<[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
* * Chas said:
"Melt forged" was/is a BS term for injection molding, a method for
making
Quoted message said:
Quoted message said:
high quality castings.
I think you meant die casting, not injection molding. Although the processes are conceptually very similar, when it's done with metal, it's called die casting. When it's done with plastic, it's called injection molding. At least, that's true everywhere I've come across it.
Quoted message said:
A casting is still a casting and doesn't have the benefits of
increased
Quoted message said:
Quoted message said:
metal density that comes from forging.
Hmm. Well, forgings definitely tend to be stronger per unit weight, but there are a wide variety of casting processes. Some are clearly better than others regarding accuracy, finish, mechanical properties, etc.
As Andrew noted, it's certainly possible to make perfectly acceptable parts by casting. The cast parts may be a bit heavier, but the difference is probably undetectable to most riders.
When you get to the point where you're counting grams, then yes, you probably want forged parts.
Unless you go with carbon fiber. ;-)
- Frank Krygowski
You're right, the process is called Die Casting. I was in a hurry when I wrote that. I guess that I'm getting old and the memory gland doesn't always work as well as it once did. ;-)
Die casting is used to make castings from aluminum, magnesium, zinc alloys (zamac), and copper and it's alloys (brass & bronze).
I object to the term "melt forged" which is a misleading misnomer rather than castings in general.
it's not. "casting" is used for liquid solidification. "melt forged" or thixoforming does in no way produce the same product as casting.
Quoted message said:
Someone at a LBS showed me a hollow Shimano crank arm that had been cut in half. He said Shimano told him it was a forging. I looked it over and could tell it had been cast.
what features led you that conclusion? i ask because those things are most definitely forged - and the above illustrates that you have some confusion on this subject. if you have access to metallography, it would be good for you to use it - you'll see what i mean the moment you look down the microscope.
My objection is to the term "melt forged". Call it a high precision casting or something similar.
the material is a slurry of solid particles with just a little interstitial liquid at the time of forming. like ice slush in a slurpee. it's definitely not "casting" in any traditional sense.
By the same token, it's definitely not "forging" in any traditional sense.
"Ryan Cousineau" <[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
In article <[email hidden]>,
* * Chas said:
"vey" <[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
[email hidden] wrote:
Quoted message said:
Castings can be less expensive to produce because they are "near net sized" and can require less machining and finishing. That's why
they've
Quoted message said:
Quoted message said:
been used so much for inexpensive bike stems.
Hm. I thought the most fundamental issue, expense-wise, was the cost of the tooling and the equipment. Forging stamps are expensive, and the tooling is expensive too, because it has to be very strong, and probably has a shorter service life than an equivalent casting.
For die casting the costs for dies or molds can be quite expensive compared to the cost of forging dies because they are generally made to produce more accurate parts with mimimal additional work required.
Quoted message said:
The finishing is surely a factor, though.
The cost savings with castings has a lot to do with the reduced need for secondary machining and finishing operations.
Follow up question... in the days of yore, a blacksmith would repeatedly pound the part (iron or steel) into shape. It seems to me (intuitively) that this would tend to arrange the steel in a much more ordered fashion than simply hitting it with a massive multi-ton press just once. Or maybe in the multi-ton, he parts that actually get formed into a bend would pick up strength, but the parts that are left unbent would not gain strength.
Follow up question... in the days of yore, a blacksmith would repeatedly pound the part (iron or steel) into shape. It seems to me (intuitively) that this would tend to arrange the steel in a much more ordered fashion than simply hitting it with a massive multi-ton press just once. Or maybe in the multi-ton, he parts that actually get formed into a bend would pick up strength, but the parts that are left unbent would not gain strength.
Comments?
My understanding is, the entire forging gains strength, because 'the metal's grain flow changes into the shape of the part'. If you go to this link
http://en.wikipedia.org/wiki/Forge and click on the image in the 'Forging' section three times, you will get a close-up view of the grain flow.
I prefer forged aluminum stems myself. Back in the 1970s I had 3 cast stems break off while riding and it's not a comfortable feeling holding a set of bars in the air while trying to stop the bike. Two of the events were while road testing cheap French Bike Boom bikes, the 3rd time was with a Belleri stem on my own 1973 Gitane Super Corsa. They all failed at the splits for the wedge cone at the bottom of the quill.
I drilled holes at the end of the slots; they were obviously THE place where cracks would start.
<[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
* * Chas said:
"Melt forged" was/is a BS term for injection molding, a method for
making
Quoted message said:
Quoted message said:
high quality castings.
