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Not a single ounce too much

The ideal drive for weight controllers.

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 GmbH, 'Groschopp'-motors with integrated electronics ensure a continuous flow of conveyor-belts.

Any manufacturer would avoid a conflict with consumer protection law, neither having any incorrect quantities, not to mention dissatisfied customer. Even overfilling is undesirable. it couldn’t only overstrain the packet, but would also mean enormous extra cost. For example, if just 0.5 g is filled over and above the stated weight, it would cost the producer a six-figure Euro-sum per year, when considering 0.37 Eurocent per gramme in a production-line having a through-put of 200 products per minute and working 3 shifts per day for 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 has been combined in 1986 as part of the Mettler Toledo-Group. In this group, Garvens is part of the Product Inspection Division, together with  affiliated company Safeline for metal-detection and X-Ray-inspection.

Garvens XE2 checkweigher

The XE2 checkweigher is a modular system of Garvens, which at under different production conditions can be fit-image: Mettler-Toledo Safeline GmbH

Garvens XE3 checkweigher

Variable conveyor height, direction and infinitely variable speed change for items up to six kg weight are the characteristics of the XE3 checkweigher from Garvens
Image: Mettler-Toledo Safeline GmbH

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, 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 ambiences with a very high dust content. There are three different kinds of weight controller -conveyor-belts: feeding-, weighing- and hauling-off conveyors – separate designs which are driven individually by their respective drive. A controller unit synchronizes all three drives. The transport belts are made of synthetic material, easily cleaned and allowing the products neither to slide nor to stick too much to 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 integriated electronics and transmitter-system stands as 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 are about 200 weighing cycle-operations per minute. The dynamic weight controllers are smoothly integrated into the production- and packing-processes in order to guarantee an economical 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 great 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 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 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 made by Garvens can be integrated into various production processes due to their flexible design catering for variable transport heights and infinitely variable speed adjustment. Needless to say, 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 continious speed control. With its integrated complex analysis model, the electronic ensure a smooth running which isn’ t only important for the steady-going of the three weighing belts, 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, symbolic instructions. The drives are connected with the respective Plc, using either a Can-Bus- or a serial interface. Beside the weight controllers Garvens provides software-modules for statistical analysis related to quality control and 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 subject to the highest demands upon 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.

Well-balanced drives

Running characteristics and a compact-built housing with integrated electronics speak for the drives made by Groschopp. Special attention is hereby placed on the efficiency of the motor, since the possible operation temperature depends on the resistivity of the electronics, and especially due to the characteristics of stainless steel in respect of heat dissipation aren’t so favourable. Groschopp found a solution to these problems by placing the winding around the tooth, 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 considerably 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 in 24 (optionally 48) Vdc and with an 8-pole connection plug. The motor types available within this 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, a glueing-joint, may be corroded by cleaning chemicals and hence, are unsuitable. Such detail shows the high-quality make which justifies the protection class IP69k. With the EGK48-60NV (REA/EAA)-motor, made by Groschopp AG, 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 market-leading producer Mettler-Toledo Garvens GmbH, which are used in all produktion spheres.

The roots of the Groschopp AG go back as far as the 1920’s with their commence-ment of manufacturing electric motors in Saxony. Now there is a more than 230 strong staff employed in the town of Viersen, Northrhein-Westfalia, engaged in the development and manufacturing of motors and gears. A major business of the company is the development of customer-tailored drives and their integration into their respective application.

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