Just curious, not to go all-in on the "fake news" stuff, but does anyone take this article or this entire site seriously and if so, why? The "author" is a fake persona using a photograph from a hair salon advertisement as their avatar. All of the photos are from Tesla's own materials. The lead photo is from their Q2 investor letter, and it depicts a machine in China, not California. The site is just weird clickbait and, if not deliberately misleading, at least seems to lack any reason to exist.
This article from the SAE (you know, the industry group of car building) is way more interesting.
For everyone concerned about repairs-- this isn't exactly a new concept.
The BMW i3 has a carbon fiber frame that, as far as I know, they do not sell in sections (https://www.cnet.com/roadshow/news/crash-your-carbon-fiber-i...). This means during an accident, the damaged portion is cut out and a new section is glued in, though the repair would likely involve purchasing an entirely new frame unless the shop has one leftover from a previous repair.
With the Y, it'd be the same thing-- the shop would either have a spare, partial casting from a previous repair or need to order a new one, and it would be cut and welded into place.
The repair itself shouldn't be any more difficult than any other car, it's just purchasing the part that becomes more expensive if you have to purchase a new entire casting for damage in one area of the car. That, however, is entirely fixable through some clever supply chain fixes and may be something Tesla can support through savings on the single casting.
From my experience, if the frame of the vehicle is functionally damaged then the car often totaled anyway. Maybe that is not true for expensive cars like the Model Y.
Tesla parts are actually really valuable. A lot of people want their engines (and batteries) for hot rod projects, and there are very few around. They can't be bought new, and the used price is probably higher than new would be.
I heard some irrational sounding numbers a few years back. Maybe prices have come down, now that more Teslas have had the opportunity to be totalled and sold for parts.
If you have a project car that really wants a tesla engine.. the car wants what the car wants. I wouldn't be surprised if some number of Teslas have been bought new to scrap.
JFC we really need to turn this societal acceptance of "you don't own the hardware" around.
It's always been legal to sell parts off your car. Do not buy anything that attempts to prevent you from owning what you bought through any sort of user agreement.
My understanding is you can't go to a junkyard and bring a Tesla back to life, cause they own the software. Course wonder if someone determined enough could make it work at minimal like a normal car (no self-driving). Reversing the firmware is probably a bit of effort though (I don't think reversing anything is ever truly impossible).
I've done that sort of work on a late model Daihatsu. You will need access to a frame pulling setup if the damage is extensive enough, you'll need the exact measurements from the manufacturer, a lot of time and very good measuring and metalworking skills but it can definitely be done. Fabricating new structural members from plain automotive sheet steel is a study in patience.
The car I did this to was totaled in Belgium, bought for the scrap value and repaired on a very small budget. It is still driving the streets of Bucharest today. The MOT inspectors could not find proof that the car had been worked on, which I took as a badge of honor until they went off on a tangent that therefore it must be a stolen re-id'd car. Then I showed them the step-by-step pictures and it was all good. Fun job!
They are not going to weld castings except maybe for very small cracks and even then it's very unlikely. The casting is not in a place that could be repaired if it were steel, though. It's the main structural member, located behind the rear seats. If you needed to weld there you'd need to take the car practically down to its frame.
Even if it were in a place that was accessible and subject to repairable damage, you would not see it welded or cut. First off a lot of it isn't physically possible to weld; it's in very deep (6") pockets and you'd have a huge amount of difficulty getting penetration. Second, welding aluminum is not super easy. Anyone can weld steel, aluminum isn't the worst but it is much trickier. Third, aluminum welds create a weakness in the aluminum around the weld, because it gets hot but isn't properly tempered as it cools. It's still strong, but the loss is significant- temper is responsible for ~70% of the strength of common aluminum alloys. Fourth, the weld and the surrounding area are very weak (<40% strength) for several days after the repair. It's a huge pain in the ass and you probably can't just let somebody drive off on it.
I'm sure there's some cases where that might be true or it's not practical for other reasons (I'm not an automotive engineer or anything), but remember, the 3 has ~70 parts welded together for this same area of the car, so welds themselves are not fundamentally bad.
I dont think the main concern here is that the new part would be welded in.
