The development trend of high-speed precision press
The continuous increase in the number of strokes of high-speed presses has greatly improved production efficiency and reduced costs. Benefiting from the strong market demand for standardized, serialized, and batch-oriented functional stamping parts, the thickness of stamping parts is gradually reduced, and the required stamping tonnage is gradually reduced, which creates conditions for high-speed presses to increase the number of strokes. In addition, the development of high-speed precision stamping dies, especially multi-station high-precision progressive dies and automated peripheral equipment, has also created conditions for high-speed presses to increase the number of strokes. From the development history of high-speed presses, as the number of strokes increases by leaps and bounds, its nominal force and stroke show a decreasing trend.
⑵High rigidity and high precision.
Hard alloy molds are mostly used on high-speed presses, and the relative displacement of the concave and convex molds in the horizontal plane must be reduced to a minimum. The high-speed presses are required to have a certain level of rigidity. Due to the “reverse load” of the high-speed press, it is required to further increase its vertical rigidity. Usually adopt reasonable structural design and increase the design margin (increase the size of parts such as crankshaft, pin or ball joint) to ensure it.
High precision refers to high static geometric accuracy and dynamic accuracy (bottom dead center accuracy). The static geometric accuracy is related to the manufacturing level of the high-speed press, and the dynamic accuracy is achieved by adopting temperature control and bottom dead center dynamic compensation mechanism. In terms of static geometric accuracy, the Japanese Industrial Standards Super Precision Standard (JIS B 6402:1997) is basically the minimum standard, and the internal control standards of foreign companies have been greatly compressed on this basis.
⑶ The upper transmission is dominant.
The moving method of uploading has the advantages of lighter weight of moving parts, good layout, convenient maintenance, etc. It has become the mainstream method of high-speed presses and is widely adopted by domestic and foreign manufacturers. It is carried out in the aspects of transmission mechanism, guiding method, and dynamic balance mechanism. A lot of innovation. High-speed presses with lower drive mode only occupy a place in certain areas.
⑷ Closed structure will dominate.
With the further improvement of the accuracy of hedging products, the use of closed structures is an inevitable trend. On the one hand, the closed structure has a large space for the installation of dynamic balancing devices, which is beneficial to increase the number of strokes (super high-speed presses from 3000 to 4000 spm are closed structures), thereby improving production efficiency; on the other hand, the closed structure has good rigidity, It can improve the precision of punching products and the service life of molds. In addition, the use of a closed structure can increase the width of the worktable and facilitate the use of multi-station progressive dies.
⑸ The dual-point structure gradually develops towards multiple points.
Closed high-speed presses are mostly of double-point structure. With the increase of stamping die stations and the size of stamping products, it is required to widen the working table and increase the punching force. The use of double-point structure requires further enlargement of the slider and guide Stiffness. Therefore, many companies adopt a three-point or four-point structure, and the auxiliary guide adopts a cylindrical type, which can not only reduce the weight of the slider, but also increase the number of strokes.
⑹Using new materials.
As the accuracy requirements for high-speed presses continue to increase, new materials are continuously being used. The main purpose is to reduce the weight of moving parts, reduce the impact of temperature changes on the bottom dead center, and improve the load-carrying capacity under the premise of ensuring rigidity. The new materials used mainly include:
1) Low density materials. Some of the high-speed presses of American OAK Company use super-hard aluminum alloy for the slider, which reduces the weight by 60%; the 100kN, 4000spm ultra-high-speed press of Nidec Kyori Co., Ltd. uses ceramic-aluminum alloy composite material for the slider. The inertial force of the moving parts of the slider is reduced by 40%, reducing the impact of changes in the number of work on the accuracy of the bottom dead center.
2) Low expansion coefficient materials. The U-series high-speed press from ISIS, Japan, the main drive components and couplings are all alloy castings with low thermal expansion coefficient Nobinate-5 (Ni content 36%, Co content 6%), and its thermal expansion coefficient is only 1/4 of steel ~1/3, the hardness is equivalent to FCD45-50. In addition, some companies use Invar alloy with a smaller coefficient of linear expansion as the sliding bearing material to reduce the impact of thermal deformation on the accuracy of the bottom dead center.
3) Other special materials. With the increase in the number of strokes of high-speed presses, special materials are gradually used in the sliding support or guiding parts. For example, babbitt alloy with better friction performance is used for sliding friction parts; high-strength brass or beryllium bronze is used for parts bearing large impact loads such as bowls.
⑺Using high-precision bearings.
Rolling bearings are in line contact when subjected to impact loads and have poor rigidity. Especially when they are under heavy load, the bottom dead center accuracy will be unstable, so they are mostly used for medium and small tonnage high-speed presses. The development trend of rolling bearings is to further improve accuracy and focus on the perfect combination with high-speed presses.
The sliding bearing is surface contact with high rigidity, which is beneficial to the stability of the bottom dead center accuracy. With the continuous improvement of the overall manufacturing accuracy of high-speed presses, and the use of oil temperature control and large-flow lubrication systems, the heating of sliding bearings has been effectively resolved, and they have been gradually reused in high-speed and ultra-high-speed presses. The development trend of sliding bearings is to apply new materials and further improve manufacturing accuracy.
Japan AIDA company uses composite bearings (rolling bearings + sliding bearings). When stamping, the sliding bearings work and have high rigidity; when not stamping, the rolling bearings work and the friction is significantly reduced, which is beneficial to high-speed operation.
The efficiency and accuracy of punching products are not only related to the high-speed precision press itself, but also related to its supporting peripheral equipment and molds. Many manufacturers have begun to pay attention to peripheral equipment and molds and incorporate them into their business scope. In addition, the use environment is also taken into consideration. On the one hand, it is the problem of stamping noise protection, on the other hand, it is the impact on accuracy. Moreover, some manufacturers have adopted the soundproof room as a standard configuration, such as the soundproof room of the MXM series high-speed press of YAMADA DOBBY of Japan.
This integration is also reflected in the control system, which makes the high-speed press present certain characteristics of metal cutting machine tools. For example, the handwheel is used to precisely adjust the height of the mold, the windows-based visual operating system is used for the input and storage of stamping parameters, the online monitoring system (such as the BRANKAMP system) is used to monitor the operating parameters of the stamping line in real time, and the Internet technology is used for online fault monitoring And disposal etc.
⑼ Application of servo drive technology.
The application of servo drives in stamping equipment can achieve high process flexibility while simplifying the transmission system. The high-speed precision press reflects a high degree of “rigidity”. With the development of servo technology and the improvement of users’ stamping process, it will realize the “combination of rigidity and flexibility”, that is, the application of servo drive technology to the field of high-speed precision presses. For example, the Fit-3 type high-speed servo press developed by Japan’s YAMADA DOBBY company is driven by a servo motor without clutch and brake.