driveable cobra 3d printed

https://www.youtube.com/watch?v=HXvIMRklWiM

Just thought this was really interesting on how fast this technology growing.
if you not seen this yet it is cool.
53w

What is revolutionary about a plastic car body? Do you suppose that any of those federal employees ever heard of molded fiberglass? As used in (wait for it) PRODUCTION?
The deposition has the approximate surface quality of a stack of Legos. On a frame we would call those striations "stress raisers." Like to see the pile of sandpaper that jitterbug used...

Oldwrench said:

What is revolutionary about a plastic car body? Do you suppose that any of those federal employees ever heard of molded fiberglass? As used in (wait for it) PRODUCTION?
The deposition has the approximate surface quality of a stack of Legos. On a frame we would call those striations "stress raisers." Like to see the pile of sandpaper that jitterbug used...

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With molding you can't control the pointwise composition or property of the material. With a 3D printer you can. And this is just R&D stuff anyway. The reality as we know it now and in the future is 3d printer will work multiple materials. And by then you can do really fancy stuff with multi-material composite structures you can't hope to achieve with today's techniques.

They actually addressed that issue by discussing the post processing they did to smooth out the corner features. So presumably there will not be as bad stress concentration. And even still, a lot of polymers do not respond the same way as metals or ceramics when it comes to cracks formed from stress risers.

One thing for sure though. If they are going to use a thermoplastic, then they had better thermally insulate the engine (scratch that ..... electric motor) and hot exhaust very well. Also don't wanna drive around in hot deserts. Things gonna start melting.

And that right there folks is our billion dollar toilet...

cncdumm said:

With molding you can't control the pointwise composition or property of the material.

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Not to beat a dead horse, but with fiber reinforced resins you do precisely that, by controlling the strand orientation, the number of plies in a stressed area, and the materials used in the fibers. There are at present something like 20 specific combinations of fiber materials to produce tailored properties in the finished part, which is laid up in a MOLD. Now when you can introduce something other than randomly oriented chopped strands into a 3D deposition process you might have something, but the surface quality is just not going to be as smooth as a molded part. For me, the test isn't printing something that has to be sanded down with a jitterbug, it will have to rival the strength of a carbon-fiber stabilizer on an aircraft. Until then, the process will "show tremendous promise," a description which, while it initially attracts investors to the bandwagon, has been the commercial epitaph of many a New Thing. I don't mean to be a total downer but I'm happy to let others get in on the ground floor...

Oldwrench said:

Not to beat a dead horse, but with fiber reinforced resins you do precisely that, by controlling the strand orientation, the number of plies in a stressed area, and the materials used in the fibers. There are at present something like 20 specific combinations of fiber materials to produce tailored properties in the finished part, which is laid up in a MOLD. Now when you can introduce something other than randomly oriented chopped strands into a 3D deposition process you might have something, but the surface quality is just not going to be as smooth as a molded part. For me, the test isn't printing something that has to be sanded down with a jitterbug, it will have to rival the strength of a carbon-fiber stabilizer on an aircraft. Until then, the process will "show tremendous promise," a description which, while it initially attracts investors to the bandwagon, has been the commercial epitaph of many a New Thing. I don't mean to be a total downer but I'm happy to let others get in on the ground floor...

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You can but not to the kind of "point-wise" control that you can with a 3D printer that deposits something at a specific location. With composites using fiber sheets and strands nowadays, that still pretty macro.

Didn't you watch the video. They kinda addressed that. Instead of sanding down the square corners, they filled it with a material instead. They ended up with smooth surfaces too. The 3D printer only really printed the rough 3D shape and the final surface is finished by fillers and sanded down. The end product was a smooth surface with no rough edge.

Plus.. its one heck of a lot faster on a 3D printer than to make composite structures on molds? Even if you have those super specialized and expensive fiber layering machines used in the aerospace industry, its still slow as heck and requires assembly. 3D printers can be faster and probably doesn't require assembly if the part was designed that way.

