tailieunhanh - 21st Century Manufacturing Part 13

Tham khảo tài liệu '21st century manufacturing part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 354 Plastic-Products Manufacturing and Final Assembly Chap. 8 Have screws and other fasteners been minimized and reduced to snap fits Can everything be done in an automatic assembly machine Can a base part base plate or central axle be used to which everything else can be assembled This helps to orient everything toward a central assembly theme. Are subassemblies modular Has group technology been used for the next part in the assembly process Is the greatest value-adding task performed last This is an important point in case something is damaged at the last minute. Has the required assembly dexterity been minimized Design Checklist for Welding Brazing Soldering and Gluing A brief description of joining methods is appropriate here. Kalpakjtan 1995 and Bralla 1998 provide an excellent review of the physical chemistry and the DFA DFM aspects. Welding processes Intense heat from the electric arc of a welding-stick a controlled plasma arc or a spot-welding tool causes localized melting mixing and local resolidification of the surfaces of the two components being joined. This micromelting casting needs to be done in a protective atmosphere otherwise the oxygen in the air forms local oxide deposits that damage the metallurgical integrity of the finished joint. For example a consumable welding rod may serve to provide this atmosphere as it decomposes in the heat thereby generating a covering shield of inert gases. Brazing and soldering A filler material is locally melted with a soldering iron for soldered joints or a flame for a brazing operation and made to flow between the two surfaces to be joined. In contrast to welding the two main surfaces do not melt but when the filler material resolidifies a solid-state bond is created between each surface and the filler material. The filler material may be conventional electrical solder tin-lead alloys or brazing compound silver or copper alloys . Brazing gives a higher strength than soldering. Gluing methods Epoxy resins .