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IndustryArena Forum > Machine Controllers Software and Solutions > PlanetCNC > howto work with multiple work offsets G54 G55 ....
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  1. #1
    Join Date
    Aug 2020
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    131

    howto work with multiple work offsets G54 G55 ....

    I'm currently looking into working with different Work Offsets and I have a bit of a hard time understanding the differente and relations between Work Position and Coordinate System.
    I'm more or less sure that the confusion mainly is caused by me being an absolute novice in machining, so if someone could shed some light into this it would be greatly appreciated.


    I have two vices installed on my machine and I want to machine the same part in both of them to reduce tool change time. From my understanding I can achieve this by running the same gcode in different coordinate systems and switching between them on the fly. Machine Part 1 with tool 1 in G54, and repeated the same code a second time with G55.
    In general this seems to be working as expected, however I'm struggling with setting the Origin for G54 and G55 correctly.
    From a hierarchy point of view I always thought that I would have the Machine Coordinate Systems on top, followed by the G54/G55 Coordinate System. But it seems that with Planet CNC there is a third Work Position in between the two.
    When using the default buttons for "Work Position XY/Z" To zero it shifts not only the currently G5* but ALL of them.
    I figured that I need to use the Buttons
    Machine->Coordinate Systems->Axis To Zero..... to set the Origin for each G5* individually.
    Beside this I figured that switching in Settings->User Interface->Position->Command from Work Position to Coordinate System would change the behavior of the XYZ Buttons in the user Interface to change only the current active G5*

    So while ignoring the Menü buttons on the left menu and working with "Machine->Coordinate Systems->....." buttons seems to give me the desired result I don't really understand the benefit of the "Work Position" Coordinate system in between and I'm not sure if I'm going with the correct approach or if I do something fundamentally wrong.

    best Regards,
    Klaus

  2. #2
    Join Date
    Mar 2017
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    1295

    Re: howto work with multiple work offsets G54 G55 ....

    Text below

    On this image CS sets distance between blue and green, WO sets distance between green and orange.
    Attached Thumbnails Attached Thumbnails IMG_20210216_114900[1].jpg  

  3. #3
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    Mar 2017
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    Re: howto work with multiple work offsets G54 G55 ....

    There are two important positions on CNC.


    1. Machine position - this is physical position of tool of your machine.
    This position is set during hoiming procedure where machine limits are detected.
    2. Work position - this is ad hoc position. It is set as needed to ease working with machine.


    CNC move commands almost always use work position (exception is G53).
    Because physical machine moves are in machine position. algorithm to calculate machine position from work position is needed.


    These are our options (I call them offsets):
    1. Axis offset, rotation and scale (AO)
    2. Tool offset (TO)
    3. Work offset (WO)
    4. Coordinate system offset and rotation (CS)
    5. Warp
    6. Transformation


    Formula for algorithm is:
    Machine position + AO + TO + WO + CS + Warp + Transformation = Work position


    As you see there are a lot of different ways to get same results.


    Which offset you use depends on your workflow because each offset has its own perks.
    In "multiple vices" case I would use CS offset for each vice.
    Within each vice I would use WO.


    In old days there was only one offset and perhaps it was easier to understand.
    But this gives much more flexibility.

  4. #4
    Join Date
    Aug 2020
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    131

    Re: howto work with multiple work offsets G54 G55 ....

    OK this matches more or less what I figured.

    The point that confuses me is that changing the Work offset while being in G54 has a influence on G55
    I had expected that the WO would be a "subset" of CS, not the other way around.
    As far as I can see from the reactions of the Programm CS seems to be set in relation to WO

  5. #5
    Join Date
    Mar 2017
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    1295

    Re: howto work with multiple work offsets G54 G55 ....

    WO and CS are independent.

    Lets say machine position X=10 and all offsets are zero. Work position is X=10.
    Set CS to X=6. Work position is X=4.
    Set WO to X=3. Work position is X=1.
    Set CS again to X=1. Work position is X=6.

    G54, G55... just select which coordinate system offset you you use. Work offset remains the same.
    This is logical. You select coordinate system for each vice. With G54, G55,... you select which vice you will be using.
    Now put some material in all your vices. You only need to select "working zero" on one vice and will remain same for all other.

  6. #6
    Join Date
    Aug 2020
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    131

    Re: howto work with multiple work offsets G54 G55 ....

    Thanks for the explanation. I think I finally understand the logic behind this. It does not match by initial Assumtion on how this stuff would work but I think I can adapt to this ;-)

  7. #7
    Join Date
    Jan 2005
    Posts
    15362

    Re: howto work with multiple work offsets G54 G55 ....

    Quote Originally Posted by ScorpionTDL View Post
    I'm currently looking into working with different Work Offsets and I have a bit of a hard time understanding the differente and relations between Work Position and Coordinate System.
    I'm more or less sure that the confusion mainly is caused by me being an absolute novice in machining, so if someone could shed some light into this it would be greatly appreciated.


