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  1. #21
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    Quote Originally Posted by Robert R View Post
    Motion Guru has gone off and fixed the problem I guess.
    There is not much in the world of machine building Motion and his crew can't fix.
    It's nice when he throws us a bone as to what he is up to.

    One can do resin bond "porosity" wheels in CBN or diamond and they have a place.
    These wheels have lots of visible "holes" in the working surface. Not the same as a white wheel but not the same flat finish of a standard resin bond.
    Bob

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    “They are used when a mirror surface finish is needed. The goal in this instance is to retain the dull abrasive.”

    Robert has surfaced the fly in the ointment . . . it is a part that in addition to being tight tolerance, has certain aesthetic requirements.

    Marposs system is enroute and I have been working on counting data drops of CAT6 cable in the new building . . . if you told me we would need roughy 150 drops I would have told you were crazy, but it is what it is.

    We will have an update when the hardware shows up and we get it commissioned.

  3. #23
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    Quote Originally Posted by motion guru View Post
    I have been working on counting data drops of CAT6 cable in the new building.
    Off thread but I hope you are using CAT7 or CAT7a rather than CAT6.

  4. #24
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    Quote Originally Posted by motion guru View Post
    it is a part that in addition to being tight tolerance, has certain aesthetic requirements.
    The CBN and the seeded gel ceramic grinding wheels recommended in the earlier posts are used for removing metal quickly and would be poor choices for producing polished surfaces.

    The old school approach for this kind of work is to use a conventional glass bonded aluminum oxide wheel with a coarse dress for grinding the part to size and then do a very slow wheel dress to dull the abrasive for producing the final finish. This approach might have a faster throughput than using a polishing wheel with a coarse dress to act as a grinding wheel.

    On the other hand a grinding wheel will produce large chips. If the filtration system of the grinder coolant or the wash down of the table and parts is less than perfect the polishing step will be damaged by loose abrasive and metal chips. I can see why the resin bonded wheel might be a better choice even if it means a lower throughput.

    The disk drive industry solved this problem a long time ago. The aluminum disks are ground to size with a mirror surface finish.

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    Quote Originally Posted by Robert R View Post
    The disk drive industry solved this problem a long time ago. The aluminum disks are ground to size with a mirror surface finish.
    Those are ground ? That's cool to know. I have seen machines for turning floppy disks - honkin' big blocks of granite, a diamond, and a whole lot of air bearings - so just assumed that hard disks were done the same way.

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    Quote Originally Posted by EmanuelGoldstein View Post
    Those are ground ? That's cool to know. I have seen machines for turning floppy disks - honkin' big blocks of granite, a diamond, and a whole lot of air bearings - so just assumed that hard disks were done the same way.
    I chose a very poor example.

    I should have written that for material removal of less than .005 inches, a surface finish in the range of .05 microns and surface flatness in the range of 0.3 microns, a single side lapping process would be a better choice than a Blanchard grinding process. Reference volume 16 , Machining, ASM metals Handbook page 492., chapter on lapping. The point being that lapping can compete with grinding on a cost basis even when .005 inches of material are being removed and produce surface finishes and accuracy that cannot be obtained by grinding.

    My understanding is that the hard drive disc platters are punched from an annealed aluminum alloy sheet unspooled from a large roll. The blanks are then annealed again while being pressed flat to remove the cold work stress. There may or may not be a double sided lapping process as the next step depending on the depth of the surface defects. There then follows a cleaning-etching-chemical plating process that deposits a non magnetic tightly adhering hard film. The disks are then run through the double sided lapping process again, cleaned. and sent off to the disc drive manufacturers. The disc surfaces may then be textured and finally sputter coated with the magnetic media layers. A top layer of hard film and maybe a lubricant will also be applied.

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  9. #27
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    Ok, Marposs finally received, mounted, commissioned, and calibrated . . . first two batches of parts off the machine gave us the best accuracy and repeatability we have experienced to date with spot checking of parts revealing +/- 0.00015 in of target.

    More testing tomorrow and perhaps we can get this grinder back into useful production before the end of March.

    Major kudos to Frank from Marposs for spending two days with us to ensure everything was as close to perfect as it could be before we ever turned on the spindle.

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  11. #28
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    Quote Originally Posted by motion guru View Post
    Ok, Marposs finally received, mounted, commissioned, and calibrated . . . first two batches of parts off the machine gave us the best accuracy and repeatability we have experienced to date with spot checking of parts revealing +/- 0.00015 in of target.

    More testing tomorrow and perhaps we can get this grinder back into useful production before the end of March.

    Major kudos to Frank from Marposs for spending two days with us to ensure everything was as close to perfect as it could be before we ever turned on the spindle.
    Looks like something we might be interested in.

    Is this system integrated into your control or standalone? How does it address thermal growth?

    Glad to hear it's working out.

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    Good that Marposs seems to have solve problem . .00015 is good IMHO


    Qt:[These wheels have lots of visible "holes" in the working surface. Not the same as a white wheel.... ] old school method to make visible "holes" in vitrified wheels was adding ground walnut shells to the mix before baking the wheels.

    Always wanted to make a highly porous clay wheel of about 220 grit for polish finish SG hard steel work.

    We had a high porous AO 46m we called the Popcorn wheel for SG chuck grinding..Think I used my last one..


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