Key points of injection mould design for hot nozzle of mobile phone bottom shell
The bottom case of the mobile phone is shown in Figure 1. The maximum size of the product is 97.50 mm x 43.85mm x 10.10 mm, the average thickness of the plastic part is 1.00 mm, the plastic part material is ABS+PC, the shrinkage rate is 1.006, and the plastic part quality is 7.16 Grams. The technical requirements for plastic parts are that there must be no defects such as peaks, dissatisfaction with injection molding, flow lines, pores, warpage deformation, silver lines, cold materials, jet lines, etc.
The mobile phone shell is composed of upper and lower shells. After the upper and lower shells are assembled, the joint surface is required to be smooth without scratching, and the appearance is beautiful. The mobile phone shell is a very demanding plastic part with high appearance, which has high requirements on the mold. The plastic parts of the mobile phone shell are made of ABS+PC. The last issue of the article has analyzed the key points of the mold design of the face shell, and this issue will continue to analyze and introduce the key points of the bottom shell mold design.
The mobile phone shell mold is a precision mold. The mold cavity is ranked 1 out 1. The mold base is a standard mold base CI2330. The left and right sides of the mold base are designed with a slope positioning block to facilitate precise mold clamping and resistance to injection molding. Xiangli. The glue feeding method of the mold is to feed the glue at one point at the point of the gate, and use a single hot nozzle to feed the glue, and the glue feeding position is on the top surface of the plastic part.
The mobile phone shell is divided into a front shell and a bottom shell, and the two are usually assembled tightly with a buckle. Therefore, the key points in the design and production of the mobile phone shell mold are the design of the lateral core pulling mechanism and the design of the inclined roof. Generally, the cross-section size of the inclined roof of the mobile phone shell mold is small. Therefore, the inclined roof needs to be paid attention to when making:
(1) It is made of better steel, which needs to have higher toughness and wear resistance.
(2) The wire cutting accuracy should be high, and the medium wire or slow wire wire cutting is often used.
(3) There must be an oil groove on the non-glue position of the inclined roof. The oil tank is more than 10mm away from the glue position.
(4) For long-life molds produced for a long time, the inclined top surface needs to be nitrided, PVD treated, and DLC treated. DLC film not only has excellent wear resistance, but also has a very low friction coefficient, generally lower than 0.2, which is an excellent surface anti-wear modified film.
(5) Clearance. There should be a large gap between the small inclined top of the mobile phone shell mold and the back mold core to have a long life. As the saying goes, the inclined top should be looser.
(6) For the inclined top, make a guide block on the back of the B plate, and use the guide block to guide to avoid damage. For the guide block, see part 5 and part 33 in the mold design diagram 2.
The plastic part structure is a flat shell, and there are three places around it that need to be designed with lateral core pulling, one of which is the front mold slider. For hot runner or hot nozzle molds, since the fixed template is fixed, no template can be separated, so it is difficult to design the front mold core. In this set of molds, the front mold slider 21 of the cylinder core is designed. For the front mold slider of the oil cylinder core pulling, if the area of the core pulling is small, the lateral force of the slider expansion is not large, and the oil cylinder can be used directly, without the need for wedge locking. This is the case of this set of molds, and the core is drawn directly with an oil cylinder. The two outer slides are movable mold slides, which are driven by oblique guide posts.
Both the front and rear molds are designed with a wrap-around direct water transport, which effectively guarantees the normal progress of injection molding. The water transported around the front mold is hot oil, the water transported around the hot nozzle is cold water, and the water transported by the rear mold is cold water. The main purpose of passing a set of hot oil to the front mold is to increase the surface temperature during injection molding and improve the appearance quality of the surface of the plastic part.
In addition to the inclined top, the ejector of the plastic part is also designed with a thimble.
Daisy Wang
Sales Engineer, ABIS Mold
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