Толщина стенок деталей литья под давлением должна быть одинаковой
литьё алюминия под давлениемThere are no hard and fast rules governing die casting parts wall thickness and consistency. Inherent in the process is a wall section that possesses a dense fine-grained skin, 0.015-0.020 in. thick (0.4-0.5 mm). The material between the surface skins tends to be less dense and large grained as a result of a longer solidification time. This is where defects tend to congregate. Die casters have demonstrated the capability of casting 0.06-0.07 in. (1.5-1.8 mm) thick aluminum walls over large surface areas. It is feasible to cast small areas as low as 0.04 in. (1 mm). Zinc alloys flow more readily, and can be cast to wall thickness as low as 0.03 in. (.75 mm) Magnesium alloys can be cast to wall thickness 0.035-0.045 in. (.89-1.14 mm) Wall sections should be as uniform as possible. It is difficult to achieve uniform and rapid solidification of the alloy if the heat load varies from one location to another in the die. Thinner walls contribute a lesser heat load than heavier walls and will have a longer die life. Intersections of walls, ribs and gussets should blend with transitions and generous radii Generous radii, outside corners, and transitions promote metal flow and internal integrity. Radii and fillets also enhance structural integrity by reducing stress concentrations in the casting. Additionally, fillets reduce heat concentration in both the die and castings. Hot spots that result from sharp corners promote shrinkage voids in the casting. These hot spots also reduce die life at sharp corners in the die cavity steel. Standard draft should be specified Draft is highly desirable on surfaces parallel to the direction of die draw because it facilitates ejection by allowing the casting to release easily from the die surfaces. The NADCA Product Standards recommendations for minimum draft should be specified. Sharp corners should be eliminated or minimized If sharp corners are required, they readily are accommodated at parting lines and at the junctions of die components. Sharp corners should be broken with radii or chamfers. Undercuts should be avoided Undercuts should be avoided because they may require machining operations or additional die components, such as retractable core slides. Slides increase the cost of die fabrication and maintenance. They can also add to cycle time and manufacturing problems if they flash. If possible, the component should be redesigned to eliminate undercuts.
