Printer substrate large injection mold design（1）
1. Plastic parts appearance requirement and structure analysis
Plastic part is the substrate of a famous brand printer, material: ABS, shrinkage rate of 0.5%. The detailed structure is shown in the figure below. The features of the molded part are :(1) the maximum external size is 680.00×290.00×123.50 (mm), which is a large plastic part. (2) the appearance quality of plastic parts is very high, the surface is not allowed to have weld mark, flow mark and shrinkage dent and other defects; (3) complex structure of plastic parts, lateral concave and convex structure up to 10, both inside and outside core pulling, both moving mold core pulling and fixed mold core pulling. The lateral core-pulling mechanism of die is the second difficulty in design.
2. Mold structure design
Due to the large projection area of plastic parts on the parting surface, to ensure the molding quality, the mold adopts the hot runner multi-point injection pouring system. The lateral concave-convex structure of plastic parts is formed by the fixed mode inclined slide block, the moving mode inclined slide block, the inclined top and the lateral core-pulling mechanism of "inclined guide column + slide block". Because there is a push block under the sliding block of the moving die, the die must be designed to reset the push rod plate first. The detailed structure of the mold is shown in figure 2 and figure 3.The maximum external dimension of the mold is 1250×750×878(mm), and the total weight is about 6 tons. It is a large injection mold.
2.1 molding parts design
The forming parts of the mould adopt inlay structure, which is mainly composed of fixed die inlay 10 and moving die inlay 18. Forming parts and templates are fitted with H7/m6 in transition. As the mold is a large injection mold, in order to facilitate assembly and disassembly, two wedge tightening blocks are designed between the insert and the template, as shown in figure 5. The wedge tightening Angle is 5°, and the wedge tightening block material is S136H. According to customer requirements, the forming part material is NAK80, which has excellent electrical processing performance and excellent polishing performance.
2.2 design of lateral core-pulling mechanism
There are 10 side bucking parts and 10 side core-pulling mechanisms. There are 2 inner core pulling mechanisms, 6 outer core pulling mechanisms, 1 inner core pulling mechanism and 1 inner core pulling mechanism. The lateral core-pulling mechanism is one of the most important core mechanisms of this mold. The detailed structure is shown in the figure below. In the figure, S1, S3, S5, S6, S7 and S8 are all external corepulling mechanism of the moving mold, which adopts the "inclined guide column + slide block" corepulling mechanism, and the corepulling distance is all 37mm. Positioning parts adopt the limit block 19 and spring 2, 15, 38 and 54.
Both S2 and S4 adopt the fixed-mode "inclined slider + t-shaped buckle" core-pulling mechanism, which is composed of inclined slider 6, 9 and t-shaped buckle 7 and 8, respectively. The inverted buckle depth at S2 and S4 is 24.6mm, and the core pulling distance is 27.6mm. In the core pulling process, the inclined slider and the t-buckle are not separated, so no limiting parts are needed.
Reversing S9 is inside the moving die, and core pulling is the most difficult, because its core pulling direction is not only inside the die, but also not perpendicular to the direction of mold opening, but at an Angle of 46° with the direction of mold opening. In addition, the inverted position is in the middle of the mold, which also increases the difficulty of core pulling mechanism design. In order to simplify the mold structure, with the consent of the customer, the S9 adopts the structure of "oil cylinder +T button + oblique slide block", which is composed of the slide block 41, the moving mode inclined slide block 42 and the T groove pull block 43. The core pulling distance of S9 is 20mm. Since the installation position of the cylinder is parallel to the direction of mold opening, and the t-groove is perpendicular to the direction of core pulling, the moving distance of the cylinder piston must be solved by drawing method.
S10 is inverted inside of the moving die, and the distance of core pulling must reach 25.5mm. To avoid interference with S9, the lateral core pulling adopts the inclined top inside core pulling mechanism, and the inclined top 50 slides on the base 49 mounted on the push rod fixing plate 46. Special attention should be paid to the fact that the inclined roof is long, guide block 51 must be designed to ensure the stability and reliability of the inclined roof sliding. The tilt Angle of the inclined top 50 is designed to be 12°, which is within the safe range. Injection Mold