Forming cycle is one of the three injection into physical conditions. it is not only the visual representation of operation efficiency, but also an important parameter of quality control.

 

Definition: the time required to complete an injection molding process is referred to as the forming cycle. Complete forming cycle includes mold closing time, injection time, holding time, cooling time and other time.

 

Mold close time (dwell time): refers to the closing time of the mold before injection molding. If the mold closing time is too long, that is, the cooling time is too long, then the mold temperature is too low, in addition, the melting material in the barrel of the residence time is lengthened accordingly (continuous operation). On the contrary, the mold temperature will be high. Mold temperature directly affects the flow and cooling characteristics of the melt, which then affects the final performance of the product.

 

 

Injection time: the injection starts at the mold cavity full of this period of time, that is, the axial travel time of the screw or plunger. In actual production, injection time ranges from a few seconds to ten seconds depending on the size of the product. It is determined by the injection speed and the mold cavity size. And the injection speed mainly affects the flow behavior of the melt in the mold cavity.

 

Packing time: the period in which a mold cavity is filled until it continues to pressurize. That is, the residence time of the screw or plunger in the forming position. When the pressure is too high, there will be a large residual stress. And it is easy to overflow and edge, which makes the strength decrease, and even makes the demoulding difficult. When the packing pressure is too low, it is easy to cause the products not to be compacted and poor forming effect.

 

Mold cooling time: refers to the time required for the end of the mold until the die opening time, including the back-off time of the screw or plunger. It is mainly affected by the thickness, thermal properties (heat capacity and thermal conductivity) and die temperature of the product.

 

The selection of cooling time is based on the principle that the product does not deform during demoulding, When the cooling time is too long, the whole production cycle will be elongated and the production efficiency will be reduced, leading to difficult demoulding. However, when the cooling time is too short, the product is prone to deformation and other defects.