Turning “High Risk” into a “Stabilizer”: Funeng Precision’s Thick-Wall Injection Molding Process Achieves a Breakthrough

In the injection molding industry, thick-walled parts are a perennial challenge. While they often serve critical functions such as load-bearing, sealing, or structural joining, their substantial wall thickness, slow cooling, and concentrated shrinkage make them prone to sink marks, warping, and dimensional variability. For customers, the real pain point is not whether a trial mold can be run successfully, but rather whether the part can maintain consistent appearance and dimensional stability over long‑term mass production. This, precisely, is where the difficulty in molding thick‑walled components lies.

Thick walls shrink—what appears to be an aesthetic issue is, in fact, a testament to the system’s capabilities. In thick-wall injection molding, the material undergoes a lengthy and complex shrinkage process within the mold cavity. If packing is insufficient, cooling is uneven, or pressure transmission is inadequate, these shrinkage disparities will manifest directly on the part’s surface. Often, the root cause lies not in the process parameters themselves, but rather in whether the mold has been designed with sufficient process margin to accommodate thick-wall geometry and whether the equipment can reliably execute the process. This is why the same part can yield dramatically different results when produced on different molds or with different machines.

From the mold‑making stage, we proactively mitigate shrinkage risks for thick‑walled structures.

In Funeng Precision’s mold‑design philosophy, thick‑walled parts are not treated according to the conventional approach of maintaining uniform wall thickness. Instead, drawing on polymer rheology, solidification‑shrinkage behavior, and molding‑window stability, each potential high‑risk area is proactively planned and optimized.

First, during the product structural design phase, we conduct a dedicated analysis of thick-walled sections based on key parameters such as the material’s linear shrinkage rate, volumetric shrinkage curve, and thermal conductivity. Without compromising mechanical strength or functionality, we employ strategies like localized hollowing, optimized rib placement, and the incorporation of functional transition structures to minimize excess solid volume, thereby fundamentally reducing the risk of dimensional shrinkage and deformation caused by uneven cooling.

Secondly, in gate system design, we emphasize “priority for feeding paths.” Thick-walled areas, with their slower cooling rates and greater shrinkage, rely more heavily on continuous material replenishment. Accordingly, we prioritize configuring these regions with optimal gate types and runner layouts—such as extending the holding‑pressure duration along the flow front, employing high‑efficiency hot runner systems, and optimizing gate size and placement—to ensure that thick sections receive sufficient and stable feed.

Meanwhile, in cooling system design, we employ CAE thermal‑balance analysis to simulate the temperature distribution across both the interior and exterior of the part, with targeted enhanced cooling applied to thick‑walled regions. By incorporating multi‑circuit water channels, localized insert water wells, oblique through‑holes, or high‑thermal‑conductivity inserts, we align the cooling rates across varying wall thicknesses, thereby minimizing defects such as internal stresses, sink marks, and warpage caused by uneven cooling.

It is worth emphasizing that these specialized processing techniques do not make the product drawings overly complex; rather, they significantly broaden the molding window during mass production, reduce shrinkage, scrap rates, and rework probabilities, and ensure stable forming and superior surface quality for thick-walled parts right from the outset.

Stable molding results depend on “controllable injection molding machine performance.”

The requirements for thick-wall injection molding go far beyond simply having sufficient clamping force. Even more critical are stable pressure output, precise switching, and sustained, effective holding pressure. Funei Precision’s tailored injection-molding solutions place particular emphasis on these factors when producing thick-walled parts:

  •   Smooth transition between the injection and holding phases

  •   Precise control of multi-stage speed and pressure

  •   Reliable performance of parameter repeatability under long-term operation

Only when the injection molding machine can consistently and accurately execute the process settings can the process engineer’s expertise truly translate into product quality—rather than relying on “intuitive adjustments.”

In the thick-wall products project, Funeng Precision places greater emphasis on the molding window under mass‑production conditions, rather than merely the single‑part results achieved during the trial‑molding phase. By systematically optimizing mold temperature, holding pressure time, and cooling strategy, the parts remain consistently under control throughout the shrinkage process, thereby mitigating quality risks arising from environmental fluctuations or equipment variability. For customers, this translates into fewer cosmetic defects, more consistent dimensional stability, and a more predictable delivery schedule.

This also marks a crucial step in transforming thick-walled injection-molded parts from “difficult-to-produce” items into “mature, mainstream products.”

Turn complex problems into stable, tangible outcomes that your customers can see.

Shrinkage in thick‑walled injection‑molded parts has never been resolved by a single trick. It demands a company’s comprehensive expertise in mold design, injection‑molding equipment, process optimization, and mass‑production experience. Funei Precision Engineering consistently adheres to a systematic, collaborative approach—spanning product architecture, mold tooling, and molding process planning—to ensure that thick walls no longer pose quality risks but instead enhance product reliability. For our customers, what truly matters is not the complexity of the process, but the stability of the final outcome—and that is precisely the core value Funei Precision Engineering continues to invest in and refine.