[slowtwitch]

It was suggested that i start my own thread on the issues I'm having with the mikini mill. So here it is

Let start off by saying that the Mikini is a wonderful machine.. Phil at Mikini does all he can to help you out. But, they really have to stop the blame game and admit that they are having issues. I just received an email from Phil and he was kinda upset. Stating that I am ungrateful for the repairs they did on my boards, at no cost to me.

I would have been glad to have paid for everything, if they would have listened to me from the beginning and repair the boards from the get go. Instead, I was told to buy a motor, sensor ring, get an electrician to check my wiring, buy an EPD, etc etc.

I sent Phil the link of the motor running with the bad bearing. His response was that bearing was good and would last 5000 hours. He also stated the the pulley was damaged when i removed it previously. He also mentioned that my temporary test setup was dangerous and that only qualified personnel should work on the high DC voltages created by the drive. Let me say this, I've rewound small motors and I've rewound very large motors. I've tested motors that ran on 110 volts and I have tested motors that ran on 13k volts. Ground test on 13kv motors required 40 kv of DC..you can smell the ozone being created. So don't tell this old man about testing motors

His email was about a page long and not once did he say, "pete we goofed...sorry" or take responsibility. Everything was my fault...I was chastised about my planned AC/vector drive setup. Everything was my fault...

Anyway, I'm done with playing the blame game, you just can't convince some people. It's time to move on. I like this machine and there are a bunch of folks out there that have them. Hopefully my future posts will be of value to someone and they can repair or improve their mill.

Lastly, I have installed a new bearing on the spindle motor. No ball-peen was used in the installation of the pulley..lol

here's a video...

[ame=http://www.youtube.com/watch?v=2bO22qxczJQ]DSCN3764 - YouTube[/ame]

take care

pete

[howecnc]

It seems to me that the company did not do enough field testing on the machines before they started to sell them. I have had my ups and downs with mine and consider it my second choice to my Tormach.

[GF12]

The specs of the Mikini Machines look very nice, but from all the problems people seem to be having I'm wondering if the machine is a reliable product. Does anyone know how many machines are out there that run routinely without problems? Has Mikini sold more than a hand full of machines which are having the problems, or are there many out there that perform great?

[howecnc]

Mikini does not disclose those numbers, names or any of that information.

[Brian L]

Serial numbers of the machines should give you a clue.... pretty easy to see who's got what number then and get a rough idea on total quantity.

[slowtwitch]

Hello, I haven't really done anything with my mill since Mikini returned my parts. I do start it every day to see if it starts and it still does

A bit off topic, I have been on vacation for the past week and dedicated my time off to learning G code and learning the inner workings of using Mach turn on my EMCO lathe. The average day was about 16 hrs of researching and learning code. On top of that figuring out how Mach 3 works.

I posted a video of the EMCO cutting some aluminum here.....

http://www.cnczone.com/forums/vertic...p_rebuild.html

pete

[aussiedude]

I'm fascinated that i finally find out I'm not the only one having problems with my $12k paperweight.
in the almost 2 years i have had it I have yet to cut a complete part.
Its always been because of "grounding, power issues", (i was originally running it on a very expensive diesel generator) but after changing 3 control boards before one worked and finally having a chance to run it on 220v house power, and not to this day getting the spindle motor to stay at speed and not crash i can honestly say it simply isn't reliable.

[cheetahcnc]

It is interesting that there aren't dozens of positive responses to combat your thread, this may be the answer you seek. I have purchased many machines over the years, some for my employers, some for myself. Very, very few have been trouble free - 100%. I believe a good machine purchase is one that is 90% complete. I have seen over $1 million spent on a system, and it still not be 100%, and I built a system that out performed it for about $250k less. My first personal CNC router purchase cost $16k, and was not able to cut a part, even as the installation tech left with the balance due. It became my hands-on CNC lesson, no instructor included. Classes, if they were available, would have easily cost plenty more than my initial investment. This route, pun intended, was much more challenging and interesting. Plenty of people want to know CNC, they then get their wish - an opportunity to learn it. Believe me, it is a rewarding process. It is good to see you pursue a direction of success, rather than repeat a path of failure. :cheers:

[slowtwitch]

It is good to see you pursue a direction of success, rather than repeat a path of failure. :cheers:

Thanks for the reply My mill is working somewhat since the parts were returned to me. I'm currently investigating a couple spindle options, in preparation for a spindle failure. Which i believe will happen.

