Irregular extrusion lenght!!!

[viprit]

I believe I'm suffering from irregular extrusions.
I have measured 50mm of filament from the top of the PTFE tube and marked it, then from Prepare > Move Axis > 1mm > Extruder I've increased the value of exactly 50mm and I ended up having 8mm left out of the PTFE tube. I repeated the test twice more, every time staring my measurement from the top of the PTFE tub: once I got 4mm and once I got 12mm... Weird enough they are all multiples of 4, even if 3 is not really a series...
If my understanding is correct this might either be caused by the extruder motor losing steps or by the gear slipping on the filament (so partially related to the variable filament section).

Question No. 1: is my understanding correct?
Question No. 2: is there any other obvious cause for this?
Question No. 3: how do I check if the extruder motor is losing steps? (I have a multimeter and a crappy oscilloscope)
Question No. 4: assuming the motor is working fine, what can I do to fix this?
Question No. 5: is it possible this is related to my other issue with the wobbly XY plane?

Thank you for your patience, I imagine this has been asked a hundred times already, but the shttps://ovo.fyi/redtube/ https://ovo.fyi/beeg/ https://ovo.fyi/spankbang/
earch function of this forum doesn't seem to play nice with me...

[William]

Thanks for your question. Your logic and point are correct.
Here is my answer:


A1+A2: You can control it move 100mm, then check the actual length.
Try to check it 3 times.If you get 3 different values then it means the motor driver or the motor broken.
You can swap the motor from X-axis or swap the a4988. Then test it again.
For how to calibrate the Estep ,you can refer to this video.

A3:For the losing step,you can print the test gcode or measure the length and you will know it normal or not.

A4:You can refer to the FAQ of the i3 type printer
viewtopic.php?f=109&t=61933

A5:It seems no details related to the X/Y wobbling

Cheers