Development status and Prospect of the hottest mic

2022-07-27
  • Detail

The development status and Prospect of micro injection molding machine with the progress of science and technology, the products continue to develop in the direction of miniaturization, thus producing the micro electro mechanical system technology required by the industry in the new century. In 2002, the world created an output value of 45billion US dollars in this field. Its main products play an important role in optoelectronic communication, image transmission, biochemical medicine, information storage, precision machinery and other application fields. In order to produce micro components with practical value, many emerging manufacturing technologies have emerged, including lithography, electroforming and demoulding (Liga), UV etching (UV), electrical discharge machining (EDM), micro injection molding, precision grinding and precision cutting. Among them, micro injection molding technology has become one of the research hotspots of manufacturing technology in the world because it is easy to achieve low-cost mass production of precision micro structure parts

the micro injection molding technology, in which the quality of finished products is calculated in milligrams and the geometric dimension of finished products is measured in microns, began in the late 1980s. It is a new advanced manufacturing technology. Compared with the traditional and conventional injection molding technology, it puts forward different requirements for molding materials, molding process and molding equipment. Many existing and mature injection molding technologies and theories are not applicable to micro injection molding technology. The technical characteristics of micro injection molding process must be systematically and thoroughly studied and discussed in theory and practice

1 special requirements for micro injection molding machine

at the beginning of the development of micro injection molding technology, there was no special injection molding machine for micro parts manufacturing. In production practice, the traditional medium and large-scale injection molding machines are usually used to cooperate with the multi-mode cavity mold design to realize the part preparation, which not only has high requirements for the mold runner balance design, but also is difficult to control the molding quality of the parts. Therefore, a special injection molding machine is required to meet the requirements of miniaturization and high precision of parts. Compared with the traditional injection molding technology, micro injection molding technology has many special requirements for production equipment, mainly in the following aspects:

(1) high injection rate: micro injection molding parts have small quality and volume, and the injection process is required to be completed in a short time, so as to prevent the parts from being under injected due to solidification of molten materials, Therefore, high injection speed is required during molding. The injection speed of the traditional hydraulic driven injection molding machine is 200mm/s, and the injection speed of the electric servo motor driven injection molding machine is 600mm/s. However, the micro injection molding process usually requires the injection speed of the polymer melt to be more than 800mm/s. Using the shear thinning principle of the polymer melt, the viscosity of the melt is reduced at a high injection speed to make it fill the micro cavity smoothly

(2) precision injection volume measurement: the quality of micro injection molding parts is measured in milligrams only, so the micro injection molding machine needs to have a control unit for precision measurement of one injection during the injection process, and its quality control accuracy should reach the milligram level, and the screw stroke accuracy should reach the micrometre level. The traditional injection molding machine usually adopts the linear reciprocating screw injection structure, and the injection control error is relatively large, which can not meet the micro control requirements of micro injection molding, and has a great impact on the molding quality of parts

(3) rapid response capability: the injection volume is very small during the micro injection molding process, and the moving stroke of the screw/plunger of the corresponding injection equipment is also very small. Therefore, the driving unit of the micro injection molding machine must have a very fast reaction speed, so as to ensure that the equipment can reach the required injection pressure in an instant

2 classification of micro injection molding machines Some Japanese and American companies have cooperated with scientific research institutions to develop various types of special micro injection molding machines (generally, the clamping force is less than 15t =. At present, the main foreign equipment suppliers include Nissei, y, Battenfeld, MCP, Babyplast, Takahashi, etc. the main functions of the micro injection molding machine usually include plasticizing, metering and injection, which can be classified by the driving mode of each part or by the mechanism design of each part.

according to the driving mode, it can be divided into hydraulic/pneumatic drive, all electric drive and electro-hydraulic composite drive Drive. The hydraulic/pneumatic drive, i.e. the rotary/reciprocating motion of the plasticizing unit and the injection unit are driven by the hydraulic/pneumatic system, which has the advantage of high injection pressure and injection speed, and can meet the requirements of micro injection molding process; The disadvantage is that the control accuracy is poor. All electric drive means that all units of the equipment are driven by servo motor, which has the advantages of high control precision, fast response speed and little environmental pollution; The disadvantage is that the thrust output of the servo motor is limited, and the injection pressure and speed that can be achieved are not high. The electro-hydraulic composite drive combines the high injection pressure and injection speed of the hydraulic drive with the precise control and rapid response of the full electrical drive as the drive source of the system

according to the mechanism design classification of plasticizing and injection unit, it can be divided into screw type, plunger type, screw plunger mixed type and other special forms

