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EDM Applied to make PCB's

Discussion in 'Electronic Design' started by D from BC, Dec 16, 2006.

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  1. D from BC

    D from BC Guest

    Has anyone had a PCB made by an EDM?

    I admit, it's perhaps a weirdass method of making a circuit
    board but does it work? Is it slow? Anybody have a homemade one?

    Background Info

    EDM (Electric discharge machine)...There are commercial units
    available on the net for metal machining.
    An EDM creates an arc that vapourizes the unwanted metal.. I
    believe this can be done in pure water. No smoke.

    This is like direct printing so no etch chemicals and no etch
    resist required.

    You know if I find out this works I might convert my ink jet
    printer into a CNC and make an EDM for small boards..

    As a rough experiment, I used a microwave oven transformer and
    zapped a PCB in a tray of water... Cool seeing 2kV arcing in
    water. Surprised to see only a few tiny bubbles for such high
    energy ....I successfully made a tiny hole in the copper only.
    Industrial EDM's I think use much lower voltages.
    (Please do not copy my experiment unless you are familiar with
    high power& high voltage.)
  2. Eeyore

    Eeyore Guest


    Why would anyone bother ?

  3. I believe kerosene is a more commonly used fluid.
  4. Luhan

    Luhan Guest

    Hmmm, 2 kv sparks plus kerosene ???

    [Luhan looks for rock to hide under...]
  5. Guest

    I had a PCB made with money. Money is a widely used substance that
    allows one to transfer onerous tasks over to someone specialized in
    said task. Money has no particular storage requirements. I mean, I like
    steak, but it wouldn't occur to me to get my own cow.
  6. DJ Delorie

    DJ Delorie Guest

    Some friends of mine have their own cows. And pigs, and other
    animals. They haven't had to pay store prices for meat in years.
    They're called "farmers". Without them, you wouldn't be able to get
    meat either.

    It takes all types. Some of us are DIY, some of us are $$$, some of
    us are both. Can't you just accept that different people like doing
    different things?
  7. D from BC

    D from BC Guest

    Hmmm, 2 kv sparks plus kerosene ???

    [Luhan looks for rock to hide under...]

    Yes I know...1kW energy + fuel=more danger....Isn't kerosene
    similiar to jet fuel.. This could spark some
    about zapping in liquid propane. ;)
    I do recall there are other liquids used for EDM.
  8. Guest

    I don't think it's a very good fit.

    EDM tends to come in two varieties. One is very localized, either
    point-type, or a wire "saw" which cuts all the way through something.
    Covering a whole pcb with a point type operation would seem rather
    slow, but I suppose might be an option for designs where you can leave
    most of the copper and simply use thin outlines of removal to isolate

    The other is a larger area operation, but requires a shaped electrode -
    essentially, making a die. Usually this is a quite messing operation
    of machining a block of graphite.

    When photoresist is not used, the preferred choices in practice seem to
    be either a specialized milling cutter, or a laser system. My employer
    uses both to make small geomotery-critical microwave boards, generally
    on teflon substrate.
  9. Guest

    Good for them. Ask them how much effort and machinery is required if
    all you want is *one* filet mignon. I mean I like wearing T-shirts, it
    would never occur to me to open my own sweatshop.
    Also ask them if they sell the rest of their meat? Wouldn't your
    comparison imply that if you make your own PCBs you should sell some if
    it's comparable to the farmer's case? The farmer is just *gasp* like a
    PCB shop.
    Exactly, they're called farmers, and god bless them for we are all
    parasites on them in the end...
    Farmers call themselves farmers, I'd bet. They don't call themselves
    "gourmets" and then go around asking on gourmet groups about how to
    make your own steak, am I right?

    Just like a farmer grows meat, a PCB shop makes PCBs. It's really quite
    simple, otherwise they wouldn't call themselves a PCB shop.

    My problem is that this is an electronics group, and we have people
    wasting time and energy on something that's been done for 50+ years and
    is easily accessible with pocket money today, instead of building
    phase-locked oscillators or PIC based LED flashers.
    Building my own PCBs is a phase I went through in high-school, and then
    quickly abandonned as my projects became more than 1 IC with 1
    No one asks how to make their own resistors out of nichrome wire...
  10. The O.P. might take this idea to one of these Yahoo
    discussion groups:

    I can imagine this technology becoming an environmentally
    friendly way to make boards, if sufficiently developed.
  11. I made a couple of test boards last weekend - surface mount, single
    sided+ground, couple of square inches each. Took about 1/2 hour for
    the pair of them. In fact most of that was waiting for things to
    happen, so probably 10 minutes actual "labour". It would have taken me
    longer than that to prepare the gerbers and go through the order
    process. Then I would *still* have to wait 2 weeks and pay >$60.

