Joining process selection

As mentioned above, a number of other selection methods exist for different joining technologies, and the reader interested in further information is referred to  

Due to the large number of different joining processes and variants, only the most commonly used and well-established processes in industry are included. Investigations 

Economic Production quantity Production rate Availability of equipment Ease of automation Skill required Tooling requirements Cost The economics of joining processes aligns the design with the business needs of the product. 

1 Permanent joint - Can only be separated by causing irreparable damage to the base material, funetional element or characteristic of the components joined, for example, surfaee integrity. A permanent joint is intended for a situation where it is unlikely that a joint will be dismantled under any servicing situation. 

2 Semi-permanent joint Can be dismantled on a limited number of oeeasions, but may result in loss or damage to the fastening system and/or base material. Separation may require an additional proeess, for example, re-heating a soldered joint or plastic deformation. A semi-permanent joint can be used when disassembly is not performed as part of regular servieing, but for some other need. 

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The authors wish to acknowledge the further support of individuals at CSC and Richard Batchelor of TRW. Special thanks are given to Bob Swain for help in the preparation of the figures and to Nathan Brown for research into joining process selection, both at the University of Hull. Thanks are also due to EPSRC for continued support of research under the Designers Sandpit Project (GR/M53103 and GR/M55145). 

This chapter certainly does not consider all possible substrates. However, the guidance that is offered should be sufficient for the user to select candidate joining processes and epoxy adhesive materials, no matter what substrate or combination of substrates is involved. 

Initiation. Protein synthesis in bacteria begins by the association of one 308 subunit (not the 708 ribosome), an mRNA, a charged tRNA , three protein initiation factors, and guanosine 5 -triphosphate (GTP). These molecules make up the 308 preinitiation complex. Association occurs at an initiator AUG codon, whose selection was described above. A 508 subunit joins to the 308 subunit to form a 708 initiation complex (Figure 25-11). This joining process requires hydrolysis of the GTP contained in the 308 preinitiation complex. There are two tRNA... 

Selection of the flux type depends on the solder alloy, metal finishes on the board and components, condition of the surfaces to be joined, the type of soldering process selected, required solder-joint attributes, and the intended final use of the assembly. 

Material type - Accounts for the compatibility of the parent material with the joining process. A large proportion of the materials used in engineering manufacture have been included in the selection methodology, from ferrous alloys to precious metals. In situations involving multiple material types the selection methodology must be apphed for each. 

Degree of permanence - This is a significant factor in determining appropriate joining processes, as it relates to the in-service behavior of the joint and considers the need for a joint to be dismantled. This selection criterion is divided into three types ... 

Quantity - Production quantity per annum, and consequently the number of joints to be produced, accounts for the economic feasibility of the joining process. The quantities specified for selection purposes are the same as for the manufacturing process selection strategy. 

In order to illustrate the selection methodology, two sample case studies are presented. The case studies show just how many different joining processes can be used on essentially the same design and how this affects part-count, assemblability and functional performance in support of DFA. 

Selecting the best joining process is critical to the success of the project and must be chosen carefully and with all considerations made. 

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