In the design process of laboratory instrument die castings, optimizing wall thickness uniformity is a key step in reducing the risk of thermal stress concentration in the mold. Uneven wall thickness leads to significant differences in the flow rate of molten metal during filling, with thin-walled areas cooling too quickly while thick-walled areas remain continuously heated, resulting in excessive local temperature gradients in the mold and causing thermal stress concentration. This stress concentration accelerates thermal fatigue on the mold cavity surface, causing cracking or fissures, directly affecting the dimensional accuracy and surface quality of laboratory instrument die castings, and even leading to premature mold failure. Therefore, achieving wall thickness uniformity through structural optimization is an important means to improve mold life and the reliability of laboratory instrument die castings.
The design phase must adhere to the principle of "uniform wall thickness" and avoid abrupt cross-sections. If thickness differences are necessary due to functional requirements, gradual transition structures (such as elliptical arcs or large-curvature fillets) should replace right-angle turns to reduce molten metal flow resistance and temperature fluctuations. For example, at the connection between the reinforcing ribs and the main body of the spectrometer housing, a rounded transition can disperse thermal stress and prevent localized overheating. Simultaneously, adding process ribs can balance structural strength and reduce stress concentration caused by differences in wall thickness. Process ribs not only improve the rigidity of laboratory instrument die castings but also act as heat conduction media, promoting uniform mold temperature.
Mold design needs to be optimized in conjunction with the wall thickness distribution of laboratory instrument die castings. For structures where thin and thick walls coexist in spectrometer laboratory instrument die castings, the filling speed of molten metal can be balanced by adjusting the gating system layout (e.g., using multiple genates or stepped runners), preventing premature solidification of thin-walled areas or continuous heating of thick-walled areas. Furthermore, the mold cavity surface can be locally strengthened (e.g., nitriding or shot peening) to improve its resistance to thermal fatigue and delay crack propagation caused by thermal stress concentration. For complex curved surface laboratory instrument die castings, the molten metal filling process needs to be simulated using mold flow analysis software to identify potential thermal stress concentration areas and optimize the wall thickness design accordingly.
Material selection is equally important in reducing the risk of thermal stress concentration. Spectrometer laboratory instrument die castings often use aluminum or zinc alloys, whose coefficients of thermal expansion and thermal conductivity directly affect the temperature field distribution of the mold. High thermal conductivity materials can accelerate heat transfer and reduce localized overheating of the mold, but require a well-designed cooling system to avoid excessive overall temperature rise. Mold materials must possess high resistance to thermal fatigue (e.g., H13 steel) and undergo pretreatment (e.g., vacuum quenching) to eliminate machining stress and reduce deformation caused by stress release during service.
Optimizing the machining process can further reduce the risk of thermal stress concentration. Cutting stress generated by final machining processes such as turning, milling, and planing can be eliminated through intermediate annealing; the white layer on the surface after EDM needs to be polished off and tempered to prevent crack initiation due to a brittle layer. During mold assembly, it is essential to ensure tight contact between inserts and the mold body to prevent localized stress concentration caused by point or line contact. Furthermore, periodic stress-relief tempering of the mold (e.g., the first tempering at 30% of its service life) can significantly extend its service life.
Temperature control during the production process is crucial for reducing thermal stress concentration. The mold needs to be preheated to a suitable temperature (usually 150-200℃) to reduce the chilling effect during molten metal filling and avoid thermal stress concentration due to excessive temperature gradients. Simultaneously, a cooling temperature control system is required to maintain a stable mold operating temperature and prevent mold sticking or malfunction of moving parts due to localized overheating. For thin-walled areas in laboratory instrument die castings, localized cooling enhancement (such as increasing cooling channel density) can accelerate heat dissipation and balance the overall temperature field.
Optimization of the wall thickness uniformity of laboratory instrument die castings needs to be integrated throughout the entire process of design, materials, processing, and production. Through gradual structural transitions, collaborative design of the gating system, material heat treatment enhancement, stress relief during processing, and precise temperature control, the risk of thermal stress concentration in the mold can be significantly reduced, improving the quality and lifespan of laboratory instrument die castings and providing a reliable guarantee for the high precision and high stability requirements of spectrometers.
