(1) Straight ejector pin should be arranged so that ejection force is as balanced as possible. Demolding force required for complex structures is large, and number of ejectors should be increased accordingly.
(2) Ejector pin should be set in effective parts, such as bone, column, steps, metal inserts, and some thick structural parts. Ejector pin on both sides of bone and column should be arranged as symmetrically as possible. Distance between ejector pin and bone, column is generally D = 1.5mm, as shown in Figure 5.5.8. In addition, center line of ejector pin on both sides of column should be as far as possible to pass through center of column.
(3) Avoid setting up ejector pins across steps or on inclined surfaces. Top surface of ejector pin should be as smooth as possible, and ejector pin should be layout at structural part where part is better stressed.
(4) A rectangular E.P. should be used when plastic parts is deeper (depth ≥20mm) or it is difficult to arrange a round needle. When a rectangular E.P. is required, rectangular E.P. should be inserted as much as possible to facilitate processing. Figure 5.5.10
(5) Avoid sharp steel and thin steel, especially top surface of ejector pin should not touch front mold surface. Figure 5.5.11
(6) Layout of ejector pin should consider side distance between ejector pins and water conveyance channel to avoid affecting processing and water leakage of water conveyance channel.
(7) Ejector function of ejector is taken into consideration. In order to exhaust ejector, ejector should be arranged at the place where vacuum is easy to form. For example, at larger plane of cavity, although rubber packing force is small, it is easy to form a vacuum, which results in an increased demolding force.
(8) For plastic parts with appearance requirements, ejector pin cannot be arranged on appearance surface, and other ejection methods shall be used.
(9) For transparent plastic parts, ejector pin cannot be placed on part that needs to transmit light.