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Thread: Problems with PoKeys57CNC Plasma plugin

  1. #13
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    Default Re: Problems with PoKeys57CNC Plasma plugin

    You are wrong.The THC is handled directly by the motion controller hardware and not by mach3 so it does not have to be realtime. The microcontroller or FPGA works realtime on the THC signals.
    The motion is buffered and therefor everything is realtime, because the motion controller has all motion information in advance before controlling the THC.



  2. #14
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    Default Re: Problems with PoKeys57CNC Plasma plugin

    The difference is that a cheap arsed 64 bit Celeron CPU like the tiny J1900 I've mounted to the back of my monitor has so much more processing power than a simple FGPA. In any case, the ESS is attempting to be a motion controller yet is only capable of step generation at about 3 mHz. In my world I use the FGPA on my Mesa 7i76e to generate steps at up to 10 Mhz under the direction of THE_MOTION_CONTROLLER being LinuxCNC.

    In my world, because the THC operates as part of THE_MOTION_CONTROLLER, I can do things that are simply not possible on a buffered environment becasue in my world, I know exactly what is going on every millisecond. eg. I know the current velocity v's commanded velocity, so I can hold the THC if velocity falls below say 90% of what was commanded. I can calculate the rate of change in volts per second so I can sense a void/kerf crossing, I can auto sample volts when I want to and I have the ability to use the power of LinuxCNC's High performance proven PID modules and the new external Offsets to take total control of the Z axis height (be it THC adjustments, pierce height or cut height) without any gcode. Heck, I can even sense when we are cutting an arc in THE_MOTION_CONTROLLER and calculate the radius and change cut parameters based on whatever algorithm I choose to code.

    Furthermore, I can command precise adjustments to Z axis height based on the deviation of torch voltage from the desired set point (which I always sample so I don't need to worry about cut charts so much). For example, I know that torch volts varies with 99.8% confidence at 7.53 volts per millimetre. So rather than a dumb bit bang up/down approach used by most THC's to adjust the torch height, I can make a precise calculation on how much the torch height needs to be varied and apply that offset to the Z axis becasue I am THE_MOTION_CONTROLLER. Not only that, I can adjust that calculation every millisecond. It is these features that early adopters in the LinuxCNC world are throwing their external THC's in the scrapheap and are choosing to adopt LinuxCNC, THE_MOTION_CONTROLLER for THC.

    Best of all, this system I describe is packaged and waiting for you to try on the LinuxCNC forum for free if you are not totally wedded to the Windows Operating System.

    Rod Webster
    www.vehiclemods.net.au


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    Default Re: Problems with PoKeys57CNC Plasma plugin

    Ohh, I'm not that fast that I could do things in milliseconds.
    10MHz what the ... when most stepper drives can't take even 0.2MHz. I see that high frequency useless for my system and probably for most of the systems. Even 3MHz is much more than enough.

    Thank you for the offer, it is kind of you, but I'm happy with my current system and I'm too old to learn a new operating system (Linux). How is it said? If it's ain't broken then do not repair it.



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    Default Re: Problems with PoKeys57CNC Plasma plugin

    Hi,
    Here is the problem with MACH and any external motion system . Its not real time
    That incorrect, the ESS handles THC on board without reference to Mach, ie realtime.

    Warp9 have just released (approx. 10 May 2019) their new THC feature for Mach4.

    Mach is still the supervisor and sends to the ESS the parameters to apply but the application of those parameters are done on board
    without requiring intervention from Mach and therefore the communication delays associated with any buffered control system.

    Craig



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    Default Re: Problems with PoKeys57CNC Plasma plugin

    Quote Originally Posted by Torchhead View Post
    The Neuron guy has a quasi stand alone THC that does not need a lot of back and forth to MACH

    TOMcaudle
    CandCNC – CNC Control Electronics for Plasma and Router
    Correct. Neuron this is a full stand alone THC and require to/from CNC only 3 IO signals - START (M3/M5), THCOFF and ARCOK - it's can be software or hardware signals - both can processed in same time.

    Cortex ARM on board processor allow to make all calculations and controls in REALTIME. For example, the controller main cycle loop is 1 ms. This time is sufficient for measuring the arc voltage, filtering this value and processing in the PID controller.
    From my experience I can say that if I increase controller main cycle loop to 15 ms and more - noticeable delay in torch height control.

    Neuron plugin use Mach3,4 or UCCNC controls only as programming interface for operator. This is a cutting profiles (cut height, arc voltage, pierce height, pierce time and etc), plotting graphs for setup and diagnostics, controller engine settings.

    Best Regards!
    Andrew.


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    Default Re: Problems with PoKeys57CNC Plasma plugin

    Hi,
    the only problem with hardware THC units described by shad71 is they cause the loss of Z reference of the machine.

    The machine has no idea how many pulses and whether they are up or down.

    The current THC solution enacted by the ESS for instance accept up/down signals from a voltage measuring device and cause up/down
    motion of the Z axis in realtime but additionally the number and direction of the pulses are copied back to Mach so that it
    retains reference.

    There is a delay (180ms by default in Mach4) between the up/down THC pulse and the DRO updating but the movement is realtime.

    Craig



  7. #19
    Member shad71's Avatar
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    Default Re: Problems with PoKeys57CNC Plasma plugin

    It does not matter, because Neuron is full stand alone. CNC controls doesn't even know about the z axis - only XY. Torch Z slide and plasma cutter under full Neuron control.

    Attached Thumbnails Attached Thumbnails Problems with PoKeys57CNC Plasma plugin-uccncplasmascreen-jpg  
    Best Regards!
    Andrew.


  8. #20
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    Default Re: Problems with PoKeys57CNC Plasma plugin

    Hi,
    yes I fully understand, I have worked on several machines that have the Z axis that are controlled in that fashion and it works well for 2D shapes.

    If you want 2.5D capability or the ability to vary the torch angle from vertical for the purposes of beveling then genuine Z (and more) axis control is required.

    Craig



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Problems with PoKeys57CNC Plasma plugin

Problems with PoKeys57CNC Plasma plugin