Casting a vuoto in silicone is a high-precision manufacturing process used to replicate complex parts—from electronic device shells to art prototypes—by eliminating air bubbles via vacuum pressure. The success of this process depends entirely on selecting the right materials, which include silicone molds, base prototypes, auxiliary agents, and casting resins. This article breaks down each material category with clear comparisons, technical specs, e applicazioni del mondo reale, helping you optimize vacuum casting for accuracy, durata, ed efficacia in termini di costi.
1. Core Silicone Mold Materials: The Foundation of Casting
Silicone is the heart of vacuum casting molds—its flexibility and detail-retaining ability ensure replicas match the original prototype. Materials are categorized by curing mechanism and performance, each suited to specific needs.
| Tipo di silicone | Caratteristiche chiave | Curing Parameters | Applicazioni ideali |
| Condensation Silicone | – Releases small molecules (ethanol/acetic acid) during curing.- Basso costo (30–50% cheaper than additive silicone).- Moderate shrinkage (2–3%), which may blur fine details.- Shore una durezza: 20–40 (morbido, Facile Demolding). | – Mixing ratio: 100:2–5 (silicone:agente curativo).- Tempo di cura: 4–8 ore (20°C–25°C).- No vacuum needed for mixing (but vacuum casting still requires bubble removal). | Simple parts with low precision demands: handicrafts, prototipi giocattoli, and non-critical decorative items (PER ESEMPIO., plastic plant pots). |
| Additivo (Platinum-Cure) Silicone | – No small molecule release during curing.- Ultra-low shrinkage (0.1–0,5%)—critical for high-precision parts.- High durability (reusable 40–60 cycles, contro. 20–30 for condensation).- Shore una durezza: 30–60 (versatile for soft/hard parts). | – Mixing ratio: 1:1 (by volume/weight—easy to measure).- Tempo di cura: 2–4 ore (20°C–25°C; 1 hour at 50°C–60°C).- Requires vacuum defoaming (1–2 minutes at -0.1MPA) to avoid internal bubbles. | Componenti di alta precisione: gusci di dispositivi elettronici (Involucri per telecomandi TV), parti del dispositivo medico (ugelli per siringhe), e finiture interne automobilistiche (pulsanti dashboard). |
| Silicone resistente alle alte temperature | – Resiste al calore post-fusione (200° C - 300 ° C.) per resine termoindurenti.- Mantiene la flessibilità e la forma a temperature estreme.- Basso restringimento (0.3–0,8%) ed elevata resistenza allo strappo. | – Mixing ratio: 100:5 (silicone:agente curativo).- Tempo di cura: 6–10 ore (20°C–25°C; 2–3 ore a 80°C).- Deve essere polimerizzato in un forno a temperatura controllata per attivare la resistenza al calore. | Scenari di fusione ad alto calore: repliche in lega metallica (leghe di stagno-piombo a basso punto di fusione), parti in resina termoindurente (resina epossidica polimerizzata a 120°C), e prototipi di componenti aerospaziali. |
| Silicone trasparente | – High light transmittance (85–95% after curing)—lets you monitor casting material flow.- Available in both condensation and additive types (additive preferred for precision).- Similar mechanical properties to non-transparent counterparts. | – Same curing parameters as matching non-transparent silicone (PER ESEMPIO., 1:1 ratio for additive transparent).- Requires extra care to avoid dust (which reduces transparency). | Componenti ottici: light diffusers, transparent device housings (PER ESEMPIO., LED lamp covers), and prototypes where internal casting defects need visual inspection. |
2. Base Prototype Materials: The “Original Model”
The prototype (or master model) defines the shape of the final replica. It must be durable enough to withstand silicone pouring and compatible with silicone (no chemical reactions).
