[SWATH]

Hey Mike,
As soon as I get the mill trammed I'm going to bore the pulley out a little more. I already did it once but got it stuck real good about halfway on the shaft. I needed to buy a 12t hydraulic gear puller to get it off. I think the tram being off really affected the bore as it only cuts on one side closest to me no matter how good I center in on it. I should have the shim stock when I get home tonight. Maybe I'll do it then. Once I get the pulley on and verify the belt tension and that no other machining needs to be done then on goes the new motor for good. I have a bunch of video of the process but I'm waiting for a good video editor program to get it uploaded. I also video the tramming procedure. BTW, check your other threads later tonight or tomorrow for a tribute. Also I'm thinking of making numerous circuits once I get everything ironed out to offer for a modest price to other Mikini user wishing to upgrade spindle motors.

Sent from my SCH-I545 using Tapatalk now Free

[millersson]

I started my conversion earlier this year after seeing Allen's results with his conversion. There has been a lot of activity on this thread since I started my project. After numerous delays I'm pleased to have now completed my conversion. Well Maybe not quite complete, but the machine is usable again. You can see it here

millvideo1 004 - YouTube

I want to thank Allen for his inspiration for converting my boat anchor into a usable piece of equipment.

[SWATH]

That's great! What struts did you get? I've been contemplating getting some heavier ones to compensate for the heavier motor but I wasn't finding any that where the same length specs.

Sent from my SCH-I545 using Tapatalk

[Brian L]

I have no idea what length and poundage you need, but this place has them all:

Gas Springs and Dampers | Guden Hinges

They used to have a $50 minimum purchase, not sure if that is still the case....

[allenj20]

Nice work, good to see more people fixing their machines.

[millersson]

Swath,
Both of the springs on my machine were shot. I had to replace the springs. As you saw in the video you'll loose the last inch of travel using the lower limit/home switch position. There is roughly 1/2" stroke remaining on the struts. I ordered the springs from Associated Spring P/N GSNI320060. They are made to order so you don't have something that has been sitting around. Gas springs loose 5 to 10% per year. They recommend mounting the springs with the plunger down to keep the seals lubricated minimizing pressure loss. I also ordered the 10mm zinc ball ends P/N EFPS90 and new ball studs P/N BS1002 and safety clips P/N SC1006.

M

[millersson]

Allen,
I can't thank you enough for inspiring me do the VFD conversion. It took me out of my comfort zone and was educational. The mechanical stuff is no problem. I generally shy away from playing with machine controls because it's not my field. After doing this conversion I'm already thinking about another CNC project.
M

[slowtwitch]

millersson, Great Job !!!!!!! It is great to see another Mikini converted into a usable machine

[SWATH]

I have the motor mounted and running but I've hit some problems and frankly I'm exhausted with problems. One is the that the commanded speed vs actual speed is pretty far off which is chapping my ass. Secondly the motor doesn't really sound smooth anymore. I don't know if it's the bearings or what but it sounds kind of rough. Also there is an annoying vibration present and I'm pretty sure it's because the bore of the pulley is not concentric with the outside so the pulley wobbles as it turns. Finally I keep getting over-voltage errors on decel, even with the breaking resistor and conservative settings.

I'm trying to tackle the speed problem first in mach so hopefully someone on that forum can help. Then I may look at getting another pulley and then perhaps the bearings. Pete, you seem to know a lot about motor bearings what are some good replacement bearings to consider or at least bearing grease. I noticed it sounding rough after I mounted the pulley, the shaft got really hot from the hot pulley, but I tried to keep it cool with a wet rag and compressed air. I'm wondering if the grease has melted out of the bearing. It doesn't sound too bad, but just like a faint scraping feel/sound like it's dry with no lube or something. I might play with the belt tension as well to see if that has anything to do with it. Maybe I'll do a video tomorrow if I have time.

burned out

[SWATH]

Here are some videos of some problems I've uncovered with the motor:
Rough sounding motor - YouTube

The motor sounds rough, rougher than I ever remember it sounding. So I took it apart to find out what was going on.


The drive bearing at least was bad. It didn't feel too rough but after I took off the rotor and was spinning it you could tell it was pretty rough. I'm assuming the top bearing would soon follow.

When I first got the motor I took it apart to make sure the clicking noise I was hearing was not the rotor hitting the stator. It wasn't but I noticed a lot of green grease all over the bearings and in the bearing pockets. I assumed it was just preservative grease or something to help the bearing slip in place because the bearings sounded ok. Now I think it is actually the grease from inside the bearings that has leaked out over time leaving them somewhat dry inside.
Attachment 208658


I'm just going to replace them both with some better ones. These say CHINA stamped on the shield.

They are 6205Z. I just ordered some ABEC-3 double shielded bearings from mcmaster.

[millersson]

That does sound rough. There are a lot of cheap bearings, but you'll need something better. I good bearing to get is ABEC3 grade bearing.
M

[SWATH]

Thanks Millersson, That was exactly what I did. They were $15ea. so no big deal. I got 4 just in case.

[uawgmsmco]

Okay WOW everyone...I'm new to the Mikini name...i literally just discovered it an hour ago. I've built the classic Grizzly Industrial X3 machine for myself, and I thought I've gone through hell to get the bugs out of my setup...this has been intense for you Mikini owners. The machine looks super promising!...but damn, it looks like it's been just that. But I must say, the machine does look sweet. I love the shape of the head and the color is killer too!

[SWATH]

Here is what I was using and what I'm working on now.

Sent from my SCH-I545 using Tapatalk

[SWATH]

Getting the bearings off was pretty straight forward but I had to rig up a way to install them with some threaded rod and couplings. I also opened up a washer to keep the pressure on the inner race.


Sent from my SCH-I545 using Tapatalk

[SWATH]

I'm actually reinstalling the old bearing here just to make sure it would work because the bearings I ordered were actually most likely stolen off my front porch by some degenerate thief.

Sent from my SCH-I545 using Tapatalk

[SWATH]

My apologies for being so absent. I've just had a ridiculous number of problems and set backs lately including a blown vfd due to the braking resistor both of which I had to replace. But here is a sneak preview. A few tweaks maybe tomorrow and hopefully this card will be working. I give you v1.0. A seamless transition from the BLDC motor and drive to a VFD driven AC motor.


Sent from my SCH-I545 using Tapatalk

[mcphill]

Wow, you're going all out! Nice job!

[SWATH]

And the ridiculous number of problems continue. I planned on spending today calibrating the vfds speed output since I got everything working yesterday. But the machine wouldn't turn on today. Turns out the Mikini 12v power supply is dead. So I ordered another 12v today plus a dedicated 5v for my circuit and the smoothstepper. I ended up making a Lexan plate to mount my circuit and the c41 card where the old BLDC driver used to be.

Sent from my SCH-I545 using Tapatalk

[FannBlade]

Man it just never ends for you! I wish someone would offer just an "iron" package with (ballscrews and oil ports) that was CNC ready so we could just add electronics we wanted. No warranty required just give me some true iron.

Hang in there not much more can go wrong.