I think you meant die casting, not injection molding. Although the processes are conceptually very similar, when it's done with metal, it's called die casting. When it's done with plastic, it's called injection molding. At least, that's true everywhere I've come across it.
I was thinking "die casting" when I wrote "injection molding" in several messages.
The term injection molding usually refers to the plastics industry but it can be used to describe the manufacturing processes for both plastic molding and metal die casting.
I was unfamiliar with the term thixoforming. I ran across the above site searching on thixoforming. I heard about the process about 10 years ago when I visited an aluminum mfg. who was making the slugs for the process but it was called a number of different names. I've never seen the actual process in use.
No matter how good the results, thixoforming, vacuum casting melt forging or what ever it's called is still not forging.
"Melt forged" was/is a BS term for injection molding, a method for making high quality castings.
Quoted message said:
<[email hidden]> wrote
Quoted message said:
I think you meant die casting, not injection molding. Although the processes are conceptually very similar, when it's done with metal, it's called die casting. When it's done with plastic, it's called injection molding. At least, that's true everywhere I've come across it.
* * Chas said:
I was thinking "die casting" when I wrote "injection molding" in several messages.
The term injection molding usually refers to the plastics industry but it can be used to describe the manufacturing processes for both plastic molding and metal die casting.
I was unfamiliar with the term thixoforming. I ran across the above site searching on thixoforming. I heard about the process about 10 years ago when I visited an aluminum mfg. who was making the slugs for the process but it was called a number of different names. I've never seen the actual process in use.
No matter how good the results, thixoforming, vacuum casting melt forging or what ever it's called is still not forging.
Right. But the greater bulk of our industry's mid to low end equipment is much the better for these processes, gravity castings being pretty much obsolete for aluminum bicycle parts. No one makes an AVA or Pivo cast stem or its equivalent now fortunately! A choice of Record or sand cast is not a reasonable choice for everyone. (jim beam first introduced me to the the term 'thixoform' here. The SR-Sakae folks all said 'melt-forge'😉 -- Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971
I'm not a metallurgist (nor do I play one on the 'net), but back in the day, we had "forged" and "melt-forged" stems, the "melt-forged" versions being less-expensive and, according to SR and Shimano, were forgings done at higher temperatures and not as strong as a lower-temp (room temp?) forging. I never looked into it beyond such claims; others here will know if this is actually true or not.
Jasper Janssen said:
'Cold-forged' steel AFAIK just starts at room temp, after being spectacularly deformed under massive pressure, it heats up to "can burn you" levels at least, when it comes out of the process.
Drop-forged, as seem on many wrenches (especially cheap ones), AFAIK involves using a Very Big Hammer (several tons of weight) which fall from a height onto the steel and shape it that way, in one go. I think those typically hot-forge.
Have you seen a 5 or ten ton forge? It drops. That's what it is/does.
'Cold-forged' steel AFAIK just starts at room temp, after being spectacularly deformed under massive pressure, it heats up to "can burn you" levels at least, when it comes out of the process.
Quoted message said:
Quoted message said:
Drop-forged, as seem on many wrenches (especially cheap ones), AFAIK involves using a Very Big Hammer (several tons of weight) which fall from a height onto the steel and shape it that way, in one go. I think those typically hot-forge.
Quoted message said:
Have you seen a 5 or ten ton forge? It drops. That's what it is/does.
But on warm or cold steel?
AFAIK, fairly large steel parts like wrenches that are made in large forging presses are always done hot. I'm talking about impression die forging, where the die that does the shaping has cavities in the shape of the part. Steel gets much, much more ductile when it's raised above a certain temperature (roughly 1400 deg. F). That allows it to flow into complex shapes.
Steel in the form of thin rods or sheets is formed at room temperature. But doing a wrench handle that way would destroy forging dies in short order, even though they're made of very strong tool steels.
"Mike Jacoubowsky" <[email hidden]> wrote: > I'm not a metallurgist (nor do I play one on the 'net), but back in the day, > we had "forged" and "melt-forged" stems, the "melt-forged" versions being > less-expensive and, according to SR and Shimano, were forgings done at > higher temperatures and not as strong as a lower-temp (room temp?) forging. > I never looked into it beyond such claims; others here will know if this is > actually true or not.
