Improved Accuracy Meat Packaging

In many industries, product is sold by weight. Any inaccuracy in the weighing system causes mislabeling, reduced product uniformity, and waste. Hatfield Quality Meats in Hatfield, PA relies on automated weight sortation systems to provide their customers with highly uniform meat products. Like all agricultural products, some variation is inevitable, so Hatfield Quality Meats sorts its pork ribs into 8 bins based on weight variations as small as 0.05 lbs. Each bin sells for a different price per pound, so not only is accurate sorting essential to meeting customer specifications, but incorrect sorting can also lead to lost revenue through product waste.

Hatfield’s in-motion scale system was not providing the accuracy it required. With weight bins as small as 0.05 lbs and scale accuracy of 0.02 lbs, there was little room for error. The system would lose tare between scheduled cleanings due to an accumulation of product on the belt, further reducing accuracy and precision. The dedicated scale head unit did not allow any customization, so Electronics Technicians at Hatfield Quality Meats began searching for a more flexible and accurate solution capable of 0.002 lbs accuracy, 10 times that of their current system.

Hatfield considered several products in its search for a more accurate and flexible solution. One upgraded dedicated scale head could not provide a fast enough sample rate for consistent measurements and the closed architecture did not allow for any customization. Other scale systems would cost almost $100,000 to implement.

By using the existing load cell scale base and a Q61LD Load Cell Input Module from Mitsubishi Electric, Hatfield was able to replace both existing PLCs, and the scale head unit with a single iQ Platform rack to handle all of the conveyor, scale, and sortation functions. This all-Mitsubishi solution reduced the amount of hardware needed and simplified implementation, which took approximately 1 month, while still maintaining production. The system is configured to detect when product is fully on the scale to ensure accuracy. This solution also allows integration with Hatfield’s existing MES-IT system from Mitsubishi Electric for logging the weight of each product directly to its SQL database without the need for a PC on the plant floor.

The Q61LD Load Cell Interface Module continues to exceed the performance requirements by providing 0.001 lb accuracy with high precision due to the 10ms sample rate and automatic sample averaging. The flexibility of programming an automatic tare routine in the PLC has cancelled out the zero-drift caused by product accumulation, and uptime is improved by eliminating line stops to clean and manually re-tare the scale. The upgrade paid for itself the first day by reducing the measurement error by an average of 0.17 lbs per rib. Weighing 2000 ribs per hour, the system saved enough money to pay for the upgrade in about 8 hours.