Noob to edm with hole popper questions
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  1. #1
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    Default Noob to edm with hole popper questions

    Have a situation where we need to make about 8k holes in a hardened part. Due to the nature of the pieces any other process is not going to work.
    Stumbled across edm drilling in a search for solutions.
    Being a completely newbie to the process I have lots of questions.
    How long would electrodes last putting a hole about .100 diameter through a .200 wall thickness. What do quality electrodes cost?
    I assume the exit side of the electrode is close to burr free?
    Does deionized water work well or is it best to purchase a dielectric? Can the dielectric be filtered and reused or is it one and done?
    The part would need multiple holes(it will be fixtured). When starting the process how does the machine start? Do you just hit the go button and it approaches the part and starts the process or is there more to it than that? We would like to be able to have it be as quick as possible.
    Does anyone have estimates on time per hole? From the youtube vids I've seen I'm guessing 45 seconds or so per hole.
    Found a Sodick K1C fairly local but not sure if that would be the best choice of machine.
    Any and all input is welcome.

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    Hi welderboyjk:
    Everything depends on the quality of hole that you need.
    If they must be near perfect, you need a machine like a Makino and they are very pricey but will give you a hole that's accurate to a micron.
    If you don't need a perfect hole, the Sodick will work perfectly well and they are pretty cheap used.
    The Sodick will make a hole that might be accurate to within 50 microns or so for size, cylindricity and location.
    For most things that's plenty good.

    The electrodes are cheap...a few dollars per trode.
    You will consume roughly the same length of electrode as your hole is deep...that can be tweaked a lot, but it's a good rule of thumb to quote from.
    Trodes are about 12" long and so if you use up 0.2" of trode per hole you can get 5 holes per inch that's 60 holes per trode.
    In reality you will probably not get quite that many.
    A gazillion places sell EDM consumables...find one close to you and ask for prices.

    Hole poppers use deionized water, so no need for dielectric oil.
    Most will make their own and monitor its ion content...a few need an external source of water.

    There are all kinds of hole poppers out there, ranging from the very basic like the Sodick K1C to very elaborate fully automated 5 axis models that can load the part, load the trode, locate and do the burns and load the next part, all fully automated lights-out.

    New price for a manual cheapie is about twenty grand...new price for a super model with all the bells and whistles and robot loaders might be as much as 300 grand or more.

    I'd talk to EDM Network in Illinois, they have a fairly broad offering and can get your questions answered in detail.

    Here's a link:
    EDM Network | Drilling EDMs | New EDMs

    Talk to Ron Vogel and let him know Marcus from Implant Mechanix in Canada sent you his way.
    I bought a machine from them in 2011 and they were very good to deal with.

    Cheers

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

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    Marcus, thanks for all the info.
    The hole location and size are not super critical. Sounds like something along the lines of the Sodick will work for us.

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    Quote Originally Posted by implmex View Post
    .
    Hole poppers use deionized water, so no need for dielectric oil.
    I don't know all the lingo around EDM - is a hole popper the same as sinker, i.e. straight down vs a wire?

    just for kicks, here's my diy version....guess its a hole popper lol (no good for 8000 holes, but its saved me on a broken small tap) (power supply/controller by the late Chris Bell)

    Projects - Metallum

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    Hi Mcgyver:
    A hole popper is a specialized sinker EDM that can only make holes.
    It's used a lot for start holes for a wire EDM, also for cooling holes in turbine blades and other weird applications.
    It's very fast...a four inch deep hole 1 mm diameter is done in minutes and it doesn't care if the material is hard so long as it's conductive.

    Very cool technology...if you want to read up on it do a search for "small hole EDM"

    Cheers

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

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    So...


    Hole sizes are not overly important that's good as a holepopper will not be any more repeatable than +/-.001 and the actual size will depend on the electrodes
    which come in standard .1mm increments.
    That also means that for a .100" dia hole you'd use a 2.5mm trode, and depending on material and other conditions you'll get something like a .0995 - .1025 - ish hole size.
    It will repeat to the .001, but it will also have a certain amount of taper.

    I do not know that Sodick model, but for the 2.5mm trode size you want something in the 50A or higher current range.

    DI water vs straight tap water ... mehh... I've tried both and in 20+ years did not find the extra BS involved being worth it.
    You can filter the DI water to sent through the trode, but you better have it damned clean or else it will clog smaller electrodes.
    You can use a separate flush water and "wash" water from separate tanks.
    You can have the flush water ( the one going through the electrode ) as a DI water from a dead clean source and use another tank to wash and cool the workpiece.
    Benefit is that you only need a smaller amount of DI water, but it comes at the cost of not being able to recycle it.
    What I've found working best is that I have a 20 gallon source of clean tap water for the flushing, and a separate 30 gallon tank for washing/cooling.
    No filter at all, just add the flush water as-needed and change the wash water after a certain amount of time.
    Wash water does not affect drill quality or time.

