jit-s-build [Bukobot 3D Printer Instructions & Docs]

**jit's build**

This is documentation of the building of a Bukobot 8 Duo kit.  This model has two extruders and a heated bed.  The single-extruder version of the x carriage is also shown.  Nearly everything here should apply equally well to the smaller versions of the Bukobot.

Some photos show printed parts lists.  These are based on an early version of the Bill of Materials (BOM), and may not exactly match your kit.

The background grid in some photos is a 1 cm grid.
 
{{wiki:jitsbuild:x-carriage-duo-kit.jpg}}

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.

The parts for each linear bearing are:

{{wiki:jitsbuild:linear-bearing-subassembly1.jpg}}

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:

{{wiki:jitsbuild:linear-bearing-subassembly2.jpg}}

Snap the bearing into printed part, and verify that it fits well, and that the two parts are parallel.  Do this with all of the linear bearings and holders, and compare them;  they should look the same.  Also verify that the flat face of the holder has no protrusions that will prevent it from lying flat against the X carriage plate.  If needed, trim the part (remove the bearing first!).  See [[Cleaning up printed parts]].  

If you haven't done it yet, remove the bearing from the printed part.  (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.)

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.

{{wiki:jitsbuild:threading-a-printed-part.jpg}}

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, but don't tighten completely.  Later you will remove the screw, while carefully holding the nut in place, and pass the screw through the X carriage plate and back into this same printed part and nut.

Insert the bearing into the holder, make sure it is centered and parallel, and wrap one cable tie around the subassembly to secure the bearing into the holder:

{{wiki:jitsbuild:linear-bearing-subassembly3.jpg}}

Now cut off the loose end of the cable tie.

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




{{wiki:jitsbuild:x_left_kit.png}}

The printed plastic part shown in this image has a significant overhang in the large circular opening.  The printing technique used to make this part cannot produce a sharp clean profile with this kind of overhang, so the part must be trimmed before you attach parts to it.  See [[Cleaning up printed parts]].

Sometimes you will find that a screw will not easily fit into a hole in the printed part.  This printing technology cannot produce holes of a precise size, so parts designers adjust the size of holes to minimize problems for builders.  If a screw is intended to be self-tapped into a hole (with no nut on the other side) it is important that the hole not be too wide, so the designer will specify a smaller hole than really needed for that screw.  If you have a lot of trouble turning a screw into a hole, widen the hole, but not too much.

On the other hand, if a nut is to be used on the screw, the hole can be widened until the screw easily passes through.  Be very careful to determine which holes use nuts and which don't, as it can be a big hassle if you remove too much plastic from a hole that needs it to hold threads.

Sometimes a designer will indicate which holes need nuts by printing a nut-shaped depression at one end of the hole.  In some cases you can press the nut into this depression and it will stick there.  But if this depression is printed on the bottom of a part, its shape will not be very accurate and the nut may not fit into it.  In this case, you may not have to adjust the size of that depression to actually fit the nut;  add the screw and nut to the part, then check to see if the protruding nut will interfere with anything.  Often there is no potential interference, and no need to do anything else.  Consider the nut-shaped depression to be just a hint that a nut goes on that side of the part, and not an actual required feature of the part.

Note that there are generally no lock-washers.  Vibration during operation may cause nuts to unscrew.  You can use a dab of threadlocker (the blue removeable type) to hold nuts in place.  Many nuts and screws are left loose throughout much of the build process, so that the position of various parts can be adjusted in later steps;  don't apply threadlocker until these adjustments are made.  If you are worried about nuts working loose during the build, apply a small dab of threadlocker near the end of the screw, far from the nut;  the nut may work itself toward the end of the screw, but it won't leave.

We add one stepper motor and one synchromesh pulley:

{{wiki:jitsbuild:x-leftend_assembled_bottomview.png}}

Note that the two nuts near the bottom of this image are sitting on top of nut-shaped depressions, but don't fit precisely into them.  They don't need to.  There is room on the bottom of this part for the nuts to protrude from the surface.  Threadlocker will be used later to keep these nuts from wandering.

Top view:

{{wiki:jitsbuild:x-leftend_assembled_topview.png}}

The nuts with fender washers on them should be quite loose.  The long steel rods will be inserted under the fender washers later.

The wires for the stepper motor have been threaded through the oval hole near the motor.



//The contents of this page may be re-used under any of the following licenses:  The [[http://creativecommons.org/licenses/by-sa/3.0/|Creative Commons Attribution-ShareAlike 3.0 Unported License (CC BY-SA 3.0)]], or the [[http://www.gnu.org/copyleft/fdl.html|GNU Free Documentation License (GFDL, version 1.2 or later)]].//
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