En el plastic prototype manufacturing industria, CLORURO DE POLIVINILO (Cloruro de polivinilo) blow molding prototype products are widely used in construction, médico, daily chemical and other fields due to their excellent chemical resistance, flame retardancy and cost-effectiveness. Sin embargo, processing PVC blow molding prototypes is more complex than other plastic materials—PVC is prone to degradation at high temperatures, and its flexibility and stability rely heavily on formula matching. Many manufacturers struggle with issues like prototype brittleness, grosor de la pared desigual, or surface defects during production. This article breaks down the entire processing process of PVC blow molding prototype products, focusing on solving practical problems and helping you achieve efficient and high-quality prototype manufacturing.
1. Selección de material: Lay the Foundation for Stable PVC Prototypes
Selección de material is the first and most critical step in PVC blow molding prototype processing. Unlike PE, pure PVC resin is hard and brittle, so it requires precise matching of additives to meet the performance requirements of prototypes. The right material formula not only ensures the prototype’s functionality but also avoids problems like degradation during molding.
1.1 Core Components of PVC Blow Molding Materials & Their Roles
| Componente | Key Types | Función | Impacto en el prototipo |
| PVC Resin | Suspension PVC (SG-3 to SG-8), Emulsion PVC | Provides the basic structure and mechanical properties of the prototype | SG-3 (low K-value) has good melt fluidity, suitable for thin-walled prototypes; SG-7/SG-8 (high K-value) has high strength, ideal for load-bearing prototypes like pipe fittings |
| Plasticizers | Dioctyl phthalate (DOP), Diisononyl phthalate (DINP) | Improves PVC flexibility and processability | Con la atención 20-40% plasticizer makes the prototype flexible (P.EJ., medical hoses); con la atención <10% keeps it rigid (P.EJ., plastic containers) |
| Stabilizers | Calcium-zinc stabilizers (environmentally friendly), Lead-based stabilizers (alta eficiencia) | Prevents PVC degradation at high temperatures (avoids discoloration, fragilidad) | Calcium-zinc stabilizers are mandatory for food/medical prototypes; lead-based stabilizers are suitable for industrial prototypes (but restricted in eco-sensitive areas) |
| Relleno | Calcium carbonate, Talc powder | Reduces costs and improves dimensional stability | Con la atención 5-15% fine calcium carbonate enhances prototype rigidity; excessive fillers (>20%) cause poor melt fluidity and rough surfaces |
| Colorants | Organic pigments (bright colors), Inorganic pigments (estable) | Meets the appearance requirements of prototypes | Organic pigments (P.EJ., phthalocyanine blue) are suitable for decorative prototypes; inorganic pigments (P.EJ., titanium dioxide) are ideal for white opaque prototypes (better weather resistance) |
A common question here is: Why do PVC prototypes often become brittle after molding? The main reason is improper material matching—either insufficient plasticizers (menos que 15% for flexible prototypes) or low-quality stabilizers that fail to prevent PVC degradation during high-temperature processing. It is recommended to conduct small-batch formula tests before mass prototype production: mix materials in different ratios, test their tensile strength and elongation at break, and select the optimal formula.
2. Configuración de la máquina: Ensure Precision in Prototype Shaping
Machine setup directly determines the accuracy and consistency of PVC blow molding prototypes. Unlike PE blow molding, PVC has stricter requirements for temperature and pressure control—too high a temperature causes degradation, while too low a temperature leads to poor melt fluidity. Every parameter in machine setup needs to be calibrated precisely.
