Automating for Quality
Coaxial cable is used in a variety of products serving many different markets. It is used to carry higher frequency signals from point A to point B with minimal signal loss and degradation. Cables and interconnect systems are getting smaller, and overall volume is increasing. The most common applications include antenna cabling, cable TV equipment interconnects and automotive applications. In automobiles, for example, more and more systems (satellite radio, AM/FM radio, GPS, cell phones, etc.) are being packed into extremely tight spaces. This increased density of signal carrying cables makes coaxial cable an obvious choice to reduce or eliminate signal interference.
Higher volume jobs for standard applications are usually produced offshore, and smaller jobs are produced locally using varying levels of automation. OEM’s tend to outsource coaxial cable assemblies since they are considered a commodity and not part of their core business. Increasingly, cable and connector manufacturers are producing and providing finished cable assemblies to the OEM’s. Since they manufacture the cable and connectors, these manufacturers have a cost advantage over subcontractors who must purchase the components on the outside.
Cable Preparation
The first step in producing a coaxial cable assembly is to measure and cut the cable to length. Many cables are in the 3 to 12 feet length range and can be produced using an automatic cutting machine and then laid into an automatic stacker. Longer lengths must be coiled and tied for easy handling. A semi-automatic cutting machine (with an optional coiler) can make quick work of this step. The next step is to strip the cable ends to prepare them for termination. This step is best done using a semi-automatic programmable coaxial cable stripper (see photo below). These types of strippers can store parameters for a wide range of cable types and can typically perform a 2 or 3 level strip in approximately 6 seconds. An operator must feed each cable end into the machine and wait until the stripping operation is completed. Fully automatic cable preparation machines are available which eliminate the need for an operator to present each cable end. These machines can measure, cut and strip cables with a cycle time of approximately10 seconds, depending on cable length.
Coaxial cable being stripped on a semi-automatic machine
Connectors and Termination
There are a myriad of connector types on the market, even greater than the number of different cable types that are available. Some connector designs require additional processing steps, such as folding back the braided shield, tinning the center conductor, etc. Older connector types typically have many parts including the rubber boot, crimp ring, connector body, center contact and connector housing. Newer connector types are being introduced which have fewer parts, sometimes only a single part. For example, the Radiall R3C connector (see photo below) is available on reel and can be applied in a crimping press in one operation. These one piece connectors lend themselves to automatic assembly methods. The trend is toward fewer connector parts, making it easier for both manual and automatic assembly methods.
Radiall R3C Coaxial Connector
Semi-Automatic vs. Fully-Automatic Assembly
Regardless of where coaxial cable assemblies are produced, there is a benefit to using partial or fully automatic assembly methods as opposed to strictly manual methods. For smaller batches and frequent changeovers, producing cable assemblies in a semi-automatic work cell is usually more cost effective. Once the production volume increases above 50,000 cable assemblies per month for a given assembly, it makes sense to invest in a fully automatic assembly system. A fully automatic assembly system can be equipped with quality monitoring equipment such as non-destructive pull testers, electrical testers, etc. to ensure that all product is fully tested as it is built. A good/bad sorting station and destructive piece cutter can be added to cut the ends off of any cable assembly that fails any of the quality tests.
Fully automatic coaxial cable assembly system
Conclusion
The use of coaxial cable assemblies continues to increase. Coaxial cable assemblies can be produced using hand tools or using fully automatic equipment with varying levels of automation in between. The level of automation employed usually depends on the typical batch sizes being produced. Low volume, high mix jobs lend themselves to semi-automatic work cell type assembly, and high volume, low mix jobs are best done on fully automatic systems.
Newer connector types have fewer parts. With fewer parts to assemble, it is easier and less expensive to automate the process. This results in lower automation costs and shorter production cycle times than was possible with older multi-part connectors.
The higher the level of automation, the easier it will be to maintain consistent high quality. Of course, it’s possible to manually assemble a coaxial cable assembly but automation is the key to quality.
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