What are the different types of ejectors for plastic injection mold?

When a small round product or a product has a boss column with a depth of more than 10.00mm, the use of a sleeve pin ejector facilitates product demoulding and increases the exhaust effect during injection molding production, and reduces the discharge during mold processing, saving processing costs.

Therefore, almost every set of molds with boss columns and products that meet the position requirements will use a sleeve pin to assist product demoulding.

The ejector pin can be replaced by the round ejector pin described above, or a strip ejector pin can be used according to the strength requirements. The ejector tube has a separate model for ordering, and is also divided into a straight-through ejector tube and a stepped ejector tube, but most of them use a straight ejector tube.

In the past, when designing custom plastic injection molds, taps were often used to fix the ejector tube. During molding, it was found that the ejector tube fixed by taps was easy to loosen and break. The product was not removed from the mold for a long time and was easy to burr. Therefore, most of the molds designed now use small pressure plates to fix the ejector tube.

5. About the “foolproofing” of ejector pins

Under normal circumstances, when the position of the push rod is not a regular plane, if it rotates, it will cause mold pressing, glue position difference, etc., so the push rod hanging table will be pinned (pinning is not commonly used, compared with “edge cutting”, it is difficult to do, and the processing requirements will be higher).

For some products, the arrangement position of the ejector pins and the ejector pins is small, and the hanging table interference will use three-side positioning or right-angle edge positioning. According to the mold requirements of the molding manufacturer, the ejector pin will choose to cut the edge or cut the small edge, but it must be coordinated with the ejector pin panel, and no excessive gap can be generated.

For products with eight cavities in one mold/four cavities in one mold, the product shape is the same and the ejector pin position is the same. If the ejector pins are mixed up, the clearance after assembly will be different. In order to prevent the fitter from installing the ejector pin incorrectly during assembly and grinding, engraving is the easiest and most convenient way, but it cannot be satisfied with installing the ejector pin incorrectly. Therefore, different ways of edge cutting will be performed on the ejector pins of the same shape (as shown in the figure above).

6. About ejector pin “clearance”

Under general requirements, the sealing distance of the ejector pin is 10.00-15.00mm. If the fitting distance is too long, the resistance of the ejector pin when ejecting the product will increase. A small fitting position is not conducive to the sealing of the product, and it is easy to run burrs during long-term molding.

For products with middle-filled glue, the ejector pin under the main channel will directly bear the injection pressure, so the clearance distance should be 5-10mm longer than the ejector pin at the glue position to prevent mold wear and ejector pin leakage. In addition to the sealing position, the clearance distance on other templates is generally 0.5mm on one side for clearance. For products with high precision requirements, the clearance distance on one side is 0.25mm.