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    Default doosan lathe troubles

    This is general question about machine and material. I run heat treated material on a Doosan lathe. I am having a lot of problems trying to maintain a tolerance of +/- .009 microns. I know this is a tight tolerance but there seems to be no consistency and I end up with a lot of scrap. Is a Doosan capable of this or should I be looking at a material issue?

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    .009 microns or .009"? If .009 microns or .0003", not a problem depending on the part. I just got done running a job that had a dimension of .3148-.3144 on a diameter over about half an inch. We had very little problems once the machine was warmed up.

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    Quote Originally Posted by jwgray081965 View Post
    This is general question about machine and material. I run heat treated material on a Doosan lathe. I am having a lot of problems trying to maintain a tolerance of +/- .009 microns. I know this is a tight tolerance but there seems to be no consistency and I end up with a lot of scrap. Is a Doosan capable of this or should I be looking at a material issue?

    you havent given a good description. more than likely the problem is your methods of cutting. because of the "NO consistancy" statement.

    for example but not limited too.
    are you using shit junk inserts?
    are you using a rougher and finisher:
    how long is your cut?
    what dia?
    is it a solid part or thin part long part or short part?
    Whats the hardness of the material after heat treat?
    how you holding it chuck with cut jaws? collet, fixture , live center?
    and the list goes on

    Almost can guess its the Methods not the Material or machine unless your machine is a P.O.S.

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    What does heat treated mean? Case hardened? I don't know how big 9 microns is but generally if the machine is in decent condition it ought to hold a half thousands fairly easily so yeah it might be material. It could be something other than both those things?

    Brent

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    Quote Originally Posted by yardbird View Post
    What does heat treated mean? Case hardened? I don't know how big 9 microns is but generally if the machine is in decent condition it ought to hold a half thousands fairly easily so yeah it might be material. It could be something other than both those things?

    Brent
    9 microns is .00035".

    There are a lot of different models of Doosan lathes.

    I have one that is geared between the servo and the ballscrew, using only the motor encoder for feedback. It is a lot more unpredictable than most when starting from cold, but that lathe will still do +/- 9μm without excessive monitoring and adjustment.

    I would assume that most Doosan lathes are at least as good as this one.

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    Quote Originally Posted by jwgray081965 View Post
    This is general question about machine and material. I run heat treated material on a Doosan lathe. I am having a lot of problems trying to maintain a tolerance of +/- .009 microns. I know this is a tight tolerance but there seems to be no consistency and I end up with a lot of scrap. Is a Doosan capable of this or should I be looking at a material issue?
    .009 microns is 0.00000035 in. Good luck with that.

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    Quote Originally Posted by Eric U View Post
    .009 microns is 0.00000035 in. Good luck with that.
    It's Verizon math!
    VerizonMath: Verizon doesn't know Dollars from Cents

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    Model, year and condition of machine might help. Material, tooling, work holding as well, and material stresses.
    I know my 1yr old lynx2100 moves about .001" from cold to running steady, then seems to hold .0001" repeatability in stainless for hours with minor tool wear adjustment. So far its been fairly predictable. But, I haven't crashed it yet, and its still low hours. In a few years who knows, and that would go with pretty well any brand I think.

    Maybe your parts would be better done by grinding?

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    I have a customer with a Doosan lathe that has a 2 to 3 year old machine. they have had issues from the beginning holding +/- .001 on it. they have to run a 3 hr warm up program in a temperature controlled shop to hold .0005 and dont dare let it stop for more than 5 minutes according to him. his old Hardage lathes don't have any issues holding tolarances. not sure what model it is but I'll make a note next time I'm there.

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    Lynx 220LC here............fast and accurate. I'll have a few tenths movement from cold to warm(coolant like bath water)............Holding tenths is no problem.

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    Quote Originally Posted by Hoss710 View Post
    I have a customer with a Doosan lathe that has a 2 to 3 year old machine. they have had issues from the beginning holding +/- .001 on it. they have to run a 3 hr warm up program in a temperature controlled shop to hold .0005 and dont dare let it stop for more than 5 minutes according to him. his old Hardage lathes don't have any issues holding tolarances. not sure what model it is but I'll make a note next time I'm there.
    Anytime a machine isn't holding that sort of tolerance, mostly .001" if its basic 2 axis turning, it should be properly looked over as there's probably somewhere wrong somewhere that needs attention.

