Custom Waterproof Bulkhead Pass-Thru Added to Overmolded Cable Harness

Challenge

This custom cable assembly project started from a website inquiry from a member of our customer’s mechanical engineering team. They sent in preliminary documentation to our sales team which we reviewed and confirmed that this was a technology and product that we could support. This quickly led to a conference call with the lead engineer to learn more about the project and its design objectives.

This customer makes a variety of consumer products geared towards household bathrooms and spas. These products must work in a warm and humid environment. Since they are consumer products, they cannot be overly expensive. Cost was a major concern, and reliability was also a concern. The customer was looking for a manufacturing partner that could support both the design and manufacturing requirements, offering a high-value solution.

The specific product they were looking for was a medium-complexity cable harness with multiple legs of different types of wire. One of the legs was for some type of ethernet connectivity, one was to power the device, and the other was for low-voltage communication data leg. Where they struggled was combining all these different cable types into one multiconductor cable. More importantly, their biggest design challenge was to overmold some type of bulkhead plate or a grommet onto this that would seal out warm and humid air on one side and protect the delicate electronics on the other.

They had an idea of what they wanted but they did not know how to get there or how to design it so that it was manufacturable. This customer also had to meet their own internal cost and reliability targets for this to be a successful consumer product.

Solution

After reviewing with our sales team and the product manager, we initially tried to define the project and scope of work to make sure we understood their critical requirements and what their timeline was. Right out of the initial discussions, we steered the customer towards separate individual legs for each one of those cable cross-sections. We recommended that it would not be feasible to combine all these different signals into one composite multiconductor cable, but rather keep all the different cable legs separate. With this approach, it would be a better solution for costs, reliability, and lead time. It's also impractical to extrude a custom multiconductor cable for a proof-of-concept stage when several standard cables can do the job.

What we did was take the cables and design a custom overmolded plate that would completely encase these cables, allowing them to be secured to a larger panel that was part of the customer's system. But we still needed a way to seal moisture out between the plate and the customer's panel.

We ended up using three separate cable cross-sections in the design, and we paired that with an ABS injection molded plate that was then overmolded with a softer gasket material to the far side of the plate. We had a handful of critical mounting locations, so female inserts were installed and needed to be precisely located to be able to mate with the rest of the customer's system.

Cable assembly using three separate cross sections

When we started the project, there was a hierarchy of nice-to-have and must-have features identified by our team. Going through this list, we quickly determined we could incorporate all the must-have features, as well as all those nice-to-have features that the customer was trying to incorporate but wasn't sure if they could. We developed a multi-step overmolding process to properly seal the wires, to properly locate the threaded inserts, and then overmold which provided a waterproof seal for the whole system.

Result

The customer was able to (at a very reasonable price and timeline) incorporate a completely custom cable assembly that was effectively three cables in one. The completed assembly was able to meet the IP67 waterproof rating that they required between the two sides of this overmolded plate that we designed and the customers mating panel.

We were able to do this complete design activity in a six- to eight-week timeline from napkin sketch to a production worthy prototype. The customer was able to test that prototype for both electrical functions, as well as the mechanical fit checks. This was part of a new line that they were able to launch, and Epec is continuing to manufacture this customer cable assembly today.

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