[SWATH]

Yeah I thought it was too, so I began systematically unpowering things on the machine to see if the 12v disappeared. It did not, instead when I disconnected certain things it would add more volts to the ground line. I told Mikini about this and was told that the 12v on the ground is still symptomatic of a high impedance ground line and that should have the ground tested.

[Brian L]

OK, how far is your ground rod from the machine? Take some solid copper wire and run directly from the machine to the ground rod. No chance of a ground loop feedback that way, and no impedance to even consider any longer.

[SWATH]

One of the electricians did something to that effect but didn't take it all the way outside to the ground rod, just to the panel grounding bar. I may try your approach as well. Wire runs 25ft from machine to panel and about 10ft from panel to ground rod so total travel is about 35ft over wire.

[Brian L]

Do it direct to the ground rod. Wouldn't be the first time I've seen issues in a house wiring system. This way you completely eliminate any possible issues with the house wiring... if the problem goes away, then you really have a problem, if not, you can now call Mikini comfortable that it's not possible anything on your end is incorrect.

Wife is a realtor, she had a house for sale, friends of the family, her niece's best friend from high school. The house is maybe 15 years old... while they have it for sale, one day a breaker trips... husband doesn't think much about it, goes outside to flip the breaker back, pow! It trips again..... start looking around, smell smoke... can't figure it out.... finally go in the attic, in a wall up high, maybe 12 foot off the floor in the master bedroom (vaulted ceiling in the bedroom, lowered ceiling over the bathroom), so he could see the vertical wall area and here is a black, burnt and charred section of drywall and the stud looked like it had been almost to the point of burning down the house, all charred black. Turns out a drywall nail came out the side of the stud, grazed into the wiring through the insulation. Now, it had been sitting there for 15 years without an issue and then that day, it would have burnt the house down if he had tried to flip that breaker one more time.....

So a ground coming loose, corroding, becoming isolated, none of it is beyond the realm of possibility.

[pkelecy]

I'm a lurker (hoping for a Mikini someday ) , but thought I would post a comment. Some CNC mills have an internal DC bus that supplies the servos. To produce that, the input AC is rectified and filtered with a bus capacitor. When the machine is first turned on, the capacitor voltage (which is zero initially) looks like a short circuit. So to prevent the current from spiking excessively, a resistor or inductor is normally placed in series with it. Based on the way fuses are blowing on power-up, this current limiting resistor/inductor could be bad (shorted). Just a thought, but might be worth checking out.

Good luck!

Pat

[SWATH]

Ok I got the ground resistance tested today and it is fine, <5ohms@50ft. So the machine is properly hooked up to ground and the ground has low resistance. I'm leaning more toward it being the machine now so I'm going to get an industrial trouble shooter out here to figure out what exactly is adding the 12v and what I need to do to fix it. I tried running a wire directly from the machine to the rod and the spindle was still acting hinky but I was in a hurry so I probably didn't get good connections, I'll try again later tonight.

[SWATH]

After pulling all my hair out trying to get a CNC knowledgeable electrician to try and diagnose it, I spoke with another one today who seemed to know exactly what the problem is. He said he sees this with larger machines that use a DC transformer and suggested I install what he called a "zero tap transformer". I didn't follow entirely but he thought converting AC to DC without this special transformer could cause these problems on single phase power with a residential ground. He is going to look over the block diagram in the manual and let me know what he thinks. Hopefully he can come and look at it, but I gather from all these guys that they are too busy to deal with anyone other than a large machine shop.

[Brian L]

Interesting, but what does Mikini have to say about all of this? Doesn't seem like any of this is on your shoulders, doesn't Phil stand behind his machines?

[ROCKYMTN]

Hmmmm a DC transformer doesn't make sense at all - or at least transformers don't work very well when DC is applied Maybe he meant a center tapped transformer? This way you could generate a good supply with a mid-supply reference ground located right at the machine. Both legs would be balanced at around 115VAC. I could see that as a good test.....

However, I'm still questioning your ground as being a problem as you DID have your machine up and running and have video of it working - right? Did you have the same quirky spindle issues at first power? If the spindle is the only thing still misbehaving, I'd send the controller board in for Phil to look at. At least if would rule that part out.

My controller board died a couple of weeks ago and right before it did, it had very erratic speeds and gave a spindle halt when just moving off the stock that I was cutting. I'm wondering if there is something amiss on your board that could be confusing the controller and causing speed dips.

Board is repaired and is heading back to me. Eager to have machine back running.

Rooting for you !!

[SWATH]

Well the spindle has always had the problem since I first got it. I asked Phil about early on and he said it was just the sound pitch not the rpm dropping and was normal and just electronically shifting gears, so I ignored it. It doesn't do it at the faster speeds as in the video and is not noticeable when cutting wood. The spindle really takes a dip (like 50%) at the lower speeds (below 2000rpm). The speed dips become painfully apparent when cutting metal with spindle halts and tool chipping. That is when I realized that it is actually dropping speed.

[allenj20]

I have had trouble with my spindle since I got the machine in early 09. My spindle has died 3 or 4 times I lost count.

Phil sent me the new V2 electronics at no cost as a result of all the problems I had with the spindle. It's good that Phil stands behind the product but it has been extremely frustrating none the less as you can imagine.

The spindle is definitely the weak point of the design. I think the idea of a brushless linear DC drive is a nice differentiator. But I think it is not as well trodden a path as the AC motor with a VFD. Plus Chinese electronic components are somewhat dodgy to begin with so the more well tested the better I am thinking.

The last time mine died I seriously considered converting it to an AC motor and VFD. If it dies again I will do that I think. Nothing else has given me trouble with the machine the steppers etc... well except the coolant pump recently froze up but that's not a huge deal.

