Compression moulding allows parts to be created from a mould by applying pressure to the material. Let us explain what it consists of and its applications.

What is compression moulding and what is it for?

Compression moulding is a forming process that heats and softens a plastic material to achieve a desired shape. Compression moulding is used to mould parts from thermoset materials such as polyesters, polyurethanes, urea-formaldehyde resins, vinyl esters, epoxy resins and phenolic resins, to process thermoplastics, elastomers such as rubbers and silicones for small parts, and glass fibre reinforced composites.

The compression moulding process

The compression moulding process involves preheating and compressing an estimated amount of moulding material to the desired shape through two preheated moulds.

Compression moulding is where the polymer, in powder or putty form, is introduced into a hot, open mould and pressure is then applied to bring the material into the shape of the mould by contacting all parts of the mould while maintaining the heat and pressure until the resin cures.

The process of compression moulding is described in detail below:

1.- Creation of the moulds: by machining processes, die casting or with 3D printing.

2.- Preparation of the machine: by carrying out tasks such as, for example, cleaning the mould or turning on the heaters.

3.- Preparation of the load: the type of material to be used is selected and the quantity required is estimated. If the load is too large, the excess material will leak out of the mould, generating a burr that will have to be removed by hand.

4.- Introduction of the load: the load is placed in the centre of the upper mould.

5.- Compression of the part: the upper mould is closed and pressure is applied waiting for the part to be formed. Sometimes heat is also applied during this process as it softens the raw material helping to speed up the process.

6.- Releasing the part.

7.- Cleaning of the part: the part is cleaned and the burr that protrudes from the edges is removed manually. 

Large industrial machines such as industrial hydraulic compression moulding machines, table presses and cold or wet compression moulding machines are generally used to carry out compression moulding. In addition, small home-made machines, used by home-workers and do-it-yourselfers, can also be employed in this process, allowing complex moulds to be made with a 3D printer and CAD software and even, in small projects, compression can be achieved with a vise or a set of levers. 

The advantages of compression moulding parts

The advantages of compression moulding include its ability to mould large, complex parts and to produce ultra-large basic shapes that are impossible with any other technique. In addition, it creates strong, robust and durable parts that are free of flow lines and welds, offers great design flexibility, is highly suitable for engineers and product developers as it allows the design of simple compression moulds with CAD software, 3D printing and shaping of other materials using only a vise, produces little waste and is the most cost-effective compression method for simple, large and flat parts.

Furthermore, compression moulding provides efficient, automated mass production, low internal product stress and warpage deformation with relatively stable mechanical properties, low cavity wear and low mould maintenance costs.

What products are manufactured by compression moulding?

Compression moulding is typically used for the manufacture of electrical components, e.g. plugs, switches and their plates and gauges, household appliances and kitchenware, such as tableware, including bowls, cups and plates, medical and dental device parts, e.g. syringe plungers and respirator masks, computer and gaming devices, including keypads and game controllers, and gears.

This process is also used to produce buttons, buckles, knobs or handles, electrical appliance housings and large containers.

EONSI, manufacturer of parts for multiple industries

EONSI specialises in designing and manufacturing moulds for compression moulded parts. We have the latest technology in industrial machinery and a team of highly qualified professionals to design, develop and manufacture all types of parts.

At EONSI we manufacture compression moulds for multiple industries ranging from ceramics, mining, food, electronics, kitchen or even medicine. Contact us and we will advise you to find what your company needs.