特种铸造之熔模铸造.ppt

Design Information 1 Overall size 2 Wall thickness Some areas of the part require thicker walls and, wherever possible, it is better to have the walls go from thin to thick in all directions, rather than from thin to thick to thin to thick again. In other words, avoid thicker sections surrounded by thinner ones. Figure 1 shows recommended ways of changing wall thickness. ３Joining walls ４Corners ５Isolated bosses ６Internal features　 ７Linear tolerances for cast dimensions Holding closer tolerances requires more expensive tooling, more extensive process control and often additional operations all of which increase cost. Assure you get such tolerances at the lowest possible cost 8 Wall thickness tolerances Due to the nature of the process, investment castings need more allowance for wall thickness variation, regardless of the wall thickness dimension. For lowest to highest cost, the wall tolerances are ±0.015 inch (0.38mm), ±0.010 inch (0.25mm), and ±0.005 inch Hitchiner Manufacturing Co., Inc. 9 Geometric surfaces Tolerances required for profiles, contours, perpendiculars, etc. depend on their length, so the table for linear tolerances can generally be used. For example, for lowest cost, a contour could be held to within ±0.010 inch (0.25mm) if it is one inch (25mm) long (or one by one inch (25-by-25mm), ±0.013 inch (0.33mm) if it is 2 inches long, etc. 10 Artwork 11 Machining stock lettering, knurl, company logo, lines, rule and other types of fine detail Surfaces polished for visual appeal need at least 0.005 inch (0.13mm) stock (depending on the alloy) to provide a great looking surface after polishing. 1.3 工艺特征 　　Investment casting is used with almost any castable metal, however aluminium alloys, copper alloys, and steel are the most common. In industrial usage the size limits are 3?g (0.1?oz) to about 5?kg (11?lb). The cross-sectional limits are 0.6?mm (0.024?in) to 75?mm (3.0?in). Typical tolerances are 0.1?mm for the first 25?mm (0.005?