Prusa (Bear) MK3 / MK2S / MK2.5 Y-Axis Belt Holder and Tensioner

myminifactory

Work in progress - see changelog at end of this description After playing around for my upcoming linear rail mod for Prusa MK3 Bear Upgrade I needed a new belt holder for y-axis because different distances from belt to idler and bed were causing issues. Also, I was looking for a nice tensioner for the y-belt which doesn't shift the axis of bearing or de-parallel-ise belts or bring some torsion in - with no luck. So I designed one myself and made it way stronger than original one, perfectly aligned to original Prusa idler and pulley design with a tensioning along belt. For MK2S/MK2.5: After getting reports about the tension screw of former MK2 Version hitting the pulley on motor I redesigned parts for those printers. As I don't have a MK2 I had to test it in a CAD model which seems to be fine now and holder triggers end-switch before hitting the pulley. The belt path changed because of less space in MK2 version. The sledge and screw are now completely in the block. I made the sledge way a little wider (0.1mm) to counter overhangs there. Please make sure that the belt is on the sledge like shown in the picture with the red circle to maximise its grip. This Thing is a 3-parts design: Prusa_XXX_y-belt_Cover Prusa_XXX_y-belt_Block Prusa_XXX_y-belt_Sledge The Cover is to prevent the belt skipping out of the teethed slots (6.2mm wide) and in the MK3-version also for protecting the sledge it makes the whole thing even more rigid too. The Block is the main block which is screwed to headbed-frog-thingie oriented like the original one The Sledge is the tension-mechanism, which slides into the block (see video on https://youtu.be/oqcmMYRy_z0) Don't be confused by the dimensions on the pictures and the video - it's the version for my linear rail mod and different idlers. This Thing here is for the Original Prusa i3 MK3 with or without the fantastic Bear-Upgrade by pekcitron. The STLs have the right orientation for printing - please don't change it because all the parts are optimised for high dimensional accuracy. You need: 2 M3x20 Screws from the block side through the block and cover 2 M3 standard hex-nuts fits in the cover 1 M3x22 Screw for the (through) sledge (MK2S/MK2.5 M3x20) 1 M3 square nut which slides in the slot behind the sledge tunnel in the block pretty easy, right? Happy printing! PS: I will add the STEPs and a GT3 belt version after my linear rail project is completed (could take some time) Updates: [2018/08/27] Added MK2S / MK2.5 Parts - small refinement on _Cover Small change to _Block for better dimensional accuracy on printing Redesigned MK2S/MK2.5 Part because of screw hitting the pulley [2018/08/27] reduced the height to gain more distance block->belt [2018/08/27] the MK2S/MK2.5 parts are tested at real machines and working with today's modifications