The casting structure of the electro-hydraulic valve casting is complex (as shown in Figure 1), with two slender and curved independent oil passages, each with a length diameter ratio of 20 (as shown in Figure 2). When casting these two oil passages, the sand core is made by the coated sand machine. In the core making process, due to the structural characteristics, the sand core is difficult to form. After several process improvements, the sand core making process with double sand nozzles and exhaust holes and exhaust grooves at multiple key positions is finally designed (as shown in Figure 3).
Qualified batch sand cores were produced by using coated sand with high strength, low gas generation and good fluidity, and selecting reasonable sand shooting pressure and other parameters.
In order to ensure the dimensional accuracy of the casting oil duct, the accurate core assembly process is adopted, and the assembled sand core is shown in Figure 4.