MakerBot Industries

You don't need to repeat my mistakes...

Stupid mistakes you probably won’t make when assembling your Plastruder MK5

• I can’t believe this – but I actually mounted the drive gear upside down. ¹  There were three symptoms of this problem.  First, I  couldn’t hand feed the ABS filament.  Second, no matter how much I crunched down on the filament with the thumbscrew,² the filament would extrude about 1cm or so, nothing for 30 seconds, and this cycle would repeat.  Third and finally, when I pulled the filament out there was a bizarre pattern of nasty chew marks and what looked like stretching on the filament.  These are not the sort of marks I would expect to see from this drive gear with its super small teeth.  The first symptoms was caused by the wider base of the drive gear obstructing the filament path and preventing hand feeding.  The last two symptoms were caused by the set screw on the gear biting into the filament about every 30 seconds, forcing the filament down a little ways, and then just rubbing against the filament with the smooth part of the base of the gear.
  • I spent an embarrassingly long time puzzling over this problem before figuring it out.  Even after I realized what I almost certainly had done, I couldn’t believe I had installed the drive gear upside down.  Alas, it was true.  Fortunately, the fix was simple – unbolt the motor, pull off the drive gear, drop it back on, tighten, insert motor, bolt it back on.  All extrusion problems magically melted away.
• I replaced my most severely warped threaded rods on my ‘bot but encountered a bizarre problem.  Even after leveling the Z stage perfectly, it would become misaligned almost immediately as soon as I moved the stage more than a centimeter or so.  I went through this process several times – level, raise, lower, realign, re-level, etc.  Here are some of the problems I guessed at and how I went about eliminating them as causes.
  • I began to wonder if the new threaded rod and a different pitch to it. ³  In order to test if there was a different pitch to the threaded rods, I took four pieces of aluminum foil, pressed a piece of foil firmly against each of the four rods, pulled out the four pieces of aluminum foil and compared the threads with my calipers and ruler.  They were all fine.
  • If the Z axis belt was too loose one or more Z axis rods could lose a step.  I tightened the Z axis belt and tested it again.  The problem remained.
  • Theoretically, the nuts on the Z axis rods could have lost their threads…  So, I held one and adjusted the Z axis belt.  It should want to raise or lower as you adjust the belt.  Wait?  What’s that?  It isn’t!
  • What does it mean when adjusting the belt doesn’t raise or lower a Z axis nut?  It means you installed the new Z axis rods, put the ‘bot back together, and forgot to tighten the set screws in the toothed pulleys onto the Z axis rods.  The result is that the Z axis pulley will be spinning freely without forcing the captive nut on the Z axis rod to raise or lower.

I certainly hope you learn from these mistakes.  Both were confounding problems caused by ridiculous errors.  However, if you have these problems, hopefully you’ll know how to fix them!

1. The next time you see me, feel free to point and laugh. [↩]
2. The only thumbscrew to survive my testosterone driven smashing. [↩]
3. It did not. [↩]