Flex3Drive Motor Stall

guerty25

Hi all,

I recently built a delta printer (following dc42's guide with some modification). I added a Flex3Drive G5 remote extruder (40:1 gear ratio). Their recommended settings are as follows:

M350 E8 I0; microstepping
M566 X1500 Y1500 Z1500 E6 ; jerk
M201 X2000 Y2000 Z2000 E120; accel
M203 X18000 Y18000 Z18000 E2400; max speed
M906 X1500 Y1500 Z1500 E400 I60; current

I'm also using an E3D volcano for my hotend. E3D claims the max volumetric speed is 25 mm3/s.

I've found that my extruder stepper motor stalls at anything over 800mm/min. My steps/mm is set at 2450 mm/min with 8x microstepping (306.25 real steps) so I am being severely limited by my extruder motor. I ordered a new NEMA 17 pancake motor from StepperOnline (17HS08-1004S) to see if that makes a difference. My existing motor is a Usongshine US-17HS4401S. Is there any other steps I could take to alleviate this limitation?

Thanks!

Veti

put the values into the emf calculator and see if you are limited by the max speed of your motor.

https://www.reprapfirmware.org/

bot

It's likely because your stepper motor is being commanded at too fast of a speed. To improve this, you'll want to find a stepper motor with the lowest inductance possible. I've found nema 17 with inductance of about 2 mH is the best you'll get. If lower, even better.

You probably still won't get as fast as you'd like, though. 40:1 is a lot of gear ratio.

bot

Wait. Also, I just ran the math and 800 mm/min on the E axis (with 1.75 mm filament) is equal to 32.07 mm^3/sec. Is my math wrong? It seems to be exceeding the stated performance.

guerty25

@bot I think I'm calculating this correctly. Here's my math:

800mm/min / 60s = 13.333 mm/s

(1.75mm / 2)^2 * pi = .875 mm2

13.333 * .875 = 11.667 mm3/s

This definitely could be (and probably is) flawed.

bot

@guerty25 I think your math is wrong.

800 mm/min = 13.333 linear mm per second

The volume of a cylinder of filament 0.875 radius and 13.333 height is given as: V=πr^2h=π·0.882·13.33≈32.06962

(Badly copy and pasted from google. Google for "volume of a cylinder" to get the calculator.)

guerty25

@bot Wouldn't volume multiplied by speed give me mm^4/s? Shouldn't it be area times speed?

bot

@guerty25 the benchmark is given in mm^3 per second. Time is an essential component of this.

guerty25

@bot yep my math is flawed. If anyone else stumbles on this and is also bad at geometry here is a calculator.

In the end then I guess it doesn't really matter that my motor stalls at the higher speeds. 800mm/min is pushing the volumetric limits of the volcano, so I'll get underextrusion anyway. I did set the max volumetric speed in PrusaSlicer to 23 mm^3/s and it still stalled but that might have been acceleration or some other factor that I'll have to dig in to.

Veti

you could get a mosquito magnum. it can reach 30-35 mm^3/sec.