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Tesla's Carmaking 'Breakthrough' Also Comes With Plenty Of Downsides

In theory, casting an entire underbody in one piece could be revolutionary.

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Tesla Model Y
Photo: Tesla

After previously announcing that it would be able to cast the front and rear subsections of the Model Y in a move to cut costs and reduce complexity a couple of years ago, it sounds like Tesla is close to another engineering breakthrough. Five people recently spoke with Reuters, claiming Tesla will soon be able to cast essentially the entire underbody in one piece. Theoretically, that would allow Tesla to develop a new vehicle in two years or less and cut costs even further, allowing it to actually sell that elusive $25,000 electric car we’ve been promised.

Terry Woychowski, president of the engineering company Caresoft Global and former General Motors employee, told Reuters that if Tesla could actually pull it off, it would be a huge deal. But even he wasn’t exactly quick to predict a rapid Tesla victory over legacy automakers.


“It is an enabler on steroids. It has a huge implication for the industry, but it’s a very challenging task,” he told Reuters. “Castings are very hard to do, especially the bigger and the more complicated.”

To be fair to Tesla, it does sound like it’s made a number of breakthroughs. One downside to casting large pieces is that making changes to the test mold can be incredibly expensive. Smaller tweaks can reportedly easily cost $100,000, while redoing a mold could be more like $1.5 million. Considering it regularly takes several changes to get a design right, you’re spending a whole lot of money before you’ve even started production. But Tesla found a company that uses sand to 3D-print molds.


One source told Reuters that using these sand-based molds would likely cost about three percent of the total cost of creating a traditional mold even with multiple tweaks. It could also speed up the process, cutting the time it takes to get the molds right from six months or a year to just a couple of months.

As great as that sounds, though, there’s also a downside. To cast these underbodies quickly, Tesla would need to use more powerful presses that are too strong for the sand-based molds. Alternatively, they could take a slower approach with less powerful presses that create higher-quality castings but can’t be done as quickly.

Assuming it all works, though, there’s another downside that we’ve already covered. Casting the underbody in one piece also essentially makes the car impossible to repair if it gets into a wreck. So you may be able to buy a $25,000 Tesla, but if you crash, you’ll probably have to go out and buy another $25,000 Tesla to replace it. And we can’t imagine insurance companies are going to be happy about that, so prepare to pay higher monthly premiums.


There’s also the risk of cracks forming in the metal, which Tesla previously claimed to have solved by creating a super special aluminum alloy that wouldn’t have that problem. Except, as at least one Model Y owner has already found out, that isn’t necessarily the case.

Now, it’s entirely possible that the photos shown above are the only example of cracks forming during manufacturing, and that owner just got unlucky. And it’s also entirely possible that Tesla has been able to tweak the alloy it plans to use to cast the underbody as one piece to ensure that doesn’t happen. But that doesn’t mean there isn’t real reason to be concerned here.


If Tesla can pull the whole thing off and do it correctly, it’ll be seriously impressive. But at the same time, it’s far too early to say that Tesla has revolutionized auto manufacturing — and also a little too early to start questioning why legacy automakers aren’t following Tesla’s lead. With so many challenges, risks and upfront costs, it’s no wonder they’re not exactly rushing to beat Tesla to the punch.