tailieunhanh - Composites Manufacturing - Materials, Product, and Process Engineering Part 9

Tham khảo tài liệu 'composites manufacturing - materials, product, and process engineering part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | as well as for uniform cooling rate. This will avoid the risk of part distortion and telegraphing of thickness changes through the surface. For one-piece Class A panels the nominal thickness is typically in. For two-piece panels it is to in. for outer panels and to in. for inner panels. 3. Inner and outer radii. Sharp corners must be avoided during design. A minimum inside corner radius of in. and minimum outside corner radius of in. are recommended for better material flow along the corner as well as for ease in part removal. The general rule for paintability is to make inner and outer radii as large as possible without sacrificing part function. 4. Create mash-offs for hole location. A mash-off is a localized reduction in panel thickness for creating holes during secondary operation. It is a membrane-like thin area that can be easily removed. Charge can be placed directly over the mash-off area. This promotes a more homogeneous material flow through the hole location which improves mechanical properties around the hole. Mold Design Compression molding is a match mold operation in which male and female molds are prepared. Because the charge is placed on the bottom half of the mold prior to molding there is no inlet port as in the RTM and SRIM processes. Entrapped air and excess resin escapes from the parting line as shown in Figure . The shear edge design shown in the figure reduces the need for edge trimming and thus aids in near-net-shape part molding. The shear edge closes before the flow front reaches the parting line and therefore does not allow reinforcements to escape. A stop block is designed to prevent damage to the mold during the mold closing operation. The mold is usually made of steel and is nickel or chrome plated to improve the surface finish of the molded part and the wear resistance of the mold. FIGURE Shear edge in compression mold. 2002 by CRC Press LLC as well as for uniform cooling rate. This

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