The Stretch Molding Process
Stretch molding is a process used to create products out of plastics, rubber, and other thermoplastics or thermoset materials. The process is an economical way to create complex shapes and components for many industries. It is often used for products that need to be light weight and yet be able to withstand rugged use and high temperatures.
This process starts with a pre-fabricated plastic or thermoset base material that has been shaped into the desired end product. The material is heated until it becomes malleable enough to be shaped into its final form. This can be done with either a heat press or electric bun foot (EBF). The next step is to introduce a measured amount of rubber or thermoplastic into the material. Depending on the size and shape of the product, this is often done in multiple stages.
Once the material is fully heated and injected with the rubber or other material, the next step is to stretch the material over a desired shape, or mould. This is done through a combination of pressure and pulling, as well as various tools, to work the material into the desired shape. The stretching of the material also helps to conform it evenly into the interior of the mould, allowing a more uniform thickness and shape.
Finally, the product is then cooled in an oven or water cooled area to help it solidify and return to its original, pre-stretched state. Depending on the size of the mould, the cooling process can take from several minutes to several hours.
One of the main advantages of stretch moulding is the ability for accurate definition. The stretching process allows for very precise uniformity, which helps create products with a high degree of detail and accuracy. Additionally, the stretching process means that products can be created that are thinner and lighter than products created through traditional moulding techniques.
However, there are some drawbacks to stretch moulding. First, the process requires a high degree of skill. The bathtub has to be heated precisely, and each time a rubber or thermoplastic is injected, the bathtub and contents have to be cooled to a specific temperature before the next injection can occur. This can be difficult to accomplish in a timely manner if the operator is inexperienced. Second, if air bubbles or other unseen obstructions form and become trapped in the mould, it can cause flaws or weaknesses in the product.
Overall, stretch moulding is a viable option for creating products with complex shapes and that require accuracy and uniformity. Its cost effective nature and ability to create lightweight products make it an appealing option for many industries. That said, the process requires a high degree of skill and knowledge to perform and therefore should only be undertaken by those with the necessary expertise and knowledge.
