Press introduction & Operation
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This document provides an introduction to press working and various press operations used in sheet metal forming. It defines press working as a chipless manufacturing process that uses a press machine to form sheet metal components by applying force. It then describes common cutting operations like blanking, punching, trimming, shaving, notching, nibbling, perforating, parting, and shearing. Forming operations like bending and embossing are also summarized. The document aims to introduce students to basic press working and the different types of operations used in sheet metal manufacturing.
Press introduction & Operation
- 1. Government Engineering College - Bhuj Subject:-Production Technology (2161909) Press introduction & Operation Mechanical Department Prepared By:- Guided By:- BITTU MAKATI (140150119059) Prof. M.M.CHANDRALA
- 2. Introduction Press working has been defined as chipless manufacturing process by which component are made from sheet metal. Press working operation are carried out with the help of a metal forming machine called press which shear or forms the component by applying force. The main features of the press include a frame which supports a ram or a slide , a bed and source of power with a mechanism for operating the ram inline or at right angles to the bed. The ram is equipped with a punch or a set of punches which have the shape of the job to be produced while a die block is attached to the bed. Workpieces are produced or formed as the punch descends onto the die block. In most cases processing of sheet metal is done in cold state. Material like magnesium may sometimes be heated slightly to make them more workable. Press tool operation of sheet metal is by far the cheapest and fastest method to complete manufacturing of component
- 3. Press working cutting operation In cutting operation the work piece is stressed beyond its ultimate shear strength and cut off into piece. In forming operation the stresses applied are below the ultimate shear strength of the material. As such there is no cutting of the metal only the contour of the work piece is changed to the desired shape.
- 4. Common cutting operation using dies and punches include the following:- 1. Blanking 2. Punching 3. Trimming 4. Shaving 5. Notching 6. Nibbling 7. Perforating 8. Parting 9. shearing
- 5. Blanking & Piercing Blanking and piercing are shearing processes in which a punch and die are used to modify webs. The tooling and processes are the same between the two, only the terminology is different: in blanking the punched out piece is used and called a blank; in piercing the punched out piece is scrap. The process for parts manufactured simultaneously with both techniques is often termed "pierce and blank." An alternative name of piercing is punching.
- 6. Trimming The trimming operation is the last operation performed because it cuts away excess or unwanted irregular features from the walls of drawn sheets Shaving The shaving process is a finishing operation where a small amount of metal is sheared away from an already blanked part. Its main purpose is to obtain better dimensional accuracy, but secondary purposes include squaring the edge and smoothing the edge. Blanked parts can be shaved to an accuracy of up to 0.025 mm (0.001 in)
- 7. Notching A shearing operation that removes a section from the outer edge of the metal strip or part.
- 8. Lancing Lancing is a piercing operation in which the work piece is sheared and bent with one strike of the die. A key part of this process is that there is not reduction of material, only a modification in its geometry.
- 9. Nibbling The nibbling process cuts a contour by producing a series of overlapping slits or notches. This allows for complex shapes to be formed in sheet metal up to 6 mm (0.25 in) thick using simple tools. Punches are available in various shape and sizes; oblong and rectangular punches are common because they minimize waste and allow for greater distances between strokes, as compared to a round punch. Nibbling can occur on the exterior or interior of the material, however interior cuts require a hole to insert the tool
- 10. Perforating Perforating is a piercing tooling that involves punching a large number of closely spaced holes. Parting Parting is a operation in which metal is cut simultaneously along two parallel lines or contour in such a way that the side thrust in neutralised.
- 11. Bending Bending means deforming a flat sheet along a straight line to form the required angle. Various sections like angles, channels etc., are formed by bending, which may then be used for fabrication of steel structures. Three common methods of bending are illustrated in Fig.
- 12. Embossing In embossing, impressions are made on sheet metal in such a manner that the thickness of the sheet remains uniform all over even after embossing has been done. It means that if one side of the sheet is raised to form a design, there is a corresponding depression on the other side of the sheet. Basically it is a pressing operation where not much force is needed. The sheet is spread on the bottom die and the stroke of the punch is so adjusted that, when it moves down to its lowest position, it leaves a uniform clearance between the impressions carved in the punch and the die which is equal to the thickness of the sheet being embossed.
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