Finding a spindle motor was looking kinda of tough, until I saw this....

hossmachine's Channel - YouTube

If you look at Hoss's other video's, you will find one with this motor in action. He does a 1" deep cut with a 1/2" rougher. I can tell you now that my 3 hp spindle will go into alarm doing this.

Another improvement that I will be looking into are the stepper motors and drives. I may want to play and learn about servo motors If I stay with steppers, i will switch to Keling digital stepper drives and motors. I have them on my lathe and they appear to run a lot smoother and quieter. Also with this change will come some type of rpm sensor in the spindle, so that Mach3 can see the actual rpm.

The beauty of all these changes is the knowledge gained by making these upgrades. Everything you need to know can be found on these forums and the web

pete

[SWATH]

Do you thing the spindle motor itself is a problem or the controller board? I agree mine seemed way too eager to go into spindle halt alarm although that could have been due to the spindle RPM dropping. I remember I was doing a conservative cut calculated in Gwizard. While it was cutting it didn't sound bogged down at all and the spindle load meter was barely registering. Then suddenly the spindle just stopped mid cut and the alarm went on, which is an absolute pain in the ass since you have to power down the computer right in the middle of a program then power down the machine just to turn off that blasted sound. In another instance I calculated a cut in Gwizard that required something tiny like .11 HP but the spindle load meter was registering about 50%. I thought that had more to do with the MCU chip on the board fluttering in and out but I was pretty confused as to why the spindle seemed to have no power to make even a conservative cut. I was hoping these were all problems with the board. Sometimes I see videos of the Tormach making a cut and think "that's weird I'm pretty sure that cut on my machine would stall the spindle". What further problems are you experiencing?

Keep us updated on what you do Pete! We need a resident Hossmachine or saunixcomp here on this forum.

[slowtwitch]

[QUOTE=SWATH;1007417]"Do you thing the spindle motor itself is a problem or the controller board?"

I have to say it's the spindle control board, it just can't take the load.


"Sometimes I see videos of the Tormach making a cut and think "that's weird I'm pretty sure that cut on my machine would stall the spindle"".

And the Tormach uses a 1.5HP AC motor with a vector drive.


"What further problems are you experiencing?"

My display panel seems to have a solder joint. It fades in and out at times. I have to give the screen a tap to bring it back on. Sometimes when it fades , it sets off the emergency button in Mach3. Then I have to reset everything, kinda of a pain.

This was the panel that Mikini replaced

Keep us updated on what you do Pete! We need a resident Hossmachine or saunixcomp here on this forum.

I will keep you posted, but, to be put into the same league as those two guys...I don't know. they're kinda like legends

pete

[mcphill]

Sounds like your PC is on machine power? If so, try to sourcs AC to the PC from a constand AC source. I can power down the Mikini and keep the PC onN so I can reset a spindle fault without rebooting the PC. I have only done it once so far, but like you it was during what should have been a weak cut - I think it was a rapid peck drill. I channged it to a standard peck, and it runs OK.

[cheetahcnc]

In another instance I calculated a cut in Gwizard that required something tiny like .11 HP but the spindle load meter was registering about 50%.

