Shear rate is too high

About this result

Shear rate is the rate of change of shear strain with time. Shear strain is the ratio of the deformation of the polymer due to a shear force.

The shear rate should be less than the critical maximum value for that material, which can be obtained from the Material Database.

If a part has a yellow or red Quality prediction result, find out why. If it is due to high shear rate, try making some of the changes recommended below.

If the part is mostly green with some small yellow areas, it may be acceptable, but you should look carefully at the other result displays to see exactly how and where further improvement could be made.

Problems caused by high shear rate

High shear rate can cause the material to degrade, become brittle, and have a poor surface finish.

What to do

To reduce the shear rate in an area, you can decrease the material viscosity, ease the polymer flow through the cavity, and consider some of the following recommendations:

• Thicken the part at the end of flow or in thin sections.
• Decrease the injection time which will increase the shear heating, which will decrease the viscosity.
• Increase the melt temperature to decrease the viscosity.
• Select a less viscous material (higher melt flow rate) to enable quicker material flow.
• Increase the gate size which increases the flow rate for a given injection pressure.

Parent topic: Improving Quality Prediction results