As the core equipment for WPC product molding, the performance of wood plastic composite material molds directly determines the quality stability, production efficiency, and service life of the final product. In industrial clusters such as Linyi in Shandong, high-performance molds have become a key technological carrier for enterprises to enhance product added value and export competitiveness.
The wear resistance of the mold is its primary performance indicator. Due to the formation of high abrasion melt between wood powder and plastic under high temperature and pressure, the inner surface of the mold is subjected to strong mechanical friction for a long time. To address this challenge, mainstream molds use H13 hot work mold steel and are processed through WPC ® Surface treatment or nitriding, chrome plating processes form a hardened layer with high hardness and low friction coefficient on the surface. The surface hardness of the processed mold can be increased to over 60HRC, and the wear resistance life is extended by 5 to 10 times compared to ordinary steel, effectively reducing dimensional deviations and surface roughness deterioration caused by wear.
In terms of heat resistance and thermal stability, the mold needs to continuously withstand a melt temperature of 180 ° C to 230 ° C and undergo repeated thermal cycles in continuous production. The material must have excellent thermal fatigue resistance and thermal expansion control capability. High quality molds achieve a hardness gradient distribution from inside to outside while maintaining toughness in the core through vacuum quenching and tempering processes, avoiding deformation or cracking caused by temperature difference stress. Molds with insufficient thermal stability are prone to defects such as wavy bending and uneven wall thickness in extruded profiles, which directly affect the product qualification rate.
Dimensional stability is the core of ensuring product accuracy. The proportion of wood fibers in WPC materials is as high as 50% -65%, and its thermal expansion coefficient is much lower than that of plastic matrix, which easily generates internal stress during the molding process. Mold design must accurately compensate for this difference by optimizing the layout of cooling water channels and controlling the surface temperature gradient of the mold cavity to ensure uniform shrinkage of the product during the cooling and shaping stage. Dimensional deviation exceeding ± 0.3mm may affect splicing installation, especially in outdoor flooring and fence systems, where small errors accumulate as structural misalignment.
The corrosion resistance of molds is often overlooked, but it is crucial. Wood powder undergoes thermal degradation with plastics at high temperatures, which may release organic acids and trace chlorides (especially in PVC based systems), causing chemical corrosion to mold steel. To resist corrosion, high-end molds are made of molybdenum containing stainless steel or surface chrome plated to form a dense passivation film, effectively blocking the penetration of corrosive media, extending maintenance cycles, and reducing downtime costs.
The surface smoothness and texture replication ability directly determine the visual and tactile quality of WPC products. Modern WPC products pursue highly realistic appearances such as wood grain and stone grain, and the mold cavity needs to be replicated at the micrometer level through precision electrical discharge machining or laser engraving. The surface roughness Ra value needs to be controlled below 0.2 μ m, and any scratches or pores will form defects on the surface of the finished product, affecting its acceptance in the high-end market.
The service life and fatigue strength of molds are the core of economic evaluation. Under the condition of continuous operation for 8-12 hours per day, the mold needs to withstand millions of high-pressure injection or extrusion cycles. High stress areas such as cutting edges and channel edges are prone to fatigue cracking. Adopting WPC ® The mold with surface strengthening technology has a nearly 10 fold increase in anti chipping ability and a service life of 3-5 years, significantly reducing replacement frequency and downtime losses.
In addition, the performance of channel design directly affects the uniformity of melt flow. High fiber content leads to a significant increase in melt viscosity, and traditional flow channels are prone to insufficient filling, weld marks, or bubbles. The optimized flow channel needs to have a gradient cross-section, no dead corners structure, and an efficient exhaust system to ensure smooth and synchronized flow of the melt in the mold cavity, avoiding mechanical anisotropy caused by uneven flow.
In summary, wood plastic composite material molds are not simple molding tools, but precision systems that integrate material science, thermodynamics, rheology, and surface engineering. The performance of WPC products determines whether they can move from being "usable" to being "easy to use" and "durable", which is the underlying support for enterprises to achieve green manufacturing and high-end transformation.