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.
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.
Comments:
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I am not familiar with the systems you mentioned, we use a Z-printer. It uses two wells, one for printing on and the other as a reserve of powder, both have automatic bottom plates. After the print head finishes a layer the well plate in the printing area drops down a slight amount and the well plate in the powder reserve raises up the same amount. Then a strike off bar runs across the top starting with the reserve well. The result is a smooth surface for the print heads next layer. After you finish your part and allow for drying time, you simply pull the part out and reset the system. I dont know if the system transfers the powder back to the reserve well or if that is done by hand. The printing of a well wall at the same time would only save you from transfering the power back to the reserve, hardly seems worth the problems in recycling the well material.
Mike
Mike
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)
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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