This article explains the warping and deformation of plastic parts most clearly! (2）

This article explains the warping and deformation of plastic parts most clearly! (2）

Injection Temperature, Pressure, and Speed ​​Analysis

So, is there a logical relationship between the injection pressure and the melt flow rate and length?

As shown in the diagram: (1) A high pressure gradient results in a high melt flow rate; (2) Under the same pressure gradient, an increase in inlet pressure leads to an increase in flow length; (3) A low pressure gradient results in a low melt flow rate and a low flow length; (4) Under the same pressure gradient, an increase in inlet pressure also leads to an increase in flow length. Question: Can this relationship be quantified?

Relationship between melt speed and pressure gradient

Injection Temperature, Pressure, and Speed ​​Analysis

Below, we will discuss the relationship between them.

According to the simplified theory of classical fluid mechanics, the injection pressure required to fill the molten adhesive delivery system (sprue, runner, and gate) and cavity is related to the materials used, design, process parameters, etc. The following figure shows the functional relationship between injection pressure and various parameters. Let p represent the injection pressure, and n represent the material constant. For most polymers, the n value is between 0.15 and 0.36, with 0.3 being a suitable approximation. Therefore, the injection pressure required for molten adhesive to flow in circular channels such as sprues, runners, and cylindrical gates is:

The functional relationship between injection pressure and the viscosity, flow length, volumetric flow rate, and wall thickness of the material used.