Using Touch Off with Soft Limits

Hi, hope this is the right place for this. I'm having a hard time setting up my project. I used MeshCam to create the G-Code and have my 3 axis machine homed. It's a 2D cut. The problem is when I load the file, it displays outside the cut area(red dotted area), so I used the Touch Off button to adjust each axis. But then I get an error for exceeding soft limits. What am I missing?

O.K.
Make sure you have a g code for a part that will fit in the working area of your machine.
After you start linuxcnc you home the machine, then jog the machine to where you want to start working, the touch off your axis there.
If X0 Y0 is the lower left corner of the work and Z is the top of the material, jog to that position and touch off as X0 Y0 Z0.
Or jog to whatever position MeshCam used as a reference point and touch off there.
Make sure your machine and the g code are in the same measuring system metric or imperial G20 G21.
Which axis shows the problem?

Rick G

Alright, so I was able to change the G Code to run within my work area. I'm having problems with the Z axis. I guess Im not sure whether its something in the CAM or in LinuxCNC I should be tweakin but Im looking for the right way to set up the Z. I broke a couple bits already.

I have never tried MeshCam, so perhaps someone who has will jump in.

I would Start with your Cam set up. Normally there is a section where you set up your material. length, width, thickness and safe Z travel height.

If you set Z 0 as the top of the material in your Cam program and all cuts are downward. I also set my X0 and Y0 to be the lower left corner of the material on a router or the top left if using a vise on the mill.
The important thing is that both the Cam program and linuxcnc are set the same.

If your Cam is set for Z 0 as the top of the material jog your Z axis down to the top of the material and then "touch off" Z as Z0.

This might help...
gnipsel.com/linuxcnc/g-code/mill02.html

To avoid breaking bit try setting Z above the work and let the machine "air cut" the part to see what is going on.
You can also post the code you created for us to look at.

Rick G

Also take a look at your meshcam setup as you can specify where the part's origins are. Typically you want Z0 to be at the top surface of the blank but I've often seen imported CAD drawings force this to deeper into the model. If so change it within Meshcam.

Watch out for tool length compensation..!

Tool length compensation can give "unexpected" shifts in Z-level. You can read the current compensation from the "TLO Z" value in the DRO.

If MeshCam is configured to use tool length compensation, you will have to manually load the requested tool in LinuxCNC and enable the tool length compensation with "G43", before you make the Z-axis touch off.

I really think my problem is in Meshcam. Setting up the Z 0. I tried a few different heights and tried those different programs and it's getting closer to where it should be. There's an option in Meshcam to set Z0 as Top, Middle, Bottom of material, but even with this code, when I try to run it, the bit doesnt reach the material. It 'air cuts' it. Right now, after I home all 3 axis, jog the Z to top of material, Touch Off as ZO, the project shows a little below that point, maybe an couple inches. This seems to be causing the problem, so I then Touch Off the Z to a number that brings the project closer to the bit in the GUI. I'll have some time tonight to mess with it again. Thanks for the replies. Closer to getting this thing running.

if you set meshcam to the top of the material as Z0 then it should show that as top , not 2 inches below , are your datums all the same i.e all Inch or all metric
if you first make sure all compensations are turned off and the repeat the exercise . before working with tool compensations

what kind of mill and controller do you have. I think maybe that you're Z axis is trying to run 'reverse' which I have seen before on some new system setups.

In addition take a look here...

wiki.linuxcnc.org/cgi-bin/wiki.pl?Coordi...t_what_should_you_do

Rick G