I regret not getting the Tormach or even maybe just building my own from a good Rong-Fu RF-45 (not clone). At least that way I could always order spares off the shelf from a number of suppliers.

Though I would guess this could have happened with a Tormach as well. I am sure there are many people that have had this kind of trouble like this with these Chinese CNC machines. I know there are some in the Novakon forums that have had a lot of frustrations.

Phil has always stood behind the product and always responded professionally to all the issues I just wish there were a few less issues.

[SWATH]

He also mentioned something about a bad speed pot or something. It certainly could be the spindle motor, in fact I may try to completely disconnect the U,V,W wires from the board and see if I still get voltage fluctuations on the board. I don't know if that will tell me anything but it is something I haven't tried yet. I've also been in contact with another very frustrated Mikini owner who has had a lot of spindle problems and replacements as well.

[ROCKYMTN]

I have had trouble with my spindle since I got the machine in early 09. My spindle has died 3 or 4 times I lost count.

Phil sent me the new V2 electronics at no cost as a result of all the problems I had with the spindle. It's good that Phil stands behind the product but it has been extremely frustrating none the less as you can imagine.

The spindle is definitely the weak point of the design. I think the idea of a brushless linear DC drive is a nice differentiator. But I think it is not as well trodden a path as the AC motor with a VFD. Plus Chinese electronic components are somewhat dodgy to begin with so the more well tested the better I am thinking.

The last time mine died I seriously considered converting it to an AC motor and VFD. If it dies again I will do that I think. Nothing else has given me trouble with the machine the steppers etc... well except the coolant pump recently froze up but that's not a huge deal.

I regret not getting the Tormach or even maybe just building my own from a good Rong-Fu RF-45 (not clone). At least that way I could always order spares off the shelf from a number of suppliers.

Though I would guess this could have happened with a Tormach as well. I am sure there are many people that have had this kind of trouble like this with these Chinese CNC machines. I know there are some in the Novakon forums that have had a lot of frustrations.

Phil has always stood behind the product and always responded professionally to all the issues I just wish there were a few less issues.

When you say your spindle died was it the actual motor or the controller boards that went? When mine died, two electrical parts smoked on the spindle driver/controller board - a small cap on the backside plus a resistor on the top. My board is due back tomorrow and I HOPE that fixes the problem. I was hesitant to ship the spindle motor back too as motors are fairly robust...... Keeping fingers crossed......

[allenj20]

When you say your spindle died was it the actual motor or the controller boards that went? When mine died, two electrical parts smoked on the spindle driver/controller board - a small cap on the backside plus a resistor on the top. My board is due back tomorrow and I HOPE that fixes the problem. I was hesitant to ship the spindle motor back too as motors are fairly robust...... Keeping fingers crossed......

Well the motor was replaced at least once maybe twice and I think in every case the Spindle Driver board was replaced. Phil has told me the V2 spindle driver is much more robust and should be more reliable. Curious who here with a busted spindle past or present has the V2 spindle electronics I.E. the 2010 or later design?

I should also mention I never crashed the spindle, abused it, or pushed it hard in any way. My max DOC was 0.020 mostly in 6061 I am very conservative with DOC in general because I am not in a huge hurry and would just as soon not push the capabilities of the machine until I get a good feel for it and know what it can handle. I have basically always babied the 1610L spindle because I am afraid the next time I start the machine the spindle will be dead again.

BTW in the Denver area in case you are too

[ROCKYMTN]

Well the motor was replaced at least once maybe twice and I think in every case the Spindle Driver board was replaced. Phil has told me the V2 spindle driver is much more robust and should be more reliable. Curious who here with a busted spindle past or present has the V2 spindle electronics I.E. the 2010 or later design?

I should also mention I never crashed the spindle, abused it, or pushed it hard in any way. My max DOC was 0.020 mostly in 6061 I am very conservative with DOC in general because I am not in a huge hurry and would just as soon not push the capabilities of the machine until I get a good feel for it and know what it can handle. I have basically always babied the 1610L spindle because I am afraid the next time I start the machine the spindle will be dead again.

BTW in the Denver area in case you are too

Thanks allenj20 for reply back. I definitely have the newer controller as I have a fairly new machine (March of this year). Bummer to hear about yours needing replaced so often and I would certainly feel the same way about swapping out the motor for a AC version. Sounds like they (Mikini) may still have bugs to work out with that spindle hardware/electronics.

I'm also curious if anyone else is experiencing spindle issues....

Yes, close to Denver, Loveland to be exact.

[mcphill]

I have had odd "spindle speed" issues with my machine since new. Phil has said that it is just a "sound" like "shifting gears" electronically, as he told SWATH. I am not sure that is the case, but I also haven't put a tach on it yet to get a real speed feedback.

One odd think I find is that the RPM reported by the Mikini on screen is only about 1/2 the speed requested by Mach at lower speeds. Up around 5000 RPM in Mach3 it reads 4900 on the Mikini, but down around 1000 it reads 500. Anyone else have this as well?

[slowtwitch]

.

I'm also curious if anyone else is experiencing spindle issues....

Sadly, you can put me on that list.

[allenj20]

Sadly, you can put me on that list.

What sorts of problems have you had? And do you have the version 1 or version 2 electronics?

[slowtwitch]

What sorts of problems have you had? And do you have the version 1 or version 2 electronics?

I have version 2 electronics. I'm currently communicating with Phil, in hopes of getting this mill running and don't really want to post my experience...just yet. I will say that when the mill does run, it runs great. Sadly, it only ran on a couple days. in the time that I have owned it.

[allenj20]

I understand and feel for you having gone through the same exact thing. It sucks, hopefully Phil will get you going.

Cheers