    Use a submerged type fixture if you can! It will help immensely at the break throughs!
    Does not need to be large, does not to be drained and filled at each cycle, just have enough submerge water to compensate for the pressure loss.
    It also helps with the quality of the exit side.

    Trodes come in 300 and 400mm lengths, a 2.5mm dia trode is way strong so might as well use the 400mm ( 16" ) long for less changeovers.
    Trodes are also straight tubes or core-less. Do not even attempt the straight tube for this application.
    Faster drill - Yes.
    Will it suck at breakthrough? YES!!!

    Cycle time at that .2" length should be quite a bit better than 45 seconds, but you WILL need a properly large generator for it.
    Mine is 75A, and at your 2.5mm dia it can drill approx 1.0 - 1.3 IPM depending on material.
    Steel is so so, stainless is nice, AL sucks balls.

    Entry and exit is HIGHLY dependent on your machine's spark control!
    There are a bunch of ways machines can control the spark depending on the scenario!
    Reduced current entry, increased feed for in-cut, reduced feed at breakthrough, variable spindle RPM etc...
    If you have that many holes to drill , DO NOT!!! accept the word of a salesman!
    Do your own test, even if you have to fly out for it!!!

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    The problem you'll have with the Sodick ( and Im a Sodick wire guy ) is its not a CNC control and I'm pretty sure they use oil not water. We have a GF Drill 20. Its CNC machine and uses water.

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    Quote Originally Posted by welderboyjk View Post
    Have a situation where we need to make about 8k holes in a hardened part. Due to the nature of the pieces any other process is not going to work.
    Stumbled across edm drilling in a search for solutions.
    Being a completely newbie to the process I have lots of questions.
    How long would electrodes last putting a hole about .100 diameter through a .200 wall thickness. What do quality electrodes cost?
    I assume the exit side of the electrode is close to burr free?
    Does deionized water work well or is it best to purchase a dielectric? Can the dielectric be filtered and reused or is it one and done?
    The part would need multiple holes(it will be fixtured). When starting the process how does the machine start? Do you just hit the go button and it approaches the part and starts the process or is there more to it than that? We would like to be able to have it be as quick as possible.
    Does anyone have estimates on time per hole? From the youtube vids I've seen I'm guessing 45 seconds or so per hole.
    Found a Sodick K1C fairly local but not sure if that would be the best choice of machine.
    Any and all input is welcome.
    You can make an entire career on EDM hole drilling quite easily, there are 30+Million cooling holes in a modern gas turbine. I'll try to answer your questions in the same order you gave them. There are a few other options you might want to look into, namely laser hole drilling (specifically a laser hole driller not a cutter) and waterjet, although a ō.100 is near the lower limit of waterjet.

    EDM hole drilling is quicker in nickel alloys, but for a ō.100 hole .200" through hardened steel I'd shoot for 20 seconds a hole and try for lower. For a hole that short, if your entry and breakout are normal to the surface I would try a tube rather than a multichannel electrode as you will burn less material and end up spitting out a core on the bottom (think of it as a hole saw vs a drill). Tubes are more consistent from one electrode to the next so you won't be pulling your hair out when the flushing conditions vary from one electrode to the next. As you get further and further away from normal to the surface you will find that a multichannel electrode will work better, but will be slower due to less flush and having to burn the entire hole.

    For your electrode usage I would expect to use .200 of electrode per hole. Calculate the number of electrodes needed by taking the full length of the electrode, subtracting the length of the longest hole (plus ~.100 for run through), and subtract the amount you can't use (in the collet/spindle/guide/gap between guide and spindle/etc). Whatever that ends up being, add a good 20% to CYA.

    If you buy from a reseller expect up to $2 per electrode for tubes and twice that for multichannel. If you buy directly from a manufacturer (try Zayintec in Korea) you will pay half that and get better delivery times for sizes not 'on the shelf'. The EDM companies in North America don't make electrodes, they all buy them, some from 4+ vendors. Some grind electrodes they have purchased. Drawn electrodes will always outperform ground electrodes.

    Deionized water is a dielectric fluid. Any fast hole driller will continuously filter, chill and deionize its own water supply (suspended particles, temperature, and dissolved solids in water all affect the resistivity of the water). The filter removes the suspended particles/dirt, the chiller cools the water and the dissolved solids/ions are removed with the dielectric resin. Using dirty/conductive water causes ECM, not EDM.

    There are a slew of companies that have been built just on EDMing and lasering holes. If it is a 1 off part the larger companies who do 3M+ holes a day won't even look at it, but a smaller shop might.

