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Prusa Original i3 Mk2 Cable Chains

by timsaucer Aug 18, 2016
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Hi, first of all thank you for this design.
I was wondering if I am the only one having issues with the heat bed chain that hits the bottom right corner of the printer (basically the corner that supports the horizontal rod on the side where the chain is.
Is there an easy way to avoid that?

This was my fix..

3mm thick plastic washer under the heat bed wire mount. Gives it just the right amount of clearance and the chain actually moves better.

Few notes.. use the new RAMBo cover with the 5mm lift, and DONT use metal washers for this mod... I repeat don’t use metal washers. Should be pretty self-explanatory why, but I also just want to mention it as another Precaution. :)

Thanks for the tip!

I think the only way I can avoid that is if I redesign the head bed chain mount to have a vertical offset.That would also entail moving the clip on the circuit board enclosure. I don't think that would be terribly hard. How large of an offset do you think you need? On mine it doesn't hit often and when it does it hasn't interfered with the printing, but I can see your point of wanting more clearance. I can make a change and upload it if you're willing to test it. I'm switching my printer to a CoreXY so I won't be able to test it.

What about raising the enclosure plug of about 5mm? Assuming that the chain has enough torsion to flex, that should automatically raise the chain enough not to touch the corner anymore. That way there is no need to redesign both ends, and current users would only need to reprint the enclosure part while they could keep the rest of the parts.
Do you think that would work?
Btw I can of course test it!

Ok, I uploaded a rambo cover with y clip raised 5mm. Let me know if that works. I'm not crazy about where the vertices are inside the model but it sliced okay for me in Cura.

Hey, is it me or the new model is actually 5mm lower rather than 5mm higher?

It looks to me like I moved it the right way.

Ah right, I messed up with the model names during the comparison so I actually thought the old one was the latest one and vice versa, sorry for that. I'm going to print this over the weekend, I will give you a feedback as soon as it is in place!
Thank you so much!

Hey, so I just mounted the new enclosure but I have to admit that it didn't change anything, actually, I think it makes it a bit harder to open the door of the PCB enclosure cause it hits the chain and you need to bend it slightly. Honestly I don't know if this "issue" is also present on the default design as I had no door when I first tested it.

Hello there maker and remixers -

I am making this presently for a mk2 I borrowed from a friend. Thank you for putting the time into this design. I am excited about it.

Is the remixed x-axis holders a good idea? does the default one disconnect?

I am printing this as well. I chose to use Tig3rch3n's remix, as Ubikus's broke on me rather easily. So far no problems, but I have yet to print off the chain links and actually give it a test drive. I didn't try the default.

I hope you find it helpful. It's odd - my original design I had on my machine for over a year with no problems. I ended up reprinting it after I did something stupid and broke it off. Since then I've gone through 2 parts that broke quickly. That's definitely a weak point that probably needs to be reengineered. Unfortunately I don't have the time to work on it. I hope the remixes work for you.

Sorry but I must say it. The design is totally shit. I regret the time I spent printing it and assembling. So many issues that even blind person noticed it.

I'm sorry you feel that way, though I suspect your opinion is in the minority based on the feedback I've received here and other channels. Best wishes to you.

I'm sorry for my rude comment. I was a bit angry :D I printed piece after piece. It tooks me lots of time. Then abrading it and assembling. I left it for couple of months lying on my table waiting for the right time and looking forward to it. Then I disassambled my printer, change it and realized what's wrong. The end stop not working when the Z-axis is in top position. The X-axis motor is in collision with the chain as well. So I had to change it back to the original prusa chain. I will leave it for months now. In fact, apart from the mentioned issues, it is nice model.

I understand. It can be very frustrating. The one down side of the Mk2 I've realized is that there is no room to spare. The clearances on everything are very, very tight. I hadn't noticed the end stop problem. I've got a print running now that will take another day and a half :) but after that I'll investigate. I really wanted to modify as little as possible on the original design, but I fear I should have gone a little further with the mods. I haven't had a problem with the x-axis motor. It does touch which is annoying but hasn't been a problem during printing.

