Dans le fabrication de prototypes en plastique field, Pp (Polypropylène) Pièces prototypes de moulage par soufflage are highly favored in industries such as packaging, automobile, et appareils domestiques. This is thanks to PP’s excellent properties like light weight, résistance à l'impact élevé, and good chemical stability. Cependant, processing PP blow molding prototypes is not without difficulties. Many manufacturers face problems such as poor parison stability, épaisseur de paroi inégale, and insufficient prototype durability during production. This article will break down the entire processing process of PP blow molding prototype parts based on six core themes, providing practical solutions to common issues and helping you produce high-quality PP prototypes efficiently.
1. Sélection des matériaux: The Cornerstone of High-Performance PP Prototypes
Sélection des matériaux directly determines the basic performance and processing feasibility of PP blow molding prototype parts. Unlike PVC, PP has better thermal stability but is sensitive to external factors like temperature and additives during processing. Choosing the right PP material and matching additives is the first step to ensure prototype quality.
1.1 Key Factors in PP Material Selection
| Facteur | Détails | Impact sur le prototype |
| Polypropylène (Pp) Notes | Homo-PP (rigidité élevée, faible résistance aux chocs), Co-PP (random copolymer: bonne transparence; block copolymer: résistance à l'impact élevé) | Homo-PP is suitable for rigid prototypes like plastic crates; random Co-PP for transparent prototypes like food containers; block Co-PP for impact-resistant prototypes like automotive bumpers |
| Propriétés des matériaux | Densité (0.90-0.91 g / cm³), Point de fusion (160-170℃), Résistance à la traction (30-40 MPA), Force d'impact (2-10 KJ /) | Low density reduces prototype weight; high melting point ensures stability during high-temperature processing; excellent tensile/impact strength enhances prototype durability |
| Matériaux recyclés | Content (0-50%): Low-content (＜20%) maintains performance; high-content (20-50%) reduces cost but lowers strength | For non-critical prototypes (Par exemple, ordinary packaging), 20-30% recycled materials can be used; pour les prototypes de haute performance (Par exemple, pièces automobiles), utiliser 100% virgin PP |
| Additifs | Antioxydants (prevents aging), Stabilisateurs UV (resists sunlight damage), nucleating agents (improves crystallization), colorants | Antioxidants extend prototype service life; UV stabilizers are essential for outdoor prototypes; nucleating agents enhance rigidity; colorants meet appearance requirements |
Une question courante ici est: Why do some PP prototypes become brittle after long-term use? The main reason is improper additive matching—either no antioxidants are added (leading to oxidation aging) or insufficient UV stabilizers are used (for outdoor prototypes). It is recommended to add 0.1-0.3% antioxidants (comme 1010) et 0.2-0.5% Stabilisateurs UV (like UV531) for prototypes used outdoors or in harsh environments.
2. Phase de conception: Lay the Groundwork for Smooth Processing
Le design phase is crucial for ensuring that PP blow molding prototype parts can be processed smoothly and meet functional requirements. 不合理的设计 often leads to processing defects like uneven wall thickness and difficult demolding.
2.1 Core Design Elements for PP Blow Molding Prototypes
| Élément de conception | Exigences | Raisonnement | Exemple pratique |
| Modélisation CAO | Utiliser un logiciel comme SolidWorks, Autocad; ensure 3D model accuracy (tolérance ± 0,05 mm) | Accurate modeling provides a reliable basis for mold making and processing | When designing a 500ml PP bottle prototype, the CAD model should clearly mark the bottle mouth diameter (28MM), hauteur (200MM), and bottom thickness (2MM) |
| Épaisseur de paroi | Épaisseur uniforme (variation ≤8%); minimum thickness ≥0.5mm (pour les petits prototypes), ≥1 mm (pour les grands prototypes) | Uneven thickness causes uneven cooling (leading to deformation); too thin thickness reduces strength | For a PP bucket prototype (diameter 300mm), design the wall thickness as 1.5±0.1mm; Évitez les changements d'épaisseur soudains (Par exemple, from 1mm to 3mm) |
| Géométrie en partie | Évitez les coins pointus (radius ≥2mm); set reasonable draft angle (1-3° for vertical surfaces) | Sharp corners cause stress concentration (easy to crack); draft angle facilitates demolding (PP has high friction) | When designing a PP box prototype with a lid, set the draft angle of the box sidewall to 2°; round the corner between the sidewall and bottom to R3mm |
| Conception de la fabrication (DFM) | Simplify complex structures; avoid undercuts (difficult to demold); reserve trimming allowance (0.5-1MM) | Reduces processing difficulty and cost; ensures smooth production | For a PP handle prototype integrated with a bucket, design the handle as a separate part (assembled later) instead of an integrated undercut structure |
2.2 Erreurs de conception courantes & Correction
- Erreur 1: No draft angle on vertical surfaces → Prototype sticks to the mold during demolding (Facile à rayer).
