Research And Development Of High Vacuum Die Casting Plunger Tip And Its Cooling And Lubrication Teachnology

Lubrication and cooling of plunger tip is the important process of die casting, and thedegree of cavity vacuum in the high vacuum die casting is directly related with the sealingof plunger tip and shot sleeve. At present, oil-based and dry pellets lubricants are mostcommonly used in lubrication of plunger tip, but they may produce large amounts ofsmoke, being harmful to the quality of castings and polluting the environment.Water-based lubricants are used in the lubrication of plunger tip, and as the water-basedlubricants do not contain large amounts of oil, they cannot produce smoke. As a result,thegas content and the porosity in castings are reduced and the workshop environment isimproved. In the paper, water-based lubrication equipment for the plunger tip, newplunger tip and rod which has the funcation of plunger tip lubrication, sealing, cooling andrapid replacement, are developed.Through the research of basic principle of water-based lubrication for plunger tip, theequipment of water-based lubrication which consists of lubricant dilution function,blow-dry function and spraying control function is designed. The dilution function is usedfor diluting the water-based lubricant. Then those diluted water-based lubricant is sprayedin shot sleeve with the transportation of pipe line and plunger rod. When the spraying iscompleted, the blow-dry function will dry out the moisture of water-based lubricant,leaving behind a layer of lubricant coated in the inside surface of sleeve to lubricateplunger tip and shot sleeve.In this paper, the new plunger tip and plunger rod, etc which match the plunger tipwater-based lubrication equipment are fabricated. There is lubricant pipe in the newplunger rod to realize spraying water-based lubricant. Seal ring, optimized water coolingstructure, rapid replacement structure etc, are proposed. Seal ring is used for sealingplunger tip and shot sleeve to achieve high vacuum die casting. Optimized water coolingstructure can be applied to improve the cooling effect. New plunger tip with rapidreplacement structure was designed to allow for easy removal and replacement,minimizing production downtime and enhancing die casting productivity.The die casting experiments are conducted by using the plunger tip water-basedlubrication equipment, and the new plunger tip and plunger rod. The castings producedduring experiment are inspected by X-ray, and the inspection result is compared with thecastings that their plunger tips are lubricated by oil. The results show that the porosity ofthe castings produced during experiment is less, so lubricating plunger tip by water-based lubricant instead of oil, it helps to reduce the gas content of castings.The temperature of new and traditional plunger tips is measured during ourexperiment. When the die opens and the castings are ejected, at this point the averagetemperature of the new plunger tips is6.4℃higher than the traditional plunger tips. So thenew plunge tips do not show more effective cooling property than traditional plunger tips,but the temperature of new plunger tips is more stable. When the plunger tips come back,the temperature of new plunger tips increased by11.1℃, however the traditional plungertips is27.3℃.The temperature increase of new plunger tips is lower than traditionalplunger tips, because the water-based lubricant sprayed during the plunger tips going backhas the effect of cooling plunger tip and shot sleeve.