Note: I made this to fit my HP DraftMaster RX, but it should fit on several other large format plotters that HP made around that time as a lot of their DraftMaster plotters shared many components.

I noticed that my plotter started to loose its accuracy while plotting. The errors would only occure in the Y-axis and the errors were worse after doing large movements. After taking the side off of the plotter, I could see the driven pulley for the Y-Axis movements would slip on its shaft. Looking closely at the old pulley I could see some small cracks starting to form its clamping mechanism. So I measured it up and drew a replacement.

My replacement was designed in two pieces. The pulley and the spacer. The original was a single piece but this would have required a lot of support material to print.

When assembling, the spacer needs to slide on first. The small end towards the bearing and large end towards the pulley. The spacer should slide on loosely. The pulley then needs to be warmed up before pressing it into place. I didn't include any clearance between the pulley and the shaft as this needs to be a tight fit. But warming up the hub of the pulley gently with a hair dryer allows it to form nicely onto the shaft.

Note: The STL files were drawn in Inches. If your slicer doesn't recognize that, simply scale them up by 2540% and it would be printable in millimeters.