The problem is your velocity control unit (drive) will not function properly without the tach signal. These units are velocity drives not current drives ( Current drive is what the pixie wants to see with its PID.). I modified the Pixie diagram to show this. If you do use a F to V converter ( US Digital ect...) the I and D terms in the Pixie will be basically useless ( This part of the tuning will be in the drive.).

Darek

Thanks Darek,

I have a few more questions and thanks so much for your insight thus far.

1.  Is this the type of F to V board I will need:  http://www.eidusa.com/Interface_Boards_F_to_V.htm

2.  Were the rest of my assumptions in my prior post correct?

3.  If the I and D functions are useless, is the p100 the way to go?  Will the board still work even though it won't handle the encoder signal?  Is there an alternative board or combination of boards to use?

4.  Suppose I was ready to junk the entire control system.  Meaning, I will only have the machine, motors, and external devices (spindle motor, coolant, etc).  What system would you reccommend I use?  I don't want to break the bank but I want a system that is appropriate for my machine.  Let me know if you need additional specs.

5.  The machine is currently using 3 phase.  If  changing the controller setup, would it remain three phase or is that dictated by the motors?

Thanks so much.

David

The F to V converter has to be bipolar, positive voltage for one direction and negative for the other ( I don't think the ones you posted will do that.). It also needs to output 3V per 1000RPM. Here is a link to the US Digital one.

http://www.usdigital.com/products/etach2/

Once you figure the price of this with the Pixie You would probably be better off with the Rutex step and direction drive.

http://www.rutex.com/us/home/index.htm

You will need a DC power supply for the Rutex drives. You should be able to use the existing servo transformer and add some bridge rectifiers and capacitors. If you are running this machine on a phase converter this would be preferred over the existing system. To elaborate your Fanuc velocity control units are the ones with six SCR's that fire on the three phase power. I have found these drives to be finicky on phase converters. You sure can not perform the scope pulse alignment as covered in the maintenance manual.

Darek

Hello Darek,

Do you think that is better a Rutex or original amps. with bigger servo motors? I have fanucs 20M and I am thinking of rutex R2020, but my servos are 213V , 18 A continuos, 40 A peak. Do you think rutex can handle it. Or can I use pixies with etach2 conected directly to the servo amp.

George.

George,

Rutex has a file MYSTIQUE.PDF about motor and drive sizing on this page.

http://www.rutex.com/us/home/index.htm

My opinion would be the R2020's would work fine for the Fanuc Model 0 and 5 servoes. The Model 10 would be boarder line and NO WAY on Model's 20, 30 and H10. I would not want to use a breaking resistor in series with the armature as suggested in the MYSTIQUE.PDF.

Darek

Darek,


What would you do in my situation??


Thanks,

George

Your velocity control units should have a DC power supply with PWM output (A20B 0009 0320). These are good drives. I would try to use them. With that being said a tachometer or a F/V convertor must be used.

Once you have the drives working stand alone, +/-10v analog signal, without the 6M mother board. At this point you can either choose a step a direction to analog converter or a controller board such as Galil or Delta Tau.

Darek

Darek,
Do you think that this Glentek CEMF to Velocity Feedback Conversion Card will work as a  F/V converter?

I have never seen that one. I could not find any support documentation for it on the Glentek site.

Darek

 A friend has broken Enshu Accu-mill just like the one pictured here.  I offered to try to repair it.  Does anyone happen to have the schematic diagrams for it or know where they can be downloaded from.

vr/rik