Product of server network card bracket is shown in Figure 1. Maximum external dimension of product is 167.84 mm * 121.61 mm * 29.65 mm, average thickness of plastic part is 2.00 mm, material of plastic part is HIPS, shrinkage rate is 1.005, and weight of plastic part is 55.07 grams. Technical requirements for plastic parts are that there shall be no defects such as peaks, underfilling, flow lines, pores, warpage deformation, silver lines, cold materials, and spray lines.

 

Figure 1 Product map of server network card bracket
As can be seen from Figure 1, plastic part structure is a non-closed rectangular shell. Except for large plane at the top, other three sides have cooling grooves, network cable connector sockets, and installation structures. Narrow side of bottom surface parallel to large plane also has narrow grooves and small rectangular holes. See attached 3D drawing.

 

Figure 2 3D drawing of back mold

 

Figure 3 Gating system diagram

 

Figure 4 Slider and parting line

 

Figure 5 4 sliders and their positioning
Structure of plastic parts is complex, difficulty of mold design lies in judgment of mold opening direction, parting line design of 4-sided slider, design of slider structure, and ejection of plastic parts.
Mold design is a systematic design. Three elements that determine mold design scheme are gating system design, ejection method and parting surface design. Mold structure analysis needs to follow three-element analysis method, analysis of mold opening direction of plastic part is the most basic foundation. Before parting surface is determined, mold opening direction should be determined first. After mold opening direction is determined, parting surface can be determined. Therefore, no matter how complex plastic part is, resulting in a very complex parting surface, or undulating, or curved surfaces and gaps, expression of parting surface should be complete, correct and unique. Expression of parting surface should not be indistinguishable or ambiguous. Mold opening direction and selection of parting surface are the most important factors in determining mold structure.
Selection of parting surface should be combined with design of gating system and should be adapted to ejection method. Therefore, three elements are interdependent and related, and analysis of three elements is basis of injection mold design. Three elements must be considered comprehensively and analyzed comprehensively to find a reasonable mold design scheme.

 

Figure 6 Front die

 

Figure 7 Rear mold core
Structure of plastic parts of server network card bracket is complex, and there are two possible mold opening directions. The first is design of laying down plastic part. At this time, if slider below inner long bone position does not perform long-distance core pulling, a clamping line will be left on long bone position, and long bone position will be uneven. On the other hand, ejecting plastic parts is more difficult. Likewise, design of gating system runners can leave unsightly marks on the edge of plastic part.
Final mold design adopts design method of standing plastic part. At this time, all four sides of plastic part need to be designed with slider core pulling. See Figure 2. Parting line of slider is shown in Figure 4. Gating system is designed as a latent gate, as shown in Figure 3.
Design of 4-sided slider is shown in Figure 5. All 4 sliders are driven by inclined guide posts. Inclined guide column driving slider has characteristics of simple and reliable structure. If there are no special requirements, foreign developed countries all adopt design of inclined guide column. Height of hanging table design on both sides of slider should be greater than 15 as much as possible, and gap with slider groove on mold base should be as small as possible. Generally, zero gap is used in design. Hanging table is shown in Figure 8. Positioning of hanging table is convenient for mold assembly and adjustment, and a gap can be left between bead and slider. With this design, positioning pins can be omitted from bead.
Limit guide locking block is shown in Figure 9. Bottom of slider is designed with a limit block, and the two sides are inclined along movement direction to facilitate guide and positioning of slider. Limit guide locking block cooperates with guide groove of rear mold core 7 .
Inclined surface and bottom of slider are designed with wear-resistant blocks, which are easy to adjust and fly.
Mold has been designed for safety. A travel switch is designed on ejector plate to facilitate detection of return travel of ejector plate. A spring is designed on the outside of small slider on sky side to prevent slider from falling after mold is opened. See Figure 10.

 

Figure 8 Design of slider hanging table

 

Figure 9 Limit guide locking block

 

Figure 10 Design of safety mechanism

 

Figure 11 Ejector mechanism
Ejection of plastic parts adopts lifter and the ejector pin. Lifter is shown in Figure 11. In addition, the entire set of molds is designed with sufficient cooling runners. See mold design 3D drawing.

 

Figure 12 3D drawing of mold