wire edm speed through thick material.
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  1. #1
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    Default wire edm speed through thick material.

    This may have been covered here somewhere before but here is my question.
    Just for some background I have never run or setup an EDM

    I have a job were I need to cut a 3" diameter hole with 6 keys ways in it through a stack of plates 12" tall. The material is abrasion resistant plate Hardox extreme 65-75RC. The keys are 1/2" half rounds. The accuracy of the bore and keys needs to be +-.003"

    What I'm trying to find out id how fast in Inches per minute a wire EDM can cut through this material wile holding the +-.003" tolerance.

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    Crasher455,

    Is this a part you are trying to make internally, or a part you are having quoted on the outside? I do have a couple more questions to help clarify exactly what you need...

    - What is the start conditions of the part...is there a certain diameter hole that will be in the center of the part?

    - Do you need to Wire EDM the 3.0" ID of the part?

    - Do you have a specific Surface Finish target that you must achieve?

    If you can provide a bit more information on your part, I can help provide a more accurate Cycle Time Estimate, which I need to know the exact perimeter length of the part profile that will be machined by Wire EDM. As for a feedrate at 12.0" thick, your accuracy requirements of +/- 0.003” would be met performing 1 Pass Machining on a Makino U6 HEAT machine, and the feedrate using 0.012" Brass Wire would be in the neighborhood of 0.014" per minute with a Wire Consumption rate of 0.57 lbs. per hour.

    The beauty of Wire EDM will be that all this machining will be performed completely unattended, but this part will have a long cycle time. Is it possible for you to finish Mill or Turn the 3.0” ID before the Wire EDM process? This would reduce the EDM cycle time, as only the Key Way slots would be machined by Wire EDM.

    - Brian

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    I think if I was quoting it I would reduce the stack size to maybe 6 inches tall for improved flushing and probably estimate 7 sq. in./hour over Brian's suggested 10 since I perceive the Hardox to be a little less cleaner than D2 or A2. You also have to be concerned with the part going egg shaped if the wall thickness is too thin. Certain part geometries and materials can stress relieve in funny ways so you might have to stress relief cut. Cutting the keyways only may be an excellent option as well if you can bore the stack, or even maybe faster one at a time that way.

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    Brian and Jmullett both offer good advice and input. The only things I would add are that you do not specify how thick each plate is, and the speed is going to be a rough estimate at best since it depends greatly on what machine and wire one is using. As well, you do not state whether you can accept skim cuts or you wish to finish in one pass.

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    The plates are 1" thick. And the part is a disk 8" outside diameter with teeth on it like a saw blade. The outside is water jet cut and there will be a 1/8" hole 1/4" off the inside edge of the bore to start the wire through. the whole bore with the keys needs to be cut out. knife1.jpg

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    I'd really recommend doing those on a VMC from the waterjet blank. Seems like it would be much cheaper.

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    Redesign the shaft so a waterjet cut keyway or involute? spline can transfer the torque.no need to overcomplicate a trash shredder.

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    With +/-.003" I'd waterjet the whole thing with a high tolerance cut.

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    Inches per minute...more like inches per hour...that's gonna be in the .005-.010 ipm feed, if you can get good flushing.

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    Most wedm cuts are fastest at 2" material thick. For the aggravation and problem of controlling the slugs I think you would be better NOT stacking the plates, and figure about an hour per plate to cut with one pass.

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    Default Drill then bore

    Quote Originally Posted by crasher455 View Post
    The plates are 1" thick. And the part is a disk 8" outside diameter with teeth on it like a saw blade. The outside is water jet cut and there will be a 1/8" hole 1/4" off the inside edge of the bore to start the wire through. the whole bore with the keys needs to be cut out. knife1.jpg
    Late to the party here, but with the half round keys you could drill the 6 holes with solid carbide drill then bore that 3" hole. (Maybe waterjet a 2-1/4" hole in the center.)

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    Hi All:
    Hardox Extreme is a fair bitch to machine; I'm not sure how successful it's going to be trying to drill or bore it.
    It's attractive in principle, but you may find you've got a lot of trashed cutters on the floor and not much in the way of chips.

    So with a waterjet cut blank and a wire EDM you might still end up at lower overall cost than if it were milled.
    I agree you'd be way better off stacking two blanks at the most...you might save a bit of wire stacking them up 12" but you'll do a lot of cursing too.

    Next question; what condition are the flat surfaces going to be in when you load the blanks.
    Just about every wire driver I know will refuse some scabby scaly crap dinging up his super precision table as he tries to clamp the blank down.

    I've never tried, but if it's as wear resistant as claimed, I'll bet it's a cast iron bitch to surface grind on a piddly little surface grinder like mine, so you may need a pre-wirecutting Blanchard grind to get it flat and smooth enough that a wire guy will accept it, especially if it's supplied as hot rolled plate.

    I'd try boring and drilling a bit of scrap to see if I'm full of it or not; and base my decision on the outcome.

    Cheers

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


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