When the car is in design process, each weld is carefully calculated to provide the exact binding force at the precise location. In case of accident, the car is modeled to crumble just right to absorb maximum energy without compromising cabin space, thus protecting occupants. The process of cutting out and welding in parts almost always means altering the stiffness of such bonds (and/or moving the bonds to different locations), which can be very dangerous in the event of accident
Just as the BMW i3 the Alfa Romeo 4C also has a carbon fiber monocoque: https://www.toraytac.com/media/story/XkKY/Alfa-Romeo-4C-Mono.... And Alfa Romeo has published a 162 page manual for bodyshops on how to do repairs. The PDF is out there in the internet for people that want to know the technical details.
From the internet: "assuming your joint is designed properly and you have an experienced welder performing the work, your welded joint will be as strong as the base materials it is joining."
Welds are key to most bicycle frames and they are not known as the part that's likely to fail.
The "weld is stronger than the base metal" argument is often repeated on the internet, but it's overly simplistic. Welded joints don't usually fail at the seam (a.k.a the weld). Instead, they fail near the seam where the base metal has been stressed due to thermal expansion/contraction and heat treating. It is correct that when done properly, everything should be fine, but I wouldn't trust the vast majority of body shops to have access to welders who would do it "properly."
This doesn't make it any more clear whether weld repair poses a practical danger for most people in most circumstances. If it's the case that metal stress near the point of welding is the where it's more likely to fail, that still doesn't tell me how much more likely to fail. For all I know it could be the weakest part but still such a trivial difference as to pose no concern.
And the point about welders leaves a dangling, open ended implication that invites anyone reading the sentence to just go ahead and assume that poor weld jobs leading to immenent danger are happening all the time. But are they? Or is that just being noted as a hypothetical possibility? I'm having a hard time telling whether a possible or probable danger is being asserted here.
Welding is like programming. Everybody with half a brain and some skills can weld. But proper welding is an art form, and the difference between the two levels is many years of work and study.
So for most people welding like that is not in the cards, but a trained and meticulous professional can do miracles (or close to miracles). It starts to get really interesting when you start hanging stuff from your welds, for instance when building an overhead crane.
Welding is just practice, practice, practice. Like everything else.
Welding lifting rings onto stuff is not really a high bar. High quality welds are easy if the materials you're dealing with are easy. Stuff that is exotic, expensive and hard to work with is the stuff that takes real skill because it's really hard to get a ton of practice at those things (there's only so much magnesium alloy that needs welded) so you need a lot of skill and experience in varied circumstances to do a high quality job from the get go.
I can weld and I can dick around in a bash shell but I'm much better at the one that is my current day job that I do for ~40hr a week.
You only know how good your welds are once you've seen them destructively tested. What looks good may not be all that good. A really good welder will be able lay bead after bead after bead with very consistent quality and material characteristics.
It's hard to look at someone else's weld and know if it's good because lord knows what they did under there (if it's externally bad there's some pretty obvious signs). It's easy to lay a weld and know that it's good from a combination of how you did it and how it came out. If you know what you're doing then a bend test just confirms what you already knew. X-rays keep honest welders honest.
For "easy" material combinations you can get away with a surprising amount of corner cutting and still pass a bend test. Good welds aren't hard. A community college will have you passing a bend test on an overhead weld in a semester and doing the same for pipe in two but it will all be in steel and a limited variety of consumables and processes. Those kids might be masters of 7018 but hand them some aluminum electrodes and they'll be lost. Good welds the first or nearly the first time on material + consumable combo on which you only burn say 10lb a year is what really takes practice.
The vast majority of welders do not possess the skills to properly repair an automobile frame. There's no way I'd trust a body shop to repair my car's cast frame with weld on replacement pieces.
Yep. Thermal hardening is a thing and if a weld isn't properly annealed post work then there is a good chance that it will fail right next to the weld itself. This is taken as proof that the weld is stronger than the material that's been welded but actually it is more often than not proof that the weld wasn't properly thermally treated.
Once you do that though, it is actually true, and even then you may see stress cracks next to the weld if the change in thickness is too abrupt. You need to gradually thin down or you'll get a focal point for stresses.
They are the part of the frame that fails, but they’re also at joints, which is where stress collects. I’d be interested to see failure modes for lugged (silver soldered) frames vs TIG welded vs pressed/glued or other bonded joins of tubed (no monocoque) frames.
Frames do fail at or around welds though, especially for even mildly exotic metals beyond plain low-carbon steel. I've had them break before, and it makes for a long walk home.
