"printing" in a loop?

Hi guys,
I want to laser engrave leather belts, but don't want to build a 1+meter laser plotter for that purpose.
What if I take my Prusa and exchange the heatbed with a closed loop of 40cm diameter? I'd place the belt inside the loop and rotate the drum.

Question is, how would I guide and drive the drum? I can't use any spokes.
Would it be OK to glue a GT2 belt on the outside ( or inside? ) and directly run it with a stepper with an open pulley?
The former y-table would be reused to guide the drum with rollers and probably another set of rollers on top of the printer.

Has it been done before? Do you see any problems?
-Olaf

I believe laser cutters have similar attachments that simply substitute the drum rotation for one axis of motion. You might have to change the steps/mm for the drum, and swap the drum's home position sensor for the printer's end stop switch, otherwise it should work.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

... I've done this with a pretty simple turning axe (a NEMA36 stepper motor and a 4bite(?)-chunk) by connecting the Y-axis motor cables to the NEMA36 --- then constructed a drawing with Y-height=steps per revolution ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Can't you put the belt on the *outside* of the drum? Then you can have a solid axle and spokes.

Then just use the stepper that normally moves the bed to rotate the drum, perhaps via a GT2 belt if necessary.

Something like this?

Would it be too difficult to lay down the leather belt flat
with most of belt dangling off printer.

using a laser mounted on X-Y axis to burn the leather

Engraving 6 inches of leather
and moving the belt 6 inches and engraving some more?

Thanks for all your comments and suggestions.

Spokes and center bearings don't work on a Prusa because of the X axis would be going "through" the drum.

Any ideas about the material of the drum? I'd like to find something cheap to Frankenstein my ~40cm dia drum of it.
-Olaf

Found a 30cm drum that could work without the bottom, but is maybe to small. I think, I have to lose a lot of weight, before my belts fit completely in there

Edited 1 time(s). Last edit at 12/09/2015 05:19AM by o_lampe.

Your leather belt would wrap around the drum. The belt inside the drum is a GT-2 for driving the Y axis.

No need for a drum, though. You could just have some kind of "extruder" (a gear that's driven by a stepper motor, and a clamp wheel to press the belt against the gear) mechanism to move the belt. You would probably also need a couple of guides to keep the belt aligned.

This would work with infinitely long belts, but you wouldn't be able to etch right to the ends. I guess the workflow would be to cut the belt to the right width, etch it, cut off the unetched ends, then add buckle and holes.

Quote
frankvdh
No need for a drum, though. You could just have some kind of "extruder" (a gear that's driven by a stepper motor, and a clamp wheel to press the belt against the gear) mechanism to move the belt. You would probably also need a couple of guides to keep the belt aligned.

This would work with infinitely long belts, but you wouldn't be able to etch right to the ends. I guess the workflow would be to cut the belt to the right width, etch it, cut off the unetched ends, then add buckle and holes.

I would risk to try this out, but with multiple passes before the belt is done, I'm afraid of inaccuracies from the friction drive.
-Olaf

Quote
elwood127
Your leather belt would wrap around the drum. The belt inside the drum is a GT-2 for driving the Y axis.
[attachment 67326 DrumandXCarriage.jpg]

Now I understand your point! Thanks elwood

I'd rather put the drum behind the x-carrier and put the laser vertical.
I want to have a small footprint for the printer.
-Olaf

At the very least it will be a great test for the little gray cells. Good luck.

This new super laser cutter kickstarter thing has an option that use its cameras to track where the belt would go. I think if you manually find a good reference you could do it in 2-3 parts and reposition the belt in between.

I thought of adding a 50mw laser pointer diode with a cross optic on the x-carrier to visually align parts.
That would also help to find the right z-distance. When the dot of the cutter meets the center of the cross we are ready to go.
-Olaf

Today, I got another idea.
If I'd like to engrave huge leather belts ( eg. for horses ) or long wooden parts, I could put the prusa_laser frame on wheels and drive along the belt/plank.
The wheel are controlled by the y-axis stepper.
-Olaf