Wehrle: Keeping Energy Costs Under Control with Precision
A comprehensive energy-saving concept for the injection molding shop.
Flow measurement technology is the specialty of Wehrle, a company based in Furtwangen that originated in the watchmaking industry. A core area of this long-established company is plastics technology, which today produces precision components using approximately 70 injection molding machines, primarily employing two-component technology. In addition to continuous innovation in products and production, the company has made extensive investments in technologies designed to sustainably reduce energy consumption—to ensure it can continue manufacturing in Germany at globally competitive costs in the future.
Companies with 170 years of successful history are few and far between in Germany and Europe. Starting with the production of Trompeter watches, which can be admired today in the German Watch Museum, the company has always focused on precision products throughout its history to this day. Today, the two business units “Metering” and “Precision Plastics,” which produce plastic components and assemblies for customers across various industries, form the most important pillars. More than 70 modern injection molding machines, a large portion of which are equipped for 2K technology, are available for this purpose. The clamping force ranges from 250 to 2,200 kilonewtons, and the part weights range from 0.01 to 600 grams.
The company’s positive growth is reflected in a steadily increasing workforce and the recently completed new production facility. Spanning approximately 11,000 square meters across four floors, the facility has found an attractive new home: the energy center in the basement, the plastic injection molding shop on the ground floor, office space on the first floor, and the toolmaking shop—equipped with state-of-the-art technology—and employee break rooms on the second floor. The building’s architecture, interior design, and individual operational areas have been optimized for efficient production processes. “As a medium-sized company with deep-rooted traditions in the Black Forest, we are committed to our location and the people who passionately contribute to achieving our goals. For this reason, we develop and manufacture exclusively in Germany. In everything we do, we always keep energy efficiency in mind to contribute to the preservation of our environment. To implement an energy concept in our new construction project, we therefore sought a partner with extensive experience. After conducting market research and evaluating information from reference projects, we brought on board the energy-saving specialist Oni from Lindlar. Together, we implemented an energy supply concept that sets new standards in terms of both economy and ecology,” says Georg Herth, managing partner of E. Wehrle GmbH, describing his decision.
Incorporate natural resources
If well water can be used as a recooling medium, it provides an unbeatably cost-effective source of cooling energy. A well had already been drilled on the Wehrle site years ago to supply the first injection molding shop. This was integrated into the new supply concept and optimized. The available flow rate is now utilized to the fullest extent possible within the permissible temperature range. Thus, supply circuits with different temperatures are connected in series whenever possible. This series connection is made possible by selecting the supply temperatures in the individual cooling circuits. For supplying the injection molding machines in the hydraulic cooling area, a spread of 25/30 °C was selected; for the mold cooling area, a spread of 15/18 °C; and for ventilation, a spread of 12/18 °C. Since the individual circuits are operated separately from the return cooling network via heat exchanger units, it is also possible to use the waste heat from the machine’s hydraulic cooling for heating purposes.
Security of supply is a priority
Meeting delivery commitments is arguably the most important requirement customers place on their suppliers. This requirement takes on particular importance when parts must be delivered “just-in-time” or “just-in-sequence.” To be prepared for all eventualities, all systems and heat exchanger units at Wehrle in Furtwangen have been designed to ensure dual supply reliability at all times. Furthermore, should the well water supply prove insufficient during the summer months or if additional capacity is needed to meet peak demand, a chiller with a cooling capacity of 310 kilowatts can be switched on immediately.
Cooling saves on heating costs
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. Heating energy consumption and the resulting operating costs are therefore substantial. In addition, a boiler room equipped with a boiler, burner, and exhaust system is required for heat generation and distribution. To keep investment costs and, ultimately, heating costs as low as possible, Wehrle initially focused on utilizing waste heat from all possible sources. The cooling energy supply for the injection molding machines’ hydraulics and the cooling circuit of the air compressors were identified as particularly attractive sources.
For the injection molding machines in the two production areas, cooling water with a temperature range of 25/30 °C and a capacity of 300 kilowatts is provided for the machine hydraulic cooling. Recooling would normally also run via the well water system during the transitional and winter months.
Here, however, energy that has already been used is simply reused by converting the cooling circuit into a heating circuit. This is made possible by the fact that industrial underfloor heating panels were installed in the new building; due to their high heating surface density, these panels can operate with a supply water temperature of 30 °C and bring the rooms to be heated up to the desired temperature. In addition, waste heat at 70 °C is available from the compressed air supply, which is also converted into low-temperature heat via a heat exchanger system and made available for the underfloor heating and ventilation systems. Through this heat recovery, free waste heat is transformed into valuable heating energy that replaces natural gas and heating oil, thereby preventing unnecessary environmental impact.
Sensitive manufacturing areas where high-quality products are produced require a well-defined ventilation system. Unfortunately, experience has repeatedly shown that costly ventilation systems in industrial facilities are energy-intensive yet fail to deliver the desired results. Since the molded parts used by Wehrle in precision measuring instruments must meet the highest standards of product quality, consistent production conditions must be ensured under all circumstances. In the area of indoor air quality and room temperature distribution, Wehrle opted for a ventilation concept tailored by Oni, which was planned and implemented with full consideration of all aspects regarding reliability, energy efficiency, and operational safety.
Various air supply systems were installed, each optimally adapted to the room’s geometry. These include floor-level air diffusers in the production halls and air supply ducts mounted in the ceiling. This ensures that supply air is directed precisely where it is needed. Large discharge surfaces also ensure that the supply air is introduced at low flow velocities. This prevents disruptive air turbulence and localized airflow. To heat the fresh air that must be supplied, machine waste heat or the waste heat from the compressed air compressors is utilized during the transitional and winter seasons. The use of free waste heat for air heating naturally has an extremely positive effect on the energy balance and, ultimately, the company’s annual operating costs.
Trust is good, ....
...It’s better to be in control. While plausible economic feasibility studies and exemplary reference projects can certainly be helpful in the decision-making process, it’s nice to be able to check the projected savings and the operational status of the plant equipment at a glance. In the case of Wehrle, the company’s management wanted precisely this capability so they could evaluate their decision to install an energy-optimized system in retrospect while simultaneously keeping an eye on the system’s status. A control system was therefore installed that visualizes all relevant system data. At the center is a PLC module with energy-optimizing system software developed by Oni, which acts as a dynamic management system to organize the energy supply at Wehrle. 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 immediately detects when a peak load requires the chiller cooling to be activated or in which area waste heat recovery is currently possible. This ensures that only the amount of primary energy consumption that is absolutely necessary is used. If heating is required in a specific area of the facility, the corresponding capacity is provided from the machine or compressed air cooling circuit. The resulting reduction in recooling capacity, in turn, leads to a reduction in well cooling.
Well-positioned
The Wehrle project serves as a prime example of how comprehensive energy concepts can enable highly efficient—and thus cost-effective—energy generation. “We have relied on state-of-the-art systems technology in all areas, from refrigeration to ventilation and pump technology, and are pleased that the energy concept we have now implemented not only allows us to produce with exceptional energy efficiency but also makes a significant contribution to environmental protection by keeping electricity and gas consumption at a minimum. The experts at Oni provided us with exemplary support from the initial project discussion through to the turnkey handover of the system and remain our partner of choice when it comes to reliable and energy-efficient plant systems,” concluded Georg Herth regarding the implemented energy concept in Furtwangen.
