BEC Group Helps Develop Sustainable Overmoulded Acoustic Filter Using Recycled Fishing Nets

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BEC Group has supported Cornwall-based custom earplug specialist Moulded for your Ears in developing an overmoulded acoustic filter and cord retention system that incorporates recycled plastics recovered from discarded fishing nets.

Working alongside product design consultancy VitalSpark, BEC Group provided design-for-manufacture expertise, tooling development, and material evaluation to help commercialise the new filter assembly, which combines hydrophobic mesh technology with precision overmoulding to prevent water ingress while maintaining acoustic performance.

Moulded for your Ears was seeking to improve the performance and manufacturability of the acoustic filter used within its custom-fit water sports earplugs. The filter is designed to allow the flow of sound and air while preventing water from entering the ear canal. This presented a familiar challenge to many filtration and separation applications, where permeability and exclusion need to be carefully balanced.

VitalSpark produced the initial CAD concepts before BEC Group refined the design for injection moulding and volume manufacture. The company subsequently designed and manufactured a dedicated two-cavity overmould tool for filter production, alongside a second tool for the cord retention system.

A key challenge during development was the selection and integration of the filter media. The mesh specification needed to meet hydrophobic performance requirements while allowing sufficient acoustic transmission. Several mesh grades were evaluated during the development process. Initial trials using a finer mesh delivered effective water resistance but restricted sound transmission beyond acceptable levels. A coarser mesh was ultimately selected, providing a more favourable balance between acoustic transparency and water exclusion.

The finished filter is manufactured using a precision overmoulding process in which the mesh is manually positioned onto the tool core before moulding. During injection, the polymer encapsulates the perimeter of the mesh, creating a robust mechanical bond without compromising the open structure of the filtration media.

Mike Tharme, Tooling Director at BEC Group, said: “The filter development process required us to balance several competing performance criteria. The mesh had to repel water effectively while remaining acoustically transparent, and the overmoulding process had to secure the media without affecting its functional properties. Achieving consistent placement and encapsulation of the mesh was critical to the success of the final design.”

Sustainability was also a major objective. Moulded for your Ears and BEC Group evaluated recycled polymers supplied by Waterhaul, a company that recovers and recycles discarded fishing nets from the marine environment.

Initial moulding trials were conducted using recycled HDPE derived from end-of-life fishing gear. However, processing limitations associated with the material and tool geometry led the development team to adopt Waterhaul’s recycled polypropylene grade, which delivered improved mould filling characteristics and greater process stability.

Chris Roynon, Co-Founder of Moulded for your Ears, said: “From the outset, we wanted to improve the filter design while maximising the use of recycled materials. The collaboration with VitalSpark and BEC enabled us to refine both the acoustic performance and the manufacturing process, resulting in a more robust and sustainable product.”

The project demonstrates how filtration media selection, polymer processing and precision overmoulding techniques can be combined to develop compact filtration assemblies that meet demanding performance requirements. It also highlights the growing potential for marine-recovered recycled polymers to be incorporated into technically challenging moulded components without compromising functionality.

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