Metal forming is the process of using active power to deform metal materials and obtain the required shaped parts within the limit of tooling and dies.
Metal forming parts mainly include forgings, stamped parts, and sheet metal parts, which consume 70% of the total amount of metal materials such as sheet metal, pipes, bars, wires, and profiles.
The entire metal forming industry employs over 10 million people and creates 2 trillion yuan of industrial added value annually. It also purchases 80 billion yuan of forming technology and equipment while consuming 100 billion yuan of tooling.
In the three metal forming industries of forging, stamping, and sheet metal making, production processes, technical equipment, tooling, and raw materials are indispensable. Among these, the metal forming machine-based technical equipment provides forming energy, playing a key role in ensuring product quality, improving production efficiency, reducing labor costs, controlling production costs, and promoting environmental protection, energy-saving, and sustainable development.
In today’s era, network, information, and intelligence not only change our work and lifestyle but also subvert the manufacturing and metal forming industry. Therefore, the construction of automation, information, and intelligence in metal forming enterprises is an urgent task, and the adoption of intelligent machine tools is a prerequisite for the use of automatic production, the construction of information chemical plants, and the realization of intelligent manufacturing.
Without intelligent machine tools, it is difficult or impossible to realize the automation, informatization, and intelligence of enterprises. Therefore, it is essential for metal forming enterprises to adopt intelligent machine tools or carry out the intelligent transformation of machine tools.
In an intelligent metal forming machine, intellectualizing the main drive is crucial.
The key to achieving an intelligent main drive in metal forming machines is through the use of a servo main drive.
This article analyzes and provides insight into the servo mode of the main driving mode of metal forming machine tools in forging, stamping, and sheet metal manufacturing industries. By doing so, each metal forming machine tool enterprise can plan its own development direction, assist each metal forming parts manufacturing enterprise in choosing the appropriate machine tools, improve product quality, reduce production costs, and improve their overall competitiveness.
As metal forming machine tools continue to evolve, it is essential for forging machine tools, stamping and sheet metal making machine tools, mechanical machine tools, and hydraulic machine tools to develop in the direction of servo main drive.
The advantages of using a servo drive in metal forming machines have been fully proven by the production practices of various industries. A servo-driven metal forming machine not only boasts good processability but also energy efficiency, automation integration, information networking, and intelligent control. It is a necessity for future metal-forming enterprises.
Among the four kinds of forming machine tools for forging production, the forging hammer has evolved from steam-driven and air-driven to the most commonly used electro-hydraulic drive.
Some machine tool enterprises have developed the mechanical servo-driven forging hammer (Fig. 1), which completely subverts the concept of a traditional forging hammer that uses fluid medium transmission. It is a revolutionary change in the driving mode of the forging hammer.
The screw press has evolved from flywheel friction drive to the most commonly used frequency conversion (or permanent magnet) motor direct drive. Currently, some enterprises have developed a mechanical servo-electric direct drive mode (Fig. 2), which has higher efficiency and better performance.
The mechanical press, commonly known as a die forging press, also has an upgraded drive motor from the ordinary asynchronous AC motor to the servo motor drive mode (Fig. 3). This eliminates the deceleration and braking structure, making the press structure simpler, easier to maintain, and even cheaper.
However, it is challenging to manufacture heavy forging machine tools at present due to the restriction of servo motor power.
The forging hydraulic press has evolved from a traditional hydraulic press to the most commonly used hydraulic press. Additionally, the hydraulic press has also advanced from the traditional servo valve control mode (with accumulator) to the servo pump control mode (without accumulator) (Fig. 4), greatly improving the energy efficiency and stroke times of the hydraulic press.
Compared to the mechanical press, the hydraulic press has a better comprehensive competitiveness.
Furthermore, the forging machine, roll forging machine, and cross wedge rolling mill also adopt the mechanical servo direct drive mode (Fig. 5 and Fig. 6), with simple structure, easy manufacturing, low energy consumption, and superior performance.
Fig. 1 Mechanical servo linear hammer
Fig. 2 Mechanical servo screw press
Fig. 3 Servo cold forging press
Fig. 4 Hydraulic servo cold forging press
Fig. 5 Servo roll forging machine
Fig. 6 Servo cross wedge mill
Among the two main types of forming machine tools in stamping production, the servo drive of the mechanical press (Fig. 7, Fig. 8, Fig. 9, and Fig. 10) will gradually replace the traditional asynchronous motor drive, thus completing a revolution in stamping machine tools and production technology.
