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Openbuilds CAM: Initial Height Sensing setup help needed

Discussion in 'CAM' started by IanCaz, Nov 4, 2020.

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  1. IanCaz

    IanCaz New
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    I apologize if I sound like a noob, but that's precisely what I am! I just built my first CNC Plasma Table & everything is going fairly well so far. There have been hurdles, but there's a lot of info I've been able to glean from this & other forums to get me going.

    One thing that's got me stumped is my floating head z-axis. I was able to get info that I need to setup OpenBuilds CAM's "Plasma: Initial Height Sensing G-Code", but I have no idea what to put in here!

    The placeholder shows:
    G0 + clearanceHeight +
    G38.2 Z-30 F100
    G10 L20 P1 Z0

    I believe the "clearanceHeight", is the distance it takes my limit switch to throw, which is about 2mm. I tried using:
    G0 z2 f100
    G38.2 Z-30 F100
    G10 L20 P1 Z0

    And I got to following:
    Error: 9 - G-code locked out during alarm or jog state [G10 L20 P1 Z0]

    Edit: It might be worth mentioning this is a custom built table running GRBL 1.1h on an Arduino Uno.
     

    Attached Files:

    #1 IanCaz, Nov 4, 2020
    Last edited: Nov 4, 2020
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    No, its how high you want to lift off the material.

    Thats really just a mockup to show "enter some commands here"

    You need to plan the sequence you need your machine to do

    Play with the serial console, refine the set of commands you want your machine to do. Write it down, refine it, play with it. Once you are happy you have a sequence you can use for any Plasma CAM (sheetcam, fusion etc too). Its not something OpenBuilds CAM specific, its specific to your machine build and what you want it to do
     
    #2 Peter Van Der Walt, Nov 5, 2020
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  3. IanCaz

    IanCaz New
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    Thanks so much for the quick response! My (main) problem is I'm unsure of the sequence I need my machine to do. This is where the noobiness comes in. My gcode experience is extremely limited.

    High level:
    1. Move to Z0.
    2. Probe down until Z-Limit switch triggers.
    3. Move back up to pierce height.
    4. Set Z0 to current height.

    Step #2 is what I'm having an issue with doing. I thought the G38.2 would stop once the z-axis limit switch opened, but that doesn't appear to be the case.

    One last question, the only switch I have on my Z-Axis is the float switch, which is hooked to the Z-Axis limit switch on my Arduino. Is this right?
     
    #3 IanCaz, Nov 5, 2020
  4. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Height Sensing switches sits on your Floating assembly (its not a Z endstop) and connects to your Probe input
    Its used to "sense" the height of material before each section is cut, as it may warp and lift from relieving stresses / heat while cutting

    If you don't have a floating head, and just rely on material being flat (3mm and up, smaller sheets) you don't need IHS (Initial height sensing)

    Watch this video, its the go-to tutorial at this time

    Part 1 Watch the whole video - lots of gold nuggets of learning in there. the floating head after is discussed around 9min in, while IHS in OpenBuildsCAM is discussed around the 33min mark



    Part 2 (update from some of the issues he had in Part 1)



    G38.2 = PROBE :) See G Codes
     
    #4 Peter Van Der Walt, Nov 5, 2020
    Last edited: Nov 5, 2020
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  5. IanCaz

    IanCaz New
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    That's a great video that I've actually seen before. As a matter of fact, that's what turned me on to Openbuilds CAM in the first place, and subsequently led me to use Openbuilds CONTROL as well.

    After rewatching that video, it seems I'm on the right path with my code (although my assumptions were off).

    It seems the biggest issue I'm having is that I have my floating head switch wired up to the wrong port! I'll swap that around after work tonight & see if that gets me what I'm looking for. He didn't go into that, since he's using the BlackBox, which I wish I had found before I had started ordering my electronics. :(

    Thank you so much for your time and patience!
     
    #5 IanCaz, Nov 5, 2020
  6. IanCaz

    IanCaz New
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    Okay, I was hoping I'd be able to come back on here tonight & say that everything is working great. Unfortunately, that's not the case.

    I got the probe swith hooked up to A5, normally open, when active, goes to ground.
    In the trboubleshooting screen, the probe shows OFF (green) when sitting in the air & shows ON (red) when I manually move it to the material. So far, so good!

    I've been playing in the console, and when I send the following:
    g38.2 z-30 f100
    I get the following in the console:
    [21:56:48] [ g38.2 z-30 f100 ] [PRB:-776.360,-365.666,-20.256:1]
    [21:56:48] [ g38.2 z-30 f100 ] ok
    And nothing moves, but I do hear a faint click (from the steppers?)
     
