On food and pharmaceutical production lines, as elsewhere in life, the smallest expenses can soon add up into something insurmountable. Even seemingly trivial errors in portion sizes on filling lines can result in costly levels of product waste, making the installation of advanced checkweighing systems crucial to keep waste to a minimum and maximise manufacturing output.
Dirk Bettels, Senior Product Manager at global checkweighing manufacturer, Mettler-Toledo Garvens, answers our questions about how to ensure optimum efficiency.
PhM: What do we, the customer, need to consider at the specification stage?
DB: First of all, you and your checkweigher supplier need to develop a fully common understanding of your application. This means full comprehension about the product characteristics, its behaviour and then the environment the checkweigher will be operating in. Humidity, high temperatures, and airborne dust can all impact weighing precision, while moisture and dust can age the system, before its time, by damaging the conveyor belt or weigh cell. Choosing checkweighers with sealed casings, milled from a single piece of plastic or metal, and sloped surfaces, to allow water to run off more easily during cleaning, can help overcome these issues. They can prevent particles or moisture getting into the system, protecting the delicate mechanisms within.
PhM: What disturbances affect the performance of a checkweigher?
DB: There are a number of considerations to take into account, for example, some weighcells are not suited to handle high moisture and temperature fluctuations. Debris and dust falling on and around the weighing section can offset the zero setting of the checkweigher. It is also important to limit draughts, noise or unwanted signals, excessive movement and electrical noise near the checkweigher. Tiny vibrations can be picked up by the checkweigher, potentially distorting the accuracy of measurements. These problems can easily be prevented by training staff to make simple precautions, thus ensuring precision weighing.
PhM: How does the type of product impact the choice of checkweigher?
DB: When choosing the type of checkweigher, you need to take into account the nature of the product. In addition, it is important to think about packaging format, height, weight, and whether the product is solid, powdered or liquid, as these will potentially affect pack stability in transit, potentially impacting weighing accuracy.
The most important element though is effective product handling. This ideally means that the product is smoothly transported along the checkweigher. Choosing the right product handling options, such as guide rails, will help to optimise product transfer. In addition, the products should be evenly spaced, as improper timing of items potentially results in inaccurate rejection of products due to spacing errors. Installing timing belts, screws or wheels can help to ensure each pack is correctly spaced so that only one at a time passes over the weigh cell. Side grips and transfer units can also keep the packs stable thus making certain that the weight is evenly distributed, therefore increasing weighing accuracy.
The nature of the product will affect the choice of conveyor as well. Granulate foods, such as salt, flour or sugar, can cause corrosion damage to the conveyor belt over time, especially if the mechanism is not cleaned properly. Small trapped particles within the system can cause friction between the moving parts, affecting the machine’s performance. Selecting a checkweigher with a conveyor specifically designed to accommodate powdered products where the belt is fully encapsulated, accompanied by minimal openings within the entire system, where grains could enter the machinery, will reduce the need for maintenance and ensure optimum weighing accuracy.
PhM: Does the type of product affect the choice of rejecter?
[wp_ad_camp_4]DB: The product and its packaging will need to be considered when choosing a reliable rejection device. For example, a simple air jet rejecter can be used for small, sealed packs, but large, open containers may require a sweep-off rejecter. Checkweighing suppliers provide a wide range of different reject solutions. Ultimately, choosing the right reject device will ensure the best process safety and overall performance.
PhM: What role does the checkweigher set-up play and how can we ensure the system is set up properly?
DB: Setting up the checkweigher correctly – ensuring products are not over- or under the target weight – is critical to the success of your technology purchase, as it not only ensures you meet weights and measures regulations, but also reduces wasteful product giveaway. To guarantee that the average weight of your product batch is within legal limits, your target weight should be slightly above that stated on your packaging label. Precision checkweighers will let you set tighter tolerances, above and below your product’s target weight, allowing you to further reduce giveaway and minimise the risk of underweight products reaching consumers.
You should also make sure your checkweigher has been fitted according to the weights and measures legislation governing your target markets. To comply with the European Union’s (EU) Measuring Instruments Directive (MID) for instance, your equipment supplier should get an assessment of their checkweigher from an independent metrology certification body. The manufacturer though, is responsible for making sure the original test products are available on site indefinitely for future testing and verification.
PhM: What else can help making sure the production line performs properly?
DB: Innovative data monitoring software is a must for any manufacturer to help them incorporate the checkweigher with the rest of the line’s product inspection equipment. From a checkweigher view, scalable communication levels help to satisfy customer requirements. This starts with simple weigh data communications to complete data acquisition and management software. These tools enable manufacturers to identify consistent product over- or underfill and locate the source of the error. Feedback control functions can alert your filling machines earlier in the production line to any adverse filling trends, allowing them to adjust portions to rectify the issue and reduce the future incidence of costly product giveaway.
PhM: How important is operative training?
