C axis unnecessary rotation

[mbbert]

I have a problem on a 5 axis DMU160P with TNC530 control. In the code below, the table is already at position, but line 14453 causes the C axis to rotate 360 degrees, back to the same position, while simultaneously moving to depth in Z. This caused the tool to gouge the part.
Is there a way to stop the table making this unnecessary rotation. I know code M126 will rotate by the shortest route. Willl the M126 code reset the axis and stop this unwanted rotation from taking place?

14437 ;
14438 M129
14439 ;
14440 ; SAFEPOINT Y
14441 M140 MBMAX
14442 L Y0. R0 FMAX M91
14443 M55
14444 TOOL CALL 3 Z S4974
14445 TOOL DEF 7
14446 ; KINEMATICS AUTO SET CYCLE DEF 19
14447 CYCL DEF 19.0 WORKING PLANE
14448 CYCL DEF 19.1 A+90. B0 C+33.368
14449 L B+Q121 C+Q122 R0 FMAX
14450 CYCL DEF 32.0 TOLERANCE
14451 CYCL DEF 32.1 T0.010
14452 L X-5.437 Y+18.514 R0 FMAX M3
14453 L Z+435.916 C-146.632 FMAX M8
14454 L Z+432.916 F895
14455 L X-5.973 Y+15.562 RL
14456 L Y+15.522
14457 CR X+1.987 Y+7.522 R+8. DR+
14458 L X+2.046
14459 CR X+10.374 Y+10.972 R+11.778 DR+
14460 L X+24.934 Y+25.531

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[jaideepshinh]

Hi,

Yes you need M126- I faced the same issue with my DMU 50 evolutation wherein we managed to break some tools due to the M126 command being missing. We realised this when we manually edited our 5 axis program and missed out a M126 in the process.

I am not sure if you have programmed this manually or via a CAM software- in our case our CAM software directly post processes the M126 wherever required using the appropriate post processor for our machine.

Basically M126 for the rotary axes considers the angle as 0-360 (and then back to 0) instead of the absolute form (0- infinity)- so supposed you were a 700 degrees before calling the M126 and you needed to go to 0, it would go 700 degrees in the negative direction. After calling M126 it will go 20 degrees in the positive direction instead as 720 degrees and 0 degrees is essentially the same position, and 720 is the shortest path there.

Hope this helps!
Best regards

Jaideep
23

[mbbert]

Thanks Jaideep. That's what I thought, thanks for confirming it. I've already requested the M126 code be added to the post.

[jaideepshinh]

Just for my information, which CAM software are you using?

[mbbert]

Siemens NX12.