Over on the Facebook Group for the Mini, Brian Corbino started a flurry of activity when he posted a description of how he went about changing the plastic pulleys and cheap belts in the Mini with aluminum pulleys and GT2 belts. Quite a number of people were interested in this project, and have been having a lot of success with this upgrade.
Seeing how many people are swapping the pulleys reminded me of something I wanted to fix on the Mini for a long time but never got around to it. What I'm talking about is the way the pulley bracket for the X-Axis idler pulley is fastened to the end of the gantry with a single screw on the center point of the bracket. This means that the pulley is completely free to twist out of alignment when you tighten the screw.
See how the pulley bracket is twisted? This is really annoying, and every time you install this pulley you have to mess around and try and get it straight by hand. Because this annoys me, I created an Alignment Clip that goes between the pulley bracket and the plastic channel where the pulley sits, which keeps the pulley at a perfect right angle to the rods, which will make the belt perfectly flat and level.
Here is what the Alignment Clip looks like before it is installed. To install the alignment bracket, you can clip it over the pulley bracket and insert it into the channel in the end of the gantry, or put the Alignment Clip in the channel first and then install the pulley bracket. If you want to print your very own Alignment Clip, you can get the model from my Thingiverse Page: http://www.thingiverse.com/thing:2049820
Note the orientation of the Alignment clip. It should only clip on one way and should center itself once you install it on the gantry. It should fit snugly in the channel, and prevent the pulley from twisting.
Here's the "After" photo, showing how nice and straight the pulley is now that it can't twist. Does this affect print quality or the life of the belt and pulley? I'm not sure. However, it takes only a couple of minutes to print, and makes working on the belt and pulley totally effortless. You don't have to fuss with the alignment of the pulley by hand any longer.