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IndustryArena Forum > Material Technology > Hard / High Speed Machining > Machine Shop claims they can't mill my part, hardened steel mold die, help!
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  1. #1
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    Machine Shop claims they can't mill my part, hardened steel mold die, help!

    Hello,

    Introduction:

    I am new here, I am an Engineering student, and I am developing a product for a start up company, and have an interest in machining and I do simple conventional stuff myself as well as some diy CNC, nothing complicated though.

    My project:

    I need to modify an existing injection mold die, it is over 10 years old and made outside the U.S. It was originally pre-hardened, EDM machined, and coated with TiN. It is extremely expensive, which is why I would rather modify it than have it remade. I need pockets milled into the mold to accept inserts. The mold die was hardened to accept high volume production, it no longer needs to serve that purpose, I only need it for low volume production. For this reason the TiN can be removed and it really won't matter at all.

    My Problem:

    I have been developing this product for months, and it would be ready to go in about 2 weeks, and all that had to be done was modification of the mold die, I had the machine shop lined up, Purchase order issued. However, when I went to deliver the mold die, they asked if it was hardened (the answer is yes) then they said it would not be possible to machine. It is likely a hardened tool steel (maybe A2, I have no idea since I have no documentation on the mold die) and it is probably around 60 HRC. Does anyone know if it is possible to machine this steel, or is it truly a lost cause? I thought it was possible to machine hardened metals, but I could be wrong? Do I have to turn to EDM? I wanted to avoid EDM due to cost. I would appreciate any advice!

    Thanks!

  2. #2
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    just follow a simple logic..

    grab a simple file.. try to file the surface somewhere of this mold.. if you can leave easily marks and you don't feel """slicky"" the surface then it has chance to milling..

    if file is just sliding forth n back without real effect, then it doesn't worth to mill..
    it is not that machineshop.. it is the reality..

    if file test is failing, file doesn't leaves easily marks then your only chance is the edm..
    but.. even it can be milled, it doesn't mean it will be cheap..


    no matter it is an upcoming company or exist... to producing plastic parts, will not change the price..

    with other words, you can make money only with money... means you have to invest.. just like the energy conserving law.. no free energy, just what you invested..

    you can not go to the machineshop to saying them you read on a public forum yes it can be done.. :-)

    if theres no source even just fix this mold, then don't start it.. you can save serious headache later..


    if it is an injectionmold , then it designed for high volume production..

    setting up an injection mold machine for 20 part not affordable..

    when you say low production, try to make an estimating if part would be 3d printed, or machined of solid plastic.. and.... compare with the price that mold can be fixed..

  3. #3
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    Thanks for your reply, I suppose I will have to begin inquiring about EDM. Also I was curious, the machine shop suggested annealing. It would burn off the TiN, but it should soften the material. Do you have any idea if that would change the dimensions of the mold die, due to thermal fluctuations?

    Thanks!

  4. #4
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    If you don't care how hard it will be then you might try annealing it. This may soften it enough to machine. You can always re-harden it after machining.

  5. #5
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    DREXENG2015

    You can't anneal the mold, without knowing what the material is,(this would also cost a lot to do, or it could trash the mold as well) Wire EDM would be your best if it is all the way through the plate, Ram EDM if you are not going right through, but I doubt that it is to hard to machine, if this is a cavity block then it may be to hard to machine, if it is just the mold plates, that had cores/pockets mounted in it,this will be tough, but will machine
    Mactec54

  6. #6
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    with annealing you loose the polished surface..

    in fact you have 90 percent chance to rework the whole cavity... due geometry changing.. (within annealing)

    means you get very very close in price to making a new part

  7. #7
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    I tried several tests:

    1.) Scraping with steel tool, the TiN came right off, and slight marking of mold die

    2.) Drill Press, I only have cheapie steel drilling bits so I didn't expect much, the bit slid around like a it was on an air hockey table, but slowly left a small indent.

    3.) I have a micro-abrasive sand blaster, I blasted alumina(aluminum oxide) blasting media at 80psi, it quickly made a small hole.

