Over in the RCM group I asked about the feasbility of using a master slave relationship in a CNC lathe so a part could be machined on one end and then switched from one chuck to another while spinning so the back half of the part could be machined. Below is the post I made to RCM with the first test results.
After the long discussion about one spindle following another and using a Gecko 320 servo drive I have the first test results. The servo motor has a 500 line encoder mounted on it and the Gecko Drive reads it in quadrature for a resolution of 2000 counts per revolution. I'm using another of the same model encoder mounted to another motor powered by a PWM power supply. This motor is the master and the motor controlled by the Gecko is the slave. The master encoder is connected to an LS7184 quadrature clock converter. The LS7184 accepts the encoder signals and outputs step and direction signals which are fed to the Gecko 320. As the speed of the master motor is varied the slave follows PERFECTLY! There is no perceptible (to me) lag or overshoot. And when spinning the master encoder at approximately 1 rpm the slave follows perfectly with NO cogging. When the slave is commanded to move only one step it does so without jumping as would a stepper when operated with just switches or by just touching the wires to a power source. Obviously the Gecko ramps up to speed to make movement as smooth as possible. In fact, even though the Gecko is fed only discreet step by step motion signals and position feedback is only in steps it acts like the whole system is analog, when the motor is the only analog device in the system. It looks like I can now grab a spinning part with two chucks at the same time without the worry of scuffing the part. Eric