As consumers we rely on the data given on packagin: we trust that it contains the stated quantity, whether it be washing powder or icelollies. 500 g or 12 pieces – whatever is marked on the packet, we are willing to pay for and we expect to find that the contents match.. Any manufacturer wants to avoid conflict with consumer protection laws, neither having any incorrect quantities, not to mention dissatisfied customers. Even overfilling is undesirable as it not only strains the packet, but also causes enormous extra cost. One way to ensure this is to use weight controllers directly integrated into fully automated packing process lines.
Garvens, located in Giesen, Lower Saxony, is a leading manufacturer of dynamic weighing-techniques and became a member of the Mettler Toledo-Group in 1986. Garvens forms the Product Inspection Division, together with the company Safeline for metal-detection and X-Ray-inspection.
Exposure to water and other cleaning liquids are a common daily occurrence in foodstuffmanufacturing industries. The checkweighers’ models XE- and XS, made by Garvens, are available in the highest-possible International Protection class IP69K, which means that they can be used in wet operations or in surroundings with very high dust content. There are three different kinds of conveyor-belts in a checkweigher: for feeding, weighing and removal. These separate, individually driven constructions are synchronised by a controller unit.
The transport belts are made of synthetic material, easily cleaned and the products will not slide or stick on it. The core of the belt is made of aluminium or corrosion-resistant V2A-stainless steel. The choice of material for the application depends on the required degree of protection. Garvens uses the housed motor EGK48-60NV (REA/EAA), made by Groschopp, for the XE2 and XE3 checkweighers. This motor with its integrated electronics and transmitter-system is a completely separate direct drive. The model XE2 is designed for a weighing range of up to 600 g, while articles ten times heavier can be processed using the bigger XE3 model.
Precision is guaranteed even at the maximum load of 6kg. The through-put of these stations reaches 200 weighing cycleoperations per minute. The dynamic checkweighers are smoothly integrated into the production and packaging processes in order to guarantee quality assurance and control. Motors with integrated electronics are especially suitable as their design allows for a minimum of wiring and they fulfil the demands of a decentralized automated system.
The customer has a choice between the square-shaped housing made of aluminium (EAA) and the corrosion-resistant round housing (REA) made of electro-polished stainless steel with very smooth surfaces without any protruding screws or welding seams. This latter model renders any accumulation of dirt almost impossible, while at the same time it is compact-built and not too heavy. The round stainless steel version was developed especially for the food sector. The upgrading of the protection class from the IP65- standard to IP69K is achieved by using different seals around the plug. The housing as such remains unaltered. The covers also serve as cooling elements, ensuring the necessary temperature dissipation. Heat dissipation is always a very important and critical aspect when choosing stainless steel in order to obtain the necessary output without any losses.
Checkweighers XE2 and XE3 by Garvens can be integrated into various production processes due to their flexible design catering for variable transport heights and speed adjustments. The drive must match this flexibility and be compatible with different controller units and/or interfaces. The integrated control system of the EGK-motors is advantageous for a continuous speed control. The electronics ensure a smooth running, important for the continuous transport over the three belts of the checkweigher, but also for the transfer to the production conveyors.
The operation of the checkweighers during the process is done via a touchscreen with user-specific symbols. The drives are connected to the corresponding PLC using either a CanBus- or a serial interface. Garvens also provides software modules for statistic analysis related to quality control, which can also be connected directly to the ERP system. The devices are analytical mechanisms which enable 100% control of production targets, thus need to fulfil the highest demands on the precision of all installed components. The checkweighers can also be connected directly to the batch control.
Running characteristics and a compact housing with integrated electronics are arguments in favour of the drives made by Groschopp. Special attention is paid to motor efficiency, since the allowed operation temperature depends on the resistance of the electronics. Furthermore the unfavourable characteristics of stainless steel in respect to heat dissipation have to be taken into account. The efficiency of the motors is considerably enhanced using the concentrated winding technique. The EGK-types with integrated controller are offered for 24 (optionally 48) VDC supply voltage and with an 8-pole connection plug. The motor types available range from EGK48 to EGK120. The checkweighers by Mettler-Toledo Garvens are used in all sorts of production spheres, helped by the EGK48-60NV (REA/EAA)-motor which combines powerful electronics and high efficiency