Checkweighers: control and optimization as a keystone for production lines

31 Août , 2021 Featured,News

Checkweighers: control and optimization as a keystone for production lines

Weight control: cost or investment?

Current regulations and procedures used to certify production quality require weight control on packed products. The law imposes on manufacturers to carry out the necessary controls and provide documentary proof, in order to guarantee consumers’ safety.

From this perspective, one might think weight control is basically an answer to current regulations, an obligation and, therefore, a pure cost. In fact, this is not what it really is: we will see in this article how the cost of the equipment can be turned into an investment.



Why carrying out weight control?


  • To comply with current regulations. The law protects final consumers, stating admissible tolerances in order to commercialize packed products. These values must be guaranteed for every single package coming out of the production line.
  • To respect the requirements imposed by large retailers and other customers. Major retailers and supermarkets are increasingly dictating clear and binding rules on weighing; every claim received have negative implications for the producer, causing financial losses and affecting commercial relations.
  • To protect company’s management: claims on products non-compliance usually involve the supplier and its managerial staff before the law.
  • To safeguard the brand and corporate image. The brand value and the costs to maintain it and improve it are well-known: public claims (the web and social media are huge news amplifiers) can significantly undermine this value.
  • To guarantee product’s quality. Weight is a quality-certifier parameter.
  • To manage efficiently the production line, by gathering all the information which weight control process provides.


Where do you implement weight control?



Every production process is a function of the product itself and its physical features, but companies must bear in mind that also the packaging has an impact on the control side, either for its dimensions, configuration or structural characteristics. It is possible to identify certain positions along the production line where a checkweigher can be installed to maximize the benefit.

  • Weight value verification.
  • “Metrological” check: companies need to ascertain that the weight of each single package stated in the label is confirmed by the value measured during the weighing procedure, thus respecting current regulations. This control must be carried out on the closed package only, in the same condition final consumers find it in the point of sale.

  • Control for internal use: carried out during the dosing stage, in order to implement the necessary adjustments to the filling system thanks to the feedback function, either manually or, even better, automatically.
  • Weight control of each single component added during the dosing phase, in order to guarantee the right product mix as stated.
  • Completeness verification
  • In the case of multiple packs, where several components or products are present, it must be guaranteed the completeness of all the units, according to what is declared on the label. Through a check-weighing system this assessment can be done easily. This procedure is not part of the “metrology logic” but it is key to ensure the quality of the product itself, thus avoiding claims. 



How do you carry out weight control?

The law imposes on manufacturers to guarantee and provide documentary proof that every single package coming out of the production line, along with the mean of the weight of the whole production, complies with legal requirements.



In fact, it leaves manufacturers liberty of action in deciding what method (procedure) to use for carrying out controls, but at the same time recalls them to take full responsibility on the process and its compliance with the regulations. The procedure and its outcome must be supported by documentary proof and made available for official authorities controls.


Basically, there are two alternative ways to carry out the weight check:


Sampling plan: based on the analysis of a sample which has to be representative of the entire production. This procedure has of course many weaknesses:

  • Sample products need to be picked during production stage and only afterwards it is possible to proceed with the data processing and analysis. The process, however, has already happened and, in case of negative outcomes, you need to intervene manually on the production batch, making the necessary adjustments with consequent costs and waste of resources. As a matter of fact, a batch which has been proved to be non-compliant must be rejected and cannot be marketed.
  • Being the sampling a random selection, the probability of marketing products out of weighing tolerance is extremely high: the number of pieces picked to carry out a sampling is derisory if compared to the total production (usually around 0.5%).
  • Performing sampling tests requires specialized staff and accurate intervention, with considerably high costs.
  • Since they have to be made available for external inspections, the data processed and the analyses outcomes require a careful and precise storage, normally entrusted to qualified personnel.


Total production check – 100%: every single unit is checked directly and automatically on the production line by means of a checkweigher: these are extremely advanced tools provided with automatic rejection/classification systems, that easily fit in the line and comply with international legal metrology requirements (e.g. MID). Strenghts, compared to sampling plans, are quite evident:


  • Control on each single product: units out of weighing tolerance are surely discarded at any time.
  • Continuous monitoring of the average weight of production, an essential parameter to meet legal requirements.
  • Weighing is performed in real-time, thus making available constantly updated production data, which is processed until the time you actually query the system, allowing to make adjustments promptly.
  • Modern checkweighers do not require operator supervision; on the contrary, since they are in continuous interaction with data processing and management systems (products storage, production batch, etc.), they constantly receive from the latter data and time-frames in order to work on each specific product type in an appropriate way.
  • These machines are predisposed, through their processing unit, to provide a whole series of information to the Quality Control Management and, where necessary, to the management system, contributing to the analysis of several production processes and their performances.



Checkweigher: production benefits



As we have seen, a modern automatic in-line weighing system provides remarkable advantages: precise control assurance, guarantee of compliance with current regulations, ability to transmit data to central management systems. Let’s now see some of the benefits specifically related to the production area:

  • The verification of the type of defectiveness of rejected products, either underweight or overweight, makes real-time intervention on the process possible, thus reducing the number of defective units and gaining in productivity.

