filament feedrates questions

OK,
So I have the CNCDudez Sanguino breakout board powering my custom dual head extruder.
Jhead, .4mm diameter, 100k thermistor, 1.75mm dia.
Nema8, thru a 16:1 reduction, 17mm diameter hobbed wheel. 16x microstepping on the jumpers.
Using a Stepstick A4899, turned up, monitoring stepper body temp and keeping it about 90C.

In Pronterface, I am driving the head temperature to 270C. It thermocouple reads 230C.
I have calibrated the steps to filament mm to match a measured length of filament.
It tracks very well, to within a .2mm of the target length given.

for ABS feedrate, I can sustain 500mm/min without stepper skips. I can go higher in short distances like 25mm length or 50mm length.
I think the hotend can't keep up with flow, so the pressure builds up and the stepper skips.

Question: is this a good rate for a fast moving machine? I don't have the head mounted to the machine yet, so I can't get a sense if that amount is good.

I was asked a similar question in the Tantillus forums [forums.reprap.org] and these are the results I came up with:

Extrusion length @ Rate @ 190c in PLA

50mm @ 250mm/min
100mm @ 230mm/min
150mm @ 220mm/min

They allow print speeds of over 200mm/s @ 0.25mm layers. It may even allow faster but the print results are never as good.

---

FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

that's great news then.
I am trying to upload a video to youtube to show it working.
Lot of progress this week for me. Purely mechanical guy, sorting out all this Marlin/stepstick/Sanguino stuff.

on to the high power microstep drivers and big steppers next.

Edited 1 time(s). Last edit at 09/21/2012 08:08PM by davew_tx.

[youtu.be]

I guess my clip was during the tuning.
There is a chatter and the speed is probably more towards 300mm/min in this.

Well, some advice.
Don't put 2 amps into a Nema 8 and expect good things.
I let the smoke out of the motor and the KL4030 driver.

I can't seem to set the parameters to get good feedrates and low motor temp.
Best I saw was around 400mm/min continuous feeding, and the motor running about 100C.
This was with 36 volts into the driver, set at 1.3amps.
That is just too much going into that little stepper, and I am guessing a short lifespan.

Tried both the stepstick and the KL4030 and both led to idle motor heating.

I see that Kysan has a 64:1 Nema 8, which might be worth a try. the 16:1 is very close except at low amperage, there is little torque.

you will want length of 150mm or more, i bet you acceleration is kicking in here, and you never reach the posted speed. the inertia of the print head will slow you down quite a bit. i would shoot for 15-30mm a second for perimeter and 40-60 for infill, at 0.2mm height. this may be too fast for an uncalibrated machine, tweak and test, if you want to know for sure weigh the print head, and motor, and add that much mass to the carriage, then test positioning accuracy. this will test your jog speed or max speed for when not printing. printing you also have the head dragging against the surface of the print job, and that drag can be significant.

thanks for the tips.
so far, I only have the print head in a vise on the table.
The numbers I am mentioning are filament feed rates, and it appeared to me to match the values.
It would push 10mm a second into the hotend, which is 600mm/min.

I've seen you mention print head dragging on the part in another posting.

I don't see where the head would go that is not air under it.
the road it's on has never been printed, and roads never cross.

Can you describe this more, because I'm not on the same page.

feedrate is a term used for x/y/z motion.

what do you mean by roads? the feedstock pushes thru the nozzle hot end, out comes filament, that needs to be squished down. there is contact of tool head to drag x/y movement. as for the *flowrate* (the correct term for extrustion) you will want to test it under load. when extruding, there is over 5kg of force on the hobble bolt, which depending on your gear ratio is between 1-5kg minimum on the stepper motor.

Edited 1 time(s). Last edit at 09/26/2012 04:30PM by jamesdanielv.

I just see this differently, and I may be wrong. It's happened to me before.

Thanks for your reply.

Edited 1 time(s). Last edit at 09/27/2012 01:07PM by davew_tx.