Hybrid machine tools—those that provide multiple machining processes, such as turning centers that also do milling, or machining centers that can turn and face parts—can have an impact lowering in-process inventory levels and improving quality through single machine handling. Unfortunately these same machines, by offering multiple processes, also produce a more diverse selection of chips, from large to small, strings and curled springs, to fine dust-like particles, depending upon the application's material. And they can produce a lot of it in a very short time—to the point where conventional chip handling and coolant recovery systems can be overwhelmed by both the variety and the amount.
Such was the case at the Pohlman, Inc. manufacturing facility in St. Louis, Missouri. This Tier II automotive supplier machines various vehicle components, with particular emphasis on the processing of air bag and SRS parts. According to Mike Keithly, project engineer at the plant, it was one manufacturing cell, consisting of two Turmatic machining systems processing aluminum SRS canister housings, that presented a special chip handling challenge.
"The two machines run 24 hours a day, seven days a week, each processing over 60,000 of the housings per week," Mr. Keithly says. "The machines are set up to drill, thread mill, mill and turn a variety of features on the impact-formed housing blanks, producing everything from fines and small particles to long strings from a facing operation. And, they produce a lot of chips—up to 210 cubic feet of chips per day, per machine. The machines themselves provide excellent performance, day in and day out, but the chip and coolant handling conveyors and wedge wire filters were unable to produce clean coolant, resulting in a loss of productivity we could not accept and still meet the demands for delivery to our customers."
Mr. Keithly points out that every week the machines would have to be shut down anywhere from 8 to 12 hours, roughly 5 to 8 percent of their projected spindle run time each week, to clean chips and fines from the machines' 800-gallon coolant filtering systems. "Any longer than that, and coolant levels would back up and overflow," he notes. "We also saw that chips were passing through to the ‘clean side' of the system, meaning the potential for blockages was greater, resulting in reduced coolant flow, which in turn is detrimental to tool life and can affect dimensional and surface finishes. Plus, these clean side contaminates, recirculating through the system, can increase maintenance requirements of mechanical operating units, such as pumps, bearings, spindles and feeds of the machines."
Given the task of improving the uptime for these two machines, Mr. Keithly and his team of machine operators sought out enhanced chip and coolant handling systems that would both reduce the time required for cleaning and better protect the machines' components, tools and part quality. They found their solution in one unit—the new ConSep 2000 from Mayfran International (Cleveland, Ohio). Mayfran developed the ConSep 2000 to be compact. It is a combination of chip removal conveyor/coolant filtration unit, all in one small footprint.
The ConSep 2000 system is designed to replace traditional turning or machining chip conveyors, requiring little more space yet cleaning and filtering coolant at the same time. The basic unit, which can be easily modified to suit application heights and lengths, handles virtually all types of swarf including ferrous and nonferrous strings, turnings, fines, curls and nests.
The standard system consists of a hinged and perforated steel belt conveyor for high volume chips, plus a lower drag conveyor and filter drum for removal of fines. Large chips and strings are simply carried away to the chip discharge chute by the steel conveyor as coolant flows down to the lower area containing the drag conveyor and filter drum. The coolant is maintained at a level below the height of the steel conveyor, helping to drain residual fluid from chips, plus minimizing coolant foaming conditions and the problem of floating chips.
The filter unit separates fines to 50 micron nominal and features a self-cleaning, pressurized backwash for the drum's poly fiber media. The lower conveyor then picks up and carries off the fines. The over/under locating of the two discharge chutes allows chips and fines to be collected in the same hopper. The pressurized backwash system for the mesh filter means less downtime for manual cleaning.
The ConSep series of chip handling/coolant filtration units stops chip migration to clean side tanks, thus providing longer tool life, improved part tolerances and finishes, and results in coolant fluids lasting indefinitely. Another bonus is the elimination of maintenance downtime, as sumps do not need cleaning as is the case with most standard coolant recovery systems.
"Since the installation of the new ConSep 2000s, and except for one time when coolant was mistakenly contaminated with hydraulic oil, we've not had to shut down the Turmatics because of any problems with chips or coolant," Mr. Keithly reports. "In fact, over one night shift, one of the machines ran with the pressurized backwash cycle accidentally shut off. In the morning, when coolant levels and flow were noticeably down, we thought we'd have to stop production and manually clean the filter. But first the operator started up the backwash cycle—in no time at all the filter was automatically cleaned, and we were back into full production."
Mr. Keithly does relate that, initially, there was a slight problem with the first ConSep 2000 unit installed. "After just a few hours of running," he says, "we noticed coolant flow and the amount of chips were creating a backflow, allowing particles to become lodged in the clutch assembly of the hinged, steel belt top conveyor. This would cause it to kick out and disengage. We notified Mayfran, and they were at our facility the very next business day, reviewing the application. The company's solution, replacing the hinged conveyor with one of similar design and material as the lower drag conveyor, resolved the problem immediately. The second ConSep 2000 was similarly modified before delivery. Since April of 1999 both ConSep 2000s have worked to perfection."