Production Technology Lecture 1 - Sheet Metal Working - 11/11/2024 PDF

‫مرحبا ً بكم في محاضرات‬ ‫‪Production Technology‬‬ ‫(تكنولوجيا االنتاج)‬ ‫الفرقة االعدادية‬ ‫أ‪.‬م‪.‬د‪./‬دمحم فهمى‬ ‫د‪./‬عبدالجواد مطر‬ ‫قسم التصميم الميكانيكي‬ Production Technology  Chapter 4 SHEET METAL WORKING  Contents Introduction Cutting Ope...

‫مرحبا ً بكم في محاضرات‬ ‫‪Production Technology‬‬ ‫(تكنولوجيا االنتاج)‬ ‫الفرقة االعدادية‬ ‫أ‪.‬م‪.‬د‪./‬دمحم فهمى‬ ‫د‪./‬عبدالجواد مطر‬ ‫قسم التصميم الميكانيكي‬ Production Technology  Chapter 4 SHEET METAL WORKING  Contents Introduction Cutting Operations Shearing, Blanking, And Punching Bending Operations V-Bending and Edge Bending Drawing Redrawing Sheet-Metal Operations Not Performed On presses  Introduction 1. Sheet metal working includes cutting and forming operations performed on relatively thin sheets of metal. 2. Typical sheet-metal thicknesses are between 0.4 mm and 6 mm. 3. When thickness exceeds about 6 mm, the stock is usually referred to as plate rather than sheet.  Introduction 4. Sheet-metal processing is usually performed at room temperature (cold working). 5. The exceptions are when the stock is thick, the metal is brittle, or the deformation is significant. 6. These are usually cases of warm working rather than hot working.  Sheet Metal working Terminology “Punch-and-die” Tooling to perform cutting, bending, and drawing “Stamping press” Machine tool that performs most sheet metal operations. “Stampings” Sheet metal products  Advantages of Sheet Metal Parts High strength Good dimensional accuracy Good surface finish Relatively low cost For large quantities, economical mass production operations are available  Cutting Operations Cutting of sheet metal is accomplished by a shearing action between two sharp cutting edges. The shearing action is depicted in the four stop-action sketches As the punch begins to push into the work, plastic deformation occurs in the surfaces of the sheet. As the punch moves downward, penetration occurs in which the punch compresses the sheet and cuts into the metal.  Cutting Operations This penetration zone is generally about one-third the thickness of the sheet. As the punch continues to travel into the work, fracture is initiated in the work at the two cutting edges. If the clearance between the punch and die is correct, the two fracture lines meet, resulting in a clean separation of the work into two pieces.  Cutting Operations Steps of the shearing of sheet metal between two cutting edges: 1. Just before the punch contact’s work; 2. Punch begins to push into work, causing plastic deformation; 3. Punch compresses and penetrates into work causing a smooth cut surface; 4. Fracture is initiated at the opposing cutting edges that separate the sheet..  Shearing, Blanking, And Punching The three most important operations in press working that cut metal by the shearing mechanism just described are shearing, blanking, and punching.  Shearing Shearing is a sheet-metal cutting operation along a straight line between two cutting edges. Shearing is typically used to cut large sheets into smaller sections for subsequent press working operations. It is performed on a machine called a power shears, or squaring shears. The upper blade of the power shears is often inclined, to reduce the require cutting force. Shearing Shearing  Blanking Blanking involves cutting of the sheet metal along a closed outline in a single step to separate the piece from the surrounding stock. The part that is cut out is the desired product in the operation and is called the blank. Blanking  Punching Punching is similar to blanking except that it produces a hole, and the separated piece is scrap, called the slug. The remaining stock is the desired part. Punching  Bending Operations Bending in sheet-metal work is defined as the straining of the metal around a straight axis. During the bending operation, the metal on the inside of the neutral plane is compressed, while the metal on the outside of the neutral plane is stretched. Bending produces little or no change in the thickness of the sheet metal. Bending Operations  Types of Sheet metal Bending Bending operations are performed using punch and die tooling. The two common bending methods V-bending - performed with a V-shaped die Edge bending - performed with a wiping die  V-Bending In V-bending, the sheet metal is bent between a V-shaped punch and die. Included angles ranging from very obtuse to very acute can be made with V-dies. V-bending is generally used for low-production operations. It is often performed on a press brake, and the associated V-dies are relatively simple and inexpensive. V-Bending  Edge-Bending Edge bending involves cantilever loading of the sheet metal. Edge bending is limited to bends of 90◦ or less. More complicated wiping dies can be designed for bend angles greater than 90◦. Because of the pressure pad, wiping dies are more complicated and costly than V-dies and are generally used for high-production work. Edge-Bending Edge-Bending  Drawing Drawing is a sheet-metal-forming operation used to make cup- shaped, box-shaped, or other complex-curved and concave parts. Common parts made by drawing include cans,, cooking pots, and automobile body panels.  Redrawing If the shape change required by the part design is too severe (drawing ratio is too high), complete forming of the part may require more than one drawing step. The second drawing step, and any further drawing steps if needed, are referred to as redrawing. Redrawing  Sheet-Metal Operations Not Performed On presses 1. Stretch forming 2. Roll bending 3. Spinning  1. Stretch Forming Sheet metal is stretched and simultaneously bent to achieve shape change 1. Stretch Forming  2. Roll Bending Large metal sheets and plates are formed into curved sections using rolls  Spinning Basic geometric shapes typically produced by spinning include cups, cones, and tubes. spinning spinning spinning spinning spinning spinning spinning spinning spinning