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    Another thought: If this is a repeat job, and the holes are a consistent pattern, die sinking it with a multi electrode holder can be faster so long as you can get the flush where it is needed. Fast hole drilling is 'fast' (think of a 1mm hole being drilled at 95mm/min in nickel alloy) but typically machines are made to only drill one hole at a time. When you can get 20+ electrodes on a die sinker, the benefits of a rotating electrode with 1000+psi flush pressure tend to go away. With a modern EDM hole driller and an 'easy' part, I couldn't compete with a 1970s hydraulic servo Elox drilling 80 holes at the same time. When all the holes are at significantly different angles, that benefit can't be had on a sinker.

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    Hi pb1:
    I find this really interesting because I have not had the same experience and I wonder what you did differently.
    I found that no matter what I did to improve the flushing, I could never get it good enough to get all the holes burning consistently.
    I've tried flushing drilled directly into the center of each trode and after about ten holes at a time I find some get better flushing pressure in some holes rather than others no matter how I string them together in the manifold.

    Wand flushing hasn't worked at all.

    I can see that if you had a linear motor sinker like a Sodick, you could get by without flushing and just pump the trode, but you've remarked on getting the benefit from a 1970's Elox hydraulic ram sinker, and that blows me away!

    So how are you doing it...I'd LOVE to know if you're willing to share.

    Cheers

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

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    Quote Originally Posted by implmex View Post
    Hi pb1:
    I find this really interesting because I have not had the same experience and I wonder what you did differently.
    I found that no matter what I did to improve the flushing, I could never get it good enough to get all the holes burning consistently.
    I've tried flushing drilled directly into the center of each trode and after about ten holes at a time I find some get better flushing pressure in some holes rather than others no matter how I string them together in the manifold.

    Wand flushing hasn't worked at all.

    I can see that if you had a linear motor sinker like a Sodick, you could get by without flushing and just pump the trode, but you've remarked on getting the benefit from a 1970's Elox hydraulic ram sinker, and that blows me away!

    So how are you doing it...I'd LOVE to know if you're willing to share.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining
    That Elox setup was pretty unique and was setup by the guy who I learned EDM from. The part was ring shaped and all of the holes were about 10 degrees off axis to the Z. That is they were in a cone pattern with relation to the Z axis. The fixture was 2 plates, the bottom one held the part and the end of each guide, and the top part was a few inches above that and held the top of each electrode guide. The guides were surgical steel tubing that slowly coaxed the electrode into position. The top and bottom of the fixture were round and with the guides going from top to bottom it looked like an old round lampshade. The electrode holder was connected to the Z-axis and had a set screw for each electrode to hold them. The holes weren't deep, and it took about 20 minutes to run, which would be very slow going for one hole, but that was for 80 holes. It was cutting very slowly, but made up for it by doing 80 holes at a time. That Elox didn't have flushing per electrode, it just filled the entire tank with oil and circulated it. We tried it on a fast hole driller with 1000psi flush and brass electrodes and couldn't bring it under 15 seconds a hole.

    If I'm remembering it correctly ELOX made some 'single' and 'double' EDM power supplies, the 'doubles' could run 2 machines at a time, or one at double the current. I believe we were using a 'double' attached to one machine. With those machines you never wanted the electrode to back up and pulse like a modern machine might for flushing. You wanted the servo speed to always be outperformed by the cutting, that is, run it dead slow. It was only cutting maybe .015-.020"/min or so, which is glacial.

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    Hi again pb1:
    That is so very very cool!
    There is so much knowledge out there...I don't think anyone could ever learn even a tiny fraction of all there is to know even just in a single domain.
    Thank you for sharing some of it...I really appreciate it!

    Cheers

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

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    Sodick make a 5 axis CNC hole driller that can do auto electrode changes. We just did a job with 1500 holes per workpiece and it performed like an actual Swiss clock. Itís called the K3HN i believe, we have one.

    It uses a additive that you mix like coolant to create a dionized water. We donít know much about the fluid though.

    Contrary to a previous comment. We hole drill aluminium more then anything and it breezes through the stuff with no issue. The only adjustment we make from standard settings is too turn the pressure through the rod down to about 3-4 bar from 8 bar. We think this is because it breaks the particles down further which aids evacuation.

    This week I cut through 200mm brass in 20 minutes with a 2.5 dia rod. Used copper settings and worked a treat, started to cut around 10mm a min first but started to slow a lot as it got deeper. The electrode became less rigid at that depth too so that played a part. None the less, you couldnít drill a hole like that.

    The only serious issues we get is if an electrode becomes slightly bent it starts to tough the hole sides then the machine hesitates.

    And we mostly cut through holes and we always put a sacrificial plate on the bottom of the job. That is a must. It helps with breakthrough as it keeps a back pressure of fluid in the hole upon break through, especially if the electrode is heavily worn or bullet headed.


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