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Strategy | energy management


Energy is a signifi cant cost for all injection moulders. Here, plastics processing business management expert Robin Kent provides some valuable advice on how to take control of energy use


Getting to grips with energy


Plastics processing is one of the most energy intensive of the ‘light’ manufacturing industries and most processors now realise that energy is a signifi cant and increasing cost. New machine technologies and processing methods have improved the energy effi cien- cy of injection moulding equipment greatly over the past 10 years. But however modern your production equipment, good management will always result in reduced energy bills. The fi rst step for any injection moulder that wants to


cut energy costs is to know where the money is actually being spent. The best, and most accurate, way to do this is to use ‘energy mapping’ to build a model of the energy use at the site (which is related to the site’s production activity) and then to use sub-metering or other energy use data to validate this energy map. This will provide both a visual and mathematical model of energy use and allows efforts to be targeted where they have the most effect. At the global (site) level, most injection moulding companies will fi nd that their energy use is distributed as shown in Figure 1a. This typical injection moulding site example shows that the injection moulding machines (IMMs) use the most energy. For injection moulding sites with a great deal of downstream activity, such as assembly, the downstream energy use may also be signifi cant but it will rarely be as great as the energy used by the IMMs.


www.injectionworld.com For most moulding sites, ‘invisible’ services such as


chillers, compressed air and pumps, will account for up to 30% of the total energy used. While the IMMs are the largest energy users, the services areas may provide easier savings. It is possible, using sub-metering or portable


monitoring equipment, to look at the energy use of the IMM itself and this can again be sub-divided to show where the most energy is used. At the machine level, most injection moulding companies will fi nd that their energy use is distributed as shown in Figure 1b. At this level, the major energy users are the main motors of the IMM and in most cases this will use over 69% of the total energy (depending on the process, machine


Lighting 5% Water pumps 5%


Heating 2% Offices 1%


Control cabinets 2%


Others (material feed, ejection, etc.) 6%


Compressed air 10%


Chillers 11%


Injection mouldng 66%


Heating


(barrel and other 23%)


Main motors 69%


Figure 1a (left) shows energy distribution across a typical site. Figure 1b (right) shows energy use at the machine level


September 2013 | INJECTION WORLD 29


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