QC is the operation technology and activities taken to make the products meet the quality requirements, it includes inspection, correction and feedback, such as QC inspection to find the defective products will be removed, and then the bad information feedback to the relevant departments to take improvement measures. Therefore, the control scope of QC is mainly within the factory, and its purpose is to prevent unqualified products from being put into, transferred to and from the factory, to ensure that the products meet the quality requirements and only qualified products can be delivered to customers.