Plastic compound mold processing—also known as vacuum injection molding or soft mold casting—is a cost-effective manufacturing method for producing plastic parts using reusable silicone-based molds. Unlike traditional steel mold processes, it prioritizes speed, flexibilidade, and detail replication, making it ideal for small-batch production and product development. This article breaks down its core definitions, step-by-step workflow, material selections, vantagens, and limitations—with clear comparisons and real-world examples to help you optimize the process for your projects.
1. Definição central & Key Principles
Antes de mergulhar no processo, it’s critical to understand what makes plastic compound mold processing unique and how it differs from traditional methods.
| Aspecto | Plastic Compound Mold Processing | Traditional Steel Injection Molding |
| Material do molde | Primarily silicone rubber (flexível, elástico, and detail-retaining). | Rigid materials like aço ou alumínio (highly durable but costly to machine). |
| Princípio Fundamental | Replicates parts by pouring liquid plastic into a silicone mold (created from a prototype), then curing and demolding. | Injects molten plastic into a steel mold under high pressure (10–150 MPA) para produção em massa. |
| Batch Suitability | Ideal para pequenos lotes (10–500 unidades) e prototipagem. | Designed for mass production (10,000+ unidades) to offset high mold costs. |
| Principais vantagens | Low mold cost, Voltação rápida, and ability to replicate complex shapes/textures. | Alta eficiência de produção, superior part accuracy, and long mold life (100,000+ ciclos). |
Key Question: Why choose plastic compound mold processing?
For projects where speed and cost matter more than ultra-high volume—such as new product testing, niche market parts, or custom crafts—silicone-based molds eliminate the need for expensive steel tooling, cutting both time and upfront investment.
2. Step-by-Step Processing Workflow
Plastic compound mold processing follows a linear, repeatable workflow that starts with a prototype and ends with finished plastic parts. Each step directly impacts the final part’s quality and the mold’s durability.
2.1 Estágio 1: Prototype Preparation (The “Master Model”)
The prototype serves as the template for the silicone mold—its quality determines the detail and accuracy of all subsequent parts.
| Prototype Manufacturing Method | Principais características | Ideal para |
| 3D impressão (SLA/DLP) | – Alta precisão (± 0,05 mm) for intricate details (Por exemplo, Logos, texturas).- Acabamento superficial liso (RA 0,8-1,6μm) reduces post-processing.- Voltação rápida (12–24 hours for small parts). | Partes complexas: conchas de dispositivo eletrônico (Casos de telefone, TV remote casings), decorative items with fine patterns. |
| Usinagem CNC | – Ultra-high accuracy (± 0,01 mm) for tight tolerances.- Suitable for hard materials (metal, plástico rígido, madeira).- Ideal for flat or geometrically precise parts. | High-precision components: Suportes automotivos, Capas de dispositivos médicos, parts requiring strict dimensional consistency. |
| Hand Engraving/Crafting | – Low cost for simple shapes.- Flexible for one-of-a-kind designs.- No specialized equipment needed. | Simple decorative parts: custom keychains, small figurines, low-precision prototypes for visual testing. |
Dica crítica: Ensure the prototype is clean and defect-free (no dust, óleo, or scratches). Even tiny flaws will be replicated in the silicone mold—for example, a dusty prototype will create a mold with embedded particles, ruining the finish of plastic parts.
2.2 Estágio 2: Fazendo moldes de silicone (The “Negative Template”)
This stage transforms the prototype into a reusable mold. Proper silicone mixing, derramando, and curing are essential to avoid bubbles, lágrimas, or incomplete detail capture.
Etapa 1: Mold Frame Setup
- Frame Selection: Choose a frame material (madeira, plástico, ou metal) large enough to fit the prototype with 5–10mm of space on all sides (ensures even silicone coverage).
- Vedação: Use masking tape or acrylic sealant to seal frame edges—prevents silicone leakage, which wastes material and distorts the mold shape.
- Prototype Positioning: Secure the prototype in the frame with clay or double-sided tape—keep it centered to ensure uniform silicone thickness.
