What gets marked on brake pads
A brake pad is a block of friction material bonded or riveted to a steel backing plate. The marking goes on the exposed back of the plate: pad part number, brand or maker's code, a date code and a batch or shift code. On supplies to vehicle makers, a 2D Data Matrix code (DMC) is often added and linked to the friction mix batch. Some pads also carry a code on the edge of the friction material.
Brakes are a safety part. If a batch draws noise or delamination complaints, the plant needs to trace it to the friction mix batch, the hot press, the curing oven cycle and the grinding line. A date code and batch code on every pad is what makes that trace possible.
Replacement pads sold through dealers also need a clear part number and brand on the plate. Mechanics and buyers use it to match the pad to the vehicle and to tell a genuine pad from a copy.
Which laser marking machine suits brake pads
Backing plates are usually painted or powder coated after pressing and curing. For laser marking on brake pads, a fiber laser removes the coating in the shape of the text and exposes bright steel against the dark paint. Contrast is very good, and a short code typically takes a second or two on a 20 to 30 W source. Check whether exposed steel at the mark is acceptable in your salt spray or storage test, since the bare metal is no longer covered by paint.
Laser marking the friction face itself is possible, but contrast is low on dark composite material, and dust from the mix settles on optics and guides. Most makers keep marks off the friction surface.
Continuous inkjet (CIJ) printing is also used for date codes on pad lines, and Markem-Imaje CIJ printers suit that work. Ink marks are quick to change but can rub off in handling, while a laser mark stays for the life of the pad. A dot pin mark on the raw plate, before bonding, survives the press and the paint shop and is useful when traceability must start at the plate stage.
When dot pin marking is the better choice
If each backing plate must carry its own serial before bonding, a dot pin mark on the raw plate is usually the better method. The indentation survives the hot press and the paint shop, where a light laser mark on bare steel would be covered.
Setting up the job
Pads usually leave the grinding or painting line friction side down, which suits laser marking on brake pads from above. A conveyor with a stop, or a small index table, presents one pad at a time under the head, and the software increments the serial or shift code automatically.
Many pads have an anti-noise shim bonded on the back, which covers part of the plate. Map the exposed area for each pad type and position the mark there. Commercial vehicle pads are larger than car or two-wheeler pads, so check the field covers the mark area on your biggest pad without moving it.
Paint thickness varies between batches. Set parameters for the thickest coat you see, so no text is left with partial paint in it, and verify a DMC sample from each paint batch to ISO/IEC 29158. Removing paint and powder coat produces fumes and fine particles, so place extraction close to the mark point.
What to check before you buy
- Coating type. Send pads with your actual paint or powder coat, since removal speed and contrast differ between coatings.
- Exposed area. Measure the free area left after shims and clips on each pad type before fixing the mark layout.
- Line speed. Compare marking time per pad with your line rate, and decide on a static stop or on-the-fly marking.
- Variable data. Confirm the software rolls date and shift codes over automatically at shift change.
- Pad sizes. Check the marking field against your largest commercial vehicle pad, not only the common car sizes.
- Corrosion test. Run marked pads through your salt spray or humidity test before approving the process.
- Dust protection. Friction material dust is abrasive. Ask how the lens and scan head are protected in a pad plant.
Laser marking on brake pads in Tamil Nadu
Chennai is home to some of India's established brake and friction material manufacturers, supplying the car plants in the Sriperumbudur and Oragadam belt and the two-wheeler and commercial vehicle industry around Hosur. Backing plate stampings and pad assembly work are spread across the suppliers that serve these plants.
NMB Enterprises is based at Poonamallee in Chennai, on the road towards Sriperumbudur. Pad makers in Hosur and elsewhere in Tamil Nadu can call or WhatsApp 098417 60722 with photos of the pad back and coating details, and get a recommendation for laser marking on brake pads on their line.