What gets marked on cables
Cable sheath marking is a running legend repeated along the full length. It normally includes the brand, the cable type and construction (number of cores and cross-section), the voltage grade, the standard and certification marks that apply to the product, the year of manufacture and a sequential metre mark. The metre mark lets installers and distributors check the length left in a cut coil, and lets the factory trace a fault back to a production run.
Building wires, power cables, control cables and harness wires each have their own code requirements, and wiring harness makers also mark individual wires with circuit numbers. Because the legend should stay readable for the life of the installation, its resistance to abrasion while the cable is pulled through conduit matters as much as its first appearance.
Which laser marking machine suits cables
Start with the sheath material, because it decides almost everything. Most building wires and many power cables in India are sheathed or insulated in PVC. Laser marking PVC releases chlorine compounds that form hydrochloric acid in moist air, which is harmful to operators and corrodes metal parts of the line and of the laser itself. A general purpose fiber or UV marker on a workbench should not be used on PVC cable. Some cable plants do run dedicated laser coders on PVC sheath, but only with high-volume fume extraction and frequent filter changes, so this is a specialised installation rather than a simple add-on.
For PVC cables, continuous inkjet (CIJ) is the usual method. It prints the legend at extrusion speed in an ink colour that contrasts with the sheath, and NMB deals with Markem-Imaje CIJ printers for this work. Halogen-free sheaths such as XLPE and low-smoke zero-halogen (LSZH) compounds are candidates for laser coding, particularly when the compound contains a laser-marking additive; the mark is permanent and needs no ink. Markem-Imaje laser coders are designed for production lines, while an IndoForeign UV laser marker suits short lengths of halogen-free wire and sample marking off line. Every compound reacts differently, so trial marks on your own sheath are essential before any decision on laser marking on cables.
When CIJ is the better choice
For PVC-sheathed cable, continuous inkjet is the safer and more common method, since it prints at full line speed without releasing hazardous laser fumes. It also lets you choose an ink colour that suits light or dark sheaths.
Setting up the job
On an extrusion line the marking point is usually after the cooling trough, where the sheath has set and is dry. The cable must run steadily at a fixed distance from the print head or laser lens, so a cable guide or a pair of rollers just before the marking point is needed. An encoder on the capstan or a measuring wheel feeds line speed to the coder, so that metre marks fall at exact intervals as the line speeds up and slows down.
The metre counter must restart correctly at each new drum and must not skip or repeat when the line stops. Agree on character height and the gap between legends before trials, then rub the mark and run a sample through the cable's normal handling to check durability. For laser marking on cables of any sheath type, place the extraction nozzle right at the marking point and route the exhaust safely outside the building.
What to check before you buy
- Sheath compound. Name the exact sheath compound for each product (PVC, PE, XLPE or LSZH), since PVC rules out ordinary laser marking.
- Line speed. Give the top line speed for each cable size; the coder must complete each legend within its pitch.
- Metre accuracy. Ask how the coder links to your measuring wheel or capstan encoder and how it handles line stops.
- Diameter range. Check that the guides and mounting cover both your thinnest wire and your largest cable.
- Sheath colours. Trial black and coloured sheaths, since CIJ ink choice and laser contrast both change with sheath colour.
- Abrasion resistance. Test the mark by rubbing it and by pulling a sample through a length of conduit.
- Fume extraction. Any laser coding on cable needs extraction at the head, and for PVC it must be a specialised, properly vented system.
- Changeover. See how quickly the legend text and counter can be changed between product runs.
Laser marking on cables in Tamil Nadu
Wire and cable production in Tamil Nadu includes building wire and power cable units in and around Chennai's industrial estates, and wiring harness work linked to the vehicle plants around Sriperumbudur, Oragadam and Hosur. Harness work needs marked wires and sleeves in large numbers, and electronics assembly around Sriperumbudur adds demand for marked leads and cable assemblies. For most PVC building wire, CIJ remains the practical choice; laser marking on cables makes most sense on halogen-free sheaths and on lines built for it.
NMB Enterprises in Poonamallee, Chennai, deals with Markem-Imaje coding systems and is an authorised distributor of IndoForeign Technologies laser systems. Call or WhatsApp 098417 60722 with your sheath compound, cable sizes and line speed, and NMB will help you compare CIJ with a laser coder for your line.