I asked this on the sheetcam mailing list:

I've got a prototrak style setup with a knee mill and only the x and y
axes under motor control. Whats the best way of setting up pauses in
the gcode where mach3 will prompt me to set the z before and after
rapid movement?

Les responded:

Use the Mach2 2D post processor. This inserts M00 stop codes before
every Z move. It also adds a comment telling you the required Z depth.



I just bought mach3 yesterday.  I thought Mach3 was the latest version of the software, and that Mach2 was an earlier version, and mach4 is coming up.  Is there a way to use mach3 the way Les describes or did mach3 lose functionality over mach2?

-Mike

Heya guys,

Another question I have is, when I try to run a program on mach3, it stops whenever it hits a line with Z in it, because I have only X and Y I assume.  How do I get the program to continue on?  I tried next blk and run, run by itself, stop and run, reset and run, etc... and none of them make it continue.  Whats the proper procedure?  I couldnt find it in the manual.

-Mike

If you are using sheetcam to generate the code then I would think the Mach2 post processor as mentioned above should work fine with Mach3.
 Using the post processor should solve your second problem

Hood

If you are using sheetcam to generate the code then I would think the Mach2 post processor as mentioned above should work fine with Mach3.
 Using the post processor should solve your second problem

Hood

*how* do you use the mach2 post processor in mach3?

Use a Mach2 post processor in sheetcam to generate the g-code that goes into the Mach3 controller.

you dont use it with Mach3 as such, it is SheetCAM you use it with. The post processor is to let your CAM package output the correct G and M codes for Mach.
Hood

You do not need mach2, mach3 has all the functions of 2, and much more.

A 'post processor' is part of a cam program that generates the code for one specific machine. Sheetcam has many posts, you need the one that generates 2D code.

What les suggested is to use the  Mach2 2D post processor with sheetcam. It could just as well be called a Mach3 2D post. The 2D part says sheetcam will never call for a Z move- it will put an M01 in the code, which will cause mach3 to stop and wait for you to press Start. You would manually operate the Z, to whatever depth is called for, then hit start to continue the program.

If you try to run a program with a Z move, and Mach is not setup for Z acis, it will hang, as youhave discovered. You should not do that- you are asking Mach to do a Z move that it knows it cannot do.