Analysis of Injection Molding Machine Filling Speed Settings: Professional Practice by Funeng Precision Engineering

During the injection molding process, the setting of the filling speed directly affects the product’s surface quality, dimensional accuracy, and production efficiency. As a key player in the injection molding industry, Funeng Precision has accumulated extensive practical experience in optimizing injection molding machine filling‑speed settings.

The Importance of Filling Speed

The close relationship between injection speed and part quality makes it a critical parameter in injection molding. By defining the start, middle, and end of each filling‑speed segment and ensuring smooth transitions between set points, a stable melt surface velocity can be maintained, thereby achieving the desired molecular orientation and minimizing internal stresses.

Funeng Precision Engineering has accumulated extensive experience in setting segment‑by‑segment filling speeds. In production practice, technicians have found that appropriately optimizing these speeds not only affects the part’s appearance but also directly impacts its mechanical properties and dimensional stability. During the first stage, a low injection speed is used to gently advance the melt from the nozzle toward the cold slug well; once the cold slug has been cleared, the second‑stage injection speed is increased to fully fill the cavity, thereby minimizing the time it takes for the melt at the gate to travel to the far end and keeping the melt viscosity as low as possible to prevent premature solidification. However, achieving precise control over the pressure‑holding switch‑over point at high injection speeds can be challenging, so multi‑stage deceleration is essential to effectively manage this transition. When the gate area is relatively thick, excessively fast injection can induce turbulence, leading to residual cold material in the flow path and resulting surface marks; therefore, a slow, low‑pressure approach should be employed to push aside the cold slug and allow the downstream melt to enter smoothly. Furthermore, staged reductions in injection speed during the holding phase help reduce residual stresses in the finished part.

Funeng Precision Engineering emphasizes that the geometry of the mold is a critical factor in determining the filling speed. Thin-walled sections require the highest injection speed, while thick-walled parts necessitate a slow–fast–slow velocity profile to prevent defects. To ensure part quality meets specifications, the injection speed should be set so that the melt front velocity remains constant. Since melt flow velocity influences molecular orientation and surface finish, deceleration is recommended when the melt front reaches intersecting regions. For complex molds with radial flow patterns, it is essential to ensure uniform increases in melt throughput. Long flow paths must be filled rapidly to minimize cooling of the melt front.

Filling Speed and the Resolution of Common Quality Issues

Meanwhile, Funeng Precision Engineering has successfully addressed numerous common product quality issues by optimizing the filling speed.

Adjusting the injection speed can help eliminate defects caused by flow deceleration at the gate. As the melt travels through the nozzle and the runner to reach the gate, the melt front may already have cooled and solidified, or the melt may become stagnant due to a sudden narrowing of the runner, until sufficient pressure builds up to push the melt through the gate. This results in a pressure spike at the gate, leading to surface defects.

Accordingly, we control the injection‑molding speed during the final stage to prevent or minimize defects such as flash, scorching, and trapped air. Slowing down the injection at the end of the filling phase helps avoid overfilling of the mold cavity, thereby preventing flash and reducing residual stresses. Trapped air caused by inadequate venting at the end of the flow path or by filling issues can also be mitigated by reducing the venting rate, particularly during the final stage of injection.

Conclusion

At Funeng Precision Engineering, most injection‑molding defects can be resolved by fine‑tuning the injection speed. Therefore, mastering the injection‑molding process hinges on appropriately setting and segmenting the injection velocity. Precise speed control is key to enhancing product quality and serves as a vital technical advantage that enables Funeng Precision Engineering to maintain its competitive edge in the market. By employing scientifically calibrated speed settings and meticulous segmented control, Funeng Precision Engineering has not only elevated the aesthetic quality of its products but also markedly improved their mechanical properties and dimensional stability, delivering higher‑quality injection‑molded components to its customers.

Looking ahead, as injection molding technology continues to advance, Funeng Precision will further deepen its research into fill‑speed settings, steadily enhancing product quality and production efficiency.