Manufacture of Moulds

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In the theoretical-practical classes, the contents are presented that allow the knowledge of the different types of molds, constituent elements of the molds and polymeric parts produced. To this end, videos, photographs, technical drawings, different standard mold components and some existing molds are presented in the Mechanical Engineering department. Different polymer parts produced by injection are also presented and analyzed in detail. In pratical classes, the injection of polymeric parts with different thermoplastic materials is simulated using software, and the form of mold design is also initiated through software.

Identify the main types of molds used in the industry; Know the thermoplastic injection cycle and the main process parameters; Know the main machining processes applied in the manufacture of molds and establish the relationship between the geometry to be obtained and the most suitable processes for obtaining it; Select the most suitable materials and heat treatments to be applied in Thermoplastic Injection molds; Know the functional systems of thermoplastic Injection molds and the main standard elements existing on the market; Know how to apply specific rules for the design and manufacture of injection molds for thermoplastics.

1. Introduction to mold making

Mold definition and mold history in Portugal. Application of molds in industry: Molds for the production of glass parts, molds for forming ceramic materials, molds for die-casting and molds for the production of polymeric parts.

2. Injection of thermoplastics and respective injection molds

Molding cycle and variables to be adjusted in the injector control system. Closing force and closing unit. Typical injection molding conditions for different thermoplastics. Most common defects in injected parts. Injection mold planning. Typology and classification of injection molds: i) solid or structured molds, ii) 2 or 3 plate molds, III) cold or hot channel molds, iv) other type of molds;

3. Materials and hardening materials for thermoplastic injection molds

Properties required for molds and mold service life. Steels, copper alloys, aluminum alloys. Polishing degrees. Stresses, deformations and cracks in the molds. Protective rules to prevent cracking. Heat treatments and surface coating for hardening materials.

4. Manufacturing processes applied to molds

Chip cutting: Milling, turning and drilling. Electro-erosion cutting and grinding. Application of CAD / CAM systems to mold making.

5. Functional systems for thermoplastic injection molds: Molding areas, guidance and locking.

Mold tolerance and contraction of thermoplastics. Centering: accessories, alignment and guidance. Mold finishing and assembly.

6. Functional systems for thermoplastic injection molds: Gas supply and exhaust systems.

Feeding systems with cold channels: sprue, feeder and attacks. Feeding system with isolated channels and feeding system with hot channels. Gas exhaust system.

7. Functional systems for thermoplastic injection molds: Temperature control systems.

General temperature control rules. Water holes for bushings and cavities. Accessories for temperature control circuits: screws and closing plugs, seals and connections.

8. Functional systems for thermoplastic injection molds: Extraction systems.

Simple extraction. Extraction with counter-outlets. Extraction with seesaws. Extraction with movements. Other types of extraction.

9. Use of Computer Applications in Mold Design.

Use of Mold Tools and Plastics modules from the SolidWorks® Software. Using the MasterCAM Software.

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Recommended Bibliography:

• Matos, A. (2003). Manual do Projectista para moldes de injecção de plástico. Edição Centimfe  [disponível na biblioteca do ISEC em 4-6-150]
• Martins, P. (2019). Desenho e Projecto de Moldes, Edição Centimfe e FCA
• Provenza, F. (1982). Moldes para plásticos. Escola Pro-tec  [disponível na biblioteca do ISEC em 4-6-70]
• Vaz, E (1987). Moldes, Cunhos e Cortantes. Editora Lopes da Silva
• Rosato, D., Rosato, D., Rosato, M. (2000). Injection molding handbook (3rd.  ed.). Kluwer Academic Publishers – Palatine Press [disponível na biblioteca do ISEC em 4-6-148]