Correction: Add a 1.5° draft angle; apply a small amount of mold release agent (en silicone) pendant le traitement.
- Erreur 2: Too thin wall thickness (0.3mm for a small bottle prototype) → Prototype is easily crushed (résistance à la traction <25MPA).
Correction: Increase wall thickness to 0.6mm; add a nucleating agent (0.2%) to improve material strength.
3. Blow Molding Process: The Core of PP Prototype Shaping
Le blow molding process is the key link that converts PP raw materials into prototype parts. Each step requires precise control—PP’s high melt viscosity and slow crystallization rate make process parameters critical to prototype quality.
3.1 Step-by-Step PP Blow Molding Process & Control Points
- Extrusion de paraison
Melt PP material (virgin + additifs) in the extruder (barrel temperature: Zone 1=140-150℃, Zone 2=150-160℃, Zone 3=160-170℃). Extrude into a tube-shaped parison at a speed of 10-20mm/s. The key is to ensure parison stability: use a parison controller to adjust the die gap (1-3MM) en temps réel. Par exemple, if the parison is too thick on the left side, reduce the left die gap by 0.1mm.
- Conception de moisissure & Serrage
The mold cavity surface should be polished (RA 0,8 à 1,6 μm) to ensure smooth prototype surfaces. Clamp the parison with a force of 15-30kN (petits prototypes: 15-20KN; grands prototypes: 25-30KN). The clamping time should be 1-2 seconds—too fast causes parison deformation; too slow leads to material cooling (difficult to inflate).
- Blow Pressure & Inflation
Inject compressed air into the parison at a pressure of 0.5-1.0MPa. For thin-walled prototypes (＜ 1 mm), use low pressure (0.5-0.7MPA) Pour éviter d'éclater; for thick-walled prototypes (＞1.5mm), use high pressure (0.8-1.0MPA) Pour assurer une expansion complète. Le temps d'inflation est 3-5 seconds—until the parison fully adheres to the mold cavity.
- Temps de refroidissement & Temps de cycle
Refroidir le prototype avec refroidissement par eau (température du moule: 20-40℃). The cooling time is 5-15 secondes (thinner prototypes: 5-8s; thicker prototypes: 12-15s). PP’s slow crystallization requires sufficient cooling to prevent deformation. The total cycle time (extrusion → clamping → inflation → cooling → ejection) est 20-30 seconds for small prototypes and 30-50 seconds for large ones.
- Éjection
Open the mold and eject the prototype at a speed of 5-10mm/s. PP is hard when cold, so avoid fast ejection (prevents prototype damage). Après éjection, Placer le prototype sur une grille de refroidissement pour 10-20 minutes (refroidissement à température ambiante) to stabilize dimensions.
4. Post-traitement: Enhance PP Prototype Quality & Esthétique
Post-traitement transforms the rough-molded PP prototype into a usable product, solving problems like flash, bords inégaux, and poor surface finish.
