Process Practice and Optimization of Dalian Sandblasting for Mold Surface Matte Finishing
Matte finishing of mold surfaces is a key procedure to enhance performance and appearance in modern mold manufacturing. It not only reduces surface reflection and avoids optical interference during product molding, but also improves wear resistance and demoldability, extending mold service life. As an important industrial base in Northeast China, Dalian boasts a mature sandblasting processing system and rich mold manufacturing experience, forming an efficient and professional solution for mold matte finishing. This paper analyzes how Dalian sandblasting meets the requirements of mold surface matte finishing from the perspectives of process principle, adaptation strategy and regional advantages.
I. Core Requirements of Mold Matte Finishing and Adaptability of Sandblasting
The core objective of mold surface matte finishing is to achieve uniform and controllable surface roughness (typically Ra 1.6~6.3μm) without damaging the precision and mechanical properties of the mold substrate. Sandblasting impacts the mold surface with high-speed abrasive particles. Through cutting and impact effects of abrasives, it removes surface oxide layers and oil contaminants, and forms micro uneven structures to realize a matte effect. Its advantages are as follows:
High controllability: Surface roughness can be adjusted by changing abrasive types and blasting parameters;
Wide adaptability: Applicable to various mold materials such as steel, aluminum and titanium alloy;
High efficiency: Compared with manual grinding, sandblasting can quickly cover complex cavity surfaces and ensure uniformity.
II. Key Process Steps of Dalian Sandblasting for Mold Matte Finishing
1. Pre-treatment: Ensure Surface Cleanliness
Oil stains, rust or residual release agent on the mold surface will impair sandblasting quality. Dalian sandblasting enterprises commonly adopt ultrasonic cleaning or solvent cleaning to remove surface impurities and provide a clean base for sandblasting. For example, the cavity of injection molds is soaked with neutral detergent and then rinsed with high-pressure water to eliminate residues completely.
2. Abrasive Selection: Match Mold Material and Matte Requirements
Dalian has access to a wide range of abrasives, which shall be selected according to mold material and target effect:
Glass beads: Round particles deliver a soft and uniform matte surface, suitable for high-precision injection molds and precision stamping molds without scratching cavities;
Alumina: High hardness (Mohs hardness 9), ideal for removing stubborn oxide layers and die-casting molds requiring higher roughness;
Silicon carbide: Strong cutting power for cemented carbide molds, with strictly controlled parameters to avoid excessive substrate wear;
Walnut shell/corn cob: Environmentally friendly abrasives for soft aluminum molds or surfaces requiring slight matte treatment, leaving no residues and causing no substrate damage.
3. Parameter Optimization: Professional Control of Matte Effect
Accumulated experience and experimental verification enable Dalian sandblasting enterprises to establish a complete parameter system for different molds:
Blasting pressure: 0.3~0.8MPa (0.5~0.8MPa for steel molds, 0.3~0.5MPa for aluminum molds);
Blasting distance: 10~20cm (too close leads to local over-roughness; too far causes uneven finishing);
Blasting angle: 45°~90° (vertical blasting ensures high efficiency; inclined blasting reduces damage to edges and corners);
Processing time: Adjusted according to target Ra value, generally 30~120 seconds with real-time roughness monitoring.
4. Post-treatment: Guarantee Mold Precision and Cleanliness
After sandblasting, residual abrasives are blown off with compressed air, and the surface is wiped with alcohol or acetone to prevent abrasive particles from scratching products in subsequent molding. Precision molds will undergo dimensional inspection to ensure unchanged cavity accuracy.
III. Regional Advantages and Practical Cases of Dalian Sandblasting
Dalian features a complete mold industrial chain covering automotive, electronic and home appliance molds. Local sandblasting enterprises can customize solutions for different industrial demands:
Automotive mold case: A die-casting mold of an auto parts manufacturer in Dalian required matte finishing for better demoldability. With alumina abrasives, 0.6MPa pressure and 15cm blasting distance, the finished surface reached Ra 3.2μm with uniform matte effect. The mold demolding cycle increased from 5,000 to 8,000 times;
Electronic mold case: A mobile phone shell injection mold demanded low-reflection matte finishing. Glass bead blasting at 0.4MPa pressure and 60° blasting angle delivered a soft surface and eliminated light spots on molded products;
Environmental advantages: Most Dalian sandblasting enterprises are equipped with bag dust removal systems and wastewater treatment facilities, adopting recyclable abrasives such as glass beads to comply with local industrial environmental standards.
IV. Precautions in Adaptation Process
Protection of precision parts: Precision structures such as positioning holes and guide pillars shall be covered with masking tape or special fixtures to avoid sandblasting damage;
Material compatibility: For easily deformable soft materials (e.g., Al-Mg alloy), reduce blasting pressure and processing time to prevent substrate deformation;
Quality inspection: Test Ra value with roughness testers (e.g., Mitutoyo SJ-210) and check uniformity visually to meet customer specifications;
Subsequent treatment: If coating is required after matte finishing, match surface roughness with coating adhesion, and conduct phosphating or passivation if necessary.
Conclusion
Through pre-treatment cleaning, professional abrasive selection, parameter optimization and standardized post-treatment, Dalian sandblasting can efficiently meet the demands of mold surface matte finishing. Relying on regional industrial advantages and technical experience, it provides reliable surface treatment solutions for mold manufacturers and helps improve mold performance and product quality. In the future, with higher requirements for mold surface precision, Dalian sandblasting will further develop toward intelligence and customization, delivering professional services for mold matte finishing.
