I Think Cybertruck Manufacturing Run Will be Short Lived

[Revoltlution]

I am just saying the outer "silhouette" can be stamped using a cutting die, no forming or shaping would be needed. The general shape of the flat panel can be stamped out of the sheet instead of being laser cut. This would be much faster and economical compared to the laser.

Hmmm, I LOVE how the CT tickles our engineering minds.
My guess is any stamp cutter would have a high operating cost maintaining the die/cutters and slow to make engineering changes, especially with this cold-worked stainless. I could be wrong, considering this is only 3mm.

[lasers vs stamping]
Lasers

• pro: reduced maintenance and clean process
• pro: repeatable, high tolerance and clean edges eliminates secondary operation
• pro: pro systems can easily cut <1" stainless (CT is ~3mm)
• pro: one machine (footprint) can cut any part and make just-in-time modifications
• con: cutting speed is slower then stamping, but proportional to watts!
• con: can change material's edge properties (color, hardness) due to heating

Stamp Cutting

• pro: faster than lasers, especially with difficult materials
• pro: could combine shaping steps
• con: retooling time and money to make edits or add parts
• con: more tooling wear and maintenance
• con: cut quality can effect tolerances and fit/finish

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[Crissa]

There's also water cutting, electrode wire cutting, score cutting... More ways to cut steel than I know.

-Crissa

 

[Sonnus]

Hmmm, I LOVE how the CT tickles our engineering minds.
My guess is any stamp cutter would have a high operating cost maintaining the die/cutters and slow to make engineering changes, especially with this cold-worked stainless. I could be wrong, considering this is only 3mm.

The tube on CNC lasers are considered a consumable part. They only last so long like a light bulb. And they’re not cheap.

Also, CNC lasers take up a LOT of space. The table would likely need to be around 8’x15’ to cut the parts for the Cybertruck, maybe bigger. And they would need dozens, maybe hundreds of these CNCs to get the job done. One shop I work with has just two large CNCs in about a 10,000 sqft warehouse and there isn’t a lot of space left over.

The dies for a punch press definitely aren’t cheap but they will last for thousands and thousands of parts. If you were just going to make 100 blanks then the dies would not be cost effective but when you are making thousands then the economics start leaning in that direction.

 

[Sonnus]

There's also water cutting, electrode wire cutting, score cutting... More ways to cut steel than I know.

-Crissa

I do like water jet, it is a cleaner cut than lasers. Lasers cut parts aren’t perfect, they usually have a bit of dross/slag left over that typically needs to be sanded or grinded off. Only problem with water jet is they are even slower than lasers most of the time. Plasma would likely be the cheapest option for a CNC table but then you end up with even more slag.

 

[Crissa]

The dies for a punch press definitely aren’t cheap but they will last for thousands and thousands of parts. If you were just going to make 100 blanks then the dies would not be cost effective but when you are making thousands then the economics start leaning in that direction.

Thousands of parts made from hardened steel?

-Crissa

 

[Sonnus]

Thousands of parts made from hardened steel?

-Crissa

I can’t image it being a problem. The Cybertruck’s 3mm panels are around 11 ga, this is not a difficult job for a heavy-gauge blanking press. I see pressed parts made from 1/2” mild steel regularly. The stainless is obviously harder but these presses can usually do 1/4” stainless with no problem. And these massive presses can pump out large blanks (think Cybertruck large) at 30 blanks per minute. A comparable laser cut piece would probably be closer to 1 per minute. So you would need maybe 30 laser CNC tables for every 1 blanking press.

If Tesla is planning an working/rolling the stainless steel beyond the standard cold rolled 304L that comes out of most mills then maybe they can just do this after the part comes out of the press. Whether they work a flat sheet (pre stamped) to harden it or work a flat already cut panel makes little difference. This is usually how things are manufactured anyway, the hardening process is always done after the part is made.

 

[Crissa]

You keep mixing up 'hardened' and replacing it with 'mild' and 'stainless' which are not 'hardened'.

So I don't know. Your press would need to have a large die of even more hardened steel...

-Crissa

 

[Sonnus]

You keep mixing up 'hardened' and replacing it with 'mild' and 'stainless' which are not 'hardened'.

So I don't know. Your press would need to have a large die of even more hardened steel...

-Crissa

I reference mild steel because that is what is most common, you see it everywhere. If a machine can process 1/2” mild steel then it can typically handle about 1/4” 304L stainless. To estimate capabilities you can use mild steel as a reference just halve it to estimate the machines capabilities with stainless. This rough estimate is applicable along many different processes.

If you see a manufactured part made of 1/2” mild steel then you can typically assume that same part can be made of 1/4” 304L on the same equipment.

Regular old 304L stainless straight out of the mill is nasty hard material. Much, much harder than hot or cold rolled steel.

When Tesla says they use hardened 30x stainless I think that is misleading. It is already hard AF from the beginning. I’m sure you can work regular 304L the make it a bit harder but realistically you’re not going to change it much. And the ductility of the material is going to decrease the more you harden it, this is usually not a good thing.

 

[Sonnus]

Also, hardening is a very general term. In regards to the Cybertruck I believe they are referring to cold rolled hardening.

This is different than what most think of in regards to hardened steel. The term “hardened steel” almost always refers to tempered steel. Usually this involves heating the steel up and then quenching it but you can also draw down the material (forging or rolling) to accomplish this. The tempering is always done after the part is made. Working hardened steel is obviously hard on your equipment (maybe impossible) and you will loose some of the temper by working the material. In fact, once you have done a lot of work with a piece of hardened metal you need to send it back for heat treatment to get the temper back to spec.

Most mills offer cold rolled steel. This just means that the hot rolled steel makes another pass through rollers once it has cooled off to give better finish and tolerances. Cold rolled steel is a tiny bit harder than hot rolled steel but I don’t think anyone considers cold rolled steel “hardened” steel. And cold rolled steel isn’t much different to work with compared to hot rolled steel. Regular 304L is WAY harder than cold rolled steel and much harder to work with.

 

[Crissa]

Since they're using a specific material they're getting for Starship, we just can't really say what hardness it'll be at until we have it in our hands. Or what tools they choose to use.

Either way, those tools sound large, if simpler than usual automotive stamping.

-Crissa

 

[Sonnus]

Heavy Gauge Press

Here is a 4000 ton press, they say they can accommodate blanks up to 72” x 100” and the capacity is up to 5/8” steel plate (maybe 5/16” stainless?). There is a video on the page that’s shows it in action.

A press this size could likely stamp all of the parts needed for the Cybertruck but Tesla could definitely get something bigger if needed.

 

[Sonnus]

Since they're using a specific material they're getting for Starship, we just can't really say what hardness it'll be at until we have it in our hands. Or what tools they choose to use.

Either way, those tools sound large, if simpler than usual automotive stamping.

-Crissa

That is a good point, they are already cutting/stamping parts for the Starship. Since the shapes in the Starship are pretty basic I would imagine they are using some sort of CNC shear/brake/roll for these. The CNC cuts and contours the sheet all on one machine.

 

[Sonnus]

And if they can shear the stainless on the Starship then a blank stamping press die would be no problem.

 

[LoPro]

I can’t understand (max) half of what is said in this thread, but I am in awe of the knowledge here. And hope you are right in whatever the consensus of best solution for Tesla long term is.?

/End intermission

 

[Revoltlution]

Let's just run a crowd-sourced poll... that should give us a good "best guess" of what they will use