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IndustryArena Forum > MetalWorking Machines > Mikinimech > So I bought a used Mikini...
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  1. #1
    Join Date
    May 2016
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    316

    So I bought a used Mikini...

    Knowing, more or less, what I was getting in to (thanks to the forum here).

    The price was negotiated down to budget for a complete retrofit. It was, frankly, quite a bit less than what SkyFire would charge to send me a 'bare-bones' no electrical/electronics mill. I bought it knowing it would probably be a project (but secretly hoping not so much). It even came with a 4th axis and a rather extensive collection of Royal quick change tool holders ($$$).

    Everything works so far and I have done some simple engraving, homing, axis moves. Lights and coolant containment have already been addressed.

    But... Spindle motor has the RPM dip mentioned here countless times. Not only does it dip a few hundred RPM, it also shuts off briefly (yellow tower light off) and comes back on while under a very slight load.

    Unfortunate, but not surprising. I've already contacted SWATH to see if he has one of those swanky custom boards to integrate a VFD/Induction motor with the Mikini panel. I'm not interested in spending a lot of time getting frustrated with broken cutters and botched parts before fixing this thing. I'm extremely new at CNC machining and I need to not have a machine fighting me since I'm perfectly capable of breaking things on my own.

    However, before I take the plunge, I'd like to hear some thoughts or advice on various options. Again, SWATH has been helpful and I've already put the question to him about options, but it occurred to me that maybe my first post on CNCZone after lurking forever should be a question for the Mikini folks. Here's how I see it:

    Option 1 - pitch BLDC and driver, fab a mount and install an open-loop 2hp or so 3ph motor & VFD. Manual spindle control outside of Mach3. Not a long-term solution, but would be the fastest route to glory. Upside is that the motor and VFD are unlikely to be pitched if/when I do other mods. Downside, of course, is manual spindle control, so no tapping even with a compression tap holder - I'm not that good.

    Option 2 - SWATH's REX84 board, plus PMDX 106 card, plus vector motor & VFD. More money than #1, but not by much. Upside is I have Mach3 controlling the spindle (open loop) - nice. Downside #1 is that the 106 card appears to be discontinued and don't know if the 107 card (or some alternate) is compatible with SWATH's card. Downside #2 is that if the Mikini panel dies I can't get another one as far as I know, and I'll have to pitch the two cards I bought. Being dependent on the Mikini panel is not ideal.

    Option 3 - Same as #2, but find a motor with encoder, and more expensive VFD. This is, I think, what SWATH has set up and he is perfectly happy with the arrangement. Upside is better spindle control (tapping?) Same downsides as above, plus a giant increase in price for the encoder motor.

    Option 4 - Gut it, more or less. This means pitching some combination, starting with the mikini panel & BOB.
    4a - keep the steppers & drivers, get an ESS & some BOB.
    4b - keep the steppers, replace the drivers, install ESS & BOB
    4c - pitch everything, upgrade to closed-loop steppers. Pull the column and hog out the base so longer motors fit. Yuck.
    4d - pitch everything, get some Nema34 servos. Robodrill rapids!
    4e - same as 4a-4d, but get a servo for the spindle instead of a VFD. I'm right next door to HGR Surplus, so big used servos are dirt cheap. Finding a compatible servo drive may be a bit trickier, but a new encoder vector motor & VFD appear to be quite a bit more than a 2.2kw servo and drive on the surplus market.

    So many questions.

    If I replace the Mikini panel & BOB, what do I go with? Is there a BOB or motion control board that permits me to use either steppers OR servos so I can keep the 4th axis stepper? KFlop? CSMIO?

    I suppose it boils down to money, time & effort. Like everyone, I'm not interested in pursuing an option if it means spending time & money only to pitch parts & start over because something didn't work or the mill sucked when I was done. Or doing a total retrofit with champagne parts and it doesn't really make any difference than if I'd stuck with the stock steppers & drivers.

    Obnoxiously long-winded, sorry; brevity is not my strong suit.

    Comments welcome.

