molding Underflow

ViewMold Co Ltd is an ISO 9001:2000 certified plastic injection molds company that supplies
plastic injection molds
plastic injection molds design
plastic injection molds manufacturing of high quality,plastic injection molding... We are Proud to bring to you the quality and speed you would expect from Viewmold plastic injection molds. We believe we will be your supplier of choice. Just give Viewmold a email or submit a quote online. Our team of quote specialists is the most responsive and the most hands on.

Injection Molding defect:molding Underflow

Solving molding Underflow problems

Underflow is when a flow front reverses direction.

Underflow occurs when flow fronts from two directions meet, pause momentarily, then one of the flows reverses direction and flows back between the outer frozen layers. When the flow reverses direction the frozen layer partly re-melts due to frictional heating.
In the animation below, the gate in the center has a much smaller volume to fill than the other two gates. When the center gate's volume is filled, the other volumes are still filling, so the flow front from the left gate has a lower pressure than the center gate. When the two flow fronts meet, the left flow front reverses direction.
The arrow shows the direction of the underflow.
This flow reversal gives poor part quality, both from surface appearance and structural viewpoints.molding underflow

What to do
Inspect the filling pattern to assess if underflow is likely to occur. Displaying the fill time result at 100% will not indicate the presence of underflow. Play the fill time animation from beginning to end and watch for any flow fronts meeting, then consider the geometry surrounding this point.

Copyright 2006 All Rights Reserved.