I found my Ender 3 was skipping extruder steps a lot, mainly while printing infill (tri-hex at 30%), to the point I saw several layers of infill with spotty extrusion or nothing adhered at all.
When I pulled the filament, I had to use pliers to get enough grip to back it out of the hot end. I disassembled the hot end and found melted filament in the end of the Bowden tube, though I'm not sure that indicates heat creep, because I had to dismount the fan in order to reach the heat block and nozzle with the wrenches, and then preheat to get the nozzle out (meaning the heat sink got a lot hotter than it normally would with the constant blast of its fan).
Since the nozzle was full of melted plastic as well, I simply replaced it, made sure the heat break was clear by pushing the Bowden tube through it (and removed all melted plastic from the end of the Bowden tube), then reassembled the hot end with a brand new 0.4 mm nozzle. I then started a new print, gratified initially by the clean, even extrusion.
Until it stopped printing infill about 10 layers into the print.
At that point, I simply aborted the print and turned everything off, as I didn't have time to deal with another disassembly cycle (Sunday evening and had to be up early for work today).
What should I look for in trying to troubleshoot this issue with the nozzle or hot end clogging repeatedly?
I'm printing Amazon Basics PLA, a spool that was purchased the first week in May but only unsealed two days ago; my nozzle is set to 200 °C and the coated glass bed (now using a glue stick wash for adhesion assistance) at 55 °C. My nozzle clearance is set by homing, jogging the Z axis up by 0.075 mm, and leveling snug on a 0.08 mm feeler gauge (set so I can barely push the feeler under the nozzle and have palpable drag when in place, done with bed and nozzle preheated); this should give clearance between 0 and .005 mm. My first layer (standard 0.2 mm thickness) was perfect, no extruder step skipping and nice, even line width; this problem started only when the machine began to print infill -- infill prints faster than walls and top/bottom, but I'm not sure this is related to that, as I could see skipping on the walls on the second or third infill layer. This part was printing with 3 line walls and 30% tri-hex infill.
The Bowden tube was replaced when I installed a new hot end two weeks and ten or so prints ago (which included a new nozzle, the same one that I was using until yesterday); I made the cut in the PTFE with a tubing cutter (the kind with a wheel that revolves around the tube), so I'm confident it's square, and I ensured the tubing was butted firmly on the nozzle and the lock ring installed on the push-in coupler.