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IndustryArena Forum > MetalWorking Machines > Mikinimech > New upgrades to the ole Mikini. Servos!
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  1. #21
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    Re: New upgrades to the ole Mikini. Servos!

    Also Jan shared with me the the 3D files for the different Skyfire head castings. The Mikini casting is pretty much identical to the larger Skyfire SVM-2 head casting with respect to the shape and spindle bore (140mm wide head) but the linear bearing block bolt holes are different and the ball screw bearing is different and is a giant pain to make work on the Mikini he says. Boring is the best way to go. If I can somehow figure out a way to mount a boring tool to the table I may be able to open the 80mm bore to 90mm as well as drill/tap the new bolt hole pattern for the BT30 flange.
    warmachinellc.com

  2. #22
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    Re: New upgrades to the ole Mikini. Servos!

    Quote Originally Posted by SWATH View Post
    Also Jan shared with me the the 3D files for the different Skyfire head castings. The Mikini casting is pretty much identical to the larger Skyfire SVM-2 head casting with respect to the shape and spindle bore (140mm wide head) but the linear bearing block bolt holes are different and the ball screw bearing is different and is a giant pain to make work on the Mikini he says. Boring is the best way to go. If I can somehow figure out a way to mount a boring tool to the table I may be able to open the 80mm bore to 90mm as well as drill/tap the new bolt hole pattern for the BT30 flange.
    Post or PM me those files please. Would be VERY helpful.

    The skyfire PDB just pushes on the drawbar end. Remember that the belleville stack is significantly weaker on a BT30 than is requierd on a TTS system. much longer stroke required (I think about 4-5mm vs. .050") to release, but less spring pressure.

    Honestly, the way to do the head bore without a big lathe or mill is to just grind it out in place by hand or use a jig saw. You only need 5mm width of cut, and just sneak up on it until the spindle just slips inside.

    Step 2 is to clean the paint off the mounting surface and stone it flat.
    Step 3 is to drill & tap the new mounting holes. Make yourself a steel bushing on your mill (before you get started!) and use that as a drill & tap guide.
    Step 4 is to coat the spindle OD and flange with mold release or wax. And then do it again. And do the same for the mounting screws and threaded holes.
    Step 5 is to grout the spindle in place with steel-filled epoxy. Set the spindle in a vise or fixture to hold it upright, coat the bore with epoxy and then lower it down on the head. Snug, but don't torque the mounting bolts. User a tongue depresser or whatever to get the gap completely filled and then run a 90mm O-ring down the spindle on the inside to kind of squish any epoxy back down in the annular gap - sort of like a valve packing follower.

    Once the epoxy has set but not completely cured, tappy-tap-tap the spindle out and clean up any residue. Deburr any epoxy flashing.

    You now have a better fit than would ever be achieved by boring - prefect transfer of spindle side loads to the head casting.

    In fact, this is what I'm going to do after it's bored to a close fit - I'll grout it in with epoxy.

    I've seen this done on big machines for precision surfaces, and also there are some good Youtube videos on it. I've tried it on a few things (my 4th axis frame plates for one) and am now a total convert to using epoxy to achieve good fits. Everything feel so much more rigid.

    If you're paranoid about getting the spindle back out, then before you do it for real hit it with mold release or wax and the dribble a blob of your epoxy on it and try to pop the blob off once set. If it doesn't come off easily, try more release or wax.

    And if the spindle gets stuck in there, finish the project and use the PDB to shove it out once it's mounted.

  3. #23
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    Re: New upgrades to the ole Mikini. Servos!

    BTW, Ebay has decent deal on servo/drives if you're looking for a replacement for the BlackMax.

    Just look for something in the 90-130mm frame size, and look for LONG servos. They usually aren't titled very well, but it's amazing how fast you can scan for motor plates and find something in the 220-300V range. Check for max speed, and amps. You'll get an idea of what's available in the sub-$200 range and then go hunting for a drive.

    The drive is the tricky part, as there aren't many with 240V 1P inputs and high amps on the used market. The Parker Gemini series appears to be about the highest one I could find - the GV12 or H20 are the ticket, and unlike some of the other drive mfgrs Parker's user manual is pretty friendly for non-OEM installations. Good luck with a Fanuc manual.

    Find a drive before settling on a motor, and see if the user manual is still available. Don't buy anything way old - getting a replacement shouldn't be a major chore.

  4. #24
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    Re: New upgrades to the ole Mikini. Servos!

    Those models were extremely helpful. You were right - there are some significant height differences/upgrades Skyfire did post-Mikini era.

    One look and I realized one of the Mikini shortcomings in the head is the lack of upper spindle support. All the loads are transferred through the bottom face where the spindle is mounted, whereas the Skyfire has a mid flange for spindle support.

