I'm trying to size some servos for an upcoming design and am having difficulties determining how much torque I need.
The torque required is going to be related to the screw pitch and the force required. Since as we all know, F=ma, the force required is a function of the mass, the acceleration, as well as the cutting force. The mass is easy enough, and I think the cutting force is probably going to be negligible (or if not, there are formulas to calculate it). The problem is the acceleration. I All the motion controllers that I'm thinking of using use a trapezoidal speed profile for the motion plan. Therefore with faster acceleration it will spend more time at its cutting speed and less time ramping up and down. I'm trying to figure out how to best quantify this though so I can determine the optimal servo size.
Has anyone done anything like this? It seems particularly import with the modern adaptive clearing/volumill/ profit mill toolpaths that are constantly changing direction. Anyone have any 'rules of thumb' for what sort of acceleration levels are optimal? I've heard Teknic will give some guidance if you buy clearpath servo's, presumably they are just using some sort of rule of thumb.
As an aside, I was also reading the
long thread on jerk here, and although it didn't seem like there were any conclusions there, it may be that increasing acceleration to high might cause worse jerk issues since the hobby controllers don't consider it.