Depth per pass confusion

I am cutting a relatively delicate shape out of 1/8 ply. I’m using the #122 .0.321 with default hardwood settings, but I have changed the depth per pass to .025. Stock thickness set to .125 and probe used to set z. Stock is tight glued to wasteboard. What is confusing me is that the initial plunge and pass is much deeper than .025. The machine repeatedly is cutting almost through the entire stock on the first pass. I have recalibrated, reset the tool settings, toolpath and gcode but always with identical deep results. Max depth is set to stock thickness based on top. I am still using the latest version of Carbide Motion. Assuming plunge rate should not effect this? What am I missing?

My SO3 has been tightly squared, bed leveled and calibrated am working wonderfully.

I looked at my CC 4.62 and the #122 showed up for the Nomad with 0.015 and 0.010 depth per pass depending on material (hw vs sw). So I would have to assume that your zero is not setting properly. Set your zero with the touch probe and jog the bit down to the Z zero position and see if it is really sitting on top of the project. With such a small bit the touch probe may not be setting properly and the bit is overdriving before it recognizes contact with the touch probe. Also try setting your Z zero with the paper method. If you dont want to damage your plywood set the zero and then jog to a set depth like 1" and measure if it is really at the height or is lower. You problem almost has to be that the bit is not set at zero at the stock maximum height of .125". Also double check that the stock is completely flat and not raised in some areas by your method of fixing to the waste board.


also, maybe post the G-code and/or design file for a quick check ?

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How sure are you that you didn’t probe in overhang mode but had the probe on top?


Thank you! I did use the probe in overhang. How do you change the mode?

Thanks. Great suggestions. Will try them

Ah. That’s it. I found the tutorial. I was doing the z calibration wrong.

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I changed my method for calibrating the z-axis with the probe - no overhang. When I calibrated with the probe then calibrated with the paper method I am seeing a -.50 difference (probe under estimating z depth). What could cause the probe to not calibrate properly?

-0.5mm ?⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

half an inch would be a bit steep :wink:

Calibrate for belt stretch?

@fenrus indeed, but usually when people around here omit the units, it’s imperial :slight_smile:

@zbartrout: is your stock PERFECTLY flat in the corner where you probe ? It’s easy to not see a 0.5mm bump, the large-ish probe would not sit perfectly flat, while a paper method contacts the endmill in a very specific place

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I have a threaded insert supplemental spoil board. I had surfaced the spoil board and started getting irregular depth cutting projects. When I initially put the spoil board on I had measured the maximum depth of my 1/4-2- bolts for my hold downs. After surfacing my bolts were just a bit too long and made the supplemental spoil board raise up due to the bolts bottoming out on the stock base. I went and got shorter screws and the problem was fixed.

If you have an MDF spoil board moisture can make it bumpy and have high spots. So check your height in various places on the spoil board and see if you either are pushing it up with hold downs or moisture is making your spoil board bumpy. MDF is very pours and soaks up a lot of moisture after you take the hardened surface off. Even if you still have the hardened surface places where you cut through can soak up moisture.

My touch probe sets just as the bit touches it. The paper method almost always results in a lower zero because you have to drive the bit into the paper a little to feel the paper stop moving. If I am going to carve a very shallow v carve and use the touch probe I generally check it with paper or just jog in an open space and set it 0.01 inches lower and rezero. The difference between the touch probe is the touch probe is more exact where the paper method is subject to variations.

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