Making the leap to MQL

END USER: Volkswagen AG, +49 5341-230, www.volkswagen.de.
CHALLENGE: Minimize lubricant for a mass-production cylinder head line.
SOLUTION: Switch to minimum quantity lubrication.
SOLUTION PROVIDER: bielomatik inc., (248) 446-9910, www.bielomatik.com.

Volkswagen AG’s site in Salzgitter, Germany, is one of the largest engine plants in the world. Covering 2.8 million sq. meters, the plant manufactures about 7,000 engines in more than 370 variants every day, including ones for Volkswagen, Audi and Bugatti brands.

The plant has become the world’s first mass-production line for cylinder heads that uses minimal quantity lubrication (MQL), or near-dry machining, according to the company. A mixture of compressed air and tiny droplets of oil provide the needed lubrication, replacing the coolant lubricants previously used.

From the start, Michael Knauf, head of tool planning, was involved in incorporating the technology. Since 2008, he has been responsible for testing MQL technology at the Salzgitter plant and merging it into the operation’s most demanding processes.

The beginnings of MQL use at the plant go back to the late 1990s. Later, in the 2000s, the plant moved from machining steel and cast parts via MQL to also machining simple aluminum parts with MQL. Even at that time, the plant was using MQL systems from bielomatik Leuze GmbH + Co. KG, Neuffen, Germany. (The U.S. subsidiary is bielomatik inc., New Hudson, Mich.)

The next milestone was the “innovative” MQL production line at the Salzgitter plant for dry machining of aluminum cylinder heads. The line was installed in 2009 and entered into series operation in 2010.

A key motivating factor for using MQL is that it offers clean production. The swarf is dry, the machine tools only require cleaning once every 2 to 3 weeks, machine operators do not need any special clothing or gloves, and there are no oily, slippery work surfaces.

A second motivating factor is reducing the cost of lubricant use as well as preparation, maintenance and disposal costs.

Using conventional lubricants, VW found approximately 81 to 99 gal. per minute (305 to 375 l/min.) of lubricant is in circulation for a twin-spindle GROB G 320 machining center. Therefore, when 20 machines produce, for example, 2,000 cylinder heads a day, about 2,113 gpm (8,000 l/min.) of lubricant is required from the corresponding fluid circuit.

Previously, lubricant consumption, including evaporation and carryover, of 1.1 to 1.4 gal. (4.2 to 4.3 l) per cylinder head was the norm. Now, no more than 0.002 to 0.003 gal. (7 to 10 ml) of lubricant per cylinder head is required.

Notably, in a machine tool with two spindles, only slightly more than 0.004 gal. (17 ml) of lubricant is used per spindle per hour.

Because the supply of lubricant is only on when the machine is cutting and is switched off when traversing and between operations, VW has reaped additional operational savings. Water consumption has also been significantly reduced. Only one washing process is required where previously two were necessary.