Name: Stretch Wrap Precision Tension Controller

The customer wanted an integrated amplifier, power supply and PID speed control for precision tensioning of their stretch-wrap controller.

Overview: In the application of stretch-wrap machines, the stretch tension needs to be controlled during acceleration, wrap, and deceleration. A closed-loop control from a tension feedback transducer can precisely control the wrap stretch by using a sophisticated PID circuit. In the PID circuit, the Proportional term maintains a close tracking between the reference and the feedback. The Integral term eliminates any difference between reference and feedback during steady state operation. The Differential term minimizes the difference between the reference and feedback during speed or load transitions.

The application benefit: By integrating the speed control with the PID and amplifier power supply, the stretch-wrap tension performance can be more precisely controlled, system cost lowered, set up simplified, and reliability increased.

The customer's product: The customer's product is large stretch-wrap machine used for wrapping a variety of plastic films around various palletized products.

The customer's present solution: The customer's existing stretch-wrap machine included a separate motor speed controller, power supply, and PID controller. Set up and troubleshooting required extensive knowledge about the individual circuit modules.

The customer's request was to integrate the speed control, electrical isolation, PID, and power supply for the strain gage amplifier into a low-cost module.

KB's capabilities for solving the problem: For the DC motor-speed control, it's the KBIC SCR DC motor control series. KB's engineering staff has a reputation of working directly with the customer applications to reach satisfactory solutions.

KB set up the customer's present individual components in the KB engineering lab resulting in written specifications based on reverse engineering and customer input.

The KB solution: The objective was to integrate all of the power circuits into a single PCB that included the KBIC DC motor speed control, PID op-amp circuits, power supply for the strain gage amplifier, and electrical isolation from the AC line. These circuits were designed onto a PCB attached to an "L" shaped heat sink and vertically mounted into the control cabinet for a minimal "bookshelf" footprint.

The results: The integrated product allowed the customer to switch from his discrete version while reducing costs, improving ease of set up, saving control-cabinet space, and improving reliability.

Customer's strategic advantage: The customer got exactly what he wanted - no more, no less - with major performance enhancements using custom control circuits and major advantages over his competitors.

A Win-Win solution for both the customer and KB.