Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

Right and Left Minimalistic Mk8 replacement - Modded

by Doogiekr, published

Right and Left Minimalistic Mk8 replacement - Modded by Doogiekr Oct 13, 2012
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Just a modified version of the original mk8 upgrade to allow me to use things that I had on hand instead of ordering / waiting for parts.


Update 2: Added versions for 623 bearing use (I do not have any 623 bearings so can't test it myself... please let me know if it needs to be different).

Update: Create one for the left side for those that have dual extruders and want to do both.

I was in my machine doing repairs for a thermocouple problem and noticed that my delrin plunger was worn. I did not really want to order parts and wait for them to come in to fix it so I modded the "Minimalistic Mk8 replacement" to fit what I had around the house.

I removed the spring and put a spot to use 3 "binder clip" arms to give the needed spring loaded pressure. I also adjusted the bearing area to allow for a 605 bearing (I had several in a bin full of RC helicopter parts), and made a printable pin that is a press fit through the arm and the bearing. I added a bit of a guide for the filament to make it easier to guide it in when loading.

Printed at 0 extra shells, .2mm layers and 100 infill. After it printed I cut the support away from the bearing area, installed the bearing and then put a drop of superglue on each side of the pin to make sure it didn't move after I installed it.

Have made a few test prints so far and it seems to be working quite well.

I only did the right side because I rarely print with my left extruder.

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Very nice! Keeping this in my spares section.

Amazing what a little ingenuity can do. Thanks!

I really like it.. Well done

Very impressive.. Really good


Would you split the Screws item to one file?

I am away from my home comp right now... will try to split it up once i get back.

I've been hitting my head against the wall for a few weeks trying to get my once working Replicator to print a piece I need; most of this time was spent adjusting the plunger!

Luckily, I was able to print a decent copy of this Thing and it's printing a lot better (but not perfect yet).

I didn't have any bearings handy but I did have quite a few brass screws and nylon washers. I managed to make the hole for the screw large enough by carving at it with larger and larger hex keys and tapped it for a 8-32 screw. I used a hex set-screw instead of a normal screw as the latter stuck out and made contact with the heat sink of the print head, preventing its reassembly. I used two nylon washers (sized "large enough") in place of the bearing and it seems to work okay!

Thanks so much!

Glad its working out for you... If you need it to be different, let me know and I will see what I can do.

I think my fix is slowly melting away...

I think my extruder fix is slowly melting away...

I have heard of issues with people making them in PLA... I made mine with ABS and they have been running strong for many months with no issues.

Turns out it doesn't fit my MakerBot Replicator 2. =(

Yeah... if I had a Rep2 I would ask MBI for a free http://www.thingiverse.com/thing:53125www.thingiverse.com/thing:5312... since they know its a problem

Spring-loaded Replicator 2 Drive Block
Thin Profile Whistle
by Madox

I found this under the remix.. trying to mod it to fit a 605 bearing

MK8 Extruder Rep2 Mod

If you dont have any luck, let me know and I will see what I can do.

Thanks for the offer. But I've already redid the whole thing in Sketchup.

Any Chance you can do me a modified Left version, I have a 628 (8x24x8) bearing I was just about to make a similar extruder but as you appear to be a few hours ahead you could save me the ear ache from the miss's :).

Its only a single extruder from a Rapidbot so I think its the same size stepper motor having a quick look

did you ever get it to work with 628s?

I will give it a shot

Thanks, ill have a quick play my side too see if we can get this massive bearing to fit

How to you fit this together? Does it require additional hardware parts or is everything printed?

For the original version (the one I use) you need a 605 bearing for each side as well as 3 of the binder clip arms (as shown in the pictures). There is also the version for the 623 bearing, but I never tested that, it was a request from someone in the comments.

Thanks. I'll have to procure the bearings somehow. What about the screws?

The version I use (the one pictured) does not require any additional screws, just use the 2 that are already there. This is the main reason I made this design, so that I could just use stuff that I already had (I had the bearing and the binder clip arms).

This is awesome! Thank you so much. My replicator is working like a dream again. Don't have to watch it like a hawk waiting for a jam.

