Rotomolding vs Injection Molding: Which Process for Your Protective Case?

Choosing between rotational molding and injection molding is one of the first decisions in protective case sourcing. Each process has distinct advantages, and the wrong choice can result in 30-50% higher costs, longer lead times, or inferior product performance.

How Rotational Molding Works

Rotational molding (rotomolding) is a low-pressure, high-temperature process:

1. Pre-measured polymer powder (usually LLDPE, XLPE, or PP) is loaded into a hollow metal mold
2. The mold is closed, heated to 250-350°C, and rotated biaxially (around two perpendicular axes)
3. Rotation distributes the molten polymer evenly across the mold's interior surface
4. After 20-45 minutes of heating/rotation, the mold is cooled while still rotating
5. The mold opens and the hollow, seamless part is removed

How Injection Molding Works

Injection molding is a high-pressure, high-volume process:

1. Polymer pellets (ABS, PP, PC, PA66, etc.) are melted in a heated barrel at 200-300°C
2. The molten polymer is injected under high pressure (700-1,400 bar) into a closed, two-part steel mold
3. The polymer cools and solidifies in the mold in 30-180 seconds
4. The mold opens, ejector pins push out the part, and the cycle repeats

Direct Comparison: Rotomolding vs Injection Molding

Material Differences

Rotomolding uses primarily LLDPE (linear low-density polyethylene), XLPE (cross-linked polyethylene), and PP (polypropylene) in powder form. Injection molding uses a much wider range of materials including ABS, PC (polycarbonate), PA66 (nylon), PP, PE, POM, and engineering plastics.

The material difference has practical implications:

• Rotomolded cases are typically softer, more flexible, and more impact-resistant at low temperatures
• Injection-molded cases can be rigid, dimensionally precise, and incorporate complex features like hinges, latches, and molded-in threads
• Rotomolded cases have a "softer" feel and matte/orange-peel texture
• Injection-molded cases can have high-gloss, soft-touch, or textured surfaces

Cost Comparison for Typical Case Sizes

Small case (300×200×100mm, 0.5kg)

• Rotomolding: Mold $3,000 / 1,000 parts = $3.00 amortized + $1.50 material = $4.50/unit tooling + material
• Injection molding: Mold $8,000 / 1,000 parts = $8.00 amortized + $1.00 material = $9.00/unit tooling + material
• Winner: rotomolding (for this size and volume)

Medium case (500×400×200mm, 2kg)

• Rotomolding: Mold $5,000 / 1,000 parts = $5.00 + $6.00 material = $11.00/unit
• Injection molding: Mold $25,000 / 1,000 parts = $25.00 + $4.00 material = $29.00/unit
• Winner: rotomolding by 60%+

Large case (1000×600×400mm, 8kg)

• Rotomolding: Mold $8,000 / 1,000 parts = $8.00 + $24.00 material = $32.00/unit
• Injection molding: Mold $50,000+ / 1,000 parts = $50.00+ (often impractical due to mold size and tonnage)
• Winner: rotomolding is the only practical option for cases this large

8 Common B2B Use Cases: Which Process?

1. Drone cases (DJI Mavic, Phantom, Matrice sizes): Injection molding — tight tolerances, hinges, latches
2. Camera/lens cases (Pelican Storm, Gator sizes): Injection molding — precision foam fit, brand color matching
3. Large equipment cases (pelican 1700+ sizes): Either (rotomolding for very large, injection for branded)
4. Military/pelican rifle cases: Injection molding (latches, hinges, wheels, pressure equalization)
5. Industrial storage totes (40L+): Rotomolding — cost-effective for large hollow forms
6. Custom OEM cases with brand logos: Injection molding — better for logo/feature integration
7. Medical/pharma transport cases: Injection molding — cleanability, precision foam fit
8. Marine/outdoor expedition cases: Rotomolding — superior impact resistance, seamless construction

When to Choose Each Process: A Simple Rule

Use this rule of thumb:

• Choose rotomolding if: case volume >5L OR part needs high impact resistance OR low-volume production (<2,000 parts) OR simple shape (no hinges/latches)
• Choose injection molding if: case volume <5L OR high-volume production (>5,000 parts) OR complex features (hinges, latches, molded threads) OR precise color/finish

Conclusion

Rotomolding and injection molding are complementary, not competing, processes. Each has clear advantages for specific applications. At KeXinMaterials, we operate both rotomolding and injection molding lines and recommend the right process based on your case size, volume, feature requirements, and budget. Contact kexin@beeaa.com for a 12-hour response on which process suits your project.

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