Overcoming challenges to leak test a large volume, flexible, die cast part
to IP67 specifications
High-voltage boosters are becoming an important part of electric vehicle design as higher power EV powertrain systems enter the market. These HV boosters, or inverters, allow for these new, higher performance systems to be compatible with the current charging infrastructure.
The introduction of this higher voltage technology poses a new challenge for manufacturers. These HV boosters must be tested to meet high performance demands and perform reliably in the field. Leak testing is one of the tests that must be performed during the manufacturing process to ensure product quality and reliability.
An automotive OEM manufacturer of high-voltage boosters recently came to innomatec with a project: They needed help to create a leak test for their new HV booster inverter assembly line. This application came with a variety of complexities, but the manufacturer had recently switched over to innomatec leak testers on another product line in their plant and knew they could trust innomatec to deliver a reliable, accurate result.
Overcoming challenges: Multi-channel leak testing for a large volume, die cast housing to meet IP67 specifications
Many factors made this application complex, including elements of the product design and the strict test specifications they needed to meet. Specific challenges included:
The manufacturer needed a cost-effective and reliable test, and a team they could trust. Read on for the details of how innomatec designed this test to deliver a reliable, repeatable leak test despite the complexities of the design and specifications.
Designing an accurate, repeatable leak test process for high-voltage boosters in electric vehicles
innomatec’s LTC-902 multi-channel leak tester and connec® quick connection seals were used to meet the needs of this challenging application, able to provide the flexibility and control to accommodate leak testing large volume parts, expanding parts, die cast, porous parts, and more.
The LTC-902 multi-channel leak tester allowed the manufacturer to run the multiple different test cycles and test types required for this complex application using one leak test instrument, and innomatec’s connec® seals offered the best performance, particularly when dealing with die cast surfaces.
Beyond providing superior leak test equipment, the innomatec leak test experts also helped make some alterations to the manufacturers’ original suggested leak test approach in order to make the process more effective and efficient. This included moving an addition electrical test to a separate test station, as the combination of the electrical test after the leak test was proving expensive and less effective.
Below is how innomatec provided the best leak test solution for high-voltage boosters:
Step 1: Leak testing the cooling circuit
The first step of the leak test for the high-voltage booster was to test the cooling circuit, which prevents overheating from occurring in the inverter. The cooling circuit was tested using the pressure differential method. Using the pressure differential method, the leak tester measures the change in pressure over a certain period of time in relation to a reference volume. This leak test method provides a very accurate, high-resolution measurement needed to ensure there was no leakage out of the cooling circuit. The high sensitivity of the pressure differential method allowed testing at the required low pressures (2.7 bar) and low leakage rates (2 ml/min), while maintaining a fast cycle time.
Step 2: Leak testing the die cast housing
The next step was to leak test the die cast housing unit of the high-voltage booster. The manufacturer had intended to use a mass flow test method for this process, but innomatec advised them to use the pressure change method instead. Due to the long cycle time, it was possible to increase the pressure drop signal by extending the measuring time. This enabled more stable test results.
The housing was a large volume (6 L) and needed to be tested at a negative pressure (vacuum test) (-0.4 bar relative) for a low leak rate (4 ml/min) to ensure there were no cracks or deficient sealings—and that it could meet IP67 rating (water-tight) standards.
Using the pressure change method, the part is subjected to underpressure and the pressure change is determined over time. The measurement result is then output as a leakage rate.
This application required the added challenge and consideration of the flexibility of the die cast part. This meant that it was not pressure stable and would contract, with the potential to skew measurements and test results. To accommodate for the flexible nature of this part, this test was designed with a slightly longer fill cycle time. This action ensured an accurate leak test result.
Step 3: Blockage testing for the membrane
The test cycle concluded with a blockage test to confirm the presence of the membrane (pressure equalizing element) and identify any blockages. To perform the blockage test, the test port on the pressure equalizing element is vented for a period of 1 second then closed again, followed by a pressure change test. This pressure change indicates whether the membrane is present, or if it is blocked.
The ability to perform this blockage test immediately following the previous two leak tests, using the same leak tester, was unique to innomatec’s solution and added much-appreciated ease to the process for the manufacturer.
Before final delivery of the solution to the manufacturer, innomatec ran a measuring system analysis comparing the results of 25 test cycles to ensure measurements were reliable and repeatable, proving the manufacturer could rely on their new leak test process to ensure the quality of their products.
Get the best leak test solution with innomatec—a leak test company you can trust
Having reliability and trust in their test—both from leak test design and the expert service and support from innomatec—was very important to this manufacturer of HV boosters. The leak test team at innomatec proved themselves to be true leak test specialists, answering all questions, offering advice and improvements to their proposed processes, and ultimately, building strong trust with the customer.
Does your team need help designing or improving your leak test process? The team at innomatec is here to help. Contact us today!