Plunging .9mm too low?

I’m having a bad day.

I have the following file:
Crown Hole Covers - 1 Up.c2d (92 KB)

The stock is measured exactly at .875" thick - which is what the job settings calls for:

I’m zero-ing using the paper touch method to the top of the board - as I always do. Bit setter is on. I’m only using one tool … and that tool has been in the machine since it was initialized.
[EDIT] Note: I also reinitialized the machine as a check

When CM brings in this file, it says “Cutting below stock: 0.00 in”
The side view looks like all of the cutting is within the stock.

But when I go to start the job, I get the warning that I am going to plunge .9mm too low.

I’ve checked all the toolpaths and do not see anything “lower” than ‘t’. There are only three toolpaths…what am I doing wrong here?


Since it’s .9mm ; which is .03 inches…I’m going to go ahead and run the job.

Is it possible that my stock is really .035" thinner than I think it is? Would CM catch that?

Carbide Motion is determining that the machine will run out of travel by that distance if it were to cut the entire job with a tool which has the current length offset — if you’re for example using a short V tool for the first part, but a longer square endmill for the Contour cut which actually reaches the bottom the warning will not apply.

I don’t fully understand that, honestly. The job only has one bit in it (1/8" straight bit). However, I ran the job anyway - and the bit never even broke the bottom of the board…so I’m really confused. I caliper’d the board and it’s exactly .875" all around…and I’m certain that I zeroed until the paper was trapped by the bit…so not only did it not plunge through - it didn’t even cover the ‘t’ depth. Strange.

It’s comparing the toolpath envelope (min/max values for all 3 axes) to the machine envelope that was set in the setup by choosing your machine, using the zero point set in machine coordinates.
The message means it thinks you will hit the lower Z limit before getting to the depth you programmed.
If you can touch off that tool on the spoilboard, then the limits in CM are off, and you are OK to cut the job. But if you are not reaching full depth, you may actually be hitting the physical limit of the Z axis??

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Nope…not hitting bottom of Z. I’ve never had any issue with this before…and if you look at my spoil board, you can see I’m often cutting a bit into it - and there are lots of shallow remnants of jobs gone by. I’ve stopped for the day, but tomorrow I’ll go back and see if I can touch the bit to the spoilboard…that’s an interesting possibility…but why start now?

Bottom of Z motion if the entirety of the file was cut with a tool which was the length of the current tool.

I’ll check it and report back (the bit is still in the chuck). I’d be very happy if that’s the issue.

@WillAdams @Tod1d I checked it this morning - and you guys were right! It could not reach the spoilboard. I had to lower my spindle in the bracket so that the bit I was using could touch - and that did the trick. I’m still getting my head around how CM thought I’d plunge below my workpiece…but I can live with that. No issues with my machine…I’m happy.


  • Gary
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So…this issue has me thinking…
CM could know if I had the situation where my bit would not be able to reach the depth that it’s supposed to for a given job. It knows the length of the bit - and how far down the Z has to go to hit my bitsetter - it knows where the top of my board is - and how far down the job wants to cut.

In this case, the correct message should have been - “You will not be able to cut to the depth your job is requiring” - rather than - “you will plunge .9mm too deep” - I assume that this is the situation the message was trying to convey…since it went away as soon as I moved the spindle down.

Perhaps the message could be updated to reflect what’s going to happen?

good point. The appropriate message would be something like, “The current toolpath will exceed the machine axis limits.”

CM doesn’t know the tool length, or the Z position of the bitsetter, or the Z position of the stock, or the Z position of the table.

It knows the machine coordinate when the current tool hit the bitsetter, and the machine coordinate when the current tool was at the workpiece Z zero. It knows the min/max values in the toolpath, and if set right it knows the axis limits of the machine.