Fadal Post Issue, 4th axis rotation

[Max_Marz]

Working on a part leveraging a helical rotary toolpath to do some surfacing, the Autodesk supported Fadal post is having an issue with the A axis rotation on lines that land on A0. 

Program starts up, it sends the A to 0 in absolute and it comes down to start the toolpath.
this toolpath contains at least a hundred rotations of the A axis so everything is going great for the first 10 or so rotations until a point lands on exactly A0. In my case when climb milling the the A axis is rotating in the negative direction but as soon as it hits a line with A0. the machine freezes and it starts rotating the A the opposite direction 359.99 degrees to get back to A0. (eating the part of course) and then continues.

Using find and replace to change all of these codes to A-0. fixes the issue. It's not that big of a deal but since its an Autodesk maintained post and caused a crash I figured I'd report in hopes the post could be updated.

[boopathi.sivakumar]

Hi @Max_Marz 

I think the problem is shortest path is not enabled in the machine so it cause the rotary table to unwind every time it hits its range specified in the machine kinematics.

While post processing you can choose Rotary Table Scale to linear so it outputs continuous rotations as you expected.

[Max_Marz]

Hmm, ok. I had a feeling it might be a machine parameter like that, I will search for it, and try posting in linear as well.
Thanks.

[Max_Marz]

Tried posting as linear which felt like a doh moment but now the rotary is doing a full rotation between every line as the post outputs in absolute with only positive A numbers.

I'm not seeing any configurability in the fadal control to force shortest path on A moves, the manual specifies that movement direction is solely based on whether a negative sign proceeds the coordinate, even on A0 calls.

[Max_Marz]

Searching "Fadal shortest path" through google pointed me to this thread where the honorable Rob Lockwood points out the same issue, a conclusion does not appear to have been reached.

https://forums.autodesk.com/t5/hsm-post-processor-forum/fadal-4th-axis-rotation/td-p/6096907

[contactXV8XS]

Any update on any of this? About to install a 4th onto our fadal and we are using the provided post from fusion360.

[seth.madore]

@Max_Marz @contactXV8XS  would either of you have sample files you can share that showcase this issue?