The process of removing precision castings from molds, removing excess parts other than the main body, and polishing and precision machining the inner and outer surfaces of the castings. It is divided into dry method and wet method. Dry cleaning is the use of mechanical equipment to clean castings. The equipment used is simple, with high production efficiency and strong adaptability to different types of castings. It has the advantages of effectively removing the core and cleaning the surface. The disadvantages are high dust, loud noise, and environmental pollution. Wet cleaning does not have dust, but due to the use of water as a medium, the surface of castings is prone to rusting. During operation, a large amount of sewage and sand containing cement are generated, which brings problems such as sand and water regeneration and sludge treatment.
The commonly used dry and wet cleaning methods for precision castings in production include:
Drum cleaning. Place precision castings and star shaped iron in a circular drum. When the rolling mill rotates, the sand particles inside and outside the casting are removed by the impact and friction between the waste sand particles, star iron, and other components of the casting. The surface of the casting is polished, and burrs and burrs can also be partially removed. This equipment is suitable for cleaning small and medium-sized castings with simple shapes and larger wall thickness.
Shot blasting. Utilize the impact force of high-speed steel shot and abrasive flow to remove sand sticking on the core and polish the surface of precision castings. In addition, commonly used shot blasting equipment includes shot blasting tables and shot blasting chambers. The shot blasting machine used for continuous production includes chain plate shot blasting roller, continuous shot blasting table, suspended continuous production shot blasting room, etc. This type of equipment has high operating and maintenance costs.
Hydraulic sand cleaning. High pressure water is sprayed from the nozzle to the processed casting through a pipeline, relying on the kinetic energy and scouring effect of the water flow to remove sand adhering to the core and casting. Hydraulic sand cleaning is usually equipped with an open sand cleaning chamber composed of steel sections and steel plates, with a turntable at the bottom. The spray gun is installed on the side wall and can move and rotate up and down, so that high-pressure water can be sprayed onto any part except the bottom surface of the casting. Sometimes, in order to improve the efficiency of removing sand sticking on the surface of precision castings, abrasives such as quartz sand are introduced at appropriate positions in the spray gun to obtain high-speed water and sand flow. This method is generally referred to as water sand cleaning.
Water explosion to clear sand. After casting, the casting is cooled to the specified temperature and immediately immersed in the tank. Water seeps into the casting through all gaps and comes into contact with high-temperature metals, rapidly vaporizing and exploding. The sand attached to the inside and outside of the casting can basically be removed by shock waves. The water spray sandblasting cleaning method has the advantages of short operation time and high efficiency, and has been widely used in steel casting workshops. Generally used for processing precision castings with carbon content below 0.35%.
