The new precision vertical injection molding machine clamping mechanism

Date：2014/10/31 16:53:39

Precision vertical injection molding machine is set in modern electronic, mechanical, polymer materials and the computer, network and IT in one of the highly mechatronic products. With the continuous development of information, automotive, construction, medical, electrical and other industries, and growth of precision plastic products people have become increasingly demanding, conventional injection technology has been difficult to meet high standards. This gives the development of precision vertical injection molding machine provides a broad space, and the development of machinery and electronics industry and improve precision servo control technology R & D vertical injection molding machine provides a powerful support for. At this stage, the country has made certain achievements in the development of precision vertical injection molding machine side, many manufacturers have developed a number of sophisticated hydraulic or electric vertical injection molding machine. Abroad, Netstal company developed a series of all-electric ELION precision vertical injection molding machine. Toshiba has introduced the EC Series Electric precision injection molding machines with clamping device using 5-point double-stranded lever device. BATTENFELD HM series produced by vertical injection molding machine using UnilogB6 control system can be run in windowsxp platform, through which to connect peripherals and communication interfaces, which enables remote maintenance and data transfer. The key is to ensure precision injection molding dimensional accuracy and stability of the product, which is vertical injection molding machine clamping mechanism put forward high requirements. For this purpose, can be advanced servo control systems and precision-balanced mechanical structure designed to ensure the accuracy and stability.
A new fully hydraulic clamping mechanism
         Precision Hydraulic vertical injection molding machine has many unique advantages in molding precision, shape aspects of complex products. It is from the traditional single-cylinder liquid-filled, multi-cylinder liquid-filled to the later development of two direct compression plate, more categories, also a great difference. As a traditional single-cylinder liquid-filled fully hydraulic representatives, many manufacturers have production, such as Japan's Toshiba, Nissei, Mitsubishi and other companies, but the huge volume of this structure, easily within the vent leak, boost slow, energy and more. The early 1990s, in Europe, led by Germany launched a number of new fully hydraulic vertical injection molding machine. Among them, two direct compression plate the most representative, it addresses the shortcomings of single-cylinder liquid-filled vertical injection molding machine, but its control is difficult, high-precision machining, hydraulic technology is also difficult to master. In the form of fully hydraulic clamping mechanism are more precise comparison of the new clamping mechanism are the following:
         1) 4-cylinder straight locks fully hydraulic clamping mechanism. 4 the use of four clamping cylinder as the piston rod, the piston rod is designed with a one. Clamping action moving template shift mode is implemented by two cylinders. Unique hydraulic system enables clamping mechanism of hydraulic oil pressure and injection pressure change synchronization. 4 clamping cylinder mounted on the moving platen, in the opening and closing movement, the guide is good, even by force. However, this structure does not apply to large vertical injection molding machine.
         2) high-speed high-precision hydraulic clamping devices. After the template is equipped with high-pressure clamping cylinder center hole left cover, high-pressure clamping rod, right after the high-pressure clamping cylinder head, a high-pressure clamping cylinder; 2 side hole after the template is equipped with high-speed clamping cylinder boring cover, high-speed clamping cylinder piston rod, after the high-speed clamping cylinder through cover to form the high-speed clamping cylinder; high-speed shift mode, high-speed clamping cylinder end cap by pushing together, along with the high-pressure clamping piston rod moves along the moving plate mold. After clamping, high voltage from the high voltage clamping clamping cylinder moment; when changing the mold thickness adjustment mode can be used to adjust the capacity of the mold clamping cylinder device location.
         3) direct pressure vertical injection molding machine clamping device. The device mainly through a certain length at one end of the threaded rod, and installed in the board locknut match, then the head plate below the two side cylinders quick shift mode for fast moving mold, mold opening and closing action to achieve; the other set in the head by a board of four pairs of high-pressure clamping cylinder corners to achieve clamping. The specific process is that when the locking nut rotation angle, the release lever is moved quickly shift mode cylinder movable platen advances to a preset position, rotation angle lock nut to lock the rod, and then by the high-pressure clamping cylinder clamping . The structure is simple and does not require secondary transfer mode, but it is the use of the rod has a threaded to achieve transfer mode, that is, different mold thickness, in a different position locking screw. In order to accurately transfer mode over a wide range, it requires a longer lever on the thread length and thread pitch should not be too large, so that in the course of the thread easily damaged, so that the rod shorter lifespans.
2 electric clamping mechanism and structural analysis
         Using electric clamping mechanism of vertical injection molding machine manufacturer mainly in Japan, including Sumitomo SES series, Toshiba EC series, the Japanese steel JELII series, Nissei ELJECT series, Japan SI series. Primarily through the electric mold clamping hydraulic system to the servo system to achieve the clamping function, the drive member by a ball screw, servo motor, transmission gears, etc., the rotational movement of ball screw servo motor into linear motion to achieve the mold clamping movement. Thus, the main structure with traditional toggle vertical injection molding machine similar. According to achieve in the form of mold, the electric vertical injection molding machine can be divided into electric and electric toggle direct pressure.
         Works electric toggle clamping mechanism: when the motor forward rotation, shift mode toggle mechanism driven screw push forward movement moving platen. When the mold parting surface contact line toggle mechanism has not been arranged by the deformation resistance of the movable platen role in the formation. At this time the motor speed is reduced, the torque increases, the screw acting on the shift mode of the force is increased until sufficient to overcome the resistance to deformation, so that the toggle lever arrangement has become the first-line. Clamping mechanism of elastic deformation occurring mold to achieve a preload, the preload is the clamping force. When mold, motor reversal, in shift mode screw force, toggle the line arrangement is destroyed, move the template forced separation and set the template and return the original position before clamping, enabling open mode.
