Sheetmetal Drawings Cerritos College（钣金图纸喜瑞大学）.pdfVIP

Sheetmetal Drawings Many objects, such as cardboard and metal boxes, cake pans, mail boxes, HVAC ducts, roof gutters, are made from flat sheet material that, when folded, formed, or rolled, will take the shape of an object. Since a definite shape and size are desired, a regular ortho- graphic drawing of the object is made first: then a development drawing is made to show the complete surface or surfaces laid out in a flat plane. Sheetmetal or surface develop- ment drawings are sometimes referred to as pattern drawings. Beads: Raised or depressed areas in sheet-metal parts, usually provided for purpose of rigidity. Bend Allowance: Length of material required for a bend from bend line to bend line. Bend Angle: Full line through which metal is bent: not to be confused with angle between flange and adjacent leg. Bend Line: Tangent line where bend changes to a flat surface. Each bend has two bend lines. Blank: A flat sheet metal piece, approximately correct size, on which a pattern has been laid out and is ready for machining and forming. Center Line of bend: A radial line, passing through bend radius, which bisects included angle between bed lines. Developed Length; Length of flat pattern layout. This length is always shorter than the sum of mold line dimensions on part. Flat Pattern: Pattern used to lay out sheet metal part blank. Leg: The flat or straight section of a part after bending or forming. Mold Line: A line of intersection formed by projection of two flat surfaces. Setback: Amount of deduction in length resulting from a bend to be developed in a flat pattern. Straight-Line Development: The term given to the development of an object that has surfaces on flat plane of projection (Flat Pattern). Bend Relief Cutouts: When bends intersect, a relief (notch) must be cut out to prevent the part from buckling or wrinkling. Here you are given some of the most common sheet-metal hems and joints used in the