goes in.)

We detected the final heat treatment had been missed. As the part had
ben machined only a couple of days earlier the heat treatment could be
still be done even though the item was painted. However if the pre-
machining solutionising had been missed out and the final
precipitation had been we would not have detected it and the component
would have been ...... fitted.
Has any one had a cheap Italian head stem fail and looked at
the very course grainy surface on the fracture.
It can be more likely when the components' cold.

After all that - the bottom line is..... how good to you think the
quality control is in a bike component factory. A further point is the
scrap rate on carbon fibre used to be massive in the early days in
aerospace.
cheers

You know hes a cyclist if he has a kitchen full of drink bottles.
and
Smoother legs than his wife

Chalo

01-03-1970, 08:59 AM

On Jul 28, 10:32 am, jim beam <spamvor...@bad.example.net> wrote:
> Chalo wrote:
> > jim beam wrote:
> >> Chalo wrote:
> >>> The most common sort of stem I see on new bikes is forged from
> >>> aluminum around a mandrel (making the finished product hollow):
> >>>http://www.sheldonbrown.com/harris/images/stem-dimension-thless-sm452...
> >>> Most aluminum brake arms, seatpost heads, crank arms,
> >> it seems a good amount of low end stuff these days is cast
> >> [thixoformed], including crank arms.
>
> > I guess it would be fair to characterize thixoforming as "cold
> > casting", analogous to cold forging in its subtle but significant
> > advantages over "hot casting".
>
> indeed - the majority is solid when formed. it's just like a slurpee -
> lots of solid particles with a little liquid in between them.
>
>
>
> >>> It's common these days for forgings to be machined on all exposed
> >>> surfaces. This accomplishes two primary things: It brings the part
> >>> to a very uniform shape and finish, and it makes the part shiny and
> >>> attractive to the consumer without the need for much more surface
> >>> treatment.
> >> surface finish is also a primary consideration in fatigue initiation.
> >> "shiny" has significant fatigue benefits, not just consumer attraction.
>
> > I'd say that "uniform shape and finish" is what gives good fatigue
> > resistance. Parts produced by other means (HIP casting for example)
> > can have a smooth finish that resists cracking but possesses no luster
> > to speak of.
>
> right, but much superior microstructure - which is a big deal.
>
> > The asperities in an attractive shiny machined surface
> > can be aligned unfavorably and notched deeply enough to cause problems
> > in some cases.
>
> with inferior microstructure, yes. but if you have superior
> microstructure /and/ a superior finish, you have much superior fatigue
> performance.http://www.flickr.com/photos/38636024@N00/340348242/
>
>
>
> >> stamping imparts additional cold work, which in turn can increase
> >> strength - it's not all bad. especially in applications like sprockets.
>
> > That's a good example of where the localized perimeter "forging"
> > effected by stamping does some good.
>
> it's not forging, it's simply localized cold work from the shearing process.

Sprocket teeth get a bit more work than just shearing. They have
their tips tapered at least.

> > Mostly, stampings have to be
> > designed to deliver adequate stiffness, which naturally makes them
> > both heavier and stronger than would otherwise be necessary.
>
> that's not true! stampings can capitalize on the material having been
> extensively cold worked previously and therefore be lighter and stronger
> than other fabrication routes. nervex lugs vs. investment cast lugs for
> example. if additional stiffness is required, simple features like
> corrugations help considerably with almost zero weight penalty.

Using the typical example of a stamped steel brake caliper, there is
not much in the way of corrugation that would impart enough stiffness
to make the caliper weight-competitive with a forged aluminum one.
The driving factor in both cases is bending and torsional stiffness,
and stamping the caliper arms into a "C" cross-section does not really
address the torsional part (nor can the pivot maintain a curved
section). Thus the stamped caliper must be made heavier than the
forged one for equal function.

> design
> and material should /always/ go hand in hand from inception. material
> should /never/ follow after design - a point seemingly absent from the
> the majority of engineering syllabuses.

