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jit's build: X carriage

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This page pertains to the Bukobot v1. Some portions may be useful to v2 owners. For more information, see here.

Bearing Assemblies


This kit is for the X carriage of the dual-extruder model. The kit for the single-extruder models is the same, except the lower five parts shown on the parts list are each quantity three instead of quantity four. (This is bag 17 plus a metal plate from the flat-pack in the currently shipping kit)

The parts for each linear bearing are:


The printed plastic part may need trimming before assembly. Place the nut into its hexagonal hole in the printed part, and make sure it fits flat against the bottom of its hole:


Snap the bearing into the printed part, and verify that it fits well, and that the two parts are parallel. The bearing should be seated all the way into the printed part so that the inner shaft of the bearing is just above the lip of the printed part. A fully assembled bearing is shown below. But before you do the final assembly with the nut and zip tie, make sure all the bearings fit into their printed parts well.

It is now recommended that the zip ties be left off until a later step.

Do this with all of the linear bearings and holders, and compare them; they should look the same.

A good way of checking the bearing holders is to insert bearings into all of them and then put one of the precision steel rods through them, as shown below. Get out one rod, and examine the ends; one end may be smoother than the other. The smoother end is the end to be inserted through the linear bearings. Insert it carefully, right down the middle, without banging the end of the rod against the bearing balls inside the linear bearings.

Here, the second one from the right isn't lining up with the rest. You can also see a printing defect in this part, where one layer looks different. This part is usable; it just needs to be trimmed a bit.

Where needed, trim the part (remove the bearing first!). See Cleaning up printed parts. The surface that the bearing sits against can be checked for extra plastic by running a 1/4 wood chisel down the surface in about 4 swaths, rotating the part and doing it for the other side. Being careful not to alter the shape or surface of the part, any little tabs of plastic can be scraped off with the chisel. This will help the bearing sit even.

Remove the bearing from the printed part, if you haven't done it yet. (If you can't get a good grip on it, insert your 5mm hex driver through the middle of the bearing and carefully pry it out.) Now insert the screw into the hole in the printed part. Does it slip in easily? If not, you have a choice: widen the hole, or thread the hole.

This screw fits into a nut, so it is safe to widen the hole. (Some other holes in the machine will be getting a screw but no nut, so those holes must not be widened too much or the screw threads won't hold.)

Alternatively, you can thread the hole. Since a nut will be applied, it is important that the threads you make in the hole line up with the threads in the nut, otherwise the nut will float above the bottom of its hole.

To properly thread the hole, insert the nut into the hexagonal hole in the printed part and thread the screw through the nut and into the printed part; some force will probably be required to turn the screw, but with a screw this large it shouldn't be too difficult.


Then, remove the screw, being very careful not to let the nut fall out of its hole. Move the screw to the other end of the hole and screw it in, making sure to get it into the threads you just cut into the printed part. As long as the nut remains in the same position as before, lying flat against the bottom of its hole, its threads should line up with the screw as it emerges from the plastic. Screw the screw through the nut.

That was just for demonstration. As it turns out, the holes in the linear bearing holders shouldn't be threaded; later steps will be easier if the screw slips through the hole easily. If necessary, widen the holes in all your linear bearing holders (you have seven or eight of them altogether). Then insert the screw and nut and tighten.

Insert the bearing into the holder, make sure it is centered and parallel. Later, zip ties will be applied to one side of the assemblies, as shown, to secure the bearing into the holder:


When adding the zip tie, make sure the head of the cable tie isn't on top of the flat surface of the holder; position it next to the bearing. Make it tight, and then cut off the loose end of the cable tie.

In many images that follow, zip ties will be shown as already installed. Ignore them. The zip ties will be added after the printer is first powered up.

Repeat the above for all of the bearings needed for the X carriage (three or four of them).

Assemble X Carriage

To complete the X carriage, you will need one or three flat metal parts (see kit #6b). Remove the screws from the printed parts, and screw the bearing assemblies onto the metal parts as shown.

For the single-extruder models (bottom view):


For the dual-extruder model (top view):

Note the two screws in the middle of the dual-extruder assembly. These screws increase the stiffness and stability of the X carriage. 2 x M5 10mm screws and nuts are provided in the current Duo kit for this purpose.

If you are an “early adopter”, you may not have gotten this additional hardware. You can use any hardware that fits. Make sure that the screws don't collide with the steel rods that will pass through the linear bearings. If it's too close for comfort, you can mount the screw with nut on the top side of the carriage (or put a washer under the screw head).

For the dual-extruder model (bottom view):

Add a few more parts:

Also add a terminal block (six positions per extruder) and attach it with an M3x16mm button-head screw and nut (one set per extruder). Note: The terminal block on the Duo x-carriage may be slightly offset to one side as the terminal pitch does not exactly match the x-carriage slots. For the Duo, try putting both screws through the second hole in from each end. One screw then fits into a vertical slot and the other screw fits into one of the diagonal slots.

You should also attach the X tensioner using the M3 x 16mm screw through the center and on of the other M3 screws to lock it in position as shown below (from bag 17a):

The remaining 2 x M3 10mm screws and 1 M3 nut (one loose M3 screw shown above) will be used later to attach the synchromesh cable to the X tensioner. Put these screws and nut back in the X tensioner bag for now.

(Apparently some early adopters got M2.5x16mm socket-head instead of the M3 for attaching the terminal block. That's what is shown above. If you got the M3, you may have to use the nut to crank down the screw head – or vice versa – into the terminal block. The M3 nuts fit in the terminal very tight and it will have to be jammed in. You can take the M3x16mm socket-head and thread the M3 nut on the end. You can then align the nut on top of the terminal and gently tap it in, ensuring that the nut stays flat. The terminal will flex somewhat, but as long as you are not using excessive force it should be fine. After the nut is seated in the terminal, you can back the screw out and insert it from the bottom side to attach the terminal to the x-carriage. The picture below shows the terminal already mounted, DO NOT try to jam the nuts into the terminal while it is on the aluminum frame!) (See here, and the later posts.)


Position the terminal block(s) so that they won't interfere with the X tensioner or the matching slot on the far side where the synchromesh cable will be attached.

Now set the X carriage aside.

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The contents of this page may be re-used under any of the following licenses: The Creative Commons Attribution-ShareAlike 3.0 Unported License (CC BY-SA 3.0), or the GNU Free Documentation License (GFDL, version 1.2 or later). Nothing on any of these pages is there to tell you what to do, only what other people have already done.

jitsbuild-x-carriage.txt · Last modified: 2014/01/25 17:38 by jit