Figure 1 shows plastic part of YD110 server cooling frame. Its main body is a thin shell, inner wall has multiple clamping posts and screw posts. Material is ABS+PC, and shrinkage rate is 0.58%~0.61%. Difficulty of mold design lies in demoulding feature of clamping column. Clamping column is tubular, and its lower end forms a whole circle of inverted buckles when plastic part is demolded. Design of demolding mechanism will affect demoulding of outer wall of plastic part. Inner wall of clamping column is a deep tube, and it is also difficult to demould inner wall due to large wrapping force generated by shrinkage after molding. In addition, there are 2 side holes of φ3mm on one side wall, and a side core pulling mechanism is required for core pulling and demoulding. Therefore, solving demoulding problem of stuck pillar feature is key and difficult point of mold structure design.

 

Aiming at characteristics of clamping column of plastic part, a forced demoulding mechanism for second push-out of round tube is designed, as shown in Figure 2. Primary push tube 2 is sheathed outside tube core 3, and its lower end is sheathed in corresponding hole of movable mold plate 4, and is pressed by push tube locking plate 6; movable mold plate 4 is supported by a push tube spring 11, which is mounted on backing plate 8 and is fitted into hole opened in middle plate 10. Lower end of tube core 3 is pressed and installed on intermediate plate 10 through tube core locking plate 7, and inner hole of plastic part clamping column is formed at upper end, and secondary push rod 9 is installed on mold push rod fixing plate, and is used to push secondary push plate 1 to push up.

 

1. Secondary push plate 2, primary push tube 3, tube core 4, movable template 5, short pull rod 6, push tube locking plate 7, tube core locking plate 8, backing plate 9, secondary push plate 10 , middle plate 11, push tube spring 12, pull die buckle
Top of primary push tube 2 forms outer ring of plastic part, and there is a limit shoulder on it to limit pushing distance; secondary push plate 1 forces plastic part from inner wall of primary push tube 2 for second time roll out. Working principle of clamping column demoulding mechanism is as follows: mold is first opened at P1 parting surface to realize separation of plastic part and fixed mold cavity, P2 parting surface is opened to realize automatic demoulding of inner hole of clamping column, and P3 parting surface is opened to realize complete demoulding of plastic part. When mold is opened, P1 parting surface is opened, and after movable mold descends for a certain distance, push plate is held up by ejector rod of injection molding machine to push out plastic parts. During push-out process, secondary push rod 9 bears against secondary push plate 1. Secondary push plate 1 pulls movable mold plate 4 through suction force of die-pulling buckle 12 to ensure that movable mold plate 4 is synchronized with secondary push plate 1; Under action of push tube spring 11, mold is opened on P2 surface, movable mold plate 4 is separated from intermediate plate 10, tube core 3 is separated from plastic part. As movable mold continues to descend, intermediate plate 10 pulls movable die plate 4 down through short pull rod 5, and its driving force will overcome friction force between die puller 12 and secondary push plate 1, so as to realize separation between secondary push plate 1 and movable mold plate 4 (P3 parting surface is opened), secondary push plate 1 forcibly pushes out plastic part from core to realize complete demoulding of plastic part clamping column.

Combined with design of forced release mechanism for second push of round tube undercut, mold structure is shown in Figure 3. Mold adopts a two-plate mold structure, a single-cavity adopts a single-point side gate, and a 2-cavity layout. Secondary side core-pulling inclined slider mechanism of inclined guide column is used for demoulding of two φ3mm side holes, cavity is cooled by a cooling pipe, and diameter of pipe is φ8mm. Compared with ordinary two-plate injection mold, a secondary push plate 1 and an intermediate plate 10 are added to mold base mold plate to ensure that clamping column release mechanism can smoothly realize release function.

 

1. Secondary push plate 4, movable platen 10, middle plate 11, push tube spring 13, fixed die base plate 14, fixed platen 15, backing plate 16, push rod 17, push plate 18, movable die base plate 19, slide Block head 20, slider spring 21, limit screw 22, insert 23, insert 24, slider 25, inclined guide post 26, connecting block 27, cavity plate insert 28, core insert 29, gate Bushing 30, retaining ring

In actual work, mold completes injection molding of plastic parts according to following steps.
(1) When mold is opened at P1 parting surface, secondary side core-pulling slider mechanism of inclined guide column completes core-pulling, and plastic part is demolded from cavity plate insert 27.
(2) When mold is opened at parting surfaces of P2 and P3, the first demoulding of forced demoulding mechanism by second push-out of round tube is completed.
(3) When mold is fully opened, plastic part is pushed out from core insert 28, and round tube is inverted for a second push and forced demoulding mechanism is forced to push and demold for second time.
(4) When reset, push-out mechanism is reset first, then mold is closed in order of P3, P2, and P1 parting surfaces.