True. But materials choices seem to come first all too often as
"sexy" but gratuitous materials become the basis for marketing
schemes. Carbon-thermoplastic anyone? How about metal matrix
composite? Scandium alloy!

Chalo

Chalo

01-03-1970, 08:59 AM

raam...@gmail.com wrote:
>
> Tom Sherman wrote:
> >
> > Chalo Colina wrote:
> > > ...
> > > I may have left out some noteworthy processes, but at the moment I
> > > think that's about all the common metalworking techniques used in the
> > > manufacturing of bike parts.
>
> > Chalo neglects to mention the drinking of beer [1] by the machinist
> > after the work is done.
>
> > [1] The skill of the machinist can be correlated to the quality of the
> > beer.
>
> or the dope smoked while it is done

I had a boss like that once. I couldn't imagine getting any work done
that way. Seemed to work for him, though.

Chalo

jim beam

01-03-1970, 09:00 AM

Chalo wrote:
> On Jul 28, 10:32 am, jim beam <spamvor...@bad.example.net> wrote:
>> Chalo wrote:
>>> jim beam wrote:
>>>> Chalo wrote:
>>>>> The most common sort of stem I see on new bikes is forged from
>>>>> aluminum around a mandrel (making the finished product hollow):
>>>>> http://www.sheldonbrown.com/harris/images/stem-dimension-thless-sm452...
>>>>> Most aluminum brake arms, seatpost heads, crank arms,
>>>> it seems a good amount of low end stuff these days is cast
>>>> [thixoformed], including crank arms.
>>> I guess it would be fair to characterize thixoforming as "cold
>>> casting", analogous to cold forging in its subtle but significant
>>> advantages over "hot casting".
>> indeed - the majority is solid when formed. it's just like a slurpee -
>> lots of solid particles with a little liquid in between them.
>>
>>
>>
>>>>> It's common these days for forgings to be machined on all exposed
>>>>> surfaces. This accomplishes two primary things: It brings the part
>>>>> to a very uniform shape and finish, and it makes the part shiny and
>>>>> attractive to the consumer without the need for much more surface
>>>>> treatment.
>>>> surface finish is also a primary consideration in fatigue initiation.
>>>> "shiny" has significant fatigue benefits, not just consumer attraction.
>>> I'd say that "uniform shape and finish" is what gives good fatigue
>>> resistance. Parts produced by other means (HIP casting for example)
>>> can have a smooth finish that resists cracking but possesses no luster
>>> to speak of.
>> right, but much superior microstructure - which is a big deal.
>>
>>> The asperities in an attractive shiny machined surface
>>> can be aligned unfavorably and notched deeply enough to cause problems
>>> in some cases.
>> with inferior microstructure, yes. but if you have superior
>> microstructure /and/ a superior finish, you have much superior fatigue
>> performance.http://www.flickr.com/photos/38636024@N00/340348242/
>>
>>
>>
>>>> stamping imparts additional cold work, which in turn can increase
>>>> strength - it's not all bad. especially in applications like sprockets.
>>> That's a good example of where the localized perimeter "forging"
>>> effected by stamping does some good.
>> it's not forging, it's simply localized cold work from the shearing process.
>
> Sprocket teeth get a bit more work than just shearing. They have
> their tips tapered at least.

but that doesn't do much for cold work...

>
>>> Mostly, stampings have to be
>>> designed to deliver adequate stiffness, which naturally makes them
>>> both heavier and stronger than would otherwise be necessary.
>> that's not true! stampings can capitalize on the material having been
>> extensively cold worked previously and therefore be lighter and stronger
>> than other fabrication routes. nervex lugs vs. investment cast lugs for
>> example. if additional stiffness is required, simple features like
>> corrugations help considerably with almost zero weight penalty.
>
> Using the typical example of a stamped steel brake caliper, there is
> not much in the way of corrugation that would impart enough stiffness
> to make the caliper weight-competitive with a forged aluminum one.

whoa! that's a whole different material class comparison.

