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A one stop shop for granulate supply systems  #9 (67) 2008

Werner Koch Maschinentechnik GmbH, has installed a new full granulate supply system at the modern new factory of Accuma Deutschland GmbH in Zittau

Requirements of the new system
What was the new system intended to do? First of all, the company drew up a list which included the following major requirements: The new central supply system was to be able to supply initially 12, then following expansion 26, injection moulding machines each with 80 kg/h, and be designed to
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Accuma Deutschland GmbH is a subsidiary of the international group Accuma spa in Ghisalba near Bergamo, Italy, a specialist manufacturer of plastic components for electrical accumulators for the automotive sector. In the factory in Zittau, around 5 million housings for motor and vehicle starter batteries are made annually. Customers include well-known companies such as Varta, Johnson Control, Hawker and Exide. Approximately 3,000 tonnes of plastic granulate are processed annually to produce the high-quality battery housings. They range in weight from 0.5 to 2 kilograms
allow later expansion to 40 machines. The company required direct dyeing devices on each machine and an oil-free vacuum pump that would switch automatically to a reserve pump. Accuma also needed a central mixing station to mix 80% new material and 20% ground material with a throughput of approximately 800 kg/h. Six exterior silos were to be installed initially, of which one was for regranulate. Accuma specified that this silo should be filled via a pressurised conveyor system from an existing compounder. Koch Technik presented a customised concept which ensured that every day up to 12 tonnes of PP would be ready in the right place, at the right time and in the right condition. Although equipment made by Italian manufacturers had been in use at the Ghisalba headquarters for some time, Giuseppe Persico, Process Engineer for Plastics at Accuma spa, wanted to find a supplier of complete systems using modern and reliable technology for the factory in Zittau. “We were impressed by the Koch Technik technology, which is why we awarded them the contract,” said Persico.

Ingenious solutions
For the first phase, Koch constructed a central conveyor system with a machine-based stainless steel pipe system linking six exterior silos each with a capacity of 90 m3 to a material distribution system with twelve injection moulding machines. The pipework carrying the material between the silos and the distributor were laid in an accessible channel under the entrance to the factory to save space. The pipework required for the planned expansion of the production facility was already fitted at this point to allow installation of additional equipment to go ahead quickly and flexibly at a later date.

One of the external silos is intended to be used for regranulate. An additional pipe was laid to conduct the mixture of new and regranulated material to the distributor. This allows the material hoses to be rearranged manually on the material distributor as required to switch between new material and the new-regranulate mixture - a quick and flexible solution. A central mixing station with a 1500 litre material reservoir and a two component conveying unit type Tm5570 D supplies the system with another new material-granulate mixture. The two components are mixed with the two component switching device on the conveyor unit only. A pressurised conveyor station with its own control system and a conveying capacity of around 800kg/h was installed to fill the regranulate silo. A 1250 litre container acts as a buffer between the granulator and the pressurised conveyor system. It has its own filling system with a type 4050D conveyor unit.

Direct dyeing system
The granulate is dyed in Koch KEM devices, which are installed in the injection moulding machines. This is very accurate equipment which ensures that the colour of the end product always remains consistent - this is particularly important for Accuma, as its customers have very high standards and require perfect quality. The KEM dyeing process is carried out within automatic volumetric chamber all the time granulate is supplied to the screw - the main component is added via a free feed device. The advantage of this is that when the product is changed, there is no mixed material in the machine needing to be removed. Changes to the dosing values can be seen immediately during production.

The vacuum system
In the factory in Zittau, the vacuum required to convey the granulate is supplied by an oil-free 11kW vacuum pump and an additional reserve pump. Up to 960kg of plastic granulate per hour can be conveyed over a distance of up to 90m. The vacuum pumps, with appropriate line cross-sections and bends, provide careful conveying of the material, avoiding any build-up of streamers.  The central conveying system at Accuma has two pumps each alternating between working and reserve. To save space the pumps are installed lying one on top of the other on a steel framework in a separate side room. The frame was designed to allow the installation of a third pump for the expansion planned for a later date. The vacuum system has an automatic switching function which means that the reserve pump starts up for the weekly change or if the working pump fails or needs servicing. There is a fully automatic self-cleaning Sa3 safety filter installed upstream of the pumps. It removes particles larger than 2µm from the conveying air, ensuring that the system meets stringent cleanliness requirements.

 Expansions implemented smoothly
“We have expanded our system constantly since it went into operation,” says Markus Kuhnel, Head of Production at Accuma in Zittau. Just a few months after the system went into operation it was extended by two external silos, five injection moulding machines and a switching station, which were all integrated in the central conveying system. Production was further expanded a short time later by six injection moulding machines. These required a separate 800 kg/h conveyor circuit and a third vacuum pump with a control system and an Sa3 safety filter.
“Koch Technik reacted quickly and without fuss to our requests for changes at short notice and found appropriate solutions for us on the spur of the moment.” reported Kuhnel.  In order to ensure that production remained free of disruption during the expansion phase, Koch Technik integrated the individual components one after the other.
However, Koch Technik has made an impression beyond the German subsidiary. “We have installed several Koch central conveying units for the material supply system at our headquarters in Italy,” says Persico and is certain that he will be able to rely on the flexible modular system from Koch during future expansions.

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