Oldwrench said:

Not to beat a dead horse, but with fiber reinforced resins you do precisely that, by controlling the strand orientation, the number of plies in a stressed area, and the materials used in the fibers. There are at present something like 20 specific combinations of fiber materials to produce tailored properties in the finished part, which is laid up in a MOLD. Now when you can introduce something other than randomly oriented chopped strands into a 3D deposition process you might have something, but the surface quality is just not going to be as smooth as a molded part. For me, the test isn't printing something that has to be sanded down with a jitterbug, it will have to rival the strength of a carbon-fiber stabilizer on an aircraft. Until then, the process will "show tremendous promise," a description which, while it initially attracts investors to the bandwagon, has been the commercial epitaph of many a New Thing. I don't mean to be a total downer but I'm happy to let others get in on the ground floor...

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This is being done now. The MarkForged printer does this, embedding continuous, oriented, kevlar or carbon fibers when and where needed in an FDM process. I would say it is a primitive capability at this point, but there is no reason it cannot be improved upon and it will be. This has the promise of making better than currently molded parts, because current technology relies on weak matrix materials like epoxies. Almost any thermoplastic is stronger, and some are an order of magnitude stronger. A few parts are made with continuous fiber and thermoplastics today by injection molding, but the process is very difficult. The resulting parts are strong, tough, and fatigue resistant.

swarf_rat said:

This is being done now. The MarkForged printer does this, embedding continuous, oriented, kevlar or carbon fibers when and where needed in an FDM process. I would say it is a primitive capability at this point, but there is no reason it cannot be improved upon and it will be. This has the promise of making better than currently molded parts, because current technology relies on weak matrix materials like epoxies. Almost any thermoplastic is stronger, and some are an order of magnitude stronger. A few parts are made with continuous fiber and thermoplastics today by injection molding, but the process is very difficult. The resulting parts are strong, tough, and fatigue resistant.

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That's what it will take to develop into a viable alternative to molding. However, my point (perhaps not well stated) is simply that the production speed of deposition methods is two orders of magnitude slower than injection molding, and certainly no faster than hand layup when the object is a car body--especially when you consider the staggering amount of secondary handwork necessary to fill in the low spots (or sand off the high spots; pick one) of the deposited surface.

Deposition processes are inherently suited to creating undercut or re-entrant shapes that are otherwise impossible to mold or cast, and for that they represent a huge technical advance. It makes a lot less sense to use that technique to produce large flat or gently contoured surfaces, in an effort to replace production methods which have been perfected for over half a century. I'm not saying it's impossible, just that it seems like a misapplication of the process--kind of like painting the side of a house with a lettering brush.

Thars not the point made here though. First the technology is still in its infancy. So its not fair to judge mature tech with future tech.

Second what job will it replace? You're comparing the mass production side with the single serial process production side. With injection molding, there are two steps. Making the mold, and using the mold for mass production. You make the mold currently on a CNC machine. This is a serial process. This is slow, just like a 3D printer. Then there is mass production using the mold. This is faster. You were comparing mass production with injection molds with 3d printing single parts. They are saying, 3D printers can be used to make the mold. Don't get me wrong, 3D printers can print individual parts too, but it can also make the mold. So if its job is to make the mold its no different to a CNC machine. The advantage now is a 3D printer makes molds much more effectively a potentially faster than a material removal process.

3D printers can also print the actual part itself to control pointwise composition. 3D printing simply is a superior philosophy for manufacturing things, once the technologies get improved. Taking a big chunk of material and knocking stuff off to create parts is really caveman style compared to precise bottoms up manufacturing of a 3D printer with pointwise composition control.

And then Ford came up with something which allows proper metal panels to be created -

Video: Ford unveils rapid prototyping for sheet metal parts | Mac's Motor City Garage

I'll have my Cobra panels in Aluminium please Sir!
;-)