Cutting Steel Bushings and cast iron
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  1. #1
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    Default Cutting Steel Bushings and cast iron

    Hello all,
    I am trying to cut an 8 inch part of steel bushings with cast iron center section and having A LOT of trouble. All my usual ways of cutting aren't working and I'm getting wire breaking on skim passes even. I have exceeded my knowledge, granted isn't much as I am finding, but after 2 weeks of trying to cut this thing having problems after problems I don't know what to do besides quit my job which isn't an option. It should have been a piece of cake. I started with .008 wire and then switched to .010 and was at least able to do rough cut. But on rough cut I kept getting contact after contact and chipping away at the slug of a 3" diameter hole. It left a bunch of deep lines in the part that are making my skims very hard due to the cut, skip, cut, erratic passes. I altered the EPAC'S per the manual up and down. Has anyone ever had an issue cutting the two metals at the same time?

    Is there anyone in California who has good working knowledge of the proper way to program offsets, conditions, and EPAC'S for EDM willing to train someone? I'm willing to pay, work for free for you for a week, I don't care what it takes at this point, I NEED TO LEARN THIS RIGHT! Not the get you by training I had. There is nothing more frustrating then not being able to learn how to do your job right or better.

    2 and a half weeks is too long on one part and I'm desperate. Sorry if I sound crazy I just want to do a good job and take pride in what I do but have hit a wall so I am coming to you all.

    Thanks,
    e

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  3. #2
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    Take a pic of your current epac

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    I am uploading pictures to show my situation with the part at hand. I noted the problem area as far as dimensional. Where the lines are there is .005 extra material measuring across and from other angle it is .005 over sized. The pass is cutting all the way around but wont bring that section into spec. How is that possible and how do I correct it?
    part-ang1-section-b.jpg
    part-ang1-section-.jpg
    Any thoughts?

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    epac-info.jpg
    this is what it is set to now that I was able to skim with out wire breaking. I think the IP should be at 3 and the AE at 11. Is that right? But will that bring the one part into size with the section that is larger? I dont see how it will cut all the way around yet not concentric.

    What am I missing with this????

    Thank you so much for responding to my desperate call for help!

    Tvalen1432

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    Wow that's a old one... Jack your voltage gap (vv) way up, and make sure your flushing is as high as it can go. Also bring your federate d
    Down.

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    The feed rate was only upon exit. I had it at .14 during the cut. LOL. Sorry. With the skim EPAC ending in 3 the flushing is not an adjustable setting at the meters. It's basically off in a sense. Besides, wouldn't that cause vibration in the wire? and or cause breaking in itself like a thin work piece? Or should I be using a different EPAC ending in 1 where flushing is on? If so how far should I offset the cut so I don't go way beyond my final dimension?

    Using an IP4 setting with the AE at 21 and then increasing the VG in only that section or for the whole circle of burn? The VG is the burn side to side correct? Cutting more into part depending on feed rate the amount cutting correct?

    I could PM my number if it makes it easier to explain if that is an option?
    My other question is that since there is a void of material to cut at that section, could there be given less cut power to there then the rest of the circle that has full material top to bottom? Also, can I change say the VG in the middle of a cut either by hand or in program to increase it only in that section?

    Thanks

    P.S. yes this is an old Mitsubishi FXK 20
    Last edited by tvalenzuela1432; 01-29-2020 at 05:49 PM.

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    To be honest I sometimes use a strong epac that I made for rough and finish. When your in variable mode and adaptive control (if you have ac on the machine) there are only a few epac settings that can be adjusted. Turn them off and you can edit all the pera.eters and then turn them back on. If you are having contact issues and you don't have adaptive control id slow your feed to .01 and creep up until you start getting contact then back it off a bit. The biggest thing in a tall cut is flushing.

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    So should even a 2nd, 3rd, cut if not cutting into the part only skimming, have full flushing? Have you ever had an issue where in the rough cut left those lines and then have a problem getting that part to size with the rest?
    Have you ever cut a part where there is only material on top and bottom with a large gap in middle and been able to get them the same size? That gap affects and gives less power to the bottom portion of part doesn't it?

    Is there a way to compensate for that?

    Sorry for all the questions. I just want to understand whats going on so I can come up with a way to conquer it. I will figure it out I'm sure. LOL

    Thanks,
    Tvalen1432

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    That rough patch in the middle of your part, where the lines are above and below. That looks painted, is it not painted? If it is painted could it be pushing the wire away from the material?

