tailieunhanh - Process Selection - From Design to Manufacture Episode 1 Part 4

Tham khảo tài liệu 'process selection - from design to manufacture episode 1 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 44 Selecting candidate processes GRAVITY DIE CASTING PROCESS CAPABILITY CHART FOR ALUMINIUM AND MAGNESIUM ALLOYS GRAVITY DIE CASTING PROCESS CAPABILITY CHART FOR IRON AND COPPER ZINC ALLOYS DIMENSION mm DIMENSION mm KEY I I Process does not normally operate within this region Represents the normal working capability of the process Dimensional tolerances cannot be achieved capably and increase difficulty cost substantially Consider another or secondary process Gravity die casting process capability chart. Pressure die casting 45 Pressure die casting Process description Molten metal is inserted into a metallic mold under very high pressures 100 bar where it solidifies. The die is then opened and the casting ejected see . Pressure die process. Materials Limited to non-ferrous metals . zinc aluminum magnesium lead tin and copper alloys. Zinc and aluminum alloys tend to be the most popular materials. High-temperature metals such as copper alloys reduce die life. Iron-based materials for casting are under development. Process variations Dies and cores are made from hardened and tempered alloy steel. Cold-chamber die casting shot cylinder filled with a ladle for each cycle. Used for high melting temperature metals. Hot-chamber die casting shot cylinder immersed in molten metal and then forced using a separate ram. Used for low melting temperature metals due to erosive nature of molten metal. Can be either plunger or goose-neck type. Vacuum die casting overcomes porosity for larger castings. Injection metal assembly variant of hot-chamber die casting for the assembly of parts such as tubes and plates cable terminations and to act as rivets by injecting zinc or lead alloys into a cavity in the assembly. 46 Selecting candidate processes Economic considerations Very high production rates possible up to 200 h. Lead time very long months possibly. Material utilization high. Gates sprues etc. can be re-melted. High initial die costs due to high complexity