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Wire overmolding and successful button mold at first attempt

Updated: Aug 16, 2022

In this case our client was a global high-tech company working on a cutting-edge electro-optic systems for applications in defense and security industries. Their products range from unmounted warrior systems, border surveillance and OEM solutions for airborne and naval integrations.

Over-molding the Cables

Innovation frequently leads to a creation of something customized and non-standard. In this case - custom-made cables. Wire over-moulding process is used to protect cable from strain and bending forces and mechanical wear near the termination points or contacts. Sometimes over-moulding for cables is used not only for cable protection from shocks and folding but also for branding, where companies' logo can be easily casted with plastic injection method. In this case only over-moulded protective covering was required.

CAD Design for Cable Over-moulding Process
CAD Design for Cable Over-moulding Process (1)
CAD Design for Cable Over-moulding Process
CAD Design for Cable Over-moulding Process (2)

Aluminium dies were CNC machined. For encapsulation we used TECHNOMELT® PA678 BLACK thermoplastic polyamid which has good adhesive characteristics and thus is very suitable for encapsulation. Thanks to its low viscosity this plastic can be used for low-pressure injections which is good for over-moulded components located inside the cavity. We also used additional insert seen in the upper and below pictures with wires passing through it. The insert was used to position cable and fully enclose cavity for smooth injection and solidification around the cable. The cable was screwed to the insert to maintain constant positioning and fully enclosed cavity.

Cable Over-molding, mold and inserts
Cable Over-molding in The Process With Insert
Machined Cavity for Insert and Injection
Machined Cavity for Insert and Injection
Encapsulated Cables
Encapsulated Cables

Injection molding might leave minor marks and blemishes - called flashes on a work-piece. These appear due to deviations and errors in mould size and machining inaccuracies, also, due to incorrect pressure settings which should be adjusted during the process. Also, little marks can be seen punched by ejector pins while pushing cast out of the cavity. Usually these drawbacks are unavoidable but can be minimized by using high precision tools and expert level of engineering skills, thankfully, our results prove us to be just like that.

Button Prototype Injection Moulding

There is no secret that electronics industry is high in demand for buttons and switches. Newly designed devices sometimes require custom-made knobs to turn on/off variety of functions. Buttons stand between human and machine and lets interact him with it, thus, its design becomes crucial for good user experience.

We've been contracted to mould prototype button from thermoplastic elastomer (TPE) hardness of 60 Shore A. These kind of materials are a class of co-polymers that has both thermoplastic and elastomeric characteristics. TPE makes button soft, grippy and flexible. However, when making non-standard button, dimensions and form can have huge impact on button's functionality. Button has to bounce back when pushed and create a good user experience by giving a feeling that it has actually been clicked.

Micro Injection Moulded Button from Elastomer TPE
Micro Injection Moulded Button
Micro Injection Moulded Button Aluminium Mould and Cavity
Moulded Button Aluminium Mould and Cavity

As we were about to make prototypes we decided to fit 4 button designs in one mould. However, we also expected that we might get it just right at first trial, so we decided to save on tooling costs and designed only one button with space buffer for 3 more buttons including area for runners and vents. We have used CNC milling for aluminium mould and EDM (electrical discharge machining) for surface finish.

Our expectations were right. The moulded prototype was perfect at first shots. We and our contractor agreed that we can firmly scale production without any further prototyping. Anyway, saved space in the mould will be easily used for future projects, having in mind our close partnership with our existing clients.


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