This is a robust y-belt clamp for the Anet A8 that accounts for the vertical and leftward offset of the y belt on the Anet A8.
Update 9/14/2018: Made the model 2 mm narrower to better accommodate for rear frame braces, as well as to use a more commonly available screw. Better pictures and updated instructions.
After having a few large prints end up a millimeter shorter than expected, I sought to resolve this. I recently noticed, then confirmed online, that the Anet A8 y-belt is actually slightly offset to the left. This is evident in the mounting position of of the y stepper motor, as well as the mounting position of the y-idler on the front acrylic piece (you should check that you don't have yours backwards, it should be closer to the left side). The stock belt holders also don't hold the belt parallel to itself and the rails. Both these issues result in the print moving slightly less in the y-axis than it should.
There are quite a few y-belt holders that fix the spacing of the belt to make it parallel, however I couldn't find anything out there that corrected for the belt's leftward offset. Part of what made this challenging is that the belt needs to mount partially over where the mounting screw needs to be. So I came up with this to address both issues, and made a few structural improvements on top; it's working great for me.
This print uses:
2x m3 phillips screws, 18mm, 5mm round head - I had a few extra from the Anet A8 kit
2x m3 nuts
4x m4 screws (the same ones for the stock y-belt clamp)
This print consists of 3 parts:
The belt housing - holds the belt, oriented so the belt is offset to the left
The first bracket - ends up on the right side of the belt once assembled
The second bracket - ends up on the left side of the belt once assembled
I printed these in the default orientation of the .stl files, and you will need to use supports.
See Post-Printing for assembly instructions :)
Included .scad design files if you want to tweak with them.
This mod did not have any issues with my rear frame brace, but if you use longer screws you might.
*If your y-carriage is upside-down, this print won't give you the right vertical spacing of the belt to run parallel.
35% Triangular, 1.2 mm top/bottom/walls
Step 1: Lightly sand all contacting surfaces, scrounge for m3 screws
You'll want to lightly sand any surface of this part which contacts another surface of the part or the carriage. This gives the surface much more friction grip, and helps distribute loads across the part over the faces. You probably won't be able to reach everything, but do what's easy to get to at least.
This is the screw, m3 18mm threads + a 2mm thick head
Step 2: Mount the y-belt housing to the carriage
Make sure it ends up with the belt holder void/offset on the left side of the bed/carriage, when the bed is back on the printer (looking at the printer). Then just screw it down to the carriage with the stock m4 screws.
Just screw it down
Belt loop void facing left side of carriage
Step 3: Insert the y-belt into the y-belt housing
Fold the y-belt into a little loop teeth down, such that the teeth interlock with themselves, then squeeze that loop shape to fill the void in the y-belt housing. Try to keep the belt along the wall outline, and a hole in the middle for the support post (m3 screw), I didn't have any trouble. Do this for both ends of the belt, making sure there are no twists in the belt, and that the teeth are facing inwards.
Teeth inside, doesn't need much length
Belt loop inserted in void
Step 4: Position Bracket 1 and screw in the y-belt support posts
Press Bracket 1 flush to housing on right side and start threading the 20mm m3 screw through the bracket, the housing, and the loop of the belt. Hold the belt in place with your thumb as you continue threading, until the tip of the threads reach the edge of the belt. The belt should be looped around the m3 screw support post now.
Screws threaded through belt loop
Step 6: Position Bracket 2 and tighten down the y-belt support posts
Press those m3 nuts in to Bracket 2, then press Bracket 2 flush to the left side of the housing. Finish threading the 20mm m3 screw into the nuts of Bracket 2, then tighten.
Final assembled y-belt holder
Step 7: Mount back on your printer and enjoy your new perfectly aligned belt :)
You will now sleep better at night.
Belt runs straight front to back
Belt runs parallel to itself and rails