RAM EDM equivalent to Fadal VMC
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  1. #1
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    Default RAM EDM equivalent to Fadal VMC

    The Fadal VMC is known to have plenty of spare parts and a bunch of knowledgeable people out here to help support these older machines. Is there RAM EDM Equivalent.

    I am looking for a lower cost simple machine for the sole purpose of porting barrels.

    Thank you.

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    Hi coyotebgone:
    I have a Hansvedt CNC sinker (Hansvedt Foreman) from 1996.
    It is a simple machine for a CNC sinker...basically a manual spark generator mated to a simple 3 axis motion control system.
    It can orbit it can vector in all directions, but it cannot control it's output on the fly in response to changing spark gap conditions like a "real" EDM machine can.

    However, it is very well supported by Arrow EDM Services in Illinois even though it's an old donkey.
    The folks at Arrow are super helpful and really know the Hansvedt machines: Arrow is a truly great company to deal with.

    So the Hansvedt is a good fit to the analogy of "the Fadal of Sinkers".
    Repair parts are readily available, it's cheap to fix, nothing is very complicated so with directions from the gentlemen at Arrow, I've been able to fix a variety of small problems that have arisen, and the worst repair bill I've encountered in fifteen years has been under a thousand bucks.
    That involved shipping the control from Vancouver, Canada to Rantoul, Illinois to repair two blown boards in the gap sensing module.
    I just had a Z axis servomotor fixed a month ago and the tab was $420.00 (blown encoder and shot motor bearings).
    It was back on the machine in under two weeks.
    Compared to fixing even a small problem on an Agie or a Charmilles, that's chicken feed.

    So to meet your particular needs if you can live with the primitive control and its severe limitations, it's a solid choice.
    Mine cost me fifteen grand in 2004.
    If you want or need a synopsis of why I'm calling it a "primitive control" I encourage you to have a look at the recent post started by Kevin Potter.
    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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    In paragraph 1 you mention spark gap condition. is this impactful relative to the limited work I will being with it. (porting barrel)?

    I am a newby and have never used an EDM. (but I guess thats probably not news to you). Thank you.

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    Hi again coyotebgone:
    The EDM process relies on maintaining a gap between the workpiece and an electrode and that gap is filled with a dielectric fluid who's function is to create just enough electrical resistance that electrons moving from electrode to workpiece or vise versa need enough current and voltage to generate a usefully powerful spark as they hop across the gap.
    Maintaining the gap at the correct width and the correct dielectric strength is the whole art; it gets dirty with conductive particles which must be flushed out frequently, and the dielectric strength of the fluid in the gap changes continuously as the fluid is ionized and then recovers.
    So there is sensing circuitry which decides when to stop advancing the electrode toward the work and permit the discharge of a current pulse to blow a bit of the workpiece away, and it decides based on the voltage across the gap.

    As the burn gets deeper, the used fluid becomes more difficult to flush out and the performance suffers accordingly.
    An additional complication is that as you change how much current to put into each pulse and how often, you also change how big the gap has to be and how rough the finish will be.

    A modern sinker control will ask you for the finish you desire and the difference between the electrode size and the size of the cavity you want to cut, and will get there as quickly as it it can, continuously deciding how much power to put into each spark while still allowing the dielectric fluid to recover and be replenished, also making sure it never permits such a big spark as to intrude into the final part size.

    So it starts out with high power at first and gradually winds down the power to give a fine finish.
    In addition, since it needs a smaller gap for finishing, it also typically moves the electrode in small circles that get bigger and bigger as the power goes down, the gap gets smaller, and the finished size is approached.
    So the electrode is deliberately made smaller than the shape it's going to produce and the size of the final electrode "orbit" determines how big the burn ends up.
    A typical nominal orbit is 0.005" so the electrode is made 0.005" per side undersized but the actual electrode motion is not a circle of 0.005" radius... it's less than 0.005" by the width of the spark gap and that is always changing so you can see how complicated it all gets.

