The better y-rod holder

General information

On both my MK3S+ as well as the MK3.9/M4 I encountered issues with the y-rod holder. The super flimsy latch broke on me several times when tightening the M3 bolt. I now redesigned the y-rod holder that it works with a pressfit. I got rid of the M3 screw and square nut that would clamp the rod to the holder completely. This is now done by the geometry of the part automatically, meaning the flimsy latch is no longer needed.

The same part can be used for all four positions of the y-rods. Just make sure that you always assemble it the correct way around. There is a chamfer on one side of the central bore hole which allows for an easy insertion of the y-rod and nice engagement of the press fit bore. There is a mark on the chamfered side of the part.

There are two versions of the part. They differ in the mounting style of the rod holders on the printer frame. One uses square nuts like the original prusa design does. The other version has bore holes for heat set inserts. Both versions are available with different central bore sizes, ranging from 7.9mm to 8.2mm. Choose the right bore hole size depending on the stiffness of the filament used. PETG is rather flexible, so you will be fine with the smaller ones. Take a bigger bore hole for stiffer materials. I choose 8.1mm for ASA with carbon fibre. If you are uncertain, print and test one part of each bore size and only then print all four parts needed for your printer. 

Printing

There is not a lot to watch out for regarding printing. Just make sure you place it the right way on the printbed. 

Design for heat set inserts

The version for the heat set inserts must be placed with the chamfer mark visible on the top of the part. The green arrow indicates the printing direction.

Design for square nuts

The version for the square nuts must be placed the other way around. The chamfer mark must face the build plate. Again, the green arrow indicates the printing direction. After printing of this version, make sure to take a 3.3mm drill bit and ream the two holes. There is a one layer thick film left in the bore holes that must be removed before assembly.