What do the limit switches do that mine might not be?

X-carve built and cutting fine although arnt getting the limit switch thing. On starting a carve and going through the setup the machine slowly moves and touches the switches. I then select a home position, but if you accidently over press the arrows to select home position it will just squash the switches and wont actually stop when they click?

Ah, I can explain a bit, at least.

When you first start the system, since the X-Carve uses stepper motors instead of servos, the controller has no idea where the spindle is. So it runs the axes slowly, Z first, then X and Y together, until it hits the limit switches. When those trigger, it knows it’s reached the end of that axis, and once all three have triggered, it knows exactly where the spindle is so it can start counting steps on the motors to know where it is in the future.

Once it has homed, the switches have no additional function. If you order it to go beyond the position of the switches, it will do so without question, since the switches are not active after homing. They would be much better called “Homing Switches” than “Limit Switches.” They are very useful, though, since it lets you set the home position automatically. And once you have that set up, your G28 “Home” will always be in a predictable, sane place.

With some addition work, they CAN be used as “hard limits”, in which case tripping one of them after homing will cause the unit to “alarm out” and freeze in place. Unfortunately, the steppers cause enough electronic “noise” that false positives are a big problem. A good solution to this is enabling the “Soft Limits” in the GRBL settings. Once you have defined those, if you attempt to move beyond the defined size of your rails, the system will error out without any switches being tripped at all.

Dan mentioned G28 - this post has alot of awesome on that topic. Must-read for us all - imho