Controlling Fanuc AC Servos

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aefriot

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I am still trying to wrap my head around what is needed for this CNC work and I do not want to waste money buying items I do not need. I do not have access to machines that I can look at and learn the process of cnc.

I am looking at buying some Fanuc servos. They were from a welding robot. I have to assume there are controllers for making the servos do their work, but they are not part of the lot.

Fanuc A06B-0371-B075 a1/3000 AC Servo Motor 90 V 0.3 kW
Fanuc A06B-0371-B175 a1/3000 AC Servo Motor 90 V 0.3 kW
Fanuc A06B-0123-B175 a3/3000 AC Servo Motor 127 V 0.9 kW
Fanuc A06B-0162-B075 aM6/3000 AC Servo Motor 144 V 1.4 kW

There are three different voltages so I believe there must be a way to change mains to the required voltage. Either individual transformers or a single transformer with multiple taps. There were a couple 3.0 KVA transformers in the lot. There are motors and there is a way to get the proper voltage at the proper power.

What's missing, is the way to control the motors. Do the controllers have to be specific Fanuc controllers? Or can they be of any manufacturer as long as they can provide the proper voltage and power?

Also, there must be a way of coordinating the controller timing, right? Is this the computer or is it a intermediary device that interprets what the computer is telling the cnc system?
 
I believe AC servos require specific controllers (I.E. Fanuc) and are less common than DC servos
Jim D knows more about it than me
I would not invest in hardware before knowing a lot more about the various systems out there
You don't want to buy boat anchors
 
Yes some motors may be run by drives of another brand but don't buy anything until you know more.
One thing the robot servo motors are not the same as machine tool servo motors, they don't have the same torque or service duty to output the same torque.
Yes this is commonly known by people doing retro fits.
Early pre digital servo drives can be controlled by a simple DC signal but you need a motion control card to output that signal based on feedback.
A 3D printer is a great tool / toy to learn cnc basics.
There are some cnc systems being sold that use a PC along with some interface cards , they are one of the easier ways to build a cnc in reasonable time and effort.
It is packaged with basic software and such.
 
There was a time when what was meant by "servo" was a DC motor, with tachometer output generator on the shaft for speed feedback, and possibly synchros for positional feedback. With the coming of optical encoders, stepper motors, permanent magnet multipole AC drives, and now, AC drives with current phase sensing for traditional AC induction motors, the choices have expanded enormously.

+1 on @sdelivery 's advice about don't buy until you know more. Let us get some terms right. One can get "controllers". Then another bunch of more powerful electronics known as "drives", usually with local controller buttons and tiny number displays added, but normally connected to the CNC control computer. You might be running some software, like "Mach4" , or "LinuxCNC".

Then you get the motors. These can be more applied to servo work when they have built-in shaft encoders, and logic pulses interface. That bit of kit can sometimes become a brand lock-in, to an extent. Motors generally have no choice but to be motors, and one can usually add one's own encoders, with some work. you need not be forced to purchase the whole ensemble.

For CNC, where the motors that move stuff on slides can often be geared down, or toothed belt driven, and it works a ball-screw anyway, stepper motors can be used. A raw opn loop stepper is not good. For CNC, you need the type with feedback drives. These are noisier than true servos, but are about a third of the price, which is why they are so widely used.

If your CNC includes real-time control of the main spindle, then the drive is a fatter thing, only needing speed control feedback, and has to be rated to the full torque of the machine. It needs to be of the type under servo control that can deliver that full torque, even at very low speed, or stopped, or even while being driven backwards while actually spinning forwards (i.e.decelerating to controlled stop under inertia).

I would think the motors you have listed could be driven by almost any good servo drive, unless they have proprietary design to ensure lock-in. There has to be the setup where you enter the number of poles, and other motor characteristics, so your system can get going. The connectors for such things can be relatively expensive, but if they came from a previous build, then getting hold of the cables and connectors is a huge plus. One has to study, and know the exact form of feedback signals, to ensure there is compatibility. Fortunately, there is lots of standardization in the industry, and even if incompatible, it is usually possible to adapt.
 
Last edited:
aefriot said:
I am still trying to wrap my head around what is needed for this CNC work and I do not want to waste money buying items I do not need. I do not have access to machines that I can look at and learn the process of cnc.

I am looking at buying some Fanuc servos. They were from a welding robot. I have to assume there are controllers for making the servos do their work, but they are not part of the lot.

Fanuc A06B-0371-B075 a1/3000 AC Servo Motor 90 V 0.3 kW
Fanuc A06B-0371-B175 a1/3000 AC Servo Motor 90 V 0.3 kW
Fanuc A06B-0123-B175 a3/3000 AC Servo Motor 127 V 0.9 kW
Fanuc A06B-0162-B075 aM6/3000 AC Servo Motor 144 V 1.4 kW

There are three different voltages so I believe there must be a way to change mains to the required voltage. Either individual transformers or a single transformer with multiple taps. There were a couple 3.0 KVA transformers in the lot. There are motors and there is a way to get the proper voltage at the proper power.