Some things to keep in mind with spindle speed, hp, and vfd's. If a 1hp spindle motor is rated for 3600 rpm, and your output speed is geared down (via pulley or gears) 3:1 to 1200, your torque is tripled to 3hp - not taking into account the losses in transmission. This extra hp is usually required when taking slower, heavier cuts. If you take the same 1hp, 3600 rpm motor and reduce it to 1200 rpm via the vfd, the effective output is still 1hp (in a continuous torque vfd - in a variable torque vfd the output hp is actually reduced). If the same 1hp 3600 rpm motor is over-driven 1:2, to 7200rpm via pulleys or gears, the output hp is reduced to 1/2hp. With the vfd the output is a similar reduction, eg. 3600rpm 60hz motor is driven at 120hz to achieve the speed doubling, the horsepower loss is generally linear. This is basic information, as I am not exactly familiar with your current spindle/motor/pulley arrangement. In some direct spindle motors, when you reduce speed, torque is reduced on a linear scale, eg. 1/2 rated speed = 1/2 rated hp.

[SCzEngrgGroup]

Some things to keep in mind with spindle speed, hp, and vfd's. If a 1hp spindle motor is rated for 3600 rpm, and your output speed is geared down (via pulley or gears) 3:1 to 1200, your torque is tripled to 3hp - not taking into account the losses in transmission. This extra hp is usually required when taking slower, heavier cuts. If you take the same 1hp, 3600 rpm motor and reduce it to 1200 rpm via the vfd, the effective output is still 1hp (in a continuous torque vfd - in a variable torque vfd the output hp is actually reduced). If the same 1hp 3600 rpm motor is over-driven 1:2, to 7200rpm via pulleys or gears, the output hp is reduced to 1/2hp. With the vfd the output is a similar reduction, eg. 3600rpm 60hz motor is driven at 120hz to achieve the speed doubling, the horsepower loss is generally linear. This is basic information, as I am not exactly familiar with your current spindle/motor/pulley arrangement. In some direct spindle motors, when you reduce speed, torque is reduced on a linear scale, eg. 1/2 rated speed = 1/2 rated hp.

You're confusing torque and HP. Gearing changes torque and RPM, NOT horsepower.

HP = Torque * RPM / 5252 with Torque measured in Ft-Lbs.

Or, conversely

Torque = HP * 5252 / RPM

Gearing will increase torque, while reducing RPM by the same ratio, or vice-versa, so HP is constant, regardless of the gear ratio.

A 1HP/3600RPM motor will deliver 1.45 Ft-Lbs of torque at 3600 RPM. Gear it down 3:1 and torque is increased to 4.35 Ft-Lbs, while RPM is reduced to 1200 RPM. The output of the reducer is still the same 1HP the motor is putting out. Gear it up 1:3, and torque is reduced to 0.48 Ft-Lbs, while RPM is increased to 10800 RPM. The output of the reducer remains the same 1HP.

Regards,
Ray L.

[cheetahcnc]

I agree horsepower is a function of torque and time. To simplify motor selection, using HP is easier. If you require 1hp for a given cut/task (as many machining functions are given in HP, not torque), and you require 2x the name plate rpm via gears, pulleys, vfd, etc., you need to start with a 2hp motor. This will give you the equivalent of a 1hp motor at the spindle, or 1hp worth of torque at the spindle. Then we could reduce the number more by factoring in diameter of the cutter, as torque/hp ratings are given at the center of the motor shaft. Figure it out any way you like, it would need the bigger motor.

[rowbare]

You are changing the laws of physics.

HP is a function of torque and speed not time. It is a measure of power i.e. how much work can be done in a given time. In our case, it is normally rated in how many cubic inches of metal can be removed in a minute. You can find tables listing the Metal Removal Rate for various metals expressed in cubic inches per minute per HP. A 1 HP 1000 rpm motor will remove as much metal as a 1 HP 5000 rpm motor. However the conditions under which it will do so are different.

Changing speed via mechanical reduction is very different than changing speed with a VFD. When changing speed mechanically, the motor stays at its rated speed and will therefore will put out its rated power (minor mechanical losses aside) at all speeds. The metal removal rate remains the same since the power is the same.