> The driving factor in both cases is bending and torsional stiffness,
> and stamping the caliper arms into a "C" cross-section does not really
> address the torsional part (nor can the pivot maintain a curved
> section). Thus the stamped caliper must be made heavier than the
> forged one for equal function.

compare like with like. if you have stamped steel and cast steel of the
same dimensions for instance, the stamped will almost certainly be
better in that application. if you want to stray into differing
material classes, you need to discuss specific modulus, and some
aluminum alloys are better than steels in that regard.

>
>> design
>> and material should /always/ go hand in hand from inception. material
>> should /never/ follow after design - a point seemingly absent from the
>> the majority of engineering syllabuses.
>
> True. But materials choices seem to come first all too often as
> "sexy" but gratuitous materials become the basis for marketing
> schemes. Carbon-thermoplastic anyone? How about metal matrix
> composite? Scandium alloy!

agreed. particularly regarding "metal matrix composite" - doesn't even
have to be scandium. that b.s. phrase could mean /anything/ that's not
mono-phasic. simply ridiculous.

bicycle_disciple

01-03-1970, 09:02 AM

Thanks for all your replies. This kept bugging me, and now it
encourages me to read more on manufacturing technologies. This
discussion was productive though.

Ron
http://cozybeehive.blogspot.com

On Jul 28, 8:36 pm, RonSonic <ronso...@tampabay.rr.com> wrote:
> Please consider for the FAQ. Answers a lot of common questions well.
>
> Well said.
>
> Ron
>
> On Sat, 28 Jul 2007 01:15:44 -0000, Chalo <chalo.col...@gmail.com> wrote:
> >bicycle_disciple wrote:
>
> >> What manufacturing methods are being used in high end components these
> >> days and how do each one affect strength, failure due to fatigue,
> >> stiffness etc?
>
> >There are more factors than manufacturing method that dictate the
> >properties of a part.
>
> >Know first of all that stiffness is a product of basic material type
> >and part dimensions, not manufacturing technique. A cast stem made
> >from weak, soft aluminum would be as stiff as a cold-forged and
> >machined stem made from 7075-T6 alloy, if they both had the same
> >shape, size, and weight. So for stiffness, you are concerned about
> >gross categories of material (e.g. steel vs. titanium vs. aluminum vs.
> >magnesium), part weight, and part form. It makes no difference how
> >the part is made.
>
> >For the purposes of the discussion, I am going to exclude frames,
> >forks, rims, etc-- things that can be considered structures unto
> >themselves. Such parts have more in common with each other than they
> >do with components that function as mechanisms.
>
> >The highest quality components these days are either cold forged from
> >metal or laid up and cured from carbon/epoxy. (I'm not going to talk
> >about carbon parts because I think they're goofy.) Forging is
> >basically smashing material into the desired shape between tools or
> >forms made of harder stuff. It makes the metal stronger and reduces
> >the size and effect of internal flaws, as well as being a material-
> >efficient way of making parts. The tradeoff is that the dies (shaped
> >tools) for forging are very expensive, and the finish quality of parts
> >in as-forged condition can be pretty crude.
>
> >Forging can be done on "cold" metal (in the same microcrystalline
> >state as at room temperature), which causes work hardening--
> >strengthening-- of the metal itself. It can also be done hot, with
> >metal that is softened and easier to smash into shape. Hot forged
> >parts have the structural advantages of "grain" that follows the shape
> >of the part and diminished internal flaws, but the metal will be in a
> >relatively soft state after the part cools. Thus it will be both
> >weaker and more ductile (bendable; the opposite of brittle) in
> >comparison to a cold forged part made from the same alloy. You can't
> >usually tell just by looking whether a forged part was cold- or hot-
> >forged.
>
> >The most common sort of stem I see on new bikes is forged from
> >aluminum around a mandrel (making the finished product hollow):
>
> >http://www.sheldonbrown.com/harris/images/stem-dimension-thless-sm452...
>
> >Most aluminum brake arms, seatpost heads, crank arms, pedal bodies,
> >and hub shells on decent quality bikes are also forged.
