Nel produzione di prototipi di plastica industria, PVC (Polivinil cloruro) blow molding prototype products are widely used in construction, medico, daily chemical and other fields due to their excellent chemical resistance, flame retardancy and cost-effectiveness. Tuttavia, 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, Spessore parete irregolare, 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. Selezione del materiale: Lay the Foundation for Stable PVC Prototypes
Selezione del materiale 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 | Funzione | Impatto sul 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 | Aggiunta 20-40% plasticizer makes the prototype flexible (PER ESEMPIO., medical hoses); Aggiunta <10% keeps it rigid (PER ESEMPIO., plastic containers) |
| Stabilizers | Calcium-zinc stabilizers (environmentally friendly), Lead-based stabilizers (Alta efficienza) | Prevents PVC degradation at high temperatures (avoids discoloration, fragilità) | Calcium-zinc stabilizers are mandatory for food/medical prototypes; lead-based stabilizers are suitable for industrial prototypes (but restricted in eco-sensitive areas) |
| Riempitivi | Calcium carbonate, Talc powder | Reduces costs and improves dimensional stability | Aggiunta 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 (stabile) | Meets the appearance requirements of prototypes | Organic pigments (PER ESEMPIO., phthalocyanine blue) are suitable for decorative prototypes; inorganic pigments (PER ESEMPIO., titanium dioxide) are ideal for white opaque prototypes (better weather resistance) |
Una domanda comune qui è: Why do PVC prototypes often become brittle after molding? The main reason is improper material matching—either insufficient plasticizers (meno di 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. Configurazione della macchina: 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 & Calibrazione
| Setup Item | Core Parameters | Recommended Range for Prototypes | Calibration Method |
| Blow Molding Machine | Screw diameter (30-65mm), Shot volume (50-500ml) | Choose a small screw (30-45mm) per piccoli prototipi (PER ESEMPIO., 50ml bottles); 50-65mm for large prototypes (PER ESEMPIO., 300ml containers) | Test-run with empty material to check if the screw rotates smoothly and the extruder has no material leakage |
| Parison Control | Uniformità dello spessore di Parison, Die gap (1-3mm) | Thickness variation ≤5% (critical for avoiding prototype wall unevenness) | Use a laser thickness gauge to measure the parison at 5 punti; adjust the die lip bolts to correct uneven areas |
| Design dello stampo | Cavity surface finish (RA 0,8-1,6μm), Draft angle (1-3°) | Polished cavity for smooth prototype surfaces; draft angle ≥2° for easy ejection (PVC has high friction) | Apply mold release agent (a base di silicone) 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 (foraggio): 160-170℃; Zona 3 (sciolto): 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 & Soluzioni
- Errore 1: Die temperature too high (＞190℃) → Prototype surface turns yellow (PVC degradation).
Soluzione: Reduce die temperature by 5-10℃; aggiungere 1-2% extra stabilizer to the material.
- Errore 2: Blow pressure too low (＜0.4MPa) → Prototype fails to fully expand to the mold cavity (shape distortion).
Soluzione: 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
IL 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 Secondi) leaves little room for error.
3.1 Step-by-Step PVC Blowing Process & Key Control Points
- Estrusione di Parison
The extruder melts the PVC material (mixed resin + additivi) and extrudes it into a tube-shaped parison. The key is to ensure the parison has uniform thickness and stable extrusion speed. Per esempio, 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 (PER ESEMPIO., reduce the gap by 0.2mm if the parison is too thick on one side).
- Serraggio della muffa
The mold closes quickly (entro 1-2 Secondi) to clamp the parison. The clamping force should be 10-15kN for small prototypes (PER ESEMPIO., 50ml vials) and 20-30kN for large ones (PER ESEMPIO., 500ml jars). Too much force crushes the parison; too little causes air leakage during inflation.
- Air Injection & Inflazione
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: a pareti sottili (＜ 1mm) prototypes need lower pressure (0.4-0.5MPA) per evitare lo scoppio; thick-walled (＞2mm) ones need higher pressure (0.6-0.8MPA) Per garantire la piena espansione. Il tempo di inflazione è 3-5 seconds—long enough for the parison to adhere to the mold cavity.
