Odd Dive behaviour on Rotary Tube

I’ve been using Sheetcam for what seems like forever.
We now have a rotary profile cutter that we cut HSS square tube on.

I’m having an odd issue with how the code handles the corners.

As you can see in the red circled areas, the Z axis dives to cut height while still in the corner.

I’ve found the section of code where this occures:

N57610 X1.7346 Y0.9005 Z4.1234 A-121.6125
N57710 X1.7325 Y0.9515 Z4.1109 A-120.8386 ← I’m still at 120 deg
N57810 Y2.6985 Z3.0900 F9963.9528 A-90.0000 ← This is the issue , it dives from 4.11" to 3.09" while rotating 30 Deg
N57910 Y-2.7250 F59.7073
N58010 Y-2.5141 Z3.3072 F14961.4939 A-85.2744
N58110 Y-2.2817 Z3.4894 F13782.6132 A-80.9223

I can supply the full code if needed. I have 2 of these events on this one part.

Here is the other:
N64510 X5.5389 Y0.5987 Z4.1827 A53.8552
N64610 X5.5433 Y0.8282 Z4.1399 F13234.6662 A57.2957
N64710 Y2.7119 Z3.0900 F10877.1486 A90.0000
N64810 Y-2.7377 F59.717
N64910 Y-2.5021 Z3.3174 F36934.0906 A94.9575
N65010 Y-2.4047 Z3.3966 F13782.6257 A96.8073

This one starts to dive Z with over 32 degs of rotation left.

Here are how the other corners look like, these are fine.

59610 X1.8709 Y2.2741 Z3.4949 A-9.2152
N59710 X1.8847 Y2.5402 Z3.2849 A-4.2205
N59810 X1.8986 Y2.7466 Z3.0900 F9830.8464 A0.0000
N59910 X5.4005 Y-2.7453 F59.8311
N60010 X5.4035 Y-2.5001 Z3.3190 F53516.1595 A4.9947
N60110 X5.4065 Y-2.4432 Z3.3658 F11634.3889 A6.0805

The Z dive to cut height only has to move 4 degs on this one.

I’m stumped as to why it’s doing this. I tried changing the starts to make the rotation clockwise , but i’m still getting the issue.

What post processor are you using?

I’m using both my own post and your PlasmaRotary Mach3 post.

I’m putting together a package with all my testing to send to you, if that’s alright.

The basic issue is always the same in both posts, when it wraps around one corner, only one corner now, it jumps the A rotation by a large angle. For example, when wrapping around a corner, the segments all span between 3 and 5 degrees, but when we see the error , there is a large jump in degrees, one of the patterns we have been seeing with our cut pattern is either + 43 degree or -43 degree jumps at the corner.

N21010 X2.2904 Y-0.1397 Z2.8234 A-48.1818
N21110 X2.2891 Y0.0646 Z2.8265 A-43.5291
N21210 X2.2456 Y1.7734 Z2.0900 F14597.3481 A0.0000

Also to note: The simulation in sheetcam is always fine, but the error is visible in the generated Gcode and in the toolpath generated by mach3


Sure, send your test files to me. Sim is basically just a custom post processor so it’s odd that the issue doesn’t show up in simulation.

I always found it off that the Sim was showing very different behaviour than the actual code. Good to know.

Where would you like me to send them?
I can send you the Gcode that we produced, my post and the DXF file.

Sorry for the delay in replying. Could you email them to me: les@sheetcam.com

Well, that took some finding. I will try to upload a fix in the next few days.