>
> >Casting allows the the same sorts of complex shapes as forging, with
> >even more detail and finer surface finish. (Castings can also be
> >incredibly crude and poorly finished.) Cast metals tend to be softer
> >and weaker than cold-forged metals, but much more brittle than hot-
> >forged metals. They also contain the largest flaws from which cracks
> >can propagate. Casting dies are very expensive, but the incremental
> >unit cost of cast parts is tiny compared to most other processes. As
> >a result, cast parts are common on cheap pedestrian bikes which are to
> >be sold in great numbers-- think Huffies and other bicycle-shaped
> >objects.
>
> >Machining is the term for cutting material away from a casting,
> >forging, or blank of raw metal. Any bike part with threads for screws
> >in it has been machined to some degree. Machining parts from plain
> >bar stock is one of the most economical ways to make small numbers of
> >a part, but one of the most expensive ways to mass-produce parts. It
> >produces a huge amount of swarf (chips) which must be recycled or
> >discarded.
>
> >Machining includes milling (which would be used to make a crank or
> >fancy chainring) and turning (which would be used to make a hub shell
> >or pedal spindle), as well as other processes like drilling, tapping
> >(making threads), broaching (making splines and keyways), flycutting,
> >and surface grinding. CNC stands for "computer numeric control",
> >meaning the machine runs under the command of a computer which has
> >been programmed with toolpaths by its operator. CNC machining allows
> >shapes and finish quality which were not feasible when the machines
> >were controlled exclusively by hand cranks and levers.
>
> >It's common these days for forgings to be machined on all exposed
> >surfaces. This accomplishes two primary things: It brings the part
> >to a very uniform shape and finish, and it makes the part shiny and
> >attractive to the consumer without the need for much more surface
> >treatment.
>
> >Stamping is another process that can be seen in some metal bike
> >parts. Stamping uses punches and dies to strike flat forms from metal
> >sheet or plate, sometimes bashing curved surfaces into the parts in
> >the same process or a subsequent step. Cheap steel single-pivot
> >calipers are probably the best-known stampings used in bikes, though
> >there are plenty of other examples. Seat guts are stamped, as are
> >some brake levers. Steel chainrings, sprockets, derailleurs, and hubs
> >are almost always stamped. Lots of steel stems are made by stamping
> >or a combination of stamping and welding. Pedal cages are stamped.
>
> >The benefit of stamping is entirely in its low manufacturing cost.
> >Parts made this way usually lack rigidity for their weight, owing to
> >their thin, flattened and mostly open sections.
>
> >Welding is used for some parts, like stems and a few cranks and
> >seatposts. Welding from sections of tube results in a naturally stiff
> >and efficient structure with all its mass close to the part surface,
> >where the material can best resist stresses. The drawbacks are
> >relatively high labor cost and significant variations in uniformity
> >and quality control. Almost all welded parts will need some amount of
> >machining before and after welding.
>
> >I may have left out some noteworthy processes, but at the moment I
> >think that's about all the common metalworking techniques used in the
> >manufacturing of bike parts.
>
> >Chalo

datakoll

01-03-1970, 09:02 AM

Gabbing at Sebring, I expressed some wonder at the durability of
contemporary chevy can-am cars now 5 liter not 7 or more as a complete
package, racing equipment kinda DIY not factory suggesting the level
of preperation was higher than 20 years before.
But Ti and steel metallurgy was the answer, that 20 years of
metallurgy progress improved the finishing rate by 100% or more.

raamman@gmail.com

01-03-1970, 09:02 AM

On Jul 28, 9:35 pm, bicycle_disciple <1.crazyboy.o...@gmail.com>
wrote:
> Thanks for all your replies. This kept bugging me, and now it
> encourages me to read more on manufacturing technologies. This
> discussion was productive though.
>
>

I was curious when i got into cycling, then some bike mags featured
cnc machining and I wound up taking a course and doing that for awhile
( big mistake though, I hate noise and love the outdoors, fresh air, a
challenge and freedom)

