3D printed uprights? - LotusTalk - The Lotus Cars Community
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post #1 of 18 (permalink) Old 11-28-2018, 09:14 AM Thread Starter
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3D printed uprights?

3ders.org - Carbon Performance 3D prints high-performance suspension upright for Lotus Elise | 3D Printer News & 3D Printing News

Looks like something out of Alien.

I donít know if Iíd trust these things holding the car up
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post #2 of 18 (permalink) Old 11-28-2018, 10:02 AM
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Cool idea, but I agree. Without some serious testing I wouldn't trust it either.
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post #3 of 18 (permalink) Old 11-28-2018, 10:46 AM
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It looks alien because of the artificial intelligence aspect - you set up the loads and tell it where it is and isn't allowed to put material, and then it runs through tons of iterations and gives a pretty organic shape. Human design is less organic because it is built from basic shapes (prisms, spheres, planes), so AI designs can make a less wasteful design. They're also getting pretty good now with post-processing (google hot isostatic pressing) to get printed metal to nearly 100% density, but you still won't get close to the price of a cast piece.

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post #4 of 18 (permalink) Old 11-28-2018, 01:05 PM
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I suspect it would survive static loading tests fine. I would insist on that sort of testing before putting it on a car. My concern is not with the design - it does indeed make sense given the iterative AI fitting and I can certainly believe it is 25% lighter and 25% stiffer than the stock part (note that those are the only quantifiable claims the video makes).

A bigger concern is that, as it is not a cast metal forging, it might not fail gracefully. Powder metal connecting rods are known for being great until they hit the very sharp limit, for instance.

A suspension upright is the sort of component you want to bend when it yields in preference to a fracture, because having a wheel sticking out at an angle is a lot better than having it departing the vehicle at speed.

That 25% unsprung weight loss is appealing for a race car, though.
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post #5 of 18 (permalink) Old 11-28-2018, 11:25 PM
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I suspect it would survive static loading tests fine. I would insist on that sort of testing before putting it on a car. My concern is not with the design - it does indeed make sense given the iterative AI fitting and I can certainly believe it is 25% lighter and 25% stiffer than the stock part (note that those are the only quantifiable claims the video makes).

A bigger concern is that, as it is not a cast metal forging, it might not fail gracefully. Powder metal connecting rods are known for being great until they hit the very sharp limit, for instance.

A suspension upright is the sort of component you want to bend when it yields in preference to a fracture, because having a wheel sticking out at an angle is a lot better than having it departing the vehicle at speed.

That 25% unsprung weight loss is appealing for a race car, though.
Cast metal forging? Metals are either cast or forged, not both. Also, when a material yields, it stretches... "fracturing" is a certain type of brittle failure. There is also ductile failure.

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post #6 of 18 (permalink) Old 11-29-2018, 07:42 AM
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"A QR code is included on the part that links it to a digital inventory ecosystem thatís secured by blockchain, the same code used by cryptocurrencies"

How is this any better than printing a serial number and manufacturing date on the part? And why would a parts inventory need to be secured by blockchain?
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post #7 of 18 (permalink) Old 11-29-2018, 07:54 AM
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"A QR code is included on the part that links it to a digital inventory ecosystem thatís secured by blockchain, the same code used by cryptocurrencies"

How is this any better than printing a serial number and manufacturing date on the part? And why would a parts inventory need to be secured by blockchain?
Lots of things on that page scream marketing and hype over substance. Was there any actual pictures of the part on a car on that page?

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post #8 of 18 (permalink) Old 11-29-2018, 01:37 PM
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Cast metal forging? Metals are either cast or forged, not both. Also, when a material yields, it stretches... "fracturing" is a certain type of brittle failure. There is also ductile failure.
A material yields when it stops being elastic on the stress-strain curve: EG you can't go back to the shape you came from just by taking the stress (load) off.

If it came apart, guess what: it still yielded first.

Cast and forged:

Where did you think the blank that goes into the hammer, or HIP forge comes from?

"Forging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer (often a power hammer) or a die."
-https://en.wikipedia.org/wiki/Forging

Step one: procure a blank to forge

The blank can be a hunk of billet steel in which case you're going to do a lot of shaping either with the forge or afterward with machining. That's expensive for mass production.

Billet steel is defined as an intermediate casting.

Common for mass produced parts like this is to cast a blank of the desired alloy closer to a net shape, heat it to forging temperature, then forge it even closer to net shape with a couple of hits, then heat treat and machine as needed. Lots less forge time needed this way.

Either way, it started off as a casting.

