Shape of environmental inspection detection tube cover is shown in Figure 1. It is a long thin-shell plastic part with a wall thickness of 1.5-2.5 mm. Material is ABS+PC modified plastic. Shrinkage rate of modified material is 0.52%-0.58% . Thin wall on the side surface of molded plastic part and side holes on it are difficulties in design of mold structure. Main reason is that there are many side holes, and side walls at both ends are relatively thin. When demoulding, it is easy to pull plastic part by using side core pull of large slider. Side wall makes it deformed and cannot be restored, causing plastic part to be demoulded, deformed and damaged.

 

Combined with structural characteristics of plastic part and demoulding problem, mold adopts a layout design of 1 cavity, as shown in Figure 2. Gating system uses 2 point gates for gating. Side wall hole of plastic part adopts inclined guide column slider mechanism for side core pulling and demoulding. For demoulding of side walls on both sides, a secondary demoulding slider mechanism with a push rod is required to complete core pulling. Mold structure design is mainly aimed at selection of mold base, demoulding mechanism, gating system, cooling system, and ejection mechanism. There are 5 inclined guide post slider mechanisms in mold, among which front push rod slider mechanism is similar to rear push rod slider mechanism, three inclined guide post slider mechanisms on side are same, and design of each structural part is as follows.

 

Mold structure is shown in Figure 3. Mold base structure components include fixed mold seat plate 1, pusher plate 2, cavity plate fixed plate 3, core fixed plate 4, spacer 5, movable mold seat plate 6, push rod fixed plate 7, push plate 8, gate bushing 20; among them, fixed mold seat plate 1, push piece plate 2, and cavity plate fixed plate 3 constitute fixed mold part of mold, push piece plate 2 and cavity plate fixed plate 3 are movable plates, which can slide independently along formwork guide column 21; Core fixed plate 4, spacer block 5, movable mold seat plate 6 are combined together by screws to form movable mold part of mould.

 

1. Fixed mold seat plate 2, pusher plate 3, cavity plate fixed plate 4, core fixed plate 5, cushion block 6, movable mold seat plate 7, push rod fixed plate 8, push plate 9, cavity plate inlay Part 10, core insert 11, limit column 12, slider bead 13, core 14, slider 15, locking block 16, inclined guide post 17, pressure plate 18, cavity plate fixing plate tie rod 19, push piece Plate tie rod 20, gate bushing 21, guide post 22, guide sleeve 23, guide post 24, guide sleeve 25, die buckle
Figure 3 Mold structure

Molding assembly includes a cavity plate insert 9 and a core insert 10 . Cavity plate insert 9, core insert 10 are respectively installed on cavity plate fixed plate 3, core fixed plate 4 by screw fastening, form cavity when mold is closed.

Structure of 3 side inclined guide post slider mechanisms provided in mold is same, and mechanism includes a limit post 11, a slide block bead 12, a core 13, a slide block 14, a locking block 15, an inclined guide post 16, and a pressing plate 17. Limit column 11 and slider bead 12 are installed on core fixing plate 4 by screws, limit column 11 is used to control slide out stroke of slide block 14, and slide block bead 12 is used to control motion guide of slide block 14; Block 14 is installed on core fixing plate 4 by being installed in T-shaped groove of bead 12 of slider; core 13 is installed on slider 14, and core is driven by inclined guide post 16; Inclined guide post 16 is installed on cavity plate fixed plate 3 by pressing plate 17, and locking block 15 is installed on cavity plate fixed plate 3 by screw fastening, locking slide block 14 when being used for clamping molds.

Distance control mechanism assembly includes a cavity plate fixing plate pull rod 18 and a pusher plate pull rod 19 . Cavity plate fixing plate pull rod 18 is used to control parting and fixed distance between pusher plate 2 and cavity plate fixing plate 3; Push piece plate pull bar 19 is used for controlling separation distance between fixed mold base plate 1 and push piece plate 2.

Guide mechanism assembly includes guide posts 21 , 23 and guide sleeves 22 , 24 . Guide post 21 and guide sleeve 22 are used to control movement guidance of pusher plate 2 and cavity plate fixing plate 3; guide post 23 and guide sleeve 24 are used to control movement guidance of cavity plate fixing plate 3, core fixing plate 4 and reset positioning.

