What are the common demoulding problems when using Sow mold?
How to solve demoulding problems?
When using Sow mold, common demoulding problems include insufficient demoulding angle, mold surface adhesion, ejection mechanism failure, etc. The following are specific problems and solutions:
Insufficient demoulding slope: The demoulding slope should generally be between 0.5 and 2 degrees. If the slope is too small, the friction between the metal ingot and the mold will increase, making demoulding difficult. The solution is to reasonably design the demoulding slope according to the shape and size of the metal ingot when designing the mold to ensure that it is within the appropriate range. For metal ingots with complex shapes, the demoulding slope can be appropriately increased.
Adhesion on the mold surface: The rough surface, scratches or wear on the mold cavity surface will make the metal ingot easily adhere to the mold. When solving the problem, the mold surface needs to be polished to improve the surface finish. Surface treatment processes such as chrome plating can also be used to enhance the anti-adhesion of the mold surface. At the same time, repair the worn parts of the mold, reduce the gap between the inserts, and prevent the metal liquid from entering the gap to produce flash and affect demoulding.
Failure of the ejector mechanism: Insufficient ejection device stroke, unbalanced ejection or poor ejector action will cause the metal ingot to be unable to be demoulded. The effective ejection area of the ejector should be increased to ensure sufficient ejection stroke, and ensure that the ejector is evenly distributed so that the metal ingot is balanced. At the same time, check whether the sliding parts of the top plate are sticky. If so, lubricate or repair them to ensure smooth movement of the top plate.
Insufficient mold rigidity: Under the action of casting pressure, if the mold is not rigid enough, it will deform, causing the metal ingot to be clamped and difficult to demold. When designing the mold, ensure that it has sufficient rigidity and strength, which can be achieved by increasing the wall thickness of the mold, setting reinforcing ribs, etc. For molds that have insufficient rigidity, a frame can be inlaid on the outside of the mold to increase rigidity.
Poor exhaust: If the exhaust in the mold is not smooth, gas will remain and increase the demolding resistance. Exhaust grooves or exhaust holes need to be designed at appropriate locations of the mold to ensure that the gas can be discharged smoothly. The width and depth of the exhaust groove should be reasonable, generally 0.1-0.3mm in width and 0.5-1mm in depth.
Improper temperature control: Too high or too low mold temperature will affect the solidification and demolding of the metal ingot. If it is difficult to demold at the parting surface, the mold temperature can be appropriately increased and the cooling time can be shortened; if it is difficult to demold at the cavity surface, the mold temperature can be appropriately reduced or the cooling time can be increased. At the same time, to ensure that the temperature of each part of the mold is uniform, this can be achieved by optimizing the cooling system.
Improper use of release agent: Improper selection of release agent or insufficient amount cannot effectively reduce the friction between the metal ingot and the mold. It is necessary to select a suitable release agent based on factors such as metal type and casting temperature, and strictly control its amount. For example, for high-temperature casting, polytetrafluoroethylene release agents can be selected.
