cross-posted from: https://kbin.social/m/[email protected]/t/384191

Tesla is facing issues with the bare metal construction of the Cybertruck, which Elon Musk warned was as tricky to do as making Lego bricks

  • @HazdazOP
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    1010 months ago

    There are so few things posted to this sub, but if there is actually anyone around, if you need a good laugh, go read what that buffoon Elon is demanding the parts to his cybertruck are held to.

      • @HazdazOP
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        310 months ago

        He might as well forget it too, since it seems like all his customers and the automotive press have forgotten about it and simply given him a free pass. It amazes me how much leeway journalists have given Tesla - especially in the early years.

        • @[email protected]
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          510 months ago

          Yeah, it’s almost like he has enough money to pay to keep reality out of the news. 😇

  • @demonhockey
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    910 months ago

    Dealing with needing to get a bunch of different processes to about 10um accuracy right now. It’s hard just to measure accurately at that accuracy. You start dealing with people walking by causing measurement error.

    • @HazdazOP
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      710 months ago

      You need temperature control. The heat from you hands can expand something a few tenths.

  • @dragontamer
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    10 months ago

    I’m not a mechanical engineer but I’m happy this story was posted here so that I can ask questions!!

    What are typical tolerances on large steel and/or aluminum and/or plastic parts on car sized panels? As a non-mech-e I’m not instinctively seeing the problem here.

    EDIT: Oh wait a sec… I just made a hobby PCB with 130um tolerances. (5mil or 0.13mm). Huh… Single digit micron tolerance is absurd.

    • @HazdazOP
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      1910 months ago

      It varies.

      You WANT to be as loose as possible while still sserving the function of what the part is supposed to do. The reason for that is every time you tighten tolerances, prices skyrocket to make that part. Drill a hole is dirt cheap, but you will get maybe +/- .050" (roughly +/- 1mm). Milling a hole is more expensive but you can easily hold +/-.005" (roughly +/- 0.1 mm). Then you can ream a hole and hold it to +/-.0005" (roughly +/- 0.01mm). Each different operation makes that feature roughly an order an magnitude more expensive. Not the whole part, mind you, but if you broken down what each step in the manufacturing of a part cost, each step would get more expensive by roughly 10x.

      In general (and I am speaking in very vague terms because there is so much variety out there), but holding a machined part to +/-.005" is fairly typical for the more important dimensions and the less important ones are +/-.015" or even looser. You would only ever go to super tight tolerances when you absolutely need them - like if you were press-fitting a bearing onto a hole. You need that hole (bore) to be a very tight dimension. Thats when you would be asking for the kind of tolerances that Musk is asking for ALL PARTS. His quote - if it isn’t fake - shows such a complete and utter ignorance to manufacturing it is painful to real.

      A plastic part in your car is probably made to roughly +/-.010". A steel or aluminum machined part is probably made to +/-.005". Sheetmetal would be probably +/-.015" Some dimensions within that part might be looser, and some might be tighter if they were mating with another part. Musk is asking for all dimensions on all parts be +/-.0004"

    • kersploosh
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      910 months ago

      I’ll use inches since I’m American.

      +/- .005 inch is a common tolerance when cutting metal with mills and lathes. Also for milling circuit boards as you mentioned. You can get +/- .001 inch if you really have to, but you’ll pay for it.

      EDM and precision grinding can get you +/- .0005 on small metal parts.

      Bending operations in sheet metal are more like .010 or .015 per bend. So if you have 3 bends between screw holes A and B then their relative positions might vary by +/- .045 inches.

      With big parts you tend to need larger tolerances, though the parts also flex significantly. You can use the flex to your advantage by designing clever alignment features that make the part deform to fit. Plastic car body panels do this.

      I hope Elon is just using a bit of hyperbole to try to motivate his engineers. If he is being sincere then he’s delusional.

    • @Jumi
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      110 months ago

      I only find German stuff but if you search for “ISO 2768” you’ll find a chart of general tolerances which are used most of the times.