In the core retreat production process, the hollow portion of the mold is first closed and later reopened using a sliding core or slider within the cycle. When producing a part with two components, the first injection molding stage first injects the prefabricated component and then opens the second hollow part in the same cavity (for example, by dragging the sliding core). Finally, the second component is injection molded into the prefabricated part, so that the complete part is produced and the final part is taken out of the mold. When injection molding, you can also rotate the template to open the cavity and then inject the second component into the first component.
If there are two or more components, composite injection molding can be used, but as the number of components increases, the complexity of the mold increases dramatically. Since all the required actions can be done in the mold, no external machine parts are required. However, the machine must have a sufficient number of programmable cores to control the slider.
If only one mold is needed to complete the production, and there is no need to open the mold in the middle, and there is no need to transfer the prefabricated parts, the composite injection molding has a significant advantage. However, compared to multi-component injection molding, this production method is carried out in a strict phase sequence rather than in parallel.