There are many classification methods of injection molds, according to different division basis, usually as follows several categories.
(1) According to the category of plastic materials, it is divided into thermoplastic injection mold and thermosetting plastic injection mold.
(2) According to the number of mold cavities, it is divided into single-cavity injection mold and multi-cavity injection mold.
(3) According to the mold installation method, it is divided into mobile injection mold and fixed injection mold.
(4) According to the type of injection molding machine, it is divided into horizontal injection mold, vertical injection mold and right-angle injection mold.
(5) According to the dimensional accuracy of plastic parts, it is divided into general injection mold and precision injection mold.
(6) According to the mold gating system, it is divided into cold runner mold, adiabatic runner mold, hot runner mold and warm runner mold.
(7) According to the overall structural characteristics of the injection mold, it can be divided into the following types.
a. Single parting surface injection mold (two-plate injection mold)
The single-parting surface injection mold is also called the double-plate injection mold. It is the simplest type of injection mold. One part of the cavity is on the movable mold, and the other part is on the fixed mold. Single parting surface injection mold for horizontal or vertical injection molding machine, the main flow channel is set on the side of the fixed mold, the branch channel is set on the parting surface, after the mold is opened, the part and the flow channel aggregate are left on the side of the moving mold. side. There is a push-out device on the movable mold to push out the workpiece and runner aggregate (material handle).
b. Double parting surface injection mold (three-plate injection mold)
The double parting surface injection mold refers specifically to the pouring system condensate and parts that are taken out from different parting surfaces, also known as the three-plate injection mold. Compared with the single parting surface mold, a movable middle plate (also known as gate plate) is added, which is used for single or multi-cavity molds with pin-point gate feeding. When the mold is opened, the middle plate is separated from the fixed formwork at a certain distance, so as to take out the pouring system condensate between the two plates.
c. Injection mold with movable molded parts
Due to the special requirements of plastic parts, movable forming parts are set in the mold, such as movable punches, movable dies, movable forming rods, movable forming inserts, etc., so that it is convenient to take out the parts when the mold is opened.
d. Injection mold with lateral parting core pulling
When the plastic part has a side hole or a side concave, a side parting core-pulling mechanism such as an inclined guide post or an inclined slider is provided in the automatically operated mold. When the mold is opened, the mold opening force is used to drive the side core to move laterally to separate it from the workpiece. There are also hydraulic cylinders or pneumatic cylinders installed on the mold to drive side cores for horizontal parting and core pulling.
e. Automatic unthreading injection mold
When the plastic parts with internal thread or external thread are required to be automatically demoulded, a rotatable thread core or ring is provided on the mold. Use the rotary motion or reciprocating motion of the machine tool, or install special prime movers (such as electric motors, hydraulic motors, etc.) and transmission devices to drive the threaded core or ring to rotate to make the workpiece come out.
f. Injection mold with push-out device in fixed mold
Generally, after the injection mold is opened, the parts are left on the side of the moving mold, so the ejection device is also set on the side of the moving mold. However, sometimes due to the special requirements or shape restrictions of the workpiece, the workpiece is left on the fixed mold (or may be left on the fixed mold), and a push-out device is installed on one side of the fixed mold. When the mold is opened, the push-out device is driven by the pull plate or the chain to push out the workpiece.
g. No runner injection mold
Runnerless injection molds include hot runner or insulated runner injection molds, which use the method of heating or insulating the runner (the outer layer of condensed plastic in the runner insulates the molten plastic in the center of the runner) to keep the flow from the injection nozzle to the center of the runner. The plastic between the cavity gates is in a molten state. After each injection, it is only necessary to take out the workpiece without returning material from the pouring system, which greatly improves labor productivity and ensures the transmission of pressure in the runner. Such molds are easy to achieve fully automatic operation.
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