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

When ballendo was talking about the 4 leadscrew thing, i remembered i
saw something on cnczone, heres the link:
http://www.cnczone.com/gallery/showgallery.php/cat/505/ppuser/11929
I thought it was going to be a little more detailed, but there it is
anyways. (the two pics on the right side, red machine)
Frankly, i was lost on the description Ballendo gave on the details of
the construction of the bin. Anyways, this is all I could imagine from it.
Regards
Fernando

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ballendo" <ballendo@...> wrote:
>
> Graham,
>
> Snips, inserts below...
>
> >In CCED, "Graham Stabler" <grezmos@> wrote:
> >I've lots of printer and scanner parts but I wanted to try and keep
> >the ratios between the servo motor and the drive as they are,
> >finding a set of pulleys etc of the right diameter might be a
> challenge. That said if you find something of about the right size
> <snip>
>
> Makes sense. Keep as much of the "native intelligence" of the
> printer as possible...
>
> >As for the rest of your description; its pretty much as I imagined
> >they might build it although I'm also not sure they bother having
> >the gap at the sides of the build area, its raised up but there
> >seemed to be some little fenders near the ends of the rollers. If
> >the sides of the build box are beveled inwards any little bits of
> >excess will fall in around the edges, the build platform lowers
> >before printing anyway so it would not cause a problem.
>
> Yes, the gap is a solution based on using cheap perspex as the
> material, and not wanting to do a lot of extra edge
> chamfer/detailing. One thing I HAVe thought about is whether the bin
> material being plastic--as in your pumps and my perspex--will keep
> the powder from "sliding" when the bin bottom is lowered? The shiny
> steel shown in the Zcorp pics might be a "necessary" item?
>
> >I'm not an overly big fan of using 4 leadscrews, I've never done it
> >but it seems a recipe for problems potentially. You are using the
> >grommets on your tubes and the fit between the piston and box as
> >your linear bearings essentially, there is bound to be some
> >rocking?
>
> I've done it many times; including things not cnc related (platen
> clamps). You see it on some wood planers as well. It works well, and
> is easily adjustable for rocking and plane orientation. But one
> could instead use two REAL linear bearings and one
> leadscrew/actuator. Was thinking of a: Weekend-buy-the-perspex, get-
> out-the-table-saw-and-glue-and-get-er-done kind of thing<G>
>
> As for any unintended rocking; that's the reason fo rusing 4 screws:
> any poor fit between the bin bottom and the bin sides will be
> constrained to sideways motion. Likewise the fit of the tubes in
> their grommets. The only vertical shift will be a component of the
> relative movement VARIATION between these two "planes" moveing
> sideways. And that's gonna be extremely small, considering all the
> dimensions.
>
> Put one hand above the other. Hold one end of a common string in
> each hand. Move hands side-to side... You have to move quite a ways
> before the distance vertically between your hands changes due to the
> string constraint...
>
> >If I use my piston idea I'll use single lead screws into nuts in the
> >"con rod" as you describe, that seems a pretty good solution.
> >This is the kind of pump I'm talking about:www.gifts2go.eu<snip>
> >Obviously a proper built solution would be better in the long run.
>
> Concern is for their round areas. The "snowplow" will be working
> over an area (between the two) where no rise and fall can be
> accomplished.
> I'm visualising problems due to that with scatter, uneven layering
> in the build area, and powder build up...
>
> Which was basically why I detailed the perspex tank idea; I figured
> for you that might end up being easier than the kluge of the pumps,
> and should work well enough to keep working; rather than just being
> a test of the concept?
>
> >for the shake rattle and empty you could just add a door to the
> >bottom of the tank one that only opens upwards, then just start
> >prodding it with a solenoid.
>
> Yes, I also thought about a "door". Not sure it's the best way to go
> though...
>
> Thank you for the fedback,
>
> Ballendo
>