Centroid Community CNC Support Forum

I have an issue and would like some feedback on proposed fix.

I have retrofitted Acorn control system to an early 80's vintage Hurco KMB1 mill. Have everything working so far. I've even made a part shown in one of Intercon videos. My problem is with the home/limit switches. I am using the original hall effect prox sensors. There is only one at each end of the axes (6 switches). I do not have seperate limit and home switches, so I am using each switch for both homing and limit.

Switches are wired in series to Input 1. IN1 is defined as 'HomeLimitAll' in the wizard. The machine homes fine. The problem arises when I snd machine back to home/tool change/park. It trips the limit switches, requiring manually moving machine away from limit. My workaround for now is to move the machine just a bit from initial home and reset machine zero. I wouild like to automate that process.

My proposed fix is this:
Seems like cncm.hom is the subroutine invoked to home the machine. I am proposing a few lines at the end to move the machine say 1/8" from home to move away from the prox sesnor then reset home. The current code in cncm.hom:
;Perform Homing commands
;Disable any assigned limit switch inputs
M94 /105
M92/Z L1
M26/Z
M91/Y L1
M26/Y
M91/X L1
M26/X
M95 /105

Add this to the end:
G91
G1 X.125 Y.125 Z-.125 F10
M26/X
M26/Y
M26/Z

Is this plausible? If so, should I save this as a new file and redirect CNC12 to the new homing subroutine? If so, where is this pointer?

Thanks ahead of time,
Mike

I believe that there is some new M-code that allows one to go out of the "envelope", but I've not used it and don't recall what it is. You could also do just HomeAll, and then set your software limits to limit travel. You could also set your tool change location to only go that close, and edit the Park macro to not go that close either. Your example would/should work as well, just edit/save your cncm.hom file. Make sure the wizard is set to "I will create my own" homing file, so it doesn't get over written.

Why not just edit the .hom file with the code? You can run anything in there that you need. I do some custom maths etc on my Emco Lathe to help with setting up my tool turret (A Axis) alignment.

Mine are set up like below and work. I just use home all and soft limits. If you need to change soft limits for a tool change to go outside of your working area, there is code for that. I can be included in the tool change macro to change the limit before doing the tool change and change back after.

M92/Z L1
G91 G1 Z-.25 F50
M26/Z

M91/X L1
G91 G1 X4 F200
M26/X

M91/Y L1
G91 G1 Y6.2455 F200
M26/Y

Thanks for the replies. Seems to validate my approach. I do have soft limits in place and they have tested good. Once I am a bit more familiar with how CNC12 works, I may delve into playing with the park and tool change postions. For now, tool changes and parking at home postion is not a problem (with this fix).

Thanks,
Mike