So yes, cast and forged.
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post #9 of 18 (permalink) Old 11-29-2018, 01:50 PM
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"A QR code is included on the part that links it to a digital inventory ecosystem thatís secured by blockchain, the same code used by cryptocurrencies"

How is this any better than printing a serial number and manufacturing date on the part? And why would a parts inventory need to be secured by blockchain?
It's not any better and there's no reason to secure a parts inventory via blockchain. Blockchain just happens to be the hot marketing buzzword right now.

I would argue that a serial number and manufacture date is actually much better that sticking a QR code on it. For one, you're not going to get any useful info glancing at a QR code, at least you can tell when it was made with a serial and date. For two, you scratch the corner off a QR code and it's basically unreadable, scratch the corner off a serial number plate and maybe you lose one digit. A serial number missing one digit can still be useful.
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post #10 of 18 (permalink) Old 12-03-2018, 10:18 PM
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Originally Posted by steelypip View Post
A material yields when it stops being elastic on the stress-strain curve: EG you can't go back to the shape you came from just by taking the stress (load) off.

If it came apart, guess what: it still yielded first.

Cast and forged:

Where did you think the blank that goes into the hammer, or HIP forge comes from?

"Forging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer (often a power hammer) or a die."
-https://en.wikipedia.org/wiki/Forging

Step one: procure a blank to forge

The blank can be a hunk of billet steel in which case you're going to do a lot of shaping either with the forge or afterward with machining. That's expensive for mass production.

Billet steel is defined as an intermediate casting.

Common for mass produced parts like this is to cast a blank of the desired alloy closer to a net shape, heat it to forging temperature, then forge it even closer to net shape with a couple of hits, then heat treat and machine as needed. Lots less forge time needed this way.

Either way, it started off as a casting.

So yes, cast and forged.
A-ha...so, to make an analogy of your wikipedia "knowledge", coal is carbon and diamonds are carbon so, where do you think the coal for the diamonds come from? It's amazing what a little heat and pressure can do to a material.
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post #11 of 18 (permalink) Old 12-04-2018, 04:53 AM
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Either way, it started off as a casting.

So yes, cast and forged.
If I have a red car, paint it blue, then someone steals, will I report a red car was stolen or a blue one? Forging fundamentally changes a microstrucutre so it is considered to be very different from cast. Additionally, some billet materials cannot be cast well. Any 4 digit aluminum signifies billet that is then machined, pulverized, or forged. 3 digit aluminum signifies one that is easily cast well.

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post #12 of 18 (permalink) Old 12-04-2018, 05:02 AM
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...sigh. So you say that the source metal comes from somewhere other than a casting in the case of traditional ferrous forgings? Do tell... Your counterargument so far is that I cited Wikepedia, while you cited nothing at all. You're failing on preponderance of evidence if nothing else.

I was using the 'cast and forged' terminology to point out the difference in method between that and powder-HIP forgings or these 3D printed uprights (I have seen two 3D printing technologies that work on alloys - one uses X ray to melt the powder together, the other uses oven post processing to sinter the material).

And before you get snarky about citations again, I saw the 3d printing tech at the Oak Ridge National Laboratory Manufacturing Demonstration Facility a couple of years ago. They were using one of them to 3D print stainless steel parts for submersibles.

It's not my fault that you didn't know where forgings come from, so save the snark for somebody who cares.
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post #13 of 18 (permalink) Old 12-04-2018, 06:00 AM
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Looks like something out of Alien.
I don’t know if I’d trust these things holding the car up
I suspect this comment wasn’t so much an engineering analysis as it was a way to register his unfamiliarity with a new structural form created by additive manufacturing techniques.

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Cool idea, but I agree. Without some serious testing I wouldn't trust it either.
No kidding! This comment suggests testing is optional . . . no serious engineering / manufacturing firm would omit testing such a part. Theoretical models for even traditional manufacturing techniques are rarely (if ever) good enough to omit real-world testing, especially in mission-critical or safety-related applications.

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. . .
A bigger concern is that, as it is not a cast metal forging, it might not fail gracefully. Powder metal connecting rods are known for being great until they hit the very sharp limit, for instance.
. . .
@steelypip is comparing the characteristics of a part manufactured using a traditional forging process with a powdered metal part. That’s a valid and useful contrast to consider when evaluating something like the upright cited by the OP. Maybe you don’t like his terminology . . . but if that’s all you got from his words, you're missing the point (and I would suggest doing so on purpose). Regarding a cast blank for forging, I don’t know how to get molten metal out of a crucible except to pour it into a mold or squeeze it through a die. In either case, that metal sits around in something and cools (often even if it goes through some kind of cooled die), and that thing is often called a mold. That’s pretty much the definition of casting. But again, that’s not his point: it is clear fused powdered metal and molten metal somehow obtained from a crucible and given a shape will have different characteristics.

