A rigid spacer for the PTFE/TFM with a viewing hole where one can check that the bowden tube is properly seated.
This spacer can also replace the sometimes problematic spring on the UM2-machines.
I made the spacer 9.6 mm thick, compared to 9.4 mm for the rigid metal spacer on the UM2+, to compensate for bed-leveling inaccuracies.
This means that in normal cases there should be a small gap between the heat break and the block when tightened (see picture).
I recommend to use ABS, CPE or other materials that can take a bit more temperature than PLA for this print.
100% infill works best.
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