How to control AC servos

[floriptw]

I'm new to CNC and am at a standstill on a project.

I'm trying to get a lathe setup to run off Mach3. I ordered a bunch of parts, all showed up, I got excited, and now I'm singing the blues. Being new to this I thought the servos were DC...they're AC. Now I have a couple drives, a smoothstepper, and no machine to use them on because it doesn't appear they'll work.

The servos on the machine are Fanuc b6/2000 with accompanying amplifiers. They require 24v, 15v, -15v?, and 5v. I'm in no position to buy any industrial grade/price stuff so I'm wondering what options I might have.

Would swapping out the AC servos to DC be the simplest route?

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[Jim Dawson]

Buying DC servos might be a good option. But first, what drives did you buy? And what motors are they compatible with? I assume you bought a machine with no original controls on it at all? Going to need a bit more information from you to be able to give intelligent answers.

The Fanuc servos and amps will work fine, and the power supplies are not that expensive, except for the 24V a computer power supply would work. The problem is that you are not going to control them with a smoothstepper.

[floriptw]

Buying DC servos might be a good option. But first, what drives did you buy? And what motors are they compatible with? I assume you bought a machine with no original controls on it at all? Going to need a bit more information from you to be able to give intelligent answers.

The Fanuc servos and amps will work fine, and the power supplies are not that expensive, except for the 24V a computer power supply would work. The problem is that you are not going to control them with a smoothstepper.

I bought Gecko320X drives. My CNC router uses them to drive the Fanuc 5M servos, I used my router as purchase road map.

The machine came with the original controls, when I powered the machine on, the control screen was filled with alarms and wouldn't respond to input. I bought the machine at auction for $600 so I was expecting there to be some issues.

It looks like I can pickup 5m servos off ebay for a decent price but don't know ho they'll perform on the lathe. It's a 19"X40" machine so the carriage has some weight to it. Suppose I could adjust the pulley ratios.

[ger21]

Buying brushed DC servos is the simplest option.

[Jim Dawson]

I agree with Gerry, make it like your router. Having 2 machines in the shop with the same controls reduces the learning curve dramatically. Even if the performance of the lathe is reduced somewhat from original I'm pretty sure it will work fine with the 5M motors.

[Al_The_Man]

Fanuc 5M motors are fairly large for that size machine.
You can run the DC servo's on other manuf drives, but the 5 AC version cannot be run on any other drive than Fanuc they have a proprietary encoder although a BLDC convertor can be purchased for them.
.The first thing to check on the used DC motors is the brushes, I have the minimum length for them somewhere.
Helwig Carbon sell the replacement brushes.

Spec:
Fanuc DC Motor 5
Type: 0-2500M 2500 pulse encoder
Permanent Magnet DC Servo Motor
Output Power: 0.8 KW (1 HP)
Rated Torque: 55 Kg-Cm
Max. Torque: 480 Kg-Cm
Max. Speed: 2000 Rpm
Rotor Inertia: 0.05 Kg-Cm-S 3
Back EMF Constant: 50 V/K RPM
Torque Constant: 4.87 Kg-Cm/Amp
Mechanical Time Constant: 15 mSec
Thermal Time Constant: 55 Min
Weight: 16 Kg

Al.