Uncolored PU samples can be used to test the optimal spray thickness, drying time and curing conditions of the coating. By testing different concentrations of primer in different areas of the sample, the bonding effect with PU material was observed to determine the most suitable coating formula. The design, production and quality inspection teams can communicate directly around the PU sample: the designer can point out the deviation between the sample and the drawing, the production personnel can feedback the impact of the molding process on the subsequent coloring, and the quality inspection department can clarify the appearance acceptance standards.