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  1. #1
    Hi all,

    I知 very new to the world of CNC. I致e just built a CNC kit which I bought from ebay. It appears to be working (moving via the 'Grbl Controller' software) though, I have a key question. Hope this is not to daft and too funny, for you advanced users.
    Here goes, I知 having trouble understanding the Z-axis and how this is initially set up when starting a new job. My worry is that the spindle will go straight through the circuit board I知 about to mill, breaking the drill the bit and damaging the board itself, and I guess not doing the CNC any good!? So, how to I prep the machine to deal with these possible situations?

    Many thanks.

  2. #2
    Rye's Avatar
    Lives in Sheffield, United Kingdom. Last Activity: 01-09-2017 Has been a member for 1-2 years. Has a total post count of 35. Received thanks 3 times, giving thanks to others 0 times.
    Not used the Grbl software. I use an smc4-4-16a16b controller unit for my machine and VCarve for design/gcode. I'm also no expert, but you should be able to move your spindle to where you want the job to start. Move your z so your tool bit is almost touching the PCB. In your software, you should then be able to reset the x,y and z co-ordinates to 0. This will be the start point for your job.

    That's how I do things. If you are unsure though, best wait for someone who has experience with the software to make a post.
    Bought a Chinese 6040...if only I'd known better :(

  3. #3
    Quote Originally Posted by Rye View Post
    Not used the Grbl software. I use an smc4-4-16a16b controller unit for my machine and VCarve for design/gcode. I'm also no expert, but you should be able to move your spindle to where you want the job to start. Move your z so your tool bit is almost touching the PCB. In your software, you should then be able to reset the x,y and z co-ordinates to 0. This will be the start point for your job.

    That's how I do things. If you are unsure though, best wait for someone who has experience with the software to make a post.
    Thanks for your quick reply - do you have/know of any more info/examples of setting up a new job/project on a cnc? This is the one I have (please don't buy from this users as they are very shoddy!!!)

    Thanks again.

  4. #4
    You could also set your Z 0 to just a fraction above your table, for example, stick a piece of paper on your table, bring your Z down till it just grips the paper and make this your Z zero. If your pcb was 3mm, then your starting height would be positive 3, and finishing depth would be 0. This would (should) then ensure there were no accidents.

  5. #5
    Fred's Avatar
    Lives in Reigate, Albania. Last Activity: 13 Hours Ago Has been a member for 2-3 years. Has a total post count of 34. Received thanks 3 times, giving thanks to others 1 times.
    Another thing to try is to raise the bit about 10mm above your PCB and set that to zero. Then do a dry run (also known as "cutting air") and make sure the tool path and speed looks as you were expecting. One thing to check is that non cutting moves are a few mm above the PCB, not at zero.

  6. #6
    Quote Originally Posted by Fred View Post
    Another thing to try is to raise the bit about 10mm above your PCB and set that to zero. Then do a dry run (also known as "cutting air") and make sure the tool path and speed looks as you were expecting. One thing to check is that non cutting moves are a few mm above the PCB, not at zero.
    Hi Fred,
    Ok sound interesting. So does that mean whatever software you use to run the *.nc file, the coordinates are offset from/to this? Would this be a rule of thumb procedure before each job?

    Thanks

  7. #7
    Quote Originally Posted by jamhot View Post
    Hi Fred,
    Ok sound interesting. So does that mean whatever software you use to run the *.nc file, the coordinates are offset from/to this? Would this be a rule of thumb procedure before each job?

    Thanks
    Before you start wrecking your machine have a good read through this :-
    http://www.cnccookbook.com/CCDIYCNCBeginners.html

    It will help you understand what you are trying to achieve
    ..Clive
    The more you know, The better you know, How little you know

  8. #8
    Brill - thanks Clive. I'll have a good read.

  9. #9
    To save your bed and table like metioned always cut air but if you want to see the actual cut then buy some thick insulation Foam and cut that first. This way gives enough time to react without damaging tool if goes wrong.
    Last edited by JAZZCNC; 22-01-2017 at 04:54 PM.

  10. #10
    Quote Originally Posted by JAZZCNC View Post
    To save your bed and table like metioned always cut air but if you want to see the actual cut then buy some thick insulation Foam and cut that first. This way gives enough time to react without damaging tool if goes wrong.
    Yeah good thinking - I thnk I need to get some blocks of wood or smilair material to test on (and use as a safty bed)! Thanks.

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