Y Belt Tensioner for Anet A6

Maybe my Anet A6 is slightly different dimensionally than other peoples, but none of the belt tensioners I tried worked quite right. There were some clever designs, but things were not quite in proper alignment. So, I reworked and combined two existing tensioner designs. I also added my own part to help it stay in place. Plus, I included a spacer remix I used to get the belt running at the proper height.

• I reworked NicktheGeek's design so that the idle pulley axle on the tensioner was at the same height as the Y stepper motor axle. This gets the bottom length of the belt loop to run parallel to the Y-axis bearing rods.

• I also changed the position of the tensioning knob so that it pushed on the end of the printer at the same height as the idle pulley axle. This reduces/prevents any twisting or pivoting of the tensioning mechanism as you adjust it, or as the heat plate moves.

• I used the larger knob from MrPaulM design to give me a larger pushing surface for stability. I compressed the knob down so the threads were tighter pitch, so you get more adjustment resolution.

• I added a clip to retain the knob and plate in position. While I was testing the design, I swung my elbow and knocked the knob and plate out, loosening the belt and ruining my test print. Oops! That convinced me I needed something to make sure they stay in place when under tension.

• For my A6, I needed a 17mm spacer to lower the belt connection on the heated plate (so that the top length of the belt loop runs parallel to the Y-axis bearing rods.) I took andreas_g's existing spacer and made it 17mm tall. If you do not already have a spacer of some type on your printer for this purpose, you need it to get the best results from the tensioner, and your printer in general. If you're using something else already, that's fine, don't use the part I have here. To mount the belt spacer, you'll need 4x 4Mx30mm bolts.

12-25-17 Updated the belt spacer file. It had a minor glitch in the STL. If you have the original one, you may have to drill-out the two of the mounting holes.

01-31-18 Updated screw STL file. It had errors that caused problems when slicing with Slic3r. Used Netfabb to repair the model.

Bracket: About 50% fill. Supports.
Plate: About 50% fill. No supports.
Screw: About 50% fill. No supports.
Clip: 100% fill. No supports. (Put a skirt on this for adhesion to the heat bed.)
Spacer: About 50% fill. No supports.

Post-Printing

Fitting the Bracket

I had to scrape off the supports residue, but then the bracket fit into the end brace of my printer without much problem. Depending on how your printer is, you may have to do a little more filling/scraping to get a smooth fit.