The single-cast is only the aluminum. Several common vehicle glues are stronger than aluminum (e.g. Steel Reinforced Epoxy), and aluminum itself is not very strong.
The safety critical structural elements of their cars are a mixture of mild and high strength steel[0].
Which is certainly a safety critical structural element.
Additionally, glues are not stronger than aluminum. I don't know if you're thinking of a composite resin (eg glass fiber), but normal adhesives are weaker even than pure aluminum, which is ~5x weaker than all the commonly used (copper age-hardening) alloys of aluminum.
I have no interest in a pointless debate about the semantic difference between the passenger compartment Vs rear crumble zone and what "safety critical" means, no do I over the word "common" in "common vehicle glues."
If you're going to read my post with the worst possible interpretation then try to correct that uncharitable reading, I just have no interest in a discussion.
So basically you didn't look at the link, because the castings -which, again, are new- are part of the safety cell. They are not the rear extruded rails.
If you had specified an adhesive when you first wrote the comment, sorry- I managed to not see it. I don't know of any "steel reinforced epoxy" besides JB weld (which generally should not be used on anything bigger than a lawnmower), but it and actual 3M vehicle adhesives[1] are a full 10x weaker in shear and 15-20x weaker in tension that plain boring 6061.
The point is: "We're moving to an aluminum casting instead of a series of stamped pieces. We'll go from 70 parts to 4, then 1 with a reduction in weight, improvement in [NVH], reduction in cost, and a significant drop in capital expenditure for all the robots that used to put 70 parts together."
The single casting for the Y is for cost an NVH reduction per the article & Elon. My early production Y has 4 pieces for the rear instead of the single one this new machine will produce, but it shouldn't be any structurally less sound
From experience - i3 frame means that during even small accident car gets totalled, as stress is moving across whole component and you have to rebuild basically whole car to make it safe again.
True, but the i3 is not made of Aluminum, but composites which will have to be glued together in such way as not to compromise structural integrity. Also, the insurance will have that factored in and you should always consider it as part of the price of the car.
It's exciting, and at the same time it makes clear that even small accidents may cause a complete write off of the vehicle due to the unrepairability of cars manufactured with this technique.
We don't know much about the construction of the Cybertruck. But one would assume that the center part of the body gives the structural integrety, while the outer parts are the crash and crumple zones. This should make the Cybertruck repairable, especially as it is just steel and no aluminium involved.
It is disappointing that Tesla uses much of its engineering prowess to design products that are inherently difficult for owners or small shops to modify, maintain, or repair. Taken directly from Apple's playbook.
Apple didn't do it to prevent repair, but because you can build a better product by making things non-standard, closer fitting, single piece machined, etc.
Tesla is probably doing the same.
Remember a good number of repairs Tesla will end up paying for - through various warranty schemes - so they care about repairability too, just to a lesser extent than they care about product performance and cost.
They are now in the insurance business and Musk has already stated this will drive them to produce cars that can be repaired more cheaply. I cited his statement on the earnings call elsewhere in this thread.
The reduction in size/complexity at Tesla/Apple scale may actually be an overall benefit.
Thought experiment: Imagine that the overall material required is cut by 10-20% by tons of optimizations and reductions. That means the supply chain and associated energy/costs vanish. If you have a failure rate of less than that (probably much less) scrapping is likely still better.
I'm talking about every optimization that reduces repairability. While I'd prefer to be able to fix things, just producing and shipping a whole new unit to a small subset may be less wasteful overall (at that scale) than designing for repairability.
> "Tesla uses much of its engineering prowess to design products that are inherently difficult for owners or small shops to modify, maintain, or repair."
Teslas (especially the Model 3 and Y) are not inherently difficult to repair. The problem is that Tesla's restrictive policies make it difficult for individuals to access the documentation and parts to do so.
You need to understand Elon to understand that. He talks ton about sustainability. But what he means by that, is sustaining lifestyle of rich people, while feeling good about themselves.
He's actively against public transport (which is by far most ecological), pursuing dreams of living on Mars (which is unpractical on so many levels, that if it'll be ever complete, it'll be trip of lifetime to fifthly rich people), building expensive toy cars (car that does 0-60 in less than 6s? who would even want that?) and many more.
Sure, body-on-frame cars (before the early 1960s) were easy to weld back into shape.