Now using a VFD is a different story. An AC motor under VFD control can be treated as a constant torque device under its rated speed and a constant power device above. Thus if you run a 3450 rpm 1HP motor at 1725 rpm, it will be putting out 1/2 HP. Run it at 4500 rpm and it will put out 1HP albeit at reduced torque. At half speed, it can remove half as much metal as it can at its rated speed or higher.

bob

[cheetahcnc]

...Thus if you run a 3450 rpm 1HP motor at 1725 rpm, it will be putting out 1/2 HP...

bob

This is similar to my original post description, what happened to all your torque specs?

[slowtwitch]

Here's a little update on my mill. I have been having a problem with my front panel. With the machine running and when a load is put on the spindle, the panel would lose all the graphics.

It would still run under manual, but under Mach, it would go into emergency stop at times. I would then have to give the screen a tap and the screen reappears. Then i would have to reset everthing, etc, etc, etc.

This kinda lead me to believe a loose connection of some sorts was the cause. I have rewired the entire machine and installed all new connector ends. These connector ends are polarized, unlike the Mikini ones that are not. I double checked everything and all looked and tested good.

Then I suspected a bad solder connection. I narrowed down the area that I suspected was the culprit. If you ever had the panel off, you have a board where all the connections are made, your parallel port, relay board, drivers, etc. and then there is another board underneath the connection board. I would have to say it's the main board. This was the board giving me problems.

When i removed the top board, i could see right away the some type of repair was attempted. There was a lot of solder paste all over the board. It looked like they attempted to do a "Re flow" repair. Because these boards have surface mounted components (SMD), re-flow soldering is a common repair tactic.

Anyway, they didn't succeed.

I don't really want to deal with Mikini again, so I decided to make an attempt at the repair myself. I searched the web and found a ton of stuff on re-flow soldering, especially hot air soldering. I had some soldering paste from my Megasquirt engine mcu project. I spread it over the solder in an area that i believed to be the problem area (very little is needed). I brought out my industrial strength heat gun and proceeded to heat up the area. I could see the paste begin to react and shortly afterwards stopped heating the area. I admit, i was kinda of nervous about the whole thing...it is kinda of spooky

Once things cooled down, I cleaned up the board and used some "air in a can" to get in every nook and cranny to clean things up.

Now came the moment of truth, hooking everything back up and see if I made a bad decision or not.........


IT WORKED !!!! It's been a week and a half, I have made some deep cuts with repectable feeds, crashed a couple of times stalling the spindle and the screen has not faded out on me yet

Now I just have to learn this g code stuff and stop crashing into things..lol

Oh, one last thing. I'm thinking of starting a new thread not bashing Mikini mills, but, on how can we improve them ourselfs. These are really great machines mechanically, they just need some help in other area's.

One of the things I'm looking into right now, is having the ability of Mach3 seeing the actual rpm from the spindle. I think it's very doable...we'll see


pete

[mcphill]

Enabling RPM feedback is very easy, all it takes is a digital input to MACH3. I added one to my router a while back and plan to do the same on the Mikini. I also have been buying some parts to do either a semi-auto drawbar, or a full auto one (or start semi and go full auto).

Also, I just got a set of Tormach TTS tools, and was disappointed to find out that the surface of the Mikini is too far from the face of the R8 collet (or the camfer of the collet is too shallow - same difference). So I need to add a ship to the face of the Mikini spindle. Not ideal, but not the end of the world. The face of the Mikini is VERY flat and planar to the bed - I was afraid it would not be, but was happily surprised!

Down the road, I will start with a winerack tool holder, and am thinking about upgrading it with the Tormach automatic toolchanger as well.

So many ideas, so little time!

[Brian L]

Not sure if I understand you correctly, but the TTS system requires a modified 3/4" collet, it has to be ground short on the nose so that it doesn't protrude. That way the ring of the TTS holders hit the spindle nose.