Optimum BF30 Mill - Is Spindle Motor AC or DC

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08-15-2012, 07:35 PM
frostheave

3 Attachment(s)

Optimum BF30 Mill - Is Spindle Motor AC or DC

Hi All,

Well, this is my first real post after many years of lurking and learning.
This is such an awesome site! Hopefully in the future I can actually contribute,
but for now here is my question. If anyone has input, I would greatly
appreciate it.

I purchased a new Optimum BF30 and from day 1 the gearbox noise has
really bothered me. I have a video posted here (Turn Up Your Volume):

[ame="http://www.youtube.com/watch?v=tPkAMdzAwuc"]BF30 Gearbox Noise[/ame]

The Optimum Rep I spoke to said the noise is at least partially due to an
inferior motor driver design which causes motor cogging and resonance.
I asked if it would be worth trying a different motor driver and he thought
it would but could not recommend a replacement.

Now to my question. The Rep said the BF30 has a DC motor but I am not
sure he is correct. Below is the wiring diagram and motor nameplate.

http://www.cnczone.com/forums/attach...1&d=1345054171

http://www.cnczone.com/forums/attach...1&d=1345054482

http://www.cnczone.com/forums/attach...1&d=1345054171

It looks to me like this is a 3 phase AC motor, NOT a DC motor. What do
you guys think?

The reason I ask is I would like to get a VFD (If it is a 3 phase AC motor)
and see if that will quiet down the gearbox.

Thanks for your help!
08-15-2012, 07:46 PM
SCzEngrgGroup

The wiring strongly suggests it's a brushless DC motor (no reason to have a Hall Effect sensor on a 3-phase AC motor...). It is definitely NOT a simple DC motor.

Regards,
Ray L.
08-15-2012, 08:16 PM
frostheave

Thanks for the info Ray. After a quick reading at the Baldor Motor website,
I see what you are saying about the Hall devices and a brushless DC motor.

Would you suspect the Hall sensors imply a proprietary design that would not
allow an "off the shelf" replacement? Would it be correct to call this a
"3 phase brushless DC motor"?
08-15-2012, 08:53 PM
SCzEngrgGroup

Quote:

Originally Posted by frostheave

Thanks for the info Ray. After a quick reading at the Baldor Motor website,
I see what you are saying about the Hall devices and a brushless DC motor.

Would you suspect the Hall sensors imply a proprietary design that would not
allow an "off the shelf" replacement? Would it be correct to call this a
"3 phase brushless DC motor"?

Most brushless DC motors are 3-phase motors at heart. And most brushless motor controllers should support Hall sensor feedback. But I would suspect mating, and tuning, a brushless controller and motor may well be a non-trivial under-taking, judging by the number of machines we've all heard about where they work very poorly. I think you'd be better off either sticking with your existing controller, or going to a brushed DC motor and PWM drive or a 3-phase AC motor and VFD.

Regards,
Ray L.
08-15-2012, 09:13 PM
Al_The_Man

Quote:

Originally Posted by frostheave

Would you suspect the Hall sensors imply a proprietary design that would not
allow an "off the shelf" replacement? Would it be correct to call this a
"3 phase brushless DC motor"?

As Ray states the BLDC and AC synchronous are built virtually the same, the main difference is how they are powered, the BLDC, called Brushless DC because only two windings are powered at any given time, equated to a DC brushed turned inside out, as opposed to AC which power 3 windings via 3ph sine wave, both have a P.M. rotor.
Without the advantage of encoder and controller feedback, BLDC can be seen to cog quite a bit at low RPM, I am using a BLDC motor for a spindle but it is under control of a Galil Motion card, so it has a encoder PID loop the same as a servo would, and is very smooth down to zero rpm.
I also agree if you want smoother control down to zero RPM, the DC brushed would be the way to go, there are some Quality Treadmill motors on ebay and also KB and Baldor make both SCR and PWM drives, PWM being the slightly higher priced.
BTW, IIRC that is only a 4 pole motor, whereas 8 pole will give a much smoother operation for BLDC.
Al.
08-15-2012, 10:11 PM
frostheave

Quote:

Originally Posted by HimyKabibble

Most brushless DC motors are 3-phase motors at heart. And most brushless motor controllers should support Hall sensor feedback. But I would suspect mating, and tuning, a brushless controller and motor may well be a non-trivial under-taking, judging by the number of machines we've all heard about where they work very poorly. I think you'd be better off either sticking with your existing controller, or going to a brushed DC motor and PWM drive or a 3-phase AC motor and VFD.