    My spindle model was also a bit off from theirs, so I re-did a few things and added an upper spindle support plate. The plate OD will have to be made undersize to fit the rough head casting ID surface, but I can mount the spindle and then use epoxy to grout it in place. Side bolts will put the epoxy in compression, and the unsupported back surface should be OK as the side bolts will be in shear.

    I could, theoretically, make it longer to add support further back, but I think my steel motor plate should be enough once it's tightened down.

    REV4 (or so)

  5. #25
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    Re: New upgrades to the ole Mikini. Servos!

    Excellent work!

    For reference here is the BT30 spindle in the SVM-2 head. The pink drawings are my 2hp Black Max motor.
    Attachment 425532
    Attachment 425534

    Hmm, the SVM-2 head is looking more attractive now if I could just get it to fit on the linear guides and the ballscrew bearing.
    warmachinellc.com

  6. #26
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    Re: New upgrades to the ole Mikini. Servos!

    Yep, that BlackMax looks painfully familiar.

    To be honest, I think it'll be less work to make a top plate and a spindle reinforcing collar thing than fitting a new head. And if I ever switch motors it'll be pretty easy to redrill or make a new top plate - or even a sub-plate.

    If it goes poorly, I'll just get some plate and weld/bolt up a new head with the dimensions & features I want. I'm not spending a pantload more on this thing - if I want an ATC or 5th axis, I'll have to find time to make it myself.

  7. #27
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    Re: New upgrades to the ole Mikini. Servos!

    Here are the Mikini head specs directly from Skyfire:

    Attachment 425642
    Attachment 425644
    Attachment 425646

    Here are some measurements from the 3D model of the Skyfire SVM-2 head:

    Attachment 425648
    Attachment 425650

    As you can see they are almost identical.
    warmachinellc.com

  8. #28
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    Re: New upgrades to the ole Mikini. Servos!

    Yep, they're close. Did Jan explain why it was such a PITA to swap heads?

    And do you have any other Mikini drawings?

    EDIT - you're right, they are about identical. I don't see why it wouldn't bolt up. And I don't see why the bearing blocks and ball screw wouldn't bolt up - center to centers and the nut flange circle are the same. The ballscrew nut might need a shim sleeve, but that's stupid easy on a lathe.

    Thinking discount on a 2-pack from China?

  9. #29
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    Re: New upgrades to the ole Mikini. Servos!

    Quote Originally Posted by spumco View Post
    Yep, they're close. Did Jan explain why it was such a PITA to swap heads?

    And do you have any other Mikini drawings?
    No those are all the drawings I have. He said that the bore for the ball screw bearing was 1mm off and he needed to make some kind of spacer. He couldn't route the oil lines in the head and had to run them on the outside. Also it took forever to get it back in tram. Curiously he said the center center distance between the rails on his machine was 120mm. I measured and mine is 128mm just like the drawing. Some column castings don't have a way to access the linear bearing guide bolts from the back. Mine does, as did his, but like his mine are very small and probably need to be drilled out.

    Defeng tells me that the SVM-2 uses larger ballscrews and larger linear ways, however from what I can tell at least the ball screws are the same (2005). The linear ways are similar sized but are a different type (RGW25 type).
    warmachinellc.com

  10. #30
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    Re: New upgrades to the ole Mikini. Servos!

    Thanks for the details. I think I'm back to the adapter plates.

    I've got a plasma table control system to build first, but once that's done I'm going to start tearing the old Turdkini apart.

  11. #31
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    Re: New upgrades to the ole Mikini. Servos!

    Here are the finished way cover extentions

    X
    Attachment 427866
    Attachment 427868
    Attachment 427870

    Y
    Attachment 427872
    Attachment 427874

    Z drip deflector
    Attachment 427876
    Click image for larger version. 

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ID:	427878
    Click image for larger version. 

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ID:	427880
    warmachinellc.com

  12. #32
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    Re: New upgrades to the ole Mikini. Servos!

    NICE! Thanks for the servo cover details, that will help when I get to that point.

    Just starting on my control panel for the upgrade. Motion controller and buttons will be remote from the 240VAC stuff - I have some analog FRO/SRO pots I want to keep away from the noisy drives.

    Intention is to build a mostly stand-alone electrical/control package I can test on the bench without taking the mill out of service for an extended period.


  13. #33
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    Re: New upgrades to the ole Mikini. Servos!

    Interestingly the inside of my head casting is nothing like the diagrams shown here. I took the bottom coolant plate cover off to replace a broken coolant hose and looked up in there with a flashlight and mirror. The entire front of the casting is nearly solid iron surrounding the spindle cartridge not a empty box as the diagrams show. It goes all the way up to the pulley so the cartridge in completely encased in cast iron. I'll snap pics at some point but right now I'm pretty solid on keeping the existing casting and just boring it out to 90mm.
    warmachinellc.com

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