With the increasing internationalization of manufacturing industry, shortening the product development cycle and reducing the investment risk of developing new products have become the key for enterprises to survive. It can manufacture injection molds, die-casting molds, stamping molds and other precision and complex molds. At present, it has been widely used in the fields of automobile, aerospace, ship, household appliances, industrial design, medical treatment, construction, handicraft production and children's toys. With the continuous development and improvement of this technology itself, its application range will be expanded. In the automobile and home appliance manufacturing industry, die forming parts account for 50% ~ 70% of the manufacturing hours.

Injection mold is also called injection mold. The basic composition and molding process characteristics of this mold have been mentioned above. Injection mold is mainly used for the molding of thermoplastic products. In recent years, it is also more and more used for the molding of thermosetting plastic products. Injection molding accounts for a large proportion in the molding of plastic products. More than half of the output of plastic molding molds in the world are injection molds.

Classification of Plastics: there are many kinds of plastics, which can be divided into thermoplastic and thermosetting plastics according to their processing properties. Thermoplastics are plastics that can be repeatedly heated, cooled and hardened within a specific temperature range. Thermosetting plastics are no longer fusible and plastic when heated to a certain temperature.

Typical injection mold design process in Pro / Engineer environment, the injection mold design process includes the following steps:

(1) Create a plastic part model (also known as 3D modeling);

(2) Create a blank to define the volume of all die components;

(3) According to different shrinkage, demoulding slope and plastic part model, the characteristics and dimensions of cavity and core are constructed;

(4) Add mold assembly features to form gating system and define parting surface and module;

(5) Define the mold opening steps and check the interference;

(6) Assemble the die base as required to complete the cooling system design;

(7) Complete the part drawings of all parts;

(8) Generate the NC code of the part according to the machining needs.

Next, take a part of an automobile as an example to introduce the design process of this course design

(1) Create a plastic part model (also known as a 3D shape)

The following items should be paid attention to when establishing 3D part drawing

1) The wall thickness of parts shall be determined reasonably

1. Reduce the wall thickness as much as possible on the premise of meeting the use requirements; 2. The wall thickness of each part of the workpiece shall be as uniform as possible to reduce internal stress and deformation; 3. The compression strength must be ensured at the part bearing the fastening force; 4. Avoid shrinkage cavities and depressions at excessively thick parts; 5. Be able to bear the impact of impact force during forming and ejection.

2) The necessary demoulding slope must be set

1. For plastic parts with large shrinkage, a large demoulding slope shall be selected;

2. For large-size parts or parts with high dimensional accuracy requirements, a small demoulding slope shall be adopted;

3. When the wall thickness of the workpiece is thick, the forming shrinkage increases, so the demoulding slope should be larger;

4. For reinforced plastics, the demoulding slope should be larger;

5. Easy demoulding plastics containing self lubricant can be small;

6. Generally, the demoulding slope is not included in the tolerance range of parts.

3) Corners shall be designed as rounded corners as far as possible

Fillet can avoid stress concentration and improve the strength of parts

Rounded corners can facilitate mold filling and demoulding

Fillet is conducive to mold manufacturing and improve mold strength