[Retracted] An Improved Ant Colony Optimization Approach for Optimization of Process Planning

Table 4

Precedence constraints for Part 1.

Constraints	Descriptions	Hard or soft
Tool interactions	OP1 should be prior to OP2.	Hard
Datum interactions	OP6 should be prior to OP7.	Hard
	OP10 should be prior to OP11.
	OP13 should be prior to OP14.
Thin-wall interactions	OP9 should be prior to OP8.	Soft
	OP12 should be prior to OP10.
Material removal interactions	OP8 should be prior to OP9.	Soft
	OP10 should be prior to OP12.
	OP13 should be prior to OP14.
	OP3 should be prior to OP4.