Limit switches, inertia and controllers

[Neale]

It's a good question, but in practice I don't think that you need to worry too much. I'm using Mach3 and the CSMIO/IP-M motion controller, but I'm assuming that the UC300 is similar in its functionality. I home at 40% of rapid speed (Mach3 configuration parameter); I believe that Mach3 respects the acceleration parameters you have specified for each axis so that it will never try to slow the axis faster than the steppers can handle - assuming that you have set appropriate acceleration/deceleration parameters, anyway! So, the motion controller does not need to brake the steppers as such, it just reduces the pulse rate sent to the stepper as it would for any change of speed. One very useful trick that is not obvious is to arrange the proximity switches (if that's what you are using) so that the trigger passes by it, not heads straight for it. This means that if the axis does overrun for any reason, it doesn't smash the switch! You might think that this will give less accurate trigger points but that doesn't seem to be the case in practice. You probably only need a few millimetres between the limit/home switch position and the physical end of travel, to only for the slight overrun as the first phase of homing completes. Again, I assume that the UC300 is similar, but the Mach3/CSMIO homing process involves driving the axis towards the home switch until it triggers. There will be a little overrun as the axis is decelerated. The axis is then stopped and reversed more slowly until the switch triggers again. The second trigger point is where the home position is registered.

Oh, and my gantry weighs around 40Kg and I have absolutely no problems.