With unibody cars, that doesn't work anymore. Body shops have frame racks to pull steel cars back into shape. That works if the car isn't too bent and your standards aren't too high.
Aluminum unibodies don't respond well to bending so yes... If the frame is tweaked enough to screw up the wheel track, that's probably the end of the car. Maybe find a flood car with a good frame and swap everything over. This is true whether the car's body is a single casting or built up by welding 70 pieces together.
Insurance companies frequently “write off” cars with major damage that would cost more (or nearly) to repair. They generally don’t scrap them, but then sell them at salvage auctions. They are then bought and repaired by people/companies who specialize in fixing up salvage title vehicles. They are then resold (with a salvage title)...generally you should try to avoid anything with a salvage title as they tend to be fixed as cheaply as humanly possible in order to turn a profit.
What mechanics do and what insurers pay for are orthogonal.
It's not unusual for mechanics to buy newly totaled cars at their salvage value as a convenient exit to the owner, and either rebuild the vehicle or part it out as a side hustle. A repaired salvage vehicle is eligible for a rebuilt title in some states.
We'll see. It makes doing salvage titles a lot easier if you can harvest one good frame casting and then pull from a bunch of other vehicles the other needed parts.
It is also an open question on what it would cost to make this casting as a repair part.
Agreed. Sounds like the Lotus Elise, where if the extruded/bonded aluminum chassis is damaged, the repair procedure is basically "remove everything from the chassis and swap it to a new chassis."
I am fascinated by their attempts to simplify manufacturing but this does bring up the question, how easy is it to change what this casting machine produces? Will they make similar changes to the 3? One question is will the heat pump design make its way to the 3 or are changes to the 3 just on hold.
I am curious how long they will go without changing the outward design of the 3 or Y. Most manufacturers find it necessary to iterate every few years to keep customers interested and show progress while Tesla shows progress mostly through features added OTA. They already have range numbers down for a significant lead covering a few years so they are not under the same pressure.
edit: This all goes back to Musk's question to engineers why can't a car be in as few pieces as possible using a matchbox/hot wheels car as example
Since they are now in the insurance business as well they will soon figure this out. Even was mentioned at the last conference call, they’ve admitted to making a lot of mistakes in the past about manufacturing for repairability.
The transcript is not great but you get the point:
“ It's like if you want to pay more for insurance, you can. But if you want to pay less, then please don't drive so crazy. Then people can make a choice. Like, OK, they want to drive aggressively.
In that case, it'll be higher insurance. Or they want more capital enter driving and pay less. This was actually very helpful for us to have a feedback loop to see what is driving insurance expense. A lot of it is just -- it's like a little fender bender and the net fender bender because of the way that the body collision repair is being done.
It costs like $15,000 or something crazy and like -- and then we can actually adjust the design of the car and adjust how the repair is done to actually have the fundamental cost of solving that problem would be less.So this has helped us under a whole bunch of facility things that we were doing basically without realizing it. But this is a problem with -- in general, with insurance is like if the insurance is, like, all you can eat, then the feedback loop for improvement is sweet. So this gives us a great feedback for improvement because it's basically a fundamentally better insurance product. I'd also like to say, I'm inspired of recruiting because if there's one thing I'd like to come out of this call, it's that a lot of great people want to join Tesla.”
From my understanding, Tesla has been offered help by many major automotive manufacturers such as VW, and rejected it.
Perhaps that was foolish in hindsight, since most of their quality, workmanship and repairability problems stem directly from having to learn (through trail-and-error) all the same things the other manufactures learned long ago.
The parallels with McDonalds taking Chipotle under their wing to teach supply chain management, distribution, food safety and more are undeniable. Chipotle's founders famously scoffed at learning _anything_ from McDonalds... which may have resulted in the numerous food safety handling issues they had a few years back (not washing raw produce that was transported through multiple handling facilities and then into stores), and legendary portion control variance (totally depends who makes your burrito... it may weigh a 1/2 lb, or 2lbs... a total coin flip).
It's difficult to scale these complex organizations - why make it harder on yourself? Learn from other people's mistakes and try not to repeat them.
foisting large insurance bills onto Tesla customers because Tesla couldn't design their car to be repairable, even by Tesla themselves - doesn't seem fair either.
His response to that is probably to say that if every car were a tesla with autopilot enabled the probability of trivial accidents goes down significantly.
