A particular characteristic of progressive companies is that they also continuously optimize the environment in which their core business operates. In the production of injection molded parts this also and specifically includes the cooling of parts of the mold and hydraulic components.
The fact that investment in efficient temperature control paves the way not only to higher molding quality but also to lower operating costs is demonstrated by the industrial experience of Oskar Lehmann GmbH & Co. KG.
The company founded in 1967 in Blomberg-Donop, Germany, has for 45 years been one of the suppliers operating globally in the field of parts made from engineering plastics (max. shot weight: 1,100g). The product range includes, for example, caps and slides for furniture production and many other sectors and has now risen to over 5,000 special articles manufactured to customers` specific requirements.
Until recently at Oskar Lehmann the treatment of cooling water for the cooling circuits for molds and the hydraulics was carried out by two air cooled chillers. When the plant was to be modernized the company commissioned to do the work, gwk Gesellschaft Wärme Kältetechnik GmbH based in Kierspe, Germany, was also asked to achieve a reduction in operating costs.
By using a cold-water circulation system (manufacturer: gwk) a considerable burden has been taken away from the existing chillers. As a result of this they can be shut down or be run under partial load over a certain temperature range.
In this way energy consumption for running the chillers is greatly reduced. The potential savings are about 70 kW/h. Given an annual operating time of 6,000 hours this is equivalent to savings of 420,000 kW. Due to this lowering of operating costs the investment in the additional installation was paid back within 14 months.
The reliable and economic operation of production machines also depends on how susceptible to failure the cooling system is. Fresh water is saturated with oxygen and carries suspended particles and minerals along with it. These materials and substances may form deposits and block the cooling channels in the molds or result in increased corrosion.
A cold water circulation system with a heat exchanger made of stainless steel like the one now installed at the Oskar Lehmann plant divides the two cooling circuits and in this way prevents any blockage of the cooling channels. At the same time pumps operating at constant pressure ensure working conditions that protect the rest of the plant.
By ensuring a longer service life for the production machines cold water circulation systems make a major contribution to lowering maintenance costs.
Contaminated cooling circuits have a considerable impact on unit costs. Results of optimization achieved at great cost may be rendered worthless again within a very short period of time if insufficient attention is paid to water quality. Completely regardless of the design differences between individual cooling systems, deposits and corrosion products always have negative effects. Productivity falls and operating and maintenance costs rise.
For this reason Oskar Lehmann had a water treatment system installed (type: gwk active) which by cleaning the cooling medium upholds the optimum performance parameters of the injection molding machines in continuous operation.
The treatment installation desalinates the water and filters it. As a result electrical conductivity falls, thus counteracting galvanic corrosion. In addition the pipes are protected against damage by chemical additives otherwise known as corrosion inhibitors.
The filters in the treatment system trap biological material and extraneous items which could get into the cooling circuit when a mold is changed, for example. This measure also prevents the pipes getting blocked and the plant corroding.