fanuc 'red cap' motors

[mmjpotter]

Can anybody give me some advice on these motors?
I have 3 Fanuc 'red cap' servo motors model 20S and I need to drive these with brushless analogue amps. using a +/- 10 volt reference signal.
The motors don't seem to provide the standard 3 phase 'Hall effect' outputs. Does anybody know how to decode the fanuc encoder outputs into 3 phase commutation signals Ha,Hb,Hc or should I just replace the fanuc encoder with something like the 'Servo-tek' ST50 encoder which can produce both commutation and quadrature outputs.

regards
Mike

[Al_The_Man]

There was a previous post here that I gave the original poster some info on the Commutation signals, I believe he was making a custom interface.
It may be worth to PM him if you can find it with a search.
Al.

[KTP]

Yes, that was me. We developed a step/dir to analog (+/-10V) controller that will also output the 3 hall states to your amplifier, depending on which Fanuc motor encoder you have. More info can be found at www.skyko.com

[mmjpotter]

Thanks Al. I found the thread, and I have been reading through your posts-
very interesting and a great help - you have pointed me in the right direction thanks again.
KTP, it is also encouraging to know that you were able to use this information to produce the Hall signals for your project. My control outputs the +/-10 volt command ref. direct and does not produce step/dir info so I can't connect to your board.However it does look like a great adaptor for those who wish to convert from srepper to servo control.

best wishes
Mike

[Steve@Reliance]

You guys seem to be fairly knowledgable with this stuff. Maybe you can answer a question for me. our Hurco BMC 30 has these servos and since we have owned it the X axis goes in the wrong direction, always + vs. - and vice versa. we have talked to Hurco at length and no one seems to know why. We have tried everything, switching encoder wires, changing the phasing on the amp etc. I'm a machinist not an electrician, so I don't understand how the system works. The Hurco sevice guys tried hard but they didn't seem to really know how it worked either. Right now we have just learned to program backwards, but it is really inconvienient. Can someone help me?

[Al_The_Man]

If it is a Fanuc or Mitsubishi system there is a parameter that you change from 1 to 0 (or vice-versa) to reverse direction of servo, many controls follow this example.
With a DC servo it is easier to switch changing connections than AC type.
Al.

[KTP]

Mike,

Ah, ok, I didn't understand that your control already output +/-10V control signals. Well, you could still use the Pixie to generate the hall states (it does that in a CPLD using the signals from the Fanuc encoder). It might still be a cheaper alternative than changing out your encoder..they are a bit weird on the mounting.

[mmjpotter]

Good idea KTP. So I can use a Pixie to generate commutation signals and then drive the amp with my own +/- 10 volt command.

steve@reliance, If your servo drives are digital then the chances are, as suggested by Al-the-man the polarity is governed by parameters. If the drives are analogue and use a +/-10 volt command then the motor direction will follow the command signal polarity. However you must ensure that the positional encoder feedback to the control and any velocity feed to the amplifier are relative to the command signal polarity, in order to maintain the servo balance.

[Al_The_Man]

Originally Posted by mmjpotter If the drives are analogue and use a +/-10 volt command then the motor direction will follow the command signal polarity.

The systems I have worked with, even with analogue, the controller will take care of reversing the analogue signal and look at the feedback device accordingly, depending on the 0/1 status of the parameter.
If you have a DC servo and ±10v analogue, and do not have the parameter reverse ability.
Then normally reversing the analogue signal and the A & /A signals of the encoder will do the same thing.
Al.

[hurcojohn]

steve...do you mean when you push the jog + button the table physically moves to the right???what about y-axis if you push the jog + button, also, if you program a + direction move it moves negative?

[ravin]

only setting are changed in machine parameters

[hurcojohn]

steve...also...what software version on your hurco...am hoping max32 version 1.61???...at top of input screen...john