Chalo

01-03-1970, 09:03 AM

raam...@gmail.com wrote:
>
> I was curious when i got into cycling, then some bike mags featured
> cnc machining and I wound up taking a course and doing that for awhile
> ( big mistake though, I hate noise and love the outdoors, fresh air, a
> challenge and freedom)

I have to say, one of the downsides to CNC machining is that it limits
the inventive process to a small subset of the folks who participate
in the process. When a machinist took a blueprint and a piece of
metal and turned cranks with his own hands, the methods and steps were
largely left up to him. Now he's more likely to get a diskette with a
set of toolpaths on it, and nothing of significance is left to his
discretion.

I think this is one of the reasons why many CNC machine shops are
small owner-operated outfits. When a man participates every part of
the process from finding new customers to shipping finished product,
he can keep his mind stimulated. When he just takes toolpaths from
somebody else and runs machinery, it's pretty difficult to maintain
any enthusiasm for the work.

Chalo

jim beam

01-03-1970, 09:03 AM

Chalo wrote:
> raam...@gmail.com wrote:
>> I was curious when i got into cycling, then some bike mags featured
>> cnc machining and I wound up taking a course and doing that for awhile
>> ( big mistake though, I hate noise and love the outdoors, fresh air, a
>> challenge and freedom)
>
> I have to say, one of the downsides to CNC machining is that it limits
> the inventive process to a small subset of the folks who participate
> in the process. When a machinist took a blueprint and a piece of
> metal and turned cranks with his own hands, the methods and steps were
> largely left up to him. Now he's more likely to get a diskette with a
> set of toolpaths on it, and nothing of significance is left to his
> discretion.
>
> I think this is one of the reasons why many CNC machine shops are
> small owner-operated outfits. When a man participates every part of
> the process from finding new customers to shipping finished product,
> he can keep his mind stimulated. When he just takes toolpaths from
> somebody else and runs machinery, it's pretty difficult to maintain
> any enthusiasm for the work.

very true. and added to that, without experienced machinist/shop work
input, serious design mistakes can be made. just like modern engineers
seem to have lost any ability to design to their material, they seem to
have no /clue/ about production process - and cnc production is the
/prime/ culprit responsible. same for production method to reduce costs.

Chalo

01-03-1970, 09:03 AM

jim beam wrote:
>
> Chalo wrote:
> >
> > When a man participates every part of
> > the process from finding new customers to shipping finished product,
> > he can keep his mind stimulated. When he just takes toolpaths from
> > somebody else and runs machinery, it's pretty difficult to maintain
> > any enthusiasm for the work.
>
> very true. and added to that, without experienced machinist/shop work
> input, serious design mistakes can be made. just like modern engineers
> seem to have lost any ability to design to their material, they seem to
> have no /clue/ about production process - and cnc production is the
> /prime/ culprit responsible. same for production method to reduce costs.

In my experience working with a couple of hotshot high-tech startups,
some engineers are able to accept suggestions from a "laborer", and
some just can't for whatever reason. It seems like a pass/fail issue
of basic engineering competence to me, but then... I'm not in
management.

If a design engineer can't take suggestions from someone below his
station, then it doesn't really matter whether there is a functioning
feedback mechanism or not. The problem is partly technological, as
you point out, and partly cultural. If we as a technological society
could surmount it, I bet we could resume our former status as the best
innovators in the world. But as our whole society becomes more
stratified, rank becomes more important and ability less so. The
decadence of technology turns out to be just another aspect of the
decline of empire.

