Machined cast housing are often an integral element of an electric vehicle’s design. These castings are essential for areas of EVs where reducing weight and increasing rigidity is required to maintain the integrity and protection of the enclosure. Channels are also often cast into the housings to provide cooling to the temperature-sensitive components housed inside the castings.
For example, the electric drive unit (EDU) has a cast housing for rigidity and lightweighting purposes. A cast housing can be very complex, with features that are designed into the product that increase its structural integrity, provide essential cooling functions and reduce the overall weight of the product. For EVs, lower weight means greater range.
These cast housings must be leak tested to identify any vulnerabilities that could impact the parts and components being protected. This could include testing for water and debris ingress in some applications, like around the battery enclosure, drive unit housing, or power electronics modules for example.
Leak testing cast housings can be challenging due to the potential large size of the assemblies, porosity of the materials, as well as the requirements of the test; they often need to be highly repeatable and reliable, with very small acceptable leak rates at times. Overcoming these challenges requires an understanding of all the test variables and the right test methods to provide compensation and control.
Technology Used for Leak Testing EV Cast Housings
Differential Pressure Decay
The most common method for leak testing EV cast housings is pressure decay using differential pressure measurement. In a pressure decay test, the drop in pressure on the interior of a part is measured to identify a leak. Air is injected into the device until it reaches target pressure, then cut off and isolated. The loss of pressure (decay) is then measured over a specified period of time to calculate the leak rate.
Differential pressure decay leak testing is similar to pressure decay, but instead of testing the pressure drop with a full range absolute transducer, this method measures the pressure change between a reference volume and the test part volume, using a differential pressure transducer. The differential pressure transducer is typically a smaller ranged transducer with more resolution, plus this method of comparison compensates for the thermal event that occurs from pressurizing a part up to test pressure. This provides a quicker test and higher level of sensitivity than the standard pressure decay method, ideal for many EV cast housing leak test applications.
Pressure is typically tested in ranges around 4-60 psig, and leak rates in the range of 6-15 scc/m, dependent upon the leak path and porosity.
Examples from the Plant Floor
CTS has over 40 years’ experience designing the best leak test solutions for automotive manufacturers. Cast housing are an integral part of internal combustion engines and continue to be an integral part of electric vehicle design. CTS continues to innovate to meet the needs of the everchanging automotive industry, delivering the best leak test solutions for electric vehicle components. Below are a few examples of machines CTS has designed and built for cast housing testing on electric vehicle production lines.
Leak Testing of EDU Housing (machined casting)
This test stand was designed to test a large electric drive unit (EDU) enclosure (EDU not pictured). In this case, testing is done with a Sentinel 3520, ideal for balancing accuracy, cycle time, and Gage R&R in complex, large part leak testing applications due to its unique ability to compensate for temperature, atmospheric and barometric fluctuations affecting large part leak tests.
The above machine is designed with a filler block which enters into the part in the nest. The system then runs a pressure decay leak test, immediately flagging any failed, leaking parts for investigation and repair.
Leak Testing of EV Gear Cast Housing
This test stand was specially designed to test an EV gear housing using the Sentinel I28. In this test, the housing is placed over a filler block with a speciality seal to accommodate a half-moon machined characteristic used as a bearing housing inside the assembly. Using this specialty seal, we are able to seal both components properly for a robust, repeatable measurement using differential pressure decay leak test.
Trust the EV Leak Testing Experts at CTS
CTS has been a leader in automotive leak testing for over 40 years. In this new era of electric vehicle manufacturing, we continue to innovate and apply our decades of knowledge and time-tested technologies to the evolving needs of the industry. Our methods and technologies continue to be the most reliable and repeatable on the market. Contact the experts at CTS for your new EV line or improved performance on your current lines.
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