Newbie Z Axis Probe Not Accurate


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  1. #1
    Member ScottBob's Avatar
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    Default Z Axis Probe Not Accurate

    I have a China CNC Zone USB 6040 machine running with Mach 3. My Z probe works, but it is not accurate and has a very different reading each time. With the same piece of wood, I set the probe on top, hit the button to find Z, the machine touched the probe and went back to home position. Then, I took the probe away and jogged the bit down the the surface of the board. I did this 5 times, and instead of the top of the board being 0, it was .0460, .00535, .0241, .0517, and .1109. I could not get it to ever replicate a number for Z. If it was off the same number each time, I could just adjust my offset, but it is super random. My machine is set up in inches. The XML file that came with machine looks like it is in MM's. I am wondering if the motor is missing steps because of the file? I can run the machine finding Z with a piece of paper and it seems to cut fine. So, I don't think my motors are way out of tune. Plus, the Z was out of tune, would it not at least be off the same number each time?

    Here is the XML code I am using. I tried a few others that other people have posted, and I could not get them to work at all. With the USB drive, I think I am unusual. This one "almost" works. Could anyone look at this code and tell me if I can change it to inches and if this could be my problem?

    Thank you so much in advance.

    Scott




    FeedCurrent = GetOemDRO(818) 'Get the current settings, OEM DROs (818)=Feedrate DRO
    ZCurrent = GetOemDro(802) 'OEM DROs (802)=Z DRO
    GageH = GetOEMDRO(1001) 'OEMDRO(1001)=Gage Block Height
    ZNew = ZCurrent - 300 'probe down 20 mm

    Code "G90F20" 'slow feed rate
    Rem Code "G4 P1" 'Pause 1 second to give time to position probe plate
    Code "G31 Z" &ZNew
    While IsMoving()
    Sleep(10)
    Wend
    Call SetDro (2,GageH) 'DRO(2)=Z DRO

    FinalMove = GageH + 4
    Code "G0 Z" &FinalMove
    Code "F" &FeedCurrent 'restore starting feed rate dr.lin 2009.10.16

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  2. #2
    Member ZASto's Avatar
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    Cool Re: Z Axis Probe Not Accurate

    You can associate the following code to your Z0 button
    Code:
    Sub Main() 'made it a sub, so you can return on "show stopper" errors
    'Option Explicit 'Written by Big-Tex Dec 26 2010 Updated Jun 3 2014
    'Mod pb 11dec10
    
    Dim ZNew, Zplate, Zrestposition, ZMaterialmachcoord, ZPlatejobcoord, Zplatetomaterial
    Dim xjobcoord, yjobcoord, xmachcoord, ymachcoord, zmachcoord
    Dim xprobeloc, yprobeloc, xtoprobe, ytoprobe, PlateOffset
    Dim CurrentFeed, Zretract
    Dim CurrentAbsInc
    
    xjobcoord = GetDRO(0) 'get current job coordinate for X
    yjobcoord = GetDRO(1) 'get current job coordinate for Y
    xmachcoord = GetOemDRO(83) 'get current machine coordinate for X
    ymachcoord = GetOemDRO(84) 'get current machine coordinate for Y
    zmachcoord = GetOemDRO(85) 'get current machine coordinate for Z
    xprobeloc = GetUserDRO(1100) 'get X machine coordinate location of the touch plate
    yprobeloc = GetUserDRO(1101) 'get Y machine coordinate location of the touch plate
    xtoprobe = (xprobeloc - xmachcoord + xjobcoord) 'calculate the X move from the current location to the touch plate
    ytoprobe = (yprobeloc - ymachcoord + yjobcoord) 'calculate the Y move from the current location to the touch plate
    PlateOffset = GetUserDRO(1151) 'get plate offset DRO
    CurrentFeed = GetOemDRO(818) 'get the current feedrate to return to later
    Zretract = GetOemDRO(1202) 'get Z tool change location
    CurrentAbsInc = GetOemLED(48) 'Get the current G90/G91 state
    
    '//////// the block below will set all your reusable vars depending on Inch or mm.
    '//////// this sets the vars so you only need ONE large block of probing code.
    