    -Spumco

  2. #2
    Join Date
    Feb 2009
    Posts
    2143

    Re: So I bought a used Mikini...

    Option 5 - Buy a BLDC driver only from Skyfire and replace the one on the Mikini. That's what I did. Unfortunately I haven't installed it yet, so I can't report if it works or not. For now, keep your RPM's at 80% of max or more and you should be fine. If you want to mill steel that can be a problem, but for aluminum, wood, plastic it works fine (the dips in power at that speed don't affect much).
    CAD, CAM, Scanning, Modelling, Machining and more. http://www.mcpii.com/3dservices.html

  3. #3
    Join Date
    Jan 2005
    Posts
    101

    Re: So I bought a used Mikini...

    Option 6 Get a proper cnc controller, drives and servo motors from the one manufacturer. I have a lathe equipped with a GSK controller, servo motors etc. The spindle motor on it is 5.5kW induction motor driven by a vfd. Now that I've seen it, and how it seems to be supplied to the lathe manufacturer with all the cables terminated, I don't think I'd muck about with anything else. It just works out of the box, It is strong and fast, and a bit scary to use when you are just learning like I am. The documentation that came with the controller is very good, and in real english. The lathe is a lot heavier than the mill, but cost the same $, so the controller and servo's can't be all that expensive. If you look at Defeng's latest offerings you will see he is using one of a different brand on the top of the range SVM2. Have a look on Alibaba.

  4. #4
    Join Date
    Feb 2009
    Posts
    2143

    Re: So I bought a used Mikini...

    You could get a whole kit from Flashcut...

    Tabletop & Minimill / Lathe / Gantry Kits | FlashCut CNC
    CAD, CAM, Scanning, Modelling, Machining and more. http://www.mcpii.com/3dservices.html

  5. #5
    Join Date
    May 2016
    Posts
    316

    Re: So I bought a used Mikini...

    Thanks very much for the input - much appreciated.

    As for running the BLDC as-is, it's not just the dips - it's the cutting out and dropping from 5k to 3k while essentially unloaded. Not encouraging.
    I do intend to do steel and other low SFM materials so even if the driver is replaced with a SkyFire, the torque curve (as I understand it) is not favorable for my planned projects. If you had installed yours (mcphill) and reported back that it was the bees knees, I'd maybe give it a shot.

    I found the GSK integrated controller site and it's looks sweet. Thanks for the direction. Same thing for Flashcut, but a complete kit from them with servos is north of 5k - that seems rather a bit much.

    SWATH has reported that the PMDX107 card will work with his kit, so that's encouraging. I think Option 2 & 3 are back on the table since I don't seem to be having troubles with the axis movements.

    I think I'll focus on the spindle for now and address axis components later. If the Mikini panel board dies, worst case I'm out a couple hundred and not TOO much time - and still have a working spindle motor and VFD.

    So maybe my next question is - any CAD files for a 145TC adapter available? Allen appears to have made a one-piece plate and cut the spindle cover. SWATH made a two-piece thing and pitched the cover.

    Do I need to stick with a 145 frame, or will a 182 fit? Other suggestions for a spindle motor?

    Thanks,
    Spumco

  6. #6
    Join Date
    Sep 2009
    Posts
    1856

    Re: So I bought a used Mikini...

    the other option is pokeys
    http://danielscnc.webs.com/

    being disabled is not a hindrance it gives you attitude
    [SIGPIC][/SIGPIC]

  7. #7
    Join Date
    May 2016
    Posts
    316

    Re: So I bought a used Mikini...

    Daniellyall,

    Thanks. Pokeys looks pretty impressive and not too complicated to implement.

    However, I've scored a nice motor with encoder from FleaBay and just bought a flux vector drive. Based on SWATH's suggestions, Option 3 is the path forward for now.

    Once the spindle is happy, I'll be able to better evaluate the motion control. If the axis moves are not up to snuff, I'll start looking at one of the suggestions here for a new controller and or stepper/servos.

    Thanks again to everyone. Wish me luck making the motor adapter.

