Joining and Assembling

There are many different adhesive systems used to join or assemble products. There are solvent systems for most TPs, but not for thermosets. Monomeric or polymerizable cements can be used for most TPs and TSs. There are certain plastics with outstanding chemical resistance, such as the polyolefins, that preclude the use of many cements, but they generally require some form of surface treatment prior to adhesion, such as flame treatment. 

Solvent bonds work because they react chemically with the plastic. However, they literally destroy it, so it is important to limit such factors as the length of time and depth of the plastic soak. The solvent could cause either immediate or delayed damage. If a part contains excessive internal strains, the solvent could release the strains and cause cracking, surface defects, and so on. (To evaluate a plastic s reaction with a solvent. 

Foil surface around raised clear area 

Clear rect. window raised. 060 Radiused edge and shallow above surrounding surface 

Two-piece assembly avoids higher cost of metallizing mask and gives choice of other material for frame. 

Joining of a plastic product to another product composed of the same or a different plastic material, as well as other materials such as metal, is often necessary when (1) the finished assembly is too complex or large to fabricate in one piece or (2) disassembly and re-assembly is necessary. 

The success of a specific technique will depend on whether, as a by-product of the technique, sizable stress levels in the plastic product may result. Guarding against potential stresses in the assembly is a very important aspect of complete product design. There are many techniques that provide assembling all kinds of products. Each have technical and/or cost advantages and limitations. Examples of a few are reviewed in this section with more information in Chapter 3, BASIC FEATURE and FEATURE INFLUENCING PERFORMANCE. 

Use the following guidelines for material thicknesses around inserts with aluminum use 0.8 times the outer radius of the insert, with brass use 0.9 times it, and in steel 

When metal inserts require hermetic sealing, consider coating them with a flexible elastomer such as an RTV rubber, polyurethane, or epoxy system. A second method is to design an annular space or reservoir at one end of the insert from which to dispense the flexible elastomers to effectively create a hermetic seal. Flexible sealants are also used to compensate for differences in the thermal coefficient of expansion between metal and plastic. 

---

In joining reinforced thermosetting pipe it is particularly important that the pipe be cut without chipping or cracking it. It is also important to sand, file, or grind any mold-release agent from the surfaces to be cemented. Joints are built up layer by layer of adhesive-saturated reinforcement by following the manufacturer s recommended procedure. Application of adhesive to the surfaces to be joined and assembly of these surfaces shall produce a continuous bond and provide an adhesive seal to protect the reinforcement from attack by the contents of the pipe. Unfilled or unbonded areas of the joint are considered defects and must be repaired. 

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

Different processes are used for joining and assembling different parts that include adhesives, solvents, mechanical, and welding.2 41 354"359... 

Chapter 27, "Joining and Assembling Plastics," Plastics Engineering Handbook of the Society of the Plastics Industry, Inc. 4th Edition, ed. by J. Frados, Van Nostrand Reinhold, New York (1976). 

Adhestives are widely used for joining and assembling of plastics by virtue of low cost and adaptability to high-speed production. They can be subdivided into solvent or dope cements, which are suitable for... 

Fastening, Joining, and Assembling Reference Issue, Machine Design, November 17, 1988. 

Joining and assembly of medical materials and devices (ISBN 978-1-84569-577-4)... 

Medical devices are becoming more intricate with the use of a wide range of materials and components that must be joined effectively and safely. Joining and assembly of medical materials and devices provides a comprehensive analysis of the practical techniques that can be used to join and assemble medical materials. Part I reviews issues such as adhesive selection, testing and modelling. Part II discusses processes, materials and applications whilst the final set of chapters reviews safety and regulatory considerations. 

Different methods are used for joining and assembling plastic products, as sununarized in Figures 8-5 and Tables 8-3 to 8-6. Information on assembly using methods such as inserts, press fits, and snap fits, was provided in the Structural Design Analysis section of Chapter 5 see also Chapter 11. 

Fastening, Joining and Assembly Components. Machine Design. Reference issue, Nov. 

---