What is CheckWeigher?

Checkweigher

The first foundations of the principles of Checkweighing were laid in 1976. Since then, the documentation has been used extensively by current and potential CheckWeigher users, as well as weights and measures professionals and academia. This paper provides an in-depth coverage of the basic concepts of Checkweighing, as well as current developments in the packaging industry and Checkweighing applications.

The aim of this content is as follows:

To inform those working or interested in the packaging industry about the basics of Check Weighing
To reveal the areas in which Check Weighing can be used
Provide an overview of system requirements and possible needs
Guiding the process of selecting the most appropriate checkweighing system for a given application
Create a reference source of information on CheckWeigher

What is a Checkweigher CheckWeigher?

CheckWeigher is a system that automatically measures the weight of a product passing through the production line, classifies the product according to the data obtained and directs it to the relevant category. It has the capacity to weigh almost all (100%) of all products moving through the line during the production process.

In general, the physical components of the Check Weigher system consist of Inlet section, Weighing section, Outlet section, Chute or line separators and computerized control mechanisms. The design and operating principles of these components may vary depending on the product to be weighed and the environmental conditions of the facility.

In short, CheckWeigher weighs a product, classifies it according to the relevant weight range and performs sorting when necessary.

Main Areas of Use of CheckWeigher

Checks the weight of packaged products and detects under- or overfilling.
Ensures that the net contents of pre-packaged products comply with legal requirements.
Checks whether components in the package are missing, e.g. labels, user manuals, closures or coupons.
Determines by weight measurement whether there is a missing number of packages such as cartons, bottles, bags or boxes.
Checks the weight ratios of packages containing solid-liquid mixtures for compliance with set standards.
By analyzing the data, it reduces product losses and optimizes filling settings.
Classifies and categorizes products by weight.
Guarantees product conformity with customers, institutions or legal authorities.
Perform pre- and post-process weight measurements to check the performance of the production process.
Meets USDA or FDA reporting standards.
Measures the efficiency of the production line and provides detailed reports.

Statistical Uses of CheckWeigher

Case Study:
On a production line processing 100 packages per minute, if 15 packages are sampled every hour, this represents only 0.25% of total production. This means that manual sampling often offers low coverage. With CheckWeigher technology, 100% sampling is possible, making quality control processes more reliable.

Today’s state-of-the-art Check Weigher systems quickly and accurately deliver data that would otherwise have to be collected manually. This is a huge advantage compared to limited sampling in off-line systems.

Statistical Uses of CheckWeigher:

Analyze production by weight zone or classifications.
Defines multiple zones for more detailed filling information.
Analyze the total quantity and weight data of production to provide information on overall performance.
Measures production efficiency by monitoring product flow rate.
Alerts operators and systems in out-of-tolerance situations with standard deviation analysis.
Records and reports production data for management and supervisory authorities.
Analyzes the performance of single or multiple filling heads.
Monitors production data by shift, hour, day or over the entire production period.
Guide process improvements with Statistical Process Control (SPC) graphs.
Supports automatic process adjustments and closed loop control.
Integrates with high-level information systems and PLC controllers.
Organize and archive quality control records.

Key Advantage: 100% Sampling

CheckWeigher offers an error-free inspection process by analyzing every product in the production line in its entirety.

Inspection and Control Functions

Beyond quality control, Checkweigher can also be used for various auditing purposes. As a fast and integrated quality assurance system, it can

Detects open sections of cartons or boxes.
Detects missing lids.
Checks barcode and label accuracy.
Detects possible metal contamination in the product.

With these features, the CheckWeigher System functions not only as a weighing device, but also as a comprehensive quality assurance solution.

Why is Checkweigher Necessary?

The packaging and processing industry often uses Checkweighers to act as a kind of “checker” on the production line. The checkweigher instantly measures the weight of the packages as they pass over the belt, and therefore weeds out unexpectedly over- or under-weighted packages before they reach the customer. This ensures that only packages that meet the set standards are sent to the end user.

Handbook 133 of the Department of Commerce’s National Institute of Standards and Technology (NIST) provides specific rules on the net contents that wholesalers, retailers and manufacturers must indicate on the package. It describes in detail the method and means of inspection. From the minimum number of packages that must be checked, to the size of the package and the amount of packages that must be opened to comply with the standard values, all procedures are defined here. In addition, the permissible tolerances for low-weight packages and the Maximum Permissible Variation (MIVD) value are also clarified in this document.

