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What do dogs and golf have to do with machining? Knowing could prevent a crash!

Golfers refer to a hole that is crooked or has an abrupt turn, like the back leg of a dog, as a dogleg. Those in CNC refer to rapid motion that is not straight as a dogleg rapid.

Dogleg rapids occur on machines that move axes at their maximum speed at all times. When this machine tries to rapid further in one axis than the other, one will arrive at its destination first, while the other continues its journey. This results in that crooked, almost L shaped motion.

There is nothing wrong with this motion except that your CAM software may not be using the same motion in its verification or simulation. This is where you need to know what types of rapid your machine is creating, dogleg or linear, and set your CAM software to do the same. Otherwise your perfectly good simulation in CAM could result in a crash on the machine. 

Some machines are even capable of switching between the two modes via a parameter or switch. If you have the ability to choose, I would suggest going with linear as most CAM systems will default to this motion. 

Mastercam has toolpaths which will allow you to force retract rapid motions into high feed motion instead. This is another option for controlling the rapid motion on machines not capable of linear rapids. 

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