HMI Head Feeders - To mold or not to mold?

Overmolding HMI head feeders provides numerous opportunities within the entertainment industry to reduce the total cost of ownership in cable assemblies and repairs. More importantly, overmolding will reduce costs in HMI ballast repairs as well. The actual process of overmolding is nothing new. Injection molding of thermoplastic materials has been around since the 1950’s and chances are that every single electronic device in your house from computers to appliances to table lamps now have molded connectors versus older technology consisting of multiple pieces and screws that would often come apart over time.

The Problem

The majority of HMI head feeder failures are caused by breakdowns in the insulation where the contact pins meet the wire. This is a typical view of what you might see if you opened up one of your 18k HMI cables.

As we can see the head feeder’s failure was caused by twisting of the cables and the breakdown of the tubing insulation. This usually happens because most field operators use the rear shell to twist lock the connector rather than the front locking rings. This unfortunately is a very common mistake.

However, that alone does not cause the failure. Over time, the heat that is generated near the connector due to dirty or loose pins or by under gauged conductors, causes the shrink tubing to expand and contract. This leads to insulation leaks and eventually, expensive ballast repairs.

The Solution
The two fundamental cores of properly over-molding cables are first, to fully encapsulate the contact and wire termination point; Second, to provide a good mechanical strain relief. These two fundamentals ensure that you will never have insulation leaks in the area that causes over 80% of cable failures.

The most common fear is that if the connector is overmolded, how the user would go about getting inside to fix it. The question then becomes, "What needs to be fixed?"
Broken terminations or pushed pins are the most common problem. Other problems may be fractured or broken wire terminations because of the cable pulling away from the connector and its mounting hardware in the back shell.

We’re so confident that this process works as promised that we offer a LIFETIME warranty on the molding itself!

The Process
The back-end structure of the circular connector dictates the design approach of the premold. The preferred method is to mold fully around the back section of the connector with full encapsulation of the individual conductors and the cable jacket. In situations where there is a screw-on back shell, the ideal configuration is to mold fully over the threads. At this point, there is full attachment between the connector and the premold providing a mechanical bond between the cable and the connector. Each style of connector is different and in certain instances, modification of the connector body is necessary for structural bond between the premold and connector.

Using the appropriate method, a completed premold provides a significantly strong bond between the cable and the circular connector along with environmental sealing of the terminations as an added benefit. In addition to the structural advantages of a premold, it is often possible to eliminate the internal use of heat-shrink tubing and other wire prep devices, as the contact area is fully molded and provides isolation of the contacts and wires. Another advantage of a premold is the elimination of pushed pins in the connector because the premold fills this section of the overmold, capturing the contacts and disallowing them to push out of the connector housing. This premold also provides a surface around which to shield the connector body with copper tape for shielding, if needed.

The Savings
The cost of constantly repairing cables is a large expense of both time and money that can be eliminated with this injection molding process. In addition, overmolding will save thousands of dollars on ballast repairs and not to mention the downtime for your customers. A typical 18k 50ft cable with over-molding is priced roughly the same as a regular 18k head feeder. Additionally, we do offer repairs to existing cables for about the same cost as a traditional repair.

Current Advocates of Molded 18k Head Feeders:

Universal Studios

Cinelease, Inc.

Paskal Lighting

Paramount Pictures

Pacific Grip and Light

DR&A

JR Lighting

Filmtrade

Pacific Grip and Lighting

PS Production Services



MACCAM specializes in this featured product and in assembling custom equipment packages that require components from multiple vendors. Be sure to call or email us with your specific, multiple brand name needs and we’ll be happy to conveniently bring it all together for you.


Call (818) 780-5600 or Email quote@maccam.tv to get a quote today.



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