Product diagram of LCD rear case is shown in Figure 1. Maximum size of product is 430.93 mm * 312.92 mm * 70.50 mm, average thickness of plastic part is 2.15 mm, material of plastic part is HIPS, shrinkage rate is 1.005, and weight of plastic part is 496.00 grams.

 

Figure 1 LCD rear shell product picture

 

Product diagram of LCD rear case is shown in Figure 1. Specific technical requirements of product are as follows:
1. Arc without tolerance is R0.3mm.
2. For size without injection of draft angle, draft angle should be less than 0.5°.
3. Wall thickness of main part is 2.5mm.
4. Dimensions without tolerances shall be in accordance with SJ/T10628-1995 standard 6 accuracy.
5. Surface of part should be free of weld lines, shrinkage, and other injection defects. Plastic parts must not have various defects such as peaking, under-injection molding, flow lines, pores, warping deformation, silver lines, cold materials, jet lines, etc.
6. Cooling holes and 4 wall mounts, product shape refers to sample provided. All screw posts are injection molded products with an outer diameter of 6.0 and an inner diameter of 2.4mm.
Structure of plastic part is a regular rectangular shell, and top of plastic part has a number of parallel decorative lines with arc-shaped cross-sections. A number of heat dissipation grooves are designed on both sides of plastic part. These heat dissipation grooves are on the slopes on both sides of plastic part, molding problem can be solved by inserting front and back molds. Plastic part has multiple through holes on two sides, which are signal and electronic adjustment holes, socket holes of product. These two sides need to be designed with lateral slider core pulling. There are two small square holes below parting surface of one side edge of plastic part to form an inverted buckle of mold. Two inclined top moldings need to be designed. There are many protrusions or sinks on inner side of back of plastic part, there are many screw posts, which need to be designed to form a cylinder.
Size of plastic part is large, and mold design cavity rank is 1 cavity. Two sliders are respectively designed on non-operating side and ground side of mold. Mold base is standard mold base CI6070. In order to increase rigidity of mold, ø16 positioning pins are respectively designed on the front and rear molds of mold base. According to shape of plastic part, front and rear mold cores are mainly designed as a whole, with small inserts or needles partially inlaid. Size of front and rear mold cores is 500mm * 390mm. For such a large mold core, it brings difficulties to lower frame, because four sides exceed processing height of general large surface grinder and are difficult to grind. Method of tapping on both sides is usually used. That is, make 3゜～5゜ slopes on both sides of mold core, and corresponding positions of mold embryo fine frame are also matched with same slope. Take reference angle as reference, make slope on two sides away from reference. This design method is the most commonly used method for large and medium-sized mold design.

 

Glue feeding method of plastic parts is glue feeding of large nozzle directly poured into main channel. Molten plastic enters mold cavity directly through main runner, which is suitable for single-cavity deep cavity shell-shaped and box-shaped molds. Its runner process is short and pressure loss is small, which is good for exhaust, but it is inconvenient to remove gate and will leave traces of name. When designing, extend sprue bushing by 1mm and sink it by 1mm. Design a sinking rectangular position for this part. After injection molding, use electric shears or special jigs to cut it. Post a trademark to cover this position.
Two slider cores of mold are all core-pulled with oblique guide posts. Wear-resistant plates are designed on inclined surface and bottom surface of slider. Wear-resistant plates are generally made of oil steel 2510, are heat treated and quenched. Process oil groove before heat treatment. Ensure that the oil can be stored when slider moves.
Shape of oil grooves is uniformly round, and size is reasonably selected according to size of processed surface. Boundary should not be broken and depth is 0.8mm. When width of surface to be processed is small, circular oil grooves can be arranged in a straight line according to width (ratio of distance between adjacent circles to D should be smaller at this time, and recommended value is 0.7); when width of surface to be processed is larger, dimension D should be larger (ratio of distance between adjacent circles to D can also be larger), as shown in the figure below.

 

 

 

 

Figure 2 LCD back shell mold diagram

 

Figure 3 3D drawing of dynamic mold
Inclined top is guided by a guide block on the back of B plate, and inclined top seat is also designed with a wear plate at the bottom. Material and technical requirements are exactly same as slider wear plate. In mold with inclined top and cylinder, center carrier must be designed to make ejection smooth. Ejector components of mold include a thimble, a cylinder, and an inclined top.
Cooling system of mold is designed such that front mold uses direct water transport, rear mold uses direct water transport and ponds.