    My machine, and others like it with "primitive controls" cannot do any of this automatically...you have to tell it what you want it to do and it just does that, regardless whether what you told it makes sense or not.
    A fully adaptive control by contrast, asks what you want to end up with and then finds the best way to get there without you explicitly having to tell it anything about how to do it.

    You will have to find a way to get what you want whenever you make a burn of any kind, and the deeper and narrower the burn, the harder it is to keep it going if you have to actually tell it which (of a half dozen different settings) to change as the spark gap conditions change.

    That's what makes manual sinker work so challenging to do efficiently...you can do a burn in an hour on one day and fuck around for ten hours the next time on exactly the same burn, just because of some tiny flushing problem in an obscure corner of your electrode.
    A modern fully featured sinker will never let such a condition develop in the first place, so they burn way faster and won't make your hair go grey, but they're complicated and cost a lot.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining
    Last edited by implmex; 10-08-2019 at 03:58 PM.

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    Default thanks.

    Thank you for the input. Your right I want to port barrels I dont' want to be an EDM Expert. I will look for a newer edm.


    I appreciate your thoughts.

    Herschell

    Quote Originally Posted by implmex View Post
    Hi again coyotebgone:
    The EDM process relies on maintaining a gap between the workpiece and an electrode that is filled with a dielectric fluid who's function is to create just enough electrical resistance that electrons moving from electrode to workpiece or vise versa need enough current and voltage to generate a usefully powerful spark as they hop across the gap.
    Maintaining the gap at the correct width and the correct dielectric strength is the whole art; it gets dirty with conductive particles which must be flushed out frequently, and the dielectric strength of the fluid in the gap changes continuously as the fluid is ionized and then recovers.
    So there is sensing circuitry which decides when to stop advancing the electrode toward the work and permit the discharge of a current pulse to blow a bit of the workpiece away, and it decides based on the voltage across the gap.

    As the burn gets deeper, the used fluid becomes more difficult to flush out and the performance suffers accordingly.
    An additional complication is that as you change how much current to put into each pulse and how often, you also change how big the gap has to be and how rough the finish will be.

    A modern sinker control will ask you for the finish you desire and the difference between the electrode size and the size of the cavity you want to cut, and will get there as quickly as it it can, continuously deciding how much power to put into each spark while still allowing the dielectric fluid to recover and be replenished, also making sure it never permits such a big spark as to intrude into the final part size.

    So it starts out with high power at first and gradually winds down the power to give a fine finish.
    In addition, since it needs a smaller gap for finishing, it also typically moves the electrode in small circles that get bigger and bigger as the power goes down, the gap gets smaller, and the finished size is approached.
    So the electrode is deliberately made smaller than the shape it's going to produce and the size of the final electrode "orbit" determines how big the burn ends up.
    A typical nominal orbit is 0.005" so the electrode is made 0.005" per side undersized but the actual electrode motion is not a circle of 0.005" radius... it's less than 0.005" by the width of the spark gap and that is always changing so you can see how complicated it all gets.

    My machine, and others like it with "primitive controls" cannot do any of this automatically...you have to tell it what you want it to do and it just does that, regardless whether what you told it makes sense or not.
    A fully adaptive control by contrast, asks what you want to end up with and then finds the best way to get there without you explicitly having to tell it anything about how to do it.

    You will have to find a way to get what you want whenever you make a burn of any kind, and the deeper and narrower the burn, the harder it is to keep it going if you have to actually tell it which (of a half dozen different settings) to change as the spark gap conditions change.

    That's what makes manual sinker work so challenging to do efficiently...you can do a burn in an hour on one day and fuck around for ten hours the next time on exactly the same burn, just because of some tiny flushing problem in an obscure corner of your electrode.
    A modern fully featured sinker will never let such a condition develop in the first place, so they burn way faster and won't make your hair go grey, but they're complicated and cost a lot.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

  6. #6
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    I guess I'm missing something here but where do you find a machine with a tank big enough to hold a rifle barrel?
    Bob


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