    4.) I used a diamond scribe it easily scratched the mold die.

    I think a carbide end mill would have done considerably better. So maybe it is possible to machine.

  8. #8
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    all of this important the drill bit is wandering on..
    it doesn't says good for you...

    but already something you can say in the machine shop.. a test can show from here if it can be machined..
    hss tool can be machined with carbide.. but it doesn't mean it can be made effectively.. a round hss tool can be turned down carefully, but you cant turn like regular steel..
    same way just because carbide can mill it , it doesn't mean you can mill effectively..

    also if you don't mind on, then you can post a picture and mark where you think the addition.. some folks here makes everyday injection mold, so they can say you more idea..

    they can tell you what can be the lowest cost solution..

  9. #9
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    Much thanks, I have a shop quoting sinker EDM right now, looks like it isn't going to be too bad. For some reason I thought it was magnitudes more expensive than milling.

  10. #10
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    you was thinking right,,
    generally injection molds are expenses.. but on other side some manufacturer gives warranty up to 1 million part molded..
    of course pending on what type part and what type the mold..

    the TIN coating also for longer lifespan for this mold.. so it worth to save that coating..

    ================================================== ================

    let me show you an example.. around 92-93 my relative worked at a company that made small household items..
    they started to make a coffemachine..

    first in house they made the mold.. the blue colored part... it just didn't worked out..
    the design was very ok and was looking it will be long time on market.. so they started to looking for company who could make them..
    French, Italian german and all around in Europe..

    eventually made deal with a Spanish company and the company asked as much as an average worker could earn likely 800 month long... (on hungary I born)

    they also said tool warranted for one million pieces, means they come to place and replace fix anything..

    first the household maker company started to use granulate what was on hand..
    the Spanish toolmaker company said if they don't use a French product they cuts off the warranty..

    you wont believe after about 5-10 test pice the tool worked perfectly using the French granulate..


    so I just showing it you, a mold even looking simple can be more complicated as you think.. so just trust the shop who makes you the fix on the tool...
    that TIN layer might helps the plastic flowing better..

  11. #11
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    Re: Machine Shop claims they can't mill my part, hardened steel mold die, help!

    i know this thread is old but, out of all the machinists here nobody chimed in and said a d2 mold can be machined? I machine hard d2 all day long everyday, and thats at 60-61rc. a2 is even easier.

  12. #12
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    Re: Machine Shop claims they can't mill my part, hardened steel mold die, help!

    Really hard to say with the picture. Are the mold surfaces on a visible part of the end product? If you can live without the TiN coating sinker EDM a hole, wire EDM out a 'peanut' and bolt on a new block for machining. I've never worked with TiN coating but if it flakes a bit and there is a new seam does it matter??? I'm not an expert injection mold maker. Most of my molds are wax investment and everytime we have a chance to make a mold more difficult (aka goof up) I will cut a plug and machine the bad area.

  13. #13
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    Re: Machine Shop claims they can't mill my part, hardened steel mold die, help!

    Hi how many pieces are you Intend to Produce ? I guess for a Start remill the Part in 3 d at a Friends machine or happylab or similar because if your Production is New it is likely that you Need to adjust it ,..


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  14. #14
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    Re: Machine Shop claims they can't mill my part, hardened steel mold die, help!

    Hi,

    You are right, machining was no problem. I ended up getting a Haas mini mill (was cheaper than sending to mold shop as a long term investment), and just machined it myself, (granted there was a substantial learning curve). I called OSG and told them what I wanted to do, and they helped me pick some high helix angle carbide EM's to avoid deflection. Also used shrink fit EM holders, cut through that hard steel effortlessly! When it was all done, I was able to hold tolerances of +/-2.5 microns, or "One Tenth". Good enough for me.

  15. #15
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    Re: Machine Shop claims they can't mill my part, hardened steel mold die, help!

    More that likely it was case hardened only, so once you cut thru the rest should be no problem..Good luck.
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