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Homing

Discussion in 'General Talk' started by arp, Jun 7, 2021.

  1. arp

    arp New
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    I believe the home position in the lead.1010
    Is front left but I want to home back right as that's where it's out of the way is it a simply job of reversing home direction in the firmware somewhere or is it more complex
    P.s just finnished a 12 hours at work and did a little more work to machine
    Here what she looks like
    PXL_20210607_180310679.jpg
    I need more time to research and build but work is busy
    [​IMG]
     
  2. Kevon Ritter

    Kevon Ritter Veteran
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    Home is where ever you want it to be. Most people home at +X +Y like you have specifically for the purpose of material handling.
     
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  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Set $23 Homing Dir Invert to 0 ($23=0): See gnea/grbl (the Grbl wiki is a must-read (; )
     
  4. arp

    arp New
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    Thanks M8 if it's a must I'll do it
     
  5. arp

    arp New
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    Ok all set every thing moves in the right direction and all homes nicely now but it's nose is this a case of cheap stepper motor chips (just guessing as chip chips with 3d printer make the motors talk louder not sure if that's also true for bigger motors on CNC ) are do I need to set the motor adjustment on the side of the blackbox I set them all to half I'm using 2.8amp motors or is it the case of
     

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  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Halfway up is a good starting point. We have high torque drivers, not quiet, but strong. Not like you are going to hear the stepper motors over the noise of the spindle and the bit cutting away at a big piece of stock vibrating on the bed anyway (;
     
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  7. arp

    arp New
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    Not sure what happened there but the last part is

    Is it case of if it's not broken don't fix it lol. And thankyou Peter your a star
     
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  8. arp

    arp New
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    Ok next problem setting max travel I have it set to 750 yet I can move it to -880 yet I think the problem is I need to set max travel to -750

    How do I set max travel to - 750
     
  9. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Checkout github.com/gnea/grbl/wiki
     
  10. arp

    arp New
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    ok been reading still can not find how to set -750 as max travel here is what i got so far
    $131=750.000

    type $ to mess with commands(layman's terms please excuse)
    next is command line i want to mess with in this case 131 which is y max travel in mm
    = tells it what i am setting it to all simple so far
    but i do not see how i set an minuses number

    i want the machine to home back right not front left and when its cutting i want to be able to read the text as its cutting
    now i could invert the axes so the machine thinks the back is the front and the left is the right and that would work id then be moving forward to max travel but when its cutting text it will all be backwards untill i flip work peace around and will bug me

    it cart be $131=0750.000
    first 0 for invert dose not seem right to me
     
  11. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    By setting Max Travel and if you want to stop the machine exceeding Max Travel too you have to enable Soft Limits, as explained here: gnea/grbl where they say
    Thus also see the Soft Limits section here: gnea/grbl

    Which in turn will tell you Soft Limits rely on a working Homing setup, so sort that out first :) - its all there in the Wiki. The reason I ask you to read it all, is because a lot of it is interconnected as you can see above.

    Yes, it is a positive number. Negative lengths are impossible - your axis has to be longer than 0. (its a "how long is that axis" not a "where") so how long is your axis, it is 750. If it was -750mm long you would not have a machine existing in this dimension.

    See this FAQ entry to understand the negative quadrant space gnea/grbl

    Use OpenBuilds CONTROL it gives you a nice User Interface on the Grbl Settings tab

    Then set Homing dir to 0. See the dropdown menu in CONTROL > grbl Settings > $23 Homing Dir but read gnea/grbl to understand.

    Not at all related to homing. That means your motors are reversed! :) fix that FIRST BEFORE ANY OF THE ABOVE by going to Grbl Settings, $3 Direction Invert and fixing whichever axes are reversed until your machine conforms to the Cartesian Standard. That is:
    X- jog moves tool towards the left
    X+ jog should move tool towards the right of the stock
    Y- moves tool toward the front side of the stock
    Y+ moves tool to the back of the stock
    Z- moves tool down toward and eventually into the stock
    Z+ lift it up, out of the stock and away from the stock


    To recap:
    Fix $3 Dir Invert first to get machine compliant with Cartesian standards
    Then setup Homing correctly.
    Once homing is correct to standards and whereever you prefer your switches, then you can consider your options. Enabling soft limits (not beginner friendly by the way) or just buy 3 extra switches for Hard limits if you are worried.
     
  12. arp

    arp New
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    the direction my machine moves is standing at the front of the machine
    y away from me is + towards me is -
    x left is + right is -
    z up is + down is -
    that said having read your above message i realize i need to set home switch as 750 and soft limit as 0 is this possible
     
  13. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    That needs to be reversed-

    Home switch, if you have it at Back/Right as you mentioned above, would be 0. The far end (front, left) would be -750 and negative whatever the other axis length is. Because Machine coordinates are always in the negative quadrant as explained in

    If you leave the switches front left, then the switch will be -750 and the other end (back right) will still be zero, so that the machine still complies with being in the negative quadrant. Very important to honor this standard as most CAMs expect the Machine coordinate envelope to be compliant with the standard


    Apart from machine coordinates you SETZERO your "work" coordinates in positive, negative, or a mix, depending on where you CAM up the origin relative to your Stock.
     
  14. arp

    arp New
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    z home switch is down by router and home is fully up out of the way its the only axes left - lowers it and + raises but lowering it towards base board make it move in negative numbers

    other two axes move in plus number moving away from home switches
     
  15. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Z should ALWAYS home UPWARD away from the stock. CAM's expect to do G53Z Moves for safe clearance up and away from clamps/stock for safety. That is a non-negotiable. Switch should be mounted such that RAISING the Z axis, triggers it. Where its actually mounted is up to you, as long its functionally triggers with Z+ moves, and Z+ moves lifts the bit up and away from the stock

    Correct then!


    Correct, from your question, it really sounds like you still haven't read that FAQ link? (;


    Please do so now
     
  16. arp

    arp New
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    reading it now thanks i see why its hard to get my head round it having built two 3d printers one with ramps boards prusia i3 type machine and the other coryxy duet wifi machine ok not much of 3d printers translates to cnc so i need to start from scratch any other useful links i should read please post many thanks for your help
     
  17. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    The entire Grbl Wiki (every page, even ones you don't think will matter, contains golden information) and docs.openbuilds.com/blackbox (properly hooked up hardware prevents expensive mistakes that kill electronics) is all worth a read

    Yip, subtractive vs additive, and the reprap guys really refused to follow a lot of CNC standards that dates from the 60s - arrogance of developers in that community won :( but makes it hard when you work back to things that are to-standard
     
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  18. arp

    arp New
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    Just thought I'd Finnish off with showing my first use of my machine the old pencil test
     

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  19. arp

    arp New
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    heres the first cut video nothing fancy a quick mock up with openbuilds own cad/cam web interface and a quick video of her running im very impressed

    thank you peter for your help ill stick with your cad/cam/web interface for a while
     

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