I noticed that my x-axis chain has a slight bend to it, likewise it puts extra stress on the simple top part and usually causes it to break. Any idea on how to prevent the added stress on the top part? Likewise, the y-axis chain is giving me some issue because I can't get the wiring through the heatbed mount, the plastic end clip on the heatbed power is screwed together very tightly. Thanks again for any help, your design is wonderful!

Sorry about the delayed response but I've been traveling a lot recently. Do you mean that as you look down at the chain it has a curve to it? This is known to happen on printed cable chains. The issue is in the calibration of the printer. Some people get around it by rotating the prints of the cable chain parts. They print 4 at a time, rotated by 0, 90, 180, and 270 degrees.

About the heatbed attachment, I don't have the time right now to modify the design to open it up, but you could probably clip one of the vertical parts and have it work fairly well.

Hi Tim, great design, printing now and look forward to installing.

Great to hear! If you have any trouble with the top part try one of the derivatives. I've never had a problem and logged many, many hours with him (including a recent 51 hour print).

I have a MK2 and the "simple_top_part.stl" prevents the X dead stop from triggering because it pokes into the rambo box cover. Not a minor amount either, it needs about a half inch removed from the cover for it to hit the dead stop. Everything else works great.

Hi Jason/Tim

I had the same problem, so i re-engineered the mount to the X Axis Carriage,


it helped me, hope it helps you.


Prusa Original i3 Mk2 Cable Chains MK2S X-Axis Mount Kit
by kraq

I was just assembling my printed chain and realized it was not adapted for the mk2s. This helps a ton!

I did the same thing =P.

I had everything installed on the printer, so I simply zip-tied the first link to the long bolt on the back of the extruder, it held up enough for me me to print off the adapter prototypes.

Is it hitting the box or the frame? When it's nuzzled firmly up against the carriage it should slide in front of the frame. I had some issues when originally designing it and I didn't have it pushed all the way toward the front of the unit. If the back part of the top part is hitting the rambo box, can I ask what material you're printing it out of? I'm wondering if stiffness is an issue and this part does need redesigning.

On my MK2, the rambo cover is flush with the metal frame on the left side, so the chain link that mounts on the hot end sticks out too much. When a chain is attached, it becomes even wider. When I first mounted the cabling, X end stop didn't get triggered so the MK2 kept trying to go left, making loud noises.

I think I'll need to modify the rambo cover to have an indentation in it to allow the end stop to trigger

Okay, I understand. The intent was for that part to have some flex to it. I'm going to have to rethink the design. The arm is supposed to bend slightly to the side when you are at the very limits in the x direction. Clearance on this thing is a real pain. Originally I had designed a two link system that would rotate out of the way, but it became even more difficult. I have an idea on how to fix it once I have some time.

This is a good idea. Once I have some free time (probably not too soon) I'm going to tackle that top part again. I think I need to go somewhat back to my original idea of having two simple rotation joints on it so it can move out of the way. I do like your design though. Would you mind (once you've printed and are happy with it) if I add a stl of your rambo cover? I'd include attribution in the remarks.

Comments deleted.

Some constructive criticism. I printed the recommended 32 links for the extruder chain plus 1 full rotation link, to find that it was 9 too many. Fortunately, I was able to use those 9 for the bed, to which I am printing two more links, and a full rotation link.

Additionally, the "simple top" piece has a couple of flaws. First is that it needs more fillet between the vertical tabs. This will vastly strengthen the part. It also hits the Rambo box when it homes the axis. To fix this, I would recommend reducing the border around the indented area that captures the chain link.

Will give further comment, if needed, when I get the bed chain completed and installed.

Great design, thank you for your efforts. Way better than the stupid flex plastic that came with the Prusa MK2.

Thanks. I think there must be some differences in the cable lengths people received. Based on your feedback and some I've gotten elsewhere it's not completely consistent. I'll update the comments to reflect this.

Good points on the top part fillet. I wanted there to be some play in the part. This was to avoid trying to put a rotation in the piece. The original "not simple top part" was way too complex. While not perfect, this was a big improvement.

Mine doesn't hit the Rambo box though. Let me know if you have rubbing of your heat bed chain against one of the zip ties. I don't have this problem but someone else does.

I appreciate the feedback. Right now not sure how much time (or willingness) I have to work on it. Still considering making a chain for the X cable as well.

