super cheap, mini valves?

Is it possible to get a TINY, cheap electric valve?  The idea is for a 3D printer that uses a huge array of tiny needles, each of which acts as an extruder, to 3D print stuff in seconds instead of hours.  My question is, could I use a tiny valve over each needle to allow or stop plastic? or would that be impractical/impossible?

I'm fairly sure you can get .030" and smaller pipe, which you could extend out to an array of injectors. I don't think using compressed air would do it, you'd need something that'll put a fixed volume through the pipe, perhaps something similar to fuel injectors could work. You'd have to keep the entire assembly from the reservoir to nearly the ends of the needles hot, probably in a temperature controlled box, and you'll need to find a material that you can get to a very low viscosity in order for it to work.

Perhaps a better solution would be to put the needles spaced 1/4" or so apart so you can get a more practical extruder on them, then step the whole array around 1/32" at a time to get the resolution and allow some cooling time.

IIRC, inkjet printers use small resistors in the print head to repeatedly flash boil the ink to force a regular stream of droplets out at high speed. The ink droplets are charged as they leave the print head, and accurately directed to the correct position by a changing a magnetic field around the path of the droplets.

That may work for a 3D printer, if you can find a high pressure injector to throw out drops of molten plastic, although you'd probably need a pretty substantial magnetic field to alter the path of a heavy drop of molten plastic enough, assuming you can get a charge on it.
jduffy54 (author)  The Skinnerz4 years ago
The idea of the compressed air was that instead of forcing plastic through the mini valves, but still move the plastic through without any kind of plunger, or gazillions of steppers. The whole idea was that this type of printer could (theoretically) print out tens or hundreds of objects an hour, without any physical alterations between different designs (like an injection molder or other manufacturing devices would need). Sort of a middle ground between the versatility of a 3d printer and the speed of a molder. I suppose the idea with spaced needles in 2 dimensions could work and quickly, but it still brings up the original issue of making many extruders that are tiny and cheap, as well as a method of delivering the plastic.
It's a good idea, but you'd need a vast number of extruders and valves, all of which would have to be extremely small to attain a reasonable resolution. Also, you'd have a real problem trying to keep whatever you're material printing with molten and at a fairly uniform temperature without anything jamming up. Don't forget, you need the give the material time to cool and solidify before printing the next layer, which will limit your print speed.

I think that you could fairly easily use multiple extruders to print different sections at the same time, providing the item is reasonably large, especially if you can get the extruders fairly compact so that they don't interfere with each other too much.

Alternatively, you may be able to direct a reasonable number of extruders so that they print a row of points so that you can scan over the item printing a stripe at a time the same way as a normal printer prints an image.

However, these are only really practical for high volume work, and it would probably be a better investment to get a faster 3D printer, or one using a different technology.
jduffy54 (author)  The Skinnerz4 years ago
the point is that the valves are placed directly over the needles, and each needle is prefilled with plastic. Then the whole block is heated so the plastic melts, and air pressure applied above. Once the needles run out, they're refilled by another pressure block, except with molten plastic at the bottom, and the valves removed. I did get the idea from a modern printer, and I was also wondering if anyone knows how they get the ink to only fall from the specific points, without large valves and pressure. Finially, I wasn't looking for a super high resolution, or large print area. Maybe just 1"x1"x3" or so, at maybe 1/32" or 1/64" resolution. 32 would need 900 such neeles, which is the main drawback.