High-density polyethylene (HDPE) makes excellent transit cases, especially when formed by the rotational molding process. HDPE is lightweight, strong, corrosion-proof, and resistant to solvents and acids. It remains stable through a wide temperature range. Rotational molding (roto-molding for short) distributes HDPE powder over the surfaces of a mold. The mold is heated and rotated. This allows liquid HDPE to create hollow shapes with complex geometries.
Other molding processes, like injection and blow molding, become increasingly expensive as the mold tools get bigger. In contrast, roto-molding is very cost-effective for shapes like transit cases. It offers flexibility so designers can produce cases that meet exact specifications.
Some of the advantages of rotationally molded transit cases are:
- Adds extra material in the corners where transit cases suffer most impacts.
- Produces hollow sections with no joints. This helps keep cases watertight. Some will even float!
- Wall thicknesses can be optimized for strength and weight. This provides extra material where it’s needed, leaving other areas thinner for weight savings.
- Other molding processes leave residual stresses in the material, making them prone to distortion and damage. Roto-molding has none of these problems, resulting in strength and dimensional stability.
- The distortion-free process lets designers incorporate interlocking features for safe and easy stacking of cases.
- Roto-molded cases are designed to leave no sharp external corners or edges. This means it’s safer for a person to handle and carry.
- The case color is blended through the material, unlike paint or powder coating. Therefore, it retains its appearance despite the most arduous use.
- Cases can be molded in almost any color without a long production run.
For transit cases, no other manufacturing process offers the advantages of rotational molding. It enables the production of large and complex shapes in low volumes. Designers have the flexibility to maximize strength and durability while minimizing weight and cost.