In order to reduce the sand hole defects, we should start from the source of sand, inspection, removal and cavity protection, and mainly take the following preventive measures.
(1) The sand core partition between camshaft cavity core and waist circle hole core is improved to eliminate the phenomenon of local sharp angle sand. At the same time, the fillet is made around the waist circle hole core to prevent the existence of weak sand.
(2) A pressure ring (as shown in Figure 1) is made around the V-shaped core square window and the edge where the upper side plate cores are in contact with each other to prevent the sand core from being damaged, and a sand collecting pit (as shown in Figure 1) is made around the core seat of the V-shaped core and the front and rear end cores to gather sand and prevent the broken sand from falling into the mold cavity.
(3) The front-end core head is improved to check whether there is broken sand falling into the bottom of the mold cavity. At the same time, the structure of the sand blocking core in the back-end bottom box is improved to facilitate the blowing of broken sand.
(4) Control the surface quality of the sand core before core setting. Pay attention to the surface quality of the sand core before lowering the core. There shall be no floating sand, sundries, sand laps, etc. and there shall be no coating defects. Clean the body and lower it into the mold cavity.
(5) Plastic cloth shall be used to cover the mold cavity during the rest of core laying and from the completion of core laying to the completion of sand filling before box closing, so as to prevent external broken sand from falling in.
(6) Make special air duct to remove the broken sand found in the inspection.
After taking the above measures, more than 600 cylinder blocks have been produced, of which only 2 have sand hole defects, and the rejection rate is less than 0.3%.
(1) Reasonable sand core partition can eliminate the existence of sharp angle sand, avoid the occurrence of collapse phenomenon, so as to avoid the occurrence of sand hole defects.
(2) The application of anti pressure ring and sand collecting pit can prevent sand rubbing during core setting and prevent broken sand from falling into the mold cavity.
(3) Covering the cavity with plastic cloth before closing can prevent the external sand from falling into the cavity, so as to prevent the occurrence of sand hole defects.