For 5-axis applications not only does the CADCAM software have to consider actual collisions with the tool and the tool holder, but also the kinematics of the machine tool itself. For 3-axis machining the concern is mainly the tool length and holder ensuring that it can get into each part of the job without a collision.
For systems with just collision detection, the software tells the user that there is a problem and where the problem is, but the user then has to work out what needs to be done to get over the problem for himself. In some cases this can be very complex and requires detailed investigation of the surface topology of the part.
With CNC software such as WorkNC, users can generate the collided and uncollided toolpaths and get information about the minimum tool length required to finish the job. With this information engineers can cut as much of the part as possible with short rigid cutters and restrict to a minimum, machining with long tools. Best of all, the software does all the calculation for you, so that you can be sure of a reliable, safe and optimized result.
One of the benefits of 5-axis machining is being able to cut much more of the job in one setting with the shortest possible tools, minimizing resetting and secondary operations. If the CAM software just pinpoints where there is a problem, which it will do with collision detection, it is likely that the whole toolpath will need to be recalculated after the problem has been resolved. Producing a useable toolpath this way could take several attempts so at the very least it will be time consuming and tedious. With collision avoidance, the software goes a stage further as it anticipates potential problems as you are programming. Again giving the uncollided toolpath and inserting flip and unwind movements where the axis limits of the machine have been reached.
Having intelligence within the CAM software that provides a solution to potential problems as they occur has got to be a lot better than just letting the user know that a problem exists.
Antonius Köster, who uses WorkNC Auto 5 in Germany, gave this example of one of the problems resolved with collision avoidance. “For an aerospace supplier from the Black Forest, we machined a component which required the tool holder to move inside the part through a drilled hole so that we could mill a pocket at the bottom. Not only was the cutter moving inside the part, but the whole tool holder. This was a really challenging task.”


