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, high-density parts. This article dives into its core principles, processus, avantages, and practical applications—equipping you with actionable insights to leverage this technology effectively.

1. Concepts de base: How Does Vacuum Die Casting Work?

À la base, vacuum die casting is an upgraded version of traditional pressure casting, enhanced by a vacuum environment. La clé est d'éliminer les défauts liés aux gaz en contrôlant la pression de l'air dans la cavité du moule..

Principe de base

Le moulage sous pression traditionnel emprisonne souvent les impuretés de l'air et du gaz dans le métal en fusion., conduisant à la porosité (minuscules trous) et le relâchement. Le moulage sous vide résout ce problème en extraire le gaz de la cavité du moule de manière synchrone pendant le processus de coulée, créer un environnement de pression négative. Cela inhibe le mélange du métal fondu et du gaz, améliorant finalement la densité et les propriétés mécaniques de la pièce moulée.

Key Difference from Traditional Die Casting

Pour souligner sa singularité, 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 des moisissures

• Preheat the mold to the optimal temperature (varie selon le matériau, Par exemple, 150–250°C for aluminum alloys).
• Spray a high-quality release agent to prevent the molten metal from sticking to the mold.
• Assurer 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 exemple, blocs de moteur automobile) where gas can get trapped in narrow channels.

3. Liquid Metal Filling & Pressurisation

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

4. Refroidissement & Démêlé

• 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 exemple, 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. Voici ses avantages les plus importants, supported by specific data and use cases:

• Superior Casting Quality
• Densité élevée (>98% theoretical value) boosts mechanical properties (résistance à la traction, résistance à la fatigue) by 15–20% compared to traditional casting.
• Excellente finition de surface: 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: Évitez les pièges courants

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 exemple, pre-vacuum for small parts).
• Hydraulic solenoid valves: Better for high-speed, dynamic evacuation (Par exemple, 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. Scénarios d'application typiques

Vacuum die casting excels in industries where part quality, densité, et la fiabilité ne sont pas négociables. Voici ses utilisations les plus courantes:

Perspective de la technologie Yigu

À la technologie Yigu, 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 exemple, acier) due to their high melting points, which can damage vacuum system components.

3. Combien coûte l’équipement de coulée sous vide par rapport au moulage sous pression traditionnel?

L’équipement de coulée sous vide coûte 30 à 50 % de plus au départ. Mais avec des taux de rebut inférieurs (reduced by 30–40%) et moins de post-traitement, la plupart des fabricants récupèrent l'investissement dans un délai d'un à deux ans après une production en grand volume.