If you find yourself cleaning out coolant tanks more frequently than you’d like—and hating every dirty minute of it—you have a lot of company … and a solution. MP Systems, East Granby, Conn., has engineered a compact unit that connects to virtually any standard tank, filters out fines and swarf, and returns a high volume of clean coolant to the machine with minimal maintenance, according to the company. Customers, ranging from shops with big horizontal machining centers (HMCs) running 24/7 with water-based coolant, to Swiss-turn machines running with oil, report excellent results.
Micro-Mechanics is a good example. A multinational company making high-precision parts for the semiconductor industry, its U.S. operations are in what CEO Chris Borch described as the most expensive geography in the world—Silicon Valley. The company’s goal is to keep nine Makino a61 4-axis HMCs running 160 hours per week, with much of it “lights-out.” As Borch sees it, that’s the only way to compete in this environment. And “the right way to think about costs is not how much the machines cost you, but how much they cost to run per hour,” he said. Even a multimillion-dollar machine has a surprisingly low hourly running cost if it runs around the clock, Borch pointed out.
One flexible manufacturing system (FMS) serves 500-mm pallets to six machines while another FMS serves the other three machines, and each HMC has over 300 tools in its changer. They’re set up to make a lot of parts, and that results in a lot of material for the coolant system to handle. In fact, Borch identified coolant problems as the company’s “number one root cause of lost hours. A pump clogs, or becomes defective, or you’ve got to tear down the tanks and take the conveyor off and clean out an area because this sludge builds up.”
That’s because the HMCs at Micro Mechanics, like most of its machines, came with chip conveyors that take away only the larger chips. As Borch explained, “small chips and fines don’t evacuate through the conveyor system. They just settle down into the sump. And the way the industry has traditionally dealt with this is to evacuate the tank, get in there, and scoop them out. But it’s a really messy and dirty job. It takes time, and, of course, your machines are down.”
Besides the frequent irritant of unplanned downtime due to things like clogged pumps, Borch said Micro-Mechanics typically needed to clean out the sump on each machine every three months. He calculated the time required to clean a tank and get it back into production totaled from 12 to 24 hours per machine. With nine machines, that meant losing an average of 54 hours of production per month, plus tying up two operators with onerous, non-value-added work. After suffering with this for months, Borch decided to try the Purge filtration system from MP Systems. With a Purge unit, the maintenance cycle immediately switched to a five-minute process of changing out inexpensive filter bags every three weeks. Just to be sure, Borch said, operators evacuated all the coolant from the tank after three months to take a look. “The tanks were so clean it looked like they’d been polished,” he said. “It’s been a huge benefit because it’s eliminated having to manually clean out the sumps. This product is a home run.”
A Purge system works right alongside the standard coolant tank and requires just a few square feet of additional space. First, a debris pump pulls dirty coolant up from the machine’s tank near the conveyor’s outlet (or the “dirty side of the tank”), typically at a flow rate of 30-60 gpm. The pump is engineered to handle small fines and swarf without significant wear, reported Kyle Quintin, product development manager at MP Systems.
From there, the dirty coolant passes under pressure through filtration canisters in the nearby Purge tank. The filter media is an industry standard 7" deep × 32"- (17.78 × 81.28-cm) long bag, and Quintin reported that the vast majority of applications can be satisfied with 5 μm bags. A typical Purge has four such bags. After the fluid passes through the filter bags, the now clean coolant flows down from the Purge into the clean side of the coolant tank at the same rate as the input (e.g., 60 gpm).
From there, the machine’s coolant pump(s) supplies the machine with clean coolant at a lower flow rate than that which supplies the Purge (e.g., 40 gpm). Quintin explained that this arrangement maintains positive flow of clean coolant against the mesh separating the clean from the dirty side of the tank. Because of this, the debris in the tank is always being encouraged to flow towards the Purge inlet so it can be filtered and delivered back to the clean section of the tank, where the coolant pump(s) need it most.
