3D Printing (Part 4)

Part 1234567891011

Arrrrrrrrggggggggggllllllllllll !

What the hell is this awful noise from the X axis stepper motor? The moving head turned to a shaking head, and the printer sounds like a bear which has been woken up before spring.

For some reasons, I could not find a possible cause for this disaster on the Internet. Not before I identified the defective part. Once you type “Stepper motor”, “ribbon cable”, well, you find quite many people who experienced the same problem before (Any type of Replicator).

I will not go into all the details of the diagnostic, except for saying that it is very easy to swap the stepper motor drivers which are built around a fancy Allegro chip, mounted on a removable PCB. Checking the continuity of the harness is not very easy as the connectors use thin pins. Care shall be taken not to destroy these connectors with sensing probes.

The origin of the problem is the ribbon cable which crawls beneath the upper right hand side of the printer for feeding the X axis stepper motor and contact. I have been pretty lucky to see the small puncture on the cable, showing exactly the place where the wires were broken.

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In fact, what happens is that the electric wires break one by one because of the stress that they endure, so that all the current (up to 2A) goes through fewer wires which get hot and finally burn (a careful inspection at the cable section shows that the place where the wires where is brownished).

Repairing a ribbon cable requires few pieces of shrinkable tubing and some soldering skills. It might be risky for you to do it  if you do not have a soldering station and a good iron and some experience at soldering very small parts. Here are a few pictures which are self explanatory:

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Well, my soldering technique is better than my picture taking skills 😉

Finally, I tried to think about something for preventing other bends and cracks. Simple solutions are often the most efficient, so that I simply sandwiched both ribbon cables between two styrene strips. Here is a picture at rest:

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And here is a picture when the cable is fully bent:

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Short term tests show that the printer is working nicely again 😉 and only long term test will demonstrate if this modification is effective or not. In any case, I strongly suggest to the  Makerbot people to bring a significant change in design and/or quality of cables as this failure is unexpected after only 200 hours of printing.

HTH

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