- Raffreddamento
Raffreddare il prototipo con raffreddamento ad acqua (più efficiente) or air cooling. For PVC, the cooling time is 5-10 Secondi (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.
- Espulsione
Lo stampo si apre, 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). Dopo l'espulsione, Posizionare il prototipo su un rack di raffreddamento per 10-15 minuti (raffreddamento a temperatura ambiente) to stabilize its dimensions.
4. Post-elaborazione: Improve PVC Prototype Quality & Funzionalità
Post-elaborazione is essential to turn the rough molded PVC prototype into a usable product. PVC prototypes often have flash, bordi irregolari, 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
| Fare un passo | Metodi | Scenari di applicazione | Quality Control Standards |
| Taglio | Taglio manuale (forbici, coltello da utilità), Tagliata meccanica (Cutter rotanti), Trigio laser | Manuale: Prototipi di piccoli batch (＜ 50 pezzi); Meccanico: Large-batch (＞ 100 pezzi); Laser: Prototipi ad alta precisione (PER ESEMPIO., componenti medici) | I bordi tagliati sono lisci (Nessun burr); prototype size deviation ≤±0.1mm |
| Finitura | Levigatura (800-1200 carta vetrata a grana), Lucidare (pasta di lucidatura + ruota di stoffa), Sfuggente (Alcool isopropilico) | Levigatura: Remove surface scratches; Lucidare: Migliorare la lucentezza (PER ESEMPIO., prototipi decorativi); Sfuggente: Clean oil stains (PER ESEMPIO., prototypes for food contact) | Rugosità superficiale RA ≤0,8μm; no residual polishing paste or degreaser |
| Assemblaggio | Legame adesivo (PVC special glue: CPVC solvent cement), Thermal welding (hot air welding gun: 200-220℃), Fissaggio meccanico (viti, clip) | Adesivo: Prototipi ermetici (PER ESEMPIO., serbatoi d'acqua); Thermal welding: Large prototypes (PER ESEMPIO., PVC pipes); Meccanico: Prototipi che necessitano di smontaggio (PER ESEMPIO., Test Fidetures) | Bonded/welded joints are leak-proof (test with 0.3MPa air pressure); mechanical joints are stable (no loosening under 5N force) |
| Ispezione | Ispezione dimensionale (pinza, CMM), Ispezione visiva (surface defects), Performance testing (resistenza alla trazione, Resistenza chimica) | 100% ispezione visiva; 10% sampling for dimensional and performance tests | Dimensional accuracy meets CAD design (tolerance ±0.05mm for critical parts); Nessuna crepa, bolle, o scolorimento; tensile strength ≥40MPa |
| Confezione | Anti-static bags (for electronic prototypes), Bubble wrap (for fragile prototypes), Corrugated boxes (for transportation) | Anti-static: Avoid electrostatic damage (PER ESEMPIO., PVC sensor casings); Bubble wrap: Prevent impact damage (PER ESEMPIO., 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
Alla tecnologia Yigu, Diamo la priorità “material-formula-machine synergy” for PVC blow molding prototypes. We select SG-5 PVC resin for balanced fluidity and strength, match calcium-zinc stabilizers (Eco-friendly) and DOP plasticizers (per flessibilità) Via 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) per parti ad alta precisione. The core is strict control of PVC’s high-temperature sensitivity—each step is optimized to balance quality, efficiency and cost.
Domande frequenti
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. Primo, check the barrel temperature (ensure it does not exceed 195℃); reduce the temperature of the melt zone (Zona 3) by 5-10℃. Secondo, 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. Per piccolo, airtight prototypes (PER ESEMPIO., 50ml medical bottles), use PVC special glue (CPVC solvent cement)—it cures quickly (10-15 minuti) and has good sealing. Per grande, load-bearing prototypes (PER ESEMPIO., 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) Estendere il tempo di raffreddamento (aggiungere 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℃) per 24 ore prima dell'uso (stabilizes dimensions).