Mechanical press: operation and features

The mechanical press or industrial press is a machine tool capable of producing large amounts of energy in a controlled manner. Presses are used to deform parts under high pressure, made of different materials such as iron, steel, bronze, copper or aluminium.

What is a mechanical press and how does it work?

For the deformation of parts using high pressure, mechanical presses are used. You can find these conventional machine tools in many companies because of their versatility; they are the most in demand in the automotive and aerospace industries for making car and aircraft parts. They are also present in the manufacture of kitchenware and, of course, in the metalworking industry.

The force a mechanical press uses varies depending on the speed and the magnitude, as well as the striking distance. To give you an idea, the operating principle of a mechanical press is quite similar to hitting a nail with a hammer; in this particular case, the hammer accumulates energy as it accelerates (from the moment it is lifted and throughout its path to the head of the nail). When it touches the surface of the nail, the tool releases a force much greater than the initial force.

In addition, mechanical presses are equipped with an electric motor that is responsible for turning an energy-storing flywheel and that converts circular motion into linear motion. The electric motor, in this case, is what releases the stored energy to apply a great force (of several tonnes) to perform cutting, deformation, forging, stamping or deep drawing of materials and parts. In mechanical presses the motor makes the flywheel turn and convert that rotation into linear motion. When this happens, the electric motor suddenly releases that energy to apply the force of several tonnes for cutting, stamping, forging or deep drawing of materials or parts.

Parts of the mechanical press

Mechanical presses consist of:

• Frame. This mechanical structure serves as the support or body of the machine and provides stability. It must be very solid and robust, because the force used in the press is of great magnitude.
• Connecting elements. These elements allow the assembly and disassembly of the machine and its components.
• Screws and nuts. They work as motion transmission elements.
• Fixing and compression of shock absorbers.
• Electric motor.

Types of mechanical press

There are two main types of mechanical press: crank or eccentric and screw. The crank press is characterised by the use of a connecting rod that is fitted through a crankshaft. It has an upper flywheel that turns driven by an electric motor. When the machine needs to be operated, a clutch connects the flywheel shaft to the crankshaft to apply the force. This type of machine is used mainly for punching and deburring.

The mechanical screw press uses rotational energy from a motor to drive a large screw. These presses are quite similar to hydraulic presses.

In addition to the presses described above, there are also special mechanical presses such as the rack-and-pinion type and the knuckle-joint type. The former uses a gear connected to the drive shaft to operate the electric motor. The rack is a circular gear with an infinite radius and the rotating gear is a pinion that provides force by means of the rack. Knuckle presses, also called combined articulated presses, allow the motor power to be converted through the connecting rod, which makes it easier to transmit the desired power. They have a drive-shaft crank that turns through a full revolution.

Mechanical press or hydraulic press?

What is better for your workshop? A mechanical press or a hydraulic press? Mechanical presses have a fixed stroke length (some can be made with a variable stroke), allow special slide movements (link) and all the parts of the machine (flywheel and parts) are connected to each other. The slide speed is variable and the working energy varies according to the mass and speed of the flywheel. In addition, a mechanical press is very economical and easy to set up and use; on top of that, it is fast and very productive. The drawback of this machine is that it has low pressure and high efficiency, which limits it to machining small parts. It is also very noisy and must be operated by an experienced operator.

The hydraulic press obtains movement and force through hydraulic cylinders filled with a fluid such as oil. The hydraulic press allows better control of the movements of the parts and is used for machining parts with complex shapes. Unlike the mechanical press, the hydraulic press has a variable stroke length, a variable slide speed and offers great precision, performance and repeatability.