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CS-Lab / Jerky movements in complex toolpaths.
« on: July 22, 2016, 12:31:09 AM »
Hi,
I have retrofit a 1979 matsuura mc500v with a cs labs csmio/ip-a ethernet analog motion controller. The machine was originally capable of accelerating at 40in/secsec and 400ipm rapids.
I currently have the acceleration and rapids set at 80% of their normal values.
I have look ahead set to 200 lines, but I have tried all combinations including 1 line and 1000 lines.
I have CV turned to on. All other settings related to CV are off but I have played with the settings ad nauseum.
I have CV feedrate turned off, although I have tried to run programs with it on.
The problem:
When running a toolpath of any complexity, The machine tends to jerk unpredictably at moments peppered throughout the program. It does not cut in a jerky movement through the whole program, just every few seconds and sometimes throughout entire sections of the the toolpaths. These jerks will always happen in the same places in the toolpaths. These jerks will trigger following errors if I do not have my max following error set somewhere around .05" These jerks do not happen when I'm running simple toolpaths, but only when I'm running complex toolpaths with lots of small arcs and linear movements.
My attempts to fix the problem involve:
What works is to run the program at much lower feeds and rapids. This results in a 40 to 50% longer cycle time. Since this is a production machine in high volume production shop, this is not an acceptable solution. I have also set the acceleration rate at half the value that the machine was designed to run at, but this just makes the jerks less prominent. This also results in a rougher finish when moving in arcs and contours. This is also unacceptable. I have also tuned the servos over and over, trying many different combinations in an effort to achieve the perfect tune. The tighter the servos are tuned, the more pronounced the jerks are. I have also uninstalled and reinstalled a different version of mach3. I am currently running V R3.043.062. I have also installed the lastest version of the firmware for the cs labs controller.
My theories:
I suspect that something is driving the servo drives far beyond their configured limit in brief pulses in order to move the machine along to the correct position. It is almost as if mach or the motion controller are ignoring the acceleration limits when moving in small increments along a contour.
Another possibility is that the look ahead function in mach is missing lines of code. Although this sees less likely since the program will be running along smoothly but then jerk in the same spot every time.
Response from CS labs:
I have recently made a video outlining the problem and posting it on my youtube channel. It can be found here.
https://www.youtube.com/watch?v=VEE7v3ewd3U
CS labs can't seem to figure out the problem.
I have retrofit a 1979 matsuura mc500v with a cs labs csmio/ip-a ethernet analog motion controller. The machine was originally capable of accelerating at 40in/secsec and 400ipm rapids.
I currently have the acceleration and rapids set at 80% of their normal values.
I have look ahead set to 200 lines, but I have tried all combinations including 1 line and 1000 lines.
I have CV turned to on. All other settings related to CV are off but I have played with the settings ad nauseum.
I have CV feedrate turned off, although I have tried to run programs with it on.
The problem:
When running a toolpath of any complexity, The machine tends to jerk unpredictably at moments peppered throughout the program. It does not cut in a jerky movement through the whole program, just every few seconds and sometimes throughout entire sections of the the toolpaths. These jerks will always happen in the same places in the toolpaths. These jerks will trigger following errors if I do not have my max following error set somewhere around .05" These jerks do not happen when I'm running simple toolpaths, but only when I'm running complex toolpaths with lots of small arcs and linear movements.
My attempts to fix the problem involve:
What works is to run the program at much lower feeds and rapids. This results in a 40 to 50% longer cycle time. Since this is a production machine in high volume production shop, this is not an acceptable solution. I have also set the acceleration rate at half the value that the machine was designed to run at, but this just makes the jerks less prominent. This also results in a rougher finish when moving in arcs and contours. This is also unacceptable. I have also tuned the servos over and over, trying many different combinations in an effort to achieve the perfect tune. The tighter the servos are tuned, the more pronounced the jerks are. I have also uninstalled and reinstalled a different version of mach3. I am currently running V R3.043.062. I have also installed the lastest version of the firmware for the cs labs controller.
My theories:
I suspect that something is driving the servo drives far beyond their configured limit in brief pulses in order to move the machine along to the correct position. It is almost as if mach or the motion controller are ignoring the acceleration limits when moving in small increments along a contour.
Another possibility is that the look ahead function in mach is missing lines of code. Although this sees less likely since the program will be running along smoothly but then jerk in the same spot every time.
Response from CS labs:
I have recently made a video outlining the problem and posting it on my youtube channel. It can be found here.
https://www.youtube.com/watch?v=VEE7v3ewd3U
CS labs can't seem to figure out the problem.