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    It's just DYKEM. So I can see what exactly is getting cut. Reaction is the same with or without it on there. The patch that looks painted is the part that is cast material and is rough like pavement kind of. It is lack of material in the casting.

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    Ok, but is dykem conductive?

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    Quote Originally Posted by nlancaster View Post
    Ok, but is dykem conductive?
    Wire edm will go through dykem. If the material is porous or has inclusions it can cause the wire to skip or deflect, especially if it's non conductive.

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    Hi tvalenzuela:
    Do I understand correctly that you are cutting the cast iron part of this iron/steel assembly?
    I ask, because the only times I have had the sort of problems you're describing, was when I was cutting cast iron, and the problem turned out to be non-conductive inclusions in the CI.

    Not for love or money could I get that fucking lump to cut decently, and I was tearing my hair out trying to get it to work, thinking I must have taken my "extra stupid pill" today.

    Now, I've seen lots of posts of yours on here before; you're an intelligent and knowledgeable guy regarding wire EDM so I don't think it's you...I'm going to bet it's the material.
    If you have offcuts, have them inspected for inclusions if you can.
    Also, just for fun, prove to yourself that it's not the machine by making a test cut in a piece of Durabar or even mild steel that's roughly the same height.
    If that test cut goes well it ain't the machine either!

    Cheers

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

    On edit: Hey plastikdreams...you beat me to it...that's two votes for inclusions in the material!
    MC

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    You should edit your program to focus on that area that is +.005" stock and just offset your program until you can get it to size. Unless it's pushing off the CI in which case it's never going to happen.


    How hard are the steel bushings just curious why the part can't be done with a boring head on a cnc.

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    Marcus,
    Thank you for the compliment. For the record... I am a female but my name is deceiving and has got me an interview or two since they thought I was a man. LOL. I was about to chalk it up to that I let the rough cut struggle over and over to get through and bounce a bit causing the lines as why it was out. But I'll be damned if the thing wouldn't cut right. No mater how high of and Epac or low, bring my offset in and out and only cut that section that had extra material, it would barely cut anything if not break my wire. Yes the cast was very porous and old. The maker chose to put the bushings top and bottom I think because it was only way to stabilize and maintain size accuracy. After all, it housed the spindle and col-let holder of a router I believe. So for sake of sanity I'm going with you all on the material SUCKING! LOL. So nice to hear some one else has gone through that.

    Update: After almost 3 weeks of this fun my boss finally handed it to the CNC mill. (could of done that 1 1?2 weeks ago but hey) On to my next adventure.

    Thank you sooo much for everyone's input. I love this FORUM!

    Toni Valenzuela
    Mold Shop EDM

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    Hi Toni:
    You wrote: "For the record... I am a female"

    Yeah, but to all of us you're one of the guys too and it's a pleasure to have you participating.
    So I assume that you are a tool and die breaker building injection molds...what kind of molds does your shop build?
    Are you running the wire exclusively or do you get to play on all the cool toys?

    Cheers

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

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    COOL! Yes it is me exclusively running the EDM. I have experience on CNC mills and Lathes and a lot more toys. We only make molds for my company. No production thank God. LOL. To sum it up we make plastic containers for strawberries, candy, containers for Chick-Filet(spelt that wrong oops), the green baskets for strawberries and more. We have another paper division too here making boxes etc. but I only deal with the metal stuff like punches, dies and so on. We help out Cal Polly students with their racing parts too which is cool too. Anyways, I broke down the machine for a cleaning and found proof to back up the material theory and found something the cast left me. I'm adding a picture of my lower power feeder. LMAO! And to think Thursday it almost came to a quit or be fired stand off sort of thing. DUMB Cast.
    power-feeder-cast-iron.jpg

    Glad I know when to shut up because I like my job.
    Thanks again,
    Tvalen1432

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    Wire edm can be a challenge, I cut porous tantalum for a few years even with 12 wire the speeds were very low. Adaptive control was a necessity as the wire never had a full engagement across the entire cut. Turn it off and the wire would break almost instantly. These were fairly small parts and they took a good bit of time each. Now one of my jobs is to cut super alloy castings for testing. If I hit an inclusion all hell breaks loose.

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    If milling was acceptable why was it ever put on a wire to begin with?

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    I believe he felt EDM was going to be more of an accurate fit top and bottom. But I can't answer for my boss. I just do what I'm told to the best of my ability. But then again how was he to know we would have such a hard time. We usually deal with mostly aluminum and D2 steel but this was a side project.

    Thanks again for all the input and guidance. Priceless!

    Tvalen1432


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