What is the ruling on working in a factory that adds raw materials which reduce the quality of the product without informing the customer, and asks the employee to conceal this matter?

It is not permissible to conceal defects or to deceive customers, and there is no obedience to the factory owners in this regard. If you cannot remain in the job except by lying and concealing defects in the merchandise, then it is not permissible for you to stay in it.