> how easy is it to change what this casting machine produces?
Swapping dies takes a few hours. Making new dies takes many months and costs some fraction of a million dollars.
> I am curious how long they will go without changing the outward design of the 3 or Y.
I really hope they make a car that looks different soon. Branding is just SO deeply engrained in the car industry; I think they're damaged by people considering the S and 3 basically exchangeable. They should really have different styling just to make people feel like they have more than one option in buying a Tesla. It makes the number of competing non-Tesla choices seem twice as large.
sure, but it's also full of weird gimmicky shit so who knows when it'll show up, if it gets scaled.
I'm thinking more about things like the roadster. Even for being relatively similar, the accents are all more aggressive and it creates a very distinct look that the 3XY absolutely do not. And then the most frustrating thing is that Musk clearly does not intend to make very many of them! He's treating it like an ultra halo car, when just having a convertible version of the 3 with a slightly different body would make the psychological choice to buy a Tesla far easier.
Like, people don't even have to buy it. Just by existing it would make Tesla look more competitive- it just needs to seem like an accessible choice. The roadster would be perfect, but it's too expensive and full of unnecessary shit for no reason, and that totally ruins the benefit! It epitomizes what frustrates me with Musk- a great core idea, but deeply crippled by goofy whims.
At the end of the day it’s just a very large die casting machine. To switch out the part it is casting requires making new dies. It is expensive so you don’t want to be doing that a lot, but these machines are going to be probably doing 500,000 units/year at least so it’s very worth it at that volume.
Over several conference calls they have roughly answered this. Their biggest limitation to what they want to do is engineering talent. And they want to grow really fast. So using scarce engineering talent to improve an existing process slightly is not aligned with those goals. They want all the talent building new factories and products. They do seem to still have small teams to make continuous improvements, and eventually those upgrades like the heat pump and improved body will be integrated. I think Elon guessed several years at a minimum on a call.
I think a "model S Mark 2" is in the pipeline, from what I've heard on YouTube channels.
I think the model Y is already massively simpler than the 3 is (from watching Sandy Monroe on YouTube), but whether it will be possible to perform such a modification to the 3 isn't clear. My suspicion is that there's to e much complication in that area of the car (rear suspension) to make a straight swap to the Y style of rear bodyshell section.
They will bring this manufacturing process and new rear body structure to the 3 for sure but it won’t be until they seriously ramp up Y and can afford to shut down the 3 lines for retooling. My best estimate would be no earlier than Q1 2021. They have an aggressive goal to hit 500,000 total deliveries in 2020 and they can’t afford any downtime on the 3 lines to hit that goal.
They'll also bring new manufacturing processes to their new factories. Musk said on the latest earnings call that new factories are building "better cars" with all the latest enhancements. So while Fremont might keep making "original" model 3, I think it's likely other new factories will skip straight to the new processes.
So for example the factory in Berlin will just start with a monster press like this on day 1, so all Model Y built there will automatically have the "new" design. Same for the Model 3 and Model Y lines in Texas.
Check the teardown video of the Model Y by Sandy Munroe. It clearly shows the cast parts, which now get replaced by a single large part. One can assume, that they will make similar changes to the Model 3 as soon as the cast machine exceeds the Model Y numbers, as it saves a lot of money in production.
I find hard to believe that no one has thought about this before, so it makes me wonder what are the disadvantages and if the conditions changed enough that those disadvantages are not a problem anymore.
I don't buy that the only disadvantage is the increase repair cost of the car in case if accident.
> I find hard to believe that no one has thought about this before
Automotive companies utilize a myriad of frame designs for their vehicles - each one a collection of different alloys, structural shapes and castings depending on the design goals for not only the vehicle of today, but changes that they foresee in future vehicles that would utilize the same basic BIW lines (to conserve capital expenditures, training procedures and inspection methodologies).
There are some automotive companies that rely on some cast product of various sizes in their frame designs. That is not really new.
Tesla is obviously taking some more extreme measures than other automakers, but electric vehicles do inherently put more frame design freedom on the table given that there is not an engine compartment per se to consider in terms of passenger safety.
That said, generally, the disadvantages of large castings in automotive applications are:
1. Poor reparability, and
2. Porosity risks (which can unexpectedly yield structural issues), and
3. Wide tolerances, and
4. Need for a post-cast finished machining process (application dependent), and
5. Long cycle times, and
6. Design space difficulty in managing the weight/strength tradeoff and crumble zone development (application dependent).