    I have two vices installed on my machine and I want to machine the same part in both of them to reduce tool change time. From my understanding I can achieve this by running the same gcode in different coordinate systems and switching between them on the fly. Machine Part 1 with tool 1 in G54, and repeated the same code a second time with G55.
    In general this seems to be working as expected, however I'm struggling with setting the Origin for G54 and G55 correctly.
    From a hierarchy point of view I always thought that I would have the Machine Coordinate Systems on top, followed by the G54/G55 Coordinate System. But it seems that with Planet CNC there is a third Work Position in between the two.
    When using the default buttons for "Work Position XY/Z" To zero it shifts not only the currently G5* but ALL of them.
    I figured that I need to use the Buttons
    Machine->Coordinate Systems->Axis To Zero..... to set the Origin for each G5* individually.
    Beside this I figured that switching in Settings->User Interface->Position->Command from Work Position to Coordinate System would change the behavior of the XYZ Buttons in the user Interface to change only the current active G5*

    So while ignoring the Menü buttons on the left menu and working with "Machine->Coordinate Systems->....." buttons seems to give me the desired result I don't really understand the benefit of the "Work Position" Coordinate system in between and I'm not sure if I'm going with the correct approach or if I do something fundamentally wrong.

    best Regards,
    Klaus
    This can be very simple in your programing with just having an X----- Y------ move to the next Vice start position still using the same work offset
    Mactec54

  8. #8
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    Aug 2020
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    131

    Re: howto work with multiple work offsets G54 G55 ....

    After spending a good one or two hours on the phone with Daniel (tantemay) I have to say that the current implementation of the WorkOffsets and Coordinate Systems in PlanetCNC is quiet confusing and prone to error.

    My main problem is the so called "Work Position" (menu Path "Machine/Work Position") I attached the Picture to better show our current understanding of the dependencies between Machine, Work and Coordinate System position (I know transformation and warp is missing in this picture).

    In our usecase we would like to set the origin for G54 G55 etc..... independently from each other. When setting something for G55 it should change nothing on G54 and vice versa. This works fine when we strictly work with the options available in "Machine/Coordinate System"
    However as soon as we accidently use something that changes the Work Position we screw up all other Coordinate Systems.
    For me there are several issues with the current implementation:
    - G92 sets the "Work Position" but at the same time touches all the coordinate Systems
    - the "Work Position" is effektive invisible to the user, we only see the Effekt of it but never the actual values.
    - There seems to be some naming conflict with "Work". The Tab for the Work coordinates is called Work. In the Menu we have "Machine/Work Position" for us this lead to the Assumtion that those are one and the same. However Work is a combination of "Work Position" and "Coordinate Systems"
    - The real big issue is that all the set XYZ to Zero buttons act on the "Work Position" by default. In the Work Tab its possible to change this to act on the Coordinate System (Settings/User Interface/Position/Commands/Work/Coordinate System) but this does not change the behavior of the Buttons on the Handwheel for example. We would need to have the same option for the Handwheel


    At this point in time we decided that the safest approach would be to set the "Work Position" Zero to the Machine Zero and never touch this again. Switching all the Scripts for "Work Position" to the ones from "Coordinate Systems"

  9. #9
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    Mar 2017
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    1295

    Re: howto work with multiple work offsets G54 G55 ....

    There are no issues in implementation. You just want to use these offsets differently.

    If you don't want to use work offset (G92) then don't use it. After all, why would you use old school G92 work offset if modern coordinate system offset is available. But if you do, I described, how they work together and what is logic behind it. LinuxCNC and Mach does this same way. Mach calls this fixture thou.

    Simply don't use menu commands under "Machine/Work Position" and in settings "UI/Position/Commands" set "Work" button to be "Coordinate System". I'm aware of users like you and that is why I made this configurable.
    I will make sure that this is also works for pendant and if I missed it anywhere else let me know.

    But then again, old school G92 work offset is simple and what 95% of people use. You don't need to know anything about offsets. You just use "work position to zero" command and you are done.

  10. #10
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    Aug 2020
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    131

    Re: howto work with multiple work offsets G54 G55 ....

    I agree that the implementation itself is working correctly from a technical point of view. However it makes it quiet easy to set something unintended.

    So the decision from moving away from G92 altogether is the correct approach in this usecase. The main issue is that most of the Buttons are hardcoded to G92 and it requieres some rework of the GUI buttons, no big deal but its a bit more complex than "stay away from the menu commands under "Machine/Work Position"" ;-)
    Its totally manageable, but to be honest I was not sure it this was the design intent.

    If we can get a similar option like "UI/Position/Commands" for the wireless Handwheel (or if the options affects the handweel buttons as well) this would help a lot.
    At this point in time I think the only way to change the behavior of the Handwheel is by changing the script for the Workoffset and I don't realy like this as the behavior of the scripts would no longer match the naming.

    In general I agree that G92 works fine for most of the cases. Up to now that was all I ever used. However I had one workpiece that I wanted to machine two times at the same time in different locations and I thought it would be a good learning experience to try to get it working with G54 and G55. As you can probably tell from my writing it took me some time to figure everything out and I'm not 100% sure if I could explain it in easy word to someone new to the topic (that's normal my test to verify if I unterstand something correctly) but I think I'm getting there.

    best Regards,
    Klaus

  11. #11
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    1295

    Re: howto work with multiple work offsets G54 G55 ....

    I'm already working on handwheel issue. And let me know, if any other command should obey this "Work Position/Coordinate System" button setting.

  12. #12
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    131

    Re: howto work with multiple work offsets G54 G55 ....

    That's great, Thanks a lot.

    On the GUI Side it might be worth a thought to switch the default buttons on the left button menu for zeroing and height measurement over to Cordinate System as well. They are fixed to Work Position, while named correctly it might lead to confusion.
    Personally I don't use them as I have build my own GUI layout, so its no problem for me to switch them over. However for someone using the default buttons it would probable be nice to have the possibility to switch them over to Coordinate System as well.

  13. #13
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    Re: howto work with multiple work offsets G54 G55 ....

    Those buttons already behave as Work/Coordinate button setting dictates.

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