X Cable? You have that already. The X axis is the extruder. Y is the bed, and Z is the vertical. I'll assume you meant the Z and hit the X key on accident. ;)

An alternative fix for it hitting the Rambo box would be to shrink the rambo box cover slightly. It's interfering somewhere around 1/8" of depth.

The x axis motor is the one with the cable wrap on the left. Sorry, I was thinking in terms of the electronics.

My bad, I had a brain fart and was thinking the 'x' was the extruder.

Yeah, doing the x-axis would be great, but in staring at it tonight, I'm not sure how you'd mount the chain top, without modifying and making a new x-axis motor holder/z-axis guide.

11 normal links and 1 universal link worked spiffy on the bed.

Btw, I when I did the extruder, I wasn't looking at what cable lengths I had. My only concern was how much did I need mechanically to get full travel vertically and horizontally from the extruder. That wound up being 23 normal links and 1 universal.

I'm really liking the way it's working. It no longer looks like a cheap arse piece of equipment, but a well designed machine.

I dont know if anyone has made anything yet, as I have not looked... But, I would like to see some sort of fan for the power supply. It may not need it, but it would make me feel better....

I've never had an issue with power supply heat and I've logged many, many hours on my unit. I've run some prints that are up to 30 hours at a time. Given, I've kept mine in a basement and live up in Michigan where it keeps it very cool. Actually, I'm in the process of building an enclosure because mine gets too cool in my new home.

Just picked up another Prusa Tuesday that had a ton of issues and the kit buyer couldn't figure them out, so I got a deal... Printing up another cable chain set for it now. Was having issues with the 30 degree or so incline as the parts are printed, so I'm using the 0.15mm Optimal settings, reducing the perimeter speeds by 25% to see if that helps. Extruder at 195C, bed at 60C, Inland black pla.

Second set of cable chains, second broken simple_top_part. Can you send me the cad file so I can add a fillet between the vertical tabs?

If you're still having a problem with this, someone made an improvement:

i3 Mk2 Cable Chains reinforced X-Axis holder

Still not robust enough for my liking, so I amended it further.


It's not a parametric model, so if you import the stl into your editor you'll get the exact same thing as the blender file I was working on. I can upload my blender file but it really won't be any different.

This is great stuff man. Thanks a lot for your work to make the enclosure and bed cover... the whole package! I'm almost done printing the links (on last set of 12 now) and excited to install the cable chain.

Thanks! I'm really glad to see someone other than just myself is using it.

Is there parts anywhere for the third bundle on the left?

Sorry, I didn't model that side. My main concern with the other two was their movement near the heatbed/workpiece. Since that was way off to the side, I didn't bother.

Understandable :)
I'm trying to minimize the footprint for a enclosure, and those cables keep poking to the side for me...
I was thinking that I might be able to fit something with a longer bolt from the circuitboard by that bundle, that way adding a third chain without having to remix your great design :) But I need more training modeling before being able to achieve that :)

You may not even need to do that. You could potentially keep the cable wrap as it is and just tuck it forward when you put the enclosure around it. The cable wrap would then be aligned along the Y direction of the carriage. It may rub against the enclosure, but it would only be the wrap not the actual wires rubbing. I did think about the other cables on the side but I didn't think of any simple way to make it work and I didn't want to do a lot of modifying of the parts that come with the kit. Actually, I was trying to make it so my model could be removed and keep the original if needed. The real problem I was having with that side was thinking of how to best mount it to the X motor carriage. For the other end, there are some unused holes on the frame that you could potentially use. You would need to be careful they do not interfere with the full motion in the Z direction though. Please let me know if you come up with something good!

Where are the full rotation links supposed to go?

They go on the ends of the chains closest to the heat bed and extruder.

Is is possible to re-upload "simple top part taller"?

The "simple top part taller" stl does not show any content on my end. Please let me know if you see the same. I have the other 4 parts.

I don't know what's going on. I just redownloaded it from thingiverse and it opened fine in two different programs.

Will the EL on the X-Carriage interfere with the Quad extruder upgrade? Also, a more thorough discussion is here: http://shop.prusa3d.com/forum/improvements-f14/mk2-cable-chains-t1538.html

I'm not sure. I don't have any plans to make that upgrade, so I doubt I'll put any more effort into this mod.