Vacuum Pump More Precision in CNC Milling

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Dr.-Ing. K. Busch GmbH

Wuxi InfiMotion Technology Co., Ltd.

The company Lorenz Hoffmann has switched the vacuum supply of its CNC machines to a dry screw vacuum pump. This not only saves 3,500 kWh of energy per year but also increases the precision of the machining process.

The milling machine engages, coolant sprays, and metal chips fly. The milling tool moves with millimeter precision over a metal piece secured by vacuum in the production hall of Lorenz Hoffmann GmbH. The company, located south of Würzburg in Kreßberg, utilizes high-precision CNC milling machines in its shop to manufacture prototypes for mechanical engineering, among other things. With its 40 employees, the company has been producing prototypes, small series, and ready-to-install components for various industries for over forty years.

To meet the highest demands for precision, the workpieces must not shift by even one hundredth of a millimeter during the milling process. Therefore, they are secured using vacuum technology. Employees use special vacuum clamping plates connected to vacuum pumps for this purpose.

Less Energy, Higher Quality

To supply its four CNC milling machines with vacuum, the company previously used a separate vacuum pump on each machine. Managing Director Andreas Hoffmann wanted to optimize the vacuum supply in his company and therefore turned to Busch. On the advice of the vacuum experts, he replaced the four oil-lubricated rotary vane vacuum pumps with a single Cobra Plus dry screw vacuum pump. This is connected to the four milling machines via pipes.

"By acquiring the Cobra, we save 3,500 kWh per year compared to the four oil-lubricated rotary vane pumps we previously used—and with even better holding performance," summarizes Hoffmann. This is because the screw vacuum pump is speed-controlled, allowing it to adjust its power to the actual demand, thereby consuming less energy than an uncontrolled pump, whose motor always operates at full speed.

"The Cobra regulates itself and always delivers exactly the performance we need. For example, if only one milling machine is used, the Cobra works at a lower speed than if several milling machines are used at the same time," explains the Managing Director.

This pump model is also fully networked and has a control and monitoring function. The power consumption, vacuum level and motor speed, for example, can be displayed on a color touchscreen. This allows employees to keep an eye on the vacuum supply at all times.

Better Working Conditions, Hardly Any Maintenance

All Cobra screw vacuum pumps from Busch operate completely contact-free, which means they do not require any oil in the compression chamber. "Since switching to the Cobra, we no longer have to change any oil, air/oil separators or filters. This saves around four working days of maintenance per year. So far, the COBRA has run without any faults and maintenance has not been necessary at all," Hoffmann praises.

In addition, the operation of the pump causes considerably less noise than the four old vacuum pumps. Since the replacement, the production hall has been significantly quieter than before. For the employees, this means a significant improvement in working conditions. "Previously, up to four pumps were running at 72 decibels each. The Cobra generates 63 decibels. That's why it's now only half as loud and it's much more pleasant to work," says the Managing Director.

Heating with Waste Heat Instead of Oil

Andreas Hoffmann emphasizes the importance of producing as sustainably and energy-efficiently as possible. By switching to the screw vacuum pump, he now has the opportunity to utilize the pump's waste heat for heating. To this end, he and his team developed a heat recovery system. "The COBRA has water cooling. The heated coolant water is routed through an air heater, allowing us to heat our production hall," he explains. This air heater includes a fan and a heating register that cools the water so it can be reused to cool the pump. As a result, the company, which previously relied on oil heating, now requires significantly less heating oil. "In summer, we direct the waste heat outside. In winter, it's retained in production. This makes it noticeably cooler in the production hall even during the warm season. Previously, the production hall always got very hot in summer," he adds.

Reimbursement Thanks to BAFA Funding

As energy-efficient technologies are subsidized in Germany, the experts at Busch assisted the company in applying for a BAFA grant. As a result, Lorenz Hoffmann received a 40 percent reimbursement of the acquisition costs for the new vacuum pump from the Federal Office for Economic Affairs and Export Control (BAFA).

However, Andreas Hoffmann is particularly pleased with the energy benefits and is proud of his heat recovery system, which was made possible by the new pump: "The purchase of the Cobra has proven to be twice as beneficial for us. We have lower power consumption than before and can use the waste heat from the pump for heating in winter."

Heating with waste heat instead of oil

It is important to Andreas Hoffmann to produce as sustainably and energy-efficiently as possible. By switching to the screw vacuum pump, he now has the opportunity to use the waste heat from the pump for heating. To this end, he and his team developed a heat recovery system. "The COBRA has a water cooling system. The heated cooling water is fed through an air heater. This is how we heat our production hall," he explains. This air heater contains a fan and a heating coil that cools the water down so that it can be reused to cool the pump. As a result, the company, which otherwise uses oil heating, requires significantly less heating oil. "In summer, we channel the waste heat outside. In winter, it stays in production. As a result, it is now noticeably cooler in the production hall, even in the warmer months. Previously, the production hall always heated up a lot in summer," he adds.

Kugelgewindetriebe

Präzision der Werkzeugmaschinen erhöht

Reimbursement thanks to BAFA subsidy

As energy-efficient technologies are subsidized in Germany, the experts from Busch supported the company in submitting a Bafa application. As a result, Lorenz Hoffmann was reimbursed 40 percent of the purchase costs for the new vacuum pump by the Federal Office of Economics and Export Control (BAFA).

However, Andreas Hoffmann is particularly pleased about the energy benefits and is proud of his heat recovery system, which was made possible by the new pump: "The purchase of the Cobra has been doubly worthwhile for us. We have lower electricity consumption than before and can use the waste heat from the pump for heating in winter."