Etapa 2: Mistura de silicone
- Seleção de material: Use two-component silicone rubber (Parte a: base; Part B: agente de cura) with a mixing ratio specified by the manufacturer (tipicamente 1:1 by volume/weight for additive silicone, 10:1 for condensation silicone).
- Mixing Rules:
- Stir slowly and thoroughly (2–3 minutos) to avoid air bubbles—uneven mixing causes weak spots in the mold.
- Para lotes grandes, use um vacuum degassing machine (1–2 minutes at -0.1MPA) to remove trapped air—critical for parts with tiny details (Por exemplo, 0.5mm-wide slots).
Etapa 3: Silicone Pouring & Cura
- Técnica de derramamento: Tilt the frame at a 45° angle and pour silicone slowly along the frame wall (não diretamente no protótipo)—reduces bubble formation. For thick molds (>10mm), usar layered pouring: derramar 1/3 of the silicone, espere 30 minutes for bubbles to rise, then add the next layer.
- Curing Parameters:
| Tipo de silicone | Temperatura de cura | Tempo de cura (for 5mm Thickness) | Post-Curing Tip |
| Aditivo (Platinum-Cure) | 20°C–25°C | 2–4 horas | No post-curing needed; ready to demold once firm. |
| Condensation | 20°C–25°C | 4–8 horas | Cure for an extra 1 hour if mold is thicker than 10mm. |
| High-Temperature Resistant | 20°C–25°C (inicial); 80° c (post) | 6–10 horas (inicial); 2 horas (post) | Post-cure in an oven to activate heat resistance (até 200 ° C.). |
Etapa 4: Demolding the Prototype
- Uma vez curado, gently peel the silicone mold from the prototype—silicone’s elasticity ensures easy removal without damaging either the mold or prototype.
- Trim excess silicone (clarão) from mold edges with a sharp knife—creates a clean, precise mold for plastic casting.
2.3 Estágio 3: Plastic Part Production (The “Replica Process”)
Com o molde de silicone pronto, this stage produces finished plastic parts through pouring, cura, and demolding.
Etapa 1: Plastic Material Selection
Choose a material based on the part’s end-use (força, flexibilidade, Resistência ao calor):
| Material plástico | Propriedades -chave | Aplicações ideais |
| Poliuretano (Pu) Resina | – Cura rápida (1–2 hours at 20°C).- Good wear resistance and flexibility (Shore A 30–80).- Baixo custo ($20–40 per kg). | Partes funcionais: TV remote buttons, componentes de brinquedos, flexible gaskets, small electronic housings. |
| Resina epóxi | – Alta resistência (resistência à tracção: 50–80 MPa) and chemical resistance.- Resistente ao calor (120°C–180°C after curing).- Baixo encolhimento (0.5–1%). | Partes estruturais: Aparelho interior automotivo, alças de dispositivos médicos, parts requiring durability under stress. |
| Cloreto de polivinil (PVC) | – Low cost and good chemical stability.- Rigid or flexible variants available.- Suitable for food-contact parts (when food-grade). | Custom containers, Grupo decorativo, low-stress household items. |
Etapa 2: Derramando & Cura
- Derramando: Pour liquid plastic into the silicone mold slowly (use a small funnel for narrow openings) to avoid bubbles. For complex parts with internal cavities, usar sectional pouring: fill one section, espere 10 minutes for partial curing, then fill the next—ensures full cavity coverage.
- Cura:
- Cura à temperatura ambiente: PU Resina (1–2 horas), resina epóxi (4–6 horas).
- Cura acelerada: Use a low-temperature oven (50°C–60°C) to reduce time by 50% (Por exemplo, epoxy resin cures in 2–3 hours).
Etapa 3: Desmoldagem & Pós-processamento
- Gently peel the silicone mold from the plastic part—silicone’s flexibility prevents cracking or deformation.
- Trim excess plastic (clarão) with scissors or a utility knife. For better finish, sand the part with 400–800 grit sandpaper.
