How to Decide Whether Rotational Molding is Suitable for a Plastic Product

How to Decide Whether Rotational Molding is Suitable for a Plastic Product?

When evaluating whether rotational molding is the suitable method for manufacturing a plastic product, or whether it is the optimal choice among various plastic molding techniques, it is imperative to consider several factors including the product's design, dimensions, material specification, cost implications, and the expected production volume. The following guidelines can assist in making a decision regarding its suitability.

1. Hollow products

First of all, we need to clarify whether it involves the manufacturing of hollow products. If a product is not hollow or a solid object made by using foam technology, the product is not able to make with rotational molding. If product is designed to be a hollow structure, then there are many methods to choose from in terms of molding technology, such as blow molding, thermoforming and rotational molding. Each technology has its unique advantages and limitations, and there is some overlap and substitutability between these methods. Rotational molding is particularly well-suited for producing complex, hollow shapes that are difficult to create with other manufacturing processes. If your product has a unique design that requires a seamless, one-piece construction, rotational molding might be an excellent option.

Product size

If the designed plastic product is large in volume, and any of its length, width, or height dimensions exceed the processing capabilities of existing blow molding machines or exceed the maximum width of thermoformed sheets available in the market, then blow molding or thermoforming processes may no longer be applicable. In other words, such products can use rotational molding technology for production.

Product shape

After determining that the volume and dimensions of the plastic product are suitable for the three common processes of blow molding, thermoforming, or rotational molding, the next step is to evaluate the specific shape of the product. For designs that are structurally complex, such as filter residue containers, blow molding or thermoforming may not be able to produce a complete single component. In such cases, the rotational molding process becomes the best choice.

Material selection

Rotational molding works best with thermoplastics, which can be melted and re-molded multiple times. If your plastic product is made from a thermoplastic material, rotational molding can be a suitable production method.

Product structure design

In the structural design of the product, if it contains a closed parallel double-wall structure, rotational molding technology is an ideal choice. This is because thermoforming often requires the use of more complex and costly multi-functional molds. At the same time, when products need to have uniform wall thickness or stronger outer corners, rotational molding also shows its incomparable advantages.

Mold Structure

When looking at the mold structure, special attention needs to be paid to its complexity and the fact that it is composed of multiple pieces. If the mold design is complex or consists of multiple independent pieces, automatic demoulding by the machine will become unfeasible. In this case, thermoforming or blow molding processes cannot be applied to the production of the article because these methods do not allow for automated mold ejection. In contrast, rotational molding usually relies on manual demoulding, and even molds with complex structures can be demoulded manually. Therefore, rotational molding has become the only production method for products with this type of mold structure.

Molded-in inserts

When considering the product manufacturing process, if it involves inserts and the application of inserts, the choice of processing method needs to be based on the difficulty of combining the inserts with the product. The rotational molding process offers greater flexibility and efficiency than blow molding and thermoforming in processing complex inserts. In addition, the use of rotational molding technology to embed inserts can ensure a closer combination with the product and greater stability, which is the most outstanding among the three molding technologies.

Cost-effectiveness

When the above comparison method cannot determine the final choice, the production cost and efficiency of the product become key considerations. Although the mold cost of the blow molding method is relatively high, its production speed is fast and the efficiency is high. By calculating the output and efficiency, the cost price can be obtained. For hollow products that are in high demand, blow molding is often the lowest-cost option. Rotational molding has lower mold costs than blow molding and shorter lead times when producing small batches. However, the production efficiency of rotational molding is relatively low. When product demand increases, the cost will rise and its economic advantages will weaken or even disappear. The efficiency and cost of thermoforming are typically somewhere between those of blow molding and rotational molding. Therefore, when the product demand is small, rotational molding is more economical; when the demand is large, blow molding or thermoforming should be considered.

Quality requirements

Rotational molding produces consistent and uniform products with excellent surface finish. If plastic product demands a high level of quality and precision, rotational molding can meet these standards.

When selecting the most suitable molding method for plastic products, it is not a case of excluding all other methods. Indeed, the decision to use a particular method is reached after a comprehensive evaluation of a multitude of relevant factors.