It is critical that packaged products are weighed with a Checkweigher, especially to determine if they meet the MIVD values. NIST Handbook 133 describes in detail the acceptable weight values for packages. The State Office of Weights and Measures is responsible for enforcing and auditing these clear content rules. If deficiencies are found as a result of the inspection, different sanctions can be imposed, ranging from verbal warnings to legal action.

Verbal discussions between the inspector and company officials reveal whether the rules and regulations are generally complied with or where mistakes have been made. If results are found to be substandard, inconsistent or worse than similar packages, the inspector will draw particular attention to these deviations.

TIP: Handbook 133 is available from the United States Government Printing Office, Washington, DC 20402- 9325.

Net Content Regulations

If the check with Checkweigher reveals any of the defects specified in Handbook 133, this is considered a breach of legal requirements and the organization may face criminal action. Some of these violations are:

One or more packs have an underweight error that is much higher than allowed by the standards,
Detection of an average negative deviation for all parcels,
A serious error in the weight-based price calculation for one or more packages with a price tag.

Clear Content Edits

One or more packs have an underweight error that is much higher than allowed by the standards,
Detection of an average negative deviation for all parcels,
A serious error in weight-based price calculation in one or more packages with a price label.

Legal Processes and Practices

Legal sanctions can take different forms depending on the instructions given by the inspector or court decisions. These include

Cancellation or Suspension of Sale: This involves suspending the sale of products until official authorization is issued.
Re-weighing or Regulatory Orders: A specific batch or the entire batch may be withheld from sale until the accuracy of the products’ ingredients or labeling information is proven.
Prosecution Procedures: Actions such as the purchase or seizure of products may be taken to prove a violation of the rules.

Smart Checkweigher solutions and accurate weight control techniques play a major role in preventing customer complaints or legal problems due to underweight packages. In addition, a well-designed Checkweigher system not only ensures high accuracy but also feeds back to the filling line, keeping the average fill quantity at the desired level. This prevents cost increases due to overfilled packages.

Checkweigher Usage Areas and Advantages

Checkweigher can be used at various points in the production line. Often placed before or after the packaging process, they are ideal for checking the accuracy of filling operations. For example, a checkweigher can check for missing or excess content after filling, as well as detect accidentally added parts.

These systems not only offer quality control, but also cost savings. For example, accurate weight control prevents waste due to overfilling. In addition, complaints from customers and legal problems are avoided.

Which Products Can Checkweigher Weigh?

Checkweigher can be used to weigh a wide range of products from 1 gram to hundreds of kilograms. Here are some examples:

Small products: Small materials such as CDs, boxed disks, medicine bottles or bolts.
Food products: Bread, yogurt or other density-based products.
Industrial products: Industrial products of different weights that need to be measured for storage or invoicing purposes.

What is the Difference Between Static Weighing and Automatic Weighing on a Moving CheckWeigher?

The common belief in the weighing industry is that building and testing a scale is simple. But often the real complexity comes in the form of measurement certificates to prove the accuracy and repeatability of the weight value that appears on the display screen. Since the CheckWeigher is not a static scale, the applicable standards for static scales do not apply to it exactly. Therefore, choosing or understanding the right CheckWeigher is not always easy. Because there are no strict accuracy rules, companies are free to make whatever accuracy claims they want and conduct tests in their own way.

On the other hand, instead of an accurate CheckWeigher, some businesses try to cut costs with a “static-based” setup consisting of an indicator, a photocell and a conveyor that can process data at high speed. However, such statically oriented systems are often not designed for in-motion weighing. The constant vibration caused by the product coming off the conveyor and the oscillation of the load cells can lead to inaccurate measurements or damage to the equipment.

ACheckWeigher must be able to calculate the correct weight of the package in less than 1 second. For devices used for static weighing, fast response time is not a priority, so settling times of up to several seconds can occur. It is also often not possible to manage dynamic effects during movement with averaging gauges.

While there are not many strict rules for CheckWeigher applications, provisional codes for automatic weighing devices have been recognized in NIST Book 44. Nevertheless, since CheckWeigher manufacturers are not legally obliged to design according to these codes, it is necessary to do a thorough research to choose the right manufacturer. Detailed information on how to evaluate CheckWeigher manufacturers is provided in chapter 4