616.368.2684 chris@bluebilles.com
  • The Problem
    • “How do I know the cavity has a balanced fill.”
    • Unbalanced filling within the cavity can lead to many issues with the final molded part, namely warping.  If the part is not filled evenly, meaning the melt front arrives at both ends of the part, there is little to no chance of packing the part evenly, thus increasing the chances of warping.
    • Uneven filling within the cavity reduces the parts’ ability to perform to customer specifications, namely dimensions.  One end will typically warp more than the other, depending on the molecular density of plastic.
    • A lot of people consider the filling balance of multi cavity molds but fail to recognize the filling imbalance is just as important within the cavity.
  • The Solution
    • SOLIDWORKS Plastics filling simulation.
    • Most tooling and molding professionals consider geometric balance of a mold and runner system during design.  However, before that steps occurs one needs to consider how the cavity is filling and has a balanced fill during injection within the cavity.  Gate placement is critical to performing this step well and if this step is skipped the rest of the downstream process tends not to go well.  Figure 1 shows a gate location that geometrically on center of the part.  Figure 2 shows the result of the unbalanced fill within the cavity.

Unbalanced fill

    • When the gate is placed near the center of the part, the two flow fronts must reach both ends of the part simultaneously.   The geometric center (center or center of the edge) of the molded part is irrelevant, balanced filling is.  This is accomplished through flow simulation, by having the ability to accurately move the gate location, then simulate allows for the precise placement of the gate before the steel is cut.
  • How The Solution Helps
    • By precisely placing the gate, the chances of warping parts, uneven packing does down dramatically.  Figure 3 shows the gate being off center geometrically and when the results are shown in Figure 4, the part is balanced during the filling phase.

Balanced fill

    • The two gate locations look similar in relation to the part, however, they are not.  These are the precise differences that make a part run well or a part you struggle with every time it runs.
    • By running the simulation up front, there is no costly mold rework.  Moving a gate location after a mold has been built is costly and time consuming.  If the mold was a hot runner system?  Pretty much a new hot half, which can be 40% of the original mold build cost.


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BlueBill Engineering Services