How does mechanical press work?

Reshaping a metal workpiece via deformation

In metalworking, forming is the fashioning of metal parts and objects through mechanical deformation; the workpiece is reshaped without adding or removing material, and its mass remains unchanged. Forming operates on the materials science principle of plastic deformation, where the physical shape of a material is permanently deformed.

Characteristics

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Metal forming tends to have more uniform characteristics across its subprocesses than its contemporary processes, cutting and joining.

On the industrial scale, forming is characterized by:

• Very high loads and stresses required, between 50 and

  2500 N/mm2

  (

  7-360 ksi

• Large, heavy, and expensive machinery in order to accommodate such high stresses and loads
• Production runs with many parts, to maximize the economy of production and compensate for the expense of the machine tools

Forming processes

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Forming processes tend to be categorised by differences in effective stresses. These categories and descriptions are highly simplified, since the stresses operating at a local level in any given process are very complex and may involve many varieties of stresses operating simultaneously, or it may involve stresses which change over the course of the operation.

Compressive forming involves those processes where the primary means of plastic deformation is uni- or multiaxial compressive loading.

• Rolling, where the material is passed through a pair of rollers
• Extrusion, where the material is pushed through an orifice
• Die forming, where the material is stamped by a press around or onto a die
• Forging, where the material is shaped by localized compressive forces
• Indenting, where a tool is pressed into the workpiece

Tensile forming

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Tensile forming involves those processes where the primary means of plastic deformation is uni- or multiaxial tensile stress.

• Stretching, where a tensile load is applied along the longitudinal axis of the workpiece
• Expanding, where the circumference of a hollow body is increased by tangential loading
• Recessing, where depressions and holes are formed through tensile loading

Combined tensile and compressive forming

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This category of forming processes involves those operations where the primary means of plastic deformation involves both tensile stresses and compressive loads.

Bending

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This category of forming processes involves those operations where the primary means of plastic deformation is a bending load.

Shearing

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This category of forming processes involves those operations where the primary means of plastic deformation is a shearing load.

Notes

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References

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• Lange, Kurt, ed. (1985). Handbook of Metal Forming. McGraw-Hill, Inc. on behalf of the Society of Manufacturing Engineers. ISBN 0872634574.

See also

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A mechanical press is a machine press that is primarily used for forming sheet metal and metal extrusion. The working principle of the mechanical press is to convert the rotational force from the electric motor to a translational force that drives the mechanism of pressing work.

What Is a Mechanical Press?

A mechanical press is a machine press that is primarily used for forming sheet metal and metal extrusion. Press machines are the classic and common machine tools that can be basically divided into a hydraulic press and mechanical press. The press working is an essential modern metal fabrication process across industries. The mechanical press is not only used for sheet metals but also used for manufacturing plastic products and a variety of machining operations such as broaching. Machine presses including mechanical press and hydraulic press all require a great amount of output force to complete the metalwork, for example, to deform a considerable piece of metal. The type of energy source, the manner, and nature where the machine press will transfer the energy vary, define the efficiency as well as the output the machine tool can provide. 

In a vertical mechanical press machine, the force vector works upward and downward relative to gravity. In other cases, the same machine type is mounted horizontally where the working force is applied to the path perpendicular to the direction of the gravity. The working principle of the mechanical press is however the same no matter that the force is exerted vertically, horizontally, or at the intermediate angle.

How Does Mechanical Press Work?

In short, the working principle of the mechanical press is to convert the rotational force from the electric motor to a translational force which drives the mechanism of pressing work. The energy source of the mechanical press machine is typically a motor. Using a mechanical press machine, there are 3 main steps to complete the metal forming process. The production cycle begins with the material placed on the dies where the metal sheet or other raw materials should stay in place for machining. The operators should then manipulate the mechanical press to apply appropriate pressure in order to force and shape or alter the raw materials as they need. Subsequently, the finished products will be ejected and collected from the mechanical machines.

All components in a mechanical press require to be lubricated through the internal system, in general, which supplies a stable flow of lubricants to ensure smooth movement during the pressing process. In general, mechanical presses are large machine tools that might be dangerous to some degree. The operations require workers with proper training and safety procedures. The proper range of the stroke is also vital when performing metalworking using a mechanical press machine.

:: Read more: What Makes Mechanical Press Machines So Impressive?

Why Use a Mechanical Press?

The mechanical press has numerous benefits when performing metal shaping. For starters, the metal forming cycles performed in a mechanical press are typically more rapid than one in a hydraulic press. Unlike other types of machine press, the application of force in a mechanical press can vary from speed and magnitude throughout the stroke length.

Among different styles and sizes of machine presses, the mechanical press is widely chosen to use in metal forging production as well as sheet metal forming. On top of that, a mechanical press is also ideal for impact extrusion applications where the rapid and consistent application of force can be fully utilized over a preset distance. The most effective and powerful mechanical press machine nowadays perhaps is the one having the capacity of approximately 12,000 tons.

Following are some subtypes of mechanical press that can provide a wide range of metal machining jobs for specific applications. The subtypes of the mechanical press include but are not limited to the stamping press, the screw press, the punch press, the press brake, and more. The mechanical punch press is primarily used to form holes repeatedly under a great amount of pressure. The mechanical screw press is also called the fly press, utilizing the ram which is driven upward and downward by the screw to shape the metal pieces through the dies. The mechanical stamping press is also a classic press which consists of a press frame, a ram, and a bolster plate. 

The stamping press also employs the die to deform and cut the metal parts. As for the mechanical press brake, it is a special style of press machine that can be used to bend the metal parts into desired profiles. In a press brake, the bending force can be up to 3000 tons. Some common applications of this mechanical press include the production of the back-plate of a computer case, the frame pieces, and the electronic enclosures. Some of the CNC mechanical press brakes can even perform the metal forming work with excellent accuracy to a fraction of 1 mm. 

:: Read more: What is the Automatic Power Press?

Mechanical and Hydraulic Press

Mechanical and Hydraulic press are two widely-used types of machine press in the modern metalworking industry. Both of the types can be applied to a wide range of materials and use, however, the power which drives the mechanism and the delivering methods of the energy is different. In a hydraulic press machine, the movements are forced by the pumps and cylinders and also the working fluids while the mechanical press simply completes the pressing process through mechanical components. 

Both mechanical and hydraulic press have their individual strengths and also disadvantages. To compare the two, the mechanical press is more energy-efficient, economical, and also has more rapid production cycles. The programmable motions also enhance the precision during the forming process. On the other hand, the hydraulic press typically takes up less room compared to a large mechanical press machine which has the same press capability. The hydraulic press is popular for the ability to manufacture more intricate shapes and also be economical with materials during a high volume metal forming production.

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