Y-Axis Bearing Clamp for Prusa i3 MK2s/MK3

thingiverse

This replacement clamp takes over for the U-bolt bearing clamps on Prusa i3 MK2s and MK3. **Required hardware includes six M3x15 machine screws and six thin M3 square nuts**, identical to those used by Prusa, as shown below. Using U-bolts for attaching Y-axis linear bearings is a bad idea at best. The theoretical contact area between the bearing and the U-bolt is zero. This means that no matter how carefully one tightens the nuts, deformation of either the bearing or the U-bolt is inevitable. This problem worsens when using Igus bearings, which deform easily. I couldn't stop my Igus bearings from sliding back and forth without tightening the nuts enough to cause significant extra friction. This replacement clamp is actually more like a belt. It's printed straight, then wrapped around the bearing. **I recommend printing this in ABS**, which is flexible enough to bend around the bearing while being tough enough to hold it securely in place without stretching. I've tested this on my MK3 with Igus bearings for several months before uploading. I'm extremely happy with how they perform. The bearings can no longer be moved by hand, yet the Y axis slides very smoothly. My choice of thin M3 square nuts may not have been the best decision, as those can be hard to find. Feel free to modify the design for other nuts, as long as you share the result under the same license. I bought my square nuts from a popular online source. Search for 'A2 Stainless Steel Square Nuts Thin Type DIN 562 M3'. The reason for printing this flat instead of designing a U-shaped profile initially is that I believe the criss-cross fill pattern provides more resistance to stretching.