Chalo

RonSonic

01-03-1970, 09:03 AM

On Sat, 28 Jul 2007 21:47:55 -0700, jim beam <spamvortex@bad.example.net> wrote:

>Chalo wrote:
>> raam...@gmail.com wrote:
>>> I was curious when i got into cycling, then some bike mags featured
>>> cnc machining and I wound up taking a course and doing that for awhile
>>> ( big mistake though, I hate noise and love the outdoors, fresh air, a
>>> challenge and freedom)
>>
>> I have to say, one of the downsides to CNC machining is that it limits
>> the inventive process to a small subset of the folks who participate
>> in the process. When a machinist took a blueprint and a piece of
>> metal and turned cranks with his own hands, the methods and steps were
>> largely left up to him. Now he's more likely to get a diskette with a
>> set of toolpaths on it, and nothing of significance is left to his
>> discretion.
>>
>> I think this is one of the reasons why many CNC machine shops are
>> small owner-operated outfits. When a man participates every part of
>> the process from finding new customers to shipping finished product,
>> he can keep his mind stimulated. When he just takes toolpaths from
>> somebody else and runs machinery, it's pretty difficult to maintain
>> any enthusiasm for the work.
>
>very true. and added to that, without experienced machinist/shop work
>input, serious design mistakes can be made. just like modern engineers
>seem to have lost any ability to design to their material, they seem to
>have no /clue/ about production process - and cnc production is the
>/prime/ culprit responsible. same for production method to reduce costs.

On another planet a long, long time ago I took a CNC programming class (complete
with punched tape) student instructions were first tested by "machining"
styrofoam blocks held in place with wooden clamps. One way to save tool costs in
case of error. I think it was considered more instructive to let them see the
destruction than to just hand it back with a mark through the obvious bad path.

Ron

raamman@gmail.com

01-03-1970, 09:03 AM

On Jul 29, 1:23 am, Chalo <chalo.col...@gmail.com> wrote:
> jim beam wrote:
>
> > Chalo wrote:
>
> > > When a man participates every part of
> > > the process from finding new customers to shipping finished product,
> > > he can keep his mind stimulated. When he just takes toolpaths from
> > > somebody else and runs machinery, it's pretty difficult to maintain
> > > any enthusiasm for the work.
>
> > very true. and added to that, without experienced machinist/shop work
> > input, serious design mistakes can be made. just like modern engineers
> > seem to have lost any ability to design to their material, they seem to
> > have no /clue/ about production process - and cnc production is the
> > /prime/ culprit responsible. same for production method to reduce costs.
>
> In my experience working with a couple of hotshot high-tech startups,
> some engineers are able to accept suggestions from a "laborer", and
> some just can't for whatever reason. It seems like a pass/fail issue
> of basic engineering competence to me, but then... I'm not in
> management.
>
> If a design engineer can't take suggestions from someone below his
> station, then it doesn't really matter whether there is a functioning
> feedback mechanism or not. The problem is partly technological, as
> you point out, and partly cultural. If we as a technological society
> could surmount it, I bet we could resume our former status as the best
> innovators in the world. But as our whole society becomes more
> stratified, rank becomes more important and ability less so. The
> decadence of technology turns out to be just another aspect of the
> decline of empire.
>
> Chalo

a lot of assemblies are farmed out to be manufactured as component
parts, so one has the faintest clue it might be for...but then again,
you have to understand that anyone who designs and builds "stuff"
wouldn't want anyone taking liberties with their design. one of my
places qc had a problem keeping the specified tolerance on a part and
after many costly attempts to better rectify the situation the
production manager submitted a formal request that the tolerance
standard be opened to the next level which we were achieving- the
answer was a resounding "no !" and after about 4 months or so the
contract went to someone else- the point being, what is "good enough"
ain't necessarily "good".

Peter Cole

01-03-1970, 09:03 AM

Chalo wrote:

> In my experience working with a couple of hotshot high-tech startups,
> some engineers are able to accept suggestions from a "laborer", and
> some just can't for whatever reason. It seems like a pass/fail issue
> of basic engineering competence to me, but then... I'm not in
> management.
>
> If a design engineer can't take suggestions from someone below his
> station, then it doesn't really matter whether there is a functioning
> feedback mechanism or not. The problem is partly technological, as
> you point out, and partly cultural. If we as a technological society
> could surmount it, I bet we could resume our former status as the best
> innovators in the world. But as our whole society becomes more
> stratified, rank becomes more important and ability less so. The
> decadence of technology turns out to be just another aspect of the
> decline of empire.

