What is the flow  length ratio of plastic?

The ratio of the distance the plastic flows to the wall thickness of the product is called the “flow ratio”. That is to say: the ratio of the distance from the nozzle to the flow end of the plastic to the average mold cavity thickness.

Plastic’s fluidity and viscosity are closely related. The lower the viscosity, the better the fluidity, and of course the longer the flow distance.

As the distance of the flow increases, the temperature of the material decreases, the viscosity becomes poor, and filling becomes difficult.

The flow length ratio of the plastic directly affects the number and distribution of the spure points of the plastic product, and also affects the wall thickness of the product.

Different plastics have different flow length ratio, and the smaller the flow ratio, the worse the fluidity will be.

When designing small and medium-sized molds, it is generally not necessary to calculate the flow length ratio, but for large molds, the calculation of the flow length ratio cannot be ignored.

Below is a table of the flow length ratio of common plastic:

flow length ratio of common plastic

Plastic Name

flow length ratio