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jit's build: Extruder

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

Get out the extruder kit (bag 18):

The small circular object at the top is a bearing. At left is the gearbox/motor and the Tatsu drive gear. The hot end is at lower right.

(If you were one of the people who got their Bukobot before the bulk of the Kickstarter orders started shipping, then you may have a different extruder design.)

Examine the extruder lever (bottom view and top view):

All of the thin structures on this part must be removed. A good tool for this is the small diagonal cutter (or side cutter):

Also widen the screw hole that's nearest the bottom end of the lever in this view, so that an M3 screw can slide freely through it:

That needs a 3mm or 1/8” drill bit. But don't widen the other hole with that bit!. It will eventually hold a self-tapped M3x16mm button head screw, with no nut.

Clean up this part with a file. Blow away all the tiny fragments of plastic before inserting the bearing.

The bearing goes in here:

Make sure you insert the self-tapped M3x16mm button head screw from the correct side.

Now clean up the other printed part:

None of the holes in this part will need to hold threads, so check that the screws will pass through them freely. The two holes in the base of this part (not the middle hole!) will need a 4mm or 5/32” drill bit. The four mounting holes for the gearbox will need a 3mm or 1/8” drill bit.

Pay special attention to the small hole in the middle, where the filament will eventually pass through. Clean up the conical approach to this hole, without widening the hole itself. There shouldn't be any protuberances that will snag the filament as you try to push it through.

You will probably have to unblock the lower end of the channel that will hold the 60mm long screw. A nut will eventually sit underneath that hole:

Also clean up the mounting surface for the gearbox; the gearbox should lie flat against it.

Before you install anything on the extruder block, get out the extruder mount kit and the hot end. Make sure the M4 mounting screws can pass freely through the two mounting holes in the wooden base of the hot end; widen them if necessary, with a 4mm or 5/32” drill bit. Then bolt the parts together like this:

(If you have trouble getting one of those screws in with the washer in place, leave the washer off.)

(If the base of the block doesn't fit flush against the piece of wood, because of screw heads, don't worry about it.)

Note how the parts are oriented. The aluminum heater block at the left end of the hot end is pointing toward the camera.

Look down the throat of the extruder block, and check that the passage into the top of the hot end is lined up. If it doesn't quite line up, or if you had trouble getting the two screws lined up, you should widen the two mounting holes in the plastic part a bit more, using a slightly larger drill bit, then reassemble this and see if you can get things to line up better.

Now take this assembly apart.

Put the Tatsu drive gear on the gearbox shaft, flush with the end of the shaft; the setscrew end of the gear is toward the gearbox. Tighten the setscrew against the flat of the shaft, using the 1.5mm hex driver. Grab the drive gear and twist the gearbox shaft around until the setscrew is pointing in the opposite direction from the way the wires are coming out of the motor. The motor will be mounted with the wires pointing down, and the setscrew pointing up. The gearbox gears the motor down quite a bit, so it may take some effort to turn that gear.

In the following steps, it's important to add hardware in a particular order, otherwise things will get in the way of other things. So pay careful attention.

Before you install the gearbox/motor on the extruder block, install a screw and washer (if the washer will fit) and nut from the extruder mount kit into this hole in the base of the extruder block, but not the matching hole on the other side:

(In that image, the lever with the bearing is sitting in position on the block, but is not attached yet.)

Install the gearbox/motor onto the extruder block, with the wires pointing down. One of the long screws goes through the hinge hole in the extruder lever:

Install both of the long screws and both of the short screws, as shown above (the short flat-head screws are hard to see in this image, but they're there).

Close the extruder lever and look down through the hole in the lever at the grooved Tatsu gear and the bearing. They should be aligned; the machined grooves in the side of the Tatsu gear must be exactly opposite the bearing. If they're not, open the lever and adjust the position of the Tatsu gear on the shaft, using the 1.5 mm hex driver.

Take the nut off the mounting screw, insert the second mounting screw and its washer, and attach the hot end in the proper orientation, adding the two nuts to hold everything together:

Double check that everything is oriented as shown above.

Add the remaining hardware:

Note that there is a washer on both sides of the spring.

Before installing the extruder on the X carriage, you should add thermal insulation to the hot end. Methods for doing this are described here. You can do it later, but it's easier when the extruder isn't mounted. Some of the images below don't show the thermal insulation.

This assembly is now ready to add to the X carriage. However, you may need to raise the X axis first, otherwise the hot end may hit the platform. If you used the soup can leveling method earlier, then you may not need to raise anything, but you should still go through the steps below to make sure the hot end clears every part of the platform.

