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General Mach Discussion / Relief cuts grow larger on one side and become skewed.
« on: November 29, 2014, 06:43:47 PM »
I have an interesting issue that I am having trouble diagnosing. I hope one of the kind people here can help.
System Specs.
Custom 4' by 8' CNC with HSD 12HP ATC spindle and 11"Z.
Very solid frame and gantry.
THK Linear bearings and 3/4" 12 Pitch 15.5 degree rack with 18TPI gears. Z is 16mm ball screw with 5mm lead.
Direct drive with Oriental Motor AR911AA3 Motor Driver combo (semi closed loop - will not lose position - if count go off from encoder it will correct the mis-step in the driver hardware or throw an alarm and stop the system if the error is too great)
The gears are attached to the shaft via hub and are not susceptible to coming lose.
Smoothstepper USB with latest drivers.
Latest version of Mach
Control Computer is an i7 with 8GB ram and SSD HDD running Windows 7 Pro.
Design Software - ArtCAM Pro (Legit licensed version) 2013.
This machine recently ran with a different control system setup and ran without exhibiting the below issue.
If I am cutting circles, squares, rectangles or any non-relief part everything checks out fine. If I run a relief the part literally grows and goes slightly askew no matter which direction I cut it - x or y, it grows corresponding to the direction - in other words, if I am carving a number 1 for example, the base will be fine and eventually the top will skew to one side. If I change orientation and raster mill it along the Y as opposed to the X the exact same defect appears and looks the same as the former but the skew is always furthest from zero.
Another example. I did a bird with the wings spread. I cut and pasted the wing and mirrored it when I drew it so I know it to be exactly like the other. If I run it milling along the X the right wing (furthest from zero) will slant and be slightly larger and detail does not suffer. If I mill it along the Y the left (furthest from zero) will be slightly larger and also slanted. If I cut a box the same dimensions all lines are perfectly straight and to specified length.
Here is what I have checked/tried;
Inspected the part in the Mach MDI - Looks like the ArtCAM rendering.
Noise
Wiring
Driver logs (the drivers will store information about miscounts and other data issues and can be computer monitored)
Set screws
Backlash
I ran the part files on another machine with no problems.
Steps per for each axis - things are moving to where they are supposed to.
Different milling strategies
Alternate acceleration settings ranging from very low to average
Debouncing
Plasma Mode
Step/Direction Pulse Delay
Running the part file ridiculously slow
Running the part file ridiculously fast
Running the part file at optimum speeds/chip load
And several of the other obvious suspects
Milling at different points on the table
I have not tried reinstalling and reconfiguring Mach from scratch nor have I tried a new smoothsteper as I don't have one available at the moment.
All checked out. The drivers do not report any corrupt or missing data nor corrected mis-steps (basically means they moved as they were instructed) and the mechanics are in good order. There is nothing lose and everything is solid. The machine is capable of good acceleration without issue.
The Mach setup is pretty basic. Only changes are what were needed to function such as motor tuning, a few custom M codes and port/pin setup to match the configuration. Not an expert at Mach but not new either.
Could this possibly be a SmoothStepper issue or Mach Issue? I am doubting it is mechanical as everything was checked several times over.
I am at a loss here. Anyone have any idea as to what could be going on?
Thanks in advance for any suggestions.
System Specs.
Custom 4' by 8' CNC with HSD 12HP ATC spindle and 11"Z.
Very solid frame and gantry.
THK Linear bearings and 3/4" 12 Pitch 15.5 degree rack with 18TPI gears. Z is 16mm ball screw with 5mm lead.
Direct drive with Oriental Motor AR911AA3 Motor Driver combo (semi closed loop - will not lose position - if count go off from encoder it will correct the mis-step in the driver hardware or throw an alarm and stop the system if the error is too great)
The gears are attached to the shaft via hub and are not susceptible to coming lose.
Smoothstepper USB with latest drivers.
Latest version of Mach
Control Computer is an i7 with 8GB ram and SSD HDD running Windows 7 Pro.
Design Software - ArtCAM Pro (Legit licensed version) 2013.
This machine recently ran with a different control system setup and ran without exhibiting the below issue.
If I am cutting circles, squares, rectangles or any non-relief part everything checks out fine. If I run a relief the part literally grows and goes slightly askew no matter which direction I cut it - x or y, it grows corresponding to the direction - in other words, if I am carving a number 1 for example, the base will be fine and eventually the top will skew to one side. If I change orientation and raster mill it along the Y as opposed to the X the exact same defect appears and looks the same as the former but the skew is always furthest from zero.
Another example. I did a bird with the wings spread. I cut and pasted the wing and mirrored it when I drew it so I know it to be exactly like the other. If I run it milling along the X the right wing (furthest from zero) will slant and be slightly larger and detail does not suffer. If I mill it along the Y the left (furthest from zero) will be slightly larger and also slanted. If I cut a box the same dimensions all lines are perfectly straight and to specified length.
Here is what I have checked/tried;
Inspected the part in the Mach MDI - Looks like the ArtCAM rendering.
Noise
Wiring
Driver logs (the drivers will store information about miscounts and other data issues and can be computer monitored)
Set screws
Backlash
I ran the part files on another machine with no problems.
Steps per for each axis - things are moving to where they are supposed to.
Different milling strategies
Alternate acceleration settings ranging from very low to average
Debouncing
Plasma Mode
Step/Direction Pulse Delay
Running the part file ridiculously slow
Running the part file ridiculously fast
Running the part file at optimum speeds/chip load
And several of the other obvious suspects
Milling at different points on the table
I have not tried reinstalling and reconfiguring Mach from scratch nor have I tried a new smoothsteper as I don't have one available at the moment.
All checked out. The drivers do not report any corrupt or missing data nor corrected mis-steps (basically means they moved as they were instructed) and the mechanics are in good order. There is nothing lose and everything is solid. The machine is capable of good acceleration without issue.
The Mach setup is pretty basic. Only changes are what were needed to function such as motor tuning, a few custom M codes and port/pin setup to match the configuration. Not an expert at Mach but not new either.
Could this possibly be a SmoothStepper issue or Mach Issue? I am doubting it is mechanical as everything was checked several times over.
I am at a loss here. Anyone have any idea as to what could be going on?
Thanks in advance for any suggestions.