The difference between negative engraving and positive engraving

In the laser marking process, negative engraving and positive engraving are two distinct material removal methods. They differ in imaging structure, energy distribution, material deformation mode, and application scenarios. Understanding the technical characteristics of the two processes helps to select the appropriate processing method under different substrate materials and marking requirements. 
I. Definition and Technical Characteristics of Intaglio Engraving 
Engraving by laser ablation or vaporization directly on the pattern area of the material to form a recessed structure is called intaglio engraving. Its imaging feature is that the pattern body is in a "recessed structure" while the background remains unprocessed. 
The technical characteristics of intaglio engraving 
Material removal method: High-energy-density laser is used to remove materials from the target area to form physical grooves. 
2. Depth control: The engraving depth can be controlled by adjusting the laser power, frequency, pulse width and scanning times. Generally, the depth range is between 0.01 and 0.5mm (depending on the material). 
3. Heat-affected zone: The heat-affected zone of intaglio engraving is relatively large, and a remelted and re-solidified layer may appear at the edge of the groove. 
4. Processing speed: Due to the need for multiple accumulative ablations, the speed is slower than that of intaglio engraving. 
5. Applicable materials: metal, stainless steel, aluminum, copper, some hard plastics, etc. 
II. Definition and Technical Characteristics of Relief Carving 
Positive engraving involves laser removal of the non-patterned areas. By blackening, whitening or roughening the background areas, the pattern itself appears naturally raised. No material is removed from the patterned areas. 
The technical characteristics of intaglio engraving 
Imaging method: By processing the background area, the pattern area forms a "convex visual structure" due to the absence of laser influence. 
2. Surface changes: Positive engraving does not produce deep grooves. It mainly results in surface roughening, oxidation or discoloration. 
3. Lower heat-affected zone: The pattern area is not directly ablated, and the heat input is concentrated on the background part. 
4. Processing efficiency: Generally, the processing speed is higher than that of intaglio engraving. 
5. Applicable Materials: Metal, plastic, leather, coated materials, anodized aluminum, etc.
III. Differences in Application Scenarios
Common Applications of Engraving in Relief 
Deep QR code marking 
Deep engraving on metal nameplates 
The workpiece serial number is deeply engraved. 
Deeply engraved characters on molds 
Applications requiring wear resistance and long-term identifiability 
Common Applications of Relief Engraving 
Logo for the shell of electronic products 
Color-changing marking on anodized aluminum surface 
Black marks on the surface of stainless steel 
High-contrast characters on plastic housings 
Fine pattern surface texture treatment 
IV. Principles for Making a Choice Between the Two 
1.For deep engraving, choose intaglio: for instance, mold codes and permanent metal etching. 
2. For high-contrast visual effects, choose raised engraving: for example, the surface graphics of electronic products. 
3. For plastic materials, prefer raised engraving: to avoid melting collapse and charring. 
4. Engraving in intaglio is suitable for occasions where the surface hardness of the metal is high: ensuring legibility and wear resistance.