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IndustryArena Forum > MetalWorking Machines > Mikinimech > New upgrades to the ole Mikini. Servos!
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  1. #13
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    Re: New upgrades to the ole Mikini. Servos!

    The spindle + PDB were basically $1k to my door. $90 of that was shipping from china to canada. Another $90 was shipping to my place from canada. Another $130(ish) was customs/duties on both legs. So I ate $200ish because I couldn't get it from the US distributor or directly from Skyfire.

    Again, Marc from the CA distributor was very favorable on the deal - wasn't a 'favor' but he didn't mark everthing up a bunch and gank me on shipping.

    Skyfire, SZGH, and one other vendor are offering 2.2KW AC servo spindle motors which can run on 240VAC 1P. All of them want about $1100 for a motor and drive package - the SZGH are now appearing on eBay.

    I would honestly consider asking for a quote for a spindle and head + PDB assembly and supply your own motor. Eliminating the fabrication of adapters may be worth your time/money.

    Yes, I believe their ATC would bolt on to the column no problem. I think it's $2k and it uses simple interface - not some proprietary modbus programming or connector. It's a basic Geneva drive, but it appears they are in the process of upgrading the tool holder fingers (last instagram post).

    Cliff at Threadexpress youtube channel has a good comparison of spindle taper options - BT30, R8, ISO.

    The BT30 requires more Z-axis travel than TTS but less than an R8 collet. It also requires less spring pressure - the PDB doesn't need to be quite as stout. If you remove the drive keys you can run without spindle homing/indexing for an ATC and I've got certified internet speculation that the drive keys are only necessary over about 3-4HP spindles.

    I think - hope - that with the column stiffening I've mentioned earlier this thing can be a mini-beast. At the very least I need it to be have more reliable tool retention.

  2. #14
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    Re: New upgrades to the ole Mikini. Servos!

    Quote Originally Posted by spumco View Post
    The spindle + PDB were basically $1k to my door. $90 of that was shipping from china to canada. Another $90 was shipping to my place from canada. Another $130(ish) was customs/duties on both legs. So I ate $200ish because I couldn't get it from the US distributor or directly from Skyfire.

    Again, Marc from the CA distributor was very favorable on the deal - wasn't a 'favor' but he didn't mark everthing up a bunch and gank me on shipping.

    Skyfire, SZGH, and one other vendor are offering 2.2KW AC servo spindle motors which can run on 240VAC 1P. All of them want about $1100 for a motor and drive package - the SZGH are now appearing on eBay.

    I would honestly consider asking for a quote for a spindle and head + PDB assembly and supply your own motor. Eliminating the fabrication of adapters may be worth your time/money.

    Yes, I believe their ATC would bolt on to the column no problem. I think it's $2k and it uses simple interface - not some proprietary modbus programming or connector. It's a basic Geneva drive, but it appears they are in the process of upgrading the tool holder fingers (last instagram post).

    Cliff at Threadexpress youtube channel has a good comparison of spindle taper options - BT30, R8, ISO.

    The BT30 requires more Z-axis travel than TTS but less than an R8 collet. It also requires less spring pressure - the PDB doesn't need to be quite as stout. If you remove the drive keys you can run without spindle homing/indexing for an ATC and I've got certified internet speculation that the drive keys are only necessary over about 3-4HP spindles.

    I think - hope - that with the column stiffening I've mentioned earlier this thing can be a mini-beast. At the very least I need it to be have more reliable tool retention.
    Cool, thanks! $1k doesn't seem too bad but yes I would like to see how much a new head would be and if it would just easily replace the Mikini head. I see they have a US distributor, Tripletree. Perhaps they would be helpful. I did watch the Threadexpress videos. It appears my best option is BT30. There is no way I could run TTS without pullout.

    I have a 3hp Automation Direct Dura Pulse VFD running my 80-90lb 2hp Black Max motor. I wonder if the same VFD could run their 2.2kw servo motor for the spindle. I'm leary about any Chinese spindle motor ratings anymore though after the original Mikini debacle. I know mcphil got a spindle servo motor from Skyfire and he said it ended up being even worse than the original Mikini motor. It's hard to believe that is even possible.

    I'm cutting Delrin right now and you could literally cook an egg on the spindle.
    warmachinellc.com

  3. #15
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    Re: New upgrades to the ole Mikini. Servos!

    No, the servo won't run with a VFD - it might turn, but there are only a couple of VFD's on the market advertised as being able to run permanent magnet motors. My Hitachi WJ200 claims to do it, but the best one appears to be the Invertek series. And those are easily as expensive as a dedicated servo amplifier from the motor suppliers.

    My advice, for what it's worth, is to replace the bearings in your spindle now - maybe $500 for some decent but not champagne-level AC bearings. Then keep running your machine while you plan out a spindle upgrade. Sounds like your spindle isn't going to last long enough to get parts together for an upgrade.

