Easy Monoprice Mini Select Extruder Upgrade

thingiverse

This isn't a printed part, but instructions on how to almost painlessly upgrade your extruder to an all metal MK8. What You Need ============ You will need a "right hand" MK8 set for 1.75mm filament. On eBay right now these are maybe $8-$10. You will also need an MR104ZZ bearing. I bought 10 of them on eBay for $7. You only need one and if you don't mind waiting, you can get them for MUCH less. What You Won't Be Doing ==================== You DO NOT have to take the case off your printer. You DO NOT have to remove that pesky extruder gear that won't come off. You DO NOT have to change the stepper or recalibrate the extrusion. Once you have all the parts, it should take about 10 minutes. Here's the trick. It is easy to remove the extruder handle. Note the shape of the plate underneath (the black plastic pictures). See the corner that is "dog eared" that is circled in red? That dog ear misses one of the stepper motor bolt holes (the smaller red circle). That's the key. I had always failed to do this upgrade because I could not get the gear off the stepper. It is on there but GOOD. Advice Before You Start ================== Because the stock bolts strip easily, I suggest that before you start, you remove them one at a time and either snug them back but not too tight or -- better -- replace them with proper 3mm bolts. I had already done this long ago. Instructions ======== You'll want to assemble the MK8 as much as you can. You should wind up with a base plate, a handle, a spring, and some 3mm bolts made to go into the stepper. You won't need the gear and the bearing that come with the MK8. Instead, use the MR104ZZ bearing. It will fit fine. Here are some typical instructions: https://reprapchampion.com/pages/mk8-extruder -- again, fit your bearing, not theirs and don't worry about the gear or the bolts that hold things to the steppers (you'll use those bolts later). Now, remove all the bolts EXCEPT that one near the dog ear (near the Bowden connector). Now the stepper is hanging from one bolt, which is ok for now. Pull the plate straight up and put it away. The Bowden connector an bracket come away also. Now take a longer 3mm bolt and use it to temporarily fasten the MK8 base plate through the hole that has a little depression in the plate. This is the bolt that will be under the handle when things are done and you will want a shorter bolt there but not now. Make absolutely sure that the stepper is engaged on the bolt threads but keep it fairly loose. Do not tighten it down. Once you are sure the stepper won't get away from you, twist the plate as far away from the "dog ear" bolt as you can. The gear will keep you from getting it totally clear. With a little effort, you can take that bolt out now. Once that bolt is out, move the plate to its proper position and tighten the loose temporary bolt until the stepper is flush with the panel. Now put the two long bolts on the filament ext side of the base. Once they are in, remove the temporary bolt, and put in the proper bolt (which is quite short). Now you are almost done. Put the handle and the spring on, and be sure retraction works too. Done! ===== That's it! Sounds complicated, but it isn't so bad. The handle is much easier to work with, there are lots of printable accessories for things like flex filament, and the Bowden connector won't wiggle which makes a lot of difference. You might want to print out the Bowden clip from https://www.thingiverse.com/thing:1330497/, which I've included since Thingiverse requires me to have an STL. Good luck! Post Script: I didn't try letting the stepper motor fall down the tower, but it is possible it doesn't slip too far. If you note the video below, he is trying to hold it by the shaft with pliers and it slips but it doesn't fall so far down that he couldn't fish it back up with pliers. I didn't want to find out if mine would fall too far to rescue without pulling it up, and my method works fine, but you just in case, here's the video: https://youtu.be/TFO-qwQ8dLQ?t=629