Hello,

I am new to this forum.  I am hoping to glean information and share in the future.

I have recently purchased a 3 axis CNC. A 1979 Shizoka STN, manual tool changer.  This machine has a General Numeric 5 series controller, pre-Fanuc.  Pretty old stuff!!  The x axis has a problem, what I don't know.  I would like to remove the controller and retrofit to a PC based control.  I may have to replace the servos for compatibility reasons.  I have been looking around at stepper motors and drives that would be PC compatible. I have many questions.  So I will ask the most important right now.

Are stepper motors the right direction for replacing the old DC servos?

I have looked at some CNC retrofit packages but the prices are just to pricey for this machine.  For 8K and over I could buy a good running machine without having to rebuild it.

Any input would be great.

Thanks,
Tom

depending on the voltage of the servos, you could go with a Gecko drive.  If they are above 80V then there are other driver options, but more expensive.  If the voltage is not much higher than 80V you could still run them at a lower voltage and just loose a little torque and speed.  I have some 140V servos that are running at 100V DC and can still drive a 4,500 pound machine at 400 IPM.

Vince

Thanks VInce.  I will find out the voltage for the servos.  Sounds like this option could save some bucks.

Tom

You may have to add encoders to the motors if they do not have them now.  It's not that hard to do, but it depends on the motor.  If the motors turn out to have encoders and be a voltage that the Gecko will drive, you may still have to change the encoders as the Gecko will only supply 50mA for an encoder.  But I am getting ahead here.  Once you know what you have then you can figure out your options.

Vince

I do have encoders dated 1979.  That is how I know the machine is a 1979.  I did plan on replacing them if I keep the DC servos.  I can replace with a much higher resolution for better accuracy.  When I get the machine in the garage, being it is still on my trailer, I need to power it up.  Which I still need to get or make a rotary phase converter. 

When I bought it the guy said the X axis stopped working so he unplugged it and the machine just sat.  When it was running the X axis failed from worn out brushes.  He replace the brushes and started having problems in the X.  The controller started popping the fuse then he would replace and it would pop again etc, etc... and finally just stopped working.

When I put power to it I want to swap the cables with Y &X to see if the its the motor, driver or amplifier.  I am not sure how to check though yet but the time will come.  Or I just replace it all and not have to worry about it.  I am in the planning stage right now.

Thanks again

Hello,

I am new to this forum. I am hoping to glean information and share in the future.

I have recently purchased a 3 axis CNC. A 1979 Shizoka STN, manual tool changer. This machine has a General Numeric 5 series controller, pre-Fanuc. Pretty old stuff!! The x axis has a problem, what I don't know. I would like to remove the controller and retrofit to a PC based control. I may have to replace the servos for compatibility reasons. I have been looking around at stepper motors and drives that would be PC compatible. I have many questions. So I will ask the most important right now.

Are stepper motors the right direction for replacing the old DC servos?

I have looked at some CNC retrofit packages but the prices are just to pricey for this machine. For 8K and over I could buy a good running machine without having to rebuild it.

Any input would be great.

Thanks,
Tom

Hi

Tom you will have to join www.cnczone.com and have a look at this thread  comparison of several drives , develop a professional quality and performance servo drive with hobbyist level pricing. http://www.cnczone.com/forums/showthread.php?t=38465

cheers