Regards,
Ray L.

Thanks Ray. I will now investigate the brushed DC and 3-phase AC motor possibilities. Sounds like the way to go. Do you suppose inferior performing BLDC motor/controller combinations are used by manufacturers because they are cheaper?
08-15-2012, 10:23 PM
frostheave

Quote:

Originally Posted by Al_The_Man

As Ray states the BLDC and AC synchronous are built virtually the same, the main difference is how they are powered, the BLDC, called Brushless DC because only two windings are powered at any given time, equated to a DC brushed turned inside out, as opposed to AC which power 3 windings via 3ph sine wave, both have a P.M. rotor.
Without the advantage of encoder and controller feedback, BLDC can be seen to cog quite a bit at low RPM, I am using a BLDC motor for a spindle but it is under control of a Galil Motion card, so it has a encoder PID loop the same as a servo would, and is very smooth down to zero rpm.
I also agree if you want smoother control down to zero RPM, the DC brushed would be the way to go, there are some Quality Treadmill motors on ebay and also KB and Baldor make both SCR and PWM drives, PWM being the slightly higher priced.
BTW, IIRC that is only a 4 pole motor, whereas 8 pole will give a much smoother operation for BLDC.
Al.

Thanks for the tutorial Al.
How would I determine if my motor is 4 or 8 pole?
I am curious, why do you recommend brushed DC over 3-phase AC? I am not leaning towards one or the other, just trying to learn.
Any idea how long the brushes last in the treadmill motors?
08-15-2012, 10:59 PM
Al_The_Man

There have been many previous posts from those in the same situation you are in and have converted either to VFD/3ph or DC brushed.
The DC brushed will usually get you better torque down to 0 rpm, unless an encoder option is fitted to the 3ph motor.
Some one sent me one of those motors to analyze so I would have to look up my notes, but I seem to remember 4 pole.
Usually the minimum for a servo, for example is 6 pole.
On a quality T.M. motor I would expect fairly long brush life as T.M. often get a good work out, especially in Gym's.
Al.
08-16-2012, 02:23 AM
frostheave

Quote:

Originally Posted by Al_The_Man

There have been many previous posts from those in the same situation you are in and have converted either to VFD/3ph or DC brushed.
The DC brushed will usually get you better torque down to 0 rpm, unless an encoder option is fitted to the 3ph motor.
Some one sent me one of those motors to analyze so I would have to look up my notes, but I seem to remember 4 pole.
Usually the minimum for a servo, for example is 6 pole.
On a quality T.M. motor I would expect fairly long brush life as T.M. often get a good work out, especially in Gym's.
Al.

Al, what would you consider a quality T.M. motor? Can you recommend any specific brands? There sure is quite a selection on eBay! Should I look for a 3 hp motor like my original? Thanks for your help.
08-16-2012, 03:16 AM
Flexo!

The sound in your video suggests a bad gear mesh rather than a motor problem.

The wierd pulsing @ 600rpm may be down to the motor driver. Could also be caused by poor gear mesh / sloppy gears slipping in and out of alignment.

Pretty common these style machines with gear knobs. The gear has to slide freely up and down the shaft, only held in place by ball detents on the gear knob (not exactly precise).
08-16-2012, 04:11 PM
frostheave

Quote:

Originally Posted by Flexo!

The sound in your video suggests a bad gear mesh rather than a motor problem.

The wierd pulsing @ 600rpm may be down to the motor driver. Could also be caused by poor gear mesh / sloppy gears slipping in and out of alignment.

