In general, the technical standards for gravity casting cylinder block blanks often require the hammering method to be used, and the content of impurities in the dropped inner cavity does not exceed a certain value as the acceptance standard for cleanliness. Therefore, we can often obtain satisfactory results by using the traditional sand falling, core striking and shot peening processes. However, the “black ash” attached to the inner cavity surface by this process (generally caused by the peeling off of the oxide skin formed after the burning of the paint), especially in the narrow and deep parts of the inner cavity of the gravity casting or the parts with few sand holes, cannot be effectively removed. It has become the main reason for the frequent “blackening” and “discoloration” of coolant in the market in recent years.
In the R&D process of Cummins 2.7 CTI cylinder block, in view of the above hidden dangers, through a series of production practices and effect verification, we set the cleaning process as follows: vibrating sand falling → primary core striking → secondary core striking → four side grinding → rough polishing of blank → fine polishing of blank (adding fixed-point shot blasting program) → hand-held sand blasting → air blowing cleaning → manual grinding → manual inspection (visual inspection+endoscope), and finally obtained the internal cavity cleaning Bright gravity casting blank.