Shrinkage marks are a common defect that affects the appearance quality and dimensional accuracy of products during precision injection molding. This phenomenon is caused by the volume shrinkage generated during the cooling and solidification of plastics, which forms concave or wavy marks on the surface of the product. To systematically solve this problem, comprehensive optimization is needed from three dimensions: material properties, mold design, and process parameters.
Material selection is the primary step in preventing shrinkage marks. The shrinkage rate of different plastics varies significantly, for example, the shrinkage rate of ABS is about 0.4-0.7%, while that of PP is as high as 1.0-2.5%. For products with strict appearance requirements, it is recommended to use low shrinkage materials or modified materials filled with minerals. Experimental data shows that adding 30% fiberglass reinforcement material can reduce the shrinkage rate by 40-60%. A certain automotive interior manufacturer successfully reduced the depth of surface shrinkage marks from 0.15mm to 0.03mm by switching to low shrinkage composite materials.
Mold design is crucial for controlling shrinkage marks. Reasonable wall thickness design should follow the principle of uniformity and avoid local areas with excessive thickness. When the difference in wall thickness is inevitable, a gradual transition structure should be adopted, and the transition slope is recommended to be controlled within the range of 15-25 °. The optimization of the cooling system is more critical, and the use of 3D printed conformal cooling water channels can increase cooling efficiency by more than 50%. A certain electronic product shell mold has reduced cooling time by 30% and eliminated visible shrinkage marks by optimizing the waterway layout.
The precise control of process parameters is the core of solving the problem of shrinkage marks. The parameter setting during the holding phase is particularly critical, and it is recommended to adopt a multi-stage holding strategy: the initial holding pressure is set to 80-90% of the injection pressure, with a duration of 3-5 seconds; Gradually reduce to 50-60% and maintain for 5-8 seconds. A certain medical device manufacturing enterprise controls the shrinkage rate of its products within 0.3% through this pressure holding method. The melt temperature also needs to be precisely controlled. If it is too high, it will lead to intensified cooling shrinkage, while if it is too low, it will affect the filling performance. For most engineering plastics, it is recommended to control the melt temperature at the midpoint of the recommended material range.
Advanced auxiliary technology provides a new solution for scar control. Gas assisted injection molding technology forms hollow air channels in thick walled areas of the product, effectively reducing material usage and cooling time. After adopting this technology, the shrinkage problem in the 8mm thick area of a certain furniture accessory was completely solved, and material consumption was reduced by 15%. The advancement of mold temperature regulation technology has also brought significant improvements. Dynamic mold temperature control can provide the optimal temperature curve at different stages, reducing surface defect rates by more than 60%.
The intelligent upgrade of the quality monitoring system has achieved preventive control of shrinkage marks. Infrared thermal imaging technology can monitor the cooling process of products in real time and detect potential shrinkage risk areas in advance. A precision parts manufacturer introduced machine learning algorithms to analyze process data and established a shrinkage prediction model, reducing the defect rate from 5% to 0.8%.
To systematically solve the problem of injection molding shrinkage marks, it is recommended to take the following measures: establish a material shrinkage characteristic database, optimize the design scheme using mold flow analysis software, implement precise process parameter control, and introduce an intelligent monitoring system. For appearance parts with strict requirements, rapid cooling and rapid heating forming technology can be considered to improve surface quality by quickly switching mold temperatures.
Shrinkage marks are a common defect that affects the appearance quality and dimensional accuracy of products during precision injection molding. This phenomenon is caused by the volume shrinkage generated during the cooling and solidification of plastics, which forms concave or wavy marks on the surface of the product. To systematically solve this problem, comprehensive optimization is needed from three dimensions: material properties, mold design, and process parameters.
Material selection is the primary step in preventing shrinkage marks. The shrinkage rate of different plastics varies significantly, for example, the shrinkage rate of ABS is about 0.4-0.7%, while that of PP is as high as 1.0-2.5%. For products with strict appearance requirements, it is recommended to use low shrinkage materials or modified materials filled with minerals. Experimental data shows that adding 30% fiberglass reinforcement material can reduce the shrinkage rate by 40-60%. A certain automotive interior manufacturer successfully reduced the depth of surface shrinkage marks from 0.15mm to 0.03mm by switching to low shrinkage composite materials.
Mold design is crucial for controlling shrinkage marks. Reasonable wall thickness design should follow the principle of uniformity and avoid local areas with excessive thickness. When the difference in wall thickness is inevitable, a gradual transition structure should be adopted, and the transition slope is recommended to be controlled within the range of 15-25 °. The optimization of the cooling system is more critical, and the use of 3D printed conformal cooling water channels can increase cooling efficiency by more than 50%. A certain electronic product shell mold has reduced cooling time by 30% and eliminated visible shrinkage marks by optimizing the waterway layout.
The precise control of process parameters is the core of solving the problem of shrinkage marks. The parameter setting during the holding phase is particularly critical, and it is recommended to adopt a multi-stage holding strategy: the initial holding pressure is set to 80-90% of the injection pressure, with a duration of 3-5 seconds; Gradually reduce to 50-60% and maintain for 5-8 seconds. A certain medical device manufacturing enterprise controls the shrinkage rate of its products within 0.3% through this pressure holding method. The melt temperature also needs to be precisely controlled. If it is too high, it will lead to intensified cooling shrinkage, while if it is too low, it will affect the filling performance. For most engineering plastics, it is recommended to control the melt temperature at the midpoint of the recommended material range.
Advanced auxiliary technology provides a new solution for scar control. Gas assisted injection molding technology forms hollow air channels in thick walled areas of the product, effectively reducing material usage and cooling time. After adopting this technology, the shrinkage problem in the 8mm thick area of a certain furniture accessory was completely solved, and material consumption was reduced by 15%. The advancement of mold temperature regulation technology has also brought significant improvements. Dynamic mold temperature control can provide the optimal temperature curve at different stages, reducing surface defect rates by more than 60%.
The intelligent upgrade of the quality monitoring system has achieved preventive control of shrinkage marks. Infrared thermal imaging technology can monitor the cooling process of products in real time and detect potential shrinkage risk areas in advance. A precision parts manufacturer introduced machine learning algorithms to analyze process data and established a shrinkage prediction model, reducing the defect rate from 5% to 0.8%.
To systematically solve the problem of injection molding shrinkage marks, it is recommended to take the following measures: establish a material shrinkage characteristic database, optimize the design scheme using mold flow analysis software, implement precise process parameter control, and introduce an intelligent monitoring system. For appearance parts with strict requirements, rapid cooling and rapid heating forming technology can be considered to improve surface quality by quickly switching mold temperatures.
Send Email
Skype