Hacker News Reader

Comment by netfl0 | Hacker News Reader

This was the most compelling explanation of the visuals. They are saying that Telsa put function radically over form to reduce manufacturing complexity and efficiency. This is a purely utilitarian approach that is not self-evident.

I hope Telsa will put together a better presentation to explain this to the public. This is the sort of technical progress you'd like to see in other domains.

View on HN

These are mostly old manufacturing ideas which affect crash safety; repairability, an street legality.

It reminds be a lot of the DeLorean.

Could you please explain how it affects those things? I'd be very interested in learning about that.

I can't speak towards repairablity and legality, but I know cars are safer now than they used to be back when they were made of steel, because they crumple which absorbs the impact of crashes. Rigid steel transfers the impact to it's occupants.

I'm eager to see how this thing performs in crash tests.

Ah that makes sense. I'm interested to see how it performs there too

Yes they affect them, not all in a negative way.

unconvinced. long, precise, sharp angles are expensive to stamp on thick steel plates.

so I've checked around the pictures, apparently the marketing material has seams along the angle, but the car in the presentation has angled plates.

something doesn't add up https://imgur.com/a/HO1HnGC

I figured they would be using a brake[0] for the bends.

[0] https://en.wikipedia.org/wiki/Brake_(sheet_metal_bending)

yeah but that doesn't make really sharp angles and controlling the curve where it bends precisely is hard, fighting that is going against the claim it's about manufacturing efficiency

Point well taken.

There are multiple dimensions to manufacturing efficiency, though, right? I have no appreciation for the cost of a couple dies and a machine for stamping versus the cost of a CNC break with one die, but it may play a part based on the number of units they think they will sell. (1,000? 10,000? 100,000?)

If starting with super hard cold rolled steel, it’s most likely impossible to “stamp” using traditional progressive stamping dies. The deformation has to exceed the final shape and via springback the final shape is produced.

Springback is possible on a press brake when folding along a single straight line. If panel needs a 30 deg bend, then bend it to 40, and it pops back 10 when off the press brake. As an example.

That quickly gets impossible to do when you start bending around complicated 3D contours.

That's a lot slower than stamping from sheet and has all kinds of limitations with respect to angles and manufacturability. I've used them a lot making sheetmetal enclosures for industrial hardware, it's great for simple stuff, right angles and other common shapes but if you start doing sheets that have multiple bends at precise angles at odd angles to each other you'll run into the geometric limitations very quickly. Keep in mind that the wedges need to cover all of the angle for the brake to work and that you need to be able to remove your work without disassembling the tool.

This is a more likely option:

https://www.247tailorsteel.com/en/plate-bending

These machines will do full sized sheets as well and are much more versatile than a brake, also far faster.

I believe that is a type of brake, a press brake.

Ah ok, I do not know the name for that particular tool but I've seen them in use for sheetmetal bending in large quantities.

The device the OP linked to is meant to be hand operated and only for small series. Setup takes forever and then some, redoing a setup for another batch is impossible because it will all come out slightly different.

That 'press brake' uses a tool-and-die style mechanism to deform the sheet, very accurate and highly repeatable, quick as well, cycle time is a few seconds.

Is there any reason they wouldn't just make those independant panels and weld those joints? It's a little slower than stamping, but cutting and welding panels like this is well within the capabilities of their existing robots.

From what I understand, the outside of this car is bare stainless steel. Can humans or robots make welds that don’t show Up as ugly warts on the outside? If so, can it be done cheaply enough?

Fair enough. I supposed the structural weld could be on the inside to hide the bulge. But you'd need some tight tolerances for that to look good from the outside.

Order of magnitude cheaper to start with flat sheet, lasercut/waterjet/stamp out final shape, and bend.

They are starting the cut and bend operations with the fully hardened steel, so there is no post stress relieving / aging / finishing. It's about as simple as it can get for metal fabrication.

Welding also fundamentally changes the underlying steel properties. I'm not up to speed on full hard 301 SS, but most likely any thermal operation will degrade it's mechanical and chemical grain structure.

Saw this on Reddit. Seems to show a panel there which opens up. I don't think we can trust anything but the major bullet points making it to production though. This thing is a prototype and much of what we see could be up in the air.

https://imgur.com/a/r4drdJh

Reply on news.ycombinator.com