As customers we rely upon a given data on a packet: we trust that it contains the stated quantity, whether it be washing powder or ice-lollies. 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 so marked match exactly what is in the packet. One way to ensure this is to use weight controllers directly integrated into fully automated packing process lines. In weight controllers of the X-series made by Mettler-Toledo Garvens, Groschopp motors with integrated electronics ensure the continuous movement of the conveyor belts.
Any manufacturer would avoid a conflict with consumer protection law, neither having any incorrect quantities, not to mention dissatisfied customers. Even overfilling is undesirable as it not only overstrains the packet, but also causes enormous extra cost. For example, if just 0.5 g is filled above the stated weight, it will cost the producer a six-figure Euro sum per year with a given price of 0.37 Eurocent per gramme in a production line having a through-put of 200 products per minute and working 3 shifts a day on 230 days per year. That is why precise weight controllers are needed, such as Garvens offers in their product programme. This enterprise, located in Giesen, Lower Saxony, is a leading manufacturer of dynamic weighing techniques and became a member of the Mettler Toledo-Group in 1986. In this group, Garvens forms the Product Inspection Division, together with its affiliated company Safeline for metal-detection and X-Ray-inspection.
Extreme strains from water and other cleaning liquids are a common daily occurence in all foodstuffs manufacturing industries. The weight controllers’ models XE and XS are available in the highest-possible International Protection class IP69K, which means that they can be used in wet operations or in surroundings with a very high dust content. There are three different kinds of conveyor belts in a weight controller: for feeding, weighing and hauling-off there are separate, individually driven designs. A controller unit synchronises these three drives. The transport belts are made of synthetic material, easily cleaned and having the products neither sliding nor sticking on it. The bodies of the transport belts are 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 weight controllers’ models XE2 and XE3. This motor with its integrated electronics and transmitter system is a completly 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. A high precision is guaranteed even at the maximum load of 6 kg. The through-put of these stations reaches 200 weighing cycle operations per minute. The dynamic weight controllers are smoothly integrated into the production and packing processes in order to guarantee an economic quality assurance and control. That is why motors with integrated electronics are especially suitable, on account of their design needing a minimum of wiring which, together with the high protection class, offers advantages for the conveyor technique, especially since the design often demands 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 having 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 new round stainless steel version was developed especially for the food sector. The upgrading of the protection class from the IP65 standard make 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 on account of their material. Heat dissipation is always a very important and critical aspect when choosing stainless steel in order to obtain the necessary output without any losses.
Dynamic weight controllers
Weight controllers XE2 and XE3 can be integrated into various production processes due to their flexible design catering for variable transport heights and infinitely variable speed adjustment. The drive must also match this flexibility and must be compatible with different controller units and/or interfaces. The integrated control system of the EGK motors is especially advantageous for a continuous speed control. With its integrated complex analysis model, the electronic ensure a smooth running which is not only important for the steady-going of the three weighing belts in the feeding, weighing and hauling-off conveyors, but also for the transportation to the various production belts.
The operation of the weight controllers during the automated process is done via a touchscreen with user-specific instruction symbols. The drives are connected to the corresponding PLC using either a CanBus or a serial interface. Beside the weight controllers Garvens provides software modules for statistic analysis related to quality control, which can also be connected directly to the ERP system. The devices have first-class analytical mechanisms, enabling product aims of a 100 % controlled monitoring and fulfil the highest demands on the precision of all installed components. The weight controllers can also be connected directly with the controlling system for the monitoring of various filling capacities.
Running characteristics and a compact housing with integrated electronics are arguments in favour of the drives made by Groschopp. Special attention is placed here on the motor efficiency, since the possible operation temperature depends on the resistance of the electronics. Namely the characteristics of stainless steel in respect to heat dissipation are rather unfavourable. Groschopp has found a solution to these problems by placing the winding around one single tooth, a technique which is also used in the basic model Black Panther Servo. The winding is hereby placed around the tooth and the cogging torque is notably reduced due to its winding around the slanted teeth. The efficiency of a motor is enhanced using this winding technique, which can be positively seen on housed motors with integrated electronics. Customer-tailored requests can be realized with this winding, which is manufactured in a fully automated process at Groschopp in Viersen.
The EGK types with integrated controller-electronics 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 and can facilitate most of the popular applications. In the stainless steel version the high-class manufacture can be noted when looking at the joint between housing and plug adaptor, which is laser-welded. This is quite a complex method on a round housing, leaving a smooth edge, which prevents any accumulation of dirt. Other methods of attachment, e.g. glueing may be corroded by cleaning chemicals and hence, are unsuitable. Details like this show the high quality make which justifies the protection class IP69K. With the EGK48-60NV (REA/EAA) motor there is a housed motor available combining effective electronics and high efficiency, as can be seen in the application of dynamic weight controllers of the manufacturer Mettler-Toledo Garvens, which are used in all production spheres.