In the stamping industries of Europe, the United States, and Japan, the mechanical servo press has already been widely used. It has been reported that top stamping machine companies worldwide, such as Schuler and Komatsu, no longer recommend the use of traditional mechanical presses for large press users.
According to information from the China Forging Association, the stamping workshop of the main engine plant of the joint venture of the world’s top automobile companies in China will also discontinue the use of traditional mechanical press in the future.
The hydraulic servo direct drive technology of hydraulic press (Fig. 11) will also promote the technical reform of hydraulic press, reduce energy consumption, improve the impact times, and further improve the comprehensive performance of the hydraulic press. This will broaden the application scope of the hydraulic press.
The fine blanking press is developing from a servo valve-controlled hydraulic press (with an accumulator and large oil tank) to a servo pump-controlled hydraulic press (without accumulator, only with a small oil tank) and even to a mechanical servo drive (currently only used for small presses below 200t).
The development ideas of hot stamping press and fine blanking press are the same. They are also developing from a valve-controlled hydraulic press to a pump-controlled servo drive mode and even to a mechanical servo drive mode (Fig. 12 and Fig. 13).
Fig. 7 Servo single point press
Fig. 8 Servo two point press
Fig. 9 Double servo multi station press
Fig. 10 Servo press
Fig. 11 Hydraulic servo press
Fig. 12 Servo fine blanking machine
Fig. 13 Servo hot stamping press
Among the two major types of machine tools for sheet metal processing, the CNC punch has undergone significant developments. It started from the rudimentary step punch and progressed to the mechanical CNC punch, followed by the hydraulic servo CNC punch. Finally, it evolved into the most popular mechanical servo CNC punch (FIG. 14). This development has not only made the CNC punch more energy-efficient, but it has also reduced vibration and noise while greatly enhancing its adaptability.
The CNC punch can not only be used for blanking, but it can also achieve more sheet forming, improve the service life of the die, and strengthen its own process advantages when compared to laser cutting. The development of numerical control punch has been rapid, and in just a few decades, four generations of CNC punch have changed. It is exciting to think about what the future of CNC punch will look like.
Another key machine tool for sheet metal processing is the CNC press brake machine, which has also undergone significant development. In just a few decades, it progressed from CNC hydraulic to CNC hydraulic servo press brake machine and finally to the widely used CNC servo hybrid press brake machine of today (FIG. 15). This machine is not only environment-friendly and energy-saving, but its technology is also good, making it easy to realize automation and intelligent production.
It is also important to note that the use of CNC mechanical servo drive (Figure 16) has become a trend in small CNC press brake machines. Compared to the previous generations of press brake, the servo hybrid press brake has simpler drive structure, making it easier to maintain and manufacture at a lower cost.
Fig. 14 Servo CNC punch
Fig. 15 Hybrid drive press brake machine
Fig. 16 Servo press brake machine
The two major types of machines for forming metal tubes and wires are tube bending machines and wire bending machines. These machines have evolved from the early hydraulic main drive and hydraulic servo feed systems to the pure mechanical servo main drive and mechanical servo feed systems, and are now available in fully electric modes (see FIG. 17 and Figure 18).
As a result, the machine structure has become simpler, making it easier to achieve automation and maintenance, and ensuring safe and reliable operation. Additionally, these machines can achieve energy savings and green production.
Fig.17 Fully electric pipe bending machine
Fig. 18 All-electric multifunctional forming machine
Overall, the main driving force behind the metal forming machine is the servo, which improves the equipment’s performance and technology. This makes it more suitable for automatic production, information management, and data diagnosis.
Additionally, it is more energy-efficient, environmentally friendly, and promotes sustainable development while being beneficial to humans.
Among them, the mechanical servo direct drive is considered the most advanced mode of operation. However, due to limitations posed by servo control systems, servo motor manufacturing technology, and costs, it is still challenging for large metal forming machines to adopt mechanical servo direct drive.
Therefore, a mechanical transmission structure is still required between the motor and the slider. Nonetheless, the components are rigidly connected mechanically, ensuring high energy transfer efficiency, accurate motion control, simple structure, and easy manufacturing and maintenance.