Technical analysis of high-speed precision press
High-speed precision presses have experienced more than one hundred years of development, and have experienced the development stage from bottom transmission to upper transmission, from precision to ultra-precision, and the automation level of the whole machine is continuously improved. New technologies are constantly emerging and developing, and now only some representative technologies are analyzed.
⑴ Swiss BRUDERER technology.
Figure 2 shows the BSTA press transmission system of Swiss BRUDERER, which is essentially a lever mechanism, and the slider displacement curve is similar to a crank slider mechanism. The advantage of this mechanism is that the hinge points on both sides only bear 20% of the punching load, which provides conditions for the dynamic adjustment of the bottom dead center accuracy.
⑵ MINSTER of the United States, SCHULER of Germany and BALCONI of Italy technology.
These three companies all use the traditional crank-slider mechanism as the working mechanism (Figure 3). The common feature is that the crankshaft support and connecting rod parts are all sliding bearings. The biggest feature of the sliding bearing is that it can achieve no contact under a certain oil pressure, relying on the rigidity of the oil film to transmit the pressing force, with minimal or no wear, and the reliability and precision of the machine are high.
Figure 2 BSTA press from BRUDERER, Switzerland
Figure 3 Crank slider transmission mechanism
⑶ American OAK technology.
The American OAK transmission system is shown in Figure 4, which uses a sine mechanism as the working mechanism. The transmission part can realize the compression of the transmission gap through the pretension of the needle roller. American OAK products are widely used in high-speed stamping of air-conditioning fins.
Figure 4 U.S. OAK press adopts sinusoidal mechanism
⑷ Japanese AIDA technology.
AIDA’s high-speed precision presses are mainly HMX series, which have undergone a series of technical adjustments. The main technologies used are:
1) Guiding part. Adopting pure rolling flat guide rail, through the rack drive in the middle, the flat guide rail can only roll but not slip; the four-circle guide post is hydrostatically guided, and the damping hole is set in the guide sleeve. When the bearing capacity increases, the local oil pressure increases , To realize the counterbalance with the guiding load; the four-circle guide column compound guide structure is to compound the rolling guide and the sliding guide, in which the rolling part ensures high guiding accuracy, and the sliding part ensures high guiding rigidity; four-round guide The column is guided by a hexagonal prism, and the guiding part is in line contact, and the guiding rigidity is obviously improved.
2) The crankshaft transmission part. It adopts a high-rigidity three-point support structure, and some models have a rolling + sliding composite structure at two external points. The brake and clutch separation structure are generally used and are arranged on both sides of the crankshaft.
3) Connecting rod and mold adjustment part. The connecting rod part has an integrated ball head type and a pin shaft type. For four-corner and eight-sided guide rails, the mold adjustment part is usually installed in the slider body, and the external air source is used as the working power; for the ball head structure, the mold adjustment structure is set on the upper beam; the six-circle guide column guide structure, the mold adjustment Some are generally directly designed in the upper beam (many domestic use); some models use worm gear and other transmission parts installed in the slider body, and the motor and other driving parts are installed in the column and other parts.
In addition to the double-point HMX series, AIDA later developed a single-row four-point MSP structure. Two sets of flywheel-clutch/brake systems are used to drive a four-point structure synchronously at both ends of the crankshaft. The crankshaft and supporting parts are supported by sliding bearings, and each connecting rod part adopts a complex threaded locking and overload protection separation structure.
⑸ Japanese YAMADA DOBBY technology.
YAMADA DOBBY not only uses the crank slider mechanism as the working mechanism, but also uses two forms of multi-link mechanism (Figure 5, the maximum nominal force of the NXT type is 2000kN).
⑹ Japanese KYORI technology.
Figure 5 YAMADA DOBBY models: NXT and MXM
Japanese KYORI high-speed precision presses are divided into crankshaft type and multi-link type. Multi-link type high-speed precision presses have a high domestic market share due to their simple structure (not adjustable stroke), moderate price, and high precision. Compared with YAMADA DOBBY’s multi-link model, the dwell time near the bottom dead center is slightly shorter, so higher working speed can be achieved. Its latest FENIX model has a further 20% increase in speed. The multi-link drive technology of Japan’s KYORI has been adopted and upgraded by many domestic companies due to its simple structure.
⑺ Bottom dead center stabilization technology.
The bottom dead center accuracy is an important accuracy index of high-speed precision presses, which directly affects the accuracy of stamping products, and is also a key index that affects the technical level of high-speed precision presses. There is no uniform standard in the world. The precision and ultra-precision bottom dead center precision standards and test methods are given in the new precision of closed high-speed precision presses (GB/T 29548-2013) in my country. In addition to BRUDERER’s mechanical compensation for the bottom dead center, the measures taken abroad to improve the bottom dead center accuracy mainly include:
1) Preheat. Preheat the press before starting work, and make sure that the temperature rise during the working process of the press does not exceed the preheating temperature. The preheating temperature and time are related to the working speed of the high-speed press.
2) Set up an oil cooler. During the working process of the press, the cooling oil flows through the inside of the machine to suppress the temperature rise.
3) Heat first and then keep warm. The heater and the oil pump are automatically switched on and timed several hours before starting to work, and the internal temperature of the press is gradually increased. After the press works, the temperature rise does not exceed the set value and remains constant through the lubricant cooling device. Currently, many companies adopt this method.
4) In addition, the NEW-BEAT series of high-speed presses (toggle link transmission mechanism) manufactured by KYORI, Japan, adopt a method of heating the rod system in a certain order. First, the connecting rod and the connecting rod are heated to expand, and the bottom dead center position rises slightly, and then the upper and lower toggle levers and the guide rod are heated to expand, and the bottom dead center position drops, so that the bottom dead center position remains unchanged.