If you have a dual-extruder model, you don't need to raise the X axis before installing the first extruder. If you are installing the left extruder, just move the X carriage all the way to the left and the extruder will clear the left edge of the platform. You may still have to raise the X axis before you move the extruder back to the right. The following assumes you have a single-extruder model and have to raise the X axis before installing the extruder.

Hold the extruder assembly next to the X carriage and see how much the carriage has to be raised before the hot end clears the platform when the extruder is installed, remembering that the two mounting nuts won't be there when you set the assembly on top of the carriage. Keep in mind that some parts of the platform may be sticking up higher than other parts, as you haven't leveled the platform yet.

Move the X carriage and the platform until the big hole with slots, where the extruder will be mounted, is above the rear support screw in the middle of the back end of the platform.

Raise the X axis by rotating the Z axis couplers. You need to turn them clockwise, as viewed from above. Rotate the two couplers a couple of rotations at a time, keeping them in step. Occasionally check to see if you have enough clearance to install the extruder.

Once you have enough clearance, install the extruder. Don't move the X carriage or the platform during the following.

Remove the nuts from the two mounting bolts, while holding the assembly together with the other hand, and then lower the extruder through its hole, hot end first. The four wires from the hot end fit through a slot next to the extruder:

Make sure you put the mounting screws through the correct slots. It goes on at an angle, so the extruder motor points straight back. After checking for interferences, put the nuts on the underside of the carriage and tighten the mounting screws.

Note: in the picture above the nut on the tensioning screw has not been tightened as much as it should be. The long M4 tensioning screw is not fully-threaded and the nut should be tightened down all the way to the un-threaded part of the screw. Even so, some filaments are particularly stiff and hard to extrude. If you are trying to use one of these hard types of filament and you can hear the filament periodically slipping (and you have already tried cleaning out the filament drive teeth) then consider adding a few more washers to increase the amount of compression on the spring.

Now it's time for the initial leveling of the platform. We will do this again, more precisely, later.

The primary purpose of this procedure is to make the platform roughly parallel with the X and Y axes, and to make sure there is enough clearance between the hot end(s) and the platform (including anything that may sit on top of the platform, such as the glass sheet), and to practice this procedure. You can put the glass sheet on top of the platform if you wish, as long as you don't forget that it's there and lose control of it, and as long as you don't jam the hot end(s) into it. Alternatively, you can just keep the distance between the hot end(s) and the platform greater than the thickness of the glass. Or perhaps you already installed the glass sheet and tape.

Place the extruder wires somewhere where they won't hang up on the synchromesh cable or anything else. Watch the hot end and slowly move the X carriage to the right. If the hot end gets closer to the platform, then the platform height adjuster on the right needs to be turned. Turn it anti-clockwise, as viewed from above, to lower that side of the platform.

When you get to the right back corner of the platform, slowly move the platform back so that the right front corner of the platform moves toward the hot end. If needed, adjust that wheel to keep the platform the proper distance from the hot end.

Once you get to the front right corner, slowly move the hot end to the left. If it gets too close to the platform, lower the left front corner of the platform by turning that wheel the same way as before. Once you get to the left front corner, it should be safe to move the hot end to any part of the platform. Check that, slowly. If you have any hardware protruding from the top of the platform, such as the electrical connections on the heated platform, don't hit them with the hot end.

If you have a second extruder, do that one too. Carefully check platform clearance, as the second extruder might hang farther down than the first. If they hang at different heights, you may have to shim with thin washers. But first, check to make sure the extruders aren't hung up somewhere on their mounts. Also check that an imaginary line drawn between the two extruder nozzles is exactly parallel with the horizontal steel rods; if not, adjust the position of one or both extruders until it is, or as close as you can get it. A good starting point is to try aligning both hot-ends to the edge of the heated bed glass which you in turn align with the front or back edge of the heated bed.

On the dual-extruder machines, there is an offset between the two hot-ends that is roughly 75 mm in the X direction, zero (or nearly zero) in the Y direction, and (must be!) exactly zero in the Z direction. You have to get the Z offset as close to zero as you can. Then you measure the X and Y offsets and input those numbers into the software before you print (you do this just once at first, and then again any time you loosen your extruder mounts). To measure those offsets, see here. Don't worry about making those measurements right now.

You should now have everything set up so that you won't get a collision between the extruder(s) and the platform, no matter where you move either axis. At this point you should move the Z axis endstop up until its switch is fully depressed. Loosen its 5mm screw (the one holding it onto the right frame piece) and move it up until it stops, then tighten that screw. You will re-adjust the endstop later.

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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-extruder.txt · Last modified: 2014/01/25 17:44 by jit