ZKW is investing to save money
Strategically Planned
Energy Savings Shedding light on the darkness—that is the core competence of the Austrian company ZKW. The specialist in complex lighting systems for the automotive industry is planning further qualitative and quantitative growth—using state-of-the-art injection molding technology and a consistent strategy for reducing energy costs.
A product range that appears narrow at first glance but is exceptionally deep is the—obviously successful—concept behind ZKW. The consistent focus on the development and production of innovative and complex lighting systems for the passenger car, truck, and motorcycle markets has led to high market penetration, particularly in the premium segment. ZKW is also clearly benefiting from the trend toward the customization of lighting systems in vehicle manufacturing and their increasing use as design elements. In addition, plastics are increasingly replacing metal components. Since ZKW operates vapor deposition technology in-house, the company possesses the expertise required for surface finishing of both material groups.
Market developments, combined with extensive manufacturing expertise, state-of-the-art production facilities, and innovative product ideas, have contributed to the company’s well above-average growth over the past ten years. Although ZKW also experienced a significant downturn in 2008 and 2009, this did not derail the strategy. ZKW used this respite to implement various measures aimed at further increasing efficiency, such as developing and implementing a completely new energy concept in collaboration with energy-saving specialist Oni and further optimizing injection molding technology with machine supplier Engel.
At its headquarters in Wieselburg, located between Linz and Vienna, the company operates approximately 110 injection molding machines with clamping forces ranging from 2,500 to 11,000 kN, most of them in the 6,500 to 9,000 kN range. A special feature is the wide-plate systems with a clamping force of 11,000 kN, which are equipped with the platen size and peripherals of a 17,000 kN machine. The vast majority of the machines are from Engel—more than 70 in Wieselburg and more than 30 at the ZKW site in Slovakia.
Modern injection molding technology drives production
The energy-intensive field of injection molding has been and remains the ideal starting point for a new, evolving strategy to reduce energy consumption across the entire company: On the one hand, the machinery boasts a favorable energy balance thanks to modern drive and control technology. On the other hand, energy-saving potential in the generation of cooling energy for production has been identified and successfully realized in several areas. The necessary cooling is handled in a particularly energy-efficient manner, and the heat generated in the hydraulic and cooling circuits is optimally reused. ZKW has had experience with various Oni technologies since 2000. This is the only way the company has managed, for example, to keep gas consumption for heating the production halls and administrative units constant over ten years despite enormous growth. The recent expansion and new construction of the administrative building ultimately provided the impetus to take energy savings to the next level.
Make effective use of all available energy
Until now, only the energy from the hydraulic circuits was used to supply the low-temperature shop heating systems via heat exchangers. Today, the waste heat generated by chillers when producing cooling water for tool cooling is no longer expensively disposed of, but is put to good use. The flow temperatures are 16 °C for tool cooling (with a 20 °C return) and 35 °C for the hydraulics with a 42 °C return. The high temperatures for hydraulic cooling can be maintained because all Engel machines used by ZKW are equipped with so-called tropical coolers as standard. Under normal ambient conditions, the glycol-free, idle air-cooled heat exchangers are sufficient to reliably supply the machines with cooling water. Energy-intensive compressor-based cooling systems are not required, even at high outside temperatures. Pressure-boosting systems on the machines are also unnecessary.
In addition to the hydraulic and mold cooling systems of the injection molding machines, other heat sources within the company are “harvested”: Compressors with oil coolers are used for compressed air generation, and their excess energy is utilized. The same applies to the water-cooled chillers of the air conditioning systems.
- Approximately 3,020 kW of cooling capacity in the 35–42 °C range is provided by free-cooling units that are very cost-effective to operate. Currently, 1,260 kW of this capacity is required in the injection molding area for hydraulic cooling, and 1,120 kW for cooling the chillers. The remainder is needed for recooling the HVAC and refrigeration systems. An additional 1,000 kW of reserve capacity can be activated using well water.
- For mold cooling and several other loads in the 16/20 °C circuit, 1,010 kW of cooling capacity is available via air- and water-cooled chillers with winter load relief provided by free coolers.
These performance figures provide ample scope for effective heat recovery systems: A total of 2,380 kW of power is supplied in the form of recirculating air heating systems for offices, industrial halls, and the paint shop. This corresponds to an energy gain of approximately 5,200 MWh, or—at a calculated rate of 50 euros per megawatt-hour—about 260,000 euros per year. Added to this is the recovery from the heating water circuit, amounting to about 650 MWh or 33,000 euros annually.In addition to the cost savings from heat recovery, there are significant energy savings from the use of free coolers to reduce the load in winter. Within a wide temperature range, the use of chillers can be avoided.