There used to be a lot more apprentice-mode learning in engineering
professions, and this used to mitigate the white/blue collar gap. The
main reason that this has disappeared is the same reason that
engineering disciplines have become more narrowly specialized -- the
pace of technical change. The phenomenon is observable in all the
technology driven fields (e.g. medicine). People simply don't have the
time for breadth, it's all they can do to maintain depth.

Another factor is passion. Many of today's technical professionals were
attracted by a paycheck. Only so many "naturals" are born, the rest are
just recruited to fill the slots. The "natural" engineers I've met all
had terrific hands-on skills, mostly because they were passionate enough
to get their hands dirty, having engineering as both a vocation and
avocation.

The best innovation comes from the combination of breadth and passion
with the prerequisite creativity and depth. Individuals with all that
have always been rare. Perhaps they're getting rarer, but with only so
many to go around, lucrative fields brain drain less lucrative ones, and
the faster the field is evolving the less time anyone has for anything
other than narrow specialization, so the inter-specialty and blue-white
collar gaps widen. If you see a bad blue-white gap, your particular
organization likely falls into one of those two camps
(drained-traditional or tech-race).

frkrygow@gmail.com

01-03-1970, 09:03 AM

On Jul 28, 9:23 pm, Chalo <chalo.col...@gmail.com> wrote:
>
> In my experience working with a couple of hotshot high-tech startups,
> some engineers are able to accept suggestions from a "laborer", and
> some just can't for whatever reason. It seems like a pass/fail issue
> of basic engineering competence to me, but then... I'm not in
> management.
>
> If a design engineer can't take suggestions from someone below his
> station, then it doesn't really matter whether there is a functioning
> feedback mechanism or not. The problem is partly technological, as
> you point out, and partly cultural. If we as a technological society
> could surmount it, I bet we could resume our former status as the best
> innovators in the world. But as our whole society becomes more
> stratified, rank becomes more important and ability less so. The
> decadence of technology turns out to be just another aspect of the
> decline of empire.

The ability to take suggestions from a "laborer" (or machinist, or
welder, or tool & die man, etc.) is probably more of a personal
characteristic than anything else.

There are certainly engineers who lack that ability, or lack any skill
at getting along with other factory workers, and who are less
effective as a result. But the problem of arrogance really can go
both ways. That is, I've seen engineers having to deal with tradesmen
who mistakenly thought they knew a lot more than the engineers about a
particular problem. The tradesmen were not only undiplomatic, but
literally mocking in their presentation of their mistaken
"knowledge." And it didn't seem to phase them when they were proven
wrong.

Nobody can be expert in everything, and no educational program has the
time to teach everything. Learning has to continue long beyond formal
education - ideally, until the end of one's life - and people do need
to learn from lots of different folks, including those with less
prestigious job titles.

But both the engineer and the craftsman need to realize that the
other, if competent, has knowledge he lacks. Ditto the physician and
physical therapist, the lawyer and the secretary, etc.

