CamBam is trying to kill my Shapeoko

pmodiano
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CamBam is trying to kill my Shapeoko

Post by pmodiano » Wed Jul 10, 2013 3:18 pm

This is the third time it has happened. I am now prepared to blame CamBam. If I'm doing something wrong, I don't know what it is.

I was trying to make a sign similar to the one that Edward Ford demonstrated in his MakerCam video.

The CamBam file and gcode file are here.

A photo of the CamBam toolpath is here.

I made a rounded rectangle, added the text, selected all, created a pocket, selected the rectangle and added the profile operation.

I set the tool diameter for both operations to .125", set the target depth for my pocket to -0.2, set the target depth for my profile to -0.8 (the board is .78) and the depth increment is set to 0.015 for both.

It starts out fine at the beginning as it starts carving the first layer but it almost seems that as X moves across the board that Z is cutting deeper until, at one point Z goes bat sh%t crazy, suddenly carving half an inch into the wood, far deeper even than the pocket depth:
IMG_1676.JPG
IMG_1676.JPG (80.3 KiB) Viewed 2535 times
I have had trouble with Z direction before due to Z motor wire disconnection so the first thing I did after hitting the kill switch was to do continuity testing between my grbl and the motor. All was fine, leading me to conclude that the problem must be in the gcode. When I drag it into buildlog's gcode viewer, it looks good.

If anyone has any idea why CamBam is trying to destroy my Shapeoko and what I can do about it, I would appreciate any advice you could give.

Thanks,

Paul.
Shapeoko #1075 1000mm y axis, 500mm X axis, Dual Y motors, ACME screw Z axis upgrade, DW660. http://machinesonthemind.blogspot.com/

pmodiano
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Re: CamBam is trying to kill my Shapeoko

Post by pmodiano » Wed Jul 10, 2013 3:26 pm

I forgot to mention: for both operations, my cut feedrate was set to 30 and my plunge feedrate was set to 10.
Shapeoko #1075 1000mm y axis, 500mm X axis, Dual Y motors, ACME screw Z axis upgrade, DW660. http://machinesonthemind.blogspot.com/

deejayspinz
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Re: CamBam is trying to kill my Shapeoko

Post by deejayspinz » Wed Jul 10, 2013 3:58 pm

A few thoughts and things to check:
- make sure all your connections btwn your controller and steppers are solid. I had a similar issue and it was due to a direction wire coming loose.
- for the pocket operation, did you select the outside (box) and the text, then create a pocket MOP?
- Download OpenSCAM (free) and do a test run of the gcode to see if it reproduces the same issue in the sample cut. If it does, then something is whacky with the way CamBam is generating the gcode. Else, it could be your electronics/connections.

cvoinescu
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Re: CamBam is trying to kill my Shapeoko

Post by cvoinescu » Wed Jul 10, 2013 4:00 pm

It looks like the G-code uses G0 to move the Z (presumably up, but I need to look more carefully to be sure). If your default seek rates are too high for the Z axis (often the case with GRBL), those movements will lose steps, and your Z will get progressively lower. It won't manifest itself until you dug to a certain depth, then it'll suddenly go pear-shaped.

Try using G0 to move Z up and down over distances longer than a few millimeters (say, an inch or two at a time), and see if it obeys you.

I'm not familiar with CamBam, but some CAM programs have the option to use only G1 (feed) moves, which obey the F parameter, for Z moves (or even all moves). Try that. Failing that, set your seek rate much lower in GRBL, and give it another go.
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WillAdams
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Re: CamBam is trying to kill my Shapeoko

Post by WillAdams » Wed Jul 10, 2013 4:19 pm

cvoinescu wrote:some CAM programs have the option to use only G1 (feed) moves, which obey the F parameter, for Z moves (or even all moves).
Also, some Communication / Control programs have the option to limit the speed on the Z-axis (and possibly others).

