Extruder feedrates maxed out somewhere?

Hi,

in repetier there are three places I know I can change the max feedrate of my extruder stepper motor.

1. Repetier printer settings
2. EEprom
3. configuration.h

the problem is that if I have all three set to something like 50 mm/s, my extruder stepper motor still only runs at around 10 mm/s, I gathered thats its speed by incrementing the speed from 5 mm/s upward until no change. Is there something in the software that does not allow the extruder to extrude at a certain speed that I am missing? I am using manual extrusion, Ive tested all three arrow buttons, and get the same result, is it the manual extrusion that doesn't allow it to go faster?

What's your extruder steps/mm set to?

You could always try sending the printer the following G code to make it extrude, just change the F for what speed you want to test at if it goes faster then there might be a cap in how repetier send the command from using the manual buttons

G1 E10 F400

It is a 27:1 geared stepper motor, I have the steps per mm set to 2700, I changed it to 100 steps per mm and still get the same result, it wont go above that 10 mm/s mark, but of course at lower steps per mm that 10 mm/s mark is slower. Maybe it is the motors limitations?

Tried manual input with g code still the same results. I don't know why I bought a 27:1 I should've bought a 5:1 and it would've been fine.

10 mm/s is still pretty fast to feed to the extruder, It is just bothering me that it seems speed locked.

At 2700 steps per mm, you might be looking at the maximum processing power of the 8-bit Arduino Mega processor not being able to generate things faster.

At 200 steps/mm I can get about 125 mm/s from a motor (Repetier, RAMPS, delta) before it maxes out. So doing the numbers means you'll top out at 9.3 mm/s -- very close to the 10 mm/s you've measured.

There is a simple solution, change the jumpers underneath your extruder drive to use 2 microsteps instead of 16. Then change your steps/mm to 337.5.

Actually, rereading your reply, it seems that the limit isn't how fast the extruder steps pin is switching, it's a hard mm/s limit in firmware somewhere.

I assume you've set Repetier to use eeprom? What's your extruder acceleration set to?

Try sending this command:

M201 X1000 Y1000 Z100 E6000

then try again.

Edited 1 time(s). Last edit at 02/17/2017 08:55PM by nebbian.

I am thinking that it is just the stepper motor itself, I change to 1/2 stepping, and it helped, but it it is intermittan, meaning it looks like it wants to go fast, because I set the acceleration to 10 mm/s^2 and it slowly accelerates until about 5-6 mm/s and then stops but the motor is clearly still trying because I can hear the whining noise.

I maxed out the stepper driver voltage pot, and that seemed to make it less inconsistent but it still has problems.

I tried the manual command and it still had the same issue.

Verdict, I can't make a 27:1 geared stepper motor go faster than 5-10 m/s, I think, the stepper motor just can't go faster. I do have some drv8825 drivers coming in the mail, so I will see if they help at all, supossedly able to provide more current and such, 1/32 stepping and things, but I'm not holding my breath.

also limits in how fast the motors steps, vs how much power can be reached can be an issue.


there may be issues in how the inductance vs resistance effects the motor at the steps speed you are after. there is only so much current that can overcome the resistance of a charged coil. more voltage allows motor to step faster because as step rate increases so does the coil resistance increase. at 12v, many motors can only get to about 1-3 to 1/2 of spec'd max speed.


The only way to get more power out of motor is to increase voltage above 12v, or use a better stepper motor. I think that looking at the steps rate of motor specs will help with understanding the power curve. this is assuming that your using ramps at 12v.

what is the motor you are using? and what does it say in its specs for steps per second?

if the motor specs are exceeded. then it might be best to reduce power ratio. a good geared down ratio is 5:1, or 10:1 for 3mm filament, and 5:1 or 1:1 for 1.75mm. this also varies based on the torque of the motor.

Thanks for the info, its a NEMA 17 geared at 27:1, way too much obviosuly from what your talking about. What you are saying makes sense because if I try to go faster than 5 mm/s the stepper motor usually stalls, gives taht whining noises but no movement. Maybe the DRV8255 drivers will allow a little more juice to be given to the motors, but in the end I have bought a nema 17 5:1 geared motor, should work just fine, the main thing is that I have a pretty long bowden tube, and I'm tired of the normal nema 17 motor not able to push the filament through at normal temps, I usually have to almost cook PLA in order for it to come out so I can print at speeds like 50 mm/s.

I have a ramps board, I have been trying to see if I could switch to a 24V power supply, but it sounds like the normal ramps board cannot support it, because that would probably help out a lot.