Injection molding operational conditions

Several injection molding operating parameters must be optimized in order to produce a microfluidic device with a high degree of feature fidelity. Figure 4 presents the impact of the feature fidelity of different micron-sized post features as a function of barrel temperature and injection velocity. It is also important to note that computational modeling can be employed to predict optimal injection molding conditions. 

Injection molding operation is the most widely employed processing methods in the plastics industry. During the injection molding process of semi-crystalline polymers, the processing conditions and the positiorrs in the cavity influence crystal structures of the articles, which are the important parameters of describing crystallized polymer mecharrical characters. 

Injection molding allows the rapid, economical production of small to large parts. It provides close tolerances and the same machine can be used to mold many different articles. Parts can be molded combining the polymer with other polymers and with any number of additives. Further, it can be nm so that various parts can be easily married as part of an entire or combined-parts production assembly of an article. The ability to easily modify the operating conditions of the injection-molding machine is important because of the variety of articles that may be needed, variety of material employed to produce the same (general) article, variety of materials to produce different injection-molded articles, and the variability of supposedly the same polymer material from batch to batch. 

Processing. Polycarbonates may be fabricated by all conventional thermoplastic processing operations, of which injection molding is the most common. Recommended operating conditions are stock temperatures of 275—325°C and molding pressures of 69—138 MPa (10,000—20,000 psi). 

Two kinds of information are usefuL one concerned with the unvnlcanized rubber, so as to determine the best operational conditions of temperature and time for the injection molding and the other characterizing the final vulcanized rubber compound. 

These functions must be performed automatically under conditions that ideally should result in a high quality and cost-effective part. Injection molding machines have two principal components to perform the cyclical steps in the injection molding process. These are the injection unit and the clamp unit (Figure 11.4). We now describe the operation of the various units of the injection molding machine... 

It is obvious from this discussion that procedures for reducing part shrinkage work in direct opposition to those required for preventing its warpage. Therefore, the injection molding of a trouble-free part requires a careful balancing of these operating conditions. 

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