Pretty common these style machines with gear knobs. The gear has to slide freely up and down the shaft, only held in place by ball detents on the gear knob (not exactly precise).

Yes, Flexo!, there is definitely gear slop that is contributing to the noise. I have had the spindle/gearbox completely torn down and then I put it back together in stages, running the motor at each stage. It stayed very quiet until the last phase when all gears were installed and meshing. The noise also decreases when I put a load on the spindle.

Of course the ultimate answer will be a belt drive and new motor/driver combo. I sure like the looks of the AM2200-H. I guess quality is not cheap!
08-16-2012, 05:18 PM
Al_The_Man

Quote:

Originally Posted by frostheave

Al, what would you consider a quality T.M. motor? Can you recommend any specific brands?

Leeson, Pacific Scientific, Baldor, NordicTrack.
Stay away from the cheap looking pressed metal shell type.
Al.
08-16-2012, 05:36 PM
abfa9358

I have one of these machine and yes the drive train is noisy - belts would be a big improvement as would a spindle capable of say 5K rpm without getting red hot.

Without load my spindle will "hunt" because of the gear lash. On your video something sounds to be not so good mechanically. Also at higher rpm the spindle note is erratic - this sound like a call to the supplier if its a new machine.

Just out of interest have you any means of looking at the voltage coming out of the potentiometer for rpm control? When I got my machine the pot output signal was very noisy and spiked when changing the speed - I fixed it with a higher quality unit from Maplin.

Nice quality 4.7k linear pot is okay.
08-16-2012, 05:55 PM
wizard

Listening to your video seems to indicate multiple problems. There is gear noise to be sure that probably wouldn't be there on a more expensive machine. Some of that noise could very well be the motor and the lack of a good match between the motor and controller.

The noise going away under load could indicate that the slop is being taken up by the load but do realize that loading effects how the controller drives the motor.

I see you have gotten many suggestions to install a brushed DC motor. They generally aren't a bad idea unless you are looking for higher speeds out of your spindle. For the most part brushed DC motors aren't high speed devices. For a home shop they do last a long time if properly sized and not overloaded.

However considering the mix of noises here I'm not convinced that a motor swap should be your first course of action. Frankly I'd consider a belt drive second with leaving it alone the first choice. If you just can't tolerate the noise do a belt drive upgrade. Frankly I wonder why the manufactures of these machines even bother with gears. A quiet long lasting gear train requires more precision than these manufactures seem to be willing to invest in. Note though when doing a belt drive up grade choose a newer technology than V belts which have their own noise issues. Poly V is one belt to consider.

Another option is to upgrade to a 3phase motor with a variable frequency drive. If the speed range is acceptable for the work you expect to do, this route can be fairly cheap. The thing with speed range is that the cheaper motor/drive combos are not extremely stable at lower speeds and more importantly you can run into motor heating issues as the fans are not effective at lower speeds. of course if you spend more most of these problems go away.

The last option would be a full blown servo drive, most user don't have a need for this solution.
08-16-2012, 06:10 PM
SCzEngrgGroup

"For the most part brushed DC motors aren't high speed devices." - Say what? The commonly used treadmill motors are typically 6000 RPM motors. Most would consider that to be "high-speed" on a machine like this.

Regards,
Ray L.
08-17-2012, 05:46 AM
frostheave

Quote:

Originally Posted by Al_The_Man

Leeson, Pacific Scientific, Baldor, NordicTrack.
Stay away from the cheap looking pressed metal shell type.
Al.

Makes sense. Thanks Al.
08-17-2012, 06:09 AM
frostheave

1 Attachment(s)

Quote:

Originally Posted by abfa9358

I have one of these machine and yes the drive train is noisy - belts would be a big improvement as would a spindle capable of say 5K rpm without getting red hot.

Without load my spindle will "hunt" because of the gear lash. On your video something sounds to be not so good mechanically. Also at higher rpm the spindle note is erratic - this sound like a call to the supplier if its a new machine.

Just out of interest have you any means of looking at the voltage coming out of the potentiometer for rpm control? When I got my machine the pot output signal was very noisy and spiked when changing the speed - I fixed it with a higher quality unit from Maplin.

