Max cutting depth - protecting my machine's bed

[craigspc]

Hello everyone,

I'm very new to cnc, so please forgive me if I'm going to ask a silly question here!

I've set up Mach3 on my PC and I seem to have everything configured and running OK with my small CNC mill. However, I am still somewhat confused about the Homing/Limits configuration in Mach 3 - Specifically the for the Z Axis.

I have figured out how I to set the limit for the Z axis to prevent cutting through my machine's bed. However, every time I change between End Mills/Cutters (quite often), I have to manually zero the z axis on top of my material, recalculate a safe cutting depth, then go back into the Homing/Limits config and change the limits to ensure that I don't cut through the base of my machine.

Is this something that I simply have to live with, or is there a simple way to automate the process? I'm rather lost here. Can anyone help?

Thanks,
Craig.

[neilw20]

I set the soft limits for Z so that the head stays within it's limits.
Not to stop the cutter chewing up the table.

The head does not know what the length of the tool is so it is not much good using the physical limits for that.

When you put a cutter in you need to set the Z reference point, being the end of the tool and the top of the job (usually).

I put in the new cutter bring it down the the job, or a spacer block, and hit zero, or enter the height of the spacer block in the Z DRO. (and hit enter)

Now Z zero is at the top of the job.
If you measure down to the table or vice base with a ruler, and set slightly above this value value in Z-Inhibit field on screen one (it will be a negative value for below the top of the job).

This prevents a program going any lower than this value, but you can still jog down if you choose to.

With a drill cycle I often set this to minus a small amount, and zero the DRO with a center drill. Now I run the drilling cycle but the depth is limited to just spotting each hole.

Change to the drill. Run program with Z inhibit off, or set to protect the table, of the vice now.

For these limits to work you select Z-Inhibit ON (flashing yellow I believe) or you won't be protected in Z !

[ger21]

You could also look at the program limits DRO's and you'll see how low the Z is programmed to cut. If it's into your table, don't run the program.