With the development of automobile manufacturing industry, the requirement of reducing energy consumption is higher and higher. Automobile parts are gradually transformed from iron castings to aluminum die castings, and products are developing in the direction of lightweight, high integration and high performance. More and more parts with complex structure and high compactness requirements are emerging.
In die casting production, it is required that the wall thickness of the parts should be as uniform as possible, so as to ensure the solidification at the same time as possible when the die casting is cooled. However, when the wall thickness of the parts varies greatly, there will be internal shrinkage at the thick wall of the casting. In order to eliminate the product leakage caused by shrinkage defects in die castings, local extrusion technology is generally used to solve the casting defects. The engine front cover is used to seal the oil passage transmission of the engine, which requires a very high internal compactness of the parts, and the internal oil pipes shall not have leakage and oil leakage.
By adopting the function of core pulling instead of extrusion and linkage core inserting spraying, the phenomenon of oil leakage in the oil passage caused by shrinkage in the actual production of engine front cover parts is solved.
Gating system and mold structure design
The casting is a sealed part with uneven wall thickness. The die structure is designed with two groups of core pulling. The oil cylinder is used to drive the slide block. One side feeding and multi branch feeding are used to advance horizontally, which is conducive to cavity filling and forming and reduces the casting porosity. The die casting machine is 22000kn, the casting pressure is 90Mpa, the punch diameter is 120mm, and the inner gate speed is 60m / s.
Internal quality of castings after processing
Through the leakage test after machining, it is found that there is leakage between the two oil passage holes, and the qualified rate of the product is 20%. After cutting the product, it is found that the large shrinkage between the oil passage holes is the main cause of the product leakage. The cut image is shown in Figure 2.
The technology of core pulling, extrusion and joint core inserting spraying combined with Robot Spraying signal driving is adopted to realize the local extrusion function of inclined slide block, which significantly improves the internal quality of castings, and the qualified rate reaches 99%.