Advanced CAM software products have abilities not only to identify collisions prior to bringing them to a machine, but also avoid these collisions. When collisions are identified, there may be many alternative cutter orientations that can provide a non-interfering instruction.

What are some of the rules that the software should apply? Are all non-interfering locations created equally? One paradigm used to solve this question is to ask a seasoned machinist. He would seek overall machine axis smoothness, avoid tight spaces, and avoid distant potential solutions by limiting the search to a controlled range.

Key Principles
The key principles to incorporate in the CAM software are to be able to bias collision avoidance moves based on the performance of the two rotary tables, to avoid potential locations that are very far from the baseline (interfering) solutions and to blend deviating instruction orientations with neighboring instructions to ensure smoothness.

The first point recognizes that machine tool rotary axes may have different specifications and the interference may best be resolved by moving the faster, more dynamic axis.

Avoiding potential locations that are far from the baseline solution will eliminate the potential for a very large angular deviation from neighboring points that would likely be accompanied by extra tool length requirements and reduced cutter dynamics.

Further, large orientation deviations would likely provide a sudden change in a rotary axis movement and may invoke acceleration requirements beyond the capability of the axis.

When the commanded NC instructions contain highly accelerating axis motion, the CNC control look-ahead functions will try to resolve these through internal compensations. The control will often depress feedrates (axis velocity) as a means also to reduce accelerations to achievable levels. Such a process may salvage marginal instructions, but will not lead to optimal machine tool performance.

CAM software solutions, especially in challenging cases of collision avoidance, must produce smooth instructions so that the control system does not invoke these override mechanisms. The intention is to create CAM software results that can be performed by the machine tool.