    If GetOEMLED(801) Then 'ON = English Measure INCH
    FirstProbeDist = 6.0 'first probe travel
    FirstRetractDist = 0.1 'first probe retract travel
    SecProbeDist = 0.25 'second probe travel
    FirstProbeFeed = 10 'First Probe Feed Speed
    SecondProbeFeed = 2 'Second Probe Feed Speed
    Else 'OFF = Metric Measure MM
    FirstProbeDist = 150.0 'first probe travel
    FirstRetractDist = 3.0 'first probe retract travel
    SecProbeDist = 6.0 'second probe travel
    FirstProbeFeed = 300 'First Probe Feed Speed
    SecondProbeFeed = 50 'Second Probe Feed Speed
    End If
    
    '//////// Error Condition checking code
    
    If GetOemLED(16)<>0 Then 'Checks for machine coordinates
    Code "(Please change to working coordinates)"
    Exit Sub 'ERROR! exit the macro
    End If
    
    If GetOemLED(825)<>0 Then
    Code "(Z-Plate Grounded Check connection and try again)"
    Exit Sub 'ERROR! exit the macro
    End If
    
    '//////// Start Probing Code, Probe In -Z direction.MOVABLE PROBE PLATE
    '//////// The vars will be Inch or Metric from above if/else statment
    
    sleep(1000) 'pause 1 seconds to give time to position probe plate
    Code "F" & FirstProbeFeed 'slow down feedrate to 10 ipm
    ZNew = ( GetDro(2) - FirstProbeDist ) 'probe move to current z - 6 inches
    Code "G90 G31Z" & ZNew
    While IsMoving() 'wait for probe move to finish
    Wend
    ZNew = GetVar(2002) 'read the touch point
    Code "G0 Z" & ( ZNew + FirstRetractDist ) 'move back to hit point incase there was overshoot +.1
    While IsMoving ()
    Wend
    Code "F" & SecondProbeFeed 'slow down feedrate to 2 ipm
    ZNew = ( GetDro(2) - SecProbeDist ) 'probe move to current z - .25 inches
    Code "G90 G31Z" & ZNew
    While IsMoving() 'wait for probe move to finish
    Wend
    ZNew = GetVar(2002) 'read the touch point
    Code "G0 Z" & ZNew 'move back to hit point incase there was overshoot
    While IsMoving ()
    Wend
    Call SetDro (2, PlateOffset) 'set the Z axis DRO to plate thickness
    sleep(250) 'pause for Dro to update.
    Code "G53 G0 Z" & Zretract
    While IsMoving ()
    Wend
    Code "F" & CurrentFeed 'returns to prior feed rate
    
    '//////// End Probing Code,
    
    If GetOEMLED(801) Then 'ON = English Measure INCH
    Code "(Z axis is now zeroed in English Units)" 'puts this message in the status bar
    Else 'OFF = Metric Measure MM
    Code "(Z axis is now zeroed in Metric Units)" 'puts this message in the status bar
    End If
    
    If CurrentAbsInc = 0 Then 'if G91 was in effect before then return to it
    Code "G91"
    End If
    
    End Sub


    Make no mistake between my personality and my attitude.
    My personality is who I am. My attitude depends on who you are.


  3. #3
    Member ScottBob's Avatar
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    Default Re: Z Axis Probe Not Accurate

    Thank you for the code. I tried it and it said syntax error.

    I sure wish someone could look at the code I use and see if they can see what my problem is.

    Thanks again,

    Scott



  4. #4
    Member ZASto's Avatar
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    Default Re: Z Axis Probe Not Accurate

    Code works perfectly on 3.43.062 version of Mach3. (code is from Big-Tex Tool Setter screenset.

    Make no mistake between my personality and my attitude.
    My personality is who I am. My attitude depends on who you are.


  5. #5
    Member ScottBob's Avatar
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    Default Re: Z Axis Probe Not Accurate

    3.43.062 version of Mach3 is what I am using too....



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    Default Re: Z Axis Probe Not Accurate

    Ok, if something went wrong during your Copy/Paste, here is the script as text file.

    Attached Files Attached Files
    Make no mistake between my personality and my attitude.
    My personality is who I am. My attitude depends on who you are.


  7. #7
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    Default Re: Z Axis Probe Not Accurate

    Thanks! I will try it.



  8. #8
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    Default Re: Z Axis Probe Not Accurate

    Well, that was what the problem was with the syntax error. I copied it on my Mac and sent it to my Windows laptop. I bet a character got changed or something. Now, it does move very slowly and hit the probe. But then, it goes all the way up to the top of my gantry and sets the zero there instead of at the top of the material. Any idea how to fix this? I feel like I am getting closer now, but I am still using a piece of paper to get my Z.

    Thank you again for all your help.

    Scott



  9. #9
    Member ScottBob's Avatar
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    Default Re: Z Axis Probe Not Accurate

    Any idea what is wrong? I wonder if I could set my offset to a negative number or something?



  10. #10
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    Default Re: Z Axis Probe Not Accurate

    Quote Originally Posted by ScottBob View Post
    Any idea what is wrong? I wonder if I could set my offset to a negative number or something?
    Probably. Did you try that?


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