Printer substrate large injection mold design（2）
2.3 design of distance parting mechanism and guiding and positioning mechanism
Since S2 and S4 are fixed mode lateral core-pulling mechanisms, S2 and S4 must complete the lateral core-pulling before the moving and fixed mode is opened, otherwise the molded parts will be locked in the fixed mode and cannot be released. Therefore, a parting surface must be added to the fixed mold side, as shown in figure I, and parting surface I must be opened before parting surface II to complete the core pulling of the fixed mold, so as to ensure that the plastic parts remain on the moving model core when the parting surface II is opened.
The inverted depth at S2 and S4 of the printer substrate is 24.6mm, and the lateral core pulling distance at these two places should be 2~3mm larger than the inverted depth. Take 27.6mm, and the inclined Angle of the inclined slider 35 is 12°. According to the trigonometric function (or drawing method), the opening distance of the scoring surface I is: 27.6÷tg12°≈130mm.
In order to ensure the order and distance of mold opening between the templates, the mold separation mechanism with fixed distance is designed, as shown in the figure. The mechanism consists of spring 59, small rod 60.
This mold belongs to large mold, guide positioning system USES a four long guide pillar 57, four short guide pillar and 12 61 guide bush, is one of the long column specifications Ø 80 x 620 mm, short guide pillar of the specifications of the models is Ø 80 x 380 mm.
2.4 casting system design
The projection area of molded plastic parts is large, and it is difficult to fill the plastic melt. After discussing with the customer, we decided to adopt the 4-point hot runner pouring system. Although this will increase the mold cost, but can effectively ensure the molding quality requirements of plastic parts. The mould pouring system is composed of first stage nozzle 33, hot runner plate 30 and 4 second stage hot runner 31, in which the hot runner plate is heated by 10 heating rods.
2.5 design of temperature control system
Plastic parts belong to the plate type parts, mold cavity is relatively shallow, but the area is large, the design requirements of the temperature control system is to achieve a cooling balance, so that the mold cavity surface temperature is roughly equal, otherwise, molding plastic parts prone to warping deformation, welding mark and filling defects; Second, the cooling must be sufficient, and the heat transferred from the plastic melt to the mold should be taken away timely and continuously, and the mold temperature should be controlled at about 60°, so as to ensure the labor productivity of the mold. To this end, 9 straight-through cooling water pipes were adopted in the moving mode side, while 6 waves in the fixed-mode side adopted the cooling form of "straight-through water pipes + Wells", with the diameters of water pipes and Wells all having the limits of rice 10mm.
2.6 demoulding system and first reset mechanism design
The mold mainly USES a combined release mechanism of "push-rod + push-block", wherein the push-rod includes 12 ∅12×450mm push-rod and 23 ∅6×450mm push-rod. Push block is mainly used to push plastic parts outside, stable and reliable. However, because the push block is just below the slide block, if the push block is not completely reset when the slide block is reset, the two may collide, causing a serious safety accident. In order to prevent the occurrence of safety accidents, this mould designs the first reset mechanism of swinging rod type push block, which is composed of the first reset push block 64, swinging rod 66 and swinging rod 67. Special attention should be paid here: although the reset rod has the function of reset, it cannot ensure the complete reset of the push block until the mold A and B plates are closed, and it does not have the function of reset first. Reset spring has the function of first reset, but the reset spring will fatigue failure, can not guarantee 100% reliable. According to murphy's theorem "if it can happen, it will happen", so the mold must be designed to push the fixed plate reset mechanism.
3 results and discussion
- high precision and added value of printer substrate. Mold through the use of needle hot runner technology, dimensional accuracy reached MT3 level, plastic parts tensile test increased by 25 pounds, molding cycle from the original 40 seconds to 36 seconds, not only to meet the large plastic parts substrate molding quality requirements, and improve the mold labor productivity.
- by adopting the technology of oblique inner core-pulling of hydraulic cylinder, the mold not only simplifies the structure of the moving mold, but also greatly improves the stability and safety of the lateral core-pulling of the mold. Since the release of the die, there has not been a single fault caused by the lateral core-pulling mechanism.
- by adopting the swing rod first reset mechanism technology, the mold effectively guarantees the reliability and safety of the return journey of the inclined roof and slide block side core-pulling mechanism.
To sum up, the injection mold structure is advanced and reasonable, the production is stable since the release of production, and the quality indexes of the molded parts meet or exceed the design requirements. It is a classic example of large, complex, precise and long-life injection mold design.