Strange router issue...

[rrc1962]

I've never seen anything like this before.  It gets about half way into the program and at the same exact point in the program, the Z plunges about a 1/2".  The Z DRO DOES NOT reflect this.  Last time it did it, I hit the estop.  The Z was clearly at about -.5000 but the Z DRO said -0.008 which corresponds to the program.  Here is the code.

N7450 G0   Z0.3750
N7460 G0 X1.2493 Y0.1734
N7470 G1   Z-0.0128 F20.0   --------Problem occurs right about here.
N7480 G1   Z-0.0099 F50.0

I'm not sure why it's making a Z plunge move followed by a Z feed rate move.  F20 is the plunge feed attached to the tool.  F50 is the feed rate.  Either way, I don't see anything that would cause a Z plunge.  I ran this program 4 times and it did the same thing at the same exact point in the program every time.

N7490 G1 X1.2984 Y0.1805 Z-0.0170
N7500 G1 X1.3083 Y0.1856 Z-0.0220
N7510 G1 X1.3482 Y0.2162 Z-0.0526
N7520 G1 X1.3582 Y0.2202 Z-0.0566

Has anyone seen anything like this?  This is a new setup and it's been a while since I set up a router.  I'm not used to dealing with 3D tool paths.

Thanks.

[ger21]

At line N7450, is the tool .375 above the work?

Perhaps it's losing steps on a previous move and not noticed until it plunges there.

[rrc1962]

Good call Gerry.  I didn't hear the missed steps with the router running.  I bumped the speed and accel on the Z back a tad and all is well.

Thanks.