Coolant systems rarely get top billing as the key feature of a machine tool, but that is the case with the lathes and machining centers being introduced to this country by Hakusui USA Inc. (Schaumburg, Illinois). The line of machine tools includes four lathe models and two vertical machining centers. All of the machines have, as a standard feature, a high pressure mist coolant delivery system that creates a mist of ultra-fine water and oil particles. The company claims that this allows for significant increases in surface speed and metal removal rates and longer tool life.
This method of coolant delivery, which the company has dubbed the ECOREG System, mixes a water-based coolant with an oil lubricant in a high pressure air stream, creating extremely small particles. These particles are then injected through high-pressure nozzles designed to be precisely directed to the point of machining.
The coolant is a solution of an anti-corrosive agent and surfactants diluted in water. The ratio of water and solution varies from 20:1 to 30:1. The oil lubricant that the company recommends is a specially formulated vegetable oil but other oils can be used, with those formulated as extreme pressure lubricants being recommended. The advantage of the vegetable oil is that it creates virtually no environmental impact.
One of the main benefits of the system is that is uses very little liquid. The company says that, under typical machining conditions, its lathes consume about one liter of coolant in 55 hours of machining. The VMCs consume approximately the same amount under normal machining conditions. Despite this low usage, the system provides a substantial cooling and lubricating effect.
This effect is apparently due to the almost immediate evaporation of the mist on contact with the workpiece, cutting tool and chip. The misting of the liquid increases its surface area, enhancing its capacity to absorb heat. Pinpoint aim of the nozzle is critical however, because the high pressure delivery of the mist blows away chips, which carry off much of the heat generated in machining. High feed rates and spindle speeds, of course, help considerably to keep heat in the chips as they are formed. Because almost all of the mist evaporates so quickly, the chips are dry, aiding their disposal and increasing their value as a recyclable material.
The fine particles in the mist also allow it to penetrate the cutting tool/workpiece interface when injected at high pressure. Apparently, the ECOREG System creates particles that are small enough to enter the gap between tool and workpiece while high pressure overcomes the centrifugal force of the rotating tool or workpiece. Thus, a very small amount of the oil lubricant—0.3 to 0.5 cubic centimeters per minute—can be very effective, the company says.
In addition to the environmental benefits of this system, the company also cites improved machining results. The combination of increased speeds and feeds with the effects of high cooling and excellent lubrication results in better dimensional accuracy of the workpiece, finer surface finish, higher productivity and increased tool life. The company has not published direct comparisons for various applications but is inviting users to submit sample workpieces for testing at the company's technical center in Schaumburg. The company will then report on process improvements to be expected using its machine tools at the recommended settings. An increase in tool life as high as 400 percent is cited in the company's literature as a typical benefit.
Otherwise, the lathes and VMCs to which Hakusui is attaching its ECOREG System are of conventional design. The lathe line includes two 6-inch models, an 8-inch and a 10-inch model. The HL-06 lathe, for example, features 1,181 ipm rapid traverse in X and Z axes, with an optional 6,000 rpm spindle. For this model, the company has published a case history involving a 2.25-inch bar of 303 stainless steel machined with a carbide insert at a depth of cut of 0.04 inch and feed rate of 0.004 inch. With a spindle speed of 2,800 rpm and surface speed 1,680 fpm, resulting surface roughness is given as 0.00006 inch and circularity is given as 0.000031 inch TIR. In another example, the HTL-80, an 8-inch lathe, performed a rough cut on 1046 steel with an 0.08 inch DOC at 1,640 sfm producing a 3.4 micron surface finish. This operation consumed a half ounce of coolant per hour.
The two VMCs in the line are both designated as 40-inch models. The HV-40 is slightly smaller, with 30 by 17.7 by 19.7 inch axis travel and 7.5 hp compared to the HTV-40 with 40 by 20 by 20 inch travel and 10 hp. Both models have optional spindles, with an HTV-1000 model offering 10,000 rpm. All of the Hakusui lathes and VMCs are equipped with Fanuc controls.
The ECOREG System is also available as a stand-alone unit, model MRC21, which can be retrofit to existing machine tools.