Pulsator antenna tube product is shown in Figure 1. Maximum external dimension of product is 249.37 mm * ø40.88 mm mm, average thickness of plastic part is 2.20 mm, plastic part material is PC, shrinkage rate is 1.006, and plastic part weight is 41.13 grams. Technical requirements for plastic parts are that there shall be no defects such as peaks, underfilling, flow lines, pores, warpage deformation, silver lines, cold materials, and spray lines.

 

Figure 1 Product Diagram of Pulser Antenna Tube
As can be seen from Figure 1, plastic part is shaped as a round rod, with a through hole inside and a step in the inner hole at big end. There are two narrow grooves at outer diameter of detail, a thread at outer diameter of big end, a disc near big end, and 4 hooks on one side of disc, which are evenly distributed at 90 degrees. 4 hooks of big end need to be designed to pull slider core. Two annular narrow grooves at small end, from point of view of mold design, can be completely formed by using front and rear molds to open mold, and finally use slider to form, main purpose is to facilitate size adjustment, and the other purpose is to open mold after slider is formed. When left and right half sliders are separated from plastic parts, wrapping force of plastic parts on rear mold is small, which is convenient for plastic parts to be ejected. 3D drawing of mold design is shown in Figure 2.
Mold design cavity ranking is 2 cavities. Due to slender structure of plastic part and large core pulling distance, oil cylinder is used for core pulling. Mold design ranking is usually 2 cavities, and can also be designed as a 4 cavities at most. Mold base is a 396*446 mold base imitating HASCO size series. HASCO mold base is characterized by size of mold plate with 6 at the end, and thickness of mold plate is also with 6, such as 36, 46, etc. Correspondingly, structure of guide post and guide sleeve, size of hanging table at installation site are self-contained.
Design of mold gating system uses a single hot nozzle to feed glue. After molten plastic flows to parting surface, it enters edge of large disc of plastic part with a latent gate, as shown in Figure 3.
Inner hole of plastic part needs to be designed with a slender slider core. Generally, for small and medium-sized molds, it is difficult to use inclined guide column to pull core when core-pulling distance exceeds 70mm. Oblique guide posts that are too slender will appear to have insufficient rigidity and strength, and they will protrude out of mold, causing certain hidden dangers. At this time, it is necessary to use oil cylinder to drive slider to solve core pulling problem. Main thing to note is that for molds exported to Europe and United States, slender core (also called neutron) needs to be processed with Hitachi Metal's TDAC steel, processed by CNC lathes, cooled and transported internally to ensure continuous and stable injection molding production.

 

Figure 2 3D drawing of mold

 

Figure 3 Detailed structure of back mold

 

Figure 4 Rear mold diagram

 

Figure 5 Special-shaped thimble plate structure
In addition to design of cooling water inside slender core, multiple cooling circuits are designed in the front and rear molds. A heat insulation board is designed on mold panel, which effectively blocks heat exchange between mold and injection molding machine, which is conducive to normal injection molding production.
Generally, thimble plate of mold is rectangular, which is convenient for mass production. In European and American countries, when pursuing a longer mold life, rigid design of mold will be strengthened in order to prevent mold from being deformed for a long time. Under action of injection pressure, plate B is the most stressed. In order to increase rigidity of plate B, it is often necessary to increase its thickness. Another key point is to increase support area of square iron at the bottom of B plate, design square iron and bottom plate of movable mold into one, and design a push rod box surrounded by a whole. This is how DME mold base increases rigidity.

 

Figure 6 Thimble plate structure
Ejector of plastic part is ejected by ejector pin, and ejector pin is at the bottom of neutron. Therefore, it is necessary to design the first reset mechanism and stroke switch, as shown in Figure 5.