Ce que vous devez savoir sur la technologie de moulage sous vide?

La technologie de moulage sous pression sous vide a changé la donne dans le secteur de la fabrication, corriger les défauts critiques du moulage sous pression traditionnel pour produire des produits de haute qualité, pièces à haute densité. Cet article plonge dans ses principes fondamentaux, processus, avantages, et des applications pratiques, vous offrant des informations exploitables pour exploiter efficacement cette technologie.

1. Concepts de base: Comment fonctionne le moulage sous vide?

À la base, vacuum die casting is an upgraded version of traditional pressure casting, enhanced by a vacuum environment. The key is to eliminate gas-related defects by controlling the air pressure in the mold cavity.

Core Principle

Traditional die casting often traps air and gas impurities in the molten metal, leading to porosity (petits trous) and looseness. Vacuum die casting solves this by extracting gas from the mold cavity synchronously during the casting process, creating a negative pressure environment. This inhibits the mixing of molten metal and gas, ultimately improving the casting’s density and mechanical properties.

Key Difference from Traditional Die Casting

To highlight its uniqueness, here’s a direct comparison:

2. Core Process Steps: A Linear Workflow

Vacuum die casting follows a structured, step-by-step process to ensure consistency and quality. Each stage is critical to achieving the desired results:

1. Préparation du moule

• Preheat the mold to the optimal temperature (varie selon le matériau, par ex., 150–250°C for aluminum alloys).
• Spray a high-quality release agent to prevent the molten metal from sticking to the mold.
• Ensure mold tightness—pay special attention to parting surfaces, curseurs, and other key areas to avoid air leakage.

2. Vacuum Stage

There are two common methods, each suited for different part designs:

• Pre-vacuum: After closing the mold, extract gas until the cavity reaches the set vacuum level (généralement <50 mbar) before injecting molten metal. Ideal for simple-structured parts.
• Dynamic Evacuation: Continuously extract gas alors que the molten metal fills the cavity. Parfait pour complex-structured castings (par ex., automotive engine blocks) where gas can get trapped in narrow channels.

3. Liquid Metal Filling & Pressurization

• Inject molten metal into the vacuum-sealed cavity at a controlled speed.
• Once filled, the injection punch applies high pressure (typically 50–150 MPa) to compact the metal, reducing shrinkage and enhancing density.

4. Refroidissement & Démoulage

• Cool the casting until it reaches the safe demolding temperature (varie selon le matériau).
• Remove the casting and perform optional post-processing: traitement thermique (par ex., T6 for aluminum) or machining to meet precise dimensions.

3. Avantages clés: Why Choose Vacuum Die Casting?

The technology’s popularity stems from its ability to solve long-standing manufacturing pain points. Below are its most impactful benefits, supported by specific data and use cases:

• Superior Casting Quality
• High density (>98% theoretical value) boosts mechanical properties (résistance à la traction, résistance à la fatigue) by 15–20% compared to traditional casting.
• Excellent surface finish: No need for porosity removal processes—parts can be directly electroplated, peint, or assembled.
• Strong Process Adaptability
• Idéal pour thin-walled parts (wall thickness ≤1 mm), such as lightweight automotive components.
• Handles complex structures: Produces parts like automobile transmission housings or aerospace brackets with intricate internal channels.
• Heat Treatment Friendly

Traditional castings often blister during heat treatment (due to trapped gas expanding). Vacuum die casting reduces this risk significantly, allowing castings to undergo processes like T6 heat treatment for enhanced hardness.

• Cost-Efficiency in the Long Run

While initial equipment costs are higher than traditional die casting, the lower scrap rate (reduced by 30–40%) and minimized post-processing costs create a clear comprehensive cost advantage—especially for high-volume production.

4. Critical Technical Points: Avoid Common Pitfalls

To maximize the benefits of vacuum die casting, focus on these four technical priorities:

1. Exhaust Duct Design

The exhaust duct has a “critical area”—a threshold for effective gas extraction. If the duct area is larger than the critical area, the vacuum effect is significant; if smaller, the effect is negligible. Par exemple, for aluminum castings, the critical area is typically 0.5–1.0 mm² per kg of molten metal.

2. Vacuum System Selection

The system must maintain the cavity’s vacuum level until filling is complete before closing the vacuum pump. Early valve closure leaves residual gas; delayed closure risks molten metal entering and blocking the valve.

3. Vacuum Valve Control

Vannes (mechanical or hydraulic solenoid) must match the process:

• Mechanical valves: Suitable for simple, low-speed processes (par ex., pre-vacuum for small parts).
• Hydraulic solenoid valves: Better for high-speed, dynamic evacuation (par ex., complex automotive parts), offering faster response times.

4. Mold Tightness

Even minor air leakage can ruin the vacuum effect. Regularly inspect and maintain:

• Parting surfaces (clean and align to prevent gaps).
• Slider seals (replace worn seals to avoid air ingress).

5. Typical Application Scenarios

Vacuum die casting excels in industries where part quality, densité, and reliability are non-negotiable. Here are its most common uses:

Yigu Technology’s Perspective

Chez Yigu Technologie, we see vacuum die casting as more than a process—it’s a solution to meet the growing demand for high-performance parts. Our clients in automotive and aerospace often require parts with <0.1% porosity and T6 heat treatment compatibility. To deliver this, we integrate custom exhaust duct designs (tailored to part geometry) and real-time vacuum monitoring systems, ensuring consistent cavity pressure (<30 mbar) during filling. We’ve also optimized mold maintenance protocols, cutting air leakage issues by 60%. Pour les fabricants, adopting vacuum die casting isn’t just an upgrade—it’s a way to stay competitive in markets where quality and efficiency define success.

FAQ

1. What is the maximum wall thickness for parts made with vacuum die casting?

While vacuum die casting excels at thin-walled parts (≤1 mm), it can also handle thicker parts (jusqu'à 10 mm). Cependant, thicker sections may require adjusted cooling times to avoid internal shrinkage.

2. Can vacuum die casting be used for all metals?

It works best with non-ferrous metals like aluminum, magnésium, and zinc alloys—these metals have lower melting points and flow easily in a vacuum. It is less common for ferrous metals (par ex., acier) due to their high melting points, which can damage vacuum system components.

3. How much does vacuum die casting equipment cost compared to traditional die casting?

Vacuum die casting equipment costs 30–50% more upfront. But with lower scrap rates (reduced by 30–40%) and less post-processing, most manufacturers recoup the investment within 1–2 years of high-volume production.