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Thread: Wiring Mach3 with a wire EDM

  1. #1
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    Default Wiring Mach3 with a wire EDM

    Hi again

    I'm now in the process of building/designing the wire EDM and probably will use Mach3 to control it. I do though have some problems that I'm not exactly sure of how to deal with.

    1. I know that I can wire an input and in Mach3 instruct that this and this input should act like a button, but how is it done at Mach3's end? I would like to include feed hold and reverse run buttons.

    2. Does the Mach3 reverse run from a feed hold situation?

    3. For feed hold and reverse run signals, what would you recommend? Measure the gap voltage and if it is too high, feed. If it is too low (short), reverse run and if it is between the extremes, feed hold? As I remember that Mach3 doesn't do variable feed rate based on an input or does it?

    I really would like to get it process controlled and not waste wire by running the machine "slow enough so it won't short"

    FYI, the machine will have about 250 x 250 mm working area, has an adjustable Z height (around 100 mm max height). The moving parts are "inside" the tank area, so nothing protrudes from the machines footprint once in place. Linear guide rails with linear bearings and C7 accuracy ballscrews with stepper motors on them. Pulse type power supply (probably around 20-50 kHz). I'll have test and see but for now the plan is to have a wire brake that can be adjusted (a stepper motor shorted with a pot) and an adjustable wire speed and pressure flushing that can be adjusted from 0-2 bar pressure probably.

    The filtering system will have a magnetic filter, a regular filter and a deionizing tank in series so that I can good and reliable water in the working tank.

  2. #2
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    Have you gone to the Mach3 support forum? www.machsupport.com
    ----------
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  3. #3
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    The Yahoo Mach group is very good as well. http://groups.yahoo.com/group/mach1mach2cnc/

    Sorry, I'm a real noob with Mach but have been very impressed with the program and all the great guys that support it. I wish I knew enough to intelligently discuss your question.
    Milton

    "Accuracy is the sum total of your compensating mistakes."

    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

  4. #4
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    I threw the same questions on the Mach3 support forum, time will tell

  5. #5
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    I have absolutely NO experience with EDM, but...
    I'd second the recommendation to check out the machsupport.com forums. Also, I'd suggest checking out linuxcnc.org for EMC. For some things setting up EMC is much easier than Mach3 (eg. for mills, IMO). Plus it's free, so you can't beat that.

    As for how to do X with a real button input, you need to map that button input to a function that does whatever you want to do. There's usually a few ways to do anything you want to do. I'd suggest reading some of the programming guides at machsupport and asking about how to specifically implement whatever you plan to do. What I'd suggest is to start with something simple for the action - eg. zero an axis when the button is pressed - and once you understand how to map a button action to a script/function then you can implement whatever you specifically want to do in code.

    Also, cnczone may have some examples of others who have done the same. No point re-inventing the wheel!

  6. #6
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    Quote Originally Posted by JoeBean
    Also, I'd suggest checking out linuxcnc.org for EMC. For some things setting up EMC is much easier than Mach3 (eg. for mills, IMO). Plus it's free, so you can't beat that.
    Sure it is free, but it does not have reverse run at all. That is something I wold like to have, so that the machine really is automatic in operation and doesn't just halt.

    Variable feed rate based on the gap voltage & reverse run in case of a short would be the best combination, but EMC2 and Mach3 only support one of those and not both. Unless someone tells me how to do variable feed rate in Mach3?

  7. #7
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    Quote Originally Posted by JoeBean
    I have absolutely NO experience with EDM, but...
    I'd second the recommendation to check out the machsupport.com forums. Also, I'd suggest checking out linuxcnc.org for EMC. For some things setting up EMC is much easier than Mach3 (eg. for mills, IMO). Plus it's free, so you can't beat that.
    And I wouldnt pay a cent more.

    I have never heard easy to set up and emc in the same sentence.

    Jaakko, setting up external buttons to control things is pretty easy. I am going off memory here so it may not be right on. Reverse run is code 279, feed hold is 1001. In the input port configuration dialog you set up your input pins under Trigger 1 and 2. Then under the edit menu you select system hot keys. It will list the trigger inputs and you enter the code for the function for the trigger associated with the input you use.

    My guess it will reverse since people build hot wire cutters with these machines.

    You might be able to do something using the feed rate override and tie it into current monitoring via a comparator. You could use something like a Pokeys which will give you analog inputs that mach can be made to see. A voltage of 0-5v will control the feed rate, how much will depend on how you write the "brain" (Mach3's built in ladder logic system). So as the current goes up you invert that and feed it into the feed override.

    The big problem you will have is the machine will want to oscillate. You really need a PID filter as this is a servo loop. You might be able to do something with a microcontroller. You could also use something like an Omega temp/process controller in the loop, I would think. There are one with analog input and analog control output. The Controller would set the current and run mach at a feed rate that would maintain it.

  8. #8
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    macona, thank you for the information, at least sounds very easy to use that trigger input system you described.

    Yep, the oscillation issue springed to my mind also, but it isn't that much of an issue as the process is generally so slow that the oscillation is also very slow (basically the feedrate wants to oscillate if it is controlled by the gap voltage.

    And I want to monitor the gap voltage, not the current, as the voltage basically dictates how the cutting goes and I don't think the current exactly reflects that.

    The PoKey plugin sounds good, though I'll have to see later about adding that. I'll start out with a simple control and make it more process dependent once everything works otherwise

  9. #9
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    Digging a bit more I would look at a Omega CN9000 series controller, specifically the CN9151A. This has a selectable option for a 0-20mv or 4-20mv linear process input. You could tie this in to a current monitoring device. I would use a LEM hall detector. You can then use a voltage divider to scale the input for 20mv = full current. The controller has a 0-10v output so again, use a voltage divider to scale the output for the PoKeys. The controller will allow you to set the current 0-100% and handle the pid loop. You would probably have to rewrite the brain in mach to invert the input of the feed override do full voltage means 0% speed and vice versa.

    It ought to work...

  10. #10
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    See you want it to be voltage. I would use an isolation amplifier to connect to the input of the controller.

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