| Materiale prototipo | Tratti chiave | Compatibility with Silicone | Ideale per |
| 3D-Printed Resins (SLA/DLP) | – Alta precisione (± 0,05 mm) for complex details.- Superficie liscia (RA 0,8–1,6 μm) reduces sanding time.- Available in rigid or flexible variants. | Eccellente (no reaction with silicone). Use a light release agent (olio di silicone) for easy demolding. | Rapid prototyping of intricate parts: jewelry patterns, electronic connector prototypes, and TV interface panels. |
| CNC-Machined Metals (Alluminio/ottone) | – Ultra durevole (reusable for 100+ mold makings).- Elevata finitura superficiale (Ra 0,4–0,8μm) per repliche a specchio.- Resistente al calore (adatto per silicone ad alta temperatura). | Bene. Utilizzare vaselina o spray specifico per il distacco dei metalli per evitare che il silicone si attacchi. | Maestri di livello industriale: prototipi di parti automobilistiche (Alloggiamenti degli ingranaggi), inserti per stampi per uso ripetuto, e componenti ad alta usura. |
| Resine/Cera lavorate a CNC | – Costo inferiore rispetto al metallo.- Facile da macchina (tempi di consegna più rapidi rispetto al metallo).- La cera è ideale per la fusione a bassa temperatura (si scioglie se necessario). | Molto bene. La cera richiede vaselina (l'alcol scioglie la cera); la resina utilizza agenti distaccanti standard. | Prototipi d'arte: sculptural replicas, custom candle molds, and low-volume decorative parts (PER ESEMPIO., ceramic vase masters). |
| Existing Finished Parts | – No need to design a new prototype (Salva tempo).- Must be clean and undamaged (scratches transfer to the mold). | Depends on the part material: plastic/metal works; rubber may react with condensation silicone. | Reverse-engineering projects: copying legacy parts (old TV knobs), replacement components for out-of-production equipment, and competitor product analysis. |
3. Auxiliary Materials: Ensure Process Smoothness & Mold Performance
These materials enhance mold durability, prevent defects, and optimize casting results—they’re often overlooked but critical for success.
| Auxiliary Material | Scopo | Usage Tips |
| Agenti di rilascio di muffe | Create a barrier between silicone and the prototype/replica to avoid sticking. | – Petroleum Jelly: For wax prototypes (basso costo, facile da applicare).- Silicone Oil (100–500 cSt): For plastic/metal prototypes (no residue, won’t blur details).- Specialized Spray: For silicone-on-silicone casting (prevents chemical bonding).- Applicare un sottile, even layer—thick coats distort details. |
| Materiali di rinforzo | Boost mold strength and wear resistance (prevents tearing during demolding). | – Fiberglass Cloth: Lay 1–2 layers over the silicone surface (after pouring, before curing) for large molds (PER ESEMPIO., TV back cover molds).- Silicone Fillers (Silica Powder): Mix 5–10% into silicone to increase hardness (Shore A +5–10) per parti di abbigliamento ad alte. |
| Curing Agents/Catalysts | Control silicone curing speed and final properties. | – Condensation Catalysts: Use 2–5% (more = faster cure, but may reduce flexibility).- Platinum Catalysts: 1:1 rapporto (fixed—cannot adjust cure speed without changing temperature).- Store in cool, dry places (heat deactivates platinum catalysts). |
| Sealants/Tapes | Prevent silicone leakage from the mold frame during pouring. | – Acrylic Sealant: For permanent frame seals (wood/metal frames).- Masking Tape: For temporary seals (plastic frames, easy to remove).- Apply 2–3 layers along frame edges to fill gaps. |
4. Materiali di fusione: The “Replica” Materials
After the silicone mold is made, these materials are poured (sotto vuoto) to create the final part. They’re chosen based on strength, flessibilità, and end-use.
