Prusa MK3 Bear 20T 5ID Gates Y idler + tensioner
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. For a version using the stock 20T 3ID smooth idler, look at [my previous remix](https://www.thingiverse.com/thing:3475507). 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 M5x20mm screw - 1x M5 nylock - 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). **Assembly:** Insert the thin nuts from the central side slot. The hole is intentionally tight, so do it carefully. Center the nut *perfectly* by pushing on the side slot using a flat screwdriver, do not use an hex key or screw on the thread (doing so *will* damage the thin nut due to the tightness of the fit). Insert the belt and idler, then use the M5x20mm screw with nylock nut. Do not use force: the idler shouldn't bend inwards. The thread only needs to reach the nylon insert, lateral play is fine. Push the screw/idler towards the front. Insert the M3x10mm screws from the front until they simply touch the screw and bolt. A drop of low/medium strength thread-locker is recommended. 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. 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 is not perfectly identical due to the shape of the nut and axis adjustment, 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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