Rigid MK8 Mount with through body part fan and capacitive bed probe holder

Just a design im kicking around. I made a blank tool mount file a couple weeks ago and decided to start start building on it. There is nothing wrong with the mk8 mount from allted, I just found it to be a little wide and bulky, especially when i started trying to come up with clever ideas to add my capacitive bed probe. I figured with id start by adding rigid support for the motor and extruder assembly, then it dawned on me that i could shrink the amount of filament needed and add a through body fan duct. Please feel free to try it out and give me your feedback.




Slick I like it!

Part fan works so good I have to run it at 50%.

Very nice… but 2 questions:

  1. The hotend doesn’t make goo out of the part that’s nearly touching it?

  2. Why is the filament lever in the back?

I have been working on something similar over the past few days, but the bottom of mine kind of looks like a flying saucer :confused: still have a lot of finishing touches before I can actually print it… like deciding where I’m going to stick the spool of filament :confused:


A: no, i made a small indent ion for that, and if it was a problem I could just spin the heater block 90 degrees and gain like 10 mm of clearance. And the through body fan could actually be keeping the plastic cool. but so far no problems at all.

B:because that’s the way my extruder faces. they make them in both directions. i don’t actually use the lever I just feed and let it pull it in. this orientation let’s me see the entire hotend from the front of the machine.

FWIW, attached is what I have so far; I plan on wrapping the whole bottom with ABS, and using the “cutouts” in the heatsink as the anchor point for the extruder… still working on the duct work to get that rear fan to blow on the nozzle… now I see why car makers use clay… soooooooo many measurements :confused:

For some reason people seem to think that pla can’t handle being less than a foot away from the hotend. fwiw I’ve been using a blower fan since v1 with a pla duct that actually made contact with the hotend and aside from a tiny bit of warping where they touched it never caused an issue. your part looks great, but it still has the entire extruder dependent on 2 screws at the bottom holding it up. ive seen issues with second and third layers slightly warping and colliding causing vibration. I like your idea about using the fins to anchor your shroud to, I was using a shim plate before to attach my bed probe and found that the heat sink isn’t very “secure” when it comes to angular torque. see the fans mounting holes are 32mm on center and the nemas mounting holes are actually 31mm on center, which means that there is a lot of slip on that 2 1/2 Inch screw. i would have problems where my probe would be dead on for one print them drive into the bed on the next because the weight of the probe was being tossed around on fast moves. my part has solved all these issues and given me a good part that can be removed and replaced with ease, without worry that my probe will have to be recalibrated. And I don’t have to takeoff or lift up the fan to get at the mounting plate. plus I’ve gained about 10mm on my X axis and 6 or 7 on my Y

More random printing footage

Thank you very much for sharing your design. I may try to make this the first thing I print on my mpcnc when I get the electronics installed. I am getting close.

If you can print the cnc universal mounting plate then you should be able to print this it’s kinda tall but I kept the size down to a minimum. if it is too wide and you don’t have a capacitive sensor, you could always cut it off in tinkercad.

Can you talk a little bit about your filament guide setup? Just curious where/what fittings etc you are using at the extruder and from your roll. Like the setup.


Here is a link to my Bowden guide.

Sorry for the late reply I was never notified of your post.

Basically I’m using the ptfe tubing to direct the filament so it doesn’t get bound up on anything. it’s a push fit connector on each side with the Bowden supported between them. thus way the filament is only pulled by the x-axis motion. i have my spools affixed to the front of my table just under the Bowden tube end. i may rework the design in the future to add a filter/lubricator. but for now it works perfectly.

Oh and the pushfit connectors are 6mm threads

Is anyone using this yet? Id like some feedback. Ive been spending some more time getting to know onshape, and ive been working on improving this file. And i added some more printer friendly internal geometries as well as a couple of wire tie hooks on top. Let me know if anyone is interested and ill replace the files i have up on thingiverse with the newer files.

I made one, it’s pretty good. Thanks for making it available. I did remove the sensor bracket bit, because I’ve mounted my sensor in the spoil-board as I already had too many wires leading up to the Z axis mechanism. I did have to attach a chunky piece of aluminium to the bottom of the stepper for it to be close enough to detect Z-0. I just think of it as a heat-sink though.

Things I’ve thought about:

1/ It would be nice if there were holes for using zip ties to tidy up the writes leading up.
2/ My nozzle is higher up than shown in your photos, because I’ve got the filament entry port as close to the stepper gear as I can… So I’m not sure the angle of the fan outlet is correct for me. I have not printed too many things yet, but the calibration cubes did come out nicely so it’s probably ok, though as I print taller things that may change.
3/ The filament spring lever is awkward to use, I should have bought a reversed one but I don’t see any local ones available where I live. I’ve loosened the spring a little to make that easier but I’m yet to see if it’s too loose to keep grip of the filament.

Oh, and I printed it in ABS but the rest of the MPCNC is PLA so the different shrinkage did make the attachment holes a tight fit until I drilled them out a bit. That’s an easy thing to fix though, and nothing to do with the design.

Edit: Oh I see there are now tip-tie holes. How about some leading up too?

im working on how i need to direct the wires up the side, so i havent gotten that clip designed yet, although i dont think itll be neceessary since the motor wires dont really have that far to go before they hit the top of the mount. On your list of things there are some things to note. it could be a difference in throat height from different distributors, i too had my throat as high as possible to alleviate filament grinding, and have since added some filament guides to the extruder for that and that has pushed my nozzle down, but the pictures are of the extruder with the troat as high as i could get it. if you use a reverse filament lever then the hotend will not line up with the air duct. I personally dont use the lever unless im forced to manually drag the filament out of the extruder, instead i just have the extruder do the feeding itself. i did make the mount holes slightly too perfect in size and some of my screw heads try to bind up there, but its really not a huge issue, I am going to add another .1 to the hole size there. I have also made the extruder motor mount wall slightly thinner, because i had to get longer screws to hook up my extruder fan and heatsink reliably, and then i had to cut the screws down because the next size up is too long, which ultimately led to me striping out one of the steppers threads ;( I may even produce a few other versions with inductive probe mounts and even one with no probe, but I am still learning onshape and i find that once something looks nice and works its hard to convince myself to make any changes to it. i was thinking of getting an e3d hotend and i may also make a version to accomodate that.

I have had great success with the original design, and as ive said before, one should always start with low fan speeds, because for some reason this thing works incredibly well at pumping out cold air, i cant even get over 50% speed out of the fans im using without it actually peeling layers off. So i have been toying with the notion of adding some circular geometry to the duct out nozzle to spread the air out more evenly. but that may take a few more onshape classes.

My extruder is sooo cheap and crappy. The filament hole in the lever arm is about 2mm too much towards the fan side. I’d drill it out, except that it wouldn’t be a new hole on its own, as it would join the current one. I guess I’m just saying it would be little wonder if they sourced a shorter throat to save 2c since they spent no money on quality assurance. I didn’t even get a little screw to hold the thermistor in place, lucky I had the perfect size one lying around.

Yep, I had to use longer screws too. But luckily I had ones the right length and didn’t have to cut them. I did use a printed fan grill and not the metal one it came with (which I used instead on the cooler fan) because the screws I had wouldn’t fit with that on.

I do like the idea of a bigger fan outlet with fins that spread the air, but for me, if there’s a problem, I’ll just file the shape of the outlet a little. Thanks again!

im not going to change the duct design for now, maybe in version 2. I have updated the blank 525 mount part that i have on thingiverse to give some more clearance for the mounting holes, and likewise for the mk mount. I am currently printing out 2 new mpcncs and they will both be using this mount for the extruder once i get the new part printed (could be a couple weeks) ill post up the new part on thingiverse. until now if anyone wants to give it a try they can view the part on onshape (at least thats how i think it works) from onshape.

just right click on the left where it says part1 and select export to get an stl.

got a little more in depth with section viewing and got inside the part to close up some potentially problematic voids, and added some smoothing fillets to sone vertical overhangs to ease the printability. If nothing else this project has gotten me to dive in headfirst into cad modeling. hopefully i can get something printed soon and release the newer files. I will say this, it will take more time and filament now, since i closed down most of the ducting, but it will(should) print better and be slightly stronger. hopefully closing down the duct will make it easier to dial in a good fan speed.

Got the internal geometries tightened up a lot. its coming together pretty good now. now i need to find a program that can add supports manually and save them out to an stl so i can put it up on thingiverse and not have to worry about all the “how am i supposed to print this” comments. even though i had no real issues with the excessive bridging on my mpcnc, but others may not be that lucky.

Havent had a chance to print the new models yet. but i have updated them to thingiverse. I even added a model with no probe holder for jasoroony.