Real-World Injection Molding with “FLUENT-Injection molding”

Is the simulation wrong? Or is it the analyst?

People often say: “The simulation CAN’T predict potential problems!” “The simulation CAN’T help me achieve successful molding!”

These complaints come up often, especially when mold buyers review a Moldflow DFM PowerPoint report and bring their cases to us.

In this instance, we’re dealing with a multiple-valve gate system. The part is over 1,000 mm in length and will be produced using polypropylene (PP) for the automotive industry.

Explanation of the Flow Pattern:

In the image (with key parts hidden for confidentiality), plastic fills the mold starting from the center hot sprue. The graphic uses color shading to indicate the flow:

The plastic begins filling from Gate ①, starting with blue, then transitions to green, yellow, orange, and finally red as the mold fills completely.

Important Observation:

The blue color indicates the flow starting from Gate ①, which is correct. However, look closely! It appears as though the plastic is flowing from the cavity back into the smaller cold gates and runners at Gates ② and ③. This is unexpected because the first fill in these areas is not shown in blue.

Key Question for Mold Buyers:

What do mold buyers really need to know?

A well-prepared Moldflow PowerPoint report?

Or a flawed Moldflow PowerPoint report?

Critical Reminder:

Never allow plastic to flow from the part back into the small cold runners at the valve gate!