Why is leak detection so important? Due to the complex operation of new multi-speed transmissions, transmission-fluid leaks can significantly affect performance. Detecting leaks at the earliest stages of manufacture, post-casting and pre-assembly, improves quality and customer satisfaction while reducing costs.
KUKA Assembly and Test Corporation, for example, has developed leak-detection systems that are faster and more reliable than more traditional air-test methods. KUKA systems now use INFICON helium-leak detectors to test advanced transmissions such as newer aluminum automatic 9- and 10-speed transmissions.
"Historically most leaks are discovered at or after final assembly," notes Steve Kurzava, a KUKA technical specialist. "KUKA systems equipped with INFICON helium leak detectors can be used to detect leaks soon after the original casting takes place, reducing cost by eliminating defective castings early in the build process."
KUKA's automated leak-test processes use part-specific fixtures that allow transmissions to move automatically from tooling station to tooling station. The transmission is inserted into a sealed enclosure injected with helium and connected to an INFICON leak detector. Any helium that passes through cracks, tiny holes or any other pathways can be quickly detected and quantified by the leak detector.
"Helium leak detectors are much more accurate than air or underwater testing methods for identifying porosity leaks," explains Thomas Parker, INFICON's automotive sales manager for North America. "Cast aluminum products, for example, may have a one-inch diameter area with up to a trillion holes that helium molecules can migrate through. Porosity of this kind could never be detected by air or water testing."
The INFICON executive adds that leak points don't necessarily look like cracks or perfectly circular holes. They may resemble a cave-like system of cracks and pockets within the metal. Air-pressure testing actually might take days to detect these types of leaks. Helium leak detection on the other hand takes seconds with a total part-to-part test time of roughly 30-40 seconds.
"If you have a material with potentially a trillion holes per square inch helium or trace gas testing is the only method a manufacturer can use to find a leak," Parker says. "Pressure-decay or mass-flow testing simply won't find porosity created by millions of near-molecular-sized leaks. Thinner, weight-saving component walls can create potential porosity problems as well."
Helium testing is superior to other more traditional methods in a number of other ways as well, according to both KUKA and INFICON. Compared to helium, air tests can be significantly affected by changes in temperature caused by hot or cooling components. They also take longer when larger components are involved.
Manufacturers may test transmissions with helium at the end of the production line as well. The finished transmission is filled with helium and sealed inside a vacuum chamber. If a leak exists, the helium molecules can be detected as they emerge from the transmission. The process is designed to replicate and identify transmission-fluid leaks that might occur under normal operating conditions.
In comparison with other helium leak detectors, Parker notes that INFICON customers report that its cost-saving LDS3000 leak detectors provide faster cycle times, faster clean-up times and more repeatable results. Because of their sensitivity, INFICON detectors also require only a small amount of helium, reducing cost-per-test to approximately nine cents per part.
INFICON is one of the world's leading developers, producers and suppliers of instruments and devices for leak detection in air conditioning, refrigeration and automotive manufacturing. The company has manufacturing facilities in Europe, China and the United States, as well as sales and service offices throughout the world.
More information about INFICON automotive technology is available online at www.inficonautomotive.com