Makino U86 ovality of holes
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    Default Makino U86 ovality of holes

    Hi,

    I have a problem with my Makino U86 from 2001. Just got it. Wire aligment and guides are checked.

    Machining a 100mm tall toolsteel hole 45mm in diameter. But the hole comes out 0.015 out of round after some skim passes. And a belly(bigger) of 0.01mm in the middle. I expect it to be under 10 microns in straigtness and roundness?

    Backlash problem? does not feel like it.

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    I have now check the backlash and its within 1micron 0.001mm, so thats not the problem. Its bigger between 8 and 2 o'clock

    What roundness do you guys think is "okey" on a 100mm tall piece and 45-50mm round hole?

    I would like to have the roundness within 0.005mm.

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    How are you checking the roundness?
    How many skin cuts are you doing? To get that close Id be looking at Atleast 3 skims on a new sodick to expect better then 0.01

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    Checking with cylinderindicator 3-4 points at diffrent angles.

    One rough, 2 skim with 30 micron step in side compensation, and 3 fine skims

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    Quote Originally Posted by panscan View Post
    Checking with cylinderindicator 3-4 points at diffrent angles.

    One rough, 2 skim with 30 micron step in side compensation, and 3 fine skims
    How are you starting off? Is the hole already roughed in, if so how much stock do you have to cut? Or do you have a small start hole and rough it in and drop a slug, then skim?

    In my opinion your first two passes are key especially in a taller workpiece. How do your conditions hold up when the machine is cutting, are they stable? If your second pass is "Hunting" (large deflections on your voltmeter and ammeter) your either removing to much material or have weak cutting conditions. If that is occurring your remaining passes wont measure up to what you want either.

    Do you notice any wire marks or variations within your finish? These are usually evidence the cutting conditions aren't sufficient.

    To help with the roundness and straightness, although there are many culprits, slow wire speed, low wire tension, and poor flushing can contribute to the issue you are having.

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    Well it was a tool that only needed 1mm bigger in diameter so I did a nocore 3 passes of 75% of the wire. Then left 50microns for first skim and then 30microns to 2skim, and then 3 fine skims just for surface. After that it was out 0.01mm of round. I then tested to run 2nd skim pass again with just 10 microns to remove it goes full speed 2.6mm/min even finish no wire marks. But if i skim in once again on the same comp value I got wire marks and it sparks only now and then, due to to little to remove.

    I measured backlash on xy and uv axis once again they are all within 1 micron. this made me think. So I made same circle in 8mm thick material. And guess what. also out of round 0.01mm.

    Then I made a square 50x50mm Y-axis was 50,0005 and x axis 50,007.. Hmm

    I will change the machine leveling it was installed 2 months ago and weights 12000kg + 2500L of water so close to 14-15 tons so maybe the floor have moved. But weird that xaxis are straight from edge to edge, but 0.007mm to small. Maybe there could be some weird compensation/pitch compensation in the background that fucks with me?

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    Just a thought, if you use the same machine to touch on at north, south, east and west, straight after cutting, does it tell you that its perfectly round? If it says it is then Id agree and say its the machine but if it shows the same error as your indicator then Im leaning more to the cutting conditions and flushing issues.

    If you have the time and material can you make a 45mm dia gauge. With two large flats and see if you can feel the same ovalilty with the gauge? As in does the gauge feel slacker one direction then another?

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    I think that your too picky . . . that's a 19 year old machine, you are expecting a little too much.

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    I hope your not right hehe.

    anyone know if there is some pitch compensation in the machine parameters for makino?

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    Hi panscan:
    In order to find the root cause you will need to approach the error you're finding very systematically or you'll never discover the essence of the problem and any fix you do will just be a bad patch on a leaky boat.

    The first step is to characterize the error thoroughly.
    You say it's out of round...what does that mean EXACTLY.
    Do you have steps at the cardinal points?
    Are the features oval?
    Are the 45 degree points correct?
    Do you have crowning or hourglassing along the height?
    Do you have the same error with small profiles, big profiles square profiles etc etc.

    Some of this you have already done, but it's worthwhile to characterize the errors completely and to map whether they occur all the time or just intermittently and whether they occur all over the table travel or just in spots.

    There will be a pitch compensation table somewhere for each ballscrew, but the trick is to be SURE there are pitch errors before you start jiggering with these tables.

    So map the errors, map the table movements and then report back to us.
    What you tell us will help inform what we tell you.

    In a pinch, you can contact Brian Pfluger from Makino and ask his advice.
    He knows the Makino turf well and has always been a great resource on this forum.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining
    Last edited by implmex; 03-08-2020 at 07:48 PM.

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    The hole was 45mm in diameter and 100mm tall. hole = round hole no other features.

    the hole are 0.01mm tigher in the top 15mm and the bottom 15mm and its 0.01mm bigger in the middle. Measured with a cylinder indicator

    The ovality are 0.015mm.

    Ive tested to make a square on thinner material just to map the movments and its 50.000 in Y-axis and 50.006 in X axis. 8mm thick steel 1 rough and 2 skim passes. Both are straight measuring on 3 points middle and each corner as close as you can with the cylinderindicator.

    yes I just wanted to check the pitch compensation parameters if there are somthing there that should not be. This machine is new for me so I dont know.

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    Panscan,

    Allow me to introduce myself...my name is Brian Pfluger and I work for Makino in the USA.

    I see you are having a circularity issue on your machine, and I believe the bulk of the issue is with your process and not a machine mechanical problem.

    I understand that you are opening up an existing hole by 0.5mm per side, and that you used a Coreless process on the part. This process method is OK, but could you please share what type of Machining Conditions you used on this part?

    In this situation, you should be using the Both Away (Poor Flush) Machining Conditions since you will not fully bury the wire into the work piece. If a Sealed-Off (Good Flush) condition such as Speed was used, the flushing pressure will be too high and it will want to push the wire away from the part causing circularity and straightness (bell-mouth) issues.

    Your particular version of the U86 did not have standard conditions for Coreless Machining, but this can be accomplished using the Both Away settings. You can also review Section 3.7.13 (Workpiece Edge Machining and Coreless Machining) in the Machining Conditions manual for additional techniques for Coreless Machining.

    Have you also reached out to Makino Europe Technical Support (+49 (40) 29809-112) on this issue? Please let me know if there is anything else I can help you with!

    - Brian

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    Hi Brian,

    Exacly no core opening up. I used both away condition. condition 1336 rough, then 1337 two times and then, 1338, 1339, 1340

    But I did go over to a 8mm thick plate just to check. And then I made a 45mm circle in that one with 2041, 2042 and last 2043 still 0.01mm out of round. If I make a square 50x50mm measuring in Y-axis its spoton and X-Axis its 0.005mm to tight. I noticed theres a custom pitch compensation on the set menu, will that reset everytime the machine have been rebooted or can it be some compensation thats transfered from this macro function to the machine parameters? I mean making a aquare you are only moving the axis straight so interpolation error are not into the account.

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    Have you ever heard changing ballscrews and on these makinos? should not be a problem doe to the low force and slow movment. ?
    Do you know how to check the factory backlas compensations in the parameters?

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    Panscan,

    It would be unlikely to see excessive ball screw wear on the U86 machine. Have you repeated your sizing tests on the opposite side of the machine, and do you see the same results?

    I understand that you do not know the history of this machine, but was that machine installed by Makino? I wonder if the machine is installed and leveled correctly, or perhaps all of the pitch comps have been erased somehow?

    I recommend that you contact Makino Europe Technical Support to troubleshoot your machine. It might also be a good idea to have the machine re-lasered too.

    -Brian


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