Leak Detector Checks Fuel Tank Valves
In order to move production, the quality control testing system had to be updated to include documentation of each valve's compliance with buyer specifications for actuating pressures, flow and leakage rates. "We could not bring the valve manufacturing responsibility to Canton until we could demonstrate our ability to fulfill valve function tests reliably, and at volume production rates," said Kevin Holcomb, plant engineering director for Piolax.
Having a new testing system built in the U.S. made the most sense, said Holcomb. Other options involved either moving the test system from Japan, which would disrupt production, or designing and building the system in Japan and shipping it to America, which would also be cost prohibitive.
Building a new system also meant the system could be improved. The test process in Japan started out by manually placing each valve into a receiving nest. The machine would then automatically move the part through a sequence of three test fixtures, and on to the final assembly. Holcomb said he wanted a system that would eliminate these steps, and conduct all tests in a single fixture with automated in-feed at faster speeds with fewer false rejects. A system with a single fixture means fewer moving parts and seals, and takes up less floor space. The system also had to stamp dates on the caps during final assembly. This date serves as a lot number and identifies all parts that were made within a 24-hour period.
The company chose InterTech Development Co. (Skokie, IL) to develop a system that could do flow and leak-rate testing with full automation and assembly. Inter-Tech designed a system around their M-1035 Mass Flow Leak Detector. It was built with a programmable air regulator for both positive and negative testing, and low and high range transducers to accommodate the wide range of pressure, vacuum and flow rates specified by Piolax.
The vacuum cut valve has an 8-piece assembly that requires intricate testing procedures. The valve has a cylindrical body no bigger than a golf ball with four 1-inch hose connection tubes, which look like two parallel legs and two widespread arms, all molded of white Polyoxymethylene plastic. When assembled, these parts enclose and control two airways. One arm connects via hose to the fuel tank, and the other arm connects via hose to a canister that accumulates vented vapors from the engine burn. The two legs link both airways to a bypass valve, which allows a failsafe venting of vapors to the atmosphere in emergencies.
A key feature of the system is a vibratory bowl feeder that accumulates the assembled valves and delivers a continuous stream to the test stand where a pick-and-place gripper transfers pieces into the test fixture. The tester is kept supplied by two operators. "What's nice about bowl feeding, is that the assemblers can take a break or go to lunch, but the valves keep moving through the tester as quickly as possible," said Holcomb.
The test part stays in a single nest through the entire sequence of six tests. Each test introduces a new test variable to the part, such as air flow through the tank side, pressure drop across the valve, vacuum leak testing applying negative pressure at the canister, and leak testing, which applies positive pressure simultaneously through both arms. The entire test sequence takes about 25 seconds, part-to-part.
"We began making vacuum cut valves in March of 1999, and because of the tester's automated feeding, we were able to support three shifts of testing with only two shifts of assembly," said Holcomb. "Volume kept growing, and by the end of the year, we needed third shift assembly, raising production to around 40,000 pieces per month."
The system displays real-time flow rates and pressures on a vacuum fluorescent display. A green or red indicator light tells operators if a part has been accepted or rejected. All the tests on the valves are stored and monitored using InterTech's 2058 software, which can graphically display recalled data as test dynamics, print the data or download information into a database.
"Thanks to a reliable and efficient testing process, our vacuum cut valve production to the U.S. has not only reduced the part's cost by about 20%, which enables us to stay competitive, but also has helped to push our reject rates down to about 3% with minimal retesting," said Holcomb.
InterTech Development Co.
(847) 679-3377 Reply 11