DB: In a word: crucial. Trained staff will help you to avoid weighing errors due to improper set up or even from physical damage. Every machine operative should receive basic training on the system software as well as appropriate care and maintenance of the machine and conveyor. An understanding of correct product set up and changeover procedures should be communicated to every operative, as well as that for false rejections or unexpected machine stoppages.
PhM: Where can operatives get this training?
DB: Many checkweigher manufacturers offer support for food manufacturers to enable them to optimise checkweighing accuracy on their lines. At Mettler-Toledo, for example, we provide extensive training for machine operatives through our Product Inspection Training Course. This is designed to help operatives understand the capabilities of their checkweighing and other product inspection technologies, and how to operate them effectively.
[wp_ad_camp_3]PhM: Would you recommend setting up a monitoring protocol?
DB: Yes I would – periodic monitoring of the checkweighing system can help you identify and put right any issues that could affect weighing sensitivity and line efficiency, plus identify and rectify them as quickly as possible. You should ensure line operatives are trained to pay attention to the system’s output so that any differences in weighing accuracy are spotted as early as possible. A regular vision inspection routine should also be put in place. This will identify any problems and enable you to put the corrective action into effect as quickly as possible.
PhM: Is there anything else that manufacturers should put in place to ensure weighing accuracy?
DB: Manufacturers should establish a regular performance testing programme to guarantee accurate weighing. Atmospheric changes can affect weighing accuracy, so it’s vital that the weigh cell’s sensitivity is regularly checked to minimise the risk of false rejects and help prevent overweight products from continuing on the production line.
Standardised procedures in the event of a weighing error should be implemented as well. Operatives should know what to do and be able to respond quickly, to minimise disruption to the production process.
PhM: What advice can you give regarding maintenance?
DB: If a component on your checkweigher begins to wear over time, early detection is vital to protect production uptime, which can be identified through internal diagnostic tools. You should always undertake preventative action to replace worn components, such as conveyor belts, before they cause a malfunction, with rectification been carried out by operatives.
PhM: Do you have any tips for testing?
DB: You should definitely implement regular testing procedures of your checkweighing system to monitor performance, as well as scheduled service intervals with the technology supplier’s technicians to test the precision of your system’s weigh cells. Between these service intervals, you can also ‘self-test’ by passing a packaged product of an established weight several times through the checkweigher to monitor the system’s performance. Modern checkweighers feature easy-to-use Human Machine Interfaces (HMIs) that allow quick, straightforward recalibration of the weigh cells and rejection criteria, enabling you to correct many problems yourself.
To demonstrate due diligence and compliance with legal metrology regulations, you should ensure that all testing and maintenance records are comprehensively logged as proof of good practice.
PhM: What other advice can you give?
DB: Ensuring the product is the correct weight is not just about complying with legislation, but safeguarding product quality as well. The reputation of your brand depends on the correct checkweigher specification for your production line, and on the maintenance and monitoring procedures you set in place after it is installed.
As such, before making a purchasing decision, you should seek guidance from checkweighing experts. They can offer support on system selection and set up, as well as training and maintenance. This advice will ensure your production line benefits from minimised downtime due to unscheduled repairs and reduced costly product giveaway, maximising efficiency and profits, allowing your brand to grow.
About Dirk Bettels, Senior Product Manager
Dirk Bettels has been working for Mettler-Toledo for over twenty years. In that time, he has been responsible for the company’s electronic developments and, for the past seven years, has held the position of Senior Product Manager for checkweighing and checkweighing combination machines, such as metal detection, x-ray, marking, vision and labelling devices.
Due to his extensive experience in industrial automation, he is one of the driving forces behind Mettler-Toledo’s innovations. He introduced the first x-ray checkweighing combination machine to the market, as well as the inaugural serialisation stand-alone machines. More recently, he developed the XS2MV TE, 4 in 1 serialisation station, with marking, camera inspection, tamper evident sealing and checkweighing on a footprint of below 2m.
Mettler-Toledo Garvens is the world’s leading supplier of checkweighing solutions for the food and pharmaceutical industries. Together with Safeline, CI-Vision and Pharmacontrol Electronic GmbH (PCE), Mettler-Toledo Garvens forms the Product Inspection Division of Mettler-Toledo.
Mettler-Toledo develops, produces and sells precision instruments worldwide. The company is one of the largest suppliers of weighing systems in the world, whose high-quality products are used in laboratories as well as industrial and pharmaceuticalretailing applications. Renowned producers of all conceivable everyday products rely on Mettler-Toledo’s weighing technology as an important aid to product development. These producers reap the benefits of the global company’s innovative products and global presence.
Mettler-Toledo’s corporate philosophy centres around quality and tailored solutions. The company forms a true partnership with its customers, working together to develop unique solutions, providing support during the selection of appropriate systems and offering a reliable service.
For general information on Mettler-Toledo Product Inspection, visit: http://www.mt.com/pi.