The purpose of loss-in-weight feeders is to fill an exact quantity of a product into provided packaging units such as boxes, cans, bags, glasses or cups. At the same time, this process should be as fast and accurate as possible. A dosing scale must therefore be adjustable to a certain target weight. Weighfeeders are also sold under the names filling scale, multihead weigher, combination weigher, partial quantity weigher or in English as Multihead Weigher and Combination Weigher.
The operating principle of weighfeeders is based on the automated distribution of an exact quantity of product, usually bulk material, into the appropriate container. Depending on the design of the scale, the weighing containers to be filled are arranged in a circle and are filled via storage containers located above, or they are led one by one to the filling station, for example via a dosing belt. By contrast, manually operated filling scales allow slower but very precise and easily correctable filling.
Liquids and pastes can also be filled using such scales. This usually works by means of a combination system with a pump that delivers the desired filling quantity from a tank into the container. In order to prevent product agglomeration, there are dosing scales whose function can be manually intervened if necessary. To facilitate product distribution from the hopper to the weighing hoppers, additional techniques such as vibration, coreless screws and different types of conveyor belts are used.
Fields of application in weighing technology
The main field of application for weigh feeders is large production plants, especially in the food industry. There, originally easily movable individual products such as peas, crackers and the like were allocated to their packaging units via multihead weighers. Today, improved technology has made it possible to package rather bulky or sticky products such as meat, poultry, salads and accessories for ready meals using weigh feeders. Furthermore, granulates, coffee, tea and similar fine-grained or powdery luxury foods as well as products at risk of breakage such as biscuits and pastries can also be weighed with specialized dosing scales. In addition to the food industry, pharmaceutical companies, manufacturers of dental products and cosmetics manufacturers in particular use weighfeeders. The great advantage of weighfeeders is the programmable control and automation of packaging processes.
Which models for which purpose?
Different models of weighfeeders are available depending on the intended use. For example, so-called gravimetric weigh feeders can either measure fill quantities as a batch or set a mass flow constant over time. They usually consist of several components: a volumetric precision feeder (spiral feeder, vibratory feeder, belt feeder or liquid pump) and a weighing unit (platform, hybrid, frame or belt weigher). The desired dosage can be freely selected within a given control range for all models.
With the differential dosing unit, the individual components are suspended in a frame or container. Here, the weighing unit works closely with other functional units such as dosing screws, rotary valves and conveyor belts. The advantage of the weigh feeder with differential is a very good filling flow dosing, independence from the respective filling level and lower susceptibility to external influences.
So-called micro-dosing units are suitable for use in laboratories or similar facilities, since very small quantities often have to be weighed precisely in these areas. Granulates, powders and similar substrates can be dosed with high accuracy and continuously weighed.
Dosing scales without verification are not suitable for use in commercial operations because they do not have an official type approval and therefore dosing consistency cannot be guaranteed. We therefore recommend that you use only models with a verified verification certificate.