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Case Overview
This case involves an automotive cooling water pump housing (water pump housing), which is an important structural component of the automotive engine cooling system. The automotive water pump is installed at the front of the engine and is driven by the engine through a belt. It is responsible for forcibly circulating coolant through the engine cylinder block water jacket and radiator to remove heat generated by engine combustion and maintain the engine within its optimal operating temperature range (approximately 85–95°C). As the main structure of the pump body, the water pump housing accommodates the impeller, incorporates inlet and outlet chambers, and fits tightly against the engine cylinder block through a sealing gasket to form a complete coolant circulation passage.
Therefore, this component needs to withstand coolant pressure and repeated heating and cooling cycles during long-term engine operation. The internal quality and sealing performance of the casting directly affect the stability of the cooling system.
In this project, the component is die-cast from ADC12 aluminum alloy and undergoes shot blasting to improve surface quality, meeting the requirements of automotive water pump housings for structural strength, internal density, and long-term reliability.
Part Information
| Item | Parameter |
| Part Name | Automotive Cooling Water Pump Housing (Water Pump Housing) |
| Application Industry | Automotive Engine Cooling System |
| Part Function | Serves as the main structure of the water pump, forming coolant flow passages and supporting internal components such as the impeller |
| Material / Grade | ADC12 Aluminum Alloy |
| Product Dimensions | 88 mm × 92 mm × 96 mm |
| Average Wall Thickness | 4.0 mm |
| Maximum / Minimum Wall Thickness | 4–5 |
| Product Weight | 330 g |
| Manufacturing Process | Aluminum Alloy Die Casting |
| Surface Treatment | Shot Blasting |
| Quality Inspection | X-ray Inspection |
Project Difficulties and Technical Challenges
Core Challenge: High Air Tightness Requirement
The automotive water pump housing is a functional sealing structural component. Its interior needs to form a stable coolant circulation passage and continuously withstand coolant pressure as well as the effects of heating and cooling cycles during engine operation.
If defects such as pores, shrinkage porosity, or microcracks exist inside the casting, they may be exposed in the sealing area after machining and form coolant leakage paths, resulting in reduced water pump efficiency and potentially affecting the normal operation of the engine cooling system.
Since the die casting process uses high-speed filling and rapid solidification, residual gas in the mold cavity, gas entrapment in the molten aluminum, and solidification shrinkage may all cause internal defects. Therefore, reducing the risk of internal defects and improving casting density are the core challenges in manufacturing this water pump housing.
The product measures 88 × 92 × 96 mm and weighs approximately 330 g, making it a compact aluminum alloy housing structure.
Although the overall dimensions are relatively small, the product contains complex structures such as an impeller chamber, water flow passages, and mounting bosses, while also featuring significant variations between thick and thin sections:
- Thin-wall areas require high filling stability;
- Thick sections solidify more slowly and are prone to shrinkage porosity;
- Internal flow passage structures increase the difficulty of molten metal filling and venting.
Main Causes of Air Tightness Failure
During the die casting process, molten aluminum fills the mold cavity at high speed and solidifies rapidly. Internal defects mainly originate from the following factors:
1. Porosity Risk
Residual air in the mold cavity, gases generated by the release agent, and dissolved gases in the molten aluminum may become entrapped in the molten metal during filling.
If pores formed after solidification connect with the water passages or sealing areas, they can form leakage paths and affect the sealing performance of the water pump housing.
2. Shrinkage Porosity and Shrinkage Cavity Risk
The water pump housing contains local thick hot spot areas such as bearing mounting areas and flange bosses.
These areas cool more slowly during solidification. If feeding is insufficient, shrinkage porosity or shrinkage cavities can easily occur.
Internal shrinkage porosity not only reduces casting density but may also become a potential coolant leakage path.
3. Complex Internal Cavity Forming Risk
The water pump housing contains an impeller chamber, inlet and outlet flow passages, and partition structures.
The complex flow passages increase the molten metal flow path and may lead to the following problems during filling:
- Gas entrapment;
- Cold shuts;
- Local incomplete filling.
Therefore, the mold venting and gating system design need to be optimized to improve forming stability in complex areas.
Solution
To address the challenges of air tightness, internal density, and complex structure forming of the automotive water pump housing, this project adopted a combined process solution of:
Vacuum-Assisted Die Casting + Local Squeeze Feeding
to improve the internal quality and long-term reliability of the casting.
1. Vacuum-Assisted Die Casting
To address the risk of porosity formation during die casting, a vacuum venting system was installed in the mold cavity to reduce residual gas inside the cavity before and during injection.
The main optimization measures include:
- Installing vacuum vent blocks to improve cavity venting capability;
- Reducing gas entrapment during molten aluminum filling;
- Improving filling quality in complex flow passage areas;
- Improving the internal density of the casting.
Through vacuum-assisted die casting, the risk of porosity defects is reduced, improving the air tightness reliability of the water pump housing.
2. Local Squeeze Feeding Technology
For thick hot spot areas such as bearing seats and mounting bosses, squeeze pins were installed at corresponding positions in the mold.
During the solidification stage of the molten aluminum, localized secondary pressure was applied to compensate for solidification shrinkage and improve the density of critical areas.
The main measures include:
- Installing squeeze pins in hot spot areas;
- Applying directional feeding to thick sections;
- Improving feeding performance during solidification shrinkage;
- Reducing the risk of shrinkage porosity and shrinkage cavity defects.
This process effectively improves the internal quality of ADC12 aluminum alloy die castings and enhances the sealing reliability of the water pump housing.
3. Gating System Optimization
The gating system was optimized according to the internal flow passage structure of the water pump housing:
- Optimizing the molten metal flow path to reduce turbulence during filling;
- Ensuring sufficient feeding of thick-wall areas;
- Installing venting structures at the end of the filling path;
- Combining the gating system with the vacuum venting system to improve forming quality in complex areas.
Case Summary
Through the combined process of vacuum-assisted die casting and local squeeze feeding, this case successfully addressed the strict high air tightness requirements of the fuel vehicle air conditioning compressor front cover.
Through the combined process of vacuum-assisted die casting and local squeeze feeding, this project achieved stable manufacturing of the automotive water pump housing.
Project results:
- Reduced the risk of internal defects such as porosity and shrinkage porosity;
- Improved the density of ADC12 aluminum alloy castings;
- Met the sealing reliability requirements of the water pump housing;
- Achieved stable forming of complex internal cavity structures;
- Ensured product quality through X-ray inspection and other inspection methods.