    -Spumco

  8. #8
    Join Date
    Feb 2009
    Posts
    2143

    Re: So I bought a used Mikini...

    Quote Originally Posted by spumco View Post
    SWATH has reported that the PMDX107 card will work with his kit, so that's encouraging.
    Where is Swath's kit described/shown/sold? Got a link?
    CAD, CAM, Scanning, Modelling, Machining and more. http://www.mcpii.com/3dservices.html

  9. #9
    Join Date
    May 2016
    Posts
    316

    Re: So I bought a used Mikini...

    Via email. He's currently running his 1.0 'interpreter' card. He also has a v2.0 designed, but not built. He's not really selling a drop-in kit, but has discussed the various parts needed (his card, PMDX 106/7 card, VFD, 3ph motor, encoder is optional).

    As I understand it, the mikini encoder/drive work on a 6ppr signal, and the Mikini controller manages the spindle using PWM.

    The new motor and VFD operate at 1024ppr, plus use a 0-10v signal for RPM control.

    The PMDX106 or 107 convert the PWM to 0-10v, and SWATH's card converts the 1024ppm to 6ppm. Both of these are needed to permit the Mikini controller panel to operate & display the spindle properly.

    The difference between 1.0 and 2.0 is that 1.0 uses an axis alarm to trigger spindle halts or estops. The 2.0, I think, would permit Mach3 to see spindle faults directly instead of 'tricking' Mach into a stop. I'm probably missing quite a few details.

    He reports having two 1.0 cards printer but not assembled/soldered up. He has 2.0 designed, but not printed. The 1.0 was quoted at about $80, and the 2.0 he estimated at double that.

    We haven't discussed timing, but since he's busy I expect once we work out details to wait a couple of weeks for him to whip one up. I'll probably be requesting a 2.0 card despite the higher price unless it's going to take him months to get it printed and fabricated.

    Not sure if he monitors this site frequently, but he responded immediately when I emailed him through his War Machine LLC web site.

    Drop him an email. If you're interested in a card all three of us might be better off if we order two or three at once since I may order two just as a backup.

    -Spumco

  10. #10
    Join Date
    May 2016
    Posts
    316

    Re: So I bought a used Mikini...

    UPDATE:

    If anyone's watching this forum, here's the final results of my 7-month Mikini adventure.

    The deal with Swath to cook up a 'translator' board for the VFD fell through; no blame as what I asked for was slightly more complicated than we'd originally discussed. This forced me to essentially gut the Mikini and start from scratch. Here's what I wound up with:

    New PC and monitor mounted on swing-arms
    UCCNC software and a CNCDrive UC400ETH motion controller
    PMDX-126 and 107 spindle board
    Hitachi WJ200-15SF VFD driving a Marathon Black Max 2hp spindle motor
    Motor encoder for tapping (signal to both VFD and BOB)
    All new limit/home switches (12v)
    E-stop and all power circuits are based on 24vdc mechanical relays
    New control panel (all 24vdc - no 110/220 near the operator)
    All wiring inside rigid metallic conduit on back of machine.

    Coolant system hose now external to the enclosure
    2/ea 3" drain holes cut through base to a trough system that dumps in the OEM chip tray

    All wiring removed from enclosure except for X-axis conduit. Drag chain installed for all the crap going to the spindle head (encoder, motor wires, coolant hose, spindle index sensor)

    Lube pump moved to back of base (lower) to eliminate siphoning and the puddles of way oil

    This has been a serious pain, but the mill is now quite happy to make gobs of chips. Like 7000RPM, .125WOC, .375DOC @ 90IPM piles of aluminum chips, plus it can rigid peck tap.

    -Spumco

  11. #11
    Join Date
    Jan 2005
    Posts
    101

    Re: So I bought a used Mikini...

    Thanks for the update, much appreciated.
    John

  12. #12
    Join Date
    Nov 2012
    Posts
    220

    Re: So I bought a used Mikini...

    It would be great to see some pictures of your build and if you don't mind, how much did Skyfire quote you for a machine with no electronics?

  13. #13
    Join Date
    May 2016
    Posts
    316

    Re: So I bought a used Mikini...

