What is Metal stamping – Stamping of sheet metal
What is Metal stamping – Metal Stamping machine
Sheet metal working processes are cold working processes in which forming and related operations are performed. In sheet metal operation the surface area-to-volume ratio of the starting metal is high. This ratio distinguished the sheet metal operation from bulk deformation. Often it is called press working because the machines used to perform these operations are pressed. A part produced by sheet metal operation is often called stamping.
The tools used to perform stamping operation are a set of tools called punch (smaller members) the upper half and a die (larger member) the lower half. The sheet metal is placed in between the two die halves. When the two die halves are brought together the punch enters the die and part/s is/are produced. Punch has a shape that corresponds to that of a die but is smaller by an amount determined by the required punch die clearance. Again the punch die clearance is determined by the type and thickness of the material and the operation to be
Stamping of sheet metal involves cutting or shearing, bending or forming, and drawing or deep-drawing operations. A detail of all the process has been given below.
Blanking or piercing: It involves cutting of the sheet metal along a close outline in a single step to separate the piece from the surrounding stock.
Forming: This operation produces one or more plane surfaces that are at an angle to the original or flat plane of the blank. Any change either small or big is classified as forming.
Drawing: Forming of a flat metal sheet into a hollow or concave shape, such as a cup, by stretching the metal is known as drawing.
Shaving: It is a secondary operation after blanking or piercing operation. It produces a smooth edge on the work piece instead of the breakaway edge. This is achieved by removing a small amount of stock from the edge of the part.
Trimming: It is similar to blanking but, it occurs after forming, drawing, or other operations when extra metal is left in the part for holding or locating purpose or as stock allowance. The removal of this extra stock is called trimming.
Embossing: It is used to create indentation in the sheet such as raised or depressed area with little or no change in material thickness. Making of nameplates and stiffening ribs are two applications
Coining: It permits different designs to be imparted on either side of a blank. The blank is entirely captive in the die. Indentation results in thinning of the sheet metal and the raised sections result in thickening of the metal.
Swaging: This process uses an open die. The part is also squeezed into cavity but in contrast to coining, the excess material is not contained but allowed to flow at will.
Characteristics and application of metal stamping
If the parts are designed properly, then this can contribute significantly to design for manufacturability (DFM). Other parts can be reduced by incorporating diverse function to the selected parts. Springs and other flexible sections, snap-fit elements, folding tabs, and pressfixable designs can be incorporated and can eliminate the need for other parts, including separate screw fasteners or other fasteners. Projection welding and spot welding are easily provided. Such innovations can reduce the number of parts in an assembly and make the stamped part itself easy to assemble.
Perhaps the major characteristic of all stamped metal parts are of uniform wall thickness with few exception. The wall thickness ranges from a low of about 0.025 mm to about 20 mm, although pure bending or shearing operations are produced on even heavier stock. Most stamping, however, is performed in the range of about 1.3mm to 9.5mm stock thickness. The size of metal stampings ranges from the smallest parts used in wrist watches to large panels used in trucks or aircraft. The largest press brakes are as long as 9 m
In order to minimize die cost, the following guideline should be followed while designing parts for stamping manufacturing process:
- Minimize the number of distinct features in a part.
- Avoid closely spaced feature.
- Avoid the use of narrow cutouts and narrow projections.
- Minimize the number of bend stages in a part.
- Bend angles greater than 90° should be avoided if possible.
- Avoid side action feature.