    I would always out-source actual production, and, these days,
    prototypes much more complicated than the above. But I find manual
    production still has a place.
  12. Barry Lennox

    Barry Lennox Guest

    On 16 Dec 2006 09:04:55 -0800, wrote:

    Probably because it's pretty easy to do. I do still make the odd load
    resistor from Nichrome wire, Why? because it's incredibly easy, cheap
    and fast. I could make another resistor in the time taken to fill out
    a web-based order form. It costs me virtually nothing in materials.
    Compare that with waiting 1-2-3 days, the cost of the resistor and
    "Freight and handling ", that jolly convenient excuse to pad your bill
    a little.

    But going back to PCBs, there's a time and place for everything, and I
    don't really understand why there's a problem with that. Occasionally
    I want a new rev of a board this morning, or today at the latest.
    What PCB house can do that ? And while they all produce high quality
    PCBs, I have become a little cynical about their advertising and
    promises about delivery. Things like:

    "Aha, day 1 only counts if you have the design here by 0730, 0800 is
    far too late"

    "Ohh, the UPS man missed us today for some reason, that's not our
    fault that it adds one day"
  13. Guest

    There's a description of exactly such an effort on the last group
    mentioned, with decent results, IIRC. Raster-scan, EDM, zap, zap, zap!

    James Arthur
  14. Guest

    Most printed wiring boards are made by chemical etching or by ECM
    (electro-chemical machining), using an electrolyte that dissolves
    the copper. This is relatively fast, and the 'hazardous' material
    is only the copper itself (the etchants are much more benign than
    the copper is, chemically). Simple etching leaves the copper
    dissolved in the solution, ECM can plate the copper out of the
    solution (good for recycling).

    The etching or ECM works straight from a printed-on resist coating.
    EDM won't. You'll have to raster-scan the board to do the work, just
    like the
    mini-mill machines do. And, we used graphite, copper, or tungsten
    for EDM (they wear down slowest); so we would predict that copper is
    going to be a very slow material to machine with EDM techniques. The
    thermal conductivity makes lots of the heat of the spark dissipate
    of removing material, and the dissipated heat IN THE WORKPIECE will
    be a limit on cutting speed (turn the current up, you burn the board;
    turn it
    down, you cut real slow).

    Some exotic boards are made in porcelain-on-steel, with additive
    copper. You could make a steel/porcelain/steel board that would be
    mechanically stable, and the steel would ECM just fine. Weld on your
    components, and there ya go: ROHS compliant lead-free printed circuits.
  15. Luhan

    Luhan Guest

    I get up at 6am with an idea; prototype by 8:30; board layout by 10:00;
    working unit before noon; have a nice lunch; wonder if Law and Order
    reruns still start at 2pm?

    My workload averages about 10 hours/month lately. So I have more 'free
    time' than 'free money'.

  16. That's easy for the idle rich to say.

    We didn't all inherit billion-dollar estates, and some of us don't even
    have a sugardaddy! Imagine that, if you can.

  17. Ban

    Ban Guest

    You should understand the hobbyist approach.
    Maybe I find an interesting circuit on a website and because I want to use
    these free samples I have already one year, decide to make it. It is just a
    small circuit, some audio preamp for a small electret mike to measure
    frequency response of speakers, a booster for operating white LEDs on a
    single cell, a PWM to drive a small motor, whatever.

    I then order the parts, of course in through-hole, because I can breadboard
    them. Digikey has too high prices and shipping costs. I also have a great
    stock of salvaged parts to reuse, so the order is really small and cheap.
    I do not really trust those simulators and I also do not know so well how
    to operate the prog.
    In the meantime I programm the PIC, and after some trouble because the
    website listing is for the 16F84, I manage to programm it.
    Now all the parts are there and I plug them into the breadboard. The PIC
    still has to be reprogrammed, because I inverted the outputs and some minor
    glitches, but the rest of the hardware works. I will try to tweak a few
    values, seems a bit sensitive to EMC when I move my hand close, but finally
    the board can be made.
    I just paint it with that etch resistant marker on the cleaned copper. The
    etching is done in 15 min. after some setup time of course.
    The drilling is a bit messy, broke that expensive tungsten drill, because it
    was difficult to center and the stand is giving away. But anyway, now the
    soldering iron is already hot. Lets hope that pot has some flexible leads,
    the holes are a bit off...
    But it is all my own work, well maybe not the schematic, but at least the
    board. Have to show it to my GF!
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