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    We are using Sandvik inserts. An expandable collect but no tail stock. I have a 111.048 OD +/- .011 um with a 94 ID at 6.5 length cut one tool rough separate tool to finish. 120.002 OD +/- .011um with same 94 ID at 18 length cut one tool to rough and separate tool to finish. And 54.009 OD +/- .009um with 32 ID at 23 length cut finish tool from 120 OD is the rough and finish here. Print calls for HRC at 36 to 43. Our last batch was at 42 to 45 HRC. This goes through 3 green operations, heat treat, hard mill, then the hard turn is where I have the most trouble.
    So your question about method is very valid. The engineer over this is loaded down with other projects like this. I was an excellent brake press set up tech. Now I have a basic certificate in machining which means I am certified to make a lot of scrap. I have a much better understanding of this part than I did just a few months ago. Now I am the only available expert and now the supervisor. I can run about 6 parts on a finish insert then turn or replace. I back out .070 on x and z and walk it back in. In some cases by the time I am back in I get just a few parts in spec (that vary up and down the tolerance) and I am changing again. I will take any advise on method you can offer.

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    Search for "in process gaging" (or gauging), while it will take some effort to set up and connect the output to the lathe, you'll get the benefit of automatic adjustments to size as the tooling wears, along with the option of alerts for when to change inserts or other aspects of the job.

    If rapid wear of tooling will still limit you on a long production duration part, it may make sense to look for a better machine.

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    Quote Originally Posted by SND View Post
    Anytime a machine isn't holding that sort of tolerance, mostly .001" if its basic 2 axis turning, it should be properly looked over as there's probably somewhere wrong somewhere that needs attention.
    I totally agree !! doosan has been in several times. I have asked the owner if he would like me to take a peek at it . but he is dead set that Doosan has to fix it.

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    Quote Originally Posted by Hoss710 View Post
    I totally agree !! doosan has been in several times. I have asked the owner if he would like me to take a peek at it . but he is dead set that Doosan has to fix it.
    They certainly should.
    Another member here had problems holding size a while back and if I remember right it was X trust bearings that were the problem.

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    Quote Originally Posted by jwgray081965 View Post
    We are using Sandvik inserts. An expandable collect but no tail stock. I have a 111.048 OD +/- .011 um with a 94 ID at 6.5 length cut one tool rough separate tool to finish. 120.002 OD +/- .011um with same 94 ID at 18 length cut one tool to rough and separate tool to finish. And 54.009 OD +/- .009um with 32 ID at 23 length cut finish tool from 120 OD is the rough and finish here. Print calls for HRC at 36 to 43. Our last batch was at 42 to 45 HRC. This goes through 3 green operations, heat treat, hard mill, then the hard turn is where I have the most trouble.
    So your question about method is very valid. The engineer over this is loaded down with other projects like this. I was an excellent brake press set up tech. Now I have a basic certificate in machining which means I am certified to make a lot of scrap. I have a much better understanding of this part than I did just a few months ago. Now I am the only available expert and now the supervisor. I can run about 6 parts on a finish insert then turn or replace. I back out .070 on x and z and walk it back in. In some cases by the time I am back in I get just a few parts in spec (that vary up and down the tolerance) and I am changing again. I will take any advise on method you can offer.
    45Rc is not really "hard turning". Hard enough to make life difficult with carbide, not really hard enough to justify CBN, maybe hard enough that ceramics might be effective.

    Also, the difference between 36Rc and 43Rc is not insignificant. What works for one is not likely to work so well for the other.

    What exact inserts are you using? Geometry, size and grade. Full code basically. Any interrupted cuts? How does the toolpath approach the critical diameter? Does it come up the face and roll around the corner? Rapid to diameter and approach straight on?

    If you roll around the corner then backlash comp can cause a lip/overshoot ripple at the start of the straight cut, usually extremely small, but measurable if you're working in μm. In such cases I often cut backwards, i.e. down the back face to the diameter and then away from the chuck. Similar principle to always approaching from the same direction in the mill.

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    Sounds more like a process problem vs machine problem.

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    Does sounds like a possible gripping and process problem. Could probably use better tooling that lasts longer too, maybe some sort of ceramics.
    And this probably ain't the kind of thing you can just walk away from to sort out other peoples problems then come back later and so on an expect miracles.


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