Choosing Between Overmolded or Field-Assembled Cables

By Contributed Article | August 11, 2014

In an excerpt from a recent white paper, the folks at Switchcraft offer helpful tips for choosing between overmolded and field-assembled cables for your next design.

Figure 1: Sensor-Link molded cable assemblies  are utilized to control molding equipment.

Figure 1: Sensor-Link molded cable assemblies are utilized to control molding equipment.

Cable assemblies are the core components for your most critical connections. In many instances, you’ll have the option of choosing between field-assembled cables or overmolded cables. For some designs the choice will be clear cut; for others not so much.

Field-Assembled Cable

With field-assembled cables, you manually assemble your connectors to your cables. For many designs field-assembled cables will work just fine; and in certain instances they will be your only option, including:

  • You have very specific or custom installations that require a specific length or varied lengths of cable, depending on the install
  • You have to route a cable through a channel or piece of conduit and the design dictates a connector size such that one end of the cable won’t fit through the opening with the connector pre-attached; we see this, for example, in some vehicle-related installations.
  • Your cable will be in a protected environment and once connected it will seldom be disconnected and reattached, i.e. no repetitive use
  • For prototype installations in which the quantity you need is very small

Using Field-assembled Cables: Factors to Consider

Often you’ll have to make a choice between field-assembled cables and overmolded cables. Cost, quality, market, product/application, and end user needs are all among the criteria that will factor into your decision.

How qualified, how experienced, how good are the personnel assembling your cables?

We’re taking it as fact that your cable and connector suppliers are providing you with top-quality, highly functioning components. But the fact is, your field-assembled cable connections are only as good as the people in the field doing the assembling. So if you’re highly confident about the experience and skills of your employees – or those of your contract manufacturer – and this confidence is born out of product performance, then overmolded cables would not seem necessary.

But assembly personnel – both in-house and outsourced – can and do make mistakes. For example, we once worked with a manufacturer that had a problem with its contacts opening up. When we researched the problem, we determined that during the cable assembly process the contractor overheated the contacts when applying solder, which resulted in melted plastic and open contacts. So the customer switched to overmolded cable assemblies and the problem was resolved. In another instance, the contract manufacturer used a sealed IP-rated connector in a cable assembly for a refrigerator ice maker but left out the O ring. This mistake rendered the connector’s IP rating meaningless and severely degraded the performance of the connector and the ice maker.

By no means do we intend the above information to be an across-the-board slam against contractors. There are many outstanding contract manufacturers and we’re familiar with most of them. But before you commit to using the services of a contract manufacturer, make sure you ask how (and how often) they will test your cable assemblies, and be sure you’re comfortable with and confident in the answers you get. This is especially important if your cable assemblies are being used in such critical-functioning applications as bomb suits, commercial pilot headsets, or mission-critical industrial applications.

Cost comparison

Figure 2: "Blue Rain" by Michael Brown, commissioned by the London School of Economics, was installed in July 2009.

Figure 2: “Blue Rain” by Michael Brown, commissioned by the London School of Economics, was installed in July 2009.

Comparing the cost of field-assembled cables to overmolded cables is, for the most part, like comparing apples to oranges. The product costs for field-installable cable assemblies are obviously less expensive, but add in the cost of labor and the costs associated with higher error rates for field-installable cables and you may well come to the conclusion that overmolded cables offer you a lower total cost of ownership.

Overmolded cable assembly

An overmolded cable seamlessly combines the cable and connector into a single part. In overmolding, molten material is injected into a mold cavity and the cooled material conforms to the shape of the mold.

The resulting mold cavity can be plain and simple or quite elaborate, replete with your company name, logo, flanges, an extended strain relief area, and more. Overmolded cable assemblies give you ease of installation and a commonality among installs that you won’t get with field installs.

There are many applications and products for which an overmolded cable assembly is your only choice or clearly your preferred choice.

Figure 3: Cable assembly and LED light bar used in the "Blue Rain” installation

Figure 3: Cable assembly and LED light bar used in the “Blue Rain” installation

Environmental concerns – Unlike with a field-installable cable that’s subject to human error, there’s little to no chance the sealing on your overmolded cable assembly will be compromised. The rear of the connector area is sealed and, barring extraordinary circumstances, will forever remain sealed. Additionally, you can be confident that the connector part of your overmolded cable will perform as rated in harsh weather. This is particularly important for equipment that is continually exposed to moisture or machinery and devices that get regular high-pressure washdowns, such as those used in food preparation and healthcare. For solar applications, you most likely want a harsh environment seal and some UV protection. You can get that with overmolded cable assemblies.

Strength and security of connection – Overmolded cable assemblies have integrated strain relief, giving them the ability to absorb up to seventy pounds of pullout force. Getting this connection strength in a field-installable cable is typically more difficult.

Aesthetics – Sometimes it’s all about the appearance. Medical equipment; high-end, high-tech hardware; any expensive, sleek, high-performance machinery or equipment which should reflect quality calls for overmolded cable assemblies.

For example, a Switchcraft customer and manufacturer of an expensive communications device had been using field-installable cables and electrical tape to form a Y junction on its cables. As you can imagine, the appearance didn’t imply quality and prestige. We suggested an overmolded Y junction cable assembly; the customer implemented our suggestion and loved the new, more professional look.

Flex relief – Overmolded cable assemblies offer the option of a secure flex relief, which will help limit the cable bend radius at the exit of the connector and provide consistent flex relief and higher, longer fatigue. That’s not often the case with a field-installable cable. In addition, overmolded cable assemblies can be used for EMI shielding applications and can be custom designed for right-angle exits or any exit configuration you might require. Plus, overmolded cable assemblies can be color-coded for foolproof equipment installation or usage.

In a controlled environment, for volume installations of equipment, for devices with a limited number of mating cycles and with competent field-assembly personnel, field-assembled cables will usually serve your purposes just fine. In all other instances give strong consideration to using an overmolded cable assembly.

 To read this white paper from Switchcraft and Conxall in its entirety, click here

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