    #6 IanCaz, Nov 5, 2020
  7. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Could be EMI

    Consider getting a BlackBox - onboard noise filtering, plug and play
     
    #7 Peter Van Der Walt, Nov 5, 2020
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  8. IanCaz

    IanCaz New
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    Okay, I'm in IT and when reading this comment, it felt a lot like "Did you try turning it off & back on again?"
    I must adamantly apologize for that! I ran a single ground from the shielding on my probe cable to an actual earth ground & that fixed my problem immediately! I'm completely blown away! I've read all the posts about grounding & had all my shielded cables grounded, but they were grounded to my power supply ground.

    Thank you for all of your great support, the great software you guys have created & most of all for putting up with all of us noobs as graciously as you do! We certainly don't always deserve it!!!
     
    #8 IanCaz, Nov 9, 2020
  9. IanCaz

    IanCaz New
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    Okay, one last follow on question to this. I've got my height set after probing. On the plasma cutter at the local "Maker Space", they use a Hypertherm. For the HyperTherm, they recommend a "pierce height" that is roughly 1.5x the normal cut height. So, the height gets probed, move to pierce height, pierce, then drop back down to "cut height".

    Is there a way to do this in Openbuilds CAM? Or would I just add it into my IHS code?
    G38.2 Z-500 F500; probe
    G92 Z0; set workspace Z=0
    G0 Z12.2 F500; move to "cut height"
    G92 Z0; set true "cut height"
    G0 Z1.5 F500; move to "pierce height"
    M3 S1000; turn on torch for pierce
    G0 Z0 F500; move back to "cut height"
     
    #9 IanCaz, Nov 12, 2020
  10. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    You can add an M3 and extra moves to IHS yes, the second M3 we add will be ignored :)
     
    #10 Peter Van Der Walt, Nov 12, 2020
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  11. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    We've implemented a lot more functionality for Plasmas in CAM, but do be aware that the changes will conflict with your awesome Macro a little :)

    1) CAM itself now handles Piercing and moving between Z-Safe, Pierce, and Cut heights

    upload_2020-12-9_21-33-33.png

    2) Did away with the term IHS - calling it touch-off to make it easier to understand

    3) Added example Toolhead
    upload_2020-12-9_21-34-30.png


    4) The IHS (now called Touch Off) sequence now only has to probe/zero - example above sets it for you as below - can still customize if needed. As CAM itself handles the piercing etc now, it just has to touch off where the material is, and zero.

    upload_2020-12-9_21-34-52.png




    Unrelated to Plasmas, we added a Preview Gcode button - to speed up tweaking settings :) as you can quickly view the results directly in CAM

    upload_2020-12-9_21-35-46.png
     
    #11 Peter Van Der Walt, Dec 9, 2020
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  12. IanCaz

    IanCaz New
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    Just a little bit! WOW!!!

    This great progress & I'm loving watching this software evolve! You guys are awesome, keep up the good work! Now, to open a separate topic about my pierce delay problem.
     
    #12 IanCaz, Dec 20, 2020
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  13. Dave 20B

    Dave 20B New
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    I’m just trying to follow along here.... so how do I input the measured offset distance ( floating head spring displacement between touch down and limit switch activation) into the touch off command? Is this done as an additional parameter in the G38.2 command? (Newby here)
     
    #13 Dave 20B, Jan 5, 2021
  14. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Usually your mechanical setup should be such that touching the plate, triggers the switch.

    If you can't set it up like that, just account for the difference in all the CAM values. Say you need an extra 10mm, set cut height to 11.5mm for an actual 1.5mm cut height, etc
     
    #14 Peter Van Der Walt, Jan 6, 2021
  15. Dave 20B

    Dave 20B New
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    So just to be sure, if I’m using a floating head plasma arrangement with touch off, I should be inputting the cut height + spring / switch offset distance when cam setup asks for cut height?

    Also, for pierce height, I should be actually inputting pierce height + spring/switch offset distance?
     
    #15 Dave 20B, Jan 6, 2021
  16. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Theoretically then yes. Do test.

    How is your floating axis built that it allows distance between touching plate, and actuation switch?
     
    #16 Peter Van Der Walt, Jan 6, 2021
  17. Dave 20B

    Dave 20B New
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    I built a spring loaded torch torch holder carrier similar to the one in Dr. Dflo’s video. Once the torch strikes the surface during a z probe, the carrier moves up compressing the spring approximately 6mm before the probe limit switch is tripped.
    I was getting confused thinking that somehow my newly set z zero needed to correspond with the actual work surface so that my torch heights would be correct. Now I understand that is not necessary, as long as I account for the 6mm offset when specifying torch heightsin the settings for OB cam.

    thanks so much for the help!
     
    #17 Dave 20B, Jan 6, 2021
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