Page 29 - MetalForming December 2014

cut parts, our customers avoid the need to perform secondary machining operations or other edge-finishing processes such as grinding. Waterjet- cut parts can head straight to welding or other operations.”
Jacquet’s waterjet-cutting machines of choice are large-format (13 by 21 ft.) mid-rail-gantry setups from Jet Edge, Inc., St. Michael, MN. Of Jacquet’s 11 machines in use in the United States, six comprise the mid-rail design, which Jet Edge introduced in 2008. Its other, older machines are low-rail models, no longer manufactured.
“The mid-rail machines (precision ballscrews, Rexroth drives and motors and Servos digital communication) are incredibly accurate,” Engle notes, “with
repeatability to ±0.001 in. And we work with Jet Edge engineers to ensure that the machines meet our strict require- ments for providing tightly toleranced parts along with reliable on-time deliv- ery meeting ever-shrinking lead times.
“We’ve seen lead times reduced by 50 percent in the last few years,” Engle continues, “from 10 days down to just five days, and we expect them to shrink to three days very soon. So, our focus with these new machines not only is on speed and accuracy, but on uptime. We cannot afford the machines to be down for unplanned maintenance. That means jet Edge must focus devel- opment, design and manufacturing on ensuring its machines are rigid, robust and reliable.”
The firm often runs its cutting machines 24/7, further emphasizing the need to maximize overall equip- ment effectiveness (OEE), a measure tracked closely at Jacquet. Aiding in that mission is a proactive and thor- ough preventive-maintenance plan (see sidebar).
Dual Heads, Plus Beveling
Further enhancing service-center throughput: all 11 of Jacquet’s water- jet-cutting machines are dual -head models, and are run off of 100-hp intensifier pumps. Standoff between the heads is adjustable either auto- matically (through the cutting pro- gram) or manually.
Adding the second cutting head
10 Tips for Maximizing Waterjet Uptime
...provided by Jet Edge, Inc., St. Michael, MN; www.jetedge.com.
Successful waterjet operations like those at Jacquet rely on the performance of proper routine maintenance on the machines. With waterjet operating pressures often exceeding 75,000 psi (5200 bar), proper maintenance will help ensure maxi- mum uptime, productivity and profitability. It can mean the differ- ence between winning and losing customers, and retaining exist- ing customers.
Neglecting a waterjet system can result in costly downtime, lost opportunities and expensive yet preventable repairs. At ultra- high pressure, small leaks left ignored can turn into big and costly problems. Hydraulic oil left unchanged can break down and gum up a pump’s directional control valve, causing the pump to stop working. Cooling systems that are allowed to clog with mineral deposits can cause a pump to shut down. And, improperly torqued high-pressure components can cause short seal life and premature component failure.
Fortunately, all of these problems can easily be avoided by following your waterjet-manufacturer’s maintenance guidelines and taking the time to properly maintain your equipment. Here are 10 tips for preventing many of the common problems associ- ated with improper waterjet-cutting machine maintenance.
1) Read, understand and follow the procedures in the manufac-
turer’s maintenance manual and take advantage of manufac- turer training programs. Jet Edge offers its customers free training for the life of its machines every other month at its Minnesota headquarters.
2) Keep the pump cool. Hydraulic intensifier pumps use a heat exchanger to cool the pump’s hydraulic fluid; direct-drive pumps use water to cool the interface plate between the plunger pump and the high-pressure assembly. Cooling can be accomplished with a closed-loop chiller or with tap water— tap-water temperature should not exceed 70 F. If your water contains heavy mineral deposits, filter and soften it to mini- mize the deposits within the intensifier pump’s heat exchang- er, and periodically clean the heat exchanger following the instructions in your maintenance manual. If excess scale develops within the heat exchanger, it will not efficiently cool
the pump’s hydraulic fluid and the pump will shut down.
3) Use clean and cool water. Jet Edge recommends that cooling
water and incoming process water be no warmer than 70 F and that it be pretreated to <100 TDS, PH 6-8, Silica <15 PPM. Replace pump water filters after every 250 hr. of opera- tion, or possibly more frequently depending on local water conditions.
4) Hydraulic fluid must be clean. Follow the manufacturer’s guidelines for replacing hydraulic fluid and hydraulic and breather cap filters. When changing the fluid, take care to not contaminate the new fluid by keeping the working area around the system dry and free of dust, dirt and debris.
5) Closely follow the manufacturer’s pump startup and shutdown guidelines. Bring the pressure up slowly when powering on the system and bring the pressure down slowly when shutting down the system.
6) Properly maintain high-pressure components and seals. Replace leaking seals and tighten high-pressure leaks as soon as they occur. Even a small leak, if neglected, can cut a groove into an expensive high-pressure component, forcing you to spend time lapping the component or replacing it. Use two wrenches to tighten high-pressure fittings. When replac- ing intensifier seals, follow the manufacturer’s torqueing guidelines; improper torqueing often is the cause of premature pump-component failure and short seal life. Inspect and serv- ice high-pressure tube poppets when necessary, and follow maintenance guidelines for servicing the on/off valve and rod seal.
7) Keep the pump and motion system clean and well lubricated. 8) To maintain a consistent level of quality, have the motion sys- tem recalibrated periodically by an experienced technician. 9) Use quality orifices and monitor the orifice, nozzle and mixing
chamber to ensure optimal cutting performance. An abrupt pressure loss often can be attributed to a damaged or blown- out orifice.
10) Use quality, clean and dry garnet and ensure that debris does not fall into the abrasive hopper when filling it. Supply dry air to the abrasive hopper.
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