Products with Internal Threads

Products with internal undercuts (e.g., threaded closures, housings with a retracted edge, parts with snap-in noses. 

There is another method for producing internal threads which are too rigid to be stripped off a mold. That involves a core mechanism which collapses. Such collapsing cores are patented and there is an added cost for this mechanism. Molds utilizing these cores cycle nearly as fast as stripper plate molds and the mechanisms require a moderate amount of additional space. However, these molds are reported to have higher maintenance costs than the other types of molds and are generally thought of as a solution for applications with lower production quantities. 

Production of carbon electrodes is a capital-intensive business. Two suppHers dominate the prebaked market. Carbon paste producers are more numerous and tend to serve local markets. There is no international standard for the threaded joints on carbon electrodes. Manufacturers of straight pin carbon electrodes have followed the physical specifications adopted for graphite electrodes (37). Unified standards do not exist for pinless joints resulting in limited interchangeability among brands. Electrode diameters are offered in both English and metric sizes with no restrictions on new or unique diameters. 

The subscript i refers to gas-phase reactants and products the superscript c refers to gas-phase cell threads. The accumulation term in (3.43) is equalized to the sum of the convective and reactive fluxes. The reactive term is computed only when a control volume has a face adjacent to the catalytic geometrical surface Fext), while the other terms are considered for internal faces Pint). Face variables, denoted by the subscript f, are computed with a first-order upwind scheme. If Peclet number, defined as shown in (3.44), is significantly greater than 1 (as happens for the LNT case study described later), it is possible to neglect the diffusion term vL... 

Along with the possibility to mold-in threaded inserts, threads can be shaped directly inside the plastic material. Specific thread formers made from brass, steel, or aluminum are used to shape either internal or external threads. These have to be manually screwed off to allow the demolding of the plastic products. 

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