Cost-effective air conditioning for one hectare of office space
The three office buildings, with a combined floor area of approximately 10,000 m², meet the latest building standards and are cooled using groundwater (ground-source cooling). In winter, the HVAC system requires a heating capacity of 400 kW to preheat the air. This demand is primarily met by waste heat from production and only supplemented by a groundwater heat pump in emergencies. Additionally, a gas-fired emergency heating system is available, which is also intended for use during non-production periods; however, it has not yet been required. Since the heating demand, due to the company’s dynamic growth, exceeds the amount of waste heat from the machines, the water-cooled heat pump is used to meet the demand. In this specific case, the waste heat is used for heating purposes, and the generated cooling energy is made available to the tool cooling circuit. Operated in this way, the investment in the heat pump pays for itself with a payback period of about 18 months. A particularly clever side effect: The pump can also be used in conjunction with the free coolers as a pure “chiller”—which provides a cost-effective redundancy measure for tool cooling when there is no heating demand in the offices.
One secret to success—in addition to the integrated overall concept—is the system’s control. Defining the correct switching points between the various options and ensuring a steady supply of fresh air requires considerable experience. A sophisticated visualization of the entire system enables continuous monitoring from a central workstation. In the event of error messages, it is possible to quickly determine where action is needed. It is striking that during a visit to the ZKW facilities in mid-December 2011, the typical plastic odor was barely noticeable. Apparently, the ventilation system works very well despite the energy-saving efforts.
ZKW is currently investing in machine technology once again. A “twin system” was installed in late 2011 and early 2012—consisting of two Engel Duo 7050/1100 WPX large-scale machines, each equipped with a Viper 60 linear robot and a Famox 25/2 tool changer with multi-coupling, both also from Engel. The WPX designation in the machine name stands for Wideplate version: While the machines’ technical specifications correspond to those of a standard 11,000 kN machine, their build-in space is roughly equivalent to that of a 17,000 kN version.
For the first time in this installation, a mold changer serves two large Engel machines. The acronym Famox stands for the program: Fast Mold Exchange. With this technology, ZKW aims to reduce setup times for molds weighing up to 23 tons from an average of 2.5 hours to about 6 minutes. This should greatly benefit the development of ZKW’s successful core segment: Here, the focus is on small to medium-sized series of lighting systems in the higher-priced vehicle segment, which are becoming increasingly customized and consequently require frequent retooling. Typically, ZKW retools machines of this size about three times a week. The potential savings are easy to calculate. In addition, the changeover device makes retooling significantly safer, as certain problems and risks—such as damage to the molds—cannot arise in the first place.
Just like the robots, the indexing table is integrated into the injection molding machine’s operating philosophy. The CC 200 control system’s operating logic, visualization, and ergonomics are utilized here. All mold and machine parameters are transferred between the machine and the mold changer without external interfaces. The graphical display of the mold changer can be accessed both on the changer itself and on the machine. In addition, two further aspects are designed to contribute to the high setup speeds: the integrated mold preheating station and the standardized multi-coupling for the media lines, the latter of which was implemented here for the first time. Instead of using chain drives, as is common in other systems, the Famox system operates with patented direct roller drives. Here, each roller has its own electric motor, which is designed to ensure exceptional robustness. The automatic tool changer is designed for tools weighing up to 25 tons; according to the manufacturer, a smaller and a larger version are in the works.
In addition, the machines are equipped with ONI-Rhytemper temperature control systems, which reduce cycle times while ensuring the quality of the visually demanding headlight components. New tools are specifically designed for use with this temperature control technology. With this system, ZKW will be able to significantly improve efficiency in the single-step injection molding of large-volume, visually and technically demanding parts.
Forecasts confirmed
ZKW’s investment strategy can be summed up as saving energy without compromising on performance: In recent years, the company has commissioned only injection molding machines and peripheral systems that are highly energy-efficient while also ensuring the precision and consistency required for its technologically sophisticated core product—lighting technology. With the latest “twin system” consisting of two large Engel machines with a central mold change system, the next leap in efficiency and flexibility is currently being realized through a significant reduction in changeover times. Despite modern machinery, injection molding inevitably produces large amounts of waste heat—which can be put to good use. With payback periods that are sometimes astonishingly short, heat recovery systems sustainably reduce production costs. However, in most cases, simply using heat exchangers is not enough; coherent concepts and control mechanisms are necessary to elevate the entire system to an attractive level of efficiency. This also includes details such as the clever use of the “tropical cooling” feature of the Engel machines in the Alpine region.
After approximately 1.5 years of actual operation, the results to date confirm the forecast values from ONI’s planning. Accordingly, comparable technologies have also been implemented at the ZKW site in China. Here, a longer but still very attractive payback period of about 3.5 years is expected.
