Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

Dave's Parametric X-Carriage for Self-Aligning Bushings

by orgemd, published

Dave's Parametric X-Carriage for Self-Aligning Bushings by orgemd Aug 13, 2012
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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.

  • Use four bushings, or three with just the right bushing on the second rail, or three with just the left bushing on the second rail
  • Include fan mounts on any combination of left, right, and rear
  • Use traditional 40mm fan mounts, or hinged fan mounts
  • For rear fan mount, optionally use a 60mm size
  • Use slides rather than bushings on the second rail
  • Include tensioning for the X-belt on either left or right
  • If tensioning is included allow for a half-twist in the belt

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.

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This is marvellous, I wish all projects were like this!

I noticed what I think is a bug, but the bug doesn't seem to appear in your picture (though it should!)

When I render the file as downloaded, on the left belt tab (where the tensioner is NOT located), the nut trap is missing on the inner hole, but appears on the outer hole.

I tracked this down to the following code change. At the end of the "LEFT BELT CLAMP HOLES" section:
translate(v=[30, -18, PlateT/2 - M3NutD])
nut(m3_nut_diameter, 14);

Fixed (move the bracket up before the nut trap hole):
translate(v=[30, -18, PlateT/2 - M3NutD])
nut(m3_nut_diameter, 14);

Moving the tensioner from right to left moves the missing nut trap from left to right, which is why I don't understand why it is working for everyone else. Perhaps it got introduced in the last change?

Thanks for that, mitchese. I don't know when that crept in. As you can see from the pictures of the one on my current Mendelmax, it was previously correct. The error you found is not only on the left, but also on the right. I believe I have it fixed (just the change you indicate applied to both sides). I will upload a new copy of the SCAD file.


Hi I tried to open this up in openscad, had to figure out to install Greg's Configruation.scad file...but the nut traps just aren't showing up...is there another step I'm missing? Thanks!

Hi Seravi, My best guess is that you do not have functions.scad. My object uses the polyhole and nut functions from that file. To make things a bit easier, I have uploaded the copy of configuration.scad, functions.scad, and metric.scad that I used for this file. If that doesn't solve it, let me know and I will try to look into it a little more.

It works! I had to add include commands for the two new libraries, but then it worked like a charm. I'm going to print once I swap from PLA to ABS. Thanks again!

Super, I'll try it out, thanks!

Hi do you have the source or part # for the busings? thanks

I have always bought mine from http://www.techpaladin.comwww.techpaladin.com where they are sold as 8mm or 10mm bronze sleeves.  I have seen the same parts available from other sources.  They are often sold as self-aligning bushings, or sintered bronze bushings.  I believe the most common manufacturer (although there are probably several) would be SDP/SI.  From them, I believe the 8mm part is A 7Z41MPSB08M, and the 10mm part is A 7Z41MPSB10M.  They are sold as sintered bronze, press-fit, sleeve bearings from SDP/SI.  Please keep in mind that I have not ordered those parts directly from SDP/SI - I am identifying that as the correct part strictly from the description and dimensions.

Just wanted to say that this carriage is awesome. A thousand times better than the screw-on bearing holders. Those 8 screws give you a lot of grief since you have to carefully adjust the tension on each one to have a smooth axis.

I am now using this carriage with 3 bushings and the carriage glides quite a ways on inertia alone with much less friction.

Thanks for the compliment.  I don't like the screw on versions either.  Although it provides some ability to compensate for minor build issues, it can be a great challenge to get them lined up in a way that does not cause binding.  The part that this is derived from (by techpaladin) did not use the screw on holders, and I thought that it was a lot better.  The only problem I had with that one is that I wanted more options with it.  I find especially that three rather than four bushings makes a big difference.  I also wanted fan mounts and wanted to make the carriage a little beefier.