Prusa MK3 Bear 20T 5ID Y idler + tensioner (V3, dowel pin)
Description
Rework of the original Y idler by [gregsaun](https://github.com/gregsaun) for the MK3 Bear 2.0 full upgrade with a belt tensioning and tracking mechanism which uses a Gates 20T 5ID toothed idler with a 5x30mm dowel pin. The 5mm dowel pin and the design of this idler offer greatly reduced backlash compared to a screw thread. For a version using the stock 20T 3ID smooth idler, look at [my previous remix](https://www.thingiverse.com/thing:3475507). For a version using a M5x20 screw and nylock, see [my other remix](https://www.thingiverse.com/thing:4091437). This is compatible with the Bear 2.0 full upgrade using the stock MK3 Y belt holder which keeps a straight belt path. This is *not* compatible with the MK3S and/or the Bear 2.1 upgrade due to a different belt alignment. **BOM:** - 1x Gates 20T 5ID toothed idler - 1x 5x30mm dowel pin - 2x M3 thin square nuts (taken from MK3 parts) - 2x M3x10mm screws (MK3 parts) **Printing:** Print with the same parameters as for the original (0.2mm layers, 3 perimeters, 30% infill). Use the provided orientation to guarantee alignment of the reference surfaces. **Assembly:** Insert the thin nuts from the central side slot. Center the nut by pushing on the side slot using a flat screwdriver, do not use an hex key or screw on the thread (doing so can damage the thin nut). Insert the belt and idler, then push and center the 5x30mm dowel pin. Insert the two support wedges in the external slots, minding the correct orientation (use the picture as a reference):  Push the screw/idler towards the front until the wedges touch the inner vertical wall. Insert the M3x10mm screws from the front until they are in minimal tension. Loosely mount the idler on the frame. Pre-adjust the belt under the Y carriage until the belt has some tension (this idler allows for 1.5 teeth of adjustment). Center the idler by pulling the carriage towards it. I recommend to center visually first, ensuring that the entire belt is straight. Now fully tighten the idler on the frame. Proceed to tighten the belt by turning both screws in small steps and at the same rate until the belt has the desired tension. Finally, you can fine-tune the belt tracking by adjusting one screw *only* while moving the carriage to ensure the belt stays centered throughout the entire Y travel. Adjusting the belt tracking is usually better than just shifting a regular (fixed) idler left or right since it allows for all components to stay in a perfectly straight line. The final depth of the screws might not be identical, so do not rely on the insertion depth: rely exclusively on the belt to verify the alignment. Again, with great thanks to gregsaun for his work.
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