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Trouble with soft limits, slow zone
« on: March 22, 2015, 08:38:53 PM »
I've been working on the initial setup of my new woodworking CNC.  I have my motors tuned, my soft limits set, and all my axes moving in the correct direction.  I am able to REF ALL and zero out all the axes in machine coordinates.

The problem comes with the slow zones and the axes moving away from the home switches, as shown in the "Homing, Limits, and Offsets" video.  When I REF ALL, the machine goes to the home switches at full speed and stops abruptly at the home switches.  It does not slow down on approach or move off the switches.  I have my slow zone set at 1".  The only time I am able to get a slow movement is when I am jogging the Z at both extremes of my soft limits.  Any suggestions?

Also, the presenter in the video (sorry, never caught his name) said to go to the diagnostics page and toggle the home switches.  Mine do not toggle on and off like he shows, so I'm not sure what that means and if that's and indication of anything.

Are slow zones suppose to always work when your soft limits are active, whether you are toggling, REF ALL, running a program, etc?  I understood it to be a safety measure that is active all the time when the soft limits are active, but maybe I misunderstand.

I have included a couple screen shots that may help.



« Last Edit: March 22, 2015, 08:43:16 PM by AndyMS »

Offline Hood

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Re: Trouble with soft limits, slow zone
« Reply #1 on: March 23, 2015, 06:27:35 AM »
Slow zones are only meant when jogging via keyboard or MPG, they will not slow the axes down whilst homing.
When you home the axes should move, one at a time to their respective home switches at the % of full rapid you have set, for example if you have 100ipm set in motor tuning and in Homing and limits you have 20% then the axes will move at 20% of 100IPM which is 20IPM.
Once the home switch is seen the axis will back off and when the switch goes inactive Mach will set that as the Home position (Machine Coords Zero) Unless you have a Home Off value set, if you do then Mach will set the current position to that Home Off value in the machine coords DRO.
Worth noting Home Off stands for Home Offset and is NOT the amount Mach will move away from the switch once homed, it is the value that Mach will set the machine coords to. For example, say your X axis is 100 inch long and you  home to the right side of the X axis, you would then set 100 in the Home Off box and when you Home Mach will set the machine coords DRO to 100, that will mean Mach knows the machine coords zero is 100 inch to the left.

Rearding toggling the home switches and watching on Diagnostics, what is meant is you physically trip the switches and you should see the corresponding LED light up on the diagnostics page.

Re: Trouble with soft limits, slow zone
« Reply #2 on: March 23, 2015, 08:48:53 AM »
Thanks for the reply, Hood.

I suppose I had the wrong idea about the slow zones.  Once all limits were properly established, I expected it to serve as a safety net that would shut down the program and machine if you went out of bounds during jogging or running.

It mostly sounds like everything is working as it should with my homing, except for moving away from the axis once the switch is seen, or at least I can't visibly see it moving away.  The home switches have a red LED that is activated, and they stay on when the machine is homed.  I have to jog away for the led to go off.

Toggling the home switches in Diagnostics doesn't light up the boxes, but the machine switches seen to work fine.  I'm not sure what the deal is there.
Re: Trouble with soft limits, slow zone
« Reply #3 on: March 23, 2015, 09:04:24 AM »
I had the same issue on my knee mill after I upgraded to servos; 1" just wasn't enough space for Mach to slow the motor down from full speed. It would work fine on a slow jog gut not at full rapid. Changed the slow zone to 1.5" problem solved.