There are various regulations depending on where the products will be sold regarding the accuracy of the weight that is provided on consumer facing labels and the different penalties for non-compliance. Additionally, distributors and retailers may have their own standards and penalties, as most large companies understand that a scandal caused by mislabeling can carry considerable costs. To further complicate matters, these rules can include standards or language pertaining to “average” or “batches”, so that a combination of overfilled and overfilled packages can meet a certain standard.
In the US, standards related to product labeling are defined by the Department of Commerce’s National Institute of Standards and Technology (NIST) Manual 133, which defines specific net content laws for prepackaged products. This standard applies to the number of packages that can be underweight without exceeding the MAV or the Maximum Variation allowed in any case. All advanced industrialized countries have a similar set of regulations governing package weight and associated product labeling. Having real-time analytics on your checkweighers gives you peace of mind that you are operating in compliance.
Weight control operations
With all these standards governing, setting up and managing a checkweigher can sometimes require a bit of sophistication.
Some manufacturers control the weights in “bands” of acceptability which may include:
Insufficient weight: rejected
Underweight – OK (within acceptable tolerance, but needs to be controlled or adjusted)
Overweight – Ok (within acceptable tolerance, but needs to be monitored or adjusted)
Overweight – Rejected
The “Ok” bands allow workers to respond to a system that is possibly out of tolerance. In very sophisticated systems, this data is used in an automated feedback loop directly to the filling machines to adjust on the fly. For other operations, having real-time access to these bands can make the difference in keeping a line running and having to stop a line that is now producing too many rejects.
In ALL cases, having a running real-time log of checkweigher manufacturers scans can help keep waste to a minimum, but it also demonstrates a commitment to label accuracy should a problem arise.
There are two key factors that are used to judge a checkweigher for an application, linearity and repeatability.
Linearity defines how close a measured result is to the actual weight of the item being weighed. The smaller the error measured when running sequential test weighings, the better the linearity.
Repeatability is measured in standard deviations, again using a sequence of test weighings. The smaller the standard deviation, the better the repeatability of the device.
You should consult with an application engineer or system vendor to ensure that the machine you select will deliver the correct linearity and repeatability in your operating environment and application for the desired duration of operation.
Checkweighers have the obvious application of ensuring that a package contains the correct weight of a product. However, people are creative! Checkweighers are also used for other purposes, such as counting products, for example the number of screws in a bag for product assembly. They are also used to ensure that a mixed box of components has the correct combination of components or the correct paperwork. Checkweighers can also be used to classify products to be classified into similar groups and to make sure that an operation has been performed according to the standard, for example, if enough weld coating was deposited on a crankshaft before entering a machining center.
However, checkweighers are truly the ultimate production waste management machine. You can get incredible information on ways to reduce production waste by using real-time checkweighing analysis. Now, with Worximity enabling API connectivity to the most popular brands and models of checkweighers, these in-depth analyzes can be obtained much easier and faster than ever before.