Plastic Thin-wall Cup Cover Mold

What are thin-wall plastic parts?

Thin-wall plastic parts not only depend on the thickness of the plastic part but also on the flow length to thickness ratio of the plastic and the viscosity coefficient of the plastic. It can be divided into the following three situations:

1. The ratio of low length to thickness (L/T) above 150 is thin-wall injection molding. Flow length refers to the longest distance from the melt entering the mold to completely filling the cavity.

2. The thickness of the plastic part is less than 1mm, and the projected area is above 50cm².

3. For disc-shaped plastic parts, the thickness/diameter ratio of less than 0.05 can be defined as thin-wall plastic parts.

The flow length to thickness ratio of commonly used plastics

LDPE: 270

HDPE: 230

PP: 250

PS: 210

ABS: 190

PC: 90

PA: 170

POM: 150

PMMA: 150

TPE: 150

Good fluidity plastics such as PP, PS, and PE with a viscosity coefficient of 1. When the wall thickness is less than or equal to 0.5mm or the L/T ratio is greater than 150, it is a thin-walled plastic part.

For plastic parts with poor fluidity, the wall thickness should be divided by the viscosity coefficient N. The flow length to thickness ratio of plastic parts should be L/T*N. For example, a cell phone battery case made of PC material has a flow length L=40mm, a thickness T=0.4mm, and a viscosity coefficient N=2. Its flow length to thickness ratio, L/T*N=200.

The viscosity coefficient of thermoplastic: