Can injection-molded pre-embedded plastic cast aluminum parts achieve airtight functional integration?
Publish Time: 2025-10-08
As a typical metal-plastic composite structure, injection-molded pre-embedded plastic cast aluminum parts are widely used due to their advantages such as lightweight, high rigidity, excellent electromagnetic shielding, and wide design freedom.1. The Basis for Airtightness: The Quality of the Plastic-Cast Aluminum InterfaceThe core of airtightness lies in preventing gas or liquid from penetrating through the interface between the plastic and the cast aluminum. Ideally, the molten plastic should fully envelop the cast aluminum insert during the injection molding process and form a dense, seamless interface upon cooling. This requires good wettability and a micro-anchoring structure on the cast aluminum surface. Typically, cast aluminum parts undergo sandblasting, chemical etching, or laser micro-texturing to remove the oxide film and create micron-level roughness, thereby enhancing the plastic's mechanical adhesion. Furthermore, selecting an engineering plastic with a thermal expansion coefficient close to that of the cast aluminum can effectively reduce interfacial microgaps caused by temperature fluctuations and prevent "thermal fatigue leakage."2. Precision Injection Molding Ensures Sealing IntegrityThe title emphasizes "advanced technology, uniform, scratch-free, smooth surface, no bumps or bumps, no unusual edges or corners, no deformation, and no deformation after pre-molding." These are the prerequisites for achieving airtightness. During the injection molding process, melt temperature, injection speed, holding pressure, and cooling time must be strictly controlled. Too low a melt temperature will result in insufficient plastic fluidity, preventing it from completely filling the tiny grooves of the cast aluminum insert; while too high an injection speed may cause jetting or air entrapment, resulting in internal porosity. Multi-stage injection and vacuum-assisted injection molding techniques can effectively remove interfacial air, reducing bubbles and shrinkage.3. Structural Design Enhances Sealing FunctionRelying solely on materials and processes will not ensure long-term reliability under high airtightness requirements. Therefore, structural design is crucial. Common strategies include:Introducing sealing ribs or labyrinthine structures: Designing annular bosses or stepped nesting within the plastic sheath area to extend the leakage path;Introducing secondary sealing grooves: Reserving mounting locations for O-rings or silicone gaskets to provide dual "primary and secondary" sealing;Avoiding direct paths: Ensure that the interface between the plastic and cast aluminum does not directly communicate with the internal and external cavities. Where necessary, employ full sheathing or partial sealing designs.4. Verification and Reliability AssuranceEven with a perfect design and process, rigorous airtightness testing is still required. Common methods include pressure decay testing, helium mass spectrometry leak detection, or water immersion bubble testing. For key components such as automotive electronic control housings and battery cooling connectors, high-temperature cycling, vibration aging, and chemical resistance testing are also required to assess sealing stability during long-term service.In summary, injection-molded pre-embedded plastic cast aluminum parts are technically feasible for achieving airtightness functional integration. Their success relies on the coordinated optimization of the four key elements: materials, process, structure, and verification. Supported by advanced injection molding and embedded processing technologies, as long as the interface is defect-free, the structure has no through-holes, and the process has no fluctuations, such composite parts can not only meet the requirements of "smooth surface and no deformation" in appearance, but also meet the stringent sealing function requirements, becoming an ideal solution for high-end equipment that integrates structure and function.
