What is a Press Machine?
A press machine (including punch presses and hydraulic presses) is a precision-engineered, versatile machine used for processing materials such as metals, plastics, and rubber by applying force to form them into desired shapes or sizes. Press machines typically consist of a frame, a slide, a pressing device, and a control system, and are widely used for processes like cutting, punching, blanking, bending, riveting, and forming.
- Punch press: A type of stamping press machine, classified based on the working principle into mechanical punch presses (tiltable, fixed table, and deep throat), hydraulic punch presses, and pneumatic punch presses.
- Hydraulic press: A machine that uses liquid as a working medium and is based on Pascal's principle to transfer energy for various processes. Hydraulic presses generally consist of the mainframe, power system, and hydraulic control system. There are many types of hydraulic presses, each designed and customized according to the workpiece and process requirements.
The Operating Principle of Press Machines
The basic principle of a hydraulic press is that the oil pump delivers hydraulic oil to an integrated cartridge valve block, which distributes the oil to the upper or lower chamber of the cylinder through various check valves and relief valves. Under the action of high-pressure oil, the cylinder moves. Hydraulic presses use liquid to transmit pressure, following Pascal's law in a closed container.
The design principle of a punch press is to convert rotary motion into linear motion. The main motor drives the flywheel, and the clutch drives the gears, crankshaft (or eccentric gear), and connecting rods. This achieves linear motion of the slide, with the motion from the main motor to the connecting rod being rotary. There is a transition point between the connecting rod and the slide for the change from rotary to linear motion. There are roughly two types of mechanisms designed for this purpose: one is spherical, and the other is pin-shaped (cylindrical), both of which convert the rotary motion into linear motion of the slide.
Applications of Press Machine
Press machines are extensively used in processes such as cutting, punching, blanking, bending, riveting, and forming. By applying significant pressure to metal workpieces, metals undergo plastic deformation and fracture to be processed into parts.
Universal press machines used for sheet metal stamping are suitable for punching and blanking, bending, flanging, and shallow drawing stamping operations. They have a wide range of applications in industries such as watches, toys, cutlery, telecommunications equipment, instruments, motors, electrical appliances, tractors and automobile manufacturing, daily hardware, and radio components.
- Metal Processing: Press machines play a vital role in the field of metal processing. They are used for metal stamping, stretching, bending, and forming processes to make automobile parts, home appliance casings, mechanical parts, etc. For example, the stamping and forming of automobile bodies and the processing of metal casings for machinery equipment are all dependent on press machines.
- Plastic Processing: In the plastic industry, press machines are widely used in injection molding, compression molding, and other processes. Press machines can process plastic materials into various shapes of products, such as plastic containers, pipes, parts, etc., which are used in fields like automotive, home furnishings and more.
- Rubber Processing: Press machines are also used in the molding process of rubber products, such as the production of tires, seals, rubber pads, etc. By applying pressure and heat in the press machine, rubber materials can be shaped into products of various shapes and sizes to meet the needs of different industries.
- Mold Manufacturing: Press machines play a critical role in the process of mold manufacturing. By using press machines to shape, trim, and process mold materials, high-precision molds for die casting, injection molding, and stamping processes can be manufactured, ensuring the quality and efficiency of industrial production.
Classification of Press Machines
Press machines can be classified into various types based on their working principles and structural features.
In terms of structure, they are mainly divided into: four-column, single column (C type), horizontal, frame type, gantry, and universal hydraulic press, etc.
In terms of usage, they are mainly divided into metal forming, bending, stretching, punching, powder (metal, non-metal) forming, press-fitting, extrusion, etc.
- Hot Forging Press Machine
Large forging press machines capable of completing various free forging techniques are one of the most widely used equipment in the forging industry. At present, there are forging press machines in series specifications such as 800T, 1600T, 2000T, 2500T, 3150T, 4000T, 5000T, etc.
- Four-Column Press Machine
This press machine is suitable for pressing processes of plastic materials, such as powder product molding, plastic product molding, cold (hot) extrusion metal forming, thin plate stretching, and processes like transverse pressure, bending, turning, correction, etc. Four-column press machines can be divided into four-column two-beam press machines, four-column three-beam press machines, four-column four-beam press machines, etc.
- Single Arm Press Machine (Single Column Press Machine)
It can expand the working range, utilize three-dimensional space, and extend the stroke of the hydraulic cylinder (optional), which can be extended from 260mm to 800mm. It also can preset the working pressure and has a hydraulic system cooling device.
- Gantry Press Machine
It can assemble, disassemble, straighten, roll, stretch, bend, and punch machine parts, truly realizing multi-purpose use. The machine table can move up and down, which enlarges the machine's opening and closing height and makes it more convenient to use.
- Frame Type Press Machine
Frame type press machines have a good rigidity structure. The slider adopts a four-corner eight-face guide rail guide, which has high adjustment precision and strong anti-offset load capacity. This machine has a fast downward speed of the slider, a large worktable, and a reverse stretching function of the upper slider and the lower hydraulic pad. It has a wide range of processes and can complete the stretching, punching, bending, and flanging of metal thin plates. It is especially suitable for parts in the automotive industry, such as steel rings, bodies, bridge shells, chassis, doors, etc.
