Engineered Structural Foam Moulding

The ESF process is a low pressure, thermoplastic, injection moulding process, where an inert gas is introduced into the melted polymer via a blowing agent for the purpose of reducing the density hence the weight of the finished component.
ESF mouldings have a cellular core surrounded by rigid integral skins. This combination results in a moulding of a high stiffness ratio compared with non ESF (compact) mouldings.

The majority of thermoplastics can be foamed; however, some can be more challenging to process. The most common polymers to foam are: High Density Polyethylene (HDPE), Polypropylene (PP), High Impact Polystyrene (HIPS), Acrylonitrile Butadiene Styrene (ABS), Polycarbonate (PC), Polyphenylene Oxides (PPO), Polyphenylene Ether & PPE (Noryl)

Examples of moulded parts and their market are: Operating Theatre Surgical Lamp Casing, Patient Transfer Boards, Medical and scientific enclosures, ATM Facias and POS terminal Cover, CAB Interiors, Dashboard chassis, Kiosk & POS Structures,
Pallets & Transit Cases, Rugged Casings for PCB Boards, Audio Speakers, Filter Frames for Oil Exploration. These are just a few examples.

Yes – With the low cavity fill pressures, the mould tools can be made in lighter grade materials, Aluminium. The costs are up to 30% cheaper than with normal injection moulding. When Structural Foam mouldings are made invariably the mouldings are for engineering applications. The foaming action within the material demands that the material is fed into the mould tools quickly and as such large feed gates are utilized and high injection speeds are necessary.

Yes – However; It is not a good idea to just copy the metal part straight into polymer. Consideration needs to be given to the environment in which it is situated, maximum and minimum service temperatures, chemicals it will likely encounter. The forces it will experience, both static and dynamic force including shock loads. Also ask the question, could the design incorporate other features that will reduce part count.
The part will need to be designed for the polymer selected. We, of course, will offer impartial advice on any project, including the most suitable process and what polymer is the best for your application.

ESF offers design flexibility where complex curves, bosses and product specific features can be introduced, reducing component inventory and cost. Weight saving due to the cellular internal feature. Weight saving can be between 10% and 20% compare to standard injection mouldings. If replacing metal, parts a saving of 30% is not unusual. The components will be rigid but also have a better impact resistance. Because of the low mould pressures and the foaming process residual internal stress is reduced and so reducing any distortion on large flat components. This means a big reduction in sink marks on “A” surfaces – even with substantial ribs and bosses on the “B” surface. Wall sections can vary on a single moulding. Thicknesses of 5mm to 40mm can be achieved on the same part without distortion. Large parts can be moulded on a relative low clamping force press. The limiting factor on component size is Press Platen size and barrel capacity. Components up to 12 kgs have been achieved with ESF.
There are only 2 disadvantages – witness marks on the moulding surfaces known as swirl marks. These do not give a cosmetic surface. As the foaming process needs to be completed the moulding cycle times are longer than standard injection moulding.