Tham khảo tài liệu 'process selection - from design to manufacture part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Techniques in design for manufacture and assembly 9 Identify critical characteristics tolerances surface finishes Identify factors that influence the manufacture of critical characteristics Estimate manufacturing costs Minimise component cost Establish maximum tolerances for each characteristic Determine process capability of characteristics early Avoid tight tolerances Design the part to be easily inspectable Minimise number of machined surfaces Minimise number re-orientations during manufacture Use standard manufacturing processes where possible Use generous radii fillets on castings mouldings and machined parts Avoid secondary processes Design parts for easy tooling jigging using standard systems Utilise special characteristics of processes moulded-inserts colours Use good detail design for manufacture and conform to drafting standards Fig. DFM rules and objectives. A number of general rules have been developed to aid designers when thinking about the manufacture of the product Holes in machined cast molded or stamped parts should be spaced such that they can be made in one operation without tooling weakness. This means that there is a limit on how close holes may be spaced due to strength in the thin section between holes. Generalized statements on drawings should be avoided like polish this surface or toolmarks not permitted which are difficult for manufacturing personnel to interpret. Notes on engineering drawings must be specific and unambiguous. Dimensions should be made from specific surfaces or points on the part not from points in space. This greatly facilitates the making of gauges and fixtures. Dimensions should all be from a single datum line rather than from a variety of points to avoid overlap of tolerances. The design should aim for minimum weight consistent with strength and stiffness requirements. While material costs are minimized by this criterion there also will usually be a reduction in labor and tooling costs. Wherever possible design .