What's missing, is the way to control the motors. Do the controllers have to be specific Fanuc controllers? Or can they be of any manufacturer as long as they can provide the proper voltage and power?

Also, there must be a way of coordinating the controller timing, right? Is this the computer or is it a intermediary device that interprets what the computer is telling the cnc system?
Click to expand...


The short answer is a resounding NO. Don't buy them. They require a Fanuc controller and drives to run. It's the most convoluted system I have ever seen. They work great when you have all of the Fanuc hardware and controller, but to try to use them in a retrofit or a new build is virtually impossible.

Yes, there is a way of controlling the timing. There are many motion controllers available. Normally the system would look something like this

1676404224019.png
 
sdelivery said:
Yes some motors may be run by drives of another brand but don't buy anything until you know more.
One thing the robot servo motors are not the same as machine tool servo motors, they don't have the same torque or service duty to output the same torque.
Yes this is commonly known by people doing retro fits.
Early pre digital servo drives can be controlled by a simple DC signal but you need a motion control card to output that signal based on feedback.
A 3D printer is a great tool / toy to learn cnc basics.
There are some cnc systems being sold that use a PC along with some interface cards , they are one of the easier ways to build a cnc in reasonable time and effort.
It is packaged with basic software and such.
Click to expand...
That sounds like a reasonable thing to do. I will look for a cheap system to plug into to learn the basics. Problem being though, cheaper 3D printing systems do not use servos, but steppers. Are the systems so different that I will not learn servo from stepper?
 
They are different- steppers are open loop, no feedback. Servo systems have feedback (shaft encoders)
Servo systems are intelligent, the controller knows where the motor is at all times. Steppers are "dumb"- you give a pulse and hope
the motor moves the amount you want
 
graham-xrf said:
There was a time when what was meant by "servo" was a DC motor, with tachometer output generator on the shaft for speed feedback, and possibly synchros for positional feedback. With the coming of optical encoders, stepper motors, permanent magnet multipole AC drives, and now, AC drives with current phase sensing for traditional AC induction motors, the choices have expanded enormously.

+1 on @sdelivery 's advice about don't buy until you know more. Let us get some terms right. One can get "controllers". Then another bunch of more powerful electronics known as "drives", usually with local controller buttons and tiny number displays added, but normally connected to the CNC control computer. You might be running some software, like "Mach4" , or "LinuxCNC".

Then you get the motors. These can be more applied to servo work when they have built-in shaft encoders, and logic pulses interface. That bit of kit can sometimes become a brand lock-in, to an extent. Motors generally have no choice but to be motors, and one can usually add one's own encoders, with some work. you need not be forced to purchase the whole ensemble.

For CNC, where the motors that move stuff on slides can often be geared down, or toothed belt driven, and it works a ball-screw anyway, stepper motors can be used. A raw opn loop stepper is not good. For CNC, you need the type with feedback drives. These are noisier than true servos, but are about a third of the price, which is why they are so widely used.

If your CNC includes real-time control of the main spindle, then the drive is a fatter thing, only needing speed control feedback, and has to be rated to the full torque of the machine. It needs to be of the type under servo control that can deliver that full torque, even at very low speed, or stopped, or even while being driven backwards while actually spinning forwards (i.e.decelerating to controlled stop under inertia).

I would think the motors you have listed could be driven by almost any good servo drive. There has to be the setup where you enter the number of poles, and other motor characteristics, so your system can get going. The connectors for such things can be relatively expensive, but if they came from a previous build, then getting hold of the cables and connectors is a huge plus. One has to study, and know the exact form of feedback signals, to ensure there is compatibility. Fortunately, there is lots of standardization in the industry, and even if incompatible, it is usually possible to adapt.
Click to expand...
I have a complete 4 axis open loop stepper kit at home in NY to make a large cnc router. I know it won't make up for missed steps, but I bought larger motors (1200 oz.in) to reduce the chances of those missed steps. I don't have time to fiddle with cnc there since we are building a house and other buildings on our property. I neglected to bring the kit with me to Florida for the winter.
But here in Florida, I have time to build a cnc machine. I thought I would convert a lathe to cnc but have been deterred because it is a small machine and has flat ways (Atlas 10F). I have a treadmill motor to use for the spindle. I have to work out an encoder and find something to drive it with to ensure it maintains speed. Then I need to figure what I need to x and y drives. I don't plan to make so much with it that it will wear out and get sloppy, I just want to learn on it...cheaply.
As sdelivery states, buy something cheap to learn on.
 
JimDawson said:
The short answer is a resounding NO. Don't buy them. They require a Fanuc controller and drives to run. It's the most convoluted system I have ever seen. They work great when you have all of the Fanuc hardware and controller, but to try to use them in a retrofit or a new build is virtually impossible.

Yes, there is a way of controlling the timing. There are many motion controllers available. Normally the system would look something like this

View attachment 437689
Click to expand...

Okie Dokie! I don't like convoluted. I'm going to try cheap and simple (as simple as cnc can get) for now. Learn some, do some more.learn more, do some more.
 
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