Keep in mind that while a casting process may seem simpler that "traditional" BIW lines, those traditional lines are highly optimized and generally very efficient and flexible (often running multiple different kind of frames over a single line) - typically employing above 95% automation. I know Tesla has struggled with their BIW lines in the past in terms of quality. I am not sure of Tesla's current situation having not really followed Tesla's process for a number of months.
The advantage, I suppose, that Tesla is seeing is that they can radically simplify their BIW line.
> I find hard to believe that no one has thought about this before
These kinds of castings are relatively new, and car companies are surprisingly unwilling to spende more than low millions on moonshot tech. It was not an insignificant gamble by Tesla.
Tesla had to do the R+D on a new alloy of aluminum to make this work. None of the carmakers do R+D on basic materials and are limited by the commercially available alloy formulas. They have been doing aluminum castings but they are much smaller than Tesla's.
> Tesla had to do the R+D on a new alloy of aluminum to make this work.
Teslas RD budget is tiny, given for much stuff they do in-house - designing cars, autopilot, seats, batteries, robots, solar panel, solar roof, and many others. Their RD is roughly on the level of Mazda, which does much less stuff in-house.
> None of the carmakers do R+D on basic materials and are limited by the commercially available alloy formulas
You really believe that companies that spend billions of dollars per year on basic materials, that are some of the most important for their products, just look at the prodcut catalogue from suppliers and order from there?
Obviously Tesla is getting a much larger bang for their R+D buck. That comes from the incredible amount of talent they are able to attract vs. legacy automakers.
That is pretty close to what they do. Modern car companies mostly do integration and final assembly along with some marketing and finance. Vertical integration in the American auto industry died with Henry Ford until Tesla revived it. You could argue that Toyota is somewhat vertically integrated with the cross holdings they have in some of their Japanese suppliers.
Obviously Tesla is getting a much larger bang for their R+D buck.
Citation needed. What has Tesla been able to accomplish with its inhouse R&D that nobody else has? Other than battery design (using cells developed and manufactured by Panasonic), pretty much everything Tesla does is subpar compared to automobile industry standards.
None of the carmakers do R+D on basic materials and are limited by the commercially available alloy formulas.
If you believe that I have a bridge to sell you...
Pretty much every traditional automaker spent more on R&D last year than Tesla made.
Carmakers have tried unibody frames in the past, and they abandoned them pretty quickly because they're expensive to repair in the event of even minor accidents. (This is also why nobody else does shell cars like the Cybertruck anymore; because any damage to the shell can cause a structural weakness that would require the entire shell be replaced to make the car legally roadworthy.)
With multi-part frames, individual parts of the frame can be made of different materials and stiffnesses based on the physics or safety requirements imposed on that part of the frame. This means that the overall frame can be both stronger and lighter. With a unibody frame, you have to use the same material through the frame, and the only way to adjust stiffness in any part is to control the amount of material used.
> None of the carmakers do R+D on basic materials and are limited by the commercially available alloy formulas.
Materials research has been constantly reducing car weight for decades, at the same time that safety was improved and production costs reduced. New aluminum and steels are developed every day.
For example, the development of high strength steels have been driven by the automotive industry. The contribution of Tesla is merely anecdotic at this point.
This is a little reminder that Tesla isn't just about battery tech/ electrification. They have a lot of engineering talent pushing most all aspects of the auto industry forward. Companies like Lucid and Rivian can nail a lot of the basics, but Tesla is pushing hard on all fronts. Likewise GM, Ford, and Chrysler are going to have trouble attracting engineering and management talent. VW, Honda, and Toyota are Tesla's big competitors. Them and perhaps on the other end of the spectrum, Chinese manufacturers who crank out tiny, super cheap cars more people can afford. Though in the US those don't seem to take hold.
Also, I'm not convinced the reason smaller cars don't come to the US is due to safety issues since they exist in Europe where there are similar safety standards.
I wonder if there are likely to be any metallurgical differences (e.g., strength, flexibility, likelihood to crack, etc.) between cast and stamped parts? My sense is that it's generally understood that 3D printing methods for metal produce weaker parts than casting, but I'm not sure how different non-3D printing methods compare.
