Parametric pulley - lots of tooth profiles
by droftarts, published
Tooth profiles currently supported are MXL, 40DP, XL, L, T2.5, T5, T10, AT5, HTD (3mm, 5mm, 8mm) and GT2 (2mm, 3mm 5mm).
NOTE: error in script regarding L and H pulleys spotted by OSTycoon (see comments) - the script says H, but actually it is L profile.
There are a range of editable parameters for editing the fit of the tooth (to account for printer variation), the pulley base, captive nut(s) slot for the set screw, motor shaft diameter, pulley height and belt retainers.
The attached stls are reference pulleys, mostly around the size used on repraps.
After creating the parametric pulley thingiverse.com/thing:11256 I realised this way of modelling them was only going to work for square-toothed pulleys, and a way of producing pulleys for belts with better characteristics for linear motion was required. I found dxf drawings of the relevant tooth profiles here oem.cadregister.com/asp/PPOW_Entry.asp?company=915217&elementID=07807803/METRIC/URETH/WV0025/F and modelled pulley diameter from data here sdp-si.com/D265/HTML/D265T016.html
There were a couple of possible approaches to importing the data, I chose to simplify the bezier curve dxf data in Inkscape, producing vertices with a resolution of around 0.05-0.1mm for each tooth. Another advantage is the the pulleys have the tooth ramp for smooth entry and exit of the belt tooth into the pulley. I'm not really sure 3D printers can take full advantage of this yet, but quality is improving all the time!
If other tooth profiles are required, or you model any, please pass them on to me and I will include them.
22 March 2012 - Updated for issue spotted by mfinn - see comments
Recent Commentsview all
Thanks, I was trying to print a giant 150-tooth gear, that geared down a 16-tooth metal GT2 pulley (obviously next to impossible to find an off-the shelf gear that big, for cheap). I ended up getting it printed out with an 0.3mm nozzle, but just barely. Thanks again for this wonderful set of openscad tools.
RepRapPro (I work for them now) used to use a 0.3mm nozzle, set with a 0.3mm extrusion width, to print MXL pulleys. These have a pitch very close to GT2 (2.032mm), and the printed pulleys gripped the belt and worked fine. I think the rounded tooth shape of GT2 would actually help - the pulleys we produced didn't have particularly sharp tooth profiles. I think you'll struggle with anything larger than a 0.3mm nozzle. Make sure you've got good vertical straight walls, or the wobble will ruin fit, and your retraction settings are well-dialled in. Printing the outer perimeter before the inner can often help with accuracy. We've moved to supplying aluminium pulleys now, as we couldn't keep up with the quantity we needed with printing!
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2. Tweak to make your perfect pulley
3.1 If you get blobs and/or stringing, you may need to reduce the perimeter speed, perhaps as low as 10mm/s depending on your electronics/baud rate etc. The model is high resolution, and slicing software will produce lots of very short moves, that the comms may not be able to keep up with. Alternatively, print from SD card. Printing slow should improve the tooth shape, and fit of the belt.
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