Anet A8 X-belt tensioner for GT2 pulley

thingiverse

This is a reworked version of Kommander92's creation. The "fork" on the original design had approximately 3mm of vertical movement when used in conjunction with the stock Anet A8 x-idler block (a white injection-molded part purchased early 2018). The looseness allows the pulley to move up and down a great deal on new idler blocks. I increased the distance between the prongs to accommodate the stock idler housing and eliminate most of this play. I assume the original "thin fork" design was intended for printed idler blocks, which probably have a smaller opening. Therefore, this reworked version might not fit printed idler blocks (I do not have any printed idler blocks to verify this... will update some information if someone discovers that this is indeed the case). Additionally, the 16T GT2 toothed idler I purchased online had an overall width of 8.5mm. The flat wall opening on Kommander92's version was 10mm wide. Presumably, the extra space was there to accommodate washers on either side. Standard 3mm washers will rub against the bearing dust shields (no good). So I moved both shaft holes inward by 0.75mm. This transformed the walls where the pulley goes into shallow cones, keeping the bearing well-centered without rubbing on the dust shields (no washers required). I printed this in PLA and it fits nicely. Other x-tensioner components seem to be designed with 20% infill, but for a critical structural component like this, I believe 40% is a more suitable choice.