issue for subcontractor

issue for subcontractor

sorry for just typing in English due to no Chinese input system in company computer, an prevasive case for manufactures or production industry is that they all have contractors and subcontractors in their materials supply line so as to fulfill the mutiple supplements, I wander how they control the subcontractors quality including the products or quality system, and how your customer treat such case except for communication or complain. I would appreciate it for any comment from you!