3. Advantages of Plastic Compound Mold Processing
This method solves key pain points for small-batch and prototyping projects:
| Categoria de vantagem | Principais benefícios | Exemplo do mundo real |
| Baixo custo | – Silicone mold cost is 50–70% lower than steel molds (Por exemplo, \(200 vs.. \)5,000 for a small part mold).- No expensive machining equipment needed for mold production. | A startup producing 50 test samples of a new smartwatch casing saves $4,800 by using a silicone mold instead of steel. |
| Voltação rápida | – Entire process (prototype → mold → parts) takes 3–7 days, vs.. 2–4 weeks for steel molds. | A consumer electronics company needs 20 TV remote prototypes for user testing—plastic compound processing delivers them in 4 dias, enabling faster design iterations. |
| Complex Detail Replication | – Captures tiny textures (0.1MM - 0,5mm), superfícies curvas, and internal structures that steel molds may struggle to replicate. | A jewelry brand replicates a hand-sculpted pendant with fine engravings—each plastic part retains the pendant’s intricate patterns, which would require costly steel mold machining. |
| Flexibilidade | – Easy to adjust mold design (Por exemplo, modify a prototype and make a new silicone mold in 1–2 days).- Switch plastic materials or colors without changing the mold. | A phone case manufacturer tests 3 cores (preto, branco, azul) using the same silicone mold—no need for multiple molds, cutting color-testing costs by 60%. |
4. Limitações a serem consideradas
While highly effective for specific use cases, plastic compound mold processing has constraints:
- Limited Mold Life: Silicone molds last 20–500 ciclos (vs.. 100,000+ for steel molds). Parts with sharp edges or high friction (Por exemplo, Clipes de plástico) wear down molds faster—after 50 ciclos, a mold may start to lose detail.
- Lower Part Accuracy: Dimensional accuracy is ±0.1mm–±0.3mm (vs.. ±0.01mm for steel injection molding). This is sufficient for most consumer parts but not for precision components like aerospace parts.
- Lower Production Efficiency: Each part requires manual pouring and demolding—production speed is 1–10 parts per hour (vs.. 100+ parts per hour for steel injection molding). For batches over 500 unidades, it becomes slower and more costly than traditional methods.
5. Yigu Technology’s Perspective on Plastic Compound Mold Processing
Na tecnologia Yigu, we see plastic compound mold processing as a “development enabler”—it lets clients test designs fast and avoid overinvesting in unproven products. A common mistake we address is clients overusing it for large batches: one client tried to produce 2,000 phone cases with a silicone mold, only to face mold wear and inconsistent parts after 300 ciclos. We advised switching to steel molds for mass production, salvando -os 40% nos custos de retrabalho. Para prototipagem, we recommend additive silicone (1:1 razão) for detail retention and PU resin for fast functional testing. Nosso principal insight: This process shines when paired with a clear transition plan—use it for 10–500 units, then scale to steel molds if demand grows.
6. Perguntas frequentes: Common Questions About Plastic Compound Mold Processing
1º trimestre: Can I use plastic compound mold processing for high-temperature parts (Por exemplo, parts exposed to 150°C)?
A1: Sim, but use heat-resistant materials. Escolher high-temperature silicone (service temp: 200° C - 300 ° C.) for the mold and heat-resistant epoxy resin (cured temp: 120°C–180°C) para a parte. Test a sample first—expose it to 150°C for 24 hours to ensure no deformation. Avoid standard silicone (Temp: 150° c) or PU resin (Temp: 80° c) for high-heat applications.
2º trimestre: How can I extend the life of my silicone mold?
A2: – Clean the mold with mild soap and water after each use (avoid harsh solvents like acetone, which break down silicone).- Apply a thin layer of silicone oil to the mold before pouring plastic—reduces friction and wear.- Armazene o molde em um legal, Lugar seco (umidade <60%) and avoid folding or stretching it—prevents tears.
3º trimestre: Are parts made via plastic compound mold processing suitable for food contact?
A3: Only if you use food-grade materials. Escolher food-safe silicone (certified by FDA or EU standards) for the mold and food-grade plastic resins (Por exemplo, food-grade PU, PVC, or epoxy). Regular materials may leach chemicals into food—always test the final part for compliance (Por exemplo, FDA 21 Cfr 177.2600 for resin) antes de usar.