Prusa Mk3 R2B x-axis modifications

thingiverse

I made some significant changes to the X-axis motor and idler ends, denoted as R2b. These modifications build upon the original Prusa files with several key adjustments. The idler pulley bolt has been reversed to create enough space for the surrounding walls and nut to be thickened significantly. In addition, the bolt socket and nut trap have been resized to eliminate slop around the bolt head and ensure a better fit for the nut, as suggested by Geoff Gregor's work (see below). These modifications result in changes to wall thickness and nut trap dimensions on both sides. The nut side now has 2mm walls and traps, while the bolt side boasts 3mm walls and a 2mm bolt head socket, significantly strengthening this previously weak point. To complete these modifications, you'll need to replace the nylock nut with a standard nut (2mm thick) due to tight spacing with the M8 leadscrew. Use loctite to secure everything in place. When screwing the bolt through, be cautious not to scrape against the lead-screw. The motor end modifications are simpler and involve extending the elongated bolt holes that allow for belt tensioning rotation by about 1mm. Geoff Gregor's notes on his R2a modification state: "Summary: Nut pocket slightly bigger, screw head pocket much smaller, less damage, no more slop, screw stays aligned for happy printing (hopefully)." After struggling with a squeaking belt on my X-axis stage, I've come to the following conclusions. Here are all the details in point form, as is often the case when solving complex problems: * This relates to the MK3 Prusa Rev R2 X-Idler Part. * The nyloc nut trap was undersized at 5.37mm instead of the required minimum of 5.42mm. * This caused significant stress on the thin 1mm wall beneath the screw head, often damaging it upon seating the nut. * The 3.1mm diameter holes, initially aligned but not doing their job, were then held in place by counterbore pockets for the nut and screw head. * The nut was centered due to its inability to move. * However, the screw head had a larger pocket (6.0mm) than it needed (5.42mm), allowing it to move about 0.5mm out of alignment. * The modifications changed the nut side's wall thickness and nut trap dimensions from 2.5mm (wall) and 2mm (nut) to 2mm for both, while the bolt side changed from 1mm (wall) and 2mm (bolt head socket) to 3mm for both. * The modifications also eliminated slop around the bolt head and ensured a better fit for the nut. * A standard nut (2mm thick) should replace the nylock nut due to tight spacing with the M8 leadscrew. Use loctite to secure everything in place. * Be cautious when screwing the bolt through not to scrape against the lead-screw.