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Thread: CONFUSED... Where to home too... Help! where should my home switches be.

  1. #25
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    Default Re: CONFUSED... Where to home too... Help! where should my home switches be.

    Quote Originally Posted by 109jb View Post
    G28 is not an "incremental" move and can be used in G90 absolute mode or in G91 incremental mode. Yes G91 is used most often, because it is easier, but G28 works in absolute mode as well.

    G28 G91 X0 Y0 Z0 moves from where it is now in a straight line to the predefined position. Nothing incremental about that

    G28 G91 X0 Y0 Z1 moves the Z up one unit and then it goes straight to the predefined position

    I disagree that G53 is used more or is in any way better because to use it you have to set the machine coordinates that a G53 is going to. Use a different machine and the coordinates will likely need to be different Whereas with a G28, the coordinates are set at the machine and the program doesn't need to be modified. A CAM program can put a G28 G91 X0 Y0 Z1 but it can't put in a G53 unless it knows the coordinates it is sending to

    To make that same move in G53 you need

    G91 G0 Z1
    G53 G0 X??? Y???? Z???? where the ??? are the coordinates of the G28 position.


    G30 is just another predefined position and works just like G28.
    Yes correct with the G28 it is normally used with a G91 I missed that bit

    G30 does work like G28 G30 is return to 2nd 3rd &4th reference points a G28 does not do this and has very little use unless you have pallets or fixtures to move into different preset positions in the control other than normal Zero Positions

    Here is some good information on these codes and how they work

    https://www.cncci.com/resources/tips...28%20works.htm

    Last edited by mactec54; 05-15-2019 at 07:51 PM. Reason: Added link
    Mactec54


  2. #26
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    Default Re: CONFUSED... Where to home too... Help! where should my home switches be.

    Quote Originally Posted by truckeic View Post
    So using G53 do you have to use z y and X.
    Why not use z X y without the g53

    Sent from my XT1635-01 using Tapatalk
    Are yes good question you never use all 3 Axes moves at the same time you always want to first move the Z axes up like G53G0Z0. or where ever you want to move it to, this will make sure your tool is clear of your work before X and Y axes move

    End of Program

    G53G0Z----.
    G53X----Y----
    M5
    M30
    %

    Mactec54


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    Default Re: CONFUSED... Where to home too... Help! where should my home switches be.

    Quote Originally Posted by mactec54 View Post
    Are yes good question you never use all 3 Axes moves at the same time you always want to first move the Z axes up like G53G0Z0. or where ever you want to move it to, this will make sure your tool is clear of your work before X and Y axes move

    End of Program

    G53G0Z----.
    G53X----Y----
    M5
    M30
    %

    Small nitpicking point here but for 3D surfacing I have often moved all 3 axes at the same time and when I was running a 5 axis machine all 5 moved simultaneously when required.I readily admit that those sort of machines and the software to generate the toolpaths are well outside the scope of hobbyists-at least for now.The real benefit of a good homing routine is that the machine will go back to the same location the next day or the next year and perform the same operations.My hobby machine doesn't yet have that level of sophistication so I have to remember to move the axes to the point I nominated as a home position when I powered up.I get away with it but I don't make aerospace parts at home and don't have to satisfy any inspection but my own.



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    Default Re: CONFUSED... Where to home too... Help! where should my home switches be.

    He was referring to not usually using all 3 axes with a g53 or g28. This is because when using these commands you are usually moving the machine to a "clear" location and will want to move just the z axis first and then x y.

    Using 3 axes simultaneously is very doable even for a hobbyist. Fusion 360 allows full 3d contouring and is free for hobbyist and start up businesses.



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    Default Re: CONFUSED... Where to home too... Help! where should my home switches be.

    Quote Originally Posted by routalot View Post
    Small nitpicking point here but for 3D surfacing I have often moved all 3 axes at the same time and when I was running a 5 axis machine all 5 moved simultaneously when required.I readily admit that those sort of machines and the software to generate the toolpaths are well outside the scope of hobbyists-at least for now.The real benefit of a good homing routine is that the machine will go back to the same location the next day or the next year and perform the same operations.My hobby machine doesn't yet have that level of sophistication so I have to remember to move the axes to the point I nominated as a home position when I powered up.I get away with it but I don't make aerospace parts at home and don't have to satisfy any inspection but my own.
    That not nitpicking it just not normal practice, 3D surfacing and 5axes programing is not a regular 3 Axes machine movement, 3D machining and 5 axes are programed moves with Gouge protection a regular 3 axes move at the end of a program is a crash waiting to happen

    Mactec54


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    Default Re: CONFUSED... Where to home too... Help! where should my home switches be.

    Quote Originally Posted by Jim Dawson View Post
    Here is the normal layout for mill axes, home position can be anywhere that you want it.

