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