Product diagram of washing machine soap box is shown in Figure 1. Maximum size of product is 160 mm * 89.20 mm * 53 mm, average thickness of plastic part is 2.0 mm, material of plastic part is ABS, shrinkage rate is 1.005, and weight of plastic part is 67.5 grams. Technical requirement for plastic parts is that there must be no defects such as peaks, underfilled injection molding, flow lines, pores, warpage deformation, silver streaks, cold materials, jet lines, bubbles, etc.

 

 

Figure 1 Product picture of washing machine soap box
It can be seen from Figure 1 that structure of plastic part contains deep bones on both front and back sides. That is to say, both front and back sides of plastic part have great tightening force for mold. These deep bones are on the edge of plastic part. Difficulty of mold design is to first determine opening direction of plastic part, and then determine parting surface of mold on this basis. After comprehensive consideration, two places with the largest tightening force are left in moving mold. In view of key issues of mold design, mold flow analysis was carried out on plastic parts. Content of mold flow analysis includes relationship between injection time, speed and pressure switching, temperature, pressure, weld line at the front of molten plastic flow, x, y, Z deformation tendency in three directions, etc.
Plastic part has no undercut, no slider and lifter. Mold design layout is 2 cavities. Mold design drawing is shown in Figure 2. Analysis of mold opening direction is shown in Figure 3.
Mold base is standard mold base CI3545, a zero-degree positioning block is designed on the edge of mold base to assist precise clamping and positioning of mold. Design a tiger's mouth on four corners of mold core for precise mold clamping. In addition, mold is also designed with a counter on the edge of mold. In order to increase contact area of parting surface, four balance blocks are designed at four corner guide posts of mold.
After determining parting surface according to Figure 3, determine gate as a side gate, as shown in Figure 2 and Figure 4. After mold flow analysis, gating system design can meet requirements.
Back mold part of mold has a large tightening force, push blocks are designed to push out corners of outer arc surface of plastic part and adjacent two sides. In the rest of plastic part, ejector pin is designed, and ejection mechanism design is shown in Figure 5.

 

 

Figure 2 Mould diagram of washing machine soap box

 

Figure 3 Analysis of mold opening direction

 

Figure 4 Gating system design

 

Figure 5 Design of ejector mechanism
Production practice after mold is put into production shows that mold design fully meets requirements of mold design specification. Provide reference for similar mold design.

 

 

 

 

Figure 6 Mold flow analysis diagram

At the beginning of designing a simulation car, it is necessary to confirm market price and product size, price is high, functional design is comprehensive, and better materials are used. Consider how many parts to disassemble according to product size. Order of basic disassembly is order of assembly. So how is it designed? Following sharing hopes to inspire you.
1. Product size; how much is reduced in proportion to original car.
2. To confirm shape of the whole vehicle, how to open mold and how to avoid it when it is affected?
3. Material, hard plastic, transparent plastic, silica gel.
4. Mold opening angle, reserved virtual position, interference, thickness analysis.
5. Screw fixation, virtual position, draft angle, bone position, assembly, interference, and other process considerations.

 

Product appearance 3D drawing is developed by company team or provided by customer. First of all, we must understand size of product. Size of simulated toy car is different. It is determined that structural design scheme is different. Total size is 60MM, width is 18.5MM, and height is 25MM, product is small without dismantling many parts.

 

Product is relatively small and has many local features. We can mold together with body, such as door, left and right mirrors, rear lights, etc., to avoid disassembly and mold opening, which saves costs.
Car body is ejected from top and bottom when mold is opened. Side view and rear view feature many concave and convex shapes that cannot be directly opened. Choose to pull out slider through four sides to analyze whether is an undercut when part is ejected. Undercut position surface causes strain after mold opening.

 

Front and rear side glass is made into a single part for easy processing. Material is transparent or sprayed. Middle of body is designed with a cylinder. Glass hole is used to install glass from bottom view.

 

Pay attention to those points when installing glass on body design structure;
a. Inner sides of front and rear glass are designed to strengthen strength of glass and avoid appearance of internal gaps from affecting appearance.
b. Glass hole position is matched with cylinder, so that two parts can't shake left and right to play a fixed role.
c. Contact surface of two parts should be reserved for a 0.1MM virtual position to avoid problems such as some surfaces fitting after product is deformed, and gaps in other positions.

 

d. Glass is first installed to body, and structure is optimized without screws. We add four supporting columns from bottom of car.

 

Headlight requires transparent material and needs to be disassembled
Structure of simulation toy car does not need to be complicated, so add two cylinders inside headlight to install it from exterior to body, and body is made through holes at headlight to install LED light.

 

Movable wheel considers installation issues and different materials, namely tires, wheel frames, and iron cylinders.
(1) Wheel assembly is assembled, inserted into bottom of car through an iron cylinder, so design is concave and convex semicircle, but for convenience of mold opening, bottom of car is modified to open mold by bumping.
(2) Tyre is made of silica gel, which is elastic and directly inserted into wheel frame.
(3) Reserve a dummy position of 0.15 to 0.3MM for active parts, and reserve a dummy position of 0.1MM for inactive parts

 

For design techniques of fixing bottom of car to body, some products are very large, so consider using four to six screws.
We mentioned earlier that total length of this product is only 60mm, which is relatively small, so it is fixed and assembled by a screw and a buckle method. Avoid interference between bottom and edge of car. Reserve a virtual position of 0.1 to 0.2 mm.

 

(1) Disassembly skills; use position of rear compartment car number to make a deduction to replace car number, so as to achieve purpose of engineer.
(2) It is not enough to install a screw on the bottom of car and body, and other positions may be uneven, so we use M2 screws in the front. M2 screws are generally designed to be 2.2MM with bit wire barrel, and wire column is 1.7mm smaller. Buckle behind car bottom is installed in car row number position.