E-step difficulty

[printbus]

FWIW, I noticed the consistency of my extrusion tests went up after I started discarding the first lengthy extrusion after heating up the extruder. I figure the filament might be *cooking* a bit in the nozzle during cooldown from prior use, and that the subsequent extrusion helps clear out whatever gunk might be in the nozzle.

One thing you could check before disassembly is to remove the filament from the extruder and see how easy the large gear rotates with steppers disabled. On one extruder build, I evidently hadn't tightened the second nut on the large gear enough, and with use the large gear was slowly rotating itself tighter to the extruder. By the time I noticed that, I could barely rotate the large gear by hand when I tested it.

[JimG]

One thing you could check before disassembly is to remove the filament from the extruder and see how easy the large gear rotates with steppers disabled. On one extruder build, I evidently hadn't tightened the second nut on the large gear enough, and with use the large gear was slowly rotating itself tighter to the extruder. By the time I noticed that, I could barely rotate the large gear by hand when I tested it.

When I checked the large gear in the manner you suggested, I found that it can move a few degrees either way without the hobbed bolt rotating. Pretty clear that I did not tighten the jam nut tightly enough in the back. I can get rid of the play by holding the head of the hobbed bolt and turning the gear. I am going to run that way for a bit and see if it will stay snug. But I am making plans to disassemble

Thanks for the insight.

Jim

EDIT - nope, running temporarily not going to work. When reversed, the gear loosens again immediately. This also explains why the problem just showed up in a print rather than only in calibration. The particular object I was printing needed a bunch of retractions. So I am guessing that the bolt became very loose during the print, resulting in an almost complete loss of extrusion.

[JimG]

Main source of the problem is that the nut well on the large gear is 1 - 1.5 mm deeper than the nut thickness. So the jam nut cannot make contact with the nut in the well. I noticed this during assembly but failed to act on it then.

The two M8 nuts in my kit were both thin nuts. The well in the large gear is sized for a standard M8. Fortunately, I had a standard M8 in a spare parts box. When I swapped out the standard nut for the thin nut, there was enough projection outside the large gear for the jam nut to do its job.

Estep calibration complete now at 880, with fairly consistent extrusion lengths. I am cautiously calling this a solved problem.

Thanks again for the help!

Jim

[printbus]

Some discussion regarding extruder clicks, pops, cracking and creaking came up in this thread, starting at about post #24 - http://3dprintboard.com/showthread.p...-amp-Questions

[JimG]

Thanks for the link. Very informative thread.

My creak is different from the noise I heard on the posted video. Mine is more like a rusty hinge.

My present working theories are 1) the sound of PLA rubbing against the plastic extruder body below the hobbed bolt, and/or 2) the sound of plastic-on-plastic gears.

I am using 3mm filament. In hindsight I wish I had drilled out the extruder body. The print that came with my kit needed some cleanup in most places. But I failed to test fit the filament path.

I'll also mention that I get a lot of white powder (my extruder is white) on the x-axis V-rails. There is a lot of wear going on with the large gear, and perhaps the small gear as well. This explanation for the creaking doesn't seem to explain more noise with PLA than ABS, unless PLA requires more extrusion effort?

Jim

[old man emu]

Wow! My extruder feed must have been waaay out. I short changed me 17 mm.

I used the wrong default value in my calculation below (working off the top of my bird brain). If I use the factory default of 841, then the calculated value comes out at 967 steps/100mm. That doesn't sound right when compared to your values.

OME

[printbus]

Wow! My extruder feed must have been waaay out. I short changed me 17 mm.

I used the wrong default value in my calculation below (working off the top of my bird brain). If I use the factory default of 841, then the calculated value comes out at 967 steps/100mm. That doesn't sound right when compared to your values.

Been there. I'll bet that if you put in 967 and run another test, you'll get results that say you need something like 800. At least that's what I kept running into. I then followed a suggestion I had read somewhere about never measuring the first lengthy extrusion after heating up the hot end. Doing so has really helped lead to more consistent results in my testing. If you're using Pronterface, others have reported improved consistency in test results by decreasing the settings/options E manual feed rate from the default of 100mm/min.