|Left: Wet flood machining. Right: MQL machining. Graphics: Unist Inc. Click to enlarge.|
Ford Motor Company has its near-dry machining process—Minimum Quantity Lubrication (MQL)—to six plants globally, a number that will nearly double in the next few years.
Machining metal pieces generates friction and heat. Conventional wet machining floods the work piece with metal-working fluids, requiring large amounts of fluid to cool and lubricate the cutting tools. MQL eliminates conventional flood coolant from the machining processes, lubricating cutting tools with a fine spray of oil directed exactly when and where it is needed. MQL reduces oil mist generation; biological contamination of coolant; waste water volume; costs for capital equipment; and regulatory permitting. MQL also improves recycling and transport of coolant contaminated chips.
Studies (Faverjon et al. 2013) have shown that the application of MQL leads to a large decrease of the friction coefficient (0.1–0.2) and eliminates almost all traces of adhesions on pins for any substrates.
|Introduction to MQL by Unist, a vendor of metal cutting fluids and application systems. Click to enlarge.|
For a typical production line, MQL can save more than 280,000 gallons (1 million liters) of water per year, Ford says. Cologne Engine Plant in Germany decreased water use per engine by 50% from 2011 to 2012 by switching to the MQL process.
For the 1.0-liter EcoBoost at Cologne, the amount of coolant required to machine aluminium cylinder heads has dropped to just 1 liter for 250 units—compared to up to 500 liters using previous cooling methods—a reduction of up to 99.8%. Where MQL could not be introduced, Ford has streamlined coolant usage for maximum efficiency. 1.0-litre EcoBoost production in Cologne will use a total volume of 235,000 liters of coolant, compared to 1.25 million liters used in similar high volume production processes.
MQL also reduces the amount of oil needed to machine an engine or transmission 80% or more, to approximately 100 milliliters (3.4 fl oz)—about half the size of an average drinking glass. Without the need for a coolant system across most engine production lines, MQL also helps to reduce energy use. While conventional wet machining produces an airborne mist, MQL eliminates that mist, improving air quality in the plant.
Plants that have switched to the MQL process include:
- Changan Ford Engine Plant (China)
- Craiova Engine Plant (Romania)
- Cologne Engine Plant (Germany)
- Livonia Transmission Plant (Michigan)
- Romeo Engine Plant (Michigan)
- Van Dyke Transmission Plant (Michigan)
Ford continues to work toward cutting water use 30 percent per vehicle by 2015. Between 2000 and 2012, Ford reduced global water use by 62%—about 10 billion gallons.
Stoll, A., Silverson, S., and Furness, R. (2007) “Environmentally Friendly and Low Cost Manufacturing – Implementation of MQL Machining (Minimum Quantity Lubrication),” SAE Technical Paper 2007-01-1338 doi:
Stoll, A., Sebastian, A., Klosinski, R., and Furness, R. (2008) “Lean and Environmentally Friendly Manufacturing – Minimum Quantity Lubrication (MQL) is a Key Technology for Driving the Paradigm Shift in Machining Operations,” SAE Technical Paper 2008-01-1128 doi:
Nourredine Boubekri, Vasim Shaikh, Phillip R. Foster (2010) “A technology enabler for green machining: minimum quantity lubrication (MQL)”, Journal of Manufacturing Technology Management, Vol. 21 Iss: 5, pp.556 - 566 doi:
Pierre Faverjon, Joël Rech and René Leroy (2013) “Influence of Minimum Quantity Lubrication on Friction Coefficient and Work-Material Adhesion During Machining of Cast Aluminum With Various Cutting Tool Substrates Made of Polycrystalline Diamond, High Speed Steel, and Carbides” J. Tribol. 135(4), 041602 doi: