Injection molds are composed of many steel plates and various parts, generally including molding devices, positioning devices, cooling systems, constant temperature systems, runner systems, etc. According to the overall structural characteristics of injection molds, they can be divided into the following types:
Single-parting surface injection mold
Single-parting surface injection mold, also known as double plate injection mold, is the simplest type of injection mold. A part of the mold cavity is on the moving mold, and the other part is on the fixed mold. The main runner of the horizontal or vertical injection molding machine is set on the fixed mold side, and the sub-runner is set on the parting surface. After opening the mold, the product and the runner material (sprue) are left on the moving mold side. The moving mold is equipped with an ejection device, which is used to eject the product and the runner material.
Double-parting surface injection mold
Double-parting surface injection mold refers to the mold where the pouring system material and the product are taken out from different parting surfaces, also known as a three-plate injection mold. Compared with the single-parting surface mold, an additional movable intermediate plate (also known as a sprue plate) is added, which is used for the single or multi-cavity mold that requires point gate feeding. When opening the mold, the intermediate plate is separated from the fixed mold plate at a certain distance, so that the pouring system material between these two plates can be removed.
Injection molds with movable molding parts
Due to the special requirements of plastic products, molding parts that can be moved, such as movable cores, movable inserts, movable molding rods, and movable molding blocks, are set in the mold to facilitate the removal of products during mold opening.
Injection mold with lateral parting and core pulling mechanism
When the plastic product has a side hole or side depression, there is a lateral parting and core pulling mechanism such as oblique guide columns or oblique slide blocks in the automatic operation mold. When opening the mold, the core pulling mechanism is driven by the opening force to move laterally, so that it can be separated from the product. Hydraulic cylinders or pneumatic cylinders are also installed on the mold to drive the core pulling mechanism for lateral parting and core pulling.
Automatic unscrewing injection mold
For plastic products with internal or external threads that require automatic demolding, the injection mold is equipped with a rotatable screw core or ring core. The screw core or ring core is driven to rotate by the rotation or reciprocating movement of the machine tool, or by using a specialized power device (such as an electric motor, a hydraulic motor, etc.) and transmission device to drive it to rotate, so that the product can be demolded.
Injection mold with fixed plate ejection device
Generally, after the injection mold is opened, the product is left on the moving mold, so the ejection device is also set on the moving mold side. However, sometimes due to the special requirements or shape restrictions of the product, the product may be left on the fixed mold (or it is possible to be left on the fixed mold), so the ejection device is set on the fixed mold side. When opening the mold, the ejection device is driven by a pull plate or chain to eject the product.
Injection mold without runner
Runnerless injection molds include hot runner or insulated runner injection molds. They use methods such as heating or insulation (the outer layer of the plastic condensed in the runner acts as insulation to the melting plastic in the center of the runner) to keep the plastic between the injection nozzle and the cavity gate in a molten state. After each injection, only the product needs to be removed without any pouring system runner material, which greatly improves labor productivity, and also ensures the transmission of pressure in the runner. Such molds are easy to achieve fully automatic operation.
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