Program is not matching simulation

[Anonymous]

Hi,

I created a simple design that I want to cut out with my CNC. When I run the simulation, everything looks great. When I run the program everything appears to be working correctly. I have the 2D Contour set to step down in 2mm increments and on the 5th or 6th pass it seems like the program somehow offsets the cut by a large amount. I am not sure if I have done something wrong in the design/setup of the file. I have attached the design file, an image to show what is happening and the .nc code. Any ideas?

Thanks,

-Mike

[michael]

Had a quick skim of the gcode I'm not an expert by any means but there doesn't appear to be anything wrong with it. What is the actual z height when it happens?

[Anonymous]

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@michael wrote:

Had a quick skim of the gcode I'm not an expert by any means but there doesn't appear to be anything wrong with it. What is the actual z height when it happens?

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It is weird, I visualized the gcode (universal gcode sender) and it all appears correct. I ran the program twice with the same result; on the 5th or 6th pass it deviated. I then re-generated the gcode as a version iteration (V2) and ran it again, with the same issue.

I'm not sure what the exact Z height is when it happens. I think I should maybe run the program again and save the log/commands and investigate that further. Perhaps it's a hardware issue I am running into.... though I just recently cut out 4 sheets of 4'x4' 3/4" poplar plywood and had no issues, not to mention it seems to error out at the same time.

[LibertyMachine]

What control are you using at the machine and what post processor are you using at the Fusion side of things?

Is this a self-built machine or a purchased one? Assembly required?

Just trying to rule out the usual culprits...

[Anonymous]

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@LibertyMachine wrote:

What control are you using at the machine and what post processor are you using at the Fusion side of things?

Is this a self-built machine or a purchased one? Assembly required?

Just trying to rule out the usual culprits...

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I am using a laptop running Universal GCode Sender. The controller is an Arduino running GRBL + CNC Shield v3.51. The post processor on Fusion 360 I have selected is GRBL. My CNC is a self built machine based on the OX CNC. I recently cut out a bed for my daughter, which was a fairly large project with no issues (attached). That said, it could definitely be a hardware issue, but it seems very suspicious that the program/error is repeatable and always at the same spot...

[Anonymous · Accepted solution]

I finally got back to looking at this issue.

I re-ran the program again and it failed at the same spot (no surprise). I saved the gcode (gcode fail.txt) and found it failed on the pass z=12. I extracted a good pass z=2 (Good Pass z=2.txt) and the bad pass z=12 (Bad Pass z=12.txt) and compared them using kdiff. Upon doing so I discovered that the gcode that failed was totally fine.

Next, based on the replies so far I decided to see if it is a hardware issue. I took the dust boot off and removed the material and ran the program. To my surprise, the program ran and finished with zero issues. I put back the material and ran the program without the dust boot, and the program finished successfully. For whatever reason my dust boot is binding at the specific depth and angle of the cut. I believe the bristles around the dust boot are too long and will trim these to see if it resolves the issue.

Thanks to everyone who replied!