This is an OpenSCAD file to allow the selection of multiple options in creating an X-carriage for RepRap style 3D printers.This was specifically created for MendelMax 3D printers. The recommendation for these printers is to use self-aligning bronze bushings for the X-carriage. I was frustrated that there were not a lot of options available that made use of those bushings. This thing is an attempt to provide more options. The OpenSCAD file has many selectable choices.In addition, many of the dimensions (like the thickness of the carriage) can be modified.To use this, open the .scad file in OpenSCAD. Near the top of the file are a series of parameters. Set those parameters to reflect the X-carriage you want to create. Render the X-carriage with F6. Export the design as an STL file, and then slice and print as usual.This is still a Work in Progress because I have not tested all of the possible options. The main parts I have been working with are three bushing configurations with hinged fan mounts and a half-twist belt tensioner. That is the configuration included in the included STL file. In particular, I am still doing some testing on the standard fan mount and the slider. I think those are working properly, but they might still need some tweaking.The belt tensioner uses one M4x30mm screw and one M4 nut. The X-belt does a half twist before going around the idler, so that the smooth back rather than the teeth rides across the idler. The belt then passes underneath the clamp area of the X-carriage, around the tensioning ram, and then clamps onto the top of the X-carriage. Turn the M4 screw to increase or decrease the tension.The hinge mounts use two M3x25mm screws, four M3 washers, and two M3 nuts. I had to use a wrench to hold the M3 nut while tightening the screw to get it tight enough to hold the fan angle. It might be worth tightening on a second nut to lock the first or to put a dab of paint on the threads. I am not yet sure how prone the fan hinge will be to vibrating loose without one of these techniques.The belt is clamped to the X-carriage the same as with other X-carriages. The clamps, however, are not included as part of this thing.If you find anything that is not working properly, or have suggestions for improvements, please let me know in the comments.Update 2012-09-07: I am now running this X-carriage on my printer and it works well. I made a number of changes since the original post. I have made the hotend hole just a little bigger. I always had to open that up with knives and files to fit my Budaschnozzle. That should be less necessary now. I made the sliders better hold the 1/8 inch rod intended to fit into the holes. I included a tensioner for those who do not want to half-twist the belt. I added a fan mount in the rear, and allowed for a 60mm fan in that position. I still have this marked a work in progress since I have not built and used all of the possible options. I do not, however, expect it will change much more unless someone reports a problem with one of the configurations.