Fanuc 15-M G41G2 small arc glitch?

Okay so I program several different Fanuc routers and I occasionally have an issue with some of the older 15M controllers cutting full circles when they should only be cutting a small arc when tool radius comp (G41/G42)is applied. The same move with a G40 and it will cut the small arc just as it should. A G41 or G42 with even a zero in the offset value and it glitch.

This doesn't happen with every program I send but I will send dozens of different programs in a single day. I don't have time to run a dry cycle before every job.

And yes I have tried using I and J instead of R.

Is this a common issue with older controllers or is there something other than not using tool comp to ensure this won't happen?

Post code where this happens and maybe someone will spot something obvious.

Otherwise??

Okay here is an example.

This move makes a hexagon with radius corners with a lead in and lead out. Two of the arcs came out as full circular moves. The second and fifth arcs I believe. And like I said I tried posting this with I and J rather than R as well and got the same results. Only if I replaced the G42 with a G40 would it cut correctly. My offset value had no effect.

I ran this same code on another newer 15M controller and did not have the problem


G90 G0 G54 G40 X30.0453 Y7.3409 D1
G43 H1 Z1.
G0 Z0.25
G1 Z-0.222 F60.
G42 X29.6954 Y7.9421
G3 X30.3759 Y9.1258 R1.3692
G1 Y25.2682
G3 Y25.2694 R0.3478
X29.6957 Y26.4477 R1.3672
X29.6946 Y26.4483 R0.3478
G1 X15.7173 Y34.5213
G3 X14.3509 R1.364
G1 X0.3695 Y26.4483
G3 X0.3686 Y26.4478 R0.3478
X-0.3118 Y25.2688 R1.3662
Y25.2679 R0.3478
G1 Y9.1258
G3 X0.3682 Y7.9424 R1.3692
X0.3697 Y7.9415 R0.3478
G1 X14.3498 Y-0.1307
G3 X14.3536 Y-0.1329 R0.3478
X15.7159 Y-0.1321 R1.3836
G1 X29.6954 Y7.9421
G3 X29.7466 Y7.9734 R1.3692
G1 G40 X30.1225 Y7.3881
G0 Z1



WTF?

I see a couple of things I don't quite understand:
1) I always thought that the approach move should be as close to 90 degrees to the next move as possible.
2) I can't tell for sure but it looks like you are cutting on the "inside" of the hex profile but are using G42 which given the direction of the moves should be a G41.
Also, there are places with 2 or 3 moves in G3 mode successively (some of them not stating an end point on one axis or the other) and unless this is deliberate (to produce some "ornate" features, might be the source of the complete circle moves you talk about.
Maybe a drawing of the part and telling us whether you are keeping the "inside" or the "outside" of profile?

-I generated the code with Alpha-Cam. I selected for it to roll around corners that's why each arc is broken into 3 arcs.

-I can use lead in and lead outs at any angle as long as it doesn't hit that part or the parts around it and it has both an x and y move.
Also I program using zero radius comp to I only have to comp for a few thousandths at time. I am less likely to get a CRC error that way.

-This move makes a counter clockwise outside move around the outside of the part. It's conventional milling, that's why it call up G42.

Mathematically this works out perfectly. If the G42 was changed to G40 it would follow around the outside exactly as it should and since I use zero radius comp the code is already stepped over for the radius. The G42 is only there so that I can comp for tool ware. The offset value has no effect on this glitch.

9 out of 10 programs I make never have a problem. I would like to figure out why exactly it is happening so that I can avoid it.

I have noticed that it usually only happens on very short arc moves. Usually less than .010" long.