ASME Y14.31-2014 pdf – Undimensioned Drawings
ASME Y14.31-2014 pdf – Undimensioned Drawings.
12 FLAT PATTERN DEVELOPMENT
A flat pattern Li tines an item with all flanges and formed surfaces flattened into a single plane. Although this deals primarily with sheet metal items, flat patterns may he developed for composite plies, cloth, etc. The drawing should define an item without specifying manufacturing methods. I lowever, the undimensioned drawing may be prepared to favor the use of specific methods of forming by specifying parameters and using terminologies that are method specific.
12.1 General Requirements
Basic presentation of a flat pattern is shown in Fig. 5-4. Flat patterns should he developed as monodetail drawings. Superimposed cross sections on the flat pattern or formed views are permitted to clarify the shape of the item.
12.1.1 Brake Process Requirements. When items with straight bend lines are formed using a brake process, the bend line is indicated as a CLB. See Fig. 3-2. Items that are formed using a brake process shall have the majority of the flange bend instructions indicating bend up.
12.1.2 Hydro Process Requirements. When items with curved bend lines are formed using a hvdro process over a forming block, the bend line is indicated as an IML or FBL. See Fig. 3—3. For manufacturing efficienc multiple straight bend lines or a flange with a joggle may be formed using a hvdro process. Items that are formed using a hvdro process shall have the majority of flange bend instructions indicating bend down.
Solid lines shall be used to define the periphery of the item. \1hen excess material is shown for forming or tool tabs, indicate the trim line for the periphery after forming as a phantom line. See Fig. 12—I. Internal features such as cutouts or holes shall be shown as solid lines. Features such as electrical connector cutouts, flanged holes, stiffening beads, or dimples may be shown as centerlines indicating the location for the forming tool. The IMI FBI., and CL .13 lines for flanges shall be shown as centerlines. The ONIl. shall be a solid line, .50 in. in length, at each end of the part. See Fig. 12—1. loggle lines shall be hidden lines.
12.3 Bend Instructions
The largest planar surface of the item is usually selected as the principal plane. The flanges of the item are developed from the principal plane. Bend instructions shall he within the principal plane. When the principal plane cannot contain the bend instructions, place the bend instructions outside and adjacent to the principal plane. When the flange to he bent is not apparent, add a note with a leader pointing to the flange to be bent, such as BEND ‘[I uS SURFACE. See Fig. 12-2.
(a) The forming direction shall be indicated by note HLP (Bend Lip) or L1P for flanges formed up from the principal plane, and l31)N (Bend l)own) or l)N for flanges formed dowi from the principal plane.
(Ii) A leader shall be directed from the bend instruction to the CLB, IMI,, or FBL line.
12.4 Flange Angles
Flange angles shall be specified as the number of degrees the Flange is bent from the principal plane of the pattern. An optional method is to indicate the number of degrees the flange is bent from the 0—deg position using the terms OPEN or CIi)SED. A flange bent more than 90 deg from the principal plane o the pattern is a closed angle and a flange bent less than 90 deg is an open angle. See Fig. 12-3.
(1) A flange bent 120 deg from the principal plane shall he specified as CLOSED 3(1.
(2) A flange bent 60 deg from the principal plane shall be specified as OPE\ 3(1.
12.4.1 Flange Angles by Note. Other options such as a note UNSPECIFIED ANGLES ARE 90 may he used, provided clarity is not impaired.
12.4.2 Variable Flange Angles. When the flange angle varies, the angle shall be specified at each end of the flange when the angular change is constant. When the rate of change varies, the flange angle shall be specified at control points. [he flange angle shall he indicated in the bend instructions as NOlEL) ANGLE. See Fig. 12-4.
Joggle instructions shall indicate the direction of forming, depth, and length. IC LIP (Joggle Lip) indicates a flange joggling upward from the callout, and(Joggle Down) indicates a flange joggling downward from the callout. Compensation shall be made in the flat pattern development of joggled flanges for the flow of material.