William
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Tom Smith
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Re: CamBam is trying to kill my Shapeoko

Post by Tom Smith » Wed Jul 10, 2013 4:54 pm

cvoinescu wrote:It looks like the G-code uses G0 to move the Z (presumably up, but I need to look more carefully to be sure). If your default seek rates are too high for the Z axis (often the case with GRBL), those movements will lose steps, and your Z will get progressively lower. It won't manifest itself until you dug to a certain depth, then it'll suddenly go pear-shaped.

Try using G0 to move Z up and down over distances longer than a few millimeters (say, an inch or two at a time), and see if it obeys you.

I'm not familiar with CamBam, but some CAM programs have the option to use only G1 (feed) moves, which obey the F parameter, for Z moves (or even all moves). Try that. Failing that, set your seek rate much lower in GRBL, and give it another go.
This ^^^

CamBam does indeed allow G1 replacement for G0. Alternatively, a search and replace post process of the GCode file in your favourite text editor, replacing "G0 Z" with "G0 F300 Z" (metric) forces the seek movement to a speed the Z axis can handle.

Tom
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pmodiano
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Re: CamBam is trying to kill my Shapeoko

Post by pmodiano » Wed Jul 10, 2013 5:04 pm

Tom Smith wrote:
cvoinescu wrote:It looks like the G-code uses G0 to move the Z (presumably up, but I need to look more carefully to be sure). If your default seek rates are too high for the Z axis (often the case with GRBL), those movements will lose steps, and your Z will get progressively lower. It won't manifest itself until you dug to a certain depth, then it'll suddenly go pear-shaped.

Try using G0 to move Z up and down over distances longer than a few millimeters (say, an inch or two at a time), and see if it obeys you.

I'm not familiar with CamBam, but some CAM programs have the option to use only G1 (feed) moves, which obey the F parameter, for Z moves (or even all moves). Try that. Failing that, set your seek rate much lower in GRBL, and give it another go.
This ^^^

CamBam does indeed allow G1 replacement for G0. Alternatively, a search and replace post process of the GCode file in your favourite text editor, replacing "G0 Z" with "G0 F300 Z" (metric) forces the seek movement to a speed the Z axis can handle.

Tom
I thank you all very much for the help. I will try doing a search/replace and see if it continues its reign of wood destruction. Newbie question: I am using inches in CamBam for this project. What would I say as an alternative to "G0 F300 Z"?
Shapeoko #1075 1000mm y axis, 500mm X axis, Dual Y motors, ACME screw Z axis upgrade, DW660. http://machinesonthemind.blogspot.com/

Tom Smith
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Re: CamBam is trying to kill my Shapeoko

Post by Tom Smith » Wed Jul 10, 2013 5:17 pm

pmodiano wrote:
I thank you all very much for the help. I will try doing a search/replace and see if it continues its reign of wood destruction. Newbie question: I am using inches in CamBam for this project. What would I say as an alternative to "G0 F300 Z"?
Hm, I guess it would be "G0 F12 Z" but you might want to wait for someone who uses inches for their machining more regularly than I :)
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Improbable Construct
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Re: CamBam is trying to kill my Shapeoko

Post by Improbable Construct » Wed Jul 10, 2013 5:57 pm

I am going to agree that it is probably the Z axis trying to run too fast.
It could be the fault of the feed speed but it may also be mechanical.
Double check that the Z axis moves freely in both directions through the whole range of its movement.
With the motor unlocked turn the coupler by hand. It should be easy.
Even a small catch or binding may be enough to overpower your stepper motor causing you to lose steps.
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pmodiano
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Re: CamBam is trying to kill my Shapeoko

Post by pmodiano » Wed Jul 10, 2013 6:04 pm

Of course you must be right, Tom. 300mm/minute = 12 inches/minute. I'll try it out!
Shapeoko #1075 1000mm y axis, 500mm X axis, Dual Y motors, ACME screw Z axis upgrade, DW660. http://machinesonthemind.blogspot.com/

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