It depends very heavily on the type of metal. Metal strength is primarily determined by the shape of the microscopic grains making up its structure. Pressing, stretching, and squeezing those grains is one way to shape them. Chemical processes are another.
Production method matters a ton in steel, where a LOT of strength comes from the way the metal was formed, and is only fully lost when the steel is near melting temperature. Alloy steels don't care so much how they were formed, but they're usually too expensive.
Aluminum is different, and cast parts can be very strong if they're heat treated properly. The most common aluminum alloys (pure aluminum is nearly useless) are made with copper. Copper causes smaller grains to form as aluminum solidifies, and then over time it precipitates out from the bulk material and ends up in the borders between grains of purer aluminum. When stress attempts to pull grains past each other, the copper atoms act like wedges and keep everything from moving.
Because the copper creates the grain shape itself, you don't need to work aluminum alloys to make them strong. Aluminum is semi-noteworthy (but far from unique) in that it loses strength very quickly when worked. You need to change a bunch of alloying elements to control for shrinkage (or at least delay until the part can be ejected from the mould), viscosity, temperature, oxygen tolerance etc. but I don't know much about all that. I know cast alloys are weaker than the strongest extruded alloys, but not by that much. There aren't problems with brittleness etc like you can get with steel.
Also note that "cast iron" is a metal in its own right, and is NOT just steel/iron that has been cast. Cast iron is the highest-carbon (1-3%) alloy of steel, and that is what makes it weak and brittle- not the fact that it's cast. That much carbon causes a bunch of ceramic and graphitic phases to form all kinds of weird (but extremely cool, metallurgically) garbage.
Neat. Do you have a link with more info about this? I guess I'm curious if they needed to switch alloys when they switched from stamping to casting, and if so, how the properties of the new material differ from the properties of the old one.
Just out of curiosity - is there an explanation of how you can handle a fender bender that happens to affect the frame? Does the entire unibody frame need to be swapped out in that case? Is this the equivalent to soldering RAM to the motherboard.
Sandy Munro (and others) have advocated larger castings for ages. Watch munrolive, autoline and other youtube podcast interviews for ongoing analysis and discussion.
The community interest in unibottle, multivalve (name?), simplified wiring harnesses, large form unicasting, and all the other deepdive innovations is really gratifying. There's been such a huge backlog and now the dam is bursting.
Whatever else I think about Tesla and Elon Musk, this really feels like a sea change.
Not sure... ensuring quality of cast parts that complicated is going to be a huge ongoing issue. Any local temperature difference or fill problem might cause the body to fail to perform when it is needed the most. Stamping from uniform material is much morw repeatable and predictable.
It already costs absurd amounts to repair a fender bender or some smartphone zombie driving into the back of a full aluminum Tesla, so if they make the whole chassis some unibody they'll just total the cars for the slightest damage?
The insurance on my brand new model 3 is around $80/mo? Not that high. On the other hand my friend who has a Lexus RX had some pretty minor damage from a fender bender and still it somehow cost $8,000 to repair so I don’t think this problem is unique to Tesla.
It's insane, it's costs nearly $100 more per-term to have full coverage on my 2018 Model 3 than it does for the same coverage on my 2015 Leaf. Outrageous!
How would it compare with a few laser sinterers? I expect the initial investment would be bigger, especially as these machines are slower, so more would be required. But then, sinterers are probably a lot more versatile, could produce the whole 70 parts plus the rivets holding them at once, or a few single replacement parts. Probably with less wasted material?
is this an assumption or is there an actual source for the original statement - just curious as all I can find is a tweet from a suspended twitter account
Sintering is much slower than casting, and unless the state of the art has improved, usually much weaker too. Also, aluminum is already highly recyclable. Tesla buys aluminum from the mill, and ships back tool cast-offs that the mill then recycles back into fresh aluminum.
So wpuld I save enough money on this new car because Tesla saved money building it, and therefore have enough money for a car insurance that would cover any damage to the frame so that this is a non-issue? Or is Tesla just passing this problem on to the consumer?
I wonder how this affects repairability and insurance costs? Steel is seemingly repair able by bending and welding, I can't imagine stamped aluminum let alone cast is ever repairable? Doesn't that make insurance insanely expensive?
This article from the SAE (you know, the industry group of car building) is way more interesting.
https://www.sae.org/news/2020/06/tesla-model-y-big-castings