Injection molding is a widely used manufacturing process that involves injecting molten plastic into precisely designed molds before cooling and ejecting the final part. This process is favored for its ability to produce complex geometries with tight tolerances, versatility with a wide range of materials and colors, and high efficiency, repeatability, and reliability. However, like any manufacturing method, injection molding also comes with its set of drawbacks. In this article, we will delve into the advantages and disadvantages of injection molding, offering a comprehensive analysis to help readers understand the intricacies of this versatile technique.
Advantages of Injection Molding
Complex Geometries with Tight Tolerances
One of the primary advantages of injection molding is its ability to create parts with intricate and complex geometries. The mold design can be tailored to accommodate intricate features, such as undercuts, threads, and fine details, which are challenging to achieve with other manufacturing processes. Additionally, injection molding can maintain tight tolerances, ensuring consistent and accurate part dimensions, which is especially crucial in industries where precision is paramount.
Compatibility with a Wide Range of Materials and Colors
Injection molding provides immense flexibility in material selection, accommodating a wide range of thermoplastic and thermoset materials. This includes but is not limited to polyethylene, polypropylene, polystyrene, polyurethane, and ABS. This compatibility allows manufacturers to choose materials with specific properties, such as strength, rigidity, flexibility, and chemical resistance, tailored to the intended application. Moreover, injection molding supports the incorporation of different colors and additives, enabling the production of visually appealing and functional parts.
Efficiency, Repeatability, and Reliability
Injection molding is known for its high efficiency and speed in producing large quantities of parts. The process can be automated and streamlined, reducing the need for manual intervention and minimizing production time. The consistency and repeatability of injection molding ensure that each part produced matches the exact specifications, leading to reliable and uniform products. This reliability is especially advantageous in industries where product quality and performance are critical.
Low Cost per Part and Low Waste
In comparison to other manufacturing methods, injection molding offers a low cost per part for high-volume production runs. The use of automated systems and reusable molds contributes to cost efficiency, making it an attractive choice for mass production. Additionally, injection molding generates minimal material waste as excess material can be recycled and reused. This reduction in waste aligns with sustainable manufacturing practices and supports environmental conservation efforts.
Disadvantages of Injection Molding
High Initial Tooling Cost and Lead Time
One of the primary drawbacks of injection molding is the significant upfront cost associated with tooling. The design and fabrication of molds can be intricate and time-consuming, which translates to higher initial investment and lead time. This initial tooling cost may be a barrier for small-scale production or prototypes, making it more suitable for larger production runs where the cost per part can be spread over a greater quantity.
While injection molding produces parts with high accuracy and surface finish, some components may require post-processing to achieve specific characteristics or desired aesthetics. Post-processing steps may include trimming excess material, deburring, surface finishing, or adding additional features such as logos or textures. These additional steps can add to the production time and cost.
Limitations on Part Size and Design
Injection molding may have limitations on part size, especially for larger and more intricate components. The size and complexity of the mold can impact production feasibility and cost. Additionally, certain design features may pose challenges in the molding process, requiring modifications to ensure successful production. Design considerations such as draft angles, wall thickness, and corner radii are essential to optimize moldability and part quality.
Injection molding is a versatile and widely used manufacturing process that offers numerous advantages, including the ability to create complex geometries with tight tolerances, compatibility with a wide range of materials and colors, high efficiency, repeatability, and low cost per part. However, it is essential to consider the disadvantages of injection molding, such as high initial tooling cost and lead time, potential post-processing requirements, and limitations on part size and design. Despite these drawbacks, injection molding remains a popular choice for industries seeking efficient, precise, and cost-effective production solutions. By understanding the intricacies of injection molding and considering its advantages and disadvantages, manufacturers can make informed decisions to best suit their specific product needs and optimize their production processes.
1.The advantages of injection molding process
（1） the use of injection mould for the parison wall thickness distribution for precise control, make the container wall thickness is relatively uniform, avoids the general blow molding products of the corner part thinned phenomenon, products can be controlled in a heavy + 0.1 g, the precision of the screw thread can be controlled within the scope of the soil is 100 microns, the mouth size precision, thin neck high precision molding, products;
（2） the products do not need to be processed E times, no seams, saving the finishing hours of products;
（3）The billet made by injection can all enter the blow molding mold, and there is no waste in the processing process, which reduces the waste of molding materials;
（4） can get smooth surface products, no scratch, surface text and design is clear;
（5） can be economically small batch production;
（6） wide range of application to plastic varieties;
（7） high degree of automation, can be multi-mode production, high production efficiency.
2.The disadvantages of injection molding process
- The shrink
Shrinkage generally occurs in the bone position, screw column and other glue position after the comparison of the area.
1) Structural design: uneven design of the workpiece wall thickness or too thick of the workpiece
The glue thickness is as uniform as possible, the uneven position should be smooth transition, and pay attention to the glue.
2) Mold design: the runner is too thin or the mold temperature is too high;
3) Injection design: insufficient pressure holding time, injection pressure is too small;
- Insufficient mold filling
1) Mold temperature, material temperature or injection pressure and speed are too low
2) Uneven plasticizing of raw materials
3) Poor exhaust
4) Insufficient liquidity of raw materials
5) the piece is too thin or the gate size is too small
1) The drying conditions are not suitable, and too much recycled material is used
2) The injection molding temperature setting is unreasonable
3) The gate and runner system are not properly designed
4) Weld mark strength is insufficient
Burned in 4.
1) The drying conditions are not suitable, and too much recycled material is used
2) High melt temperature leads to material degradation
3) The screw speed is too fast
4) Poor exhaust system
- Fly-edge or drape
Often occurs in parting surface, line clamp, inclined top or insert position.
1) Insufficient clamping force;
2) There is wear and tear of the mold, insufficient hardness of the mold, and poor matching of the parting surface;
3) Unreasonable forming conditions (temperature is too high, pressure)
4) Unreasonable exhaust system design;
5) the glue has doping, so that the fluidity of the glue increases or the viscosity decreases;
- Plastic deformation
Internal stress is generated by high pressure during injection molding, and bending or warping occurs after demoulding. The most prone to problems are tablet-style products.
1) Structure design: the product is too thin to cause insufficient strength or too flat;
In structural design, the bone position and glue thickness should be appropriately increased to avoid large area plate products;
2) Mold design: the water outlet setting is unreasonable; The ejection mechanism force is too large;
The deformation of rubber parts should be considered in the design of nozzle.
3) Injection design: long holding time; Large injection pressure;
- More or less glue
Glue position deviation, mainly occurs in the thimble position. Multiple glue to consider whether affect the appearance or assembly, there is no need to not change.
1) Mold design more or less;
2) insufficient thimble length;
~ (If the thimble is too long, the top white will occur, and the injection pressure is too large, the ejection speed or the injection speed is too fast.)
3) Insufficient injection pressure or poor exhaust in the mold cavity
The product is caused by friction mold in the process of demoulding.
1) Structure design: the inclination of drawing die is insufficient;
2) Mold design: the surface accuracy is not enough, and the error is large;
3) Injection design: excessive use of release agent (coating for separating products and molds);
- Clamp water line or weld mark
1) Selection of raw materials: slow flow speed of raw materials and insufficient drying;
2) Mold design: the cold well is too small; The nozzle design is not reasonable; Poor exhaust;
In terms of structure design, bone position can be added in the area where weld marks are easy to be produced.
3) Injection design: mold temperature is too low; Material temperature is too low; Small injection pressure;