Nice quality 4.7k linear pot is okay.

Yes, the machine is new. I have talked to the Optimum Rep and was basically told the noise is to be expected. It is due to the manufacture of the gears, i.e. not the highest tolerances, and "not the best" design of the motor driver. He thinks with continued use it should quiet down.

The other problem I had was the motor would shut down after 10-15 minutes for no apparent reason. I finally found that the green wire to the hall effect sensors was grounding out to the motor spindle. I fixed that with a soldering iron and heat shrink.

http://www.cnczone.com/forums/attach...1&d=1345179695

To the Optimum Reps credit, he did send me a nice Palmgren 10" Rotary Table for free.

I'll get out the Fluke and check the pot output. Thanks for the tip.
08-17-2012, 06:24 AM
frostheave

Quote:

Originally Posted by wizard

Listening to your video seems to indicate multiple problems. There is gear noise to be sure that probably wouldn't be there on a more expensive machine. Some of that noise could very well be the motor and the lack of a good match between the motor and controller.

The noise going away under load could indicate that the slop is being taken up by the load but do realize that loading effects how the controller drives the motor.

I see you have gotten many suggestions to install a brushed DC motor. They generally aren't a bad idea unless you are looking for higher speeds out of your spindle. For the most part brushed DC motors aren't high speed devices. For a home shop they do last a long time if properly sized and not overloaded.

However considering the mix of noises here I'm not convinced that a motor swap should be your first course of action. Frankly I'd consider a belt drive second with leaving it alone the first choice. If you just can't tolerate the noise do a belt drive upgrade. Frankly I wonder why the manufactures of these machines even bother with gears. A quiet long lasting gear train requires more precision than these manufactures seem to be willing to invest in. Note though when doing a belt drive up grade choose a newer technology than V belts which have their own noise issues. Poly V is one belt to consider.

Another option is to upgrade to a 3phase motor with a variable frequency drive. If the speed range is acceptable for the work you expect to do, this route can be fairly cheap. The thing with speed range is that the cheaper motor/drive combos are not extremely stable at lower speeds and more importantly you can run into motor heating issues as the fans are not effective at lower speeds. of course if you spend more most of these problems go away.

The last option would be a full blown servo drive, most user don't have a need for this solution.

Thanks for your suggestions wizard. Your diagnosis is basically the same as the Optimum Reps, loose gear train and less than "Optimum" motor driver. I do like the looks of the Poly-V belts. I'll definitely check them out closely if I do a belt upgrade.
11-05-2020, 04:13 AM
Stuartcol

Quote:

Originally Posted by frostheave

Hi All,

Well, this is my first real post after many years of lurking and learning.
This is such an awesome site! Hopefully in the future I can actually contribute,
but for now here is my question. If anyone has input, I would greatly
appreciate it.

I purchased a new Optimum BF30 and from day 1 the gearbox noise has
really bothered me. I have a video posted here (Turn Up Your Volume):

[ame="http://www.youtube.com/watch?v=tPkAMdzAwuc"]BF30 Gearbox Noise[/ame]

The Optimum Rep I spoke to said the noise is at least partially due to an
inferior motor driver design which causes motor cogging and resonance.
I asked if it would be worth trying a different motor driver and he thought
it would but could not recommend a replacement.

Now to my question. The Rep said the BF30 has a DC motor but I am not
sure he is correct. Below is the wiring diagram and motor nameplate.

http://www.cnczone.com/forums/attach...1&d=1345054171

http://www.cnczone.com/forums/attach...1&d=1345054482

http://www.cnczone.com/forums/attach...1&d=1345054171

It looks to me like this is a 3 phase AC motor, NOT a DC motor. What do
you guys think?

The reason I ask is I would like to get a VFD (If it is a 3 phase AC motor)
and see if that will quiet down the gearbox.

Thanks for your help!

Did you ever get an answer to this question, I have the same motor and I am looking at options for speed control via CNC, VFD would be an easy fix