    In addition, you can make an aluminum cooling ring for the spindle nose and run flood coolant through it. I have a 3D model of one I made and used until I needed the clearance back.

    Tripletree CNC is the same outfit I tried to contact - thier website is upgraded + new business name, but same address. Maybe they've changed since I tried to engage them.

  4. #16
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    Re: New upgrades to the ole Mikini. Servos!

    Come on Skyfire, I'm getting no response from them...
    warmachinellc.com

  5. #17
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    Re: New upgrades to the ole Mikini. Servos!

    There are other spindle dealers on Aliexpress and Alibaba. Might want to shop around - just be aware that there are different bearing/speed options, as well as cartridge lengths & diameters and bolt patterns.

    Here are a couple:

    https://www.aliexpress.com/item/1705...chweb201603_53

    This one is actually Skyfire's Alibaba storefront.

    https://www.alibaba.com/product-deta...35df3608rswwMr


    And another one. Pay attention to the cartridge length - it's 2" shorter than the Skyfire version which might help with mounting. I think the riser/adapter plate could be omitted in this case, depending on motor shaft length.

    https://www.alibaba.com/product-deta...35df3608rswwMr

    Same place also has an air overy hydraulic PDB:
    https://www.alibaba.com/product-deta...3ef43bf2aSZ0YE

    And finally...

    https://www.alibaba.com/product-deta...69574dd7zTYell

    That looks like an 80mm BT30 spindle. Drop in, no head boring. Multiple speed/bearing options available. I think it's too short, however, but feel free to fiddle around with it in CAD.


    While you're waiting to hear back from Skyfire, here are a couple of images from my latest revision...

    The trick is the relationship between motor shaft, motor pulley, and spindle pulley (duh). Below is modeled with a 15mm HTD belt and a .75" thick riser plate. Pulley is a 48T with JA bushing, and the spindle pulley is a 36T I had Skyfire fabricate for me. Looks like all of the 'standard' spindles from China come with 50T HTD pulleys, so you'll need to determine your motor before fooling around with this. Overdriving a 50T pulley means a monsterous 60T-72T pulley that might not fit inside the housing very well. I suppose you could buy a 2.2kw 10kRPM spindle servo for about $1500...

    This design is the simplest so far as it only requires one adapter. The motor is rigidly mounted to the riser plate adapter, which in turn slides a little bit for belt tension. Means the PDB will be slightly off-center in the relaxed state, but should center up pretty well once the belt is tight.

    The top of the head opening(s) will have to be cut out to clear the belt but the floppy open box syndrome is fixed (mostly) by having the top plate bridge the opening. If it isn't clear from the section view the riser plate is pocketed about .375" deep for the pulley & belt path. I have a nice chunk of 3/4 cold-rolled just waiting to turn in to a bananna on me if I hog it out like this.

    Belt changes require the motor & top plate to be removed, but no fishing the belt around inside a half-closed head. Just slip it on the motor pulley and drop the assembly down over the spindle and snug it up.




  6. #18
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    Re: New upgrades to the ole Mikini. Servos!

    Quote Originally Posted by SWATH View Post
    CI know mcphil got a spindle servo motor from Skyfire
    I missed that comment earlier. Was it really a servo, or was it their BLDC that comes on the low-end model?

  7. #19
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    Re: New upgrades to the ole Mikini. Servos!

    Thanks man, that's great stuff! Skyfire did get back to me, but the delays between communications and the language mis-communications are too much for my patience to handle. I been in contact with Jan Bos and he has been very helpful although I've been waiting on a quote for over a week now. We kind of determined that the Skyfire head was too much trouble to fit to the Mikini and that boring would be the best option. He had actually done the conversion before and said he would never do it again. I contacted DMM about offering a 2.2kw or higher servo and no dice, it's too big for them. For right now I'll be stuck with the Marathon/VFD motor. My best option is still going to be putting in a BT30 spindle cartridge and PDB but maybe skipping the ATC and servo spindle motor until another time. I keep trying to come up with a way to bore the head in place, i.e. somehow mount a motor/boring bar to the table and lower the head down to bore the casting. I'll look into the 80mm catridge though when I get a chance.

    Quick question. Does the Skyfire PDB grip the spindle rotor when depressing the ram or does it just bolt to the casting and push down from there? I ask because I'm wondering if the PDB loads up the bearings every tool change.
    warmachinellc.com

  8. #20
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    Re: New upgrades to the ole Mikini. Servos!

    Quote Originally Posted by spumco View Post
    I missed that comment earlier. Was it really a servo, or was it their BLDC that comes on the low-end model?
    I actually don't know for sure. He just told me he replaced the Mikini spindle motor/drive with the Skyfire and it was worse, so he went the Marathon/VFD route. I made a REX84 conversion card for him to make it seemless with the Mikini front panel.
    warmachinellc.com

  9. #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

  10. #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.

  11. #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.

  12. #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)

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