G32 / G92 threading w/ T400 controller, examples?

[pfuhlman]

If anyone has an example of using G32 (or G92) to cut a single lead external thread in multiple passes (ex. 1/2-20), could you please post it? The T400 manual does not have a complete example and Centroid claims they cannot provide one. It would be much appreciated!

[cncsnw]

G32 is much like G1. It does a single straight-line move. Unlike G1, G32 waits for the spindle index pulse to come around before starting movement, and locks out the feedrate override control.

You can specify the thread lead (feed per revolution) with either E or F.

Since G32 just does the single move, you need to program the approach, lead-out, and return as separate moves.

Here is an example, cutting 20 TPI into a 1/2" bar. You will have to provide more appropriate cut depths, final diameter, etc..

T0100
G97 M3 S400
G0 X.6 Z.1 T0101
X.48
G32 Z-1 E.05
Z-1.05 X.58
G0 X.6
Z.1
X.46
G32 Z-1 E.05
Z-1.05 X.56
G0 X.6
Z.1
X.44
G32 Z-1 E.05
Z-1.05 X.54
G0 X.6
Z.1
M5
G28
T0101
M3 S400
G0

Note that consecutive moves in the G32 mode, without repeating the G32 code, result in continued thread-cutting movement without waiting for another index pulse to come around.

It takes a lot of lines to program a many-pass thread with G32, but you have complete control over where the cuts happen. For example, you can change the Z starting point (where you rapid to before calling G32) at successive depths, in order to cut with only one edge at a time. If you choose to do the math, you can even alternate edges.

G92 does four (and optionally five) moves in one G code line. Starting from a clearance point (e.g. off the corner of the part) it rapids in to the given X coordinate; waits for the index pulse; feeds along the thread; optionally does a chamfered lead-out; rapids back to the initial X coordinate; and rapids back to the initial Z coordinate.

Because G92 does all the moves necessary to get you back to where you started (clearance, off the corner of the part) you can leave G92 modal and just change the X value for successive cuts (unless you want to change the starting Z as noted above).

The chamfered lead-out is selected with Machine Parameter 49. Parameter 49 is a multiplier of the thread lead. I.e. if Parameter 49 is 1.5, then the lead-out length will be 1.5 times the thread lead. If Parameter 49 is 0, then there will be no chamfered lead-out.

A program example that does essentially the same thing as the preceding G32 example is:

T0100
G97 M3 S400
G0 X.6 Z.1 T0101
G92 X.48 Z-1 E.05
X.46
X.44
M5
G28
T0101
M3 S400
G0

[pfuhlman]

Thank you! That's exactly the info I was looking for. It matches up perfectly with my offline programming system: VCS APT :-)