Laser Marking Application Case: Color Marking on Stainless Steel
Laser Marking Application Case: Color Marking on Stainless Steel
Equipment Configuration: Chuangxin MFPT Series MOPA 60W Fiber Laser
Creating colorful patterns on stainless steel surfaces is a “unique specialty” of MOPA lasers—something that ordinary Q-switched fiber lasers cannot achieve. From dazzling effects on brand logos to gradient patterns on crafts, color marking can significantly enhance the visual value and recognition of products.
I. Color Marking Principle
The principle of color marking on stainless steel is the thin-film interference effect:
The laser generates a transparent oxide film on the stainless steel surface. When incident light hits this film, the light reflects off both the top and bottom surfaces of the film, and the two reflected beams interfere, producing a specific color. The thickness of the oxide film determines the displayed color—and the film thickness is precisely controlled by laser parameters (power, speed, frequency, pulse width, hatch spacing).
The advantages of MOPA lasers:
- Independently adjustable pulse width (2-500ns): Pulse width affects the depth of heat diffusion and is key to controlling oxide film thickness
- Extremely wide frequency range (1-4000 kHz): High-frequency bands allow fine-tuned energy input
- Narrow color marking window: Parameters require precise coordination; MOPA enables fine adjustment
II. Equipment Configuration
| Item | Parameter |
| Laser Source | Chuangxin MFPT Series MOPA Pulsed Fiber Laser (60W class) |
| Wavelength | 1066±3nm |
| Repetition Rate | 1-4000 kHz |
| Pulse Width Adjustment Range | 2-500 ns |
| Peak Power | Up to 10kW |
| Beam Quality M² | ≤1.4 |
| Cooling Method | Air-cooled |
The 60W MOPA provides ample power for stable color marking, with headroom for other fine processing tasks—making it the ideal power level for color marking on stainless steel.
III. Parameter Reference
The parameter window for color marking is very narrow. The following are reference starting values. It is strongly recommended to run a parameter matrix test on scrap material, as different stainless steel grades and different field lens focal lengths all affect color rendering.
Common Color Starting Parameters (Reference based on 10W/20W MOPA baseline; 60W requires corresponding adjustment)
| Color | Power | Speed (mm/s) | Frequency (kHz) | Pulse Width (ns) | Hatch Spacing (mm) | Defocus Amount |
| Yellow | 80-100% | 600-900 | 40-60 | 50-100 | 0.01-0.02 | -0.5~-0.8mm |
| Blue | 80-100% | 400-600 | 70-90 | 50-100 | 0.02-0.03 | -0.3~-0.5mm |
| Green | 80-100% | 600-900 | 70-90 | 50-100 | 0.003-0.01 | -0.3~-0.5mm |
| Red | 80-100% | 300-600 | ≥300 | 45-100 | <0.005 | 0~-0.3mm |
| Purple | 80-100% | 500-800 | 50-70 | 50-100 | 0.01-0.02 | -0.3~-0.5mm |
| Gold | 80-100% | 600-1000 | 40-60 | 80-150 | 0.01-0.02 | -0.5~-0.8mm |
60W MOPA Tuning Tip: The above parameters are based on mainstream MOPA color marking experience (10-20W baseline). The 60W has higher power, so you may need to appropriately reduce the power percentage or increase speed. The most reliable method for color marking is: fix the pulse width and frequency, then gradually increase power from a low level and observe the color change path.
Tuning Logic
Color marking is essentially about finding the target color on the energy-color mapping curve. General rules:
- High frequency (>200kHz) + dense hatch (<0.005mm): Colors change along a red → blue → green path as power varies
- With frequency fixed, gradually increase power: Colors typically shift from light to dark, from cool to warm tones
- Pulse width influence: Narrower pulse widths (<50ns) are suitable for fine colors; wider pulse widths (>100ns) produce warmer colors
- Defocus amount: Defocusing is an important means of color marking; both positive and negative defocus can work, and experimentation is needed to determine the best approach
IV. Effect Characteristics
- Color Richness: Can produce yellow, blue, green, red, purple, gold, and many other colors
- Fineness: Colors transition naturally and delicately, supporting gradients and complex patterns
- Durability: Color comes from the oxide film, firmly bonded to the substrate, wear-resistant and corrosion-resistant
- Luster: Metallic gloss texture, no additional coating required
V. Precautions
- Material consistency is critical: Different batches and grades of stainless steel (304 vs 316) show significant differences in color response; re-testing is required when changing materials
- Color marking is slower: Dense hatching + multiple color-tuning passes means per-piece time is much higher than standard marking
- Environmental temperature effects: During prolonged continuous color marking, laser temperature rise may cause energy drift and color shift; intermittent processing is recommended
- Surface cleaning: Fingerprints and oil stains will severely interfere with color uniformity; always wear gloves
- Not all stainless steel can be color marked: Certain surface treatments (brushed, mirror, coated) can affect color rendering
- High-end stainless steel crafts / souvenirs
- Brand logo color identification
- Medical device color coding
- Mobile phone / electronics appearance decoration
- Stainless steel medals / customized gifts
- Industrial equipment panel color-coded identification
VI. Application Scenarios
Summary: Color marking on stainless steel is an advanced application unique to MOPA lasers. The 60W power is sufficient for stable, vibrant color output. The parameter window is narrow and tuning is challenging, but once parameters are locked in, batch production can achieve dazzling color effects that ordinary fiber lasers cannot match—making it an excellent means of product premiumization.
*Color marking is sensitive to materials and environment. It is recommended to confirm results by creating samples with the customer’s actual materials before taking orders.*
