My laser has dynamic backlash and I tried everything I know to fix the issue without any luck; I am hoping I can explain the problem and have a hand at solving the issue.
The version of the buildlog laser 1.0. The controller is 608 AWC DSP. The stepper drivers are A4988 Pololus. Microstepping at 1/16. The test program is a 101mm x 1mm box which cycles five times. Testing the Y axis. (there is no space/jerk when running the program) To measure backlash I am using a dial indicator with the resolution in 1000ths of an inch. At the beginning of each cut cycle I set the indicator to zero.
Running a cut cycle 10 times at the cut speed of 10mm/s gives the following measurements when the cycle is complete (in order of testing, units in 1000ths of an inch): -7.5, -9, +10, +15, +3, -2, -15, +2, +2, -9.
Again, but this time the speed is set to 400mm/s: -3, +1, -8, -15, -8, +9, +7, +4, -7, -16.
The electronics bay
The testing setup
Motors are NEMA 17, 0.9°, Dual Shaft - which are found in the makerslide store: http://store.makerslide.com/index.php?m ... ucts_id=30
The version of LaserCAD is 5.95 and the DPS firmware has been flashed to the latest version 120312V7.UG5 3-12-2012.
Video of the testing procedure: http://www.youtube.com/watch?v=wC0SbDPFAUwKnown issues:
The connecting rod of the Y motor has a whip. See video: http://www.youtube.com/watch?v=4mM7YiLfvyI
Although the belts have a little bit of spring to them (.020") the machine settles back to zero when adding then removing pressure on the axis. The Y axis beam slightly rocks, when forced, about .010".Step I have taken:
Updated firmware and software.
Increased the amperage to the motors from .67amps to 1.6amps with no difference to degree of backlash.
Added ground wire from stepper board to DSP.
Tried different stepper Pololu driver in different board slot.
Used 1/2, 1/4, 1/8 stepping modes. The backlash increased the most using half steps.
Cleaned the rails.
Tightened the belts to snuggness, not overly tight nor springy.
Tried various acceleration and start speed parameters, high acceleration increases backlash variance only slightly.
Removed all equipment attached to the mains line, the only equipment powered on the breaker is the laser and PC.
Checked the tightness of grub screws, rails, frame, pulleys, etc.
From here I am at a loss. The backlash is not really bad when cutting out small parts, but when trying to cut full 16" x 20" sheets with the parts spaced at .050" apart the loss in accuracy is so great the machine cuts into other parts.
I have MACH3 running my CNC, I have yet to connect MACH3 to this machine.
I've read posts where other experience some similar issues had the steppers to spongy, please review my motor settings.
Also, I lightly tested the X axis with the same, yet smaller range in error, issue.
Anyone help is appreciated, thanks.