Marking wire with an identifying number or character has been a necessary part of wire assembly for as long as anyone can recall. Most electrical standards require a mark identifying a specific electrical circuit for tracability in assembly and service
Methods of marking a wire continue to evolve as processing technology improves. New methods are being introduced to compliment existing processing methods which continue to be effective. The result is a wide range of processing options to meet virtually all applications and production volumes.
We will outline some of the more common processing methods and how they are applied in a production environment.
Adhesive labels are an effective method of applying an alpha numeric mark to wire. Processing methods include manual from a box or card, labeling guns and semi automatic systems. Label adhesion can be affected by the type of wire insulation and quality of the label itself. Permanence can be affected by the above plus the operating environment of the wire. The operating environment can include temperature, humidity and the presence of chemicals or contaminants). Cost of application equipment can range from zero (manual) to high (semi-automated, integrated with a cut only or wire cut and strip machine).
Stamprite Machine Hot Stamp Marker
Hot stamp marking is a wire marking process that dates back to World War II. Hot Stamp marking uses heat type and thermal marking foil to place a mark to the surface of a wire. The wire is fed through a guide or anvil and the guide assembly lifts up to contact the heated type surface with the foil sandwiched between the type and the wire. There are two types of hot stamp markers, separate marking type and wheels. The separate marking type are arranged in the desired number sequence and mounted into a type holder. In the case of a wheel type of marker, each wheel represents one character and includes the characters generally used (0-9, A-Z, blank and special marks: right and left arrow and hyphen). Wheel type are quicker to change over and lend themselves better to manual or automatic processing. Actuation is by lever or foot pedal for manual (offline) processing and integrated into a semi or fully automated solution with actuation controlled by the automation system.
Hot stamp marking is less prone to environmental conditions that can affect the adhesion of a wire label. Some industries specify other marking methods as the mark is imprinted to the surface of the wire using heat and there are concerns about potential damage to the insulation. But the cycle time is limited and the heat applied is localized so this processing method is acceptable for the majority of applications.
End marking (same or different number on opposing ends of the wire) and continuous (along the length of the wire at a fixed distance) are normal processing types. Continuous marking does slow down a semi or fully automated wire processing machine as the wire feed must stop during the stamping process. The number of marks and distance between marks affects processing speed.
The type of thermal marking foil used, the temperature of the type and impression time are critical factors for a hot stamp mark. The insulation type and wall thickness normally determine the foil, temperature and cycle time. Marking foil normally comes in rolls and is white or black.
Ink Jet marking is a newer technology relative to hot stamp. Ink droplets are sprayed onto the wire surface in a pattern to form a character or character string. Ink jet marking systems are fully programmable and offer more character options than other methods. These markers can also interface into the operating system of semi or fully automated processing systems. The interface provides programming and processing communication to the marker. End or continuous marking is possible but It is important to note that without a programming interface between the processing machine and marker, only continuous marking can be processed. Line speed is quicker than other processes as the process does stop to apply a mark to the wire.
There are a wide variety of pigmented and non-pigmeted inks available to suit a wide range of insulation types. In addition, chemicals to clean the ink jet head are required to prevent dried ink from clogging the jets. Special handling of ink and chemicals is required and maintenance personnel are normally trained how to properly apply and store chemicals. Ink jet markers are typically dedicated to one type or ink due to the cleaning process required to transition from one ink type to another.
Permanence to an insulation can be a factor as the ink normally does not penetrate below the insulation surface. The mark can rub off in some environments. Using pre or post treatment methods such as plasma or UV curing can improve the adhesion of the ink to the wire.
Marking to heat shrink and applying the marked heat shrink to a wire is another method. The heat shrink tube is marked and cut to length on a dedicated machine. The marked heat shrink tube is applied to the wire manually using the Judco Focus Lite or heat gun. The mark to the heat shrink is applied using methods such as hot stamp or ink jet.
Judco Focus Lite
Laser marking is an emerging marking technology. Line speed is slower than ink jet but suited for continuous marking. Mark characters and character strings are programmable. A black mark is the primary color as the character is burned into the insulation surface. A marking method endorsed by military and aerospace.
Wire Process Specialties provides solutions for processing wire harnesses. Connect Your Way to WPS to see how we can assist your company in their processing problems.