- Frank Krygowski

jim beam

01-03-1970, 09:04 AM

raamman@gmail.com wrote:
> On Jul 29, 1:23 am, Chalo <chalo.col...@gmail.com> wrote:
>> jim beam wrote:
>>
>>> Chalo wrote:
>>>> When a man participates every part of
>>>> the process from finding new customers to shipping finished product,
>>>> he can keep his mind stimulated. When he just takes toolpaths from
>>>> somebody else and runs machinery, it's pretty difficult to maintain
>>>> any enthusiasm for the work.
>>> very true. and added to that, without experienced machinist/shop work
>>> input, serious design mistakes can be made. just like modern engineers
>>> seem to have lost any ability to design to their material, they seem to
>>> have no /clue/ about production process - and cnc production is the
>>> /prime/ culprit responsible. same for production method to reduce costs.
>> In my experience working with a couple of hotshot high-tech startups,
>> some engineers are able to accept suggestions from a "laborer", and
>> some just can't for whatever reason. It seems like a pass/fail issue
>> of basic engineering competence to me, but then... I'm not in
>> management.
>>
>> If a design engineer can't take suggestions from someone below his
>> station, then it doesn't really matter whether there is a functioning
>> feedback mechanism or not. The problem is partly technological, as
>> you point out, and partly cultural. If we as a technological society
>> could surmount it, I bet we could resume our former status as the best
>> innovators in the world. But as our whole society becomes more
>> stratified, rank becomes more important and ability less so. The
>> decadence of technology turns out to be just another aspect of the
>> decline of empire.
>>
>> Chalo
>
> a lot of assemblies are farmed out to be manufactured as component
> parts, so one has the faintest clue it might be for...but then again,
> you have to understand that anyone who designs and builds "stuff"
> wouldn't want anyone taking liberties with their design. one of my
> places qc had a problem keeping the specified tolerance on a part and
> after many costly attempts to better rectify the situation the
> production manager submitted a formal request that the tolerance
> standard be opened to the next level which we were achieving- the
> answer was a resounding "no !" and after about 4 months or so the
> contract went to someone else- the point being, what is "good enough"
> ain't necessarily "good".
>

great example - the designer and producer should have been able to
figure this out. done right, either the design gets fixed or the
producer throws in the towel - it's stupid to leave it unresolved and
shift contractor where the same problems will reoccur.

Helmut Springer

01-03-1970, 09:05 AM

jim beam <spamvortex@bad.example.net> wrote:
> done right, either the design gets fixed or the producer throws in
> the towel - it's stupid to leave it unresolved and shift
> contractor where the same problems will reoccur.

How did you come to this assessment, given the little information
that was given?

Obviously the contract started with the specified tolerances for the
part in question and the vendor accepted them, probably with the
idea to be able to meet them inside his business model. Maybe he
misjudged his quality abilities and someone else does not, maybe
with a different business case.

--
MfG/Best regards
helmut springer

jim beam

01-03-1970, 09:05 AM

Helmut Springer wrote:
> jim beam <spamvortex@bad.example.net> wrote:
>> done right, either the design gets fixed or the producer throws in
>> the towel - it's stupid to leave it unresolved and shift
>> contractor where the same problems will reoccur.
>
> How did you come to this assessment, given the little information
> that was given?
>
> Obviously the contract started with the specified tolerances for the
> part in question and the vendor accepted them, probably with the
> idea to be able to meet them inside his business model. Maybe he
> misjudged his quality abilities and someone else does not, maybe
> with a different business case.
>
you might be right - wouldn't be the first time. but you might not.
the point is, successful manufacturing requires practical feedback from
the production team, not just one-way traffic from the design team. if
they're making mistakes, they need to know about it and work with it -
not just assume incompetence and move on to another producer that will
likely run into the same problem.

raamman@gmail.com

01-03-1970, 09:05 AM

On Jul 29, 10:36 am, Helmut Springer <delta+use...@lug-s.org> wrote:
> jim beam <spamvor...@bad.example.net> wrote:
> > done right, either the design gets fixed or the producer throws in
> > the towel - it's stupid to leave it unresolved and shift
> > contractor where the same problems will reoccur.
>
> How did you come to this assessment, given the little information
> that was given?
>
> Obviously the contract started with the specified tolerances for the
> part in question and the vendor accepted them, probably with the
> idea to be able to meet them inside his business model. Maybe he
> misjudged his quality abilities and someone else does not, maybe
> with a different business case.
>
> --
> MfG/Best regards
> helmut springer

when a part is for a car and that part has to be recalled because of
either a design or manufacturing error it's tens of millions of
dollars in charges for the maker- and for the consumer, when you need
to replace a part you expect the replacement part to fit- you don't
care about the manufacturing difficulties invovled. however,
sometimes difficulties can impinge on the design- look at the aztec,
the back end of that car is about the ugliest designs on the road, but
according to another discussion I had, it is the result of an
inability to get the manufacturing technology to work with the design,
so the design was changed in order to resolve the issue.