A Simple Loss-in-Weight Feeding Control that Will Run Reliability in a Standard PLC

Many of Flexware’s customers had a common complaint – their loss-in-weight feeders were “black boxes” that failed frequently and could not be maintained by internal resources, resulting in lost production and high costs. These devices also had no graceful modes of degradation. For example, if a load cell failed, it was impossible to run the system in a degraded mode until a new load cell was put in place. As one customer put it: “Can’t someone provide me with a simple loss-in-weight control that will run reliably in a standard PLC that I can maintain?”

To address this problem, Flexware has developed a loss-in-weight control system we call IFEED. This system is typically put into whatever standard PAC is currently controlling the process, and requires only inputs from load cells on the feeding hopper, and an output to a variable speed feeder.

The IFEED system adaptively learns the feeding properties of all the products that are run through it, and continues to update these at all times, for example, tracking changes in material flow characteristics due to seasonal humidity changes. Typical flow accuracy is 0.5 to 1.0%, depending on the application. Head pressure compensation is included.

At the push of a button, IFEED can be switched immediately and seamlessly to operate in a “feed-forward only” mode in which the load cell inputs are ignored, and feeding is based on prior learning. Although less accurate, this can be an invaluable way to continue production while fixing a load cell problem.

Included in every IFEED system is an HMI window that shows complete diagnostic information to operators, technicians, and engineers.

IFEED has been installed in over 60 manufacturing applications with excellent results. All have reduced downtime, and many have a flow accuracy near 0.5%. Our customers are able to maintain their systems and it is rare that they need to ask us for help. One very large food plant has finished a program to remove all of its existing LIW feeders (from a well-known supplier) and replace them with IFEED systems.