Burn isn't straight between different section thickness
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    Default Burn isn't straight between different section thickness

    Hello. I am fairly new to EDM world. I had a class in school several years ago and now took over our shops Mitsubishi DWC-90 EDM after the previous operator retired. We only do a handful of jobs with our EDM so the previous operator was pretty much self taught. We have one job were the thickness of the material changes from 0.125" to approximately 0.045" thickness. The problem I am having is the slot width in the thick part is 0.026" and the width in the thin part is 0.034". Material is Copper

    I was wondering if you guys had any suggestions about how to make the slot straighter. One idea was re-program the contour to cheat the path but I didn't think this was the best route.

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    Quote Originally Posted by wishin4snow View Post
    Hello. I am fairly new to EDM world. I had a class in school several years ago and now took over our shops Mitsubishi DWC-90 EDM after the previous operator retired. We only do a handful of jobs with our EDM so the previous operator was pretty much self taught. We have one job were the thickness of the material changes from 0.125" to approximately 0.045" thickness. The problem I am having is the slot width in the thick part is 0.026" and the width in the thin part is 0.034". Material is Copper

    I was wondering if you guys had any suggestions about how to make the slot straighter. One idea was re-program the contour to cheat the path but I didn't think this was the best route.
    Hey just for some clarity, you have a slot in a part the runs thru .125 thick material that steps down to .045 thickness? And you are seeing a .008 difference in slot width once it gets to the .045 thickness? That's a petty drastic change in size. If I am visualizing this right, I would have to say it sounds like your conditions are a bit hot. How many passes are you taking? I tend to treat copper like aluminum.

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    Sounds like you are visualizing it right. I run one pass down the center to remove the "slug". I then run a pass at the final profile which is like a contouring operation. What would you adjust in the conditions? I might be able to post a picture.

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    Quote Originally Posted by wishin4snow View Post
    Sounds like you are visualizing it right. I run one pass down the center to remove the "slug". I then run a pass at the final profile which is like a contouring operation. What would you adjust in the conditions? I might be able to post a picture.
    I'm not familiar with Mitsubishi wires, but as a wire guy I can give you my opinion.

    Wires can be tricky especially when you are new to the process. There are many factors when cutting with a Wire EDM, submerged or un-submerged machining, type of wire your cutting with, wire tension, wire speed, surface feed, ON and OFF time, flushing and more.

    What size wire are you cutting with? Is .026 the nominal dim.? I would adjust my ON and OFF time, if your ON time is to high although it will cut faster the downside is you can get over burn and wire breaks and less accurate cuts. With your OFF time, not enough OFF time keeps the spark going and less time for flushing. Try taking you ON time down and your OFF time up. It may cut slower but there will be less power to the wire, you want to hear a nice consistent cut.

    Your OFFSETS may need adjusted as well. I would find a piece close to .045 thick and do a test cut and get the wire cutting good and to size for that thickness first. If you can get conditions set from there that would be a good base point to start. The change in thickness can be trouble at times but you should be able to find a middle ground to cut a accurate slot.

    You may also want to consider taking 3-4 passes instead of just 1 down the center and 1 profile. Your first pass should be removing most of the stock with the remaining passes left to skim and clean up the profile.

    Hopefully this can help or get you pointed in the right direction. I'm sure there are other guys here that could be much for help than I. Good Luck

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    Don't know your machine, but .008" difference would be HUGE on charmilles that I ran years ago! I agree with above to add a couple more finish passes. Also, depending on how your machine works, try setting the condition for closer to the smaller thickness (.045-.055 or so). On charmilles, this would make the cutting slower on the thicker portion, but still cut everything to size, within maybe .0005-.001" then needing some final adjustments to get them both within whatever your tolerance is.

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    Thanks Guys. Gives me a few things to try. I'm definitely out of my element with EDM.


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