Together with the Energy Management team from Bosch Power Solutions, Homburg, the team from KNOLL Maschinenbau, Bad Saulgau, installed high-pressure pumps with frequency converters in 50 machining centers to improve efficiency and power consumption. The pumps were equipped with frequency converters to supply the machines with cooling lubricant as needed. The energy savings are on average over 50 percent.
KNOLL KTS High Pressure Pump with Frequency Converter
Environmental protection, CO2 balance and energy efficiency are the top issues of our time, and industry is also concerned with them intensively. At KNOLL Maschinenbau, Bad Saulgau, they are given high priority in many ways: in the office building, in production, but also in the products, solutions and services offered. As a leading provider of pumps, filters and complete coolant systems, the company promotes the use of frequency-controlled high-pressure pumps for supplying coolant to machine tools – not only as initial equipment, but also as retrofits. In order to determine the energy savings that can be achieved during ongoing operation, KNOLL developed the so-called E-PASS around fifteen years ago. This measurement service and the associated conversion are now used by numerous metalworking companies.
Global specialists in energy management
One KNOLL customer and partner in matters of E-PASS and energy efficiency in coolant systems is Bosch Power Solutions (PS) at the Homburg site. Since 2008, this branch has had its own department that deals with the topic of energy management. At the time, a project team initially identified various energy saving potentials in its own plant. Energy manager Bernhard Kohl has been involved from the beginning. He explains: “Our Homburg site is a production plant where we manufacture components for diesel and now also hydrogen technology. Our first energy efficiency projects concerned mechanical production with defined and undefined cutting edges, where we identified savings potential in the washing processes, the supply of compressed air, hydraulics and the cooling lubricant. We thought about measures, tested them and transferred them to the entire plant. We were very successful with this and were able to significantly increase efficiency in various areas.” Even today, the energy management team continuously achieves three to five percent energy savings per year within the plant.
Active Worldwide in Energy Efficiency
In 2014, the idea arose to offer the accumulated know-how to other Bosch locations and the external market. “We implemented this idea together with the Bosch division ‘Bosch Energy and Building Solutions’, which acts as integrator and general contractor for all projects,” says Michael Blon, coordinator of Energy Services & Energy Platform at Bosch Power Solutions.
For such orders, the energy management department formed an external team that now operates worldwide and works not only for Bosch plants but also for customers in the automotive industry and other industrial segments. A major project arose in 2021 in the engine plant of a German car manufacturer, where crankshafts and cylinder heads, among other things, are produced.
Michael Blon explains: “In most cases, we start with a comprehensive analysis. Our experts first look at the various areas of the respective plant and identify opportunities for energy savings. This was also the case in this case, where we identified great potential in machining. 49 ExCello machining centers with unregulated high-pressure coolant supply were used there. The conversion to demand-based supply of coolant using frequency-controlled high-pressure pumps opened up great savings potential.”
Bernhard Kohl adds: “We had already carried out such conversion work on machine tools in our own factory – in cooperation with KNOLL Maschinenbau. Due to the positive experience, we also brought these pump specialists on board in the engine factory, especially since the ExCello machines were already equipped with KNOLL pressure booster stations.”
Measuring System for the Efficiency Analysis of high pressure pumps
Thomas Wissel, KNOLL’s field sales representative responsible for the Bosch plant in Homburg, explains: “With the KNOLL E-PASS, we have a special measuring system for the efficiency analysis of high-pressure pumps in our portfolio. This enables us to determine the savings potential during ongoing operation in less than an hour. Depending on the result, we are then happy to undertake the conversion.”
After Michael Blon and his energy management colleagues informed those responsible in the engine plant about the potential savings to be expected with the ExCello machines, they agreed to the E-PASS measurement and the conversion of a pilot machine after an initial cost calculation. Since the 49 machining centers in several production lines perform different tasks, they jointly selected a reference machine whose machining operation promised representative measurement results.
The E-PASS measurement was carried out by Florian Schönbucher, who has been responsible for energy efficiency in service sales at KNOLL since 2017. He explains the background to the savings potential and the measurement: “We used high-pressure pumps on the ExCello machines, which provide different pressure levels via a so-called Vario valve. However, they still continuously generate the full volume flow, so that the coolant that is not needed has to flow away. This is associated with a wide range of energy losses, which a frequency converter helps to avoid. Because it ensures demand-oriented pressure control by adjusting the speed of the pump.”
