Advanced winding machine development at Sandia National Laboratories

Abstract

Sandia National Labs, New Mexico is designing and testing an improved version of its state-of-the-art capacitor winding machine. The new CL1610 winding machine is based on the mechanical design of three previous Sandia designed winding machines using a precision tool plate and guide roller design to provide very accurate material alignment and minimum roller drag. It features closed-loop tension control, precise material acceleration and velocity control, programmable logic controllers, and an improved and expanded operator interface.

The new machine will increase Sandia's capacitor fabrication capability by applying the tension control accuracy we now have for narrow width films and small diameter windings to films up to 0.2 m in width and windings up to 0.25 m in diameter. Tension control of ±0.05 N will be maintained on the new machine through a range of 0.25 to 4.90 N. The machine will implement variable tension control with the goal of optimizing the electrical performance of the wound capacitors. The tension variation will be based on a model developed at Sandia that calculates internal mechanical stresses and will serve to specify all mechanical stresses in a finished capacitor. The new machine will also have the capability to wind non-cylindrical capacitors while maintaining the tension control of ±0.05 N we currently have for cylindrical capacitors.

The capability to wind two to sixteen ply extended and buried foil capacitor designs with the widths and diameters mentioned above will be available with the new machine. Take-up mandrel velocity and acceleration will be controlled using a stepper motor that can be programmed to operate between O and 60 RPM and O and 3000 rev/min/min. In addition, the number of active turns, the number of pre- and post-insulating wraps, and the number of turns to the foil termination can all be programmed.

Operator errors will be reduced by automation techniques and instruction sets built into the PC interface. The machine will be controlled wit h a Macintosh computer that communicates with both the stepper motor controller and the programmable logic controller (PLC). Using a Sandia designed software interface on the Macintosh, all of the process parameters are entered by the operator before winding begins. Variable tension will be controlled through the same interface. The operator will enter the material properties and geometric characteristics of the capacitor and the computer will generate the tension variations necessary to achieve the desired mechanical stresses. The PLC will control winding tension and spindle braking, while the stepper motor computer will control take up spindle velocity, acceleration, and material travel distance. All of the process parameters obtained from the fabrication of a capacitor are entered into the computer automatically, or by the operator, and can be stored for later analysis.