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  1. #1
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    Default Copper discussion.

    Hi,

    I am looking for advice on what type of copper is best for spark erosion. I see 3 types that are commonly used which are. Pure, sulphur and tellurium copper, plus more technical ones like tungsten copper and stuff...

    I know itís an ambiguous question. They all have their own benefits. But who uses what type and why?

    All opinions and facts will be appreciated!

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    for most general use use hdhc copper. graphite easy to machine but messy. easy cut copper less deburring but seems to wear more. tungsten copper allows a bit more power to go in as harder wearing

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    Default Copper for EDM

    Hi Luke,

    There are several choices of copper for EDM electrodes:

    Electrolytic Copper or Oxygen-Free or Oxygen-Free Electronic (OFE) is used throughout electronics (C10100) and it undergoes electrolysis in a final refinement to reach 99.99% purity. This method produces copper with less than .001% oxygen Ė more for improving metal purity than conductivity.

    Tellurium Copper (TeCu) has 0.5% Te added for machinability. During cooling, the Te precipitates throughout the copper matrix and allows for much better chip-forming and breaking. The machinability rating for pure copper is only 20% vs. 85% for TeCu.

    Copper Tungsten (WCu) is not an alloy but is a sintered product with very-fine tungsten particles suspended within a copper matrix. The tungsten is present to reduce electrode wear and is available in grades from W50-50 to W90-10. EDM suppliers usually stock electrode blanks with a tungsten content of 70% and higher.

    Silver Tungsten (WAg) is available for its higher-conductivity but is seldom used because of expense.

    Hope this helps.

    Bud

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    Hi,

    Okay great, I have two questions,

    Is this oxygen free copper anything like HDHC copper?

    And Iíve read about tellurium copper which is one type of free machining copper. What does it wear like in EDM? People often talk about free machining copper and itís higher wear but they never specify which type of Free machining copper they are using.

    Thank you for your detailed answer.

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    Hi Extem,

    What tools do you use to cut HDHC copper? Do you use indexable tip tools with specific copper tips for turning and what about milling cutters?

    Iíbe only used HDHC in my previous toolroom with no problem but my current fellow toolmakers are adamant that HDHC copper is too difficult to machine which I just canít seem to understand? I mean yer itís not easy but itís not that difficult.

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    Hi Luke:
    Here is my take on copper and its uses in EDM:
    There are two principal reasons to use it; one is to avoid the mess of cutting graphite and the second is in certain small, low power burns where super fine surface finishes are needed.

    If you are doing any volume of burning, the benefits of graphite are hard to overstate, and the things needed to solve the messiness problem are worth doing.
    Better wear, better electrode stability, better burn speed...the list goes on.

    But for the occasional use like mine, there's a benefit to copper that makes it worth while to accept its limitations, and many shops like mine with a sinker in the corner have made the same calculation with the same result.

    The arguments for and against Telco versus C101:
    I have come across them before and I checked them out for my own satisfaction years ago. (to the best of my knowledge HDHC copper is C101 but hard drawn)
    In my opinion, C101 can be profiled and surfaced without too much pain, but as soon as it comes to drilling flushing holes that are tiny, the difficulties grow alarmingly and it becomes a non-starter because of the unacceptable loss rate of trodes due to drill breakage.
    I have not found a process control plan that reduces that risk acceptably; no magic tools, no magic coolant, no magic speeds and feeds, but I confess I didn't try all that hard either.

    Telco by contrast is drop dead easy to drill; even small diameter, deep holes are a doddle.
    Other benefits are that Telco does not raise the same number or size of burrs and is easier to finish mill to an acceptable standard (but is shitty to turn to a nice finish).
    Telco can also be surface and cylindrical ground more easily then C101 and I find it easier to polish as well.

    So if you are serious about your EDM efficiency you will use graphite and reserve your copper use for very specific applications.
    If you can stomach the cost of POCO Angstrofine graphite for the fine detailed high precision burns with fine finish requirements, the need for copper will be almost non-existent.
    You can also use POCO C3 (copper impregnated graphite) if you can stand the taste of it when it permeates the air and makes you feel ill. (at least it does me)

    If you are an occasional EDM jockey, you can pick your poison depending on whether you plan to drill flushing holes or not.
    If you have a linear motor sinker, you rarely drill them anyway.
    If you have a ball screw sinker or a hydraulic ram sinker, you may drill quite a few flushing holes and in that case I would choose Telco.
    I found not enough difference in EDM performance to justify the pain of C101, even though the pain was not all THAT much more (except for flushing holes).
    The performance differences are not discernable to me... if you want to do noticeably better with your EDM process, graphite is the proper choice, not some marginally better grade of copper.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining
    Last edited by implmex; 03-23-2019 at 11:57 AM.

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    The details that are actually able to be cut in graphite nowadays is pretty amazing. 30k spindles, lightning quick cutting feeds. Rib details under 0.010" thick no problem..... Not to mention the finishes the newer edm machines can achieve with these mid to high grade graphite. Hard to imagine anyone wanting to use another material.

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    Hi,

    Thanks for all your input, everyone Iíve spoken to all gives the same answers which is great. My only trouble is that we are banned from using graphite as we share the same space with the mould shop and it contaminates their production. Thatís why this is hard as Iíve got make the best use out of the best copper without increasing our cost of buying copper.

    I was hoping if someone could give me the factual reason why free cutting coppers create more wear then HDHC copper?

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    Hi again Luke:
    The proper question to ask is: if I run Telco instead of HDHC copper will I have to make more electrodes to burn to the same level of detail and fidelity?
    For me, and the kinds of burns I do, the answer was "No"

    In addition, the Telco is cheaper for me to buy here in Canada than the C101; about a third less expensive.
    So for me it was a "no brainer".
    I'm fully satisfied with my choice and I have no complaints at all.

    With regard to your question about the reason Telco wears a bit more then C101; I have not the faintest idea!
    I believe the difference for a typical finishing electrode is trivial...maybe a few tenths at the corners.
    I certainly could not measure it when I did my comparison.

    Cheers

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

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    Default

    With graphite the cheaper stuff isn't as dense. So it's literally softer. Which in turn wears faster. Perhaps same idea with your copper. With that being said the cheaper softer graphite cuts easier and diamond tooling lasts longer... it's a tit for tat sometimes......

    Implex says it best that the wear differences most likely could be minimal anyhow. So take the cheaper and easier material to machine for your electrodes.

    You could also grab a sample of each and machine them and burn them and get your exact answer yourself in a few hours....

    Good luck.

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    Running EDMs and "banned" from using graphite!!?? Shut her down, go home, consume massive beers!


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