Roth Industries: Less Energy for Better Injection Molding
Efficiency and environmental protection: two sides of the same coin
Achieving fully climate-neutral production is a noble goal, but for companies, it must also make financial sense “at the end of the day.” Roth Industries managed to reconcile these two objectives at its Wolfgruben site in 2017. Oni’s energy-saving technology for injection molding, along with careful planning in advance, played a key role in this achievement.
Roth Industries, a company with 1,250 employees that also includes Roth Plastic Technology, has been pursuing the goal of environmentally friendly production for several years. Achieving completely climate-neutral production was accomplished in 2017 at the Wolfgruben site in Upper Hesse, where injection molding technology is primarily based. “For our family-owned business, this is a milestone in our development,” explains Dr. Anne-Kathrin Roth, representative of the owner family.
However, successful business development relies above all on innovative products and efficient production, each of which provides competitive advantages. Roth Plastic Technology therefore began investing exclusively in highly energy-efficient injection molding machines years ago—and consistently utilizing the waste heat that is still generated. To this end, Roth has been collaborating with Oni Wärmetrafo since the 1990s at several locations. The energy concept for the most recent extensive expansion of the Roth site in Wolfgruben was also developed and implemented in collaboration with Oni.
Reuse energy
As part of the expansion of its injection molding and logistics facilities, Roth has acquired additional injection molding machines and automation systems at its Wolfgruben plant and created additional office space and logistics areas. “Currently, the machines heat the office and warehouse areas down to outside temperatures of -6 degrees Celsius ‘without a drop of oil,’ as Managing Director Herbert Blodig reports, drawing on the plant’s experience during its first winter in the decidedly harsh climate of northern Hesse. And according to his estimate, this alone saves around 15,000 liters of heating oil.” Part of the waste heat is used for “concrete core activation” to keep the loading zones ice-free in winter. Here, the Oni system supplies heat to a solution implemented by Roth using components from its own product range.
Roth currently operates 38 injection molding machines with clamping forces ranging from 200 to 7,500 kilonewtons at this location, some of which are multi-component machines. Further expansion is already in the planning stages. In addition, Roth has two of the world’s largest blow molding systems for tank systems, and, last but not least, possesses extensive expertise in fiber composite technology: for example, according to Roth, the world’s only plastic hot-water pressure tank is produced here.
Loop lines in the production area supply cooling water to the hydraulic systems of the injection molding machines and the mold circuits. Depending on the required cooling capacity and the heating system’s heat demand, the Oni control system ensures the most energy-efficient energy management possible—while prioritizing safe operation and taking into account parameters such as the outside temperature. The heat demand of modern low-temperature heating systems is primarily met using waste heat from the injection molding machines. The system also integrates the compressed air compressors via heat exchangers. Only excess energy is dissipated via free coolers. Only closed systems with speed-controlled pumps are used here. A chiller with three coils is used when energy peaks occur. Free coolers are available for hydraulic cooling.
The heart of the entire energy-saving technology—including controls, heat exchangers, and pumps—is housed in a compact container that can be flexibly positioned. Multiple interfaces within the system allow for easy relocation of the container in the event of operational changes—and, not least, for the rapid replacement of equipment in the event of potential problems. According to Herbert Blodig, however, no such problems have arisen; nevertheless, this flexibility will be utilized, as the next expansion phase of the plant is already in the planning stages. The container can then be relocated temporarily—for example, during the construction period—or permanently. Expanding the entire system with an additional module is also simple and cost-effective. While striving to reduce both specific and overall energy consumption within the company, production reliability remains the top priority. For this reason, full redundancy was ensured for all pumps and filters. Regular, automatic switching between the duplicate system components ensures their constant operational readiness when needed. This also simplifies maintenance.
Tool Temperature Control: Less Energy – Higher Quality
In addition, Roth uses the temperature control technology from Oni’s subsidiary Rhytemper on many of its machines and tools. This system serves up to 36 cooling channels. “Instead of using five to six temperature control units in a production cell—which alone would cost about 1,000 euros in electricity for the pumps per unit per year, plus additional heating costs—we make good use of the waste heat from the tools via the Oni systems,” explains Herbert Blodig. “We don’t let heating and cooling work against each other, but rather with each other.” This means: Instead of ramping up heating and cooling in an energy-intensive manner for every cycle, only cooling is used here. This is particularly effective for complex geometries, especially when processing polypropylene. Both are key areas of focus at Roth. The “return on investment” depends on the specific conditions resulting from the molded products and the type of mold. However, Herbert Blodig expects an ROI of less than three years in any case, and in many cases significantly less.
Furthermore, this type of temperature control has a positive impact on machine efficiency and part quality. The quality of the molded parts improves significantly, as cycle times tend to be shorter due to the much larger water reservoir compared to typical temperature control units and the uniformity of the cooling. Additionally, the quality of the part surfaces is consistently better. As an example, Herbert Blodig points to a 1.7-kilogram thermotank lid, whose cycle time was reduced by 18 percent—with significantly reduced warpage and high surface quality.
From concept to full-scale operation in no time
“The initial ideas for our new building in Wolfgruben emerged in late 2014, but then things moved quickly. Production began as early as mid-2016,” Herbert Blodig briefly summarizes the process. Consequently, the planning and implementation of the energy systems had to proceed in parallel with the other construction phases, as did the commissioning. The application at Roth also presented Oni with several specific challenges: Roth manufactures a wide range of components for modern HVAC systems in residential and commercial buildings across multiple facilities.
Consequently, Roth possesses extensive expertise in heating and cooling technology. The concepts and solutions presented by Oni can therefore be scrutinized and evaluated here very specifically in terms of energy efficiency and sustainability—with apparently favorable results. In addition, Roth’s own products were integrated into Oni’s overall concept in many areas. “Nevertheless,” says Herbert Blodig, “the energy-saving technology was up and running quickly and on schedule. We barely had a ramp-up phase.” The control system had already been programmed in advance; during the first two weeks of live operation, only minor adjustments were necessary. The only follow-up work required was replacing a pump with a smaller model, which saves an additional 400 euros in electricity costs per year.
Be able to and be willing to
This example should make it clear that techniques for sustainably reducing energy consumption are available in many areas of the company—including in energy-intensive operations. It should also be evident that these techniques can generate benefits both in terms of costs and product quality. Long-term, comprehensive strategies are particularly promising. The fact that Roth can consistently pursue sustainability strategies despite the fierce competitive environment is also a priority for the owner family. They are actively and resolutely driving the necessary investments in coordination with experts from production, facilities management, and external specialists. “The fact that the entire company has been producing in a verifiably climate-neutral manner since 2017—thanks in part to the energy-saving Oni systems—is not, however, an end in itself. At the same time, competitiveness has been strengthened through cost reductions,” says Dr. Anne-Kathrin Roth.
