FANUC: Useable Servo Motor/Drive/Encoder Combos for Rotary 4th Integration

[the_gentlegiant]

Can anyone tell me with a fair amount of certainty, if it is a problem to run a Fanuc Red Cap Alpha Series Servo Motor with a drive that is one size bigger then is specified for the motor?

Motor wants - A06B-6079-H103

I have - A06B-6079-H104

Also: The machine I want to use this rotary table on uses Absolute Encoders on all axis. The rotary table in question has an Incremental Encoder. Of course the Servo Amp is switchable to take either, but is this going to be a problem? I mostly want to use it for indexing. Full 4th maybe once in a blue moon.

I have another rotary table with Absolute Encoders running on a fully Incremental machine. It works okay but won't home properly. It may be because I wired the cable for Absolute but am using it Incremental. I think there is maybe one or two wires that are different. I could be wrong on this. The irony is that this rotary table is too big for the Absolute machine.

Thanks for any help.

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[drdos]

It would help if we had the motor part number. The way Fanuc works is you pick out the motor first then you choose the amplifier to match it. All of Fanuc's amps can run a handful of motors so we can't say for certain if your motor/amp combination is a match without the motor part number.
As far as absolute or incremental goes the controller really doesn't care. You didn't specify which controller you have so I am going to assume series 16MC. On the 16 controller parameter 1815 determines whether or not you are using an absolute. All the absolute does is allows the encoder to retain it's position while the machine is powered off. That's its. This is done by a battery that fed to the encoder via encoder cable. If you aren't homing correctly then chances are you don't have your reference counter set right.

[the_gentlegiant]

Hello drdos,

If you'll notice, I already made the servo motor/amplifier match-up. That's how I determined the 'What it wants" in my post. The motor is an A6/2000 with tapered shaft and incremental encoder. (B077) Sorry I can't recall the middle numbers of the motor part number.

The books say the A6/2000 wants the A06B-6079-H103 size drive. I'm all wired in previously with an H104 size, Meaning one size larger.

My question was is this a problem. I can certainly see how using an under-sized amp could be a problem, but is there anything about how these servos are driven where having excess current capacity to draw on could be a problem. I've always thought that motors draw what they need and that's it. You don't push current into a motor. (Maybe in braking?) But are servos different? Do these drives have active current limiting per say? Where running and oversize drive would limit at a level that is too high? I mean what electronically is holding me back from using this non specified, one size too big drive?

This current setup I'm wanting to do is on a Mori 18MC. The poor homing setup is on an OMC. I'll have to check into the counter setting, although the table moves properly in use. I have to set a small zeroing correction in the SHIFT register. It's different every time I install the rotary table. Grid shifting it didn't work either. Technically I have my absolute encoder rotary table wired in wrong on the OMC. Incremental connections go to the control first and from there to the drives. An absolute setup goes to the drive first then to the control board. So I'm running an absolute motor connected as if it's Incremental. At least that's what I recall back when I was originally installing it. I noticed my mistake after I had already wired all the cables, and didn't feel like rewiring for a different connector. Soldering on those Honda and Hirose connectors is very challenging.

I'd appreciate any more thoughts about using the H104 when the books say H103. I'm really trying to avoid the extra cost and time of changing one or the other out.

[drdos]

My sources say Yes. The A06B–6079–H103 drive is what Fanuc calls the SVM1–40S while the A06B–6079–H104 drive is what Fanuc calls the SVM1–40L I think (S) is small and (L) is large. But if you look at the attachments it clearly show that running the A6/2000 motor.

Hope this helps

[the_gentlegiant]

Hi drdos,

You are absolutely right! Looks like either will work. I simply wasn't looking deep enough in the manuals. Thank you for straightening me out, and saving me hours and some hundreds of dollars. :-)