I agree here. The suppliers you want to be dealing with are well-established and are known for their high quality materials. In fact build a relationship with these suppliers and do not burden the planning phase. Additionally, a good relationship might help you get your materials faster and at better prices and latest qualities. A good relationship is achieved through loyalty, trust in your business dealings (you pay your bills on time, do not use their materials for illegal purposes, are fair, etc.), and involvement, that is, let them understand your product and company. Also being demanding is important as well to establish you can not be double crossed, cheated, or swindled.