Need Help! Z Axis problem Grbl :-(


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Thread: Z Axis problem Grbl :-(

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    Default Z Axis problem Grbl :-(

    Hi,
    I'm having an issue with tool changes and zeroing the Z axis after first run.
    I'll lay it out point by point so that it's clear as to what Im trying to do, yet, unfortunately, cannot do :-(

    Firstly, I am using a 1000mm X 750mm Ox CNC Setup, with a dewalt router, with a Spark Concepts Controller board, the Xpro v2 and using Universal Gcode Sender for the communication.

    Basically I start with a project say 12" x 12" Wood.
    It requires 3 tools: End Mill, Ballnose and a V-Bit
    when I zero the machine at the bottom left corner of my work piece, all zeroing happens just fine, with all axis in UGS showing as zeroed.
    Then, I send it off on its first run to do the rough path with the End Mill. It does this perfectly, then returns to zero.
    At this point I need to switch out to a ballnose bit, which is a little longer than my roughing End mill. So, using UGS, I jog the machine slighlty away from my workpiece, and lift the router up about an inch, so as to get the bit out and put the longer bit in.
    Once the bits are switched, I reset the zero for the Z axis only (after bringing it back down to the appropriate height of course), then I send the command to return to zero.

    At this point, the router shoots straight up, at full speed, until it hits the limit of its upward travel, at that point I have to hit the kill switch. After this of course, my zero is gone, and I have to try and re-zero by eye, which although close, clearly shows faults in the finished work.
    It does this everytime without fail, and as a brand new CNC user at hobby level, I'm almost at the point of giving up trying to figure it out and selling my machine.

    I have scoured the internet far and wide, and have been wrestling with this for months, but I can't find anyone with the same problem, so if someone here has a clue as to what it may be, that would be most super awesome!

    Thanks for reading.


    Dom.

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    Default Re: Z Axis problem Grbl :-(

    :-/

    At the beginning of typing this thread, I said to myself, I must put this in the right place.

    I said that to myself about 5 times, and still ended up posting this in the wrong section, so, feel free to delete or move the post as any of you mods see fit :-)

    However, just on the offchance that my problem maybe Vectric related, I do use that, so..... :-)



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    Default Re: Z Axis problem Grbl :-(

    Quote Originally Posted by Gremlin76 View Post
    :-/

    At the beginning of typing this thread, I said to myself, I must put this in the right place.

    I said that to myself about 5 times, and still ended up posting this in the wrong section, so, feel free to delete or move the post as any of you mods see fit :-)

    However, just on the offchance that my problem maybe Vectric related, I do use that, so..... :-)
    The Vectric software is a very stable platform and it sounds more like a problem with the GCode. The first thing that I would do is to confirm that you are saving your code using the correct post processor. This option is available on your save tool path page.

    Of course you will notice that mine is set for Mach3 which is what I use.

    Attached Thumbnails Attached Thumbnails Z Axis problem Grbl :-(-post-processor-jpg  


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    Default Re: Z Axis problem Grbl :-(

    Quote Originally Posted by plcamp View Post
    The Vectric software is a very stable platform and it sounds more like a problem with the GCode. The first thing that I would do is to confirm that you are saving your code using the correct post processor. This option is available on your save tool path page.

    Of course you will notice that mine is set for Mach3 which is what I use.

    Hi,

    Thanks for your response.
    I am familiar with the whole Post Processor hoo haa :-) well, I know what they are anyway, but I think I'm using the correct one. And anyway, like I said, it zeros fine, and returns to zero fine, but as soon as I jog it in any way and then reset just the z, it will no longer return to zero, it just does what I described in my initial post.

    It's not just one particular jobanyway, it's any jobs that require a re-adjustment of the Z.
    For a while, I was using the Gcode mm (*.TAP) PP, as that was recommended by the supplier of my OX kit. But after speaking to the main guy at Spark Concepts, he recommended that I use the Grbl.8c (mm) PP.

    This made logical sense to me, since although the post processor is for a previous build version of Grbl, he said that basically the changes were mainly in the software, and not the gcode side, so that should work fine.

    I will repost this to the correct place, but if you read this response mate, I'd definetly appreciate any more insight you may have.


    Cheers,


    Dom.



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    Default Re: Z Axis problem Grbl :-(

    Quote Originally Posted by Gremlin76 View Post
    Hi,

    Thanks for your response.
    I am familiar with the whole Post Processor hoo haa :-) well, I know what they are anyway, but I think I'm using the correct one. And anyway, like I said, it zeros fine, and returns to zero fine, but as soon as I jog it in any way and then reset just the z, it will no longer return to zero, it just does what I described in my initial post.

    It's not just one particular jobanyway, it's any jobs that require a re-adjustment of the Z.
    For a while, I was using the Gcode mm (*.TAP) PP, as that was recommended by the supplier of my OX kit. But after speaking to the main guy at Spark Concepts, he recommended that I use the Grbl.8c (mm) PP.

    This made logical sense to me, since although the post processor is for a previous build version of Grbl, he said that basically the changes were mainly in the software, and not the gcode side, so that should work fine.

    I will repost this to the correct place, but if you read this response mate, I'd definetly appreciate any more insight you may have.


    Cheers,


    Dom.
    OK, I believe that the grbl post is correct and would have been my suggestion.

    What is your 'Safe Z' setting? Again our machine controls are different, but should act similar when performing certain operations. My machining procedure is the same as yours
    1. Set 0,0,0 at the appropriate reference point
    2. Run roughing cutter path

    At this point the machine returns to 0",0",1" the 1" which is the 'Safe Z' set during you tool path creation within the Vectric software.

    3. Change cutter, since the machine is already at 0,0,1 only 'Z' is touched off and set to 0.
    4. Load and run next cutter path.

    Before running your second program, view your code and confirm the 'Z' moves. You should see a 'Z' with the suffix H1 which is your predetermined 'Safe Z'

    Attached Thumbnails Attached Thumbnails Z Axis problem Grbl :-(-safe-z-setting-jpg   Z Axis problem Grbl :-(-safe-z-jpg   Z Axis problem Grbl :-(-code-jpg  


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    Default Re: Z Axis problem Grbl :-(

    Hi,

    The safe Z I tend to keep at 1.5mm at the moment. I realise it should perhaps be a bit higher, but for the time being, the projects I want to try will be fine with that safe z value, as I wont typically have any tool changes to do, not to mention, I have a range of bit lengths, and due to pure laziness, I have not yet worked out the numbers to put in for my safe z overall height :-/.

    The problem is, I can't change the bit at the zeroed coordinates, because even if I set the Safe Z much higher, unless I was working something as thin as 5mm I still would'nt have the space to get my bit in or out of the collet.



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    Default Re: Z Axis problem Grbl :-(

    Quote Originally Posted by Gremlin76 View Post
    Hi,

    The safe Z I tend to keep at 1.5mm at the moment. I realise it should perhaps be a bit higher, but for the time being, the projects I want to try will be fine with that safe z value, as I wont typically have any tool changes to do, not to mention, I have a range of bit lengths, and due to pure laziness, I have not yet worked out the numbers to put in for my safe z overall height :-/.

    The problem is, I can't change the bit at the zeroed coordinates, because even if I set the Safe Z much higher, unless I was working something as thin as 5mm I still would'nt have the space to get my bit in or out of the collet.
    I have my Safe Z set at 1" and never change it, this was just a convenient number to work with, 1.5mm is close, however if you are comfortable with it will work fine. Have your checked your code to look for the H1 callout? One other question, are you using a tool changer?



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Z Axis problem Grbl :-(

Z Axis problem Grbl :-(