This is a door and window lock assembly for a bus, which is produced using investment casting technology and then black powder coating. This product is produced using investment casting with high precision and does not require further machining. After the product is assembled, it moves very smoothly and has little deformation. Later, customers were quite satisfied with the strength and quality of the product. Therefore, for some metal parts, especially carbon steel parts, alloy steel parts or stainless steel parts, if the structure is relatively complex, investment casting can be given priority.