4.1 Key Post-Processing Techniques for PP Prototypes
| Technique | Méthodes | Scénarios d'application | Normes de qualité |
| Garniture | Coupe manuelle (ciseaux, couteau utilitaire), Coupe mécanique (coupeurs rotatifs), Coupe laser | Manuel: Petits lots (＜ 50 pièces); Mécanique: Gros lots (＞ 100 pièces); Laser: Prototypes de haute précision (Par exemple, composants médicaux) | Les bords taillés sont lisses (pas de bavures); size deviation ≤±0.1mm |
| Assemblée | Screw connection (vis à taper), Liaison adhésive (PP special glue: acrylic-based), Soudage à ultrasons (fréquence: 15-40khz) | Screw: Prototypes nécessitant un démontage (Par exemple, Test des appareils); Adhésif: Prototypes hermétiques (Par exemple, réservoirs d'eau); Soudage à ultrasons: High-strength joints (Par exemple, pièces automobiles) | Joints are stable (no loosening under 10N force); airtight joints pass 0.3MPa pressure test |
| Finition de surface | Ponçage (800-1200 papier de verre de grain), Polissage (pâte de polissage + roue en tissu), Placage (électroplaste: nickel, chrome) | Ponçage: Remove scratches; Polissage: Améliorer la brillance (Par exemple, prototypes décoratifs); Placage: Enhance wear resistance (Par exemple, handle prototypes) | Rugosité de surface PR ≤ 0,8 μm; no residual sanding/polishing marks |
| Peinture & Impression | Peinture pulvérisée (peinture acrylique), Silk-screen printing (ink: PP special type), Impression | Peinture: Change color (Par exemple, colorful toy prototypes); Impression: Add logos/text (Par exemple, packaging prototypes) | Paint film is uniform (thickness 10-20μm); printing is clear (no blurring, peeling) |
5. Contrôle de qualité: Ensure Consistency & Reliability of PP Prototypes
Contrôle de qualité runs through the entire processing process of PP blow molding prototype parts, ensuring that each prototype meets design requirements and performance standards.
5.1 Full-Process Quality Control Measures
| Control Stage | Inspection Items | Méthodes & Normes |
| Material Incoming | PP resin grade, additive content, Propriétés des matériaux | Check material certificates; test tensile strength (≥30MPa) and impact strength (≥5kJ/m²) via universal testing machine |
| Processing Process | Uniformité de l'épaisseur de la partage, blow pressure, temps de refroidissement | Use laser thickness gauge (variation ≤8%); monitor pressure gauge (0.5-1.0MPA); record cooling time (5-15s) |
| Post-traitement | Trimming accuracy, assembly stability, finition de surface | Measure with caliper (± 0,05 mm); conduct pull test (joints withstand ≥10N); check with roughness tester (RA ≤0,8 μm) |
| Finished Product | Précision dimensionnelle, épaisseur de paroi, défauts (bulles, fissure) | Utiliser la MMT (tolérance dimensionnelle ±0,05 mm); ultrasonic thickness gauge (uniformity ≤8%); 100% inspection visuelle (aucun défaut visible) |
7. Yigu Technology’s Perspective on PP Blow Molding Prototype Processing
À la technologie Yigu, Nous nous concentrons sur “design-process-quality integration” for PP blow molding prototypes. We select block Co-PP for impact-resistant prototypes, matching 0.2% antioxidants and 0.3% nucleating agents via 8+ material tests. En conception, we use CAD modeling with DFM optimization to reduce 30% processing defects. Pour la moulure de soufflage, we adopt intelligent parison controllers (thickness variation ≤5%) and dual cooling systems (shorten 20% temps de refroidissement). Quality control uses 100% CMM inspection and 20% sampling durability tests. The core is leveraging PP’s properties to balance efficiency, cost and performance—each step is optimized for practical application needs.
FAQ
1. Why is the wall thickness of my PP blow molding prototype uneven?
Uneven wall thickness is mainly caused by unstable parison extrusion or improper blow pressure. D'abord, check the parison controller—use a laser thickness gauge to measure 5 points on the parison and adjust the die gap to reduce thickness variation to ≤8%. Deuxième, optimize blow pressure: pour les zones à parois minces, increase pressure by 0.1MPa; for thick-walled areas, decrease by 0.1MPa. Aussi, ensure the mold is evenly cooled (check water circulation in the mold).
2. How to improve the impact resistance of PP blow molding prototypes?
To enhance impact resistance: 1) Choose block Co-PP (impact strength ≥8kJ/m²) instead of homo-PP; 2) Ajouter 5-10% elastomer additives (like EPDM) to the PP material; 3) Optimize design—avoid sharp corners (set R≥3mm) to reduce stress concentration; 4) Ensure sufficient cooling time (extend by 2-3 seconds for thick-walled prototypes) to improve crystallization uniformity.
3. What is the best post-processing method for assembling large PP blow molding prototypes?
For large PP prototypes (Par exemple, 1m-long pipe fittings), ultrasonic welding is the best choice. It uses high-frequency vibration (20-30khz) to bond parts, creating joints with tensile strength ≥35MPa (close to PP’s own strength). Compared with adhesive bonding (slow curing, faible résistance) and screw connection (many parts, easy leakage), ultrasonic welding is fast (cycle time 10-20s), airtight, and suitable for large-batch production. Ensure the welding surface is flat (Ra ≤1,6 μm) for better bonding.