A basic structure and mechansim Re: 3D printing, powder spreading

Hey guys - guess what...there is nothing in between the roller and the
printhead. Regular preventative maintenance on the unit requires going
in and getting all the excess powder (now fully saturated and caked
with lubricating oil - yummy!) off the ways, the printhead, the back
of the traveller, the slide pads, the snowplow, the carwash (that's a
different article), the rest of the printer....and the BOTTOM OF THE
PRINTHEAD! Yup. There is nothing to prevent the printhead from
crashing into a mountain of powder (which I have done) or the build
plate if it's too high (which I've also done).

There is nothing but gravity to help get the excess powder down the
reclaim chute. In fact, you can even see clouds come back up during
printing, and the dump bin is a good 16" below the chute entrance.
Some creative types have put a baffle in the chute to minimize this,
which apparently works well (I don't have one) - that said, there is a
reason that ZCorp has a lid on the unit. The printer I have came with
a preheater assembly, which aside from the benefit of the heat, does
provide a bit of positive pressure inside the box, so the clouds
aren't that bad, in comparison to another friend's unit (one of the
very first) that clouds so much it can obscure the view of the print
job.... ZCorp has done a good job of adopting user's suggestions and
improving subsequent revisions of the printers.

Oh, the carwash? That's where the printer head parks to get the jets
wiped off. Most inkjets have them stashed to the side as a little
sponge, and the carriage just slides in. On the ZCorp, it's off in
it's own little corner, so the "car" drives up...gets clean...drives
out....cute.

The prior layer is just a bit tacky, so it does "grab" a bit of powder
along the way - I see this most often with the corn starch (coarser
medium) where it will "ball up" around the leading edge of a solid
area. The paster is a finer powder so my tired eyes don't notice it...

Ted.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ballendo" <ballendo@...> wrote:
>
> Graham,
>
> Agreed. I immediately noticed the LACK of a backwall on the overflow
> hole... So I figured there must be a deflector hidden/obscured by
> the machine structure due to our video vantage point.
>
> And it seems that the previous layer does atleast some "wetting" of
> the just put down layer. It darkens up as you watch, prior to the
> new pass beginning.
>
> Ballendo
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Graham Stabler"
> <grezmos@> wrote:
> >I suspect a barrier preceeds the counter-roller so the powder is not
> >thrown forward directly at the print head. If you look at the
> >machines in the videos you can see that there is some dust on the
> >linear bearings so it does get around. Some extraction (to store
> box)
> >would probably help.
> >
> >One thing that we must remember when we talk about snow ploughs is
> >that the layers are actually really thin, you can often see the
> >previous layer if it is coloured.
>