Cleaning head body is body of a famous brand cleaner, its function is similar to a mop, and it is an advanced cleaning tool driven by electricity. Product of cleaning head body is shown in Figure 1. Maximum external dimension of product is 335.00 mm * 250.50 mm * 133.67 mm, average thickness of plastic part is 2.56 mm, plastic part material is ABS, shrinkage rate is 1.006, and plastic part mass is 334.04 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 cleaning head body
As can be seen from Figure 1, plastic part structure is shaped as a complex irregular shell. There is one place on inner and outer sides that needs to be designed for slider core pulling. There are many deep bone positions on the back of plastic part, inserts need to be designed to solve problems of mold manufacturing and injection molding. Bone position inside plastic part is designed with inverted buckles in many places, and it is necessary to design a sloping top to demould. See attached file for 3D drawing of cleaning head body mold.
Size of plastic parts is large, mold is a large mold, and injection molding machine matching mold is a 400-ton injection molding machine. Mold cavity ranking is 1 cavity, mold base is CI6080, A180, B270, and C190; specifications of mold base exceed those of standard mold base.
Correspondingly, size of front and rear mold cores is larger, size of front mold core is 470*360, and weight reaches more than 150kg. Four corners of front and rear mold cores are designed with a tiger's mouth, M20 lifting process hole is drilled and tapped at tiger's mouth to facilitate handling of mold parts. According to theory of ergonomics, generally parts over 20kg must be lifted by a crane. Front die is shown in Figure 2. Lower frame method of front and rear mold cores is reference angle positioning, and the two sides away from reference angle are all designed with squeeze blocks to be fixed. This is basic form of large mold core framing.

 

Figure 2 Front die

 

Figure 3 3D drawing of mold
Top surface of plastic part is all appearance surface, and gate cannot be designed. Size of plastic part is large, bone position is complicated, and process of melting plastic is long. Therefore, it is very important to design gating system reasonably. Selection of gate position is shown in Figure 3. Gate position is designed at higher part of center of plastic part. Due to steep parting surface and slider core pulling in the middle position, gate can only be a point gate or a single hot nozzle. After glue reaches parting surface, it is transferred to side gate to enter glue.
4 rear mold sliders of rear mold are all driven by inclined guide columns, and wear plates are designed on the slope and bottom of slider to facilitate adjustment and replacement of flying mold. Due to limited space of the two sliders in the middle, a wedge is used to drive the two sliders. When designing a mold with two sliders driven by one wedge, care should be taken to make slider slope and core-pulling distance on both sides equal as much as possible.

 

Figure 4 Deep bone inlaid puzzle

 

Figure 5 Ejector system design
Rear mold has multiple bone positions, and exhaust of mold is very important. Multiple inserts are designed to be spliced together to facilitate exhaust. At the same time, it is beneficial to electric discharge machining and saving mold. See Figure 4. Height difference between plastic parts of this set of molds is large, so movable mold plate is thicker, and depth of rear mold precision frame is large. At this time, inserting method of inserts needs to be paid attention to. There are many ways to fix inserts. Large inserts must be secured from bottom with screws. Small inserts, but those with rubber rings at the bottom should be fixed with screws. Especially small inserts should not be fixed with screws as much as possible. Because length of small screws is limited, holes are very deep on larger template, installation of small screws is limited by vision, so it is not easy to see clearly, and it is particularly prone to phenomenon of missing screws.
Back mold of plastic part has more bones, and tightening force on movable mold is larger. Next to bone position, multiple thimbles are designed to be ejected. Due to large thickness of B plate and long lifter of mold, lifter cannot be widened due to close distance between bones and limitation of space position. Therefore, in order to avoid lack of rigidity caused by long lifter, design method of two-stage sloping roof is adopted. Structure of lifter is shown in Figure 6.

 

Figure 6 Structure of lifter