Generic 5ax Post - Primary is flipping to keep secondary positive

[huskermcdoogle]

So I have a post which is generic 5ax based and is causing me some trouble.  I have an operation where I want to rock the secondary back and forth as I zig-zag the floor to keep a lead angle on the tool.  When I post it out, the machine is flipping the primary to keep the secondary positive, if the primary would just lock, the secondary would just go back and forth +/- 15 degrees.

Is there a way to get the generic post to respect this type of movement?  I would like to just have it respect shortest axis movement....

I am going to put in a request to the original post writer, but they are in Italy, and sometimes the language barrier can be a pain.  

[MIL-TFP-41]

Check what mi10 is set to. Sometimes inside the post it is forced to be negative or positive, so look for that also

[Alex Dales]

It sounds like the issue is occurring when your Secondary axis is at (or close to) zero degrees (instability), at which point your primary axis is rotating 180 degrees, and your secondary axis goes back the save direction it came from instead of taking the alternate solution.

Without adding custom logic, your post will always want to rotate the primary axis when your programmed toolpath crosses vertical. This allows it to maintain the same tilt solution (secondary axis) since most post processors resolve for the Rotary based on bias toward one tilt direction. There are ways around this, but they can be difficult to implement and will most likely require access to the encrypted section of your post. 

Your best bet to getting around this limitation would be to define a new axis combination that only contains your secondary axis. This will ignore your primary axis and eliminate the possibility of a second solution. In this way the Primary axis will not move, and secondary axis will be free to cross past zero degrees without triggering an instability. This will work best if your Primary axis is fixed at zero. If it need to be fixed at another angle, we might need to get more creative with the solution.

[huskermcdoogle]

Yeah axis combo's do squat nothing with the output in this case.  I'm ok for now, just something I will have to get after eventually.  But this issue comes up often, and I need to get going on controlling it.   I guess I need to get going on building my own 5ax post from scratch, I know enough to get going, and have some good common sense ideas on how to prevent this issue without much extra logic,  just need to figure out what features I need in the post in the first place, axis combo's controlling axis output will be on top of the list as this is a six axis machine.  The post currently uses a user question to switch between H/H and H/T, need to get that all back into the file to make posting easier.