Quais são as principais diferenças entre fundição de precisão e fundição sob pressão, Como escolher?

Na conformação de metais, precision casting e fundição sob pressão are two core processes, cada um adaptado às necessidades de produção distintas. A fundição de precisão é excelente na criação de peças complexas, peças de alto desempenho em pequenos lotes, enquanto a fundição sob pressão domina a produção em massa de produtos leves, componentes de paredes finas. Para fabricantes, escolher o processo errado pode levar a custos desperdiçados, projetos atrasados, or subpar product quality. This article breaks down their principles, features, aplicações, and key differences—providing actionable guidance to help you select the right method for your project.

1. Precision Casting: Definição, Processo, and Core Advantages

Precision casting (also called “near-net shaping casting”) is a family of processes designed to produce parts with tight dimensional tolerances and smooth surfaces, minimizing the need for post-processing. Its most common form is investment casting (lost wax casting), which supports a wide range of metals and complex structures.

1.1 Key Process Stages (Taking Investment Casting as Example)

The precision casting process follows a linear, step-by-step workflow that ensures high accuracy. Below is a detailed breakdown using a time-axis structure:

1. Wax Mold Preparation: Melt fusible wax (por exemplo, paraffin) and inject it into a metal die to form a wax pattern identical to the final part. For complex parts (por exemplo, aerospace blades), multiple wax patterns are assembled into a single “tree.”
2. Shell Building: Dip the wax pattern repeatedly into a refractory material (por exemplo, silica sol) and sprinkle with fine sand (por exemplo, zircon sand). Each layer dries to form a solid, heat-resistant shell (tipicamente 5-10 layers thick, depending on part size).
3. Wax Removal: Place the shell in a steam autoclave (120-150°C) to melt and drain the wax, leaving a hollow cavity that matches the part’s shape. This step gives investment casting its “lost wax” name.
4. Shell Roasting & Metal Pouring: Roast the shell at 800-1000°C to remove residual wax and strengthen the structure. Then, pour molten metal (por exemplo, aço inoxidável, titanium alloy) into the hot shell—gravity or low pressure helps fill complex cavities.
5. Shell Breaking & Pós-processamento: After cooling (1-4 horas, depending on metal type), break the shell with a hammer or vibrating machine. Trim excess material (por exemplo, 浇口，risers) and perform surface treatments (por exemplo, grinding, polishing) to meet final specifications.

1.2 Features and Advantages

Precision casting’s unique workflow delivers three key benefits for high-end applications:

• Exceptional Precision & Surface Quality: Dimensional tolerance reaches ±0.1mm for parts up to 300mm, and surface roughness (Rá) is as low as 1.6-3.2 μm—no extensive machining is needed for most applications.
• Broad Material Compatibility: Unlike die casting (limited to low-melting-point alloys), precision casting works with high-melting-point metals like aço inoxidável, titanium alloy, e carbon steel—critical for aerospace and medical industries.
• Complex Structure Capability: It can produce parts with internal cavities, thin walls (down to 0.5mm), and intricate details (por exemplo, turbine blade airfoils) that are impossible with traditional casting or machining.

1.3 Typical Application Scenarios

Precision casting shines in industries where performance and complexity take priority over production speed:

• Aeroespacial: Engine blades, turbine disks, and fuel nozzles (require high-temperature resistance and complex airflow channels).
• Medical Devices: Instrumentos cirúrgicos (por exemplo, stainless steel forceps) and implant components (por exemplo, titanium hip joints—demand biocompatibility and precision).
• Oil & Gas: Pump impellers, valve cores, and wellhead components (need corrosion resistance and tight sealing).

2. Fundição sob pressão: Definição, Processo, and Core Advantages

Die casting is a high-pressure, high-speed process that injects molten non-ferrous alloys into a precision metal mold (die) to produce parts in large volumes. It is the go-to choice for lightweight, cost-effective components in consumer electronics and automotive industries.

2.1 Key Process Stages

Die casting follows a fast, repeatable workflow optimized for mass production. Here’s a step-by-step breakdown with critical parameters:

1. Mold Preparation: Heat the metal die (typically H13 steel) to 180-250°C (for aluminum alloys) and apply a release agent to prevent sticking. The die consists of two halves (fixed and movable) that clamp together to form a cavity.
2. Metal Melting: Melt low-melting-point alloys (por exemplo, aluminum alloy ADC12, zinc alloy ZAMAK 5) in a furnace at 600-700°C (for aluminum) until it becomes a homogeneous liquid.
3. High-Pressure Injection: Use a hydraulic punch to inject the molten metal into the die cavity at high speed (3-8 m/s) and pressure (30-150 MPa). This ensures the metal fills every detail of the mold.
4. Pressure Cooling & Ejection: Maintain pressure (holding time: 2-5 seconds) as the metal solidifies to prevent shrinkage. Once solid, the die opens, and ejector pins push the casting out.
5. Pós-processamento: Trim excess material (por exemplo, runners, flash) with a trim press. For critical parts, perform additional steps like drilling or surface coating (por exemplo, anodizing for aluminum).