         The key components of electric toggle clamping mechanism is the drive screw nut form, its structure there are two kinds: one is the ball screw and ball nut mounted on the central position of the clamping mechanism for the ball screw driven the way.
         Nut ball screw driven by the movement, namely screw rotates, the ball nut only for linear motion. Ball screw through the bearing and bearing assembly in the center of the transom, the ball nut directly fixed to the center through the crosshead screws. Servo motor drive ball screw nut is rotated back and forth pushing the ball movement, so bring the whole body movement. This structure using common nut screw arrangement of simple structure, but the interference problems with the crankshaft screw Clamping swing without rollback occurs, the use of double ball screw structure distributed on both sides of the cross, then solve the interference problem, but the structure is more complex.
         Another is a ball nut and ball screw installed in the middle position of the clamping mechanism, as a way to drive the ball nut.
         Driven by ball screw nut movement, that ball nut is rotated, the screw only for linear motion. Pearl nut bearing and housing assembly in the center of the transom, fixed directly to the crosshead screw center and the screw is rotated by a flat key prevented. Servo motor drives the ball nut is rotated to drive the screw back and forth movement, so bring the whole body movement [11]. This structure is designed on the domestic application of the broader changes in the hydraulic toggle clamping mechanism is small, easy to process, but the trip back and forth movement of a large screw, you need to reserve space.
Design of electro-hydraulic hybrid clamping mechanism
         Electric hydraulic hybrid mold machine combines the advantages of electric and hydraulic mechanism, is an important direction of development of the clamping mechanism. For this reason, on the basis of our previous work, around precision injection molding process analysis, carried out small and medium sized vertical injection molding machine hybrid electro-hydraulic clamping mechanism Design.
3.1 Mechanism Design
         The design of the electro-hydraulic hybrid clamping mechanism, combines the advantages of all-electric and four-cylinder direct-locking clamping mechanism, the clamping action realized by four cylinders, the cylinder is fixed on the template in action, the cylinder piston rod connected with together as one, in the right side of the piston through the high-pressure oil to achieve clamping. Using the clamping cylinder piston oil path on both sides of the spool to achieve together on and off the spool in a small hole at the right side of the end cap abutting the hydraulic effect, disconnect the oil can achieve stable clamping, removed oil after the pressure in the spring return force, the spool back and realize communication oil passage. Shift mode transmission in the form of screw nut through the structure to achieve, servo motor drives the belt wheel rotation, then drive through the hollow shaft flat key rotation, rotation of the hollow shaft and connected together by a ball screw nut, thereby driving the screw linear movement, led moving templates mold clamping action.
3.2 Structure Features
         1) 4-cylinder direct clamping part is locked in the mold opening and closing movement, the guide is good; can be balanced in the high-pressure clamping force when the high-mold positioning accuracy, high repeatability of clamping force, no transfer mode, and lock the injection pressure clamping force feedback control, wide application, easy to solve the traditional hydraulic characteristics of slow leakage. Cylinder internal structure is relatively simple and compact structure.
         2) the use of servo motors and nut screw structure, to achieve rapid opening and closing of the mold, and to ensure the control precision, can protect expensive mold, also can save energy, resolve conflicts force and speed.
         3) no machine hinge wear, simple structure, the overall clamping mechanism wear small.
         4) The use of the second plate, after a template by a small force, the overall amount of deformation of small institutions, high mechanical precision.
         5) combines the advantages of fully hydraulic and all-electric vertical injection molding machine, both with full electric precise positioning of the advantages of hydraulic structures have high thrust adaptive characteristics, and manufacturing costs are lower than with the specifications of the all-electric type vertical injection molding machine.
         6) The top of the double cylinder, on separate sides of the movable platen bracket so that the top of the smooth operation, the top of the bracket even by force. Nut screw structural arrangement in the middle of moving the template bracket with the top of the cylinder position to avoid interfere.
3.3 Comparison with other clamping structural advantages
3.3.1 Comparison with the electro-mechanical clamping mechanism
         Electro-mechanical clamping mechanism using closed-loop servo system, although easy to operate, high precision control, energy conservation, but the toggle structure used has inherent limitations, especially Linkage precision machining, assembly accuracy is difficult to achieve precision high cost, and mechanical wear will cause toggle clamping accuracy declining. Therefore, the accuracy of electro-mechanical clamping mechanism is not as electro-hydraulic hybrid, but not easily transfer mode such as electro-hydraulic hybrid.
3.3.2 Comparison with full-hydraulic clamping mechanism
         Japan with Sumitomo, crew-based vertical injection molding machine for machining precision products still use more traditional liquid-filled. Liquid-filled template force is relatively good accuracy in favor of the stability of the molded article. But its system stiffness poor clamping cylinder easily within the vent leak, bulky, slow boost, energy and more. Electro-hydraulic hybrid clamping mechanism adopts the advantages servo motor and lead screw nut structure, realize rapid opening and closing the mold and energy efficiency, while clamping portion hydraulic structure precisely balanced to ensure the precision requirements.
4 Conclusion and Outlook
         Clamping device as a vertical injection molding machine's main components, has been the various vertical injection molding machine manufacturers, the company's technology focus of competition. Toggle clamping mechanism, the traditional template rod hydraulic three vertical injection molding machine in terms of clamping speed, precision mold clamping force, etc., have been gradually not meet modern production high precision and high efficiency requirements. So, in the original clamping mechanism on the basis of the development of all-electric, electro-hydraulic hybrid, non-rod type vertical injection molding machines and other new clamping mechanism is an important development direction of the current precision injection mold clamping mechanism, especially electro-hydraulic hybrid combination collection of all-electric mode institutions and full fluid-advantage, with great value and broad development prospects.

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