A sheet metal process is basically a metal forming process, which involves application of external pressure or force on metals to produce thin and flat sheet metal components, generally of the order of few millimeters. Various sheet metal components can be made by using sheet metals, and associated processes.
Some devices made of sheet metal components are:
Check Valve
It is a mechanical device, which allows for uni-directional flow of fluids through it. It consists of two ports, one each, for the entry and exit of fluid. Check valve functions automatically and generally do not need external control systems after initial setup. Check valves are designed on the basis of maximum crushing pressure, which is the minimum value of upstream working pressure for them.
Flapper Valve
A flapper valve is a component of a two piece assembly, which is used to stop and allow the flow of fluid through an orifice or a hole.
Some important sheet metal processes used in the manufacturing of sheet metal components are:
Drawing:
Cylinder-shaped components can be manufactured from sheet metals using punch by pressing the blank into a die cavity.
Deep Drawing:
In this process, the diameter of the workpiece is about half the depth of the itself, and the process is generally done in several steps. The number of draw reductions required is directly proportional to the depth. The process can be done in fewer reductions by softening the workpiece through heating.
Material rolled bidirectionally at rolling mills, are suitable for deep drawing process, as such materials have uniform and finer grain structure, which minimizes the magnitude of residual stresses.
Stretching:
In this process, sheet metal is clamped through its edges and stretched over a die, beyond the elastic limits, which causes permanent deformation of the sheet. The formability of metals is assessed by constructing a forming limit diagram using circle grid analysis. Form block method and mating die method are primarily used in the process of stretching. The process is used for manufacturing aircraft wings, automotive doors and window panels.
Punching:
It is performed by placing the sheet metal on a die, which is then cut using a punch. The ordinary punching process is used to cut out simpler and repetitive shapes with higher efficiency, as compared to laser cutting. A typical CNC multi-spindle punch machine can employ up to 60 tools in a turret that can be rotated to position required tool to the active punching position. A modern CNC punch can execute 600 blows per minute, with very high accuracy.
Cutting:
Cutting sheet metal can be done manually, or using machine tools. CNC machines have found applications in cutting processes, which include CNC Laser cutting, and multi-spindle CNC punching press.
A CNC (Computer Numerical Control) laser comprises a lens assembly with a gas laser beam. Oxygen, nitrogen, or air is fed into the nozzle, which ejects laser beam to cut metal sheets. The quality of edges cut with CNC laser machines can be of the order of 0.1mm, with a cutting speed of 25 meter per minute on 1.2 mm sheet. Generally, the laser cutting systems uses a CO2 based laser source with a wavelength of around 10 micrometer. However, some modern systems use Yttrium Aluminum Garnet (YAG) based laser with a wavelength of around 1 micrometer.
Press Brake Forming:
It is a sort of bending, which is basically employed to bend slender sheet metal components using a press brake. The lower V-shaped groove of the press is called die, on which the punch presses the sheet metal. Air Bending is used commonly to produce sheet metal components. The die used in the process has a steeper angle than the desired bend, on which the metal is pressed down by a controlled punch to bend it through the desired angle. The inner radius of the bend formed in a metal is a function of the radius of the upper tool and the width of the lower die.
CNC and DNC (Direct Numerical Control) machines are also used to monitor the backgauge provided with the sheet metal components. It enables the machine to perform repetitive bending with very high accuracy and speed. CNC machines record the exact coordinates and pressure required for each bending operation, which imparts a 90 degree bend through versatile operations.
Spinning:
Spinning is a metal forming process, in which a disk or tube of metal is formed into an axially symmetric component by rotating it at high speed lathes, and applying force. CNC lathes are used to obtain components with high quality finishes and levels of precision.