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Cast metal forging? Metals are either cast or forged, not both. Also, when a material yields, it stretches... "fracturing" is a certain type of brittle failure. There is also ductile failure.
You have a long history of trolling and being shown to talk about things of which you clearly have no expertise. I find it difficult to take anything you say seriously.

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If I have a red car, paint it blue, then someone steals . . .
Wait . . . I thought we were talking about manufacturing processes related to metal. What?

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. . . so save the snark for somebody who cares.
Normal people aren’t experts on everything. What’s cool about a forum like this is we can come together and share the little bit each of us knows. Then normal people can gain some insight into previously unfamiliar topics. That model fails when people purposely sabotage it (looking at you MGK), contribute by making sh*t up to look smarter than they are, or don’t try to overcome the inherent difficulties of communicating. There’s a benefit to be had here on LotusTalk . . . so far this thread is a great demo of how to totally miss out on that.

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post #14 of 18 (permalink) Old 12-04-2018, 07:44 AM
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Here is an aerospace manufacturer using an additive manufacturing technique for structural parts: Norsk Titanium. Among other items, they make landing gear parts designed and tested to withstand high loads.

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post #15 of 18 (permalink) Old 12-04-2018, 01:39 PM
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I have some experience with numerical shape optimization (and 3D printing complex metal parts), and my concern is that the resulting geometry is highly dependent on the assumed loading and boundary conditions. If the loading conditions are limited or overly simplistic, the resulting part is likely to be too weak under real world loads that don't match the assumed loads. Not an easy problem to solve because uprights are subject to highly complex loads during cornering, suspension impact, braking, and infinite combinations of same.

Still, 3D printed parts have great potential, provided the material properties of the printed metal are roughly equivalent to forged metal (of a similar alloy); and we can probably all agree that physical testing is critical.

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post #16 of 18 (permalink) Old 12-04-2018, 06:02 PM
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This steering knuckle created by German engineering students has some similarities to the one @darkSol linked to.

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. . . my concern is that the resulting geometry is highly dependent on the assumed loading and boundary conditions.
. . .
Modeling problems were eventually overcome during the development of “traditional” methods of manufacture like welded tube and sheet, castings, forgings and stampings. Where models underestimated strength requirements, iterative testing improved parts until they met or exceeded requirements. The same process will likely be used for additive manufacturing. The promise of additive manufacturing is that parts can be lighter, stronger and less expensive to produce when accurate modeling and otherwise unattainable shapes are brought to bear.

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Last edited by Glen; 12-04-2018 at 06:19 PM. Reason: add comment about testing
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post #17 of 18 (permalink) Old 12-04-2018, 06:16 PM Thread Starter
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I suspect this comment wasnít so much an engineering analysis as it was a way to register his unfamiliarity with a new structural form created by additive manufacturing techniques.
Correct. I was commenting on the organic appearance of the part and am only familiar with plastic additive 3d printing (ABS/Nylon). I freely acknowledge that I know nothing about additive 3d printing with metals.

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post #18 of 18 (permalink) Old 12-04-2018, 06:29 PM
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Forging fundamentally changes a microstrucutre so it is considered to be very different from cast. Additionally, some billet materials cannot be cast well.
No argument at all, but not really the point I was (apparently poorly) trying to elucidate by using the opposition of "cast and forged" versus "powder metal forged" versus "3D printed and not clear how/if it was post processed"

People have been hammer forging ferrous metal for almost as long as blacksmiths have existed. Industrial impression/closed die forging is newer (one source I found says 1862), but that still means the process has been in use for more than a century. The effects of different forging methods on the grain structure of a cast blank are extremely well understood, and have been since at least as early as the 1940s. The only significantly new technology I can name in this space is cryotreatment, and that's not especially new either.

This means that any competent mechanical engineer used to working in ferrous forgings will have a standard cookbook of alloys and processes to get you a part that meets your strength, durability, mass, and cost requirements. The part will behave predictably -- a property universally appreciated in suspension components.

By comparison, powder metal technologies (including the metal-compatible 3D printing technologies I've seen) are a lot newer for structural metals. Sintering has been around for millenia, but powdered metal as a source material for structural parts with 'forged-like' characeristics is less than 50 years old: HIP structural airplane parts were the new thing in the late 1970s if you had the money, and the argument for them at the time (in ferrous metals) was that the near-net shape out of the press saved on finish machining costs over closed die forging, particularly on complex shapes.

My point is that the expected behavior of a suspension part made by an additive method method is not well understood. Further, the scanty information we have from the vendor doesn't address either the material science questions or the excellent point @AustinP made about the accuracy of the algorithmic stress model used to generate the shape.

Last edited by steelypip; 12-04-2018 at 06:34 PM.
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