Two slider mechanisms with push rods are set in mold, as shown in Figure 4. The first core-side slider core-pulling assembly includes a pressure plate 26, a guide post 27, a push rod 28, a spring 29, a driving pin 30, a push rod cover plate 31, a slider 32, a limit screw 33, a push plate 34, and a main slider body 35, a spring 36.
Guide column 27 is pressed and installed on cavity plate fixed plate 3 by pressing plate 26. Push rod 28, drive pin 30 are installed in push plate 34, spring 29 is installed in rear push rod cover plate 31. Push rod cover plate 31 and push plate 34 are mounted on the slider 32 by screw fastening, and slider 32 is mounted on main slider body 35 by screw fastening, limit screw 33 is installed on core fixing plate 4 for controlling sliding out stroke of main slider body 35; spring 36 is installed in spring hole of main slider body 35 to assist in pushing out main slider body 35; main slider body 35 is installed on core fixing plate 4 through bead, and is used for side core pulling of molded plastic part; push rod 28 is used for the first core pulling of side of plastic part, main slider body 35 is used for secondary core pulling of side of plastic part. Structure of second core side slider core pulling assembly is same as that of the first one.

Mold ejection mechanism assembly comprises push rod fixed plate 7, push plate 8, guide sleeve 37, guide post 38, support post 39, push rod 40, pull rod 41, sprue bushing 20. Push rod fixed plate 7 and push plate 8 are fixed together by screws to form a composite plate, guide column 38 and guide sleeve 37 cooperate to guide its movement; push rod 40 is installed on push rod fixed plate 7; support column 39 is used for strength support of core fixing plate 4; pulling rod 41 is used to pull out runner condensate; sprue bushing 20 is installed on fixed mold seat plate 1, is used for installation and positioning of mold, drainage of molten plastic into mold cavity, die buckle 25 is used for sucking and closing cavity plate fixing plate 3 and core fixing plate 4.

 

26, pressure plate 27, guide post 28 push rod 29, spring 30, driving pin 31, push rod cover plate 32, slider 33, limit screw 34, push plate 35, main slider body 36, spring 37, guide sleeve 38 , guide column 39, support column 40, push rod 41, pull diagonal rod
Figure 4 Push rod slider mechanism

In actual work, working process of mold is as follows.
(1) Injection. Mold is closed, nozzle of injection molding machine injects molten plastic into sprue bushing 20, and sprue cover introduces it into cavity. After injection is completed, cooling water cools cavity plate insert 9 and core insert 10.
(2) P1 parting surface is open. When mold is opened, sliding block of injection molding machine drives movable mold part of mold to retreat. When mold is first opened at P1 parting surface, runner aggregate is separated from plastic parts in cavity, runner aggregate is held by pull rod 41 and remains on pusher plate 2.
(3) P2 parting surface is opened. Movable mold continues to retreat, and under suction of die buckle 25, core fixing plate 4 pulls cavity plate fixing plate 3, thereby pulling pusher plate 2 through cavity plate fixing plate pull rod 18 to open P2 parting surface, pusher plate 2 pushes runner condensate from pulling rod 41 to realize automatic detachment of runner condensate.
(4) P3 parting surface is opened. Movable mold continues to retreat, and under pulling force of tie rod 18 of cavity plate fixing plate and pull rod 19 of pusher plate, mold opens at parting surface of P3, inclined guide post 16 and guide post 27 respectively drive slider 14 and main slider body 35 to realize core pulling of side hole of plastic part.
(5) Launch plastic parts. Movable mold continues to retreat, ejector pin of injection molding machine pushes push rod fixed plate 7 and push plate 8, thereby driving push rod 40 to push out upwards, and plastic part is released from core insert 10 to realize complete demoulding of plastic part.
(6) RESET. When resetting, push plate resets first, P2 surface resets and closes first, then P1 surface closes, and finally P3 surface closes, finally mold is completely closed and waits for next injection cycle.