[SOLVED] Underextrusion at 0.1mm but not at 0.2mm layer height
-
@llamazen 407 doesn't seem terribly low to me, unless you're printing with a .25 mm extrusion width or smaller.
For reference: to be able to reliably print small details down to 0.08 mm layers with a 0.25 mm extrusion width, I've found that more than 1000 steps/mm is necessary. With a 0.4 mm nozzle, the requirements are much less.
-
@phaedrux Here it is.
-
I did a test print today with 0.075mm^3 extra prime after retraction and it printed OK.
It's weird though because I never had to use it before. I got the number from the E3D nozzle diagram for my 0.4mm nozzle.
-
@phaedrux said in Underextrusion at 0.1mm but not at 0.2mm layer height:
..............................
You can combat this a little bit by setting the extruder to a higher microstepping. I find anything over 64 causes hiccups. .........................Just a "for info". The extruder moves much faster when doing retract/unretract than it does during normal print moves and that's what causes the hiccups. So if you are able to retract at slower speed, then you can push the micro stepping up a bit further. The step pulse frequency limit is about 200,000 so if you take the steps per mm, multiply that by the micro-stepping then divide the result into 200,000 it'll give you maximum extruder speed that you can use.
HTH -
@deckingman thanks for that Ian.
-
@deckingman @Phaedrux Sorry guys, I don't quite understand what you're saying. I currently set the microstepping of the extruder to 16 interpolated.
As far as I know, this sets the microstepping 256 virtual steps. I have tried setting removing interpolation but the motor gets noisy and whiny like it did with the cheap drivers.
-
@llamazen So the idea is that if the print move asks the extruder to move a distance shorter than the minimum distance of a single microstep the extruder motor won't move at all.
-
@llamazen I see where you are coming from and why. Unfortunately in this instance the term "interpolation" is a bit misleading (in fact, it's a lot misleading).
All it means is that when it is used, the driver chip will divide the micro step pulse into 16 smaller step pulses. But, it's always 16 smaller step pulses. The step pulse from the Duet is an on or an off, a 1 or a zero, a high or a low. There is no in between. I'm not sure what happens inside the firmware but I'd imagine there will be some sort of rounding happening. So if the calculated movement amount required say 10.6 micro-steps, then it would be rounded up to 11 pulses. Conversely, if the calculation resulted in 10.4 micro-steps then it gets rounded down to 10 pulses. Whatever happens, it's always a whole number of micro step pulses. So "interpolation" doesn't give any better positional accuracy. From a positioning point of view 16x micro-stepping with interpolation is exactly the same as 16X without interpolation and the only way to get finer resolution is to use higher micro-stepping.
HTH -
@deckingman OK got it. I'll do a print with 64 and 256.
Thanks guys for the input.
-
@llamazen said in Underextrusion at 0.1mm but not at 0.2mm layer height:
@deckingman OK got it. I'll do a print with 64 and 256.
Thanks guys for the input.
Stick with 64 to start with. At 256x you'll likely run into the maximum step pulse frequency of 200,000 Hz that I was talking about (unless you use very low retraction speed). Run M122 during the print and check for any reported hiccups which should zero or near zero.
-
If you let me know the steps per mm @16x, I can calculate the maximum extruder speed that you can use for retraction at any other micro-stepping (or you can do that calculation yourself using the info I posted earlier).
-
@llamazen Sorry, I've diverted from the original subject to something that I had measured on a recent test. I think it is probably best that I spin that off to a another post that I will write now. I doubt what I am seeing will directly effect your work, but I suspect it may have a little to do with retraction and advance settings.
-
@deckingman said in Underextrusion at 0.1mm but not at 0.2mm layer height:
@phaedrux said in Underextrusion at 0.1mm but not at 0.2mm layer height:
..............................
You can combat this a little bit by setting the extruder to a higher microstepping. I find anything over 64 causes hiccups. .........................Just a "for info". The extruder moves much faster when doing retract/unretract than it does during normal print moves and that's what causes the hiccups. So if you are able to retract at slower speed, then you can push the micro stepping up a bit further. The step pulse frequency limit is about 200,000 so if you take the steps per mm, multiply that by the micro-stepping then divide the result into 200,000 it'll give you maximum extruder speed that you can use.
HTHSo with 850 steps/mm at 16x that would mean 14,7mm/s?
-
@obeliks said in Underextrusion at 0.1mm but not at 0.2mm layer height:
@deckingman said in Underextrusion at 0.1mm but not at 0.2mm layer height:
@phaedrux said in Underextrusion at 0.1mm but not at 0.2mm layer height:
..............................
You can combat this a little bit by setting the extruder to a higher microstepping. I find anything over 64 causes hiccups. .........................Just a "for info". The extruder moves much faster when doing retract/unretract than it does during normal print moves and that's what causes the hiccups. So if you are able to retract at slower speed, then you can push the micro stepping up a bit further. The step pulse frequency limit is about 200,000 so if you take the steps per mm, multiply that by the micro-stepping then divide the result into 200,000 it'll give you maximum extruder speed that you can use.
HTHSo with 850 steps/mm at 16x that would mean 14,7mm/s?
No, sorry I didn't make that clear. I should have said, if you have the steps per mm at 16x, then first divide by 16 to get whole steps then multiple by the new steps per mm. If you have already got the steps per mm at the desired micro-stepping, you simply divide that into 200,000. So with 830 steps per mm, you can go up to 241 mm/sec. You'd need to go to 256x micro-stepping to get as low as 15. Sorry.
-
OK, that makes more sense.
-
Or use my Extruder Microstep Calculator. Just enter steps/mm (@ x16) and look at the
Max Retraction Speed (mm/min)column of the result table that will give you these values for all available microsteppings.
For this case you can simply ignore all other input fields and result columns.
Manuel
Duet 3 6HC (v0.6) with RPi 4B on a custom Cartesian
with probably always latest firmware/DWC (incl. betas or self-compiled)
My Tool Collection -
@wilriker I'd forgotten that you'd done that.
-
Back to the original topic. I finally found some time to play with the printer again and tried your suggestions.
I have forced the steps per mm to 64 and did a test print. It did not fix the problem but the extruder motor was louder.
I have printed 2 hollow test-cubes next to each other. There were no signs of under extrusion but the retraction cylinders looked bad.
Finally I have decided to just use the extra prime amount for the time being. It gives me the good results inspite of my reluctance to use it.
Thank you for your input. I learned a lot about the finer details of extruders.
