Name: Stretch Wrapper

The customer wanted the material on a stretch-wrap machine to be easily prestretched to recipes.

Overview: Using custom stretch-wrap recipes to accommodate the variations in film thickness, size, weight, and fragility of the stacked material, the binding is accomplished by wrapping the product while stretching the plastic material. This stretching is accomplished by pulling the material with the motor controllers that are paying out stretch-wrap from the roll of plastic sheet material.

Application benefit: By providing a unique speed profile between the master and follower stretch drives, the percentage of stretch can be custom tuned to match the film material thickness, product size, shape, and weight in a preset recipe.

The customer's product: The customer's product is a stretch-wrap machine that applies the stretched plastic sheeting to the pallet of materials by rotating the pallet while feeding the stretch material. The machine moves the stretch-wrap feeder up and down to wrap the pallet from top to bottom.

The customer's present solution: The customer's existing solution for stretching the material is an analog tensioning control that requires a re-setup of the machine for each recipe change. The customer's request was for 2 low-cost Variable Frequency Drives (VFDs) that could control the stretch profile from recipe commands.

KB visited the customer's engineering demo machine and worked with the customer's engineering staff to identify the functional and design specifications.

KB's capabilities for solving the problem: For the Variable Frequency Drives, it's the KBVF series. This series incorporates the powerful, second-generation, micro-controller that is programmable for custom OEM application using software with proprietary motor monitoring capabilities. KB's engineering staff has a reputation of working directly with customer applications to reach satisfactory solutions.

The KB solution: The objective was to maintain a relative-stretch speed profile during acceleration, run, and deceleration of the master and follower payout drives. The KBVF signal interface SIVF was designed to input the speed reference and follower speed profile while the SIVF was designed to output the profile speed. The KBVF software was designed for the master and follower to maintain the speed profile throughout the speed range. Additional jog mode logic was added for the beginning and end of the pallet wrap process. The Dynamic Brake Module (DBM) was used with each VFD to absorb the deceleration energy.

The results: Using the KBVF-24D with SIVFR and DBM, the custom stretch profile is controlled during the acceleration, run, deceleration wrap cycle. For each particular wrap application, the customer's Programmable Logic Controller (PLC) sends the speed reference and stretch profile required by the recipe.

Customer's strategic advantage: The customer got just what he wanted - no more, no less - with simplified start-up, increased cabinet space, reduced costs, and a significant advantage over the competition.

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