Part geometry

Project Engineer uses numerical input values of maximum flow length, nominal wall thickness, and projected area to describe the part geometry. 

It is fundamental, therefore, to control the rate of heat absorption and temperature variations during the cure cycle [33,34]. The cure cycle depends on the part geometry, thermal... 

Delaminations can occur during cure as a result of high internal stresses. These stresses develop due to resin shrinkage and thermal volume changes. The level of stresses depend on several material properties, such as the Young s modulus, Poisson s ratio, and thermal expansion coefficients of both resin and fibers. In addition, the level of stresses also depends on several conditions, such as fiber orientation, fiber volume fraction, and part geometry. 

Some tests are affected by core orientation and some test properties are more influenced by surface orientation. Since orientation is not uniform, but has a gradient through and along the flow path, it is difficult to predict directly the effects of process conditions on part properties, without a complex model of the part geometry and estimation of flow characteristics in the cavity. 

Sipitkowski, J. M., Design for Cleanability Part Geometry and Surface Finish, Precision Cleaning, l(l) 55-57 (Nov./Dec. 1993)... 

Shrinkage in Parts Molded from Thermotropic Liquid-Crystalline Polymers Dependence upon Part Geometry and Filler Content... 

Volumetric CTE appears to be preserved for a specified formulation, independent of gate or part geometry. Analysis of CTE behavior for the filled LCP compositions indicates some anisotropy remains even at relatively high loadings of filler. 

Figure 1 details the 3-dimensional nature of the linear CTE s for an LCP molded part. These linear CTE s can be very dependent upon part geometry, gate location, and molding conditions. From reference f71 and Figure 1, the following definitions can be made ... 

For a complex part geometry containing numerous flow interruptions, such as pins in a long connector, the 3-dimensional CTE s may be much closer together, i.e., the part is more isotropic. Where the part is completely isotropic the linear CTE, a, is identical for all three directions ... 

Table I gives the summary of CTE measurements made on neat and filled XYDAR molded parts. These CTE measurements were performed in a temperature range from 0-150 °C using a DuPont 942 thermomechanical analyzer (TMA). The CTE s shown in Table I are measured in the flow, transverse, and thickness directions for the formulation and part geometry specified. In a part of center-gated geometry, the radial direction is the flow direction and the circumferential direction is the width direction. All of the TMA testing was performed on aB-molded samples (no annealing).

In addition to the Faraday Cage effect, aerodynamic effects do not favor spraying inside a corner. Airflow considerations based on part geometry must also be taken into account to deliver the highly charged powder inside a corner or a channel, while not using so much air that the powder is prevented from depositing. 

There are several issues to be addressed when designing the apparatus and procedure for producing components by the graded casting approach. These play a key role in the successful application of the process for producing the desired part geometry having the required composition profile. 

Part ultimate deflection. The maximum deflection of an application is dependent upon the percent strain to failure of the material, part geometry, loading, and constraint. 

Table 5.1. Selection of Granular Fabrication Process Based on Part Geometry...

Mandrels - Hard parts (normally metallic) which are inserted in molds to obtain desired part geometries. For example, a solid metal mandrel is placed inside an isostatic cylindrical mold in order to obtain a polytetrafluoroethylene liner. 

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