Product of cleaning robot brush head holder is shown in Figure 1. Maximum external dimension of product is 189.12 mm * 189.34 mm * 78.21 mm, average thickness of plastic part is 2.00 mm, plastic part material is ABS, shrinkage rate is 1.006, and weight of plastic part is 132.97 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 robot brush head holder
As can be seen from Figure 1, plastic part is structured as a complex shell similar to shape of a petal. Six of petals are evenly distributed, and the other two petals are retracted. There is a circular arc groove on the top of each petal, and signal wire harness is passed through it. For installation part on the side and window, it is necessary to design slider core pull. In the middle of petals, there are two T-shaped bones, which form an upside down button, and slider core needs to be designed. There are 8 screw columns on the inside of plastic part, which are deep in size, and reinforcement ribs next to screw columns are deeper. Therefore, wrapping force of plastic part on the rear mold is larger, that is, ejection force of mold is larger.
Dimensions of plastic parts are similar in two directions, so length and width of front and rear mold cores are similar. A fool-proof design is adopted for front and rear mold cores. Design one corner of mold as a right angle and the other three as rounded corners. This enables quick and accurate assembly of mold. Fool-proof design can also design rounded corner of reference corner to be different from the other three rounded corner radii. Since there are two gaps in the front mold core, it is necessary to ensure strength of gap, and thickness of bottom is 55, so thickness of mold core is increased, which brings difficulties to mold core framing. When mold core is under frame, it is necessary to use frame matching method of pressing block. Front and rear mold cores are made of HPM38. HPM38 is a 13 chromium series molybdenum-containing stainless steel. Heat treatment deformation is very small, so it is also suitable for precision heat treatment.

 

Figure 2 Front die

 

Figure 3 3D drawing of mold

 

Figure 4 Small inserts inlaid puzzle

 

Figure 5 Mold ranking method
Size of plastic part is large, and the two sides of side need to be designed to pull core of rear mold slider. Mold design cavity ranking is 1 cavity. Mold base is CI4550, A175, B150, C140. In order to increase contact area of parting surface to resist clamping force, a balance block is designed on the edge of movable and fixed mold, using hardened steel design production. Design of fixed module balance block is shown in Figure 6.

 

Figure 6 Design of fixed module balance block
Back mold has many bones and a large depth, so a number of small inserts are designed to simplify mold processing and facilitate mold exhaust. Small inlaid puzzle is shown in Figure 4.
Design of plastic part pouring system is shown in Figure 5. YUDO single hot nozzle is used to feed plastic on the top of plastic part.
Ejector system is designed with ejector pin and cylinder ejector. All barrels are designed at the bottom of each long screw post. No garbage nails are designed on ejector plate, but garbage grooves are designed at the bottom of ejector plate, as shown in Figure 7. Use of garbage grooves to replace garbage nails is a typical requirement for European molds. Garbage chute has a larger contact area and is superior to garbage nails in large and medium-sized molds. A travel switch is designed in ejector system to ensure return of ejector plate.
Two rear mold sliders are core-pulled by inclined guide columns. Because a thimble is designed at the bottom of a slider core, ejection system must be designed with a reset mechanism first, and then cooperate with travel switch to form a double insurance. In addition, elastic glue is designed under reset rod to make thimble plate return forcefully.
Cooling system design of mold enables fixed mold design to directly transport water, and movable mold design to design pond to ensure that injection molding cycle meets customer needs.

 

Figure 7 Design of the garbage chute