Linuxcnc Z Tool Offsets

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Linuxcnc Z Tool Offsets

Post by jmcghee » Mon Feb 22, 2021 9:16 pm

Hey guys-

I’m an experienced manual machinist but 100% CNC neophyte. There’s probably an obvious answer to this, but I can’t for the life of me sort it out. I'm trying to program my Z tool offsets (3 axis mill) running Linuxcnc with Axis interface and am pulling my hair out. I've got 15 or so tools in holders that should handle 99% of the work I'll do. I set all the Z heights in the tool table by doing the following:

-Load the tool & MDI a T(n) M6 G43

-Selected "touch off to fixture"

-Very carefully jog down to a machined flat piece of stock and take a whisper cut

-Hit tool touch off button and leave at 0

I repeated that process for all the tools on the same flat surface. As I understand it, the Z offsets for each tool are now set relative to one another, but not in space.

Then I made a fairly simple program that uses all the tools, with all of them taking a facing cut. My process was to edgefind my origin and hit the "touch off" (not "tool touch off") button in X and Y, load the tool, jog down & take a whisper cut in Z, and "touch off" in Z. I was expecting this process to work (seems pretty straightforward) but it definitely didn't. Using the above it'll cut air, somewhere around 2" above the stock top.

After some advice online I added g59.3 in the MDI before the command above and that didn't work either. Rather than cutting air, it'd start tool one a few inches below the part surface.

I reloaded all my tools 3 separate times just to make sure I didn't make a math error, or change something inadvertently, but no luck. feel like I'm missing something simple, but can't get it. Anyone see something obvious I left out?

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Re: Linuxcnc Z Tool Offsets

Post by GlennW » Tue Feb 23, 2021 7:45 am

You have to set the tool offsets in relation to a master which should be the same or slightly longer than the longest tool.

I use a piece of 3/8 drill rod in a tool holder as my master.

You zero the master and then record the difference in length of each individual tool relative to the master.

I have no idea what Linuxcnc is, so this is just general info.

Operating machines is perfectly safe......until you forget how dangerous it really is!

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Re: Linuxcnc Z Tool Offsets

Post by FKreider » Tue Feb 23, 2021 9:18 pm

Setting tool offsets can vary a bit by controller and machine however Centroid has an excellent video on the topic that may be helpful:

You can also just search around on youtube using keywords- there are a ton of videos regarding tool offsets.
-Frank K.

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