Joining, Fastening

Mechanical joints to assemble RP moldings to each other or to other components usually employ metal inserts or fixtures (also used are RP and URP types), which are molded into the product. With open/ contact molding, this can readily be organized within the scope of the molding cycle. For press molding of both TSs and TPs, it can often be a 

In some cases with TPs it is possible to insert metal fittings, such as bushes, into the molded component, using friction or ultrasonic methods of insertion, and fusing the TP around the metal insert. With RTP compounds, this may create undesirable stresses, however, and advice should be sought fi om the material supplier. 

Other useful techniques with TPs include hot staking, where the plastic is deformed around a metal part (such as a plate), to secure it in place. Methods of applying range from electrically heated irons to hot air systems, and will depend on the degree of complexity of the part, the number of hot stakes to produce and the required speed of production. 

TP components can also be welded for assembly, using hot-plate or ultrasonic systems, or by spinning two matching circular parts to weld the surfaces by fnction. The technique employed will, largely, be dictated by the type of TP involved. 

Information, as a guide, follows where a welding process is followed by (a) equipment cost, (b) tooling cost, (c) typical output rates, (d) normal economic production quantities, and (e) general remarks  

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Verbindung, /. compound combining, combination, union connection blending (of colors) joining, fastening, binding joint, bond tie, link communication union, alliance, society,... 

Polymers are characteri2ed as thermosetting and thermoplastic with respect to the methods by which they are joined. Thermosetting polymers are permanently hard and do not soften upon the apphcation of heat they are joined by mechanical fasteners and adhesives. Several methods have been devised to join thermoplastic polymers, as weU as thermoplastic composite materials, which soften upon heating. 

Emulsification involves the joining of two mutually insoluble materials, such as petroleum oil and water. The surfactant, which usually has a hydrophilic or water-soluble end and a hydrophobic or oil-soluble end, holds the oil and water together in much the same manner that a fastener holds two pieces of material. Often, the emulsion which forms is unstable, subsequently breaking up and releasing the oil from the water. Break-up is actually preferred, because the oil then floats to the surface, whereas the surfactant is free to emulsify more oil. 

Uses. Dental solders and fluxes are used to join orthodontic wires, fasten attachments to partial dentures, repair castings units, and join crown and bridge units either before or after the appHcation of porcelain. They may also be used to repair fixed and removable dental appHances. 

Metal parts are also joined by a range of fasteners rivets, bolts, or tabs. In using them, the stress concentration at the fastener or its hole must be allowed for fracture frequently starts at a fastening point. 

Polymers are joined by cementing, by welding and by various sorts of fasteners, many themselves moulded from polymers. Joining, of course, can sometimes be avoided by integral design, in which coupled components are moulded into a single unit. 

Simply bonding a stiffener to a panel with adhesive is certainly a very feasible and natural procedure with typical composite structure construction. We have not discussed any procedure for joining parts except co-curing. Alternatively, to use film adhesive for bonding parts together, we simply cut a sheet or film of adhesive to the proper size, place it between the two parts that we wish to bond together, and then go through a cure cycle that causes the adhesive to adhere to both the stiffener and to the panel itself. We can also mechanically fasten any stiffener we like to a panel. 

Different methods are used for joining or fastening and assembling plastic products and plastic to other materials. It is im-... 

A variety of techniques is available for joining plastics to themselves or to other materials—mechanical fastening, welding, and bonding with adhesives—and all are used extensively. Each method has both advantages and drawbacks for plastics, bonding might be said to be preferable when they are to be joined with dissimilar materials. 

Sometimes conventional welding or a mechanical joining process is just not possible. Substrate materials may be incompatible for metallurgical welding due to their thermal expansion coefficients, chemistry, or heat resistance. The end product may not be able to accept the bulk or shape required by mechanical fasteners. 

In the electrical and electronic equipment market, adhesives compete with other joining methods such as mechanical fasteners, brazing, welding, soldering, and thermocompression bonding. Major uses of adhesives in the electrical and electronic equipment market are shown in Table 1.5. Adhesives are generally the preferred method of joining whenever... 

However, even with these potential difficulties, adhesive bonding can be an easy and reliable method of fastening one type of plastic to itself, to another plastic, or to a nonplastic substrate. Pocius et al. provides an excellent treatise on the use of adhesives in joining plastics.51... 

Mechanical Fastening, Joining, and Assembly, James A. Speck... 

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