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Thread: Advice on going home at end of program

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    Default Advice on going home at end of program

    My issue is that X,Y and Z all move at the same time.

    I typically end my programs like this:

    G0 Z20.0 (mm example)
    G49
    G91 G28 Z0.
    G28 X0 .Y0.
    M2

    With commercial machines I have use in the past this works fine.

    With KMotionCNC I have had to place G91 on its own line but why are X and Y moving before Z gets to home position?

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    Default Re: Advice on going home at end of program

    Hi eng101,

    That is the way it is coded.

    The Interpreter moves to the specified intermediate position (either incremental or absolute) then the XYZ Axes move to the home position.

    So G91 G28 Z0 indicates an incremental move of 0 and then the XYZ Axes move to the home position.

    To move Z to absolute 0 first code G90 G28 Z0

    Regards

    TK
    http://dynomotion.com


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    Default Re: Advice on going home at end of program

    Hello Tom

    G90 G28 Z0 just sends the Z Axis to the machine table.Not the direction I wanted.

    I just have to make a sufficient clearance move before using G91 G28 Z0.



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    Default Re: Advice on going home at end of program

    Hi eng101,

    Oops, if your coordinate system has 0 set at the table surface that would occur.

    G0 G53 Z0

    should move Z up assuming Machine 0 is fully up on your system.

    Regards

    TK
    http://dynomotion.com


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    Default Re: Advice on going home at end of program

    That's the way it seems to be coded. Some software, like UCCNC, allows you to set in which order the axes are homed, some don't allow that or don't have that feature implemented. Homing all at the same time never really works, so I don't know how those people were thinking, the way UCCNC handles this is very logical and useful. Of course, "home" should not be zero coordinate position because that can never really be OK as home, especially not for Z.

    https://adapting-camera.blogspot.com
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    Default Re: Advice on going home at end of program

    Quote Originally Posted by TomKerekes View Post
    Hi eng101,

    Oops, if your coordinate system has 0 set at the table surface that would occur.

    G0 G53 Z0

    should move Z up assuming Machine 0 is fully up on your system.

    Regards
    Hello Tom,
    Could you explain the coordinate system and how to change it
    Also how to define axis stroke limit (soft limit).
    I tried to set soft limit on -Z. but it just went passed where it it should have stopped.
    I could install another limit SW but I was trying not to add more wiring.
    Thanks in advance for your help.



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    Gold Member TomKerekes's Avatar
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    Default Re: Advice on going home at end of program

    Hi eng101,

    Offsets (Axis, Origin, and Tool) can change the GCode origin.

    Soft Limits are set in raw machine coordinates and are set in motor steps or counts. Do you know where your machine origin is? What did you set the Soft Limit Settings to?

    Regards

    TK
    http://dynomotion.com


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    Default Re: Advice on going home at end of program

    Sorry for the confusion.

    How is the the machine Table surface (zero) defined?

    My machine (router) is set for home position at X-axis to the left, Y-axis to the Front (towards operator), Z-axis up.

    I have figured out the Soft Limits for Z=-103200 this is gives me 250.00mm of travel Plus 0.5mm to Soft Limit.



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    Gold Member TomKerekes's Avatar
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    Default Re: Advice on going home at end of program

    Hi eng101,

    How and at what point are you setting the soft limits? It usually doesn't make sense to set them before homing.

    Are you then able to keep moving beyond Z = -103200 ? What shows on the Axis Screen?

    Regards

    TK
    http://dynomotion.com


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    Default

    Quote Originally Posted by TomKerekes View Post
    Hi eng101,

    How and at what point are you setting the soft limits? It usually doesn't make sense to set them before homing.

    Are you then able to keep moving beyond Z = -103200 ? What shows on the Axis Screen?




    Regards
    Hello Tom.
    The Soft Limits are set in the initiation program, then I run the home program. The home program disables, enables and zeros the DRO for all axies.
    Yes, the Z-Axis does not move if the programmed path is greater than the Soft Limit value.

    Is this a correct method?



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    Default Re: Advice on going home at end of program

    Hi eng101,

    So I It seems everything is working.

    Normally it doesn't make sense to set soft limits until after homing. But because you home positive and don't set a positive limit it works out ok.

    Regards

    TK
    http://dynomotion.com


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Advice on going home at end of program
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