- Horizontal Press Machine
The horizontal press machine is a multifunctional machine tool with a horizontally acting hydraulic cylinder head. By replacing different molds, it can perform operations such as shearing, bending, pipe bending, and punching. It adopts double column guidance and double sliding blocks for fixture installation, which is suitable for the press-fitting of spline shafts or flange discs of various types of automotive drive shafts. The equipment is simple to operate, responsive, and offers high concentricity precision in press-fitting. The main body of the horizontal press machine is made of cast steel to ensure that the equipment does not deform. It features an independent hydraulic system and a movable control box, making it convenient for workers to operate, reducing labor intensity, and allowing for easy and quick interchange of fixtures.
Purchasing Considerations for Press Machines
Purchasing a press machine is an important decision that requires consideration of multiple aspects. Here are some considerations to keep in mind:
- Process Requirements: First, clarify your process requirements, including the type of material to be processed, the processing technology, product size, and shape. Different types of press machines are suitable for different processing techniques and materials. Ensure that the chosen press machine can meet your process requirements.
- Processing Capability: Consider the processing capability of the press machine, including maximum pressure, maximum stroke, table size, and other parameters. Based on your processing needs, select a machine with suitable capabilities to ensure that it can meet production requirements.
- Quality and Reliability: Opt for a press machine brand and model that offers good quality and reliability, which can reduce the rate of malfunctions and increase production efficiency. You can assess and compare based on the reputation of the press machine manufacturer, customer reviews, and product quality certifications.
- Safety: Pay attention to the safety features of the press machine, including safety guards, emergency stop buttons, safety limits, and other functions. Ensure that the press machine complies with local safety standards and regulatory requirements to protect the safety of operators.
- After-sales Service: Choose a press supplier with a good after-sales service system, including timely technical support, spare parts supply, maintenance, and other services. Ensure that you can get timely help and support during use to minimize production interruptions and losses.
Maintenance of the Press
Proper use of press equipment, careful maintenance, and strict adherence to safety operating procedures are essential conditions for extending the life of the equipment and ensuring safe production. Therefore, in addition to being familiar with the structure and performance of the press, operators should pay attention to the following points:
- The debugging and repair of the hydraulic station require professionals. When disassembling hydraulic components, parts should be placed in a clean area. Sealed surfaces should not have scratches.
- Hydraulic oil is the energy transmission medium when the hydraulic station operates. The quality, cleanliness, and viscosity of the hydraulic oil play a leading role in the lifespan of hydraulic pumps, hydraulic valves, and hydraulic cylinders. Therefore, the quality of the hydraulic oil should be highly valued, and its cleanliness maintained when using the hydraulic station. The hydraulic oil used in the system must be strictly filtered, and oil filters should be installed in the hydraulic system of the press.
- Under the condition of ensuring the normal operation of the system, the pressure of the hydraulic pump should be adjusted as low as possible, and the pressure of the back pressure valve should also be minimized to reduce energy loss and overheating.
- To prevent dust and water from entering the oil, the area around the oil tank should be kept clean and maintained regularly.
- The liquid level in the press's oil tank should be kept sufficiently high to ensure enough circulation and cooling conditions for the oil in the system. Pay attention to keeping the oil tank, oil pipes, and other equipment clean to facilitate heat dissipation. Generally, a safe temperature for oil is between 30°C and 55°C, which is the most appropriate operating temperature for optimal performance and longest life. If the oil temperature exceeds 60°C, its lifespan will halve for every 8°C increase.
- Efforts should be made to prevent the pressure in all parts of the system from being lower than atmospheric pressure. Good sealing devices should be used, and seals should be replaced promptly when they fail. All stressed screws, such as cylinder head guide screws and piston rod flange screws, should be tightened regularly to prevent loosening and to prevent air from entering the hydraulic system or oil leaks.
- Systems with water coolers should maintain sufficient cooling water and unobstructed pipelines. Systems with air coolers should ensure smooth ventilation to prevent oil temperature from getting too high.
- Systems with filters should regularly clean or replace the filter elements (about once a month) to prevent blockages and rapid rise in oil temperature, which can cause serious damage to hydraulic components or oil pump rupture.
- The working pressure of the system is determined by adjusting the pressure valve to set the output pressure of the hydraulic pump. Generally, the set pressure should not exceed the original designed rated pressure; otherwise, it may cause damage to the hydraulic pump, hydraulic valve seizure, or motor burnout, among other issues.
- To ensure reliable operation of the press, it is recommended that users replace certain components of the press after they reach the end of their service life.
Record the main issues resolved and unresolved during maintenance for filing, to serve as a basis for the next maintenance or for planning repair schedules.
Precautions for Operating the Press
During the operation of the press, the following safety operating procedures must be adhered to:
- Individuals who are not familiar with the machine's structure, performance, or operating procedures should not start the press on their own.
- Maintenance and mold adjustments should not be performed while the machine is in operation.
- If the press is found to have serious oil leaks or other abnormalities (such as unreliable action, excessive noise, vibration, etc.), it should be shut down to analyze the reasons and attempt to eliminate them. It must not be put into production with faults.
- Overloading or exceeding the maximum eccentric distance is forbidden.
- It is strictly prohibited to exceed the maximum stroke of the slider; the minimum mold closed height should not be less than 600mm.
- Electrical equipment must be grounded firmly and reliably.
At the end of each day's work, lower the press slide to its lowest position.
