Case Studies: Level Wind Slitter Upgrade


Our customer had a recurring product quality problem that caused a considerable loss in production. An existing tool slit material into 18 strands, which were then re-spooled onto individual cores. During the re-spooling operation, a thin one-inch wide polyurethane liner was added to one side of the material.

The problem occurred during spooling. The core with the ply material was held at a constant torque and as the diameter of the ply roll decreased, the web tension also changed. Measurements put the web tension in a range between 1 to 3.2 newtons (N). Our customer required a solution that would allow a variable torque on the poly spool to provide a constant web tension of the roll as the diameter increased. The target web tension was approximately 1.2 N.

Phase 1: Prototype and Verification

AP Engineering Services was asked to develop a prototype that, after being proven, would need to be retrofitted to both the 18-station slitter machine and the secondary re-spooler machine. The design had to be a cost effective tensioning system that would control tension throughout the reel winding process and keep a constant web tension on the reel. The system also had to be applied to the machine with minimal impact to the company’s production schedule.

We developed a concept in which variable brakes would be introduced to each station, with the poly roll sitting directly on the shaft of the brake. One station would then have an ultrasonic sensor to read the diameter of the roll during production runs. This single sensor would control and vary the tension of the other 17 stations via a PLC and custom software written by AP Engineering Services.

Phase 2: Complete Slitter and Respooler Upgrade

Development: The particle brake system would provide the torque variations needed and would be controlled through a PLC based control system. The PLC would calculate proper tension per unit of diameter change measured by the ultrasonic sensor. The particle brake would continually update with new tension and could be independently controlled by utilizing an 18-station interface screen. Operators would be able to independently adjust the torque vs. diameter relationship on each station to effectively “dial in” each station.

Project Design and Build: AP Engineering Services began work on the full upgrade after the customer tested the prototype and felt it was a viable solution. The upgrade consisted of fabricating two complete assemblies as well as 17 similar assemblies with the ultrasonic sensor and bracket removed. We also provided the design for the control panel for the 18-station line and the re-spooler, the brakes, the controlling PLC, and a variety of other necessary components.

Installation: AP Engineering Services developed complete installation instructions and provided these to the customer whose engineering team completed the mechanical and electrical installations. We synchronized the activities surrounding the project with precise planning and weekly meetings to keep everyone involved up-to-date. As a result of our strong project management, the customer’s engineering staff required less machine downtime thereby preserving production runs.

Conclusion: The installation was completed and testing of the rebuild was successful, exceeding the customer’s expectations. The production schedule was not altered and the install was completed well within the allotted production down time, resulting in increased production for the week. Our customer stated that “the machine was running great and the issue of increased tension on the liner from outside of the roll to the core had been reduced.” Measurements showed a tension range between .8 and 1.4 N, a vast improvement over the original 1.2-3.2 N range. Our work helped to achieve the customer’s goals of increased production and increased quality.