The production of ductile iron piston rings of YpR company adopts double piece casting process, and there are two kinds of high-pressure molding machines. One is the introduction of four automatic high-pressure molding production lines from Gertz company, the other is the production line composed of two high-pressure molding machines from American B.P company. In addition, eight self-made high-pressure molding machines and production lines equivalent to Gertz type are used in the new foundry workshop.
The difference between the two molding machines lies in that the square sand box used by Gertz molding machine is 3 95×3 45x 35 m high, and the round sand box used by B.P company in the United States is Φ 4 50x Φ 3 5 mm。
B. P Company produced only two high-pressure molding machines using round sand boxes for YpR. Later, it was merged by Simpson company in 197 before new users bought them.