Broken wires due to cable fatigue: Is there any long-term solution, like a refit kit, for dealing with this?
 
Notifications
Clear all

Broken wires due to cable fatigue: Is there any long-term solution, like a refit kit, for dealing with this?  

  RSS
J
 J
(@j)
Active Member
Broken wires due to cable fatigue: Is there any long-term solution, like a refit kit, for dealing with this?

We've got three Prusas where I work: Two MK3s and one that's either a MK3S or a MK3S+. I'd say they get moderate/heavy use. They are all factory-assembled.
I also have a MK3 at home, built from a kit. It gets fairly light use.

Internal wire breaks from cable fatigue have plagued these printers. It's a continuous-flex application, and the wires used just can't handle it.

-- I've seen a few other posts about this problem here, but I was wondering if anyone knows of any third-party continuous-flex-cable refit kit for mitigating this?
Right now all I can do is keep splicing or replacing wires as they break. Some can be bypassed or ignored temporarily, like an RPM-monitoring wire, but a broken thermistor wire means no printing until it's fixed.

Within the first year or so of operation, I've had these wire-breaks across any of the three printers:
- Print blower fan: RPM wire on one printer, and power wire on another.
- Print bed thermistor (two breaks were found in one wire).
- Print head thermistor.
- Filament sensor.
- Possibly one of the extruder motor's wires, but that printer's thermistor wire broke before I could be sure.

Wire breaks happened with the spiral-wrap wire loom as well as the textile-wrap style.
The breaks weren't all at stress points where the cable ends attach to the printer. Some happened near the middle of the cable bundle.

Even my lightly-used MK3 has had wire breaks in its filament sensor and print blower fan.

I'm attempting a wire-splicing using multi-conductor cable that's rated for continuous flex, but everything in the printer design is so tightly compacted that it might not even work: There's just no room anywhere for the sizable bundle of wire and splices, while still allowing the print head to reach is normal working volume.
The only other thought I've had is some kind of breakout board that would attach to the back of the print head somehow, and another breakout board at the controller: Plug all the connectors from the print head into the breakout board, and then connect a continuous-flex cable between them. Has anyone made anything like that already?

Or I might be looking for a different printer brand, something that at least uses wires rated for continuous flexing. Intermittent problems can damage or completely ruin long print jobs, which is unplanned downtime I don't need; same with replacing broken wires and cables.
I like these printers just fine otherwise, they're good workhorses, but the breaking wires is a persistent problem.

Posted : 21/01/2022 6:09 pm
Zoltan
(@zoltan)
Moderator
RE: Broken wires due to cable fatigue: Is there any long-term solution, like a refit kit, for dealing with this?

Did you try to contact technical support and discuss with them the issue? 

even an old man can learn new things 🙂
Standard I3 mk3s, FW 3.10.1 RC1, MMU2S, no closed box, Fusion 360, PrusaSlicer, Windows 10
PRUSA MINI FW 4.3.4, Prusa Connect Beta

Posted : 21/01/2022 6:58 pm
J
 J
(@j)
Active Member
Topic starter answered:
RE: Broken wires due to cable fatigue: Is there any long-term solution, like a refit kit, for dealing with this?

I did back when some of the wires originally broke. I was sent a new blower fan and a new filament sensor cable. They have since had internal breaks as well from the constant flexing.

I don't know where to take things though when there's an issue with the design itself, especially if it only affects a small portion of their customer base.

Posted : 21/01/2022 7:58 pm
Diem
 Diem
(@diem)
Noble Member

Prusa themselves make very heavy use of their printer farm so they must have considerable experience in this area...

Contact chat and explain the issue.

Cheerio,

Posted : 22/01/2022 1:38 am
Share: