ABS Injection Mold Anti-Cracking Methods
2025-12-30 17:10:14
ABS Injection Mold
ABS resin is widely used in home appliances, auto parts and other fields due to its excellent impact toughness, heat resistance and processing fluidity. However, during injection molding, ABS injection molds are prone to cracking due to material characteristics, design flaws, unbalanced process parameters and improper maintenance. This not only affects production continuity but also causes product quality issues such as dimensional deviations and appearance defects. Combining current injection molding technology trends and practical experience, the following professional anti-cracking methods for ABS injection molds are sorted out from four core dimensions: mold design optimization, process parameter control, raw material management and mold maintenance. Relevant data are based on industry-recognized standards to ensure practicality and accuracy.
I. Optimize Mold Design
1 Reasonably Plan Mold Structure and Wall Thickness
Uneven wall thickness is a major cause of cracking. Differences in melt cooling shrinkage rates generate internal stress. The wall thickness difference of each part should be controlled within 15% during design. Reinforcing ribs can be added to optimize the structure if necessary to avoid excessively thick or thin local areas.
2 Properly Set Gates and Runners
Gate positions should be selected at the geometric center or stress-balanced areas of products. Multi-point gates can improve melt filling uniformity. Runners should preferably adopt circular cross-sections, with the main runner diameter not less than 8mm to reduce melt flow resistance and avoid local pressure concentration-induced cracking.
3 Optimize Cooling System
Uneven cooling exacerbates cracking. The distance between cooling water channels and cavity walls should be uniform, generally 15-20mm. Adjust the cooling water channel layout according to different materials; for example, crystalline plastics require enhanced cooling, while amorphous plastics need to avoid over-cooling.
II. Precisely Control Process Parameters
1 Control Temperature Parameters
Barrel temperature should match the melting characteristics of raw materials. For common PP materials, it should be controlled at 180-230°C. Excessively high temperature will aggravate melt degradation, while excessively low temperature will increase filling pressure, both prone to causing deformation. Mold temperature is adjusted by material; for PP materials, it is controlled at 30-60°C to ensure stable product cooling.
2 Adjust Injection and Holding Pressure Parameters
Injection pressure is controlled at 70-100MPa. Adopt graded injection mode: low-speed filling of gates in the early stage, medium-speed filling of cavities in the middle stage, and low-speed holding pressure in the later stage to avoid high-pressure impact on molds from high-speed injection. Holding pressure is set at 60%-70% of injection pressure, and holding time is 5-10 seconds to ensure full product compaction while reducing continuous stress on molds during holding.
III. Strengthen Raw Material Management
1 Strictly Control Raw Material Drying and Purity
ABS resin has strong hygroscopicity. It should be dried at 80-90°C for 2-4 hours before molding to control moisture content below 0.1%, avoiding high-pressure bubbles generated by moisture vaporization in the barrel that impact the mold cavity. Meanwhile, raw materials should not be mixed with metal impurities to prevent scratching the mold surface during molding and forming crack sources.
2 Standardize Raw Material Modification and Usage
If ABS raw materials need modification, compatibilizers should be used to improve the binding force between modified components and matrix resin, avoiding excessive melt viscosity fluctuations caused by uneven components and increasing mold stress. The addition of recycled materials should be controlled within 30% to prevent impurities and degraded components in recycled materials from aggravating mold wear.
IV. Enhance Mold Maintenance
1 Daily Cleaning and Lubrication
After each production, promptly clean residual scraps in mold cavities and runners to avoid affecting subsequent molding or scratching molds during molding. Regularly lubricate moving parts such as guide pillars and bushes with high-temperature resistant lubricating oil to reduce friction and wear and prevent local stress cracking caused by frictional heating.
2 Regular Inspection and Maintenance
Establish a regular mold inspection system. Inspect key parts such as cavities, cores and gates for cracks and wear after every 10,000 mold cycles. Repair tiny cracks by argon arc welding in time and reheat treat to eliminate stress; severely worn parts should be polished or replaced to avoid small defects expanding into mold scrapping.
Summary
The prevention and control of ABS injection mold cracking runs through the entire process of mold design, process control, raw material management and maintenance. The core is to avoid stress concentration, reduce molding damage and mold loss. By optimizing mold structure and materials, precisely controlling process parameters, strictly managing raw material quality and strengthening daily maintenance, the probability of mold cracking can be effectively reduced, mold service life prolonged, and the production efficiency and quality stability of ABS injection products guaranteed.
