Tweaks to ReDuplicator i3 MK3x

During my Make of the Reduplicator i3 MK3x https://www.thingiverse.com/make:816764 I tweaked or created a few new parts. Those are collated here for convenience.

• The X axis idler and Y axis idler had some minor geometry problems, which I cleaned up in DesignSpark Mechanical before printing. (Tinkercad is only so precise in STL exporting - was glad to see the author begin moving to F360). See my remixed idler STL files here.

• I slightly tweaked the "bearing on a bolt" design of the X and Y axis idlers by designing some spacers that ensure that gentle pressure / bracing is applied to the center of the bearings when the bolt is tightened. See the X / Y axis idler washer STL files included here.

• I created some spacers to fit into the oval slots on the outside of the Y axis idler. Combined with washers, this lets the bolt head and nylock nut for the Y idler bearing sit level with the sides, and makes it much easier to adjust. See "Y axis idler washer outside".

• I widened the holes for the heat inserts to 5mm on some models to match the requirements of the inserts I was able to obtain. These tweaks are included in the remixed X/Y idler STL files.

• Created a small bracket for securing a filament guide made from PTFE tubing. The design and placement of the guide accommodates mounting a bearing-based spool holder on top of the control box for super smooth filament feeding (I used this spool mount: https://www.thingiverse.com/thing:3774268 ). Note that attaching the filament guide to the X carriage required drilling out the little filament hole above the extruder tension lever in the MK10 X carriage. See the filament guide STL file.

• See https://www.thingiverse.com/thing:4445718 for the omnidirectional cooler I created to improve cooling.