Precise weighing reduces raw material waste and product defects, boosting profitability. It also allows companies to meet customer expectations for quality and safety.
Choosing the right weighing process depends on precision requirements and material characteristics. Often, direct weighing is a convenient and economical option when accuracy isn’t critical. But there are other options for more demanding applications.
Pre-weighing
A pre-weighing process can dramatically reduce cycle times for high speed bulk bag filling machines. Adding a hopper above the bulk bag filler and weighing the payload before it flows into the bag eliminates the need to weigh the product at the filling machine. This allows for maximum bulk bagging rates to be achieved.
Typically deployed in the MAKE and PACK manufacturing areas for “gain in weight” and “loss in weight” applications e.g. 2% to 10% of full scale capacity.
By weighing the product in a separate container prior to transfer into the vessel, this method of weighing can avoid problems such as taring errors. By subtracting the weight of the weighed material from the weight of the empty container, weighing by difference is an efficient and clean way to achieve accurate dispense results. Automated systems also log data, which can be reviewed and analysed to improve production processes, and can integrate seamlessly into existing batch manufacturing protocols. This enables seamless audits and quality assurance, ensuring compliance to set manufacturing standards.
Balance validation
Performing a regular set of tests on your analytical balance or scale is critical to ensure consistent results and to identify any issues with your equipment. These issues may include calibration drift, equipment problems or even environmental conditions that influence how the device operates (e.g. temperature changes).
The most important properties to test during a performance qualification are sensitivity, linearity and eccentricity. They account for systematic deviations that limit the accuracy of the device.
To assess sensitivity, you need to weigh the same weight several times and calculate the mean measurement. You also need to check the standard deviation of the measurements by calculating their square root.
Linearity error can be tested by weighing two sub-sets of weights with a total mass that is equal to half of the maximum capacity of your balance. The mean measurement and the relative standard deviation should be within a certain tolerance. The number of weights and the frequency of these tests can vary depending on the type of instrument.
Calibration
Calibration is an essential process that ensures test and measurement devices are working correctly. Whether it’s your car or airplane, your medication or food safety, the precise measurements assured by calibration are all around us every day.
A balance must be calibrated with a standard weight before the first use and on a regular schedule thereafter to maintain accuracy. This can be done at a national laboratory, through an accredited service provider like Fluke, or within a customer’s own laboratory.
A balance should be stored in a draft-free environment on a stable bench, away from vibrations. It should also be kept at a constant temperature. Weighing papers should be changed periodically and hygroscopic materials handled quickly. When a calibration is performed, it’s important to follow the manufacturer’s recommended procedure. In general, recalibration is triggered when a device’s verification measurements are outside of its engineering tolerance. This could be based on the frequency of use, or after a shock.
Integration
Weighing processes can be integrated into automated systems to improve efficiency and accuracy. But this transformation requires a carefully planned approach to ensure that it is implemented correctly and delivers on its potential for business growth.
The user-friendly interfaces of automated weighing systems reduce the traditional learning curve and enable new staff to get up and running quickly. Moreover, the system manages most of the complexities involved in ensuring accuracy and can easily diagnose issues. This accelerates onboarding, enabling businesses to meet production targets more effectively and efficiently.
Process weighing systems use the difference between the weight of material on and off the scale to calculate mass flow rates. However, plant and manufacturing noise can interfere with these readings, so it’s important to use instrumentation that can filter out environmental interference. This guarantees exceptional accuracy, even during high-speed process applications like blending and filling. This also reduces waste and raw material loss, contributing to improved profitability.