After about 500 hours of printing reliably, my Makerbot Replicator 2 finally barfed. I walked in to a 4 hour print completion that looked like this:
Woah. When you walk in on a print failure like this, it’s important to root-cause the problem, so that you can prevent it in future. Not only did I lose about 4 hours on this job, but also about $5 in PLA. I looked over the printer first to check for the usual problems – extruder head movement restricted, PLA feed issues. Nothing there, so I took a closer look at the piece. I noticed an interesting pattern:
Notice how the problem started at a certain layer – that is not really interesting; notice instead how the layers above the break point are basically intact, just shifted over to the left (along the X axis). A couple of possibilities:
- A problem with the SD card or the X3G file on the SD.
- Corrupted firmware (on how it controls the X axis)
- Problems on the X axis travel (bad lubrication, loose drive belt)
First I took a look at 1 and 2 – the software problems. I looked at those first because those are the simplest to fix. I reformatted the SD card, re-built the X3G file and reset the printer to factory defaults. Then I kicked off the same print job and noticed the problem in action (thankfully it was very easy to reproduce). Here is a video of the issue:
Hear the THUNK THUNK? That is the head either stopping without deceleration, or step skipping. This is what happens on the print:
The squiggly line is where the steps are skipped. This means that you loose alignment between layers. You can see it more clearly in this larger photo:
So this makes the printer basically useless. Bummer. I started digging around and found a great YouTube video by forbinone that describes the same problem and gives a very simple fix. Basically, the problem is that the X-axis servo cable, from being too tightly crimped in the factory, and the thousands of forwards-backwards cycles, causes some of the cores inside the cable to break. That means skipped steps. The solution of course is to replace the cable.
Once you remove the right-side MDF from the Replicator 2, you can see the problem in the X-axis stepper cable (light grey ribbon cable) – it is crimped far too tightly.
Mark the point where the kink in the cable forms (in the diagram above, the problem space is at the blue mark on the cable near the top-right of the picture), and then remove the little bar holding the cable in place to free the grey cable. Ensure the black ribbon remains in place (it is for the homing switch and does not suffer this problem), and replace the little bar.
Now you just trim away the problem section of cable, and splice in some new ribbon cable. To ensure the splicing did not lead to any shorts across the four wires, I decided to use some 0.1″ headers.
Then add in the new section. Be sure to add enough that there is no tension in the wire – there should be enough play to allow the X-axis gantry it to move smoothly forwards and backwards without getting tangled anywhere. It is critical to ensure you keep the polarity correct – that is, don’t accidentally flip the splice so that the leftmost cable on one end of the original ribbon is now connected to the rightmost cable of the ribbon. That could badly damage the printer.
To ensure the new longer section did not get tangled into the rest of the machine, I cable tied it to the front-right vertical beam.
To finish up, I added some insulation to the joints, and bolted the MDF back to the machine.
It definitely looks a little war weary, but after the operation, it runs perfectly. I did the same 4 hour part again, and it came out without any issues:
Thanks for the in-depth description! I believe our Makerbot Replicator 2X is suffering a similar fate. Do you by chance know the exact 0.1″ header you used so that I can pick one up at Radioshack? Also, did you need any tools to get the wires to come together properly?
Thanks!
The 2x has the same gantry design as the 2, so this is likely. You should be able to confirm this by extracting the cable from the clip, and then jiggling it by hand as it prints – if you can cause the skips by jiggling then this is the issue. 0.1″ headers are standard, so any of that pitch should work – be sure to get one set male, one female, and you will need to cut them to the rigth number of pins yourself (you can do this with an exacto or hobby knife). To get the cables connected to the headers you will need a soldering iron, so that you can solder each strand to one of the pins. If you are not good at soldering, you could try going to an electronics repair shop, explain the process to them, and see if they will fit the headers for you.
I think we’re having the same problem on our 2X. I want to replace that section of cable, but need to replace the female plug that plugs into the stepper motor as well. Where can I get that?
Just found the answer to my own question, in case someone else needs it. http://www.robotshop.com/en/replicator-2-2x-jumper-cable-x-motor.html
thanks Ron
THANK YOU SOOO MUCH! I had to make some 12h prints and two of them are failed in course of this cable-error. Now it works great!
Great write up, thanks! With 1700 hours on my 2X, it started doing the same thing. I should have Googled before I tried tightening the belt, cleaning and lubing everything, re-flashing the FW and SD card, and then tore the printer completely apart 🙂
Thank You so very much for this fix.
I started to get some really odd failures with layers shifting and was
thinking belt. But before buying a new belt (mine is getting old) I did a bit
of searching and happened to find this post. Your description has my issue
nailed. So I guess I will be repairing a cable and not doing belts.
Thanks Again.
I have been on a 5 year break from 3D printing, but before I took the time off I ran into this same issue. Going to fix it now and start printing again. Thanks for keeping this post up all these years!
I got a heavily-used Replicator 2 from a friend and have been spending hours trying to get slicer setups that work since the old Makerbot slicer won’t run anymore. I had all sorts of problems with other people’s bogus startup gcode recommendations, so when I started getting skipped steps, I figured it was yet another problem in the generated code.
After about a week, I figured I’d play dumb and ask the internet. Maybe there’s a failure mode that’s characteristic of the printer after a lot of use. A thousand generic, vague, probably AI-generated “help” articles later, I accidentally found your YT video while actually looking for something completely unrelated.
If it weren’t for this blog still being up 10 years later, it probably would have taken me another week to even shift my focus completely to hardware faults. I miss the days when the web was searchable.
The cable had a break in it exactly where yours did. There was even a tiny pinhole where the arcing had burned through the insulation. I replaced the section of cable from the midpoint of the pillar up to the motor. I used a connector so that the replacement cable could simply be replaced without any soldering on the device. I routed everything in the original path, but I used a couple layers of ribbon cable instead of one. That gives some redundancy, and when it’s taped together, the three layers support each other and tend to bend uniformly instead of just at the clamp.