Some of those companies, hoping to cut costs, promote environmentally friendly work environments and enhance employee health and safety, are looking beyond traditional wet machining and have embraced methods known as minimum quantity lubrication (MQL) – dry and near-dry machining that use no or little lubricant to accomplish the same tasks.

But dry or near-dry machining can have its own set of challenges, chief among them the handling of dry chips, concerns about tool life and the need to control thermal influences without large volumes of liquid coolant. How companies that use MQL address these issues could dictate its wider acceptance by more end-users in a broader range of industries.

Fords Approach

Weve had a hundred years of wet machining, said Richard Furness, a manager at Ford Motor Co.s Advanced Manufacturing Technology Development Center in Livonia, Mich. We have to change a lot of minds.

After years of extensive R&D, Ford first explored MQL technology with a pilot program in Germany in the late 1990s. Those early attempts began on manual transmission cases at the companys Cologne, Germany, plant, Furness told LubesnGreases. Initially, it was associated with cost, he said. Enhancing health, safety and quality, while getting rid of coolants, were all issues we wanted to address.

Coolant costs are not trivial. According to Furness, research at several powertrain plants within Ford identified annual coolant usage in excess of five million gallons, at a cost of several million dollars. A study among several global automotive companies further revealed that, within their powertrain operations, coolant costs take a significant bite – in the range of 10 to 17 percent – of the total mechanical manufacturing costs.

The success of Fords European research project prompted the auto giant to incorporate MQL for machining of complex components made at its high-volume powertrain facilities in the Detroit area.

Alexander Stoll, Fords technical expert on powertrain manufacturing who developed and implemented MQL there over the past 10 years, explained that the variety of powertrain components include both engine and transmission parts. So far, the applications using MQL for engine components – such as engine blocks, cylinder heads and crankshafts – are limited. Processes using MQL for engine parts include deep hole drilling of steel and cast-iron crankshafts and supercubing operations at the foundry.

More successful has been the implementation of MQL in aluminum transmission production, which now has reached 80 to 100 percent in several production lines turning out transmission cases, converter housings and valve bodies, Stoll said.

Sips and Chips

Furness explained that the MQL system at the plants uses a Bielomatik two-channel supply system. Air and oil move separately through the machine tool spindle and are mixed in the tool holder, as close as possible to the cutting zone. Vegetable-oil or ester based lubricant – in the smallest quantities (10 to 50 ml/hr) – is then delivered to the work zone.

With MQL there is always fresh oil available for the cutting tool and no treatment and maintenance of the MQL oil is necessary, Stoll points out. Consequently MQL provides stability to the machining process since there are no changing conditions the cutting tools have to deal with – with MQL the quality of the lube always stays constant. The high-viscosity oil that is being used also supports the cutting edge during the metal removal process, and it is an enabler for better surface finish and higher feeds and speeds and longer tool life.

Another issue that Ford has addressed with MQL is how to deal with dry chips when theres no fluid to flush them away.

Without coolant to wash off chips, a special focus on machine and fixture design is mandatory to assist in evacuating chips from the work envelope, says a technical report on MQL Machining Implementation authored by Furness, Stoll and their Ford colleague, Scott Silverson. Machine and fixture details including use of steep angles, fixture covers and wipers were designed to eliminate collection points and help dry chips move downward out of the work envelope.

Overall, Furness asserted, if there is a special awareness on the part of the project engineers and at the supply base, especially by paying close attention and adhering to all the details, then there are no detriments in MQL.

The Bare Minimum

For Hyd-Mech, a Canadian manufacturer of metal cutting bandsaws, MQL has always been about maintaining a clean working environment and waste disposal.

According to national sales manager Rick Arcaro in Woodstock, Ont., the firm has been practicing dry machining for over 15 years and uses it mainly in cutting aluminum, structural steel and solid steel. It purchases MQL units with both a dispensing system and nozzle-mounting system that attaches directly to their machines.

The product offers a very clean shop environment, he said. The end-user can now purchase any material handling equipment without needing coolant drip pans underneath.

But there was a trade-off.

When cutting very hard material or using machines with large blades, we find that the tool life is not as good compared to a flood coolant system, Arcaro said.