Happy it worked well for you... it has been working well for me since I installed it on my Rep1.

as luck would have it.. I was looking at these mods for the exact same reason .. started printing with PLA and BAM.. no more ABS for me at the mo.. this printed out amazing .. I had the exact bearing from a Dremel teardown and it all snapped together flawlessly. Doogiekr, you are a champion.. I had the Bull clips handy and was able to make this without spending a cent!! well done on a great idea!!

Glad it worked out for ya...

you need to post the .scad or whatever you used so that we can change the bearing parameters

Added my original files as demanded...

Thanks so much! Great Work!

Where's the file for the plastic pin hinge you used to put the two pieces together?  Thanks.

 Thanks... Emmett is the real genius, I just took his design and made it work for what I had on hand and needed it to do.

Very clever! The binder clips look like they're probably more secure in position than the springs (which, at least for me, don't feel securely in place), and are certainly easier to source. It's odd that while bolts and nuts are standardized, springs appear to be randomly designed by each manufacturer. And binder clips, while not technically standardized, are easy to pick up for almost nothing at any office supply store. Yay!

And adding a 'guide' for the filament is great. The only problem that I have with the minimal extruder is that it's a little fiddly feeding new filament in, and this might help.

Huge thumbs-up, you made a good thing even gooder! :-)

Yeah, the binder clips are very secure... there is no way they are coming out of the arm without alot of help from the user. I never made the original one, so not sure how much different mine will be, but I read somewhere on the makerbot operators group that a little more filament guide would  be nice so I went ahead and added it while I was doing the other changes. I rounded a few corners and changed some spots that looked they could benefit from being stronger as well.

Will a standard rollerblade bearing work in this design?  I'm not sure if those are 608 or 605's.

If you let me know what number you want to use, I can digitally "replace" the bearing and see if it would work.

Without knowing the size I am not sure... The roller blade bearings i had in my house were way too big, but i am not sure if there are different sizes out there.

I've been working on this in Sketchup, removing the supports you explained you cut out after printing, etc.  

I found some 608 skate bearings. The dimensions you asked include a 7mm width - easily allowed for - however the 8mm inner and 22mm outer diameters are a problem. I don't any amount of redesign would fit the 22mm diameter. Thoughts?

Got some smaller 688 bearing arriving tomorrow.  So I'm sorted, hopefully.  :)

Yeah, thats why I did not use rollerblade bearings that I had here when I made it. 22mm "might" be posssible in a single extruder setup if thats what you have, but in dual extruders the bearings would hit each other in the middle. I mocked it up in Spaceclaim with both extruders to check clearance and the 605 bearings that I used were already kind of lose, but there was enough room... the rollerblade bearings did not have even close to enough space. If your running a single extruder then I should be able to get it to work for you though.


I have the original mk8 minimalistic replacement, so unfortunately all I have are the little 623 bearings.  

Would you be so kind as to make a variant with the same solid arm and pocket of the original?  the design you came up with is brilliant, and I'd like to upgrade to it.   


I downloaded the specs for the 623 bearings, and I can make them fit easily... my concern is the printable pin I used for my version has a 5mm center for the bearing. The 623 bearing only has a 3mm center from what I can see... this means that the printable pin might not be strong enough for the pressure. It might be better to use a bolt in this case, is that ok? if so, do you have a specific bolt you have in mind so I can tailor the part to it?

I will take a look and see if it will work, and if i can i will do it.

Bolt is fine!  if you leave a 2.8 mm hole on either side of the design, I can just put a screw all the way through the design, and have it embed on the other side w/o a nut.


 Done, I made it a 2.8mm hole as requested, and moved it towards the filament because of the smaller bearing. I mocked it up with a digital 623 bearing and it looks like it should be fine, but let me know if it needs adjusted. I can't test it myself because I don't have any 623's here.

was asked what size binder clips i used, not exactly sure so I just took some pictures with a cm/mm scale for ref

love the binder clip idea. Got me thinking about using the clip part somehow...

My first thought was the spring from a clothes pin, but couldnt figure out how to get enough pressure from it. The binder clip arms have alot of spring pressure, so they were my next choice.

Very nice and practical improvement! This should encourage people to  try it with easily sourced parts. 

That was the idea, well for me anyway...

Made a left one for those that want to do both sides

Interesting source for springs!

like I said... using what I had around my house =) ... they work very well for this purpose (and others,I  love binder clips)