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

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ballendo" <ballendo@...> wrote:

>
> Graham,
>
> Thank you for the additional details.
>
> A quick thought: Cheap and/or thrown-away desktop scanners are now
> widely available over here (They're in all the thrift stores for a
> few bucks). these would be a cheap sources for an additional axis of
> travel with belts and guides...

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 you can use one of
the paper take up rollers and the paper feed encoder to make a wheel
encoder. The cable drive system means I can get exactly the same
reduction ratios for pretty much no cost and only need to turn a few
rollers and perhaps pulleys.

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.

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?
Plenty good enough for the supply don't know about the build area.

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:

http://www.gifts2go.eu/shop/index.php?main_page=product_info&cPath=4&products_id=28

Obviously a proper built solution would be better in the long run.

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.

Graham