I’ve been having an intermittent problem with my printrbot simple metal in which it seems multiple layers are being squished together. To get a better idea of what’s happening, take a look at the attached photo.
The incidents begin with a cracking sound caused by the extruder nozzle being on the same z axis plane as the top layer (or few layers) of printed material. It seems like the Z axis is not moving up far enough at points in the print which causes the layers to squish and the extruder nozzle to impact printed plastic.
As I mentioned earlier, the problem is intermittent making it even harder to diagnose. Some tall prints come out great. Other prints have squished layers but the printer seems to correct itself and finish the print. I thought it may be a stripped z axis thread, but the layer squishing happens at all different heights.
In the case below, the line near the top of the sphere was caused by an incident like this, but I caught it early enough to intervene. I paused the print, moved the z axis up about .3 mm and then used G92 to tell the printer its z axis was at the height it had previously thought it was at. While it worked for the first incident of this print, I wasn’t lucky enough to catch the second and the sphere was eventually knocked off the bed by the print head.
They should be easy to remove. Threadlocker is important, but one thing I’ve done to mine after my Z-Coupler came loose was to grind a flat on the end of the leadscrew where it goes into the coupler. This gives a much better surface for the set screw to grip against, and better prevents any rotational slip or backlash as long as the set screw is at least snug.
