Tensioner Idler (CTC, Geetech, Pro B)

thingiverse

I purchased a budget-friendly printer from eBay, a CTC clone made by Geeetech, and 5 mm plywood. The X-axis idler/tensioner on my machine self-destructed - check out the photos for yourself. The challenge with this particular component is fitting together the combination of bearings, pulley, and shaft within a single piece of plastic without moving the pulley on the shaft. In my case, the pulley won't budge, and I'm hesitant to apply too much force. Based on design [2], I initially divided the part into two pieces by splitting it horizontally. The split line is located just above the center of the bearings, causing them to snap into place in the bottom piece. For version 2 (files suffixed 2), I employed a couple of small self-tapping screws (1.7 mm thread x 7 mm thread length) to hold the two pieces together. In version 5 (files suffixed 5), I split the part vertically into three pieces and used the tensioning bolt along with an extra M3 nut to keep it intact. The middle piece features a slot that allows it to move outward, enabling the shaft to be inserted. Meanwhile, the back piece has a peg that locks the middle piece in place when the nut is tightened. This version prints smoothly and represents the best solution. After some trial and error, I discovered that idler pulleys running off-center can compromise print quality. As a result, I replaced the original pulley with a metal one. The sixth iteration of the tensioner accommodates this type of pulley without requiring multiple components - instead, it features a simple axle passing through the bearing, which is part of the pulley. The OpenSCAD source code for this design is included. Prior art: [1] http://www.thingiverse.com/thing:1830392 [2] http://www.thingiverse.com/thing:2059238