The picture of the multi-function watch case is shown in Figure 1. The maximum size of the product is 54.82 mm x 36.40 mm x 17.47 mm, the average thickness of the plastic part is 1.30 mm, the material of the plastic part is ABS, the shrinkage rate is 1.005, and the quality of the plastic part is 7.5. Grams. The technical requirements of plastic parts are that there must be no defects such as peaks, dissatisfaction with injection molding, flow lines, pores, warpage deformation, silver streaks, cold materials, jet lines, and bubbles.
It can be seen from Figure 1 that the structure of the plastic part is a complex structural part. See the attached file for the 3D drawing of the plastic part. There are 3 side holes on the two side faces that are directly opposite at 3 o'clock and 9 o'clock respectively. The three side holes need the slider to pull the core, and there is an angle between each other. A square hole on the inside of the plastic part communicates with the oblique hole on the front. There is a watchband connection pinhole at each end of the plastic part, the diameter of this hole is ø1.92, and the core pulling length is 12 or more. These holes and grooves need to be designed with 11 slider cores. Due to the small space position, there is interference between the sliders, which brings difficulties to the mold design. The mold design drawing is shown in Figure 2.
The mold is a complex mold. The product size is small, but the sliders occupy a lot of space. Therefore, the mold design cavity ranks 1 out 1. In order to facilitate the design of the front mold oblique slider, the mold base uses the standard mold base EDI3335; The shape of the part is all the appearance surface. Therefore, the gate is selected inside the circumference of the plastic part. After the molten plastic enters the parting surface from the sprue bushing main runner, it is divided into 4 channels, latent gates, and 4 points of glue.
The two pits at both ends of the plastic part need to be designed with front mold sliders, which are driven by 25° inclined guide posts. The square hole on the inner side of the plastic part adopts the form of a sliding block in the rear mold, and the oblique guide post is fixed on the back mold backing plate. There are 3 side holes on the two sides facing 3 o'clock and 9 o'clock respectively, and a small sliding block of the rear mold is designed, all of which are driven by inclined guide posts. There is a watchband connection pinhole at each end of the plastic part. The two holes also need to be designed with the back mold slider. Due to the small space position, the two-hole slider is designed at the bottom of the slider with the side hole cored, and the position is staggered. . See the 3D drawing of the mold design.
The inner sliding block adopts the rear mold floating template to realize the core pulling, and this sliding block and the front mold oblique sliding block need to touch through. Therefore, a first reset device is designed. This first reset device is the first resetting sleeve resetting after the straight rod of the front mold hits the mold, which has the advantages of simple structure and small mold space occupation. This kind of first reset mechanism has standard components to buy. It is widely used in European and American molds.
Both the front and back molds of the mold are designed for direct water transport to ensure the stable progress of the injection molding process.
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