Richard- You are facing precisely the same issue I just worked around on a 1988 Hurco KM3 that I am retrofitting. It has two proximity switches per axis (X & Y) that inhibit further travel in the undesirable direction once activated. The switches are wired to both the control computer and to the CMC servo amps.
I'm told many servo amps have limit inputs but I don't know how many machines also use a limit for homing. With the amp limit inputs providing a hardware safety, it seems pretty natural to use a limit for coarse homing if index pulses are used for fine homing, rather than incurring the expense and complexity of separate switches. I like the hardware safety feature that does not depend on the state or health of the controller, but as you found this configuration does not play well with EMC. What I did (for the moment) is to use one of the two proxes to detect either end of travel. I disconnected one prox signal at the servo amp and jumpered the other one to both inputs. I also moved one of the stops inboard by the distance between the proxes (which are center-mounted with the stops outboard). That leaves the second prox within the allowed range of travel for homing. Manual recovery from hitting a limit prox is required but this is an abnormal condition that should occur infrequently, if ever. I would of course prefer a cleaner solution in code. :) I am also using an M5I20 and late last night got homing using the index working (I think) on one axis. I am getting a following error half-way to my offset home position during the rapid move afterwards, likely due to tuning or some other configuration problem, but the homing part of the cycle seems to work fine. The FE is tonight's project. Chris -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Richard Arthur Sent: Wednesday, June 13, 2007 3:30 PM To: [email protected] Subject: Re: [Emc-users] Homing and f-error Thank you for your replies. I would add that this is a retrofit to a Hurco KMB1x circa '85. The limit switch arrangement is original. Maybe other manufacturers used this arrangement, in which case other users may face this problem. I have to confess, I was hoping for an easier solution than fitting homing switches. ;-) Does EMC need to be concerned with f-error once a limit switch has been hit? Of course, leaving FERROR set to about 0.005 thou allows homing to function (less if I drop the HOME-SEARCH-VEL), but I would like to tighten that. On a slightly separate point, I had hoped to use the index for homing. Setting HOME_USE_INDEX = TRUE in the m5i20 .ini seems to leave the index pulse 'switched off' during the homing sequence. Am I missing something? Richard ------------------------------------------------------------------------ - This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
