All-metal hotend installed, and it brought some new problems in

Written on Monday, October 9, 2017.
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My Micro Swiss arrived from The 3d Printer today (express post!), so I installed that.

While the extruder block was disassembled I noticed that the spring on the tensioning arm was really wimpy, so wimpy that it didn’t even leave tooth marks behind on the PLA. Since this could be a contributing factor to the extruder skipping I’ve been experiencing when printing solid layers, I swapped that spring for a much beefier one.

After these two changes I found that some old and new problems have joined me:

  1. The vertical vibration ripples have come back.
  2. These ripples have been joined by a new set of ripples, this time going -45° diagonally on all sides.
  3. The nozzle offset is now different, and I need to work out the new one so that the nozzle homes in the correct spot. I’ve moved the glass sheet over for now.
  4. The extruder still skips while laying down lots of plastic for solid layers.

Possible causes: Vibration

  1. The new Micro Swiss nozzle is shorter than the old one, so I’ve had to crank the bed higher than before. Less spring tension means more bed wobbling.
  2. I have a 12 V blower installed as the part cooling fan and it’s starting to make funny sounds since it’s hooked up to 24 V. Maybe it’s rattling and causing vibration? I tried a print with this fan turned off and it halved the size/depth of the vibration marks, but doubled their frequency.
  3. I wrote several posts ago that Y bearing/s (I think it’s the two on the left side) had developed play in the Z direction, and also started to make loud rattling/scraping sounds during rapid moves. This could be introducing vibration.
  4. The extruder block may have been reassembled improperly.
  5. The stiffer spring on the tensioner arm might be misaligning the plastic parts of the extruder assembly.

Possible causes: Extruder skipping

  1. The heater block may not be reporting the correct temperature. I have noticed that skipping reduces — but doesn’t disappear — when temp is increased by 20 °C. Needs PID tuning.
  2. The motor may be dying.
  3. The motor may be running with too little current or voltage.
  4. The (brand new, by the way) nozzle or heat chamber may have some debris inside them from the factory. Do a cold pull and a full clear.
  5. The extruder pulley and toothed wheel could need lubricating.
  6. The toothed wheel might be wasting torque by being so large. Printrbot’s extruder gear was far smaller.
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