德语
Design of curtain bead automatic machine guide injection mold
When designing injection molds, the demolding method affects the mold structure, which is mainly reflected in the selection of the typing method to consider the convenience of molding, simple mechanism and easy processing of mold parts. When the molded parts have multiple features and the demolding directions are different, and when conventional sliders, oblique push rods and other mechanisms cannot be demolded, demolding can be achieved by multiple partitioning and sequential demolding. Therefore, the mold structure and mold release mechanisms in specific parts need to be innovatively designed.
Curtain bead automatic machine guide plate
The structure of a curtain bead automatic machine guide plate is shown in Figure 1. It is a thin shell plastic piece with multi-curved surface composite. Its main feature is a curved sheet. A flow guide groove is set on the curved sheet. After the flow guide groove is combined with the curved sheet, an inverted groove is formed between the flange at the upper end of the curved sheet and the deep groove inside the flow guide groove. The inverted groove and hole ③ are the difficulties in molding and demolding of the mold structure design. For the features of inverted grooves and holes, a special mold release mechanism needs to be designed to achieve automatic mold release of two characteristics. PC materials have good strength, but have a notch effect. ABC materials have good moldability, but their strength is not as strong as PC. Therefore, the plastic parts material uses modified alloy plastic ABS+PC, which combines the advantages of ABS and PC. The material shrinkage rate is 0.55%, and the molded plastic parts have good smoothness and wear resistance.
Partitioning and cavity layout
Type setting
In view of the difficulty in demolding the features of inverted grooves and holes, the typing settings are shown in Figure 2. After the molded plastic parts are placed in the position shown in Figure 2, the maximum outer contour of the molded plastic parts are used as the parting line. The parts of the cavity molded plastic parts are composed of cavity plate inserts, core inserts, floating cores, and side top cores. After adopting this typing setting, the mold release steps of the plastic parts are as follows: ① The PL surface is opened, and the cavity plate insert is separated first; ② The plastic parts are pushed up by the floating core in the Z+ direction, and the core insert is separated from the plastic parts; ③ The side top core pushes the plastic parts out from the upper side of the floating core, and the plastic parts remain on the side top core; ④ The high-pressure air gun blows the plastic parts out from the side top core to achieve mold release of the plastic parts.
Cavity layout
The mold uses a 1-mold and 1-cavity layout, and the casting system uses a normal runner + side gate.
Forming parts settings
The shape of the molded parts is shown in Figure 3. The floating core 1 is a movable molded insert, which is connected and fixed to each other by a push rod on the push plate. Considering the stability of the floating core and other molded parts after closing, inverted cones need to be designed in both the upper and lower parts to ensure its stability through the conical surface of the template. The core insert 2 is then fastened to the moving form by screws, and its upper end is provided for fitting the edge cone table when closed with the cavity plate insert.
The side top core 3 is installed in the floating core 1 and is pushed by the hydraulic cylinder 5 and the top rod 4 to eject sideways. The materials of the cavity plate insert, the core insert 2, the floating core 1 and the side top core 3 are made of alloy steel 2738H (Cr-Ni-Mo alloy steel). The steel has about 1% Ni added, with good prehardness and improved hardening performance. The hardness of the thick plate in large sections is evenly distributed, and is mainly used in large plastic molds, such as car bumpers, TV shells and other molds.
Mold structure layout and principle
Mold structure
1. Core insert 2. Cavity plate insert 3. Floating core 4. Elastic pin 5. Side top core 6. Side top rod 7. Upper taper block 8. Hydraulic cylinder 9. Lower taper block 10. Hydraulic cylinder taper block 11. Hydraulic cylinder top rod 12. Floating core top rod 13. Side top rod sleeve 14. Support column 15. Moving mold seat plate 16. Push plate 17. Side top core positioning stop 18. Moving template 19. Fine positioning block 20. Fixed template 21 Fixed mold seat plate
The mold structure is shown in Figure 4, and adopts a two-plate mold structure, a 1-mold and 1-cavity layout. The runner and gate are directly processed on the fixed formwork 20 , and the runner condensed material is ejected by the fixed formwork elastic pin 4 when the runner condensed material is released. When designing the cooling system, cooling water channels are provided for cavity plate inserts 2, core inserts 1, floating core 3 and side top core 5 to ensure uniform cooling of the plastic parts. The cavity is exhausted through the mating gap between the molded parts, and the mating gap is ≤0.015mm. When the fixed template 20 and the moving template 18 are closed, four fine positioning blocks 19 distributed in four corners are used to enhance the positioning accuracy of the closing.
Mold release mechanism setting
The mold release mechanism of the plastic part is a composite structure, including two sub-mechanisms: ① the ejection mechanism for the floating core 3; ② the side ejection mechanism of the side ejection core 5 installed on the floating core 3.
The ejection mechanism assembly for the floating core 3 mainly includes: a hydraulic cylinder taper top 10, a hydraulic cylinder top lever 11, three floating core top lever 12 and a floating core 1. The floating core top rod 12 and the hydraulic cylinder top rod 11 are all installed on the push plate fixing plate and are driven by the push plate 16 . The hydraulic cylinder head rod 11 is combined with the hydraulic cylinder taper top 10 by screws to eject the hydraulic cylinder 8 and the floating core 3 simultaneously, and the precise reset is achieved by relying on its taper during reset. Similarly, the floating core 3 is also combined with the floating core top rod 12 by screws at the end of the top rod. The upper and lower parts of the floating core 3 are arranged in the shape of the surrounding conical surfaces, and the upper taper block 7 and the lower taper block 9 are added to the fixed template 20 and the moving template 18 to ensure their reset accuracy.
The side ejection mechanism assembly includes: a side top core 5 , a side top rod 6 , a hydraulic cylinder 8 , a side top rod sleeve 13 and a side top core positioning stop 17 . The mechanism is installed in the floating core 3 , and the plastic part is ejected from the side surface of the floating core 3 with the side top core 5 .
Working principle of mold
After the injection is completed, the mold is moved and fixed mold opens at PL, and the local area of the plastic part is taken out from the cavity plate insert 2. When the moving mold is down in the -Z direction, after opening a certain distance, the injection molding machine top rod presses against the push plate 16 and remains unmoved, while the moving template 18 continues to go down. The floating core top rod 12 drives the floating core 3 and its upper side ejection mechanism to move. The local area of the plastic part is taken out from the core insert 1. After the floating core 3 is pushed out for a certain distance, the hydraulic cylinder 8 drives the side top core 5 to move in the -Y direction, thereby pushing part of the plastic part out of the floating core 3. The plastic part is left on the side top core 5. After moving a certain distance, the plastic part is blown off from the side top core 5 through the external air pressure gun of the injection molding machine to realize the release of the plastic part.
Based on the shape characteristics of the plastic parts, a 1-mold, 1-cavity, and two-plate injection mold was designed. In order to solve the problem of difficulty in demoulding plastic parts, a composite demoulding mechanism is designed to realize automatic demoulding of plastic parts. The composite demoulding mechanism consists of a floating core ejection mechanism and a side ejection mechanism. When the ejection mechanism works, first the ejector pin of the injection molding machine pushes the push plate to drive the movement of the floating core and the side ejection mechanism to realize the demoulding of part of the plastic part. Then the hydraulic cylinder drives the side core to push the plastic part from the floating core in the side direction. Finally, the external blowing system is used to blow the plastic part from the side core to ensure the automated production of the plastic part. The mold structure and demoulding mechanism are simple and practical, with good action reliability, which can effectively reduce the difficulty of mold processing and the cost of mold manufacturing.
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