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SoliForum - 3D Printing Community → Solidoodle Discussion → Hysteresis Affected by Print Speed
Lawsy's comments about speed of non print moves in the z wobble discussion made me think...
http://www.soliforum.com/topic/372/z-axis-wobble/
How can hysteresis fixes, either mechanical or through software/firmware apply to different speeds? Just based on the nature and cause of hysteresis, faster movements with more momentum would increase the hysteresis, no? Do any of the fixes include a way to dynamically compensate for this?
Isn't that already handled? It seems to me that you measure the hysteresis at one speed, make an adjustment and save it to your profile (say in your start.gcode). Then, when you decide to use a different speed, you run a calibration object and test the backlash and adjust the profile.
Say you have Fast, Medium and Slow profiles and you have different hysteresis amounts for each.
That's conjecture, since I have not adjusted my backlash yet.. but it seems to me that it would be the way things are done.
Maybe someone else has a better idea about it though.
--Tim.
Almost always though, you have many different speeds even in the same print... Fastest for non print moves, fast for fill and inside perimeters, and slowest for external perimeters and bottom layer as an example.
I guess the way to tell it to test with an accurate gauge at various speeds.
Move axis back and forth a x mm/sec and measure backlash. Repeated at 2x mm/sec and so on.
I'm interested to see if Josh's theory is true. It seems plausible.
The other reason my interest is peaked about this is that I noticed my banding is significantly worse when attempting faster non print movements. What would be great is if there was a way way to independently alter the non print x, y, and z movements. Higher speeds don't seem to trouble my prints nearly as much in the horizontal plane as they do in the z axis.
Think it would be overshoot, not backlash. A slow 10mm move becomes 10.05mm at high speed, ie 10000+ feed rate in Repetier settings. I didn't figure it was enough to worry about.
The other reason my interest is peaked about this is that I noticed my banding is significantly worse when attempting faster non print movements. What would be great is if there was a way way to independently alter the non print x, y, and z movements. Higher speeds don't seem to trouble my prints nearly as much in the horizontal plane as they do in the z axis.
Pending the results of jenninaj in the z-wobble thread, having at least a separate z speed setting in slic3r might be a good feature request.
This also brings up another interesting point, because I can guarantee that the Solidoodle is not capable of moving 100 mm/s in the z axis. So how is this handled? Does the command convert the z stepper to just move at full speed till the proper distance has been traveled or does it think it is moving at that speed and possibly cause issues? I have to believe it knows it is not moving at that speed since it is not like the prints are really off dimensionally that much even when banding occurs. Ian, you said you were going at 300 mm/s non print moves... Have you seen any difference in print's z movements/results at those high of speeds?
Well my g-code is asking for a feedrate of 6000 with a 100mm/sec value.
Ian, what is yours asking for with a layer change?
From memory there is a max feedrate setting in the firmware for each stepper. It could be possible that the firmware just caps any fast z requests to this.
That is my guess. The Z speed doesn't really affect much, other than how long the extruder has to wait in place during lifts and layer changes. Faster Z means less time for oozing, so I would expect it would improve seams. It might retract fast, but then have more time to ooze while waiting on Z, which means maybe more blob when the plastic hits the layer again, or a gap after the retraction due to that plastic already having oozed out, or both.
SoliForum - 3D Printing Community → Solidoodle Discussion → Hysteresis Affected by Print Speed
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