Re: 3D printing, powder spreading

Graham -

Yup, it really is a roller, and you guessed it right, it is spinning
(for the case of most of the line of printers), in a counter clockwise
direction, and "snowplows" the powder up (G&P Stainless, about 7/8"
dia and sounds like 200 RPM). It works remarkably well. The build
platform (right-hand bin) lowers approx 0.035" - 0.05" per layer,
depending on the powder type, and the feed bin (left side) raises a
touch more usually around 0.075" (that's an inferred number, not
actually measured). The most important part of that setup is the
overflow drop chute on the far right-hand side of the build bin...any
"extra" powder gets dropped into a catch for reuse.

The "particular" 3DP printers I am familiar with use a lot of embedded
computing power in the printer to slice and print. My proto/hobby
version uses a recycled USB inkjet printer with the work being done by
Rhino and ArchCut (was Materialize RP, but I can't justify the cost
for this project) that generates a series of b/w solid JPEGS, that are
then streamed to the printer....the end of travel triggers paper out
and then the Z-increment functionality and powder reset. Why someone
hadn't put this type of control to market is beyond me - it would
essentially make an RP printer (despite how messy the powder gets) for
every desktop, probably for less than $1000...instead of $18,000....

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Graham Stabler" <grezmos@...>
wrote:

>
>
> In a printer like the ones made by zcorp:
>
> http://www.zcorp.com/
>
> They have two vats with motorized pistons, one in which the powder to
> be used it stored and one in which the model is built, as the model is
> built its platform sinks and the powder hopper rises. The powder is
> then transfered from one side of the platform to the next.
>
> A video is worth 10million words:
>
> http://www.youtube.com/watch?v=lDNLk7XvhRc
>
> Pause it, let it download and then skip to 5:21
>
> I don't understand a word they are saying but its the best video I can
> find.
>
> Someone in the past said a roller moved the powder, that can't be the
> case it just wouldn't work, it would compress but not move, however
> there is a roller but I THINK it is spinning quickly in the opposite
> direction, its a bit hard to say so I'm guessing a squeegy pushes the
> powder and the roller makes sure it is level by flicking off the very
> top layer. Notice that the build area lowers a little before the
> printing so the roller does not catch it and also that the roller
> reverse direction and spins off the excess at the end of travel.
>
> Can anyone confirm this or does anyone have any ideas?
>
> Cheers,
>
> Graham
>