고정도 고속 Groove Die Set 개발

Even though very high demand of metal mold press and its related manufacturing industries throughout world, 70 - 80% of the metal mold press is manufactured at German, Japan and Korea as a high value-added industry, and bearings and die sets for the high-speed press processing are being developed at German and Japan. Current high-accuracy and high-speed die sets of metal mold press creates scratches at the surface of guide posts, steel balls and bushes due to vertical movement of balls with point-contacts between inner surface of bushes and guide post, and those scratches reduces the metal mold life by low accuracy of die sets. This research designed and developed a groove die set which improves life of die sets by eliminating the point-contacts of ball with guide posts. The guide post consisted of a steel-ball retainer, a steel-ball retainer stopper, a guide bush, a guide pin, a snap ring, and a spring. The steel-ball retainer has 72 holes with 8 columns of 9 holes in each column. The inner surface of guide bush was grinded (surface roughness: Ra = 0.2, accuracy: +0 ~ -0.002) after NC turning and heat treatment. Also, a line of small intermediate pocket was processed inside of guide bushing for lubrication and elimination of foreign materials. Guide grooves of steel balls were processed using a wire EDM (Electrical Discharge Machining) after heat treatment. With such a design of the guide post stated above, loads against steel balls could be dispersed greatly by the line contacts through a guide groove between guide post and bush, and the life of guide post could be expanded to semi-permanently.