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
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
LOL
Yeah ok.
Tell me you know nothing about manufacturing, without telling me you know nothing about manufacturing.
That one quote - assuming it is accurate - explains that Musk is even more of an idiot than everyone already knew he was. You don’t make things at those tight tolerances. A couple of dimensions on a part might be (for instance the bore on a press fit sleeve), but you’d almost never, ever hold an entire part to that tight of a tolerance.
In imperial units, 10 microns is .00039". A human hair is roughly .001 to .005" thick. So he is asking for a tolerance that is 3 to 10x smaller than the thickness of a human hair. To put the absurdity of Musk’s demand into perspective, most parts that go into a car are roughly an order of magnitude looser in tolerance with some dimensions being 2 orders of magnitude looser.
That difference might not sound like a lot, but holding something to +/-.0039 versus +/-.00039" could easily triple the price of an item or more. Easy. You use a tight tolerance only when you need to - that’s engineering 101. Some parts could easily be +/- .039" and not affect their performance on bit. Close tolerance engine parts might be held at what Musk is demanding, but never “ALL PARTS” would be held to that.
I work in semiconductor industry where machines need to have sub-micron positioning accuracy and even we don’t generally design parts with 10 micron tolerances, unless it really needs to.
Not to mention the fact all the tolerances should have been determined before mass production began. You determine the dimensional requirements and develop the manufacturing process to deliver that.
There is absolutely no way they have the systems and tools in place to properly measure every part with sub 10-micron accuracy and precision either. To control those dimensions you need to go a whole additional order of magnitude out. I pity the fool that has to manage that control plan.
I’ve told many (usually new) design engineers that they’re stupid for asking for 0.001" tolerance on parts when they only need 0.005 “or 0.010”. The difference between 0.010" and sub-10 micron is easily a factor of 100 in most parts, ESPECIALLY when you’re talking larger steel components like panels on a freaking car.
Unless you are talking about a press fit location or some kind of high precision alignment issue, almost nothing needs anything tighter than .001" and .005 or .010" is perfectly fine for most things. I work with a lot of weldments so if we’re within .030" we consider that good enough.
+/- .030 good enough for most skin panels on airplanes.
not just that, he said “all parts”. The stitching on the seats, the floor carpets, USB ports, cupholders and the A/C vents have to be more accurate than the width of a human hair too
When I was young I got a job at a manufacturing place that made all sorts of parts for sensitive equipment. Younger people, or people with steady hands would debur and smooth. We would have these huge magnifiers and friggin microscopes and be working with what looked like a really long tiny exacto knives that needed to be replaced every 5 minutes or a couple dozen uses to get that stuff to spec. You can spend 20 minutes on a piece, think it’s perfect and then QC would send it right back because they somehow found some tiny inconsistency or groove you didn’t or couldn’t notice.
There is no way you can expect that level of accuracy, unless your willing to pay for clean room level stuff. Even we weren’t always quite that accurate depending on the end use and they charged like almost $50 for something that looked quite like something you get a hardware store for 50 cents.
Probably an optical comparator.
As someone who knows almost nothing about the topic, wouldn’t some (most?) of these parts be big enough that a small change in temperature or air pressure alone would cause these parts to expand/shrink enough to go over the tolerance limit?
Yes, and different materials will have different rates of thermal expansion. That’s probably why the pixel 7 camera glass was cracking for no apparent reason when winter hit. Imagine coming out in the morning and finding all the glass in your car shattered because it got cold overnight. Or even worse you take it out of a heated garage on a cold day and the glass shatters while you’re driving.
We compensate for thermal expansion. The standard temperature things are measured at is 68F/20C. So if it’s 72 degrees we’ll compensate it back to 68 in software for the material we’re measuring. We use scale bars of known length and similar material type to verify scale. (I run laser trackers and laser radars.)
For measurement equipment that’s stationary, like CMMs, you just control the environment.
No customer would ever pay for that accuracy on all parts.
No customer would NEED that accuracy on all parts. Just shows what kind of clown Elon is.
hah historically Teslas body panels are closer to +/- .39"
Just coming in to say you are completely and absolutely correct. 🍻
I don’t see anywhere in the article where Musk says “tolerance”. He specifically says “accuracy” and goes on the talk about listing more decimal places instead of rounding. Any mention of tolerance is done by the author of the article. If certain dimensions are not naturally rounded to one, or even two decimals, there is no reason not to list it to three or more on modern drawings. GD&T can specify whatever tolerance is necessary without relying on a decimal-based block tolerance. I’d be interested in seeing the original email but it seems like there is a misunderstanding by the author given the context being discussed.
I default to three decimal places for all my basic dimensions on both in and mm drawings. One of the benefits of GD&T is that you can give provide additional dimensional accuracy, completely independent of the tolerance being specified.
Engine parts? Tesla’s don’t have engines, they have electric motors which shouldn’t need this level of precision. Electric motors they have today work pretty well already.