Friday, August 12, 2005


Powder-based RP technology

This is probably not a new idea, but I haven't been able to find it anywhere, so I'm putting it up here.

All the powder-fusing/gluing RP machines that I have seen (Z-Corp, SLS etc) build in a powder that is held above a piston in a tube. This is all very well, but can be mechanically complicated. It also means you have to fill the entire volume to whatever depth you want no matter how small the part you're building is.

Why not have the RP machine make its own tube as it goes? Just have a descending platform and a mechanism to wipe powder flat over (part of) the width of it. Then build your part and at the same time build a dam round it to contain the powder. Excess powder would fall at the sides for recycling. The dam may have to have a slight draft angle, getting smaller as it gets higher, for this to work.

You get the big advantage of being able to build small objects without laying out a full volume of powder.

Yes - the system you describe is the standard one that's used for almost all these types of machine. All I was proposing was getting rid of the wells...
It might need a lot of wall material, and that would inevitably be contaminated with the powder.

Vik :v)
A sizeable portion of your finished work would be a throw-away part, though. Would the dam be recyclable?
No - probably not. But with a conventional machine often some of the powder is not re-usable anyway. It's a balance of costs, and it comes into its own when you want to make a one-off of a small object, something that's trivial with an FDM machine, but a real pain with a powder machine.
As far as I know the plaster powder of Z printers is very well recyclable over and over again and rather cheap as well. Of course these printers are able to build a dam around your tiny object, but the simple method of depositing a new layer of powder would still deposit just as much outside the dam as it does now. Depositing only inside the dam would really complicate this process
I have a sketch design for a powder deposition system that would be able to dump powder in any sized rectangle at any position, then smooth it flat with (say) a wiper blade from a car windscreen. The design isn't that complicated. I'll blog it here as soon as I have worked out the details. (Most of it should be possible to make with RP, of course.)
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