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Help with some basic controls for homing
« on: March 28, 2018, 02:35:30 PM »
I am setting up a new machine with mach 4 and I have some basic operation questions (I am using an ESS for input)

I am setting up my homing switches, they will also be the limit switches. On the diagnostics screen I see they are triggering correctly.

1. When I move an axis to the homing/limit switch, Mach stops movement as it should, and displays the limit switch tripped message. But when I try to move the axis in the other direction (off the switch) it will not move, My switch is my 0 point and I have soft limits set to +40 inches. The only way I can get the axis to move is to disable the switch, restart mach, move the axis, enable the switch, restart mach. So what is the correct way to move off the limit switch once I have hit it?

2. How do I command the machine to go to home position I tried the MDI screen and executing M28, the screen flashed but there was no movement. I verified that home in place is NOT checked for my XYZ axis.

3. On my other machine using mach 3, when I set a point as 0 (hit zero X, Y, Z) then hit the "goto 0" button the machine would move to the spot I had marked each axis as 0. I use this feature alot. When I do the same and hit "Goto work 0" nothing happens. Does mach have the goto 0 feature? If so how do I use it? What does the "goto work 0" do?
Re: Help with some basic controls for homing
« Reply #1 on: March 28, 2018, 02:53:24 PM »
Can the ESS use the same input as Limit and Home switches?  You need to be sure you are able to do that with the ESS.
But to move it once you hit the home switch, it is on the limit and won't let you move the axis.  There is a button on the Jogging Tab called "Axis Limit Override".  This will disable the Over travel switch, once you move off of the switch you can click the button again to turn them back on.   

M28 isn't anything. 
G28 is Zero Return. 

The Go To Work Zero Button does work.  I use it all the time here at the shop as well.
Chad Byrd
Re: Help with some basic controls for homing
« Reply #2 on: March 28, 2018, 03:37:04 PM »
I'm using the ESS on my CRP-4848 router table with the limit switches for each axis wired in serial (Normally Closed) and acting as homing switches. Back when the Mach4 was released I had problems similar to your own. I recently revisited using Mach4 with the ESS and the homing problem is gone.

I'm at work, so without looking at the actual machine I suspect you may need to run the current ESS plugin. Use the ESS settings for homing and set a back off value. If you are running a slaved axis with separate homing switches for each motor, you can set that in the configuration and the ESS is now smart enough to home both motors on the axis independently. It's very cool to watch. I suspect you need to have your homing/limit switches close to the same position on the axis. I used a gauge block to set the distance between the bumper and the limit switch body on my machine. Slaved axis also support providing an additional offset to correct for any angle in the axis, which can be helpful if your limit switches are fixed but slightly off from each other.

-Freeman
« Last Edit: March 28, 2018, 03:39:52 PM by Analias »
I'm not a complete idiot...
    there are some parts missing.
Re: Help with some basic controls for homing
« Reply #3 on: March 28, 2018, 03:43:15 PM »
Hi,
is there any reason not to have separate home and limit switches?. Combining them used to be important years ago
when no one had many spare inputs but with an ESS you have plenty. Why not take advantage of it and use them.

Failing that you'll have to use some sort of limit override.

Craig
My wife left with my best friend...
     and I miss him!
Re: Help with some basic controls for homing
« Reply #4 on: March 28, 2018, 03:52:21 PM »
Hi,
is there any reason not to have separate home and limit switches?. Combining them used to be important years ago
when no one had many spare inputs but with an ESS you have plenty. Why not take advantage of it and use them.

Failing that you'll have to use some sort of limit override.

Craig

Originally I had separate homing and limit switches. Still do, I have disabled the homing switches since I decided I wanted to home my system from the front left corner (where my limit switches are) instead of the middle of the table. My choice was really driven by how I used my machine. I'll probably pull the proximity switches and use them on my 9x20 lathe CNC conversion.

In my situation I don't see a need to have separate switches for limits and homing. Your mileage may vary.  I would rather use the I/O pins for other uses -- activating the dust system, multiple probes (touch off and laser tool measuring), etc.

-Freeman
 
I'm not a complete idiot...
    there are some parts missing.
Re: Help with some basic controls for homing
« Reply #5 on: March 28, 2018, 03:56:56 PM »
Agreed.  To Each his own.  I generally like having separate home and limit switches. 
We don't have to worry about I/O Constraints though.  We always use the HiCON here in the shop and I run a PLC on machines connected to Mach4 via TCP Modbus.   Virtually unlimited I/O.
I only have to have Probes, Limit/Home Swtiches, and E Stop hooked directly to the HiCON.

I didn't realize that you could use limit switches as home switches on the ESS; I know you can on the HiCON and it homes just fine but if you hit the switch out of the homing routine I've got to push the "Axis Limit Override" button to move it off the switch.
Chad Byrd
Re: Help with some basic controls for homing
« Reply #6 on: March 28, 2018, 04:21:06 PM »
Hi,
firstly, just because your home switches are somewhere in the middle of the table that does not prevent you from
placing your home point wherever you wish, thats what the 'Home Offset' setting is all about.

The ESS has 26 inputs without creative, and you need to economise???

Quote
In my situation I don't see a need to have separate switches for limits and homing.
Now you have the problem you describe....go to machine zero and your limit switches activate...as they are supposed to.
My wife left with my best friend...
     and I miss him!
Re: Help with some basic controls for homing
« Reply #7 on: March 28, 2018, 05:08:26 PM »
Now you have the problem you describe....go to machine zero and your limit switches activate...as they are supposed to.

Interesting, I don't ever remember trying to go to machine coordinates 0,0,0 other than when homing in the four years of owning the machine. On a 48"x48" (closer to 48"x46") table I typically drop my stock in the middle somewhere convenient for work holding and probe for work offsets.  I'll try moving to deliberately  to machine coordinates 0,0,0 tonight and see what happens. 

Your point on the number of I/O on the ESS is well taken. I just haven't bothered using more than I needed. It's even more pronounced when I have free I/O on the normal two ports that the ESS interfaces with the PMDX-126 with and there is a completely unused third port on the ESS I haven't touched yet.

-Freeman
« Last Edit: March 28, 2018, 05:17:23 PM by Analias »
I'm not a complete idiot...
    there are some parts missing.
Re: Help with some basic controls for homing
« Reply #8 on: March 28, 2018, 05:15:25 PM »
I'll try moving to deliberately moving to machine coordinates 0,0,0 tonight and see what happens. 

I just realized what will happen, nothing. My machine 0,0,0 is slightly off of the edges of the table. I have the homing settings adjusted to put the center of the spindle directly over the corner of the table surface. The coordinates where the limit switches activate are all negative. So in effect I have set my home position offset from the configured homing switches.

-Freeman
I'm not a complete idiot...
    there are some parts missing.
Re: Help with some basic controls for homing
« Reply #9 on: March 28, 2018, 07:41:38 PM »
Hi,
most industrial machines are wired so that if a limit switch is triggered ALL the power supply contactors drop out.
In many countries workplace safety legislation effectively mandates that should be the case. There is no avoiding
it, you can't bypass it or override it...by employment law.

As hobbyists however many of our machines combine home and limit switches which preclude the dedicated de-powering
of the spindle and axis motors as required in industrial practice and  require limit overrides and specifically ignoring limit switches
when homing, a situation which carries a significant risk of a run-away axis. Just when you need limit protection the most
we disable it!

Craig

My wife left with my best friend...
     and I miss him!