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Process Selection - From Design to Manufacture Episode 1 Part 5

Tham khảo tài liệu 'process selection - from design to manufacture episode 1 part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 64 Selecting candidate processes 2.1 Injection molding Process description Granules of polymer material are heated and then forced under pressure using a screw into the die cavity. On cooling a rigid part or tree of parts is produced see 2.1F . 2.1F Injection molding process. Materials Mostly thermoplastics but thermosets composites and elastomers can be processed. Process variations Injection blow molding allows small hollow parts with intricate neck detail to be produced. Co-injection for products with rigid cores pre-placed in the die before injection or simultaneous injection of different materials into same die. Economic considerations Production rates are high 1-50 min depending on size. Thermoset parts usually have a longer cycle time. Lead times can be several weeks due to manufacturing of complex dies. Material utilization is good. Scrap generated in sprues and risers. If material permits gates and runners can be reused resulting in lower material losses. Flexibility limited by dedicated dies die changeover and machine setup times. Economical for high production runs typically 10 000 . Full automation achievable. Robot machine loading and unloading common. Injection molding 65 Tooling costs are very high. Dies are usually made from hardened tool steel. Equipment costs are very high. Direct labor costs are low to moderate. Finishing costs are low. Trimming is required to remove gates and runners. Typical applications High precision complex components Automotive and aerospace components Electrical parts Fittings Containers Cups Bottle tops Housings Tool handles Design aspects Very complex shapes and intricate detail possible. Holes inserts threads lettering color bosses and minor undercuts possible. Uniform section thickness should be maintained. Unsuitable for the production of narrow necked containers. Variation in thickness should not exceed 2 1. Marked section changes should be tapered sufficiently. Living hinges and snap features allow part .