In Hyd-Mechs MQL system, a coating of lubricant is applied on the cutting edge of the bandsaw blade. Within the context of MQL, Arcaro explained that in those instances there needs to be more lubricant applied to achieve any type of blade life and any type of heat transfer – but its still far less than typical flood coolant volumes.

At Vought Aircraft Industries Inc., senior tooling engineer Thurman Molder said, To some degree, we have always used minimum quantity lubrication. MQL systems extend our cutting tool life and allow Vought to be more aggressive with spindle speeds and feed-rates on aluminum, titanium and steel components. It [also] helps cut down costs because there is no recovery system. It is just applied and wiped off.

Headquartered in Dallas, the aerospace company designs and manufactures aircraft components including fuselage panels, wings, doors and tails for commercial and military aircraft. Molder said that MQL is primarily used with powerfeed, portable drilling machines.

Our mechanics work on three-story levels so there would be big issues if we used flood coolant, he said. Voughts MQL systems uses both spray-mist and point-of-use automatic lubrication systems at its facilities.

Maintenance issues are one concern, Molder cautioned. In our application, debris can restrict or close the flow of MQL to the tool point. Most of the system consists of small-diameter tubing or fittings, and even the smallest amount of debris can cause flow rate problems.

To combat this, Molder says that more time and attention has to be paid to maintenance and repair issues so that the system runs efficiently.

Learning Curve

Its not a complete, mature technology, said Jeff Coffey, a senior product engineer at Unist. [MQL] does not work with every application. Its better with some metals than others, but theres no one formula that applies to all.

Based in Grand Rapids, Mich., Unist develops microfluidization systems that help operators to reduce the amount of lubrication in their cutting, forming and stamping operations using vegetable based oil. It boasts several thousand customers, including Hyd-Mech, across many industries.

Coffey says that customers purchase his companys equipment for many reasons, including fluid cost savings, environmental cleanup, employee safety, controlling air particulate, better air quality, elimination of dermatitis issues, improved tool life and more aggressive cutting which leads to improved cycle times and higher productivity.

MQL is best suited for milling, drilling and sawing, he said. It is also used in turning and grinding, but there is more of a learning curve in these areas. MQL is in the beginning of the technology curve. While it works great in a lot of instances, we are working with several universities to develop predictive tools to make MQL a universal fit for any cutting operation.

Switching to MQL requires deep study, as well. The entire scope of the machining system and its environment must be analyzed, Furness at Ford emphasized. Every step and component – the oil mist supply, cutting tool design, spindle design, machining parameters, heat generation, temperature compensation, machine and fixture design, chip removal and other factors – has to be rethought.

In addition, Kevin Howes, North American sales manager at Bielomatik Inc. in New Hudson, Mich., says that what is required is the willingness of the end-users and machine builders to get out of the old this is how we have always done it mindset of using coolant.

The German manufacturer of lubrication systems tailors its MQL systems to accommodate a companys machine design. Using synthetic-based, ester-based, or vegetable-based oil, Bielomatiks MQL systems are used in cubing, supercubing, rough and finish machining, drilling, milling, boring, reaming and tapping processes. One of its MQL clients is Ford.

No Panacea

Gary Rodak, president of Gregory, Mich.-based Machining Efficiencies, says that 95 percent of his client base uses flood coolant and that he is not seeing MQL in super high volumes where there is high production.

He said its his job to go in and do a deep dive and evaluate a companys machining systems for complete efficiency. We test the machine so that it delivers what it was purchased to deliver, Rodak said. I see MQL here and there, occasionally, not overwhelmingly. It is not the panacea that it was going to be. [Without] a central coolant system, there needs to be a stronger air system that uses air pressure and vacuums to remove dry chips.

However, Rodak remains optimistic saying that with better nozzles – and better nozzle aim, which is critical – plus optimal tool geometry, there is certainly a future for MQL.

Bielomatiks Howes concurs, saying MQL will become a key technology for automotive, aerospace and defense industries in their effort to find a way to reduce the cost of manufacturing [and] become more competitive in this challenging economy.

MQL is our long-term objective, but were just starting. The data is still unrefined but we know that there are cost savings and quality benefits. Its going to take some time to get some converts, said Furness at Ford.

But once under way, feels Stoll, things should pick up quickly. For industry in general, he predicted, [MQL application] will be somewhere in the range of 15 to 20 percent in the next five to 20 years.