2.1 Key Parameters for PVC Blow Molding Machine Setup & Calibración
| Setup Item | Core Parameters | Recommended Range for Prototypes | Calibration Method |
| Blow Molding Machine | Screw diameter (30-65milímetros), Shot volume (50-500ml) | Choose a small screw (30-45milímetros) for small prototypes (P.EJ., 50ml bottles); 50-65mm for large prototypes (P.EJ., 300ml containers) | Test-run with empty material to check if the screw rotates smoothly and the extruder has no material leakage |
| Parison Control | Parison thickness uniformity, Die gap (1-3milímetros) | Thickness variation ≤5% (critical for avoiding prototype wall unevenness) | Use a laser thickness gauge to measure the parison at 5 points; adjust the die lip bolts to correct uneven areas |
| Diseño de moldes | Cavity surface finish (Ra 0.8-1.6μm), ángulo de tiro (1-3°) | Polished cavity for smooth prototype surfaces; draft angle ≥2° for easy ejection (PVC has high friction) | Apply mold release agent (basado en silicona) before first use; check for mold scratches that may cause prototype surface defects |
| Temperature Settings | Barrel temperature (160-190℃), Die temperature (170-185℃) | Zona 1 (alimentar): 160-170℃; Zona 3 (derretir): 180-190℃ (avoid exceeding 195℃ to prevent degradation) | Use a thermocouple to measure actual temperature at each barrel zone; adjust the heater if the difference between set and actual temperature >5℃ |
| Pressure Settings | Extrusion pressure (15-25MPA), Blow pressure (0.4-0.8MPA) | Extrusion pressure: 18-22MPA (stable parison extrusion); Blow pressure: 0.5-0.6MPa for thin-walled prototypes, 0.7-0.8MPa for thick-walled ones | Install a pressure gauge at the extruder outlet; adjust the screw speed to maintain stable pressure (variation ≤2MPa) |
2.2 Common Machine Setup Mistakes & Soluciones
- Error 1: Die temperature too high (＞190℃) → Prototype surface turns yellow (PVC degradation).
Solución: Reduce die temperature by 5-10℃; agregar 1-2% extra stabilizer to the material.
- Error 2: Blow pressure too low (＜0.4MPa) → Prototype fails to fully expand to the mold cavity (shape distortion).
Solución: Increase blow pressure by 0.1MPa; check if the air inlet is blocked (clean with compressed air if needed).
3. Blowing Process: The Core of PVC Prototype Formation
El blowing process is a continuous and dynamic process that converts PVC melt into prototype products through parison extrusion, inflation and cooling. Each step must be timed and controlled precisely—PVC’s short processing window (melt to solidification in 10-20 artículos de segunda clase) leaves little room for error.
3.1 Step-by-Step PVC Blowing Process & Key Control Points
- Parison Extrusion
The extruder melts the PVC material (mixed resin + aditivos) and extrudes it into a tube-shaped parison. The key is to ensure the parison has uniform thickness and stable extrusion speed. Por ejemplo, when making a 100ml PVC bottle prototype, set the extrusion speed to 15-20mm/s; use a parison controller to adjust the die gap in real time (P.EJ., reduce the gap by 0.2mm if the parison is too thick on one side).
- Sujeción de moho
The mold closes quickly (dentro 1-2 artículos de segunda clase) to clamp the parison. The clamping force should be 10-15kN for small prototypes (P.EJ., 50ml vials) and 20-30kN for large ones (P.EJ., 500ml jars). Too much force crushes the parison; too little causes air leakage during inflation.
- Air Injection & Inflation
Inject compressed air into the parison at a speed of 0.3-0.5m³/min. The air pressure (0.4-0.8MPA) depends on the prototype’s wall thickness: thin-walled (＜1mm) prototypes need lower pressure (0.4-0.5MPA) to avoid bursting; thick-walled (＞2mm) ones need higher pressure (0.6-0.8MPA) to ensure full expansion. The inflation time is 3-5 seconds—long enough for the parison to adhere to the mold cavity.
- Enfriamiento
Cool the prototype with water cooling (más eficiente) or air cooling. For PVC, the cooling time is 5-10 artículos de segunda clase (longer than PE, as PVC has lower thermal conductivity). The mold temperature should be maintained at 20-30℃: use a water circulation system to cool the mold; if the prototype has thick walls (＞3mm), extend cooling time by 2-3 seconds to prevent deformation after ejection.
- Expulsión
El molde se abre, and the ejector pin pushes out the prototype. The ejection speed should be slow (5-10mm/s) to avoid scratching the prototype (PVC is softer than PE when hot). Después de la expulsión, place the prototype on a cooling rack for 10-15 minutos (room temperature cooling) to stabilize its dimensions.
4. Postprocesamiento: Improve PVC Prototype Quality & Funcionalidad
Postprocesamiento is essential to turn the rough molded PVC prototype into a usable product. PVC prototypes often have flash, uneven edges, or incomplete functions after molding—proper post-processing solves these issues and enhances the prototype’s practicality.