    The build is still 'incomplete' as I'm in the middle of making a power drawbar, but here are some photos below. The mill came with a staggeringly expensive set of Royal quick-change tool holders, but I'd eventually like to build an ATC and while the Royals are superb they are not compatible with my ATC plans.

    Drawbar will be a single-stage air cylinder, pushing up on a 1.5:1 lever, which pushes down on an 8:1 hydraulic cylinder attached to the spindle top. The internal hydraulic cylinder shoves down a big ol' stack of bellevilles and releases the Tormach TTS tool holder. I plan on torquing the drawbar to 30ft-lbs - should give about 4500lbs of axial tension on the drawbar/collet so no tool pull-out. Tormach recommends 30ft-lbs, so I figured that would be good enough for me.

    With the enormous spindle motor I didn't have room for a multi-stage air cylinder pushing directly down on the sprung drawbar, so I either needed a massive 4" cylinder with a giant lever running at 100psig and hanging way off the head, or the hydraulic thing. Should make for a fairly compact arrangement. If you're curious about the hydraulic deal, search for the Tormach Lever Operated Drawbar. The 'intensifier unit' is a spindle-mounted hydraulic cylinder with a 5/16" small piston and a 1" (I think) big piston. About an 8:1 or 10:1 ratio, and I'll be experimenting this weekend with how much stroke I need on the small piston to get the drawbar to release reliably. I've calculated I need about .800" to get .100" of drawbar movement - we'll see if that's enough to drop the tool.

    The cylinder is done except for an air bleed, and it seems to work as planned.

    Wiring is a bit messy as I've got the drawbar temp wires back in the enclosure waiting for me to get the solenoid valve and other junk installed.

    If I recall, the quote for a bare-bones Skyfire was going to be north of $10k. There is a US dealer now, so getting hold of them would provide a much more accurate picture than what I can remember.


    Overview

    Attachment 353270

    Inside cleaned up of all the silly conduit

    Attachment 353272

    Coolant collar

    Attachment 353274

    Big-A$$ spindle motor
    Attachment 353276

    New control panel finished yesterday! Woo!
    Attachment 353278

    Monitor & PC out of the way. Hated them on the top of the mill.
    Attachment 353280

    Rearranged the basement for the new drain/coolant system and because there are no electrical bits to get wet now.
    Attachment 353282

    Back of the mill. Liquid-tite conduit because I don't want to cut a wire and to suppress the EMI/RFI from the VFD.
    Attachment 353284

    Closeup of the conduit. Also had to move the lube pump because it would siphon and get oil all over everything inside the enclosure.
    Attachment 353286

    Back of column. Drag chain made things easy since I have oil line, spindle power wires, coolant, encoder, spindle index signal, and (soon) drawbar air lines to get up there without tangling.
    Attachment 353288

    Awesome motor. Dirt cheap on Fleabay, came with an encoder I can sell for twice what I paid for the whole package. Too heavy, but the Z hasn't lost any steps at 100IPM with moderate acceleration.
    Attachment 353290

    220V box down below. VFD, power supply, relays for the coolant and lube pumps. Keeps the electronics from wigging out, especially the spindle encoder and limit switches.
    Attachment 353292

    Inside the 200 box.
    Attachment 353294

    Electronics and 110V stuff. All the safety stuff is run via mechanical relays. E-stop is tied to the VFD alarm, too - not just a 'software' stop. I tried to make this as 'industrial' as I could without blowing money on purpose-built safety relays and controls.
    Attachment 353296

    More of the electronics. Wireway covers are missing, and the wireways are, frankly, too full. Everything is too close together but everything is labeled and easy to trace. Using a CNCDrive 400ETH motion controller and a PMDX 126 BOB with PMDX 107 spindle control board. If I knew 6 months ago what I know now, I'd have gone with the 300ETH and a different BOB, but what I've got is working fine. I just want more inputs.
    Attachment 353298

    Finally, a shot of the extra drain through the base. Much, much nicer - no flooding the base out.
    Click image for larger version. 

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