3D Printed Pulleys

I am planning (what I do to add to my project list when it's too cold to go across to the workshop) to make a back shaft setup for a 6mm Wolf Jahn lathe which is mainly used for polishing clock pivots.

The lathe has a three step pulley in the headstock and uses 3mm belt. It's driven rather too fast by a small sewing machine motor (which came with it).

After 3D drawing a suitable set of pulleys for the back shaft setup, it occurred to me that rather than turning them out of aluminum, It might be equally possible to 3D print them. The OD of the largest pulley is <50mm and the overall width of the set is <25mm. They will ride on some 8 x 16 x 5 bearings I have left over from another project.

Has anyone printed pulleys in this way, and used them with 3mm round belts.

Any gotcha's or specific materials to use.

Hi Peter I have printed lots of stuff for my models , fishing and the wife's sewing but nothing quite like a pulley.

However the valid point i would make is you are likely to need "support" at some point and my experience with that is it can be a pig to remove and can leave some sharp edges that will not do the belt much good unless they are very well smoothed off.

Suggest you try slicing different orientations, maybe using a raft, to try and minimise the amount of support that will be in the " V's ".

Definitely worth doing though.

Good luck.

Clive

I should think that 3dprinting would be an ideal application for a pulley on a small lathe like that.

I don't think it's cast in stone that you will actually need support for the vees. (If indeed they are vees rather than a circular section). It's surprising what you can get away with in this respect (try some of the test-pieces on Thingiverse).

In any event, if it were me, I'd first try, as a test, a single pulley section laid flat **, using a circular belt profile if that's feasible. and minimising the depth of the belt profiles as much as possible I'd keep the taper-angle for the vees as large as I reasonably could too

.I'd print this without support and see what happens.

For material, I would think ABS ould be preferable o PLA but ome of the more advanced materials (of which I have no experience) might possibly be better .... don't know.

Edit: ** Come to think of it, I'd just start printing the whole model and stop it if the first section is unsuccessful.

Edited By Peter Greene on 07/02/2021 20:04:14

Daft suggestion, print the pulley in two halves and screw the two halves together.

Should be quite possible. Print with the largest diameter down to give best bed adhesion. If circular grooves for a round belt may well print without support. If a V pulley may need minimal support to support the top of the groove most slicers will work out the supports automatically. Might be worth increasing the number of perimeters in the slicer software. Could print solid but probably unnecessary try 25-30% infill. Try PETG if you have any but PLA likely to be OK.

John

Not quite a pully but I've printed an idler wheel for my printer mod - 29mm dia by 10mm wide to fit on a pair of flanged ball bearings. I actually made it slightly larger on the OD and under in the bore and then skimmed them back to size. It worked fine, I printed it with PLA at 100% fill. If you do skim any of the diameters run at a fairly low speed as there is a risk of melting the printed part.  Sorry about the lousy picture!

Edited By Henry Brown on 07/02/2021 22:11:17

I shouldn't worry about the supports - you can clean the surface up by putting it in a lathe or holding it in a drill against a file.

Edited By Bazyle on 07/02/2021 23:46:16

And it should be relatively easy to print a cone of sizes - rather than making them individually.

Just in case you had not thought of that.

Cheers, Tim

An update for anyone interested. I modelled the pulley set, and printed it in PLA in two pieces. A single motor pulley and a set of three to drive the lathe. The largest pulley in the set of three is 55mm diameter. I printed with standard Cura settings for my Ender 3Pro, no support and standard 20% infil.

It came out well. With 16 x 8 x 5 bearings presses into recesses in both ends of the 3 pulley stack, a piece of 8mm steel rod for the spindle, and M3 bolts to hold it together. Very pleased so far. Todays project is the frame for the motor and to hold this set.

Nice looking parts, Peter. I'd still have slight reservations about the PLA if continuous belt slippage is a possibility (because of friction heating) but if that's not an issue it should work well. Easy to suck it and see.

My only concern would be, A that the less than perfectly smooth surface may cut up the belt and B that any slipage will cause heat and melting. I had a gear assembly that was left in the sun and melted ! Noel

Nice one Peter, I understand the reservations but you can prove the theory and if you have a problem you can soon print it in PETG (if you keep the files of course) which should be plenty strong enough I'd have thought.

Thanks for the encouragement.

The lathe (a 6mm Wolf-Jahn copy) is really only used for polishing pivots so the loads should be small. If I do have problems I will try PETG.