Quintin also explained that the Purge monitors the incoming pressure, which increases as the filters get dirty. “Based on that pressure, we can calculate how much filter life is left, or how close the system is to no longer being able to maintain an adequate flow.” A blue light flashes when the bags are near full, a screen tells the operator to change them, and the debris pump automatically turns off if the bags become completely full. Changing bags is as simple as loosening four wing nuts at the top of each canister, lifting out the full bags, dropping in clean bags, and tightening the nuts, a process that takes under five minutes.
“And the best part is you don’t have to shut your machine down while you’re doing this, because it’s an auxiliary system that’s off to the side,” said Quintin. “The beauty of the Purge unit is that it’s a complete, ready-to-go, easy-to-install package. And it’s compact. Floor space is precious in a shop and it’s hard to add peripherals to your machines after your area is configured. So it’s been very exciting for people to find a small-form-factor, easy-to-install system and get the thing up and running in a few hours, with no problems.” According to MP Systems, the Purge system pays for itself within a year or so in added machine time, while freeing operators for more productive tasks.
At Fiberglass and Composites Technologies (FACT), Wichita, Kan., machining fiberglass pipes and fittings on CNC lathes produces chips that can easily be captured in a standard conveyor. But it also produces a huge amount of dust that can’t be, reported Plant Manager Rick Davis. FACT floods the cutting zone with coolant not to preserve tool life, Davis explained, but to “rinse everything down and prevent the dust from flying everywhere.” The problem though, said Davis, is “within two months, three-quarters of the tank is full of sediment.”
At that point, FACT would experience flow problems and a lack of pressure at the nozzle in the machine, because the pump was starved for coolant. Davis was also concerned about premature wear in the pumps due to the recirculating fiberglass. At first, the only solution was to pull the tank and clean everything out, a process that took a full day. That wasn’t a maintenance cycle Davis could live with, so FACT invested in a four bag Purge system.
Now, the routine is to pull the bags out about ¾ of the way at end of business Friday and let them drain over the weekend. “That way, you’ve captured 99 percent of the coolant that was in those bags,” explained Davis. “Then on Monday we throw the old bags in the dumpster and put in new bags. It’s a really simple process for us.” If the size of the product FACT is machining causes the bags to fill faster, that’s not a problem, he said, because “the alarm system works very well.” It’s just a matter of changing the bags a bit earlier than usual.
It was the challenge of machining a titanium ultrasonic blade for brain and spinal surgery that led Swissline Precision LLC, Cumberland, R.I., to the Purge. As the biggest Tsugami Swiss-turn user in North America, with over 56 machines, Swissline is experienced at sustaining high throughput with tight part tolerances. However, the pinch milling process it was using on this family of blades produced a fine chip that prevented the machine from achieving the expected output. As President Mike Chenevert recalled, “the stock machine has the usual baffles in the oil tank, arranged in different layers to trap the chips. But the little fines that we get from machining titanium just float in the oil and then go right through everything.”
Chenevert added that the application requires high-pressure coolant for adequate chip evacuation (to prevent marring the surface of the part), and that requires a relatively high coolant volume. Also, the risk of fire when machining titanium puts a premium on ensuring that the cut is always immersed in oil. But the filtration problem was so bad that Swissline was pulling the tank and cleaning everything out almost weekly. What’s more, the need to frequently deal with coolant alarms and chip buildup inside the machine in the days before pulling the tank prevented Swissline from setting up any unattended operation.
Installing a Purge unit turned the situation around. Now the weekly, or sometimes bi-weekly, maintenance schedule entails changing the filter bags, which Chenevert confirmed “literally takes five minutes. We’ve increased production. We’ve minimized the amount of machine downtime. The oil is cleaner. And the tools are lasting a little bit longer because the oil doesn’t have as much residual titanium in it. We have seen less wear on the tooling and have been able to continue running. We’ve added five to ten additional parts per insert, which all adds up in the long run.”
On top of that, Chenevert explained, Swissline has gained an extra 42 hours of unmanned operation over the weekend. “On Saturday, the operator sets the machine to run when he leaves at noon, and that thing does not stop running until he comes in on Monday morning.” That alone would pay for the unit in about two weeks, according to Chenevert.
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