Assembly methods

As noted throughout this book, designing a one-piece item is the ideal situation, because it precludes assembly. However, mechanical limitations and other considerations often make it necessary to join plastic parts, either to each other or to metal parts, to complete an assembly. In such instances the joining process can take an efficient approach to fabrication if a few precautions are observed and established procedures are followed. Various methods of joining can be used easily and successfully. 

The viscosity behavior of plastics makes them sensitive to strain rates as well as temperatures (see Chapters 2, 3, and 4). It therefore becomes important to define the rate, magnitude, duration, and type of mechanical stress and strain loading (i.e., tension, compression, flexure, and shear) along with temperatures during loading. The rate and duration of loading also determine whether creep or impact will be a factor in a given part s mechanical response [1, 2, 5-14, 29, 33,40-43, 55-68, 152, 202, 225, 235, 250, 270-74, 808]. 

Plastics are often used to replace stamped steel because their viscoelastic behavior at lower strain rates enables them to spring back rather than to deform under suddenly applied loads. This characteristic does add a safety factor to a design, but it also means that a part can undergo large, nonlinear deflections. Such deflections, defined as being greater than the wall thickness of the part, are difficult to analyze accurately with standard engineering equations. 

POTENTIAL HIGH BENDING STRESS AS BOLT IS TIGHTENED 

PLANNED GAP BETWEEN ADDED BOSSES PREVENTS EXCESSIVE BENDING OF HOUSING AS BOSSES TOUCH AND GO INTO COMPRESSION 

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The failure rate changes over the lifetime of a population of devices. An example of a failure-rate vs product-life curve is shown in Figure 9 where only three basic causes of failure are present. The quaUty-, stress-, and wearout-related failure rates sum to produce the overall failure rate over product life. The initial decreasing failure rate is termed infant mortaUty and is due to the early failure of substandard products. Latent material defects, poor assembly methods, and poor quaUty control can contribute to an initial high failure rate. A short period of in-plant product testing, termed bum-in, is used by manufacturers to eliminate these early failures from the consumer market. 

It prohibits the use of materials, components, or assembly methods in certain conditions. 

It is important that the produet development team be familiar with the main eapabilities and eharaeteristies of the manufaeturing and assembly methods seleeted, as well as the materials eonsidered, in order to obtain the full benefit from the methodology. Teehnieal and eeonomie knowledge for some eommon manufaeturing proeesses ean also be found in Swift and Booker (1997). 

Glycal assembly method (Section 25.11) A method for linking monosaccharides together to sym thesis polysaccharides. 

Glycal assembly method, 1002 (4- )-Glyceraldehyde. absolute configuration of, 980 (-)-Glyceraldehyde, configuration of, 300... 

All these type assembly methods usually require the same time to perform as placing inserts in the mold, but they also lower IMM time. There are several other means of accomplishing the desired result that depend on the circumstances at hand. In any event, conventional molded-in inserts usually prove costlier. There are highly automatic injection molding machines available designed just for insert molding that will reverse the cost. 

Preliminary consideration of candidate materials, processes and tooling factors, configuration, thicknesses in section, ribs, bosses, holes, surface characteristics, color, graphics, decoration, and assembly methods will begin to impose some discipline on the product design as it evolves. In the middle and latter phases of the design cycle, two or three concepts should make their validity apparent to all involved. With luck (logic), one will... 

Special Characteristics Information that describes the functionality of the application needs to be handled in a specific manner. This information can include such properties as size, weight, geometric form, special functional elements, processing and assembly methods, and other product specific information. 

With the complex where L = pyridine an optical nanosensor was developed [135-137], the method used to fix the vapochromic material to the optical fiber was the electrostatic self assembling method (ESA) and the light source used was an 850 nm LED. The sensor was tested for two different alcohols (ethanol and methanol) and it was possible to distinguish between different concentrations. It was also possible to discriminate between the two different alcohols. 

Self-assembly methods have been used to form zinc bisquinoline assemblies with high refractive index and film uniformity.287... 

A huge number of transition metal-sulfur clusters have been synthesized,36 most of which have been obtained based on the self-assembly methods. On the other hand, to construct the cluster cores with the desired metal-sulfur compositions and connecting schemes, rational pathways leading to the high-yield syntheses of tailored metal-sulfur clusters have recently been explored. Fragment condensations have been demonstrated to be the powerful methods to obtain such clusters numerously,37 some examples of which are shown below. 

In order to prepare and isolate solid-state, crystalline, oxygenated iron-heme model complexes, chemists learned to synthesize (by self-assembly methods) and oxygenate many types of hindered porphyrins. For instance, capped porphyrins were synthesized by direct condensation of a suitable tetraaldehyde with four pyrrole molecules.37 Picket-fence porphyrins such as I e(TPP)((V-MeIm) (where TPP = meso-tetraphenylporphyrin and /V-Melm = (V-methylimidazole)... 

Redox enzymes have been assembled in a monolayer on the solid surface by a potential-assisted self-assembling method as well as a thiol-gold selfassembling method. These enzymes are electronically communicated with the solid substrate through a molecular interface of conducting polymer and a covalently bound mediator. Electron transfer type of enzyme sensors have been fabricated by the self-assembling methods. 

An ordered antibody array has also been assembled on the solid surface by a combination of Langmuir Blodgett (LB) film method and self-assembling method. An ordered monolayer of protein A is deposited on the solid surface by LB method, which is followed by self-assembling of antibody. Individual antigen molecules which are complexed with the antibody array have been quantitated selectively by atomic force microscopy (AFM). 

There have been several methods for assembling protein molecules on the surfaces of various matrices. These include (1) covalent, (2) Langmuir-Blodgett, and (3) self-assembling methods. The protein assembling by these methods are mostly accompanied by appreciable loss of biological activity. 

The Glycal Assembly Method on Solid Supports Synthesis of Oligosaccharides and Glycoconjugates... 

Scheme 2.2 General strategy for the synthesis of oligosaccharides on a solid support using the glycal assembly method.

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