Design of injection mold for facial cleanser The choice of parting surface and the determination of the number of cavities. To ensure that the plastic parts quality and avoid affecting the quality of appearance; for that part of the opening and closing of the smooth and cooperation. All the products into the parting surface are on the same side of the, to ensure that the plastic parts of the coaxial degree. In order to make the mold and injection machine production capacity matching, improve productivity and economy, and to ensure the accuracy of parts, using a multi cavity mode. Determine the number of cavity according to the maximum injection volume of injection machine, the formula: