Analysis Of The Reasons Why Rotational Molding Products Must Be Rounded
Avoiding right angles in rotational molding and adopting rounded corners is a fundamental requirement. This is primarily driven by the characteristics of the rotomolding process and the material properties. The following is an analysis of the specific reasons and impacts:
1. Fundamental Factors Determined by Process Characteristics
Powder Flow Characteristics
Right angles can hinder the flow and distribution of plastic powder within the mold.
Rounded corners ensure uniform powder coverage of every corner of the mold.
Avoids powder accumulation at right angles, resulting in uneven wall thickness.
Heating and Melting Process Requirements
Right angles are prone to overheating (heat concentration).
Rounded corners provide more even heat distribution.
Avoids material degradation or discoloration at right angles.
2. Product Factors Affecting Product Quality
Structural Strength
Right angles are stress concentration points and prone to cracking
Rounded corners disperse stress, increasing product strength by over 30%
Wall thickness at right angles is difficult to control, creating weak points
Mold Release Issues
Right angles increase mold release resistance and can easily damage the product
Rounded corners ensure smoother mold release (reducing release force by approximately 60%)
Avoid deformation caused by vacuum suction at right angles
Appearance Quality
Right angles are prone to defects such as flow marks and wrinkles
Rounded corners create a smoother and more aesthetically pleasing surface
Avoid color unevenness at right angles
3. Recommended Corner Radius Design Specifications
Minimum Corner Radius Radius Standards
General Products: R ≥ 3mm
Large Products: R ≥ 5mm
High-Quality Products: R ≥ 1.5 times the product wall thickness
Special Area Treatment
Root of Rib: R ≥ 1.5mm
Corner Joints: Use Gradual Radius
Functional Areas: Adjust based on actual needs
4. Exceptional Situations
Special Situations Where a Right Angle is Essential
A "Fake Right Angle" Design (Extremely Small Radius + Post-Processing) Can Be Adopted
Use Inserts to Compensate for Process Limitations
Consider Split Design for Post-Assembly
Remedial Measures
Machining the Right Angle Later
Use Filler Material Modification
Use surface treatment to reduce the visual effect of rounded corners
5. Economic Analysis
Mold Cost
Rounded corner mold life is extended by 40-60%
Reduced mold maintenance costs
Reduced mold release agent usage
Production costs
Reduced scrap rate (estimated 15-25%)
Improved production efficiency
Reduced post-processing steps
Summary: The necessity of rounded corners in rotational molded products is a comprehensive requirement of process characteristics, product quality, and economic considerations. The "no right angles" principle should be adhered to during design, with appropriate rounded corner radius settings. In special cases where right angles are unavoidable, alternative processing methods should be employed.