What gets marked on LED bulbs
An LED bulb carries its wattage, voltage range, brand, model number and a batch or date code, along with the certification marks that apply to lighting products sold in India. Some makers also mark lumen output and colour temperature, and a QR code that links to product registration or a datasheet. Contract assemblers that build for several brands need to change the brand and model on the mark often, sometimes several times in one shift.
The mark has to cope with heat, because housings and heat sinks run warm for years, and it has to stay readable through dust inside a light fitting. Printed labels can peel or fade with heat, which is one reason makers move to direct laser marking on LED bulbs.
Which laser marking machine suits LED bulbs
For laser marking on LED bulbs, start with the part. Most bulbs have either a plastic housing near the cap, often PBT or polycarbonate, or an aluminium heat sink, sometimes with a plastic sleeve over it. On aluminium heat sinks a fiber laser gives a clean engraved mark quickly, and on painted or powder-coated aluminium it removes the coating for a bright mark. On white plastic housings, a UV laser usually gives a crisp grey mark with little heat damage, while a fiber laser works on grades that contain laser additives. White PC and white PBT react differently, so run trials on both if you use both.
Diffusers are usually clear or opal polycarbonate. Marking them is generally avoided, because any mark shows as a shadow when the lamp is lit; if a mark is needed, a small UV mark near the rim is the gentler option. Driver boards can be marked on the PCB solder mask, where a UV or fiber laser places a serial number or Data Matrix code in a spare area without damaging tracks, so the board can be traced through assembly and testing.
When a printed label still makes sense
Where a bulb housing has no suitable flat area or the plastic gives poor contrast in trials, a heat-resistant printed label may still be the practical way to carry the full data, with the laser marking only a batch code. Outer cartons are usually coded with inkjet rather than laser.
Setting up the job
Bulbs are round, so the fixture usually holds the bulb by its cap or body in a nest that keeps the marked surface square to the beam. Keep text on a curved housing short so it stays in focus across its width; a rotary fixture is rarely needed for a few characters. On high-volume lines, either mark housings or heat sinks before assembly on a tray fixture, or mark finished bulbs at a station on the conveyor triggered by a sensor.
Batch and date codes should come from the line's shift calendar so operators do not change them by hand. Check marked samples after the burn-in or ageing test as well, since heat can shift the colour of a mark on plastic slightly.
What to check before you buy
- Housing material. List the housing plastics and heat sink finishes for each model, and trial each one.
- Mark position. Agree where the mark goes so it is still visible after the bulb is fitted, usually near the cap.
- Diffuser policy. Decide whether diffusers will be marked at all; if so, judge trial marks with the lamp lit.
- Heat stability. Run marked samples through your ageing test to confirm contrast holds.
- Line integration. Check the marker's trigger inputs and cycle time against your conveyor speed.
- Board marking. If driver PCBs need serial codes, confirm the spot size suits the free space on the board.
- Model changeover. Ask how quickly an operator can switch layouts for different wattages and brands.
Laser marking on LED bulbs in Tamil Nadu
LED lighting assembly in Tamil Nadu is carried out by units in and around Chennai's industrial estates and in other industrial towns, many of them building a wide range of wattages on the same lines. Units that assemble for several brands gain the most, because changing a wattage or brand on a laser mark is a software change rather than a new label stock. Laser marking on LED bulbs also suits makers who want the brand on the product itself rather than only on the carton.
NMB Enterprises, based at Poonamallee in Chennai, is an authorised distributor of IndoForeign Technologies laser systems, including UV and fiber markers. Buyers across Tamil Nadu can call or WhatsApp 098417 60722 with photos of their bulb parts and the data they need to mark.