What can the KNOLL E-PASS measuring system do?
The KNOLL E-PASS is used to determine the power consumption of the high-pressure pump in the process and the power actually used for the machining process. The time required is minimal. The machine in question must be shut down for around five minutes in order to install a measuring turbine after the pressure relief valve. This then determines the actual coolant flow to the machine and the respective pressure during a complete machining cycle. In addition, required data such as operating hours, electricity and investment costs for the retrofit are entered into the calculator.
After the measurement process and the turbine has been removed, the calculation starts. The largest share of the energy savings comes from the difference between the fixed speed and the speed actually required with a frequency converter. The frequency-controlled drive of the pump also means that less heat is introduced into the cooling lubricant and the ambient air. In addition, the pump is protected by partial load operation, which increases its service life. All of these factors are taken into account in the E-PASS evaluation. Just a few minutes after the measurement process, a printout is available that provides exact figures on the possible energy savings with a retrofitted frequency control and the payback period.
Great savings potential
In the engine plant in question, each of the ExCello machines performs an operation with different machining processes (milling, drilling, threading, etc.). Depending on the tool, these require a coolant supply at different pressure levels up to a maximum of 64 bar. The KNOLL E-PASS measurement on the pilot machine showed a potential saving of around 50 percent of energy, which was confirmed after its conversion. This led to the follow-up contract, which includes converting the remaining 48 machining centers.
During this rollout phase, Andreas Martin, a member of the external Bosch energy team, took over project management. He explains: “In coordination with our customer, we subsequently took two machines out of operation and converted them together with KNOLL employees. Each team had its own work packages, which were carried out one after the other on the systems in a rolling manner. We needed around five hours per machine.”
Since all ExCello machines are supplied with coolant via a central system, the work only concerned the frequency control of the high-pressure pump, a KNOLL KTS screw spindle pump. This self-priming positive displacement pump is characterized by low pulsation, high efficiency and a long service life. The associated frequency control is called PQ-Tronic at KNOLL, as it ensures variable pressure (P) and flow (Q) with optimal speed setting.
With flexibility and great motivation to success
Machine after machine was equipped with KNOLL products. Andreas Martin praises the collaboration with KNOLL: “The on-site employees were motivated and very flexible, so that we always found a good solution even in difficult situations. And we received coherent documentation from KNOLL in accordance with CE standards, such as drawings, electrical plans, parts lists and safety assessments. This is of great importance to our customer.”
The engine factory is also very satisfied with the service and the efficiency achieved. “Our before and after measurement determined the actual energy savings across the process steps,” says Andreas Martin. Depending on the machine and machining process, this was between 34 and 69 percent. “The differences depend on the machining and the tools used,” explains Bernhard Kohl. “Deep hole or blind hole drilling requires high pressure to remove the chips and maintain lubrication, so the savings potential is rather low. This is different with small tools or threaded holes. Here, lower speeds and only a little coolant pressure are required, so a lot of energy can be saved.”
On average, the engine plant now saves 54 percent of its energy consumption across all 49 machines, which corresponds to around 100,000 euros per year. The systems also run very stably, so that there have been no complaints in the past two years. “The entire conversion will have paid for itself in just over three years,” suspects coordinator Michael Blon. “That is certainly not particularly fast, but given rising energy costs, this time can be shortened.” In any case, these are ensuring an increase in orders in the Bosch energy management department, supported by the self-commitment of many companies with regard to their CO2 footprint . “If we need to equip machine tools with high-pressure supplies tailored to their needs again, we will be happy to turn to our proven partner KNOLL,” confirms Michael Blon.
Bosch in Homburg
The Bosch Group employs around 133,800 people at 100 locations in Germany; annual sales are 19.1 billion euros. Worldwide, there are around 429,000 employees and 91.6 billion euros (as of December 31, 2023). The three plants located in Homburg, Saarland – Robert Bosch GmbH, Bosch Rexroth AG, and Moehwald GmbH – employ a total of 4,400 people, 3,600 of them in Robert Bosch GmbH with its Power Solutions division. As a lead plant and competence center, it manufactures the latest diesel technology for passenger and commercial vehicles. In addition, expertise in the field of hydrogen technology is being built up. This plant also includes the Energy Management department, which, with an internal and external team, advises Bosch locations and industrial customers on energy-saving measures and supports the conversion.