What to do when the extruder stepper gags

I began to print a larger object. The extruder would start to skip steps at so time into the print. I found as the temp went up it failed earlier and as the speed went down it failed earlier. I posited that the filament was probably flowing out of the print head faster than the feed speed causing too much build up of plastic.

I brought the speed way up and now was printing perfectly, with the exception of some ringing in the print.

So if you have the problem I would take the temp down or the speed up.

 

I am making up some non critical parts. I have been using old PLA of various manufactures just to get rid of it. I use the Partsbuilt system board. I found this one roll that would not complete a print. In looking at the filament after the extruder stepper began dropping steps I could not find anything wrong. The extru8der stepper was running pretty cool. I began bringing up the current until the stepper hit 120F during print. I took the extruder temp up to 235C. Now it worked.

 

First thing I did was to replace the 42mm stepper with a 48mm stepper. I then adjusted the current.

 

I have changed all of my steppers from 1.8 degree to 0.9 degree. this has resulted in quieter operation but did not give me the quality improvement I was hoping for. I think I have run into the maximum quality the system can supply. The spring in the belts driving the weight in the steppers seems to be the limiting factor. I can move speed down, but I find that my lower speed limit is about 20mm/s after which quality goes down. My best compromise is about 30 mm/sec for quality. If I just want to make mechanical parts I can print at 70 mm/sec. This is for PLA. All this is with the caveat that as I learn I often find that previously, I was completely wrong.

 

I am printing up some non critical mechanical parts that take about half an hour each. I got the dreaded stepper missing steps and gagging. I thought this a perfect time to figure out the parameters that cause it.

I am using cheap PLA.

Temperature: gagging stopped as I moved the temp down to 205 above 205 causes problems
Speed: no effect. Works from 20mm/sec to 50mm/sec
layer thickness: Fails at .1 works from .15 to .25 This seems really odd and I have no idea why

My observation is that the print head just stops being able to feed the filament. When I pull out the filament it looks fine with an expanded bulb the width of the inside of the nozzle at the end.

I just moved so my machine shop is down for the foreseeable future so I can not make physical mods. The heat break on my hot end is shorter than what I normally had because of the Chinese parts that came in. When I am able I will machine a variety of heat break lengths to see if that is the source of my problems. I am positing that the hotter the print head the more likely that the retracted filament in a short heat break hitting a cold heatsink will seize. Like many reasonable assumptions will probably fail an actual test