Not cutting all the way through?

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Mackerethwoodcraft
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Joined: Sat May 21, 2022 1:13 pm
Model of CNC Machine: Quintax pacer 2500

Not cutting all the way through?

Post by Mackerethwoodcraft »

Ok another question. I’m new to this, I’m cutting out cabinet parts and trying different things with making programs ect. I am finding that i often am having full sheets of parts that don’t cut all the way through, they’re left with a very thin layer between the bottom of the cut and the spoil board, for the whole sheet. When it does it, it happens to the whole sheet, and when it doesn’t it doesn’t at all. furthermore if i try to fix it by changing the depth and running it again it cuts high. Example .625 sheet thickness.625” cutting depth leaves me with maybe .005 “onion skin”. So i change it to .625 sheet .630 cut depth and I’m cutting air 1/2” above the sheet now?
I’m starting to think i may have to put in the final pass depth? At .125 or something, i know i have sometimes and I’ve just done 2 passes sometimes. I’ll have to do some troubleshooting.

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Adrian
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Re: Not cutting all the way through?

Post by Adrian »

That's really odd. There's no way what you're describing should be doing that. Are you sure the Z zero is being set correctly?

Mackerethwoodcraft
Posts: 10
Joined: Sat May 21, 2022 1:13 pm
Model of CNC Machine: Quintax pacer 2500

Re: Not cutting all the way through?

Post by Mackerethwoodcraft »

I’ve got z set as machine bed, and have done a tool set and bed check several times. I’ve even tried setting the bed deeper than it should be so it would cut like a 16th into the spoil board, then do a tool check run it again and it still doesn’t cut all the way through. It’s very weird, I’ll do more today, i don’t know why but i think it worked better when i did set the final pass at .125, but I’ll have to try again to confirm that. I’m running super old software on the computer that runs the machine and it’s very finicky

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Adrian
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Re: Not cutting all the way through?

Post by Adrian »

So i change it to .625 sheet .630 cut depth and I’m cutting air 1/2” above the sheet now?
That's the bit that is really confusing me. I don't see how that can happen.

There are various reasons why the machine not cut exactly the programmed depth specified such as the Z being pushed upwards with the downwards force especially if you're not ramping into cuts with bigger bits but that air cutting bit has me baffled.

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adze_cnc
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Re: Not cutting all the way through?

Post by adze_cnc »

That air-cutting also confused me when I saw it. I could only see it happening if there was a difference between where the machine and the software think z-zero is.

One other reason for not cutting through when z-zero is at the machine bed (spoilboard) is a humidity change. On a long cut I have found that my vacuum pump can sometimes suck enough moisture out of the MDF to make it shrink in thickness by a few 1000ths of an inch.

Mackerethwoodcraft: I've got in the habit for each job of creating a document variable called oc which stands for overcut. Normally this is always 0. When I'm cutting through a piece I will set the depth of cut to the formula: t+{oc}

That is "material thickness plus overcut".

So, if I get into a situation where it is not cutting all the way through or where I want to force it to cut all the way through and a bit into the spoilboard I can set the oc variable to a small amount (e.g. 0.004)

So, for your test file that you are setting to 0.630 depth of cut you create an oc document variable and set it to 0.005 then change the test cut's depth of cut to: t+{oc}

Does this run above the material?

Note: when creating the document variable use oc without braces. When oc is used in the formula it is enclosed in braces. For more on document variables see this

Mackerethwoodcraft
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Joined: Sat May 21, 2022 1:13 pm
Model of CNC Machine: Quintax pacer 2500

Re: Not cutting all the way through?

Post by Mackerethwoodcraft »

Oh i like the over cut tip! I did get it figured out. My xmc program on the machine is old and I’m still figuring it out, turns out when i was setting the toolset from the main console it wasn’t actually setting the manual toolset, it said it was but when i did a bed check it was just a hair above. I finally found if i went into the engineering tab and did the toolset in there, it actually changed it.

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adze_cnc
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Re: Not cutting all the way through?

Post by adze_cnc »

I'm that it worked out. Attached is a sample using two document variables (ps and pc) as a typical file I might create when cutting "Baltic" (Euro?) birch plywood whose surface splinters notoriously when using an up-cutting bit.

Two toolpaths: pre-score and finish. Check the finish toolpath for a "complicated" way of combining the ps, oc, and built-in t variables.

Steven
Attachments
doc variable sample.crv
Created with VCarve v9.519
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