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Design of injection mold for drinking bottle cap with internal thread

1 Drinking water bottle cap structure

The structure of the cap of a drinking bottle for infants is shown in Figure 1. The height is about 75 mm. There are 2 handles on the outer surface. The maximum distance between the 2 handles is 127 mm. The main part of the bottle cap is a circular structure, with an outer circle. The diameter is φ66 mm, the inner surface has 2 turns of internal threads, the internal thread specification is M58 mm, the length of the inner cylindrical surface of the bottle cap is 14 mm, and the length of the internal thread is 6 mm. The material of the plastic part is ABS. Since the ABS material is relatively hard, the internal thread of the bottle cap must be demoulded in a rotating manner and cannot be forced to be demoulded.

2 Mold design

The mold adopts a 1-mold, 2-cavity, three-plate mold structure. The external structure of the plastic part is formed by the collision of two Huff sliders, and the internal threads of the plastic part are formed by a threaded core, as shown in Figure 2. Since the demoulding distance of the Huff slider is small, it is driven by the inclined guide post. The inner hole of the plastic part is formed using a structure in which the fixed mold core and the movable mold core collide.

2.1 Core structure
The structure of the plastic part determines that the internal thread must be demoulded first, and then the two Huff sliders are separated, and the gate is set on the inner cylindrical surface of the plastic part to be formed. The core is divided into two layers: inner and outer. The inner core is provided with runners, gates, push rods and pull rods. The outer core is provided with a structure for the internal thread of the molded plastic part.

2.2 Gating system
Set up a straight flow channel for each plastic part to be formed, align the point gate with the parting surface where the fixed model core and the movable model core collide with each other in the inner hole of the molded plastic part, and then open a flow channel on the end face of the movable model core, and then The material is fed in the form of ear protection gates, and there are 2 gates on each plastic part to be formed, as shown in Figure 4. This kind of gate has two advantages: ① The gate is relatively hidden and does not affect the appearance of the molded plastic parts; ② The gate condensate can be automatically trimmed. In order to avoid welding marks on the molded plastic parts, both ends of the flow channel on the end face of the dynamic mold core are slightly extended to act as cold material pockets.

2.3 Transmission mechanism
In order to enable the threaded core to rotate automatically, a transmission mechanism consisting of a hydraulic cylinder, a rack and pinion, a driven gear, a threaded nut and a tapered roller bearing is designed, as shown in Figure 5. In order to facilitate the adjustment of the position of the threaded core when assembling the mold, a gear adjustment device is provided in the threaded nut mechanism. A tapered roller bearing is installed on the bottom surface of the driving gear, and the two cores are driven by the same driving gear. When the thread core rotates, driven by the thread nut mechanism, the thread core also translates along the axis direction at the same time, so that the internal thread of the molded plastic part is demoulded. In order to extend the service life of the threaded core and prevent its wear, a copper sleeve is installed on the outer cylindrical surface of the threaded core. The outer core consists of three parts. The thread structure of the molded plastic part is set at the top, the driven gear is set in the middle, and the thread in the thread nut mechanism is set at the tail. The nut in the thread nut mechanism is fixed on the template of the mold base. superior.

2.4 Launch organization
Since the internal thread demoulding mechanism demolds before the mold is opened, after the internal thread is demoulded, the plastic part still adheres to the core and needs to be pushed out with a push rod. Six push rods are set on the inner core. The structure of the push-out mechanism is shown in Figure 6.

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