Weighing Integration for a Packaging Project
An in-line NW-CW-5 checkweigher supplied for a packaging project, with belt interface and accuracy conditions clarified together with the line integrator.
Checkweigher
A checkweigher weighs each product as it moves along a line, compares the reading with a target weight and diverts units that fall outside the accepted band. Belt width, line speed and the reject device decide whether it fits the line.
A checkweigher sits in a production line and weighs every unit as it passes: the belt carries the product over a weighing section, the reading is compared with the target and the accept limits already set in the controller, and each unit is either passed on or sent to a reject device. It is a decision taken at line speed rather than a careful bench reading, so the weight range to be judged, the tolerance band and the rate the line runs at are what decide the machine and its fit.
The product itself shapes the reading. A stable single item of defined shape gives a cleaner result than loose material, a bundle or a pack that shifts on the belt. The weight range and the smallest difference that has to be detected set the load cell and the division; the belt width has to take the widest product with clearance, and the belt speed has to keep up with the line while still leaving the product steady long enough to be read. High throughput and very light products are the two ends that usually need the most discussion.
Then the reject and the interface. The reject method follows the product – a pusher, an air blast, a swing arm or a drop flap – and each needs its own space beside the line plus a place for the rejected units to go. On the interface side, work out how the checkweigher talks to the rest of the line: a signal to stop, a start and stop from the line, a count of passed and rejected units, or a record handed to the site system. Where the machine will stand, and whether it is a stand-alone unit or built into an existing conveyor, belongs in the same decision.
Verification belongs in the same conversation. The way to confirm the machine does what the line needs is to run the actual products, at the actual speed, through the checkweigher in the layout where it will be installed, including the lightest and heaviest item and the products the reject device will handle. A check made by hand at a bench is not the same test, so the condition and the samples to be used are worth agreeing before the machine is built.
Primary task
Weigh every product as it moves along the line, compare the reading with the accepted band and divert the units that fall outside it.
Questions to answer
- What is the weight range of the products to be checked, and how wide is the accepted band around the target?
- What is the smallest weight difference the line has to detect, and at what throughput?
- What are the product sizes, and what belt width and line speed does the checkweigher have to fit?
- Which reject method suits the product, and is there space beside the line for the reject bin?
- What signals or records does the line need from the checkweigher, and can the real products be run for verification?
Next action
Open the Checkweigher product page and the packaging line case, then send the product weight range, belt width and line speed through the enquiry form.
NW-CW-5 Checkweigher
In-line checkweigher for packs up to 5 kg that compares every reading with a target weight and diverts packs outside the tolerance.