MendelMax build: X and Z axes
I titled the last post in the build guide “MendelMax Build: frame part 1” because I anticipated there’d be a part 2; turns out the build was faster than I thought. Let’s move on to the X and Z axes.
First, assemble your X-carriage. This should be a matter of attaching whatever manner of bushing or bearing will make contact with the X smooth rods. I’m using a variant of Josef Prusa’s X-carriage I made that better supports the Igus bushings I sell:
Next, stick two of your smooth rods into one of the X-ends, either the idler holder or the motor holder, it doesn’t really matter which one. You want to be careful when inserting the rods if you’re using push-fit X-ends, as you can easily crack the whole thing if you jam the rods in too hard. You may have to ream the channel a bit or support the top and bottom when you insert the rods. Easy does it.
Put the X-carriage onto the rods before you cap them off with the other X-end. Make sure the carriage’s two rounded protrusions are on the same side as the motor mount and the hole for the idler.
It should all look like this:
Now you need to attach to the MendelMax frame the smooth rods that these X-ends will ride on. First, attach one of the rods to the motor mount so it hangs down to the bottom:
Note: those Z-rod clamps are the versions that are on the Thingiverse page; you may have newer ones that look more like this:
Now attach the lower holder and align it with the rod that’s hanging down:
Not quite there yet! You can screw the clamp right into the holes on the lower holder; no M5 nut is necessary, since this isn’t a high-stress part.
Once you’ve got the lower rod holder aligned, move the rod up a bit. Then put the completed X-gantry you assembled earlier on the frame beneath the bottom end of the rod, and line up one of the X-end’s bearing column with the rods:
Lower the rod down into the X-end’s bearing columns and tighten the clamp on the lower holder. Then do the same thing on the other side. You should have an attached X-gantry that look like this:
Make sure the gantry slides up and down smoothly, but be very careful when lifting it, as you can easily crack the X-ends’ bearing tubes at their bases. This is even more true if you happen to be using Prusa 2 LM8UU X-ends, but it’s a risk for any printed X-end. The safest way to lift the gantry is using one hand under the X rods, as close as possible to the centerline of the machine. Go slowly and if you feel resistance, let it return to the bottom while you make adjustments.
The gantry should be able to return to the bottom by gravity alone when you raise and lower it with your hand under the center of the X rods. If it binds at all, you may need to slightly adjust the position of the X-ends on their rods or move the lower Z rod holders a few millimeters to the left or right to straighten out the Z rods.
Once the gantry slides up and down smoothly, it’s time to insert the leadscrews! First thread a leadscrew into the X-ends. Make sure the top end is a little beneath the hole in the motor mount.
Attach one of your aluminum couplers to a motor. Tighten the lower set screws to join it to the motor shaft, but make sure that the upper set screws are loosened enough not to obstruct the leadscrew when you insert it.
…and then put the motor onto the mount, letting the leadscrew enter the coupler’s larger hole:
Tighten the remaining set screws to attach the leadscrew to the coupler. Keep in mind here that doing so will slightly deform the metal of the leadscrews where the set screws dig in. DO NOT attach a leadscrew to the clamp at one end, and then change your mind and clamp it at the other end instead, because the first end will have deformed threads and it won’t go through its nut. You don’t want that.
Finally, screw the motor to its mount. Even though there are four holes, you really only need to attach the motor with two screws.
Now do all the same things for the other leadscrew and motor. Once the leadscrews are attached and the motors fastened to their holders, rotate both leadscrew shafts to bring the X-gantry up towards the top of the frame. This will take it up out of the way so you can later assemble the Y axis easily. You should wind up with this:
Congratulations! It’s getting closer… now time for the Y-table!