Disadvantages of Rotomolding Products

Disadvantages of Rotomolding Products

While rotomolding offers significant advantages in specific applications (such as large hollow parts), it also has several drawbacks, primarily summarized as follows:

1. Long production cycles and low efficiency. Heating and cooling are time-consuming: The mold must be slowly rotated and heated in an oven to melt and plasticize the powder, followed by a lengthy cooling and solidification process (usually by air cooling or spraying). Production time per part: A complete cycle typically takes tens of minutes to several hours (much longer than the few seconds to minutes of injection molding). Unsuitable for mass production: Output per unit time is low, making it uneconomical for large-scale production.

2. High raw material costs and limited selection. Expensive powder raw materials: Plastics specifically used for rotomolding must be ground into a fine powder (typically 35-500 mesh), resulting in higher processing costs than standard pellets. Limited material options: While polyethylene (PE) is the dominant material, high-temperature engineering plastics (such as PEEK and high-temperature nylon) are limited in their application due to their high melting temperatures, poor fluidity, and susceptibility to oxidative degradation. The material performance range is limited by the stringent requirements of injection molding materials: excellent thermal stability and melt flow characteristics are required, limiting the application of materials with specialized properties.

3. Product precision and surface quality are relatively low. Dimensional accuracy is poor: molds are affected by thermal expansion, cooling contraction, and rotation, resulting in lower tolerances than injection molding (typically +/-2%, with more complex parts experiencing this). Surface defects are common: orange peel texture (surface unevenness), bubbles (gas trapped during powder melting), and uneven color (powder dispersion issues).

4. Details are weak: forming sharp edges or ultra-fine structures (such as thin-walled holes and precision threads) is difficult. Wall thickness control is limited and uniformity is design-dependent: deep cavities or narrow areas can easily lead to uneven wall thickness due to insufficient powder flow. Localized thickening can be challenging: special techniques (such as embedded insulation) are required to achieve specific area thickening, resulting in complex processes.

5. High energy consumption
Long-term high-temperature operation: Large ovens must be continuously heated to 200-400°C, and the mold's large heat capacity results in significantly higher energy consumption than high-speed molding processes (such as injection molding).

6. Complex process control and reliance on experience.
Parameter sensitivity: Variables such as temperature, rotational speed, and cooling rate have a significant impact on quality.
Long debugging cycles: New molds or new materials require repeated testing to optimize parameters.
Difficult defect traceability: Internal defects (such as bubbles and unmelted particles) are difficult to detect online.

7. Unsuitable for small or solid parts.
Poor economic efficiency: Small parts require fewer parts per batch, but energy consumption and time costs are similar, resulting in a low cost-performance ratio. Solid parts cannot be produced.
Overall, the core disadvantages of this process are:
Slow cycle time → high unit cost, inefficient mass production
Limited material requirements → high raw material costs, making engineering plastics difficult to use
Low precision → rough surface, low dimensional stability
High energy consumption → significant energy consumption during baking and cooling