1. Ok, the basic height control project is complete, but got sidetracked by the advanced height control project. I will loop back and update this as soon as I can get back to it.

Plasma Torch Initial Height Sensor - Prototype

Discussion in 'Basic Height Control' started by SignTorch, 5/22/14.

  1. SignTorch

    SignTorch Artist

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    Ok, made some progress on the touch probe.

    Not ready for production. Still must develop a fail-safe mechanism before it can be used and really tested.

    It's very simple and very sensitive. It's almost too good to be true, so until I can test it right, I'm not sure I believe it can be that simple and that effective without some sort of problem, so stay tuned.

    It detects through heavy rust, paper, and skin (if grounded). It can touch off on a bowed piece of .005" brass shim stock without flexing it at all.

     
  2. SignTorch

    SignTorch Artist

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    here's the test circuit, not much to it...

    probe-breadboard.
     
  3. SeanP

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    Looks very impressive! will be keeping a close eye on this one ;)
     
  4. SeanP

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    Hows testing going with this Gary? it sounds like a good job!
     
  5. SignTorch

    SignTorch Artist

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    Well, it was going good, then I started experimenting with a ATHC and haven't been able to put that down.

    I've been meaning to take a break and post an update. Just a couple to a few more days and I'll do that...
     
  6. SeanP

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    Good stuff Gary,,,,,,no panic at all, anytime.
    Good luck.
     
  7. bmquist

    bmquist registered

    could you share your circuit diagram for the ohmic sense please? :) It seems to work really nice!
     
  8. SignTorch

    SignTorch Artist

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    sorry I didn't answer sooner - there was a glitch preventing me from seeing new messages

    yes - I've been meaning to - I even developed a kit for it - just been running in circles - ever since I took apart my old router to make the gotorch work - every project turns into a z axis rebuild - I've almost got a replacement built - once I get that then the initial height sensor is at the top of the list of things I can't wait to get back to work on

    I've been using one all this time and it seems to be working fine -
     
  9. mcagauto

    mcagauto member

    Any updates on this I would like to get one.
     
  10. SignTorch

    SignTorch Artist

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    no - the weather has been so nice - I could just stay outside 24-7 -

    about all I have ready is the circuit diagram - and a photo of the prototype

    ihs. ihs2.

    the ohmic probe is represented as a resistor but of course it's actually an isolated touch plate that detects ground contact

    the probe runs through normally closed contacts of the same relay that turns the torch on - so that the probe is not connected to the circuit when the torch (or spindle) is on

    I usually adjust sensitivity (via R7) to just detect my skin when I'm grounded - that seems to be a good setting - any more sensitive and it can false detect through moisture or dust - especially moisture or dust on the circuit board itself - my prototype is sealed in solid plastic

    I use a water table and water drops don't really collect on the probe or puddle under it (thanks to air post flow) - but it would detect on a water drop and of course that would not be accurate or useful - I haven't had any problems with that lately - but during development on a breadboard it was obvious that water, moisture and dust (even fog) can easily interfere with sensitivity adjusment and stability and detection reliability in such a circuit

    U2 is one half of an optoisolator - the other half (not shown) couples the probe signal to the BOB - the optocoupler and LEDs are optional but recommended

    it shows 12 volts but I think it should work with almost any reasonable DC voltage - if you use a higher voltage then eliminate or replace TVS-18V transient voltage supressor accordingly (that componenet isn't necessary)- maybe increase R5, R8 and R9 for 24V

    it's a fairly simple op amp circuit - I'm out of time to explain how it works at the moment
     
  11. East German

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    Hallo,

    Thanks Gary

    Here is a small price Version, works fine on every years by my plasma table.

    Cost in Germany 11.37€.

    Best Regards Peter

    Watersensor.
     
  12. SignTorch

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    are you saying that works as a torch height touch probe - or as a water level sensor - ?
     
  13. East German

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    Hallo Gary

    I built in the last few weeks, a test board with smooth stepper from Warp9.
    I have the motors from my old system connected to my test board.

    Here is a Touch Test with the Waterswitch, on my old Machine Board is the Waterswitch every years:


    Test the SC Cutting Rule in the Corner is THC Signal off, the lamp over the Proma THC is out:


    First Cut with the Testboard:


    Regards Peter
     
  14. SignTorch

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    I love it - all that slag on your slats your machine must have more miles than my car - I've yet to cut one whole sheet of steel in total

    that's very interesting - I would have never even thought that an inexpensive off the shelf liquid level sensor would work for initial height sensing

    in the first vid around 52 seconds in I notice it does flex the material a little bit - which makes me wonder if you're probing too fast and/or what the sensor response time is

    my problem is I didn't want it to flex the material, ever, whatsoever - which means I had to probe slower and have a fast response time - not only to avoid inaccurate height readings - but when using it to set the height on router bits (especially when touching off on hard flat material with no flex) there is much less margin for error - it just has to stop immediately and not run past the contact point whatsoever - (in routing circuit boards and things) I regularly use really small carbide tools like .025" diameter drill bits and .03" end mills

    of course since your system has automatic height control then initial height sensing accuracy is not as critical - but I'd test that thing for repeatability using g31 commands repeatedly at various speeds just to know what the margin of error is - it looks to me like you're probing too fast and I saw the plate flex which I know affects height detection accuracy

    I haven't got into auto height control yet but I love to see the videos and hear about any tricks to using them - that's the most interesting thing
     
  15. East German

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    Hallo

    I need to clean the machine:mad: since any Miles on the DRO:thumbsup:

    I have worked for several years with the G31 in the Macro m3.
    Now I test with the G28.1 in the G code.
    The G31 does not work with the ESS and System rotation from Mach3.

    I built in the past few weeks a screen for Mach. 3
    The goal is to have a better control of the Z axis with the Gamepad.
    I just test the screen.
    Peter

    Simpel Plasma6pr.
     
  16. SignTorch

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    I like the grey tones -

    I haven't tried ESS - I'm glad to know it doesn't support G31

    I haven't used G28.1 much - same difference I suppose - I like G31 (for routing) for touching off on the sides of a part

    Not familiar with the gamepad either -
     
  17. East German

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    Hallo Gary
    I would be interested if the touch with G31 and rotating G68R45 works with you?!

    For me, it comes during the touch to movements of the x axis:m1:

    Start from Here ist not working with the System Rotation from Mach3!

    Regards Peter
     
  18. SignTorch

    SignTorch Artist

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    I'll have to try G31 after G68 -

    now, why are you using G68 ?
     
  19. East German

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    I use it to small pieces to rotate.
    To have little scrap.
     
  20. SignTorch

    SignTorch Artist

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    ok - in Mach3 - G31 and Run-From-Here does work when G68 is active
     
  21. East German

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    OK Gary
    I had problems with it;)

    Sometimes you do not understand the world.
    But Mach3 is a very good program.

    Regards Peter
     

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