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0 pointsMunkum8y ago0 comments

The body on an electric car is basically no different to an ICE car. The floor is flatter and thicker to accommodate the battery pack and no need for a tunnel to accommodate the drive train, but other than that they're about the same.

Tesla will almost certainly be using a combination of materials on the model 3; mild steels (cheap and cheerful, easy to press), aluminium (lightweight) and boron steels (strong). To join these materials you need a variety of techniques including resistance spot welding, aluminium RSW (altogether more difficult than steel because of the low melting point and high conductivity, and the fact that weld spatter sticks to the tip of the gun), riveting (for steel-Al joints), structural adhesives, flow drill screws, laser welds etc. All of these processes take serious time to calibrate and get right, and some are not all that robust (by high volume standards).

There are many quality loops with a vehicle launch. The tooling needs to be proven out. Tools get shimmed relentlessly to make up for panel variations - panel quality can vary from batch to batch within a press run. This is especially true for mixed material cars.

Believe me, these are not easy problems to solve and nothing I've seen and heard out of Tesla makes me think they've addressed any of these issues.

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4 comments · 1 top-level

sqeaky8y ago· 3 in thread

Is it possible that Musk has solved the problem, much like he or his employees have solved countless other tech problems, but Musk also knows what makes a sexy headline. Spot welding is hard to sell as flashy and new. If you can't do it on mars, it might not make good headlines.

scott_karana8y ago

If Musk solved the problem, they'd be producing the Model S faster already. ;)

csours8y ago

Spot welding isn't hard, and wasn't claimed to be hard. Mixed Materials welding and joining is Hard (steel + aluminium/mild steel + high strength steel/ etc).

MunkumOP8y ago

It isn't even that it's hard. I mean, it's been done before, many times. But there are processes here with a stack of key control parameters that can and will drift.

Panels will not be consistent - they never are (and you'd be surprised at the variation). Rivets will tumble in feed tubes or get trapped in escapements. Vision systems will get confused by ambient light or reflections at certain times of day. Weld spatter will accumulate on tips, and frequent tip dressing will change weld parameters (timing, pressure, current etc). Adhesives will be effected by temperature, humidity. Batches of sealer might not be consistent. Weld timers will fail. Power supplies will fail. Flow drill screws will deform, go off centre and be a bitch to get right. Laser welder lens will accumulate weld crud. People will mis-load parts. PIA bits will come in below the required quality. Tools will get shimmed wrong. Robots will be badly programmed.

All of this stuff will take time to get right. It isn't impossible, but it is very difficult to get a line performing reliably. Tesla will be integrating a lot of new technologies, and at volumes that they are not used to, in an area with no serious history of car building, in a high wage state. I doubt they can get the people to manage the line and maintain this equipment.

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