Machsupport Forum
Mach Discussion => Mach4 General Discussion => Topic started by: sunny_x1 on December 18, 2017, 02:47:27 PM
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Hi
I have an issue with my cnc. Homing my z-Axis works fine until the switch will be activated. Then it runs into an Limit-Switch error. It seems, that Mach4/Pokeys doesn't retract the Z-Axis far enough to release the switch after homing. Is there a way to adjust the distance of the Z-Axis, that the switch will be released after homing? i don't know if it's an issue with Mach4 or Pokeys57cnc. All other axis working fine.
Thanks
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IIRC the axis is moved off of the switch until the switch has been seen to change states.
I would make sure that you have your limits and home configured properly.
Mike
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Well, that‘s why i‘m asking. I have no idea and i‘m searching for a way to change the distance the z axisis has to drive back after homing.
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Are you using the same switch for limit and home?
Mike
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Hi,
I have no idea and i‘m searching for a way to change the distance the z axisis has to drive back after homing
the axis backs off only as far as it takes for the switch to activate again. There is no control over how far it moves.
Craig
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The back off is dependent on the vendor's plugin implementation.
PMDX SmartBOBs will back off until the sensor clears, and then
another 0.050" so that vibrations will not trigger it in case it is also
used as a limit sensor that might false trigger due to vibration from
other axes moving.
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Hi,
you could write some code to cause it to back off and add the code to the <Ref All> script.
Mach4 is very flexible and this is exactly the sort of thing which is made possible by that flexibility.
Craig
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The plugin has the advantage that it can ignore false trips while doing
the back off. My guess is that the script could be interrupted by a
limit trip if the same switch was used for home and limit.
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Hi,
Steve is right if the home switch is triggering a limit event at the same time you can write code until the cows come home,
the limit event will stop Mach dead.
I personally prefer limit switches and home switches to be separate. This post is an example of why. You wish Mach to treat this
switch as a home switch at the moment and therefore to ignore it as a limit switch. The fault you describe is that Mach IS treating
it as a limit switch. If you had separate home and limit switches the problem wouldn't arise. Additionally it allows you to use
good quality microswitches for home switches, for which they are ideally suited, and proximity switches as limits, again an
ideal application for them. A proximity switch is a poor choice as a home switch, it is not sufficently repeatable.
Is there a particular reason that you have combined the limit and home functions?
Craig
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Thank you for your post. i‘m really new to cnc. 3 month ago i had no idea what it is and how it works. Now, 3 month later i build one. It sounds reasonable to me, that during a homing process a limit switch can simply be handled as a home switch. I‘had no idea, that there could be a problem. It works for all axis but not at my z. My z pulls back a bit and stops, without releasing the switch. I ordered some inductive switches last week but for now im interested in solving this problem as it is. Any idea how to handle this inerruption. Can i do something in my Pokeys57cnc?
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Hi,
no I don't think so. Snap action microswitches are correct for home switches and proximity switches for limit switches. The simplest way to solve your problem is to have
three individual home switches, one for each axis and ideally each with its own input pin and separate limit switches. Note that all your home switches need
to be 'inside' your limits. Then you can reference (home) your machine without any of the limit switches triggering. With your motion controller a 57CNC
you have swags of IO, why are you trying to economise on inputs? Faults like the one you have described are exactly the sort of thing that occurs when you try
to do double duty with your switches.
Craig
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IMHO i cannot see a problem with proximity switches as home switches and limit, i have used these on my machine for 4 years as the same and will do on my new machine shortly, they are very accurate.
DazTheGas
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I got a tip to solve this by adjusting the “Debounce interval” and “Index debounce” settings. unfortunately in mach3. I could not found this function in mach4. Does it exist in mach4?
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Hi,
those are settings in your motion controller plugin not Mach.
Craig
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OK. Thanks Craig. I will have a closer look to the board doc.