The Challenges Of Coding On Wire And Cable

One of the last things you may think about in your production environment is the process of coding or marking the wire jacket. Of course, because of the extreme environment in which wire and cable is extruded and the varying environments for wire harness, effective and efficient coding and marking is not always simple. By carefully assessing your coding needs and aligning them with the best coding technology, you will be rewarded with a permanent, efficient, and reliable coding solution.

The first considerations when coding in any environment should be:     What do your customers want?

     What do customers want you to print?

     At what point in your production process can you get this accomplished?

Industrial laser marking has developed into a well-established technology. Laser marking does not require inks, stamps, or ribbons to generate a code.

For years, wire and cable production has been accomplished in long runs with constant codes. This process has been well serviced by contact coding using gravure print wheels. In today’s market, when you may be faced with finding a different solution for every order, think about finding flexible solutions or make sure that the printer and inks chosen can shift between a variety of codes on a variety of jackets and in a variety of environments. Thinking about the flexibility you require up front can save time and money down the road, and give you the ability to better meet your needs and those of your customers.

Recent trends in the market have moved toward increasingly shorter runs, each with their own coding requirements. Customers require an increasingly differentiated product, with a greater mix of jacket material and colors. In addition, many manufacturers are looking for branding opportunities as well as points of differentiation. Many times, the most visible method to achieve this is through variable coding applied inline. With this increasing need for differentiation, the manufacturer and assembler must make sure their coding solution can achieve this flexibility.

Within the wire and cable market, both for extrusion and wire harness assembly, there are several key factors to consider. (See adjacent box.) Once you know these factors, it will be easier to choose which marking and coding technology is best for your application. There are a range of ink jet and laser coding solutions that can meet the needs of extrusion manufacturers and wire harness assemblers.

Traditionally, the wire and cable market has centered around PVC, cross-linked PE, and LDPE substrates. In addition, most marks have been readable with either a black or opaque white ink. Today, these applications still account for almost 70 percent of the wire coding market. However, in order to meet the emerging variety of wire applications, there are now a variety of jacket types, including HDPE, nylon, Teflon, and silicon. Coding and marking companies have been working to keep up with these trends and have now developed a variety of solutions, both ink jet and laser, to code on a wide variety of substrates. In addition, new inks are being developed in a variety of colors to allow for more brand identity and differentiation on the jacket.

Continuous ink jet technology offers a low-cost and flexible way to print up to four lines of continuously changing information on wire and cable.

Permanence of the code is of highest importance. These wires are exposed to a variety of difficult elements, both during and after manufacturing. The combination of the type of material, the temperature of the material and factory, and timing of the process makes it challenging to achieve excellent, lasting adhesion.

Another aspect of the process to consider is the amount and type of handling the wire will endure. While laser coding eliminates any worries in this area, you can also get excellent, lasting adhesion if you choose the right ink. There are a variety of tests you can perform to ensure that the coding solution you are choosing will give you the permanence you need. “Rub” and “pink pearl” tests are standard across the industry and test the durability of the code in heavy-handling environments. Scratch tests are also useful for testing adhesion in more abrasive environments.

Interestingly, there are some coding applications that are specifically designed to come off. For example, codes applied at the original point of extrusion may later be replaced with codes applied during assembly that not only incorporate the information from point of manufacturer, but include additional information required for future users in the supply chain.

The final test of durability is around ink transfer. In many extrusion environments, the jacket is subject to quick rewind, where a “just coded” wire is then immediately placed adjacent to other wire. This poses an additional challenge to the code, but one that can be overcome with both ink jet and laser solutions.

Within the extrusion market, there are many challenges that arise from the actual manufacturing process and production environment. Temperature and moisture challenge the adhesion and durability of the code.

Many extrusion manufacturers choose to incorporate a corona or plasma treatment to the wire immediately before coding, particularly on HDPE. This prepares the jacket by temporarily adjusting the surface of the jacket to be more receptive to ink, which adds to the adhesion of the code.

Within the wire harness environment, dealing with “cool” jackets, or those that are equal to ambient temperature, make adhesion to various plastics more challenging. In addition, these jackets are usually contaminated with dirt and dust, or emitting plastizers. All of this can be overcome by qualifying an ink that meets an individual operation’s environmental and production requirements. Similar to extrusion, corona and plasma treatments many be used to help achieve a greater degree of permanence on particularly difficult jacket materials. Other options include UV cure inks which provide a high degree of solvent and abrasion resistance.

An environment challenge comes from the need for quick change and frequent starts and stops in production. Inks that can achieve good adhesion on a variety of substrate types and colors are ideal. This will minimize the need to change ink types or to “shift change” printers on a single line.

Finally, the manufacturer needs to assess line speed and make sure that the coding solution can deliver a consistent, readable code every time. Depending on the speed required, there are many options to ensure an accurate code, every time. Traditional ink jet coding can print up to around 400 meters per minute.

The most prevalent solution for non-contact coding on wire and cable, both at the point of manufacture and wire harness assembly, is continuous ink jet (CIJ). Choosing the right solution is driven by the variety of needs discussed previously. Non-contact CIJ is the most common technology used for variable coding and marking in wire and cable operations, and originated in the late 1960s. It offers a low-cost and flexible way to print up to four lines of continuously changing information, such as serialized length marks and images; production batch, date, and line information; corporate logos; and end-user installation marks and cues. Alpha-numeric and graphic images between 1/32 inch and ½ inch are typically printed.

Industrial laser marking started in the early 1970s, and since then has developed into a well-established technology. Today, laser marking and coding is used in thousands of production lines throughout the world. It can be used for marking numerical codes, 2D-matrix and bar codes, logos and symbols onto a variety of surfaces, including wire and cable.

Lasers do not require inks, stamps or ribbons to generate a code. In modern sealed-off CO₂ laser coders, the infrared laser light is generated via radio frequency discharge in a carbon dioxide gas mixture. The CO₂ laser systems code thermally by changing the surface color, melting, foaming, or removing the material surface.

Careful consideration of the application — substrate, environment, adhesion and permanence needs, anticipated line speeds, and operating costs — is the first and most important step toward determining the right marking and coding technology for your company’s needs. In addition, balancing this with the breadth of applications that are performed today (and anticipated in the future) is a critical step in choosing the best overall solution for your facility. From there, coding and marking supplier representatives can assist in examining the features and costs of various ink jet printers, appropriate inks and specific laser coders. Once all these issues are factored in, actually choosing a marking and coding system becomes the easiest step of all.

Scott Prochaska a supplies manages supplies at VideoJet Technologies Inc., 1500 Mittel Blvd., Wood Dale, IL 60191. His duties include management and strategic planning for inks and supporting fluids used in both the small and large character ink jet coding product lines. He has been with Videojet for seven years. More information is available at www.videojet.com or by calling 630-860-7300.