Rotational Molding Mold Process and Engineering Specification for Hollow Plastic Products
Product Overview
Rotational molding molds are essential tools for producing hollow plastic products through a one-piece forming process.
In this process, polymer powder is heated and rotated along two axes, allowing the material to evenly coat the inner surface of the mold.
Compared with injection molding or blow molding, rotational molding is more suitable for large-scale products, complex geometries and customized production requirements.
Process Principle
The rotational molding process typically includes:
Loading polymer powder into the mold
Heating under controlled conditions
Biaxial rotation for material distribution
Melting and adhesion to mold surfaces
Cooling and demolding
No external pressure is applied, and material distribution is controlled by mold geometry and rotational motion.
Rotational Molding Engineering Control Parameters
Product quality in rotational molding depends on precise control of process variables rather than pressure or tooling force.
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Control Factor
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Range
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Engineering Purpose
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Heat Input Profile
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Multi-stage heating curve
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Ensures uniform material melting
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Mold Surface Temperature ΔT
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≤ ±5°C
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Controls wall thickness consistency
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Biaxial Speed Ratio
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1:1 – 4:1
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Influences material flow path
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Powder Size Distribution
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300–500 μm
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Affects melting and adhesion behavior
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Charge Weight
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Based on target thickness
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Determines final wall thickness
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Gelation Time
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Adjustable
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Stabilizes material bonding
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Cooling Rate
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Controlled cooling curve
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Reduces deformation and shrinkage
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Demolding Temperature
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Below softening point
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Maintains structural integrity
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Thickness Variation
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Within ±5%
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Ensures production consistency
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Shrinkage Rate
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1.5% – 3%
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Used for mold dimension compensation
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Rotomolding Mold Capability Specification
This section defines the engineering capability range of mold design and production systems.
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Capability
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Range
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Description
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Max Product Size
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≤ 5000 mm
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Suitable for large tanks and boat structures
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Min Product Size
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≥ 500 mm
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Suitable for small containers
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Max Volume
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≤ 30000 L
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Supports large-capacity hollow products
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Wall Thickness
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3 – 15 mm
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Adjustable based on structural design
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Mold Material
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Aluminum Alloy
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Standard for rotational molding
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Structure Type
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Cylindrical / Rectangular / Complex shapes
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Supports diverse geometries
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Molding Method
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Biaxial rotation
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Standard process
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Production Mode
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Mass production
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Suitable for industrial applications
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Surface Quality
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Controllable
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Depends on machining precision
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Role of Mold in the Process
The mold defines product geometry, dimensional accuracy and wall thickness distribution.
Mold design determines material flow behavior and directly affects forming quality.
Optimized mold geometry enables complex shapes, smooth transitions and functional features.
Mold precision and structural stability are critical for production consistency.
Process Advantages
Seamless one-piece structure
Suitable for large and complex products
Controllable wall thickness distribution
Suitable for multi-variant production
Efficient material utilization
Typical Issues and Engineering Solutions
Uneven wall thickness → Optimize rotation speed and mold design
Stress concentration → Improve geometric transitions
Large part deformation → Control cooling rate
Inconsistent thickness → Adjust heat input and charge weight
Selection Guidelines
Select mold design based on product geometry
Consider size and structural complexity
Verify process compatibility
Optimize mold structure for application requirements
FAQ
Q1: Is high pressure required in rotational molding
A: No
Q2: Is the process suitable for large products
A: Yes
Q3: Can complex geometries be produced
A: Yes
Q4: Does mold design affect product quality
A: Yes
Product Tags:
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Seamless Structure Rotomolding Mold Customized For Hollow Plastic Products Images
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