One-sentence answer: Drive motor housings are mostly one-piece die-cast aluminum parts with an integrated cooling jacket. Poor sealing at die-casting micro-porosity, cooling jacket partitions, and end cover mating faces allows coolant to seep into the motor cavity, and external moisture to intrude into bearings and magnets. Using the CTS Sentinel A28 differential pressure leak detector, the housing and cooling jacket air tightness is tested by comparing a master part with the part under test, which maximally cancels out false judgments caused by temperature fluctuations in the die-casting workshop, making it suitable for 100% inspection on high-volume production lines.
Die casting porosity, jacket baffles and end cover mating faces let coolant into the motor cavity and moisture into bearings and magnets
Motor housings are mostly one-piece die castings with uneven wall thickness, and gas entrapment is likely near the gates. Micro-porosity may hide in locations such as bearing bore walls and the roots of cooling jacket partitions that only become through-holes after machining, making it difficult to intercept all of them by appearance and non-destructive testing alone.
The cooling jacket, motor stator cavity, and terminal box cavity are independent of each other, each with its own sealing interface and volume. A single charge of air cannot determine which layer has failed, so they must be plugged and judged separately.
Housings that have just come off the die-casting and machining processes are hotter than the ambient environment. The gas inside the workpiece continuously releases heat, shifting the entire pressure curve and easily judging a conforming part as out of tolerance.
There are three main sealing locations:
Consequences of leakage: coolant enters the stator cavity, the winding insulation resistance drops, and inter-turn short circuits occur, in severe cases burning out the motor; conversely, if external moisture intrudes, bearing grease emulsifies and magnets corrode and lose magnetism, manifesting as abnormal noise and torque attenuation.
The motor housing cooling jacket is a small-volume, multi-cavity, high-volume workpiece, and the difficulty in judgment lies in distinguishing true leaks from temperature drift:
If the housing volume is particularly large, or multiple test methods need to be combined in series within one instrument (for example, cooling jacket pressure decay with stator cavity vacuum decay), the multifunctional single-station model I28 can be selected.
Yes, they need to be tested separately. The cooling jacket cavity and the stator cavity are two independent sealing interfaces, and the consequences of leakage are completely different, so they must be plugged and judged separately. The A28 can establish an independent test program for each cavity and call them up in sequence on the same instrument.
It can intercept micro-porosity that has become through-holes to the surface. Air tightness testing reflects the overall leak rate of the cavity; as long as the micro-porosity connects the inside and outside and the leakage exceeds the test program limit, it will be judged out. Subsurface porosity that has not become a through-hole does not affect the current sealing state and is usually not included in the judgment.
Give priority to the differential pressure method. The A28 compares the master part with the part under test, which maximally cancels out errors caused by ambient temperature fluctuations; at the same time, let the workpiece rest at the test station until it is close to the ambient temperature, reducing interference from its own residual heat on the pressure curve.
In sealing tests for drive motor housings, the key is to stably distinguish true leaks on multi-cavity workpieces with residual heat. The differential pressure comparison structure of the CTS Sentinel A28 directly addresses this point, and together with custom plugging fixtures and 32 test programs, it can cover the 100% inspection needs of high-volume production lines for different motor models.
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