4.1 Key Post-Processing Steps for PVC Prototypes
| Paso | Métodos | Escenarios de aplicación | Quality Control Standards |
| Guarnición | Manual trimming (tijeras, utility knife), Mechanical trimming (rotary cutters), Laser trimming | Manual: Prototipos de lotes pequeños (＜50 pieces); Mecánico: Large-batch (＞100 pieces); Laser: Prototipos de alta precisión (P.EJ., componentes médicos) | Trimmed edges are smooth (no burrs); prototype size deviation ≤±0.1mm |
| Refinamiento | Lijado (800-1200 papel de lija), Pulido (pasta de pulido + cloth wheel), Desengrasante (alcohol isopropílico) | Lijado: Remove surface scratches; Pulido: Improve gloss (P.EJ., decorative prototypes); Desengrasante: Clean oil stains (P.EJ., prototypes for food contact) | Surface roughness Ra ≤0.8μm; no residual polishing paste or degreaser |
| Asamblea | Adhesive bonding (PVC special glue: CPVC solvent cement), Thermal welding (hot air welding gun: 200-220℃), Fijación mecánica (tornillos, clips) | Adhesive: Airtight prototypes (P.EJ., water tanks); Thermal welding: Large prototypes (P.EJ., PVC pipes); Mecánico: Prototypes needing disassembly (P.EJ., test fixtures) | Bonded/welded joints are leak-proof (test with 0.3MPa air pressure); mechanical joints are stable (no loosening under 5N force) |
| Inspección | Inspección dimensional (calibrar, Cmm), Inspección visual (surface defects), Performance testing (resistencia a la tracción, resistencia química) | 100% inspección visual; 10% sampling for dimensional and performance tests | Dimensional accuracy meets CAD design (tolerance ±0.05mm for critical parts); Sin grietas, burbujas, o decoloración; tensile strength ≥40MPa |
| Embalaje | Anti-static bags (for electronic prototypes), Bubble wrap (for fragile prototypes), Corrugated boxes (for transportation) | Anti-static: Avoid electrostatic damage (P.EJ., PVC sensor casings); Bubble wrap: Prevent impact damage (P.EJ., thin-walled prototypes); Corrugated boxes: Ensure safe transportation (batch delivery) | Packaging is intact; prototypes have no damage after 1m drop test |
5. Yigu Technology’s Perspective on PVC Blow Molding Prototype Processing
En la tecnología yigu, Priorizamos “material-formula-machine synergy” for PVC blow molding prototypes. We select SG-5 PVC resin for balanced fluidity and strength, match calcium-zinc stabilizers (ecológico) and DOP plasticizers (Para flexibilidad) a través de 10+ formula tests. For machine setup, we use laser parison controllers to keep thickness variation ≤3% and calibrate temperatures daily (±2℃ accuracy). In blowing, we extend cooling time by 2s for thick-walled prototypes to avoid deformation. Post-processing uses laser trimming (RA 0.4 μm) para piezas de alta precisión. The core is strict control of PVC’s high-temperature sensitivity—each step is optimized to balance quality, efficiency and cost.
Preguntas frecuentes
1. Why does my PVC blow molding prototype turn yellow during processing?
Yellowing is mainly due to PVC degradation caused by excessive temperature or insufficient stabilizers. Primero, check the barrel temperature (ensure it does not exceed 195℃); reduce the temperature of the melt zone (Zona 3) by 5-10℃. Segundo, increase the stabilizer content by 1-2% (use calcium-zinc stabilizers for eco-friendly needs). Finalmente, shorten the material residence time in the barrel (increase screw speed by 5-10rpm).
2. How to choose between adhesive bonding and thermal welding for PVC prototype assembly?
It depends on the prototype’s function and size. Para pequeño, airtight prototypes (P.EJ., 50ml medical bottles), use PVC special glue (CPVC solvent cement)—it cures quickly (10-15 minutos) and has good sealing. Para grande, load-bearing prototypes (P.EJ., 1m-long PVC pipe fittings), use thermal welding (hot air gun at 210℃)—it creates stronger joints (tensile strength ≥35MPa) than adhesive. Avoid adhesive for prototypes used at temperatures ＞60℃ (glue may soften).
3. What is the maximum thickness of a PVC blow molding prototype, and how to avoid deformation?
The maximum practical thickness for PVC blow molding prototypes is 5mm (thicker than that leads to uneven cooling). To avoid deformation: 1) Extender el tiempo de enfriamiento (agregar 1-2 seconds for each 1mm increase in thickness); 2) Use a dual-cooling system (water cooling for the mold + air cooling for the prototype after ejection); 3) Reduce the blow pressure by 0.1MPa (prevents excessive internal stress); 4) Store the prototype at room temperature (20-25℃) para 24 Horas antes de usar (stabilizes dimensions).