Ready For The Future - Mitschke Expands Material Conveying System

The company's significant increase in turnover and existing structures typical of a medium-sized company – in this case, in particular respecting its material conveying system – caused the production division of Mitschke GmbH & Co. Kunststoffwerk KG, based in Eggenthal, Southern Germany, to gradually reach its limits. In order to meet this increase in turnover, Mitschke had been buying a new large-scale machine every year for the past three years. Its annual material throughput eventually reached about 4,000 tons of different engineering plastics. These plastics include countless speciality products comprising up to 30% talc, glass beads, short and long glass fibres with a fibre content of up to 50%. Further, Mitschke processes around 1000 tons of the latter a year alone. 

The company operates 17 injection moulding machines with clamping forces of between 450 and 32.000 kN in two production halls. Its product range comprises technical parts for agricultural machinery and car manufacturers, for both exteriors and interiors, enclosures, panels and large fans. The weights of the injection-moulded parts it produces range from 25 to 30,000 gram and are produced at cycle times of 25 to 240 seconds. The moulded parts' dimensions of up to 1,800 x 1,800 mm are equally impressive. The company's injection moulding shop, assembly hall and tool making workshop are housed in an area totalling 5,000 m², which is connected to a 6,000 m² storage space. Operating over 3 shifts with its 160 employees, Mitschke generates an annual turnover of around 30 million Euros. 

In part, it was this significant increase in turnover that caused Mitschke to eventually decide to completely revamp its material conveying system, from the material loader, the decentralised and central drying systems, right down to the entire conveying system used to supply the machine park with material. Added to that, Mitschke also decided that the dust created by the highly filled materials needed to be contained and that the future system should be more energy efficient. The machines are supplied by 12 external silos as well as a twin-design big bag station specially designed by Motan-Colortronic. 

Mitschke and Motan-Colortronic have been collaborating since the 1990ies. Between them, the long-standing partners designed a central drying system with two Luxor A900 dry air generators as well as six Luxorbin drying hoppers with a capacity of 1,800 litres each, which were installed on a specially designed platform. The new system furthermore included an ETA Plus air volume control, a dew point control unit and a water cooler for the regeneration air. 

One of the two dry air generators comprised an existing rather than new one. This generator has been connected to a new controlled drying unit, whose air performance varies between a minimum of 30% and maximum of 100% depending on the current throughput or demand rate, which supplies the drying hoppers with dry air. Connecting this unit required a number of changes to be made to the control technology and the associated piping. The concept overall is designed in such a way that it can be expanded by additional dry air generators and drying hoppers. The system is furthermore located in a central location between the two halls, thus allowing material to be fed into the system on a demand basis. The drying system's control system has been integrated into the company's network and can be centrally monitored by the production management.

The process air is controlled by the ETA Plus system, which analyses and controls both the individual process air requirements of the individual drying hoppers as well as that of the entire system. This means that each drying hopper is only supplied with the amount of dry air required to achieve and maintain the required material conditions. If the control system detects that the material in the hopper has been fully dried, it will reduce the flow rate, heat output and the total air output. This ensures that the system will always operate at its optimum performance level. The integrated Drying Organizer furthermore automatically detects drops in the material throughput rate and gradually reduces the drying temperature to the optimum stand-by parameters. This again saves energy and protects the material from thermal damage.

Since it is not possible to eliminate all of the dust associated with some materials, the hopper conveyors as well as some of the machine conveyors were built using filterless conveying systems (Metro HCG) from Motan-Colortronic Metro G-series. These conveying systems are specially designed for processing abrasive materials and are fitted with special abrasion resistant valves for this purpose. The filterless conveyors' have spacers fitted above their material inlets, which contributes to the system's capacity to extract as much dust and, for example, loose glass fibre particles, through the vacuum line and into the central filters as possible. 

In order to prevent the interior of the material lines from becoming abraded, in particular inside the bends, Mitschke has fitted all of them with glass bends with a PU coating. The PU coating is applied to the outside of the bends. It keeps broken glass in place and prevents it from posing a hazard to personnel in the event of damage.

The material conveying system utilises a line vacuum. The material is conveyed from one of the 12 silos, depending on the source, to the drying systems and, from there, to the machines via a coupling station. This makes it possible for every drying hopper to supply any of the machines with material. The longest conveying line in the production facility is 270 metres long. In addition to the silos, the facility also features an alternative material source, which comprises a twin-design big bag station. This station and the associated control system has been specially developed for Mitschke by Motan-Colortronic. The base of the big-bag system has been fitted with a sensor (rotary paddle bin level indicator). If one of the stations is empty, the control automatically switches to the second station, thereby ensuring uninterrupted material supply over long periods of time. At the same time, the control also triggers a warning light when a new big bag is needed. If the bag hasn't been changed within 30 minutes, it will sound an alarm to ensure that it is replaced in time. 

The material conveying system is distributed over four vacuum circuits capable of conveying up to four tons of material per hour between them in line with the consumer points' (machines) capacities. Two of the vacuum circuits are connected to a 7.5 kW side channel blower each. The vacuum lines for supplying the large machines have a diameter of 76mm and the associated material lines a diameter of 60mm. This allows each circuit to convey as much as approx. 1250 kg/h of material respectively. The third vacuum circuit features a vacuum line with a diameter of 60mm and a material line with a diameter of 50mm, which, coupled with a 5.5 kW claw compressor, allows it to convey up to 850 kg/h. The fourth vacuum circuit, both the vacuum and material line of which have a diameter of 50mm, also features a 5.5 kW claw compressor, which allows it to convey up to 650 kg/h. The compressors are housed inside a container outside the production area in order to minimise noise. 

The motan-group

The motan group based in Constance was founded in 1947. As leading provider for sustainable raw material handling, they operate in the areas injection moulding, blow moulding, extrusion and compounding. Innovative, modular system solutions for storage, drying and crystallisation, conveying, dosing, and mixing of raw materials for the plastics manufacturing and processing industries are part of the application orientated product range. Production takes place at different production sites in Germany, India, and China. motan-colortronic distribute their products and system solutions via their regional centres. With over 500 employees currently, a yearly turnover of roughly 132 million euros is achieved. Because of their network and long-standing experience, motan can offer their customers what they really need: Individually tailored solutions with real added value.

Contact:

motan-colortronic gmbh

Rüdiger Kissinger

Otto-Hahn-Str. 14

61381 Friedrichsdorf / Deutschland

Tel. +49 6175 792-214

ruediger.kissinger@motan-colortronic.de

www.motan-colortronic.com