Wire Identification Methods 101
Introduction
In today’s wire and cable harness industry, the need for effective wire identification continues to increase. The current wire identification methods are:
- Inkjet Marking
- Hot Stamp Marking
- Labeling
- Heat Shrink
- Thermal Marking
- Laser Marking
This article will describe each identification method, while providing a brief comparison amongst the different processes.
Inkjet Marking
Inkjet technology has improved greatly over the last few years. With less maintenance and quicker start-ups, Inkjet marking systems have grown much more reliable and user friendly.
For the wire and cable industry, it is usually a dye or pigmented ink, with an MEK (Methyl Ethyl Ketone) base. Although rare, alcohol based inks can be used for those who choose to stay away from MEK, (however drying time is increased and production is decreased.) Overall, inkjet marking is the most versatile.
Depending on the interfacing wire processing equipment and software, you can mark on the fly and vary text strings throughout the length of the cable. You can also vary font sizes and bolderization, tower print, and invert the text. Inkjets are dot matrix printers, and the ink is directed onto the wire via deflector plates once it is electrically charged.
Inkjet marking, however, does have its limitations. Certain substrates (insulations) require certain ink types, and marking Teflon is not an option. In addition, if you have a printer with Black ink, you cannot clearly mark on black wire. Since changing ink is not a possibility, it would require the puchase of an additional printer in order to mark in a different color. Typical unit cost: $13.5-22.5K.
Hot Stamp Marking
Hot stamp marking is still the most inexpensive method for wire identification and is the only viable method for marking Teflon insulated wire (with the exception of laser). In order to receive the best quality mark, the are four requirements: You must have the correct air pressure, dwell time, wheel temperature, and foil. The air pressure is the pressure in which the wheels make contact with the wire. This process must create and imprint in the insulation, which could possibly affect the integrity of the jacket.
The dwell time is the length of time in which it takes to complete the whole stamping cycle. The wheel temperature and foil types go hand in hand. The foil consists of a backing and a pigment. The pigment is transferred to the wire insulation via the heat from the character wheels. The backing of the foil must be able to withstand a certain temperature range and therefore can be made up of different materials such as Mylar or Nylon. Certain pigments will stick to certain substrates and will require different temperatures to transfer them. For example, you cannot use a foil that will mark on PVC at 275 degrees for Teflon that may require temperatures of 350-400 degrees.
Although the ability to mark Teflon is a plus, there are some hot stamp marking limitations. For example, while in production, the hot stamp marking machine requires that the master machine (i.e. Wire Cut & Strip Machine, Wire Cutter, Wire Cut-Strip-Terminate Machine), stop for every stamp cycle. The dwell time determines how long the machine is stopped, so the less dwell the better. The more marks that are required - the slower the production rate. In addition, the marking text must remain the same on each cable piece since the character wheels can only be adjusted manually. Typical unit cost: $3.5-7K.
Labeling
Labeling is especially useful when hot stamp or inkjet cannot provide satisfactory results. Labels are printed and then applied automatically. Some labels can also withstand harsh environments such as gasoline and oil. Some labeling systems allow you to program the text to be printed via PC and use a master machine to send a print signal for the label location. Typical unit cost: $12-15K.
Photo courtesy of Gettig Technologies
Heat Shrink
As with labeling, heat shrink can also be an effective method when hot stamp or inkjet marking is not an option. Heat shrink can be marked prior to it being applied to the wire and then heated to shrink.
Thermal Marking
Thermal marking requires a foil and heat, but unlike hot stamp marking, it does not require “impacting the insulation”. This method uses the heat to transfer the pigment from the foil to the wire while it is rolled on. It can mark on both flat and round cables with either black or white markings. Color foil changeover is quick and it can mark logos and other bitmaps. The print resolution is 300 DPI (12 dots/MM). Typical unit cost: $20-25K.
Laser Marking
Laser marking is quite effective for marking Teflon, but for most - it is not a viable option since laser marking is usually too slow or too costly. There are different laser types:
- Vector Based Laser: the wire needs to stop and the laser uses x-y coordinates.
- Mask Type Laser: the mask acts as a type of stencil.
- Carbon Dioxide Laser: destructive and is not typically used for wire and cable.
- UV Laser: Ideal for marking Teflon. However, the teflon jacket must contain Titanium Dioxide in order for a color change to occur.
In a nutshell, the faster the laser system, the more it will cost. Typical unit cost: $125-400K.
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