1.Runner 2. Runner cup 3. Riser 4, 5, 6. Ingate 7. Lap sheet 8. Sprue 9. Annular runner
The original process scheme is shown in Fig. 1, using disa line vertical molding machine, designed as a stepped gating system, without sand core. The gating system consists of gate cup, riser, runner, sprue and ring runner, which are respectively located in the corresponding positions of positive and negative platens. The gating system has the advantages of smooth mold filling and high feeding efficiency of riser. However, due to the thin edge structure of the casting where the riser is placed, the liquid metal in the riser can not be fed in sequence, so the internal shrinkage of the casting is serious, as shown in Figure 2.
The improved casting process scheme is shown in Fig. 3. The reason for the internal shrinkage of the casting caused by the original process is that the riser can not transfer enough liquid metal through the thin wall position of the casting to the thick wall position to realize effective sequential feeding, resulting in the blocking of the feeding channel. Therefore, the feeding channel is artificially increased by adding a wedge block on the die (corresponding position of the casting), The bridge between riser neck and casting shrinkage porosity is realized to keep feeding channel unobstructed. With the improved casting process, the liquid metal in the riser can be directly supplied to the feeding position through the wedge block (plus the thickness of the original casting).
Through the simulation analysis, there is no shrinkage porosity and shrinkage cavity in the casting, and the mold filling is stable, as shown in Figure 4. Through small batch test and mass production, after sand and shot blasting, X-ray inspection, destructive cutting and coloring inspection were used to verify that the internal shrinkage defects of castings have been completely solved (see Fig. 5 and Fig. 6), and there is no casting dynamic balance out of tolerance. The remaining wedges on the machined surface of the casting can be removed by turning when machining the friction surface of the casting, without additional machining cost. At present, the clutch flywheel has been put into mass casting production with stable quality.
