How to Do a Good Job of Injection Molding Process?

The process of injection molding mainly includes four stages: filling, holding, cooling and demolding. These four stages directly determine the quality of the product. It is a complete continuous process. Injection parameters


Injection parameters

  1. Injection pressure


Injection pressure is provided by the hydraulic system of the injection system. There are many factors affecting the filling pressure of melt, which can be summarized into three categories: (1) material factors, such as the type and viscosity of plastics; (2) structural factors, such as the type, number and location of the casting system, the shape of the cavity and the thickness of the product; (3) forming process factors.


  1. Injection time


Injection time refers to the time needed to fill the cavity with plastic melt, excluding the auxiliary time of opening and closing the mould. The injection time is much lower than the cooling time, which is about 1/10-1/15 of the cooling time. This rule can be used as a basis for predicting the whole forming time of plastic parts.


  1. Injection Temperature


Injection temperature is an important factor affecting injection pressure. The barrel of injection moulding machine has 5 to 6 heating sections, each material has its appropriate processing temperature (detailed processing temperature can refer to the data provided by the material supplier). The injection temperature must be controlled within a certain range. The temperature is too low, the melt plasticizes poorly, affects the quality of the moulding parts, and increases the process difficulty; the temperature is too high, the raw material is easy to decompose.


Operation process


Filling stage: Filling is the first step in the whole injection cycle, starting from the closure of the mold to the filling of the mold cavity to about 95%. In theory, the shorter the filling time, the higher the forming efficiency. But in practice, the forming time or injection speed are restricted by many conditions.


Pressure holding stage:


The role of the holding stage is to continuously exert pressure, compact the melt and increase the density of the plastics to compensate for the shrinkage behavior of the plastics. In the process of holding pressure, the back pressure is higher because the cavity has been filled with plastic. In the process of packing and compacting, the screw of injection molding machine can only move forward slightly slowly, and the flow speed of plastics is relatively slow. At this time, the flow is called packing flow.


In the holding stage, the cooling and solidification of the plastic wall accelerates, and the melt viscosity increases rapidly, so the resistance in the cavity is very large. In the later stage of holding pressure, the density of material continues to increase, and the plastic parts are gradually formed. The holding stage should continue until the gate solidification seal. At this time, the cavity pressure in the holding stage reaches the highest value.


Cooling stage:


The design of cooling system is very important in injection moulds. This is because only when the plastic products are cooled and solidified to a certain rigidity, can the plastic products be avoided from deformation due to external force after demolding. Because the cooling time accounts for about 70%-80% of the whole molding cycle, a well-designed cooling system can greatly shorten the forming time, improve the injection productivity and reduce the cost. The improper design of cooling system will prolong the forming time and increase the cost, and the uneven cooling will further cause warpage deformation of plastic products.


Demolding stage:


The forming period of injection molding consists of closing time, filling time, holding time, cooling time and demolding time. Among them, cooling time accounts for the largest proportion, about 70%-80%. Therefore, the cooling time will directly affect the length of plastic products forming cycle and the size of production. In the demoulding stage, the temperature of plastic products should be cooled below the thermal deformation temperature of plastic products to prevent the relaxation caused by residual stress or warping and deformation caused by external force of demolding.


JasonMould Industrial Company Limited, established in 2010, is a leading China mold factory. JasonMould specializes in plastic mould production for household appliances, medical equipments, electronic equipments, safety equipments as well as monitoring system.

The company has over 15000 square metres factory. With plastic injection tooling divisions possessing different machinery and expertise, JasonMould offers tools from small and precise mobile phone parts to as big as automotive parts. Our tools are mainly exported to U.S.A., Europe, Japan and UK. JasonMould’s diversification strategy and full service has won compliment from customers all over the world.

Our mission is to provide our customers high quality moulding products and services. We aim to exceed our customers’ expectations of pricing, quality and on-time delivery. To achieve our mission, JasonMould:

  • Commits to continually improve employee skills and efficiency,
  • Provides our employees a clean and safe working environment,
  • Upgrades machine technology and support equipment through a strict maintenance program, and
  • Maintains customers’ tooling to its highest peak of performance

For more about China injection molding cost,please visit

Inquiry Contact:

Contact person: James Yuan

Company name: JasonMould Industrial Company Limited

Address: LongGang Village,LongXi Town,BoLuo County,HuiZhou City,GuangDong Province, China

Telephone: 86-752-6682869

Email: [email protected]


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