Alex Joni wrote: > A machine (in my oppinion) would have a home switch (where it would home > consistently). Starting from that position you have software limits (you > are allowed to travel up to the soft limits, and never beyond). > Outside of the soft limits bounds, you have the hardware limits. Usually > these are wired as tripping faults which disable the motor amplifiers, > so crashing them is a serious problem. (One would need to move the axis > by hand back off the limit switch). > On some machines the hardware limits aren't as extreme, and are used > only as a fault input to the controller (emc2 in our case), so if it > trips emc2 errors out. You still have the option to push override limits > then, and jog the axis in the other direction back off the limit switch. > > But yeah, I agree with no home switch (homing by eye) software limits > move according to where you homed. Having limit switches but no home > switch seems like an odd setup to me. I would use one of the limit > switches as the home switch and properly define HOME position and HOME > OFFSET (this scenario is supported by emc2, and described in the docs). > > Regards, > Alex
To further emphasize what Alex is saying.... A "proper" machine ALWAYS has a home switch, so that it homes in the same place every time. If you home in the same place every time, then soft limits keep you from hitting the hard limits (unless something goes wrong). Since you won't be hitting the hard limits by accident every other day, they can be made failsafe - for example they can kill power to the servo amps. For large machines that can seriously injure or kill someone, the above is the only way to go. However, I realize that not all machines need that level of complexity. That is why EMC2 is configurable to work without a home switch. You just jog it somewhere, and say "this spot is home". If you don't go to the same spot every time, soft limits are pretty useless. So set them wide enough that you never hit them. Regards. John Kasunich ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