Quoted message said:
Quoted message said:
Jasper Janssen said:
'Cold-forged' steel AFAIK just starts at room temp, after being spectacularly deformed under massive pressure, it heats up to "can burn you" levels at least, when it comes out of the process. Drop-forged, as seem on many wrenches (especially cheap ones), AFAIK involves using a Very Big Hammer (several tons of weight) which fall from a height onto the steel and shape it that way, in one go. I think those typically hot-forge.
Quoted message said:
A Muzi said:
Have you seen a 5 or ten ton forge? It drops. That's what it is/does.
Jasper Janssen said:
But on warm or cold steel?
I'm sorry I was a bit terse. When a chunk of steel gets smashed with a few tons in a forging die, it comes out hot. Very hot.
If you start with a red-hot piece, the required impact to get grain alignment is less (as with hammer and tongs and a fireplace). -- Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971
I am pretty certain that my Sugino Maxy cranks (purchased in 1975-6, $29.95 cranks and BB complete) were melt-forged and anodized. So, there is at least one mistake in this article listed above.
I am pretty certain that my Sugino Maxy cranks (purchased in 1975-6, $29.95 cranks and BB complete) were melt-forged and anodized. So, there is at least one mistake in this article listed above.
I still have a Maxy of that era, but it is definitely not anodized.
My objection is to the term "melt forged". Call it a high precision casting or something similar.
the material is a slurry of solid particles with just a little interstitial liquid at the time of forming. like ice slush in a slurpee. it's definitely not "casting" in any traditional sense.
By the same token, it's definitely not "forging" in any traditional sense.
"* * Chas" <[email hidden]> wrote: > "Melt forged" was/is a BS term for injection molding, a method for > making high quality castings.
Quoted message said:
<[email hidden]> wrote
Quoted message said:
I think you meant die casting, not injection molding. Although the processes are conceptually very similar, when it's done with metal, it's called die casting. When it's done with plastic, it's called injection molding. At least, that's true everywhere I've come across it.
* * Chas said:
I was thinking "die casting" when I wrote "injection molding" in several messages.
The term injection molding usually refers to the plastics industry but it can be used to describe the manufacturing processes for both plastic molding and metal die casting.
I was unfamiliar with the term thixoforming. I ran across the above site searching on thixoforming. I heard about the process about 10 years ago when I visited an aluminum mfg. who was making the slugs for the process but it was called a number of different names. I've never seen the actual process in use.
No matter how good the results, thixoforming, vacuum casting melt forging or what ever it's called is still not forging.
Right. But the greater bulk of our industry's mid to low end equipment is much the better for these processes, gravity castings being pretty much obsolete for aluminum bicycle parts. No one makes an AVA or Pivo cast stem or its equivalent now fortunately! A choice of Record or sand cast is not a reasonable choice for everyone. (jim beam first introduced me to the the term 'thixoform' here. The SR-Sakae folks all said 'melt-forge'😉
that's because "melt-forge" sounds better than "slurry-sloshing"!
Follow up question... in the days of yore, a blacksmith would repeatedly pound the part (iron or steel) into shape. It seems to me (intuitively) that this would tend to arrange the steel in a much more ordered fashion than simply hitting it with a massive multi-ton press just once. Or maybe in the multi-ton, he parts that actually get formed into a bend would pick up strength, but the parts that are left unbent would not gain strength.
Comments?
My understanding is, the entire forging gains strength, because 'the metal's grain flow changes into the shape of the part'. If you go to this link
http://en.wikipedia.org/wiki/Forge and click on the image in the 'Forging' section three times, you will get a close-up view of the grain flow.
I prefer forged aluminum stems myself. Back in the 1970s I had 3 cast stems break off while riding and it's not a comfortable feeling holding a set of bars in the air while trying to stop the bike. Two of the events were while road testing cheap French Bike Boom bikes, the 3rd time was with a Belleri stem on my own 1973 Gitane Super Corsa. They all failed at the splits for the wedge cone at the bottom of the quill.
I drilled holes at the end of the slots; they were obviously THE place where cracks would start.
why? the slot is not subject to stress perpendicular to its axis - that's the only situation where the slot will be a stress riser requiring drilling.
I am pretty certain that my Sugino Maxy cranks (purchased in 1975-6, $29.95 cranks and BB complete) were melt-forged and anodized. So, there is at least one mistake in this article listed above.
John Thompson said:
I still have a Maxy of that era, but it is definitely not anodized.
Original stamped outer ring 3-bolt type were tumble polished I believe.
Later Maxy NJX (the first 110mm chainrings! woo hoo!) and Super Maxy were anodized. Super Maxy in colors. -- Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971