    CONFUSED... Where to home too... Help! where should my home switches be.-mill-axis-jpg

    Unless your home switches are very accurate, it is better just to zero off of the part that you are working on. There is really no need for a home position unless you have a tool changer. I don't have home switches on my mill, but I do have the ability to set a floating ''parking position'' to move the Z and table to a convenient location for tool and part changes that is invoked on a tool change command or program end. This is set per the job on the table.
    I just want to make sure of this....
    So if I am facing my Mill and the Table is JOGGED to the right (moving in the right direction) the DRO should be going positive correct? and if the Table is jogged to the LEFT that would show negative direction on DRO correct.
    Jogging Y away from me should give me positive movement on DRO and Y close to me would be Negative correct?

    I want to make sure my Motors are turning the correct directions and homing in the correct directions.

    Thanks for all the help!!



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    Default

    Quote Originally Posted by truckeic View Post
    I just want to make sure of this....
    So if I am facing my Mill and the Table is JOGGED to the right (moving in the right direction) the DRO should be going positive correct? and if the Table is jogged to the LEFT that would show negative direction on DRO correct.
    Jogging Y away from me should give me positive movement on DRO and Y close to me would be Negative correct?

    I want to make sure my Motors are turning the correct directions and homing in the correct directions.

    Thanks for all the help!!

    Do the following with a felt tip marker:
    -stand in front of the machine, facing it, as the user.
    - in the physical center of the table make a dot
    - the dot is home.
    - draw a line through the dot in the left/right direction, from one end to the other end of the table.
    - on the right most end of the line, ON THE TABLE, write +X
    - on the leftmost end write -X
    - draw another line through the dot, perpendicular to the first line.
    Furthest from you, at the end of the line write +Y
    Closest to you write -Y.



  8. #32
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    Default Re: CONFUSED... Where to home too... Help! where should my home switches be.

    Quote Originally Posted by truckeic View Post
    I just want to make sure of this....
    So if I am facing my Mill and the Table is JOGGED to the right (moving in the right direction) the DRO should be going positive correct? and if the Table is jogged to the LEFT that would show negative direction on DRO correct.
    Jogging Y away from me should give me positive movement on DRO and Y close to me would be Negative correct?

    I want to make sure my Motors are turning the correct directions and homing in the correct directions.

    Thanks for all the help!!
    You have to look at it from the perspective of the tool bit (looking down).

    Table moving Right = DRO X going Negative
    Table moving Left = DRO X going Positive
    Table moving Towards the Column = DRO Y going Negative
    Table moving Away From the Column = DRO Y going Positive
    Tool Moving Closer to the work (down) = DRO Z going Negative
    Tool Moving Away from the work (up) = DRO Z going Positive

    https://en.wikipedia.org/wiki/Cartes...rdinate_system see the image at the top right on the page.

    The coordinates shown are what your DRO should read when the tool bit in the position of the dot.

    Last edited by Jim Dawson; 05-16-2019 at 11:13 AM.
    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: CONFUSED... Where to home too... Help! where should my home switches be.

    think of the Tool in the Spindle as a Pencil you write with...You are moving the Pencil ....not the Paper.
    Cartesian Right-Hand Rule - CNCexpo.com



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    Default Re: CONFUSED... Where to home too... Help! where should my home switches be.

    Quote Originally Posted by Jim Dawson View Post
    You have to look at it from the perspective of the tool bit (looking down).

    Table moving Right = DRO X going Negative
    Table moving Left = DRO X going Positive
    Table moving Towards the Column = DRO Y going Negative
    Table moving Away From the Column = DRO Y going Positive
    Tool Moving Closer to the work (down) = DRO Z going Negative
    Tool Moving Away from the work (up) = DRO Z going Positive

    https://en.wikipedia.org/wiki/Cartes...rdinate_system see the image at the top right on the page.

    The coordinates shown are what your DRO should read when the tool bit in the position of the dot.
    That is what I thought...
    It from the prospective of the tool looking down. I have several folks telling me otherwise.

    So if the x direction were to home to Neg X then it would have to move to the right and if Y were to home in the negative direction then it would home to the front (away from the column) that would put my home

    Neg X=0 Neg y=0 and i know Z is positive at the top.

    Thanks!!



  11. #35
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    Default Re: CONFUSED... Where to home too... Help! where should my home switches be.

    Just to add some confusion here, one should not confuse a home position with a ''parking'' position. Normally a home position is where the Machine Coordinate System (MCS) is set to 0,0,0. The parking position could be an offset from the home position.

    On the Haas, the home position is a fixed location set by limit switches and servo encoder index. The Work Coordinate System (WCS, G54-59) is set as an offset from the MCS (G53) and is set to the work. The parking position is an offset from the WCS, I think (I don't run the Haas). To park the Haas we normally move the table to the center, and to the front of the machine, Z is sent to the top. I don't know if this is done with a G28 or just a G0 move.

    On my knee mill, 0,0,0 (WCS=MCS) is always set to the work, there is no fixed home position. The parking position is set per the job by moving the table and Z to a convenient location and clicking on ''set park position'', I think this is equivalent to a G28 move, but I have never used a G28.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: CONFUSED... Where to home too... Help! where should my home switches be.

    I put them on because it cost me $20 and I don’t need to brainsweat as much. My inductive switches made 1/2 a thou as well. More like .0003.



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CONFUSED... Where to home too... Help! where should my home switches be.

CONFUSED... Where to home too... Help! where should my home switches be.