AFK: Efficient Injection Molding for Medical Technology – Cleanroom Technology and Energy Efficiency Go Hand in Hand
AFK, an injection molding company based in the Sauerland region, is committed to providing comprehensive solutions, including tool development and optimization. The company is currently expanding its medical technology division, for which a new ISO Class 7 cleanroom has been constructed. This project involved the challenge of operating the cleanroom in a particularly energy-efficient manner, thereby complementing the energy-saving concepts applied to the rest of the injection molding process.
Sensitive production areas, where defined values for air temperature, pressure, and humidity must be maintained in addition to particle concentration, and which are also subject to regular, certified testing, are typically housed in enclosed cleanrooms. The requirements for their planning, construction, operation, and testing are specified, among other things, by VDI Guideline 2083, EU GMP guidelines, and other national or customer-specific guidelines. Due to the high quality and hygiene standards required for parts produced for medical technology, AFK Kunststoffverarbeitung uses a complete ONI cleanroom system.
ONI complete cleanroom system. In this ISO Class 7 cleanroom—which corresponds to the older US Standard 10,000—the manufactured parts are also packaged. During the design phase, the operational reliability of the cleanroom systems was an absolute priority, but low operating costs were equally essential.
To keep the energy consumption of the cleanroom as low as possible, special filter technology was employed and an especially efficient air distribution system was implemented. “As an energy-intensive operation, low energy costs are of particular importance for securing our future. As a partner in this field, ONI also provides services such as support in securing grants,” says Managing Director Andreas Franke, describing the situation.
Drastically reduce refrigeration system operation
To cool the injection molds, a cooling capacity of currently 130 kilowatts must be provided year-round via a supply network, maintaining a constant cooling water temperature of 15 degrees Celsius. In many cases today, electrically powered chillers are still used throughout the entire year to generate the cooling water, which leads to significant costs due to high electricity consumption. In contrast, AFK’s cooling water concept limits the use of chillers to operation during the summer and a small portion of the transitional period.
The cold water for cooling tools and ventilation equipment is generated cost-effectively during the transitional and winter seasons via a so-called winter relief system. At the heart of this winter relief system is a glycol-free, patented air-to-water heat exchanger that uses free outside air to cool the cooling water. If the outside air temperature is below the cooling water return temperature, the relief of the chillers begins.
Specifically, this means: Pre-cooling is performed by the heat exchanger installed outdoors, while the required residual cooling continues to be provided by the chiller. If the outdoor air temperature reaches a value that is only a few degrees below the cooling water supply temperature, the chiller shuts down completely and the heat exchanger takes over the cooling of the cooling water on its own. Practical experience shows that, thanks to winter load reduction, in most cases chillers are not used for over 70 percent of operating time.
Cooling water provides free heat
Heating a facility with several thousand square meters of production, office, and warehouse space during the transitional and winter months typically requires a significant amount of natural gas or heating oil. These costs have a significant impact on production costs. In the energy supply concept developed by ONI, energy used once at the AFK site in Finnentrop is utilized twice. This is made possible by dividing the cooling water system into two closed circuits.
The basis of the new heating energy concept for AFK is the use of waste heat from the oil cooling of the injection molding machines. Many plastics processors still discharge this waste heat unused into the atmosphere via recooling systems.
However, the temperature of 35 degrees Celsius in the cooling circuit return—which is sufficient for the machines’ oil coolers—is ideal for space heating. In this case, special industrial and office heaters supply a large portion of the approximately 5,000 square meters of office and warehouse space with free heating energy.
During production hours, approximately 200 kilowatts of power are continuously available for heating purposes. This type of waste heat utilization offers the operator a financially attractive dual benefit: waste heat, which previously had to be cooled back at great expense, is converted into free heating energy and drastically reduces heating costs—a particularly valuable advantage in times of rising energy costs.
Low-temperature heating technology offers an additional positive effect: office and industrial hall heaters can achieve an optimal temperature distribution within the space. The relatively small temperature difference between the heating outlet and the room air temperature results in particularly good, homogeneous mixing within the space and a comfortable indoor climate.
Even the most powerful system needs to be optimally organized if it is to operate with minimal energy consumption. For this reason, AFK uses a dynamic management system developed by ONI to manage the energy supply. At its core is a PLC module running energy-optimizing system software.
All information regarding the system status of the entire plant converges here, is evaluated, and from here, the system components receive all necessary commands.
For example, the control system detects when the chiller can be taken off load and automatically activates the free cooler. This ensures that winter load relief remains active for as long as possible, because every hour the chiller remains shut down is worth real money to the operator.
The same principle applies to heat recovery: If heating is required in a specific area of the facility, the necessary capacity is drawn from the machine cooling circuit. The resulting reduction in cooling capacity then leads to a decrease in free cooling capacity, which saves additional electricity.
Many commercial refrigeration systems harbor significant energy-saving potential that can be realized cost-effectively from a business perspective. The “Impulse Program for Climate Protection Measures in Commercial Refrigeration Systems,” launched by the Federal Ministry for the Environment, Nature Conservation, and Nuclear Safety, offers an additional incentive for retrofitting old, inefficient refrigeration systems.
Renovation measures that result in a significant improvement in the energy efficiency of refrigeration systems are supported with non-repayable grants. This program also offers the possibility of funding heat recovery measures in conjunction with refrigeration system optimization.
For comprehensive refrigeration system optimization, funding is available for two areas through what is known as “basic” and “bonus” grants. “ONI experts brought these funding opportunities to our attention and actively supported us throughout the application process. That’s what we call a valuable, collaborative partnership,” says Commercial Director Daniel Struwe.
The AFK project exemplifies how comprehensive energy concepts open up the possibility of particularly economical—and thus cost-saving—energy production. “With the energy concept we’ve now implemented, we’ve created a situation where we can produce energy efficiently and economically. This strengthens our competitiveness while also making a significant contribution to securing our future,” concludes Andreas Franke regarding the project implemented at his company.
