Checkweigher Machine Suppliers & Manufacturers

How checkweighers work and where they are used

A checkweigher (also called a dynamic checkweigher or in-motion checkweigher) weighs individual packages or products while they are moving on a conveyor, without stopping the production line. Each pack crosses a precision load cell conveyor belt; the electronic system measures the net weight of the pack in motion and compares it to the set target weight and tolerance limits. Packs within the acceptable weight window pass through; packs outside the tolerance are automatically rejected to a side lane, drop reject, or air blast rejection chute. Checkweighers are used in packaging lines for: legal compliance — pre-packaged goods sold by weight must meet average quantity requirements (EU Directive 76/211/EEC, NIST Handbook 133 for the US, UK Weights and Measures regulations); a checkweigher running on every production line is standard practice for food and pharmaceutical manufacturers to demonstrate compliance and reject defective packs. Quality assurance — checkweighers catch under-filled or over-filled packs that would otherwise reach the consumer. Missing product inside the pack (a missing component, a missing sachet) is often detectable as an underweight pack. Statistical process control (SPC) — checkweigher data (mean weight, standard deviation, fill rate trends) is fed to the filling machine control or MES system for real-time control of fill weight. Fill weight trend monitoring prevents gradual drift outside the tolerance window. Checkweighers are installed at the end of the primary packaging line, after the sealing machine, and before or after the labeller and coder. They are frequently combined with a metal detector or x-ray inspection machine in a combined inspection unit.