Process selection joining processes

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... 

AM processes work without part-specific tools (tool-less). The tool is represented by the element that contours each layer and joins adjacent layers. It is changed neither during the build process nor from one build process to another (process-oriented tool selection). 

Adhesion is an interfacial phenomenon that occurs at the interfaces of adherends and adhesives. This is the fact underlying the macroscopic process of joining parts using adhesives. An understanding of the forces that develop at the interfaces is helpful in the selection of the right adhesive, proper surface treatment of adherends, and effective and economical processes to form bonds. This chapter is devoted to the discussion of the thermodynamic principles and the work of adhesion that quantitatively characterize the surfaces of materials. Laboratory techniques for surface characterization have been described which allow an understanding of the chemical and physical properties of material surfaces. 

It is usually necessary to compromise on some of these requirements when selecting a practical joining system. Some properties and characteristics that are desired will be more important than others, and a thoughtful prioritization of these criteria will be necessary in selecting a process. 

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. 

Different manufacturing technologies such as primary shape generating processes, joining techniques, assembly systems and surface engineering processes require that selection takes place based on the factors relevant to that particular technology. For example, the selection of a joining technique may be heavily reliant on the ability of the process to join dissimilar... 

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. 

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