| Casting Material | Proprietà chiave | Vacuum Casting Parameters | Applicazioni |
| Poliuretano (Pu) Resina | – Currezione rapida (1–2 hours at 20°C–25°C; 30 minuti a 60 ° C.).- Basso costo ($20–40 per kg).- Versatile: rigido (Shore D 60–80) o flessibile (Shore A 30–50).- Buona resistenza all'impatto (10–15 kJ/m²). | – Pressione del vuoto: -0.095 A -0.1MPA (Rimuove le bolle).- Pouring temperature: 25°C–30°C (too hot = flash curing). | Small-batch functional parts: TV remote buttons, phone case replicas, and toy components. |
| Resina epossidica | – Alta resistenza (resistenza alla trazione: 50–80 MPa, contro. PU’s 30–50 MPa).- Resistente al calore (120°C–180°C after curing).- Basso restringimento (0.5–1%)—good for structural parts. | – Pressione del vuoto: -0.1MPA (hold for 2–3 minutes to remove deep bubbles).- Tempo di cura: 4–6 ore (20°C–25°C; 1–2 hours at 80°C). | Componenti strutturali: staffe automobilistiche, alloggiamenti per dispositivi elettronici (laptop bases), and medical tool handles. |
| Low-Melting Alloys (Tin-Lead/Bismuth) | – Punto di fusione: 183°C–250°C (compatible with high-temperature silicone).- Metallic finish (Nessun dipinto necessario).- Alta densità (feels like real metal). | – Pressione del vuoto: -0.1MPA (critical—metal bubbles cause cracks).- Pouring temperature: 20°C–30°C above melting point (avoids premature solidification). | Metal replicas: hardware decorativo (maniglie delle porte), scale model parts (miniature car bodies), and jewelry (metal pendants). |
| Gypsum/Plaster | – Costo ultra-basso ($5–10 per kg).- Easy to color (mix pigments before pouring).- Fragile (low impact resistance—not for functional parts). | – Pressione del vuoto: -0.08 A -0.09MPA (too high = sucks out fine particles).- Tempo di cura: 24–48 ore (air-dry; no oven needed). | Art/teaching models: sculptural replicas, modelli anatomici (skull casts), and classroom demonstrations. |
5. Yigu Technology’s Perspective on Silicone Vacuum Casting Materials
Alla tecnologia Yigu, we’ve found that material mismatches cause 70% of vacuum casting failures—e.g., using condensation silicone for high-precision TV prototypes or low-temperature silicone for metal casting. Our key advice is: prioritize silicone type based on precision and end-use. For clients making electronic device shells (PER ESEMPIO., smartwatch casings), we always recommend additive silicone—it eliminates shrinkage-related defects, risparmio 30% nei costi di rielaborazione. For budget-sensitive projects (PER ESEMPIO., craft replicas), condensation silicone works but requires extra sanding to fix detail blurring. We also emphasize testing material compatibility: a client once used a rubber prototype with condensation silicone, causing the rubber to degrade—switching to a 3D-printed resin prototype solved the issue. Finalmente, don’t skip reinforcement for large molds: fiberglass-clad silicone molds last 2x longer than unreinforced ones, critical for small-batch production (50+ repliche).
6. Domande frequenti: Common Questions About Silicone Vacuum Casting Materials
Q1: Can I use condensation silicone for high-precision parts (PER ESEMPIO., electronic connectors with 0.1mm slots)?
A1: No—condensation silicone’s 2–3% shrinkage will close 0.1mm slots or blur fine details. Use additive silicone instead (0.1–0.5% shrinkage) to retain precision. Per esempio, a 0.1mm slot cast with additive silicone will remain 0.095–0.1mm, while condensation silicone will reduce it to 0.07–0.08mm (too small for connectors).
Q2: What casting material should I use for a functional TV remote prototype that needs to withstand drops?
A2: Use rigid polyurethane (Pu) resina (Sponda D 70–80) or epoxy resin. PU resin offers better impact resistance (15 kJ/m² vs. epoxy’s 10 KJ /), making it ideal for drop-prone parts. Test by dropping the replica from 1m onto a hard surface—PU resin should not crack, while gypsum/plaster will shatter immediately.
Q3: Why does my high-temperature silicone mold still deform when casting low-melting alloy?
A3: This usually stems from two issues: (1) The silicone wasn’t fully cured (insufficient oven time at 80°C—re-cure for 2 ore extra). (2) The alloy pouring temperature is too high (exceeding the silicone’s service limit—keep it 20°C–30°C above the alloy’s melting point, not higher). Per esempio, a 200°C silicone mold will deform if poured with 300°C alloy—lower the temperature to 270°C (for a 250°C melting point alloy).