  • An automatic checkweighing system allows to constantly monitor the trend of the “average filling time”. This basically means avoiding production wastes, typical of automatic packaging lines, therefore gaining in terms of performance and profit margin. In fact, the checkweigher can automatically regulate the upstream filling system (feedback function). Dosage adjustments could also be made manually, but this would inevitably generate the sinusoidal oscillation of the weight, forcing the operator to chase after the weight value which, with no regular frame rate, goes from positive to negative and viceversa, without ever stabilizing. An automatic system, on the contrary, acts on the dosage regulation with a suitable algorithm, both in case of positive and negative drift, making proportional adjustments on the mean error and bringing the filling weight value to “error zero”, keeping it constant over time and therefore eliminating wastes and rejections due to overdosing/underdosing.

Checkweighers are not only used to verify the equivalence between the weight value stated on the label and the value actually observed, but can also be employed for internal process controls.


  • Dosing several ingredients in a single package often causes issues: the values declared on the label must be respected. Automatic dosing systems are becoming more and more reliable, but they are still affected by the type of product to be treated. There is a need, therefore, for installing, after each dosing machine, a checkweigher that is able to automatically verify the dosage and make necessary modifications (feedback).
  • Completeness check: it is made on packages which contain multiple units. Single product units can be of a same type (as in classic “multipack” formats, frequently used in food industry), or include different kind of products in a carton box, at the end of the line, which is common to all sectors, from food to pharmaceutical, from chemical to cosmetic, beverage, DIY and many others. Imagine being the final consumer, who has a little home improvement to do on a weekend: how would you react if, opening the assembly kit box, you realized that one component is missing? Completeness check, through weight control, protects the manufacturer from the costly claims of final users and large retailers.



Checkweigher: areas of application



We have observed and highlighted the importance of weight control, but also the possibility of turning this cost into an investment thanks to the use of a checkweigher, an automatic system that checks 100% of production, guarantees product’s quality and, at the same time, provides a series of useful data in real time, in order to analyze and manage the production line.

Therefore, talking about sectors of application is really simple: all those that offer packed products on the market. All the food industry, of course, but also the cosmetic, chemical, pet food and DIY ones, without forgetting the pharmaceutical sector, where completeness checking is of primary importance in order to market the final product (leaflet presence, check of right number of blisters/capsules, verification of the presence of all components of a kit, etc.).

For each one of these applications, very specific and reliable tools are needed: the answer is represented by the solutions offered by Pen-Tec, a modern, innovative structure, that has made research and development in the control systems field its own mission. The numerous applications implemented and our customers satisfaction allow us to be recognized on the market as an expert and qualified partner.



“Quality” in an increasingly demanding market



The market and final consumers are becoming more and more attentive about what they purchase: health safeguard depends on what you eat, among other things. For this reason products quality is a mix of several elements: from raw materials to the way they are treated at industrial level, from product’s image to the impact the packaging has on the environment. The “weight guarantee” is only one of many components that, altogether, make up the “quality” of a product. In fact, in terms of safety, the consumer wants to be reassured on the absence of contaminants and foreign bodies as well. The quality check plans carried out by certification authorities provide for a wide range verification, which takes into account various aspects of the overall quality of products and production processes. Moreover, we can’t forget about the extremely negative effects on a company’s brand due to claims from consumers who suffered damages caused by foreign bodies in their food.

Pen-Tec has taken care of this concern, investing in technological research with the aim of responding to this primary need. Our proposal takes shape in a full range of solutions in the field of product inspection and in-line control.




  • Checkweighers, that we have already described, with a wide range of machines suitable for many different applications and complying with international metrology regulations (e.g. MID).
  • Metal detectors, equipped with conveyor and rejection system, and able to operate on different types of products, from fresh to frozen.
  • Integrated solutions with checkweigher and metal detector, which combine two functions in a single framework, guaranteeing a double control on packed products.
  • X-Ray inspection systems, provided with the most cutting-edge technologies: able to check the presence of foreign bodies of various type (high-density plastic, metal, stone, glass, high-density rubber, bones, cement shards, etc.) and applicable to any kind of packaging, including aluminized or metalized films on which metal detectors are unable to work. They are low-power and low-emission tools, have zero impact on the environment and do not require medical supervision on the line.

  • Finally, the greatest revolution in the field of product inspection: the integrated unit that combines checkweigher and X-Ray inspection system. A highly innovative product designed by Pen-Tec (we have reached the 5th generation), being aware of the issues that companies commonly encounter on production lines. The Combi machine has indeed extremely limited dimensions, whilst remaining loyal to the fundamental principles of compliance with legal metrology requirements (the weighing system is MID-certified) and environmental legislations.
  • All of our solutions meet Industry 4.0 requirements: they are able to communicate with the company’s centralized system in a bidirectional way, providing a continuous flow of information on production status.
  • The low degree of maintenance needed, result of a careful and innovative design which uses the highest level components, the great value for money, the high level of performance and efficiency, make Pen-Tec solutions the ideal working partner, reliable and relentless.



A choice that becomes investment

The Pen-Tec’s technical and commercial team bring their 20-year expertise on the market, result of the experience gained from many applications that obtained the highest satisfaction of our customers, who continue to renew their trust in our activity.

We are on your side to understand your need and provide you with the most appropriate solution for the best price, motivated by the will of having your company among our faithful clients, because the choice of a partner must be an investment.


Find out our inspection systems:

Automatic weighing systems, Checkweighers, automatic scales: Checkweigher

X-Ray inspection systems: X-Ray product inspection

X-Ray inspection and Checkweigher integrated version: Combi X-Ray + Checkweigher

Detection and inspection systems with Metal Detector technology: Metal detector

Metal Detector and Checkweigher integrated version: Combi Metal Detector + Checkweigher


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