2.2 Features and Advantages

Die casting’s strength lies in its efficiency and cost-effectiveness for large-scale production:

• Extreme Production Speed: A single die casting machine can produce 50-200 parts per hour (depending on part size)—ideal for mass markets like automotive and 3C electronics.
• Low Per-Part Cost: While mold costs are high (tipicamente \(50,000-\)500,000), the cost per part drops significantly in large batches (por exemplo, \(0.5-\)5 per aluminum phone shell for 1 million units).
• Lightweight & Thin-Walled Capability: It can produce parts with thin walls (down to 0.8mm) and complex geometries (por exemplo, laptop chassis with integrated ribs)—reducing weight by 20-30% compared to plastic or steel parts.

2.3 Typical Application Scenarios

Die casting dominates industries where volume, custo, and lightweighting are key:

• Automotivo: Engine blocks, transmission housings, and EV battery frames (aluminum die casting reduces vehicle weight to improve fuel efficiency).
• 3C Electronics: Smartphone middle frames, laptop palm rests, and tablet casings (zinc or aluminum alloys balance durability and slim design).
• Home Appliances: Air conditioner compressor shells, washing machine motor brackets, and TV stand bases (require cost-effectiveness and consistent quality).

3. Precision Casting vs. Fundição sob pressão: A Comprehensive Comparison

To help you quickly identify the right process, the table below compares 7 key dimensions—from material compatibility to cost structure. Esse side-by-side comparison highlights critical trade-offs:

4. How to Choose Between Precision Casting and Die Casting?

The right process depends on your project’s priorities. Use this decision framework (based on 4 key factors) to avoid costly mistakes:

4.1 Factor 1: Production Volume

• Choose Precision Casting if: You need <10,000 parts/year (por exemplo, custom medical instruments). High mold costs for die casting will outweigh any per-part savings.
• Choose Die Casting if: You need >50,000 parts/year (por exemplo, componentes automotivos). The high initial mold investment will be offset by low per-part costs.

4.2 Factor 2: Material Requirements

• Choose Precision Casting if: You need high-melting-point or corrosion-resistant metals (por exemplo, titanium for aerospace parts, stainless steel for medical devices).
• Choose Die Casting if: You can use aluminum, zinco, or magnesium alloys (por exemplo, aluminum for EV parts, zinc for electronics).

4.3 Factor 3: Part Complexity & Desempenho

• Choose Precision Casting if: The part has internal cavities, thin walls (<1milímetros), or requires high-temperature/mechanical performance (por exemplo, turbine blades).
• Choose Die Casting if: The part is a solid or simple hollow structure (por exemplo, phone shell) and prioritizes lightweighting over extreme performance.

4.4 Factor 4: Custo & Lead Time

• Choose Precision Casting if: Lead time is flexible (2-4 weeks) and per-part cost is less critical than quality (por exemplo, custom oil valve cores).
• Choose Die Casting if: You need fast lead times (1-2 days for mass production) and low per-part costs (por exemplo, invólucros de eletrônicos de consumo).

5. Yigu Technology’s Perspective on Precision Casting vs. Fundição sob pressão

Na tecnologia Yigu, we believe the choice between precision casting and die casting is not about “which is better”—but “which fits your needs.” Many manufacturers mistakenly prioritize cost over performance (por exemplo, using die casting for high-temperature parts) or overengineer (por exemplo, using precision casting for low-volume consumer parts), leading to waste.

For clients in aerospace or medical fields, we recommend precision casting with advanced shell materials (por exemplo, ceramic-based refractories) to enhance part durability. For automotive or 3C clients, we advocate for fundição de alumínio paired with vacuum technology to reduce porosity—balancing cost and quality.

Looking ahead, the two processes will converge: We’re already seeing “precision die casting” (combining die casting’s speed with precision casting’s accuracy) for EV battery frames. By aligning process selection with material, volume, and performance goals, manufacturers can maximize efficiency and product value.

6. Perguntas frequentes: Common Questions About Precision Casting and Die Casting

Q1: Can die casting produce parts with internal cavities like precision casting?

Sim, but it requires removable metal cores (placed in the die before injection), which add cost and complexity. For simple cavities (por exemplo, a single hole), cores are feasible; for complex internal channels (por exemplo, turbine blade airfoils), precision casting is more practical and cost-effective.

Q2: Is precision casting suitable for low-cost consumer products?

Rarely. Precision casting has high per-part costs (due to wax patterns and shell building), making it too expensive for low-margin consumer goods (por exemplo, toys, basic hardware). Die casting or plastic injection molding is better for these applications.

Q3: Can die casting parts be used in high-temperature environments (por exemplo, engine hot ends)?

Most die casting alloys (por exemplo, aluminum ADC12) have a maximum service temperature of 150-200°C—too low for engine hot ends (exceed 300°C). For high-temperature applications, choose precision casting with heat-resistant alloys (por exemplo, Inconel superalloy) instead.