Feed motor Makes rough XY moves during print

Hey guys has any one had a problem with the feed motor making the print speed very inconsistent. When I run my delta
printer with out the feed motor being used in the gcode the machine moves very smoothly. Soon as I use the filament feed
motor the moves get very irratice . It does not appear to be a power problem since I have run tests with the 2 different power
supplys and When I disconnected the steeper motor from the ramp that made no difference in smoothing out the moves. It seems as though the
firm ware can not command moves to all four axises at the same time. Any Ideas ??? Seems the problem started so as I went
from 8 micro steps to 16 micro steps but at 8 micro steps the feed rate was way off from commanded feed rate.

Ron

Have found if I lower the Delta_segments_per_second to 40 and much of the jitters stopped but feed rate of the moves still not correct.
Still working to a better machine.

OK, that was a good test.
Delta printers have a lot higher computation overhead that the rest, due to lots of 32-bit square roots being done to calculate the effector position. You will see this as stuttering during moves. This will cause blobbing at each point as it pauses, and could cause missed steps (as the acceleration is interrupted).

A lot of it depends on how many pulses per second the controller has to output, plus the speed of the moves. A 16 mhz, 8 bit controller has a very hard time keeping up, and will never do so perfectly depending on how hard you push it.

Some of your choices are:
- Lower the movement and printing speed (you've already lowered the segments per second - perhaps more than enough)
- Use lower microstep rates for all motors. 16 microsteps should have been pretty OK except for over 100mm/sec or so. You could go to 8 (it will be a bit louder). You will have to re-calculate your steps per mm so it still moves the right amount, and put that in the firmware and re-flash.
- Use a different firmware. Repetier is supposed to handle a little higher step rate than others, it can do quad-stepping... however I still have problems with it and can not go as fast as I want, or print fast without random jitter/stuttering.
- Get a 32-bit controller as I just did. Some of your choices are Smoothieboard or Azteeg (a Smoothieboard clone that also runs Smoothieware). There are others that are perhaps not quite as popular/mature that I am not aware of. If someone else wants to suggest one of those, go for it.

Hope that helps!

Edited 1 time(s). Last edit at 01/05/2015 05:46PM by Paul Wanamaker.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
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Thanks so much for your input. I think I may have finally stumbled on to the problem and I think it is right in line with what you are saying .
The extruder I am using had me set it to 16 micro steps which worked out to 1162 steps per mm. Way to high!! . Causing to much over head
step out put . I set it down to 292 or quad stepping
and now the printer seems to be moving much closer to the right feed rate Correction ....programed feed rate.
Also I was able to change delta _segment_per_second to 80 which really help in getting the speed back.


Ron