2.1 the plasticization, metering and injection of the screw type

micro injection molding machine are completed by a group of screws. The rotation and reciprocating motion of each unit are on the same axis, which is simple in structure and easy to control. However, due to the non-return ring structure at the front end of the screw, the control accuracy of the equipment for the primary injection volume is poor. The representative models of this kind of micro injection molding machine include boy12a of German Y company, hm7-denkey of rijing Resin Industry Co., Ltd., jmw-015s-5t of Shuyan industry and EC5 of Toshiba

2.2 plunger type

micro injection molding machine includes two types: single plunger type and plunger plunger type. The single plunger type pushes granular or powdery plastic forward, flashes Amway material everywhere around a fish, and injects it into the mold cavity through the nozzle. The function of the diversion shuttle is to disperse the plastic on the inner surface of the tube, making the plastic easier to plasticize; The content is characterized by the inclusion of graphene and two-dimensional materials. The plunger plunger type consists of two groups of plungers to complete the plasticization and metered injection functions respectively. This type of micro injection molding machine usually has small plasticizing amount, low plasticizing quality and poor mixing performance. Its representative models include babyplast6/10 of Spanish cronoplast company, rabbit2/3 of British MCP company and sesame of American Medical Murray company

2.3 screw plunger hybrid

micro injection molding machine takes the screw as the plasticizing unit to complete mixing and plasticizing, and takes the small-diameter plunger with servo motor and controller as the micro injection unit to complete precision metering and injection. The micro injection molding machine can be divided into two-stage metering and three-stage metering according to the design of plasticizing metering mechanism

(1) two stage metering type: the plasticizing screw first plasticizes the plastic and carries out rough metering, then sends it to the injection chamber, and then the small-diameter plunger carries out precise metering and injection. The representative models of such micro injection molding machines include 12/90hsp of MCP company in the UK, tr18s3a of Sodick company in Japan, au3e of rijing resin Co., Ltd. and epoch shot7 of Tianrui company

servo control drive

three-stage metering type: the plasticizing screw plasticizes the plastic and carries out rough metering, and then sends it to the first metering chamber. After metering by the first metering plunger, the injection is sent to the second metering chamber, and then the injection is carried out after precise metering by the second metering plunger. The representative models of this micro injection molding machine include microsystem50 of Battenfeld company and fx25 improved by German ferromatik Milacron company in cooperation with IKv Research Institute of Aachen University

4 other special forms

the injection machine of German Ettlinger company has a coaxial screw/plunger composite injection unit, which can produce 0 0g plastic parts. The outstanding feature of this type of mechanism is that it adopts direct injection molding. The hot runner system is integrated into the injection machine through the needle nozzle with special structure design, so that the micro injection molding process can adopt the runner less mold, which saves materials and shortens the molding cycle

3 development trend of micro injection molding machine

micro injection molding machine is a new direction of the development of injection molding equipment, which creates a new way for the research of micro structure parts and system manufacturing. Its outstanding advantage is that it can realize the mass and low-cost production of high-precision and high-precision parts. For the screw micro injection molding machine, the plasticization, metering and injection are all completed by a group of screws, so the structure is simple and easy to control. The disadvantage is that due to the non-return ring structure at the front end of the screw, the control accuracy of the equipment on the one-time injection volume is poor, and the probability of material degradation in the injection barrel is increased, which affects the stability of part molding quality. For the plunger micro injection molding machine, although its control accuracy of injection volume is higher than that of the screw type, its plasticizing volume is small, the mixing performance is poor, and the plasticizing quality of the material is worse than that of the screw type, which is not conducive to forming parts with high surface quality and optical characteristics. The screw plunger hybrid micro injection molding machine integrates the advantages of the plunger type and the screw type. With the screw as the plasticizing unit and the plunger as the metering and injection unit, the control accuracy of micro injection molding and the molding quality of parts are significantly improved. However, its structure is usually more complex and the control and maintenance are more complicated than the plunger type and the screw type

the above micro injection molding machines with different principles have different performance indicators, which are suitable for the needs of different micro structure parts. Therefore, the appropriate micro injection molding machine should be selected and configured according to the cost, size and quality of specific micro structure parts. However, as micro injection molding technology is a new technology field, many basic theories are not perfect, and the micro injection molding process is not mature enough, which needs further exploration and research. At the same time, with the continuous development of electromechanical integration technology, computer network technology and other related technologies, it provides many new ideas and new directions for the development of micro injection molding machine. Therefore, the further development of micro injection molding machines still faces many challenges, which are mainly reflected in the following aspects:

(1) driving mode: at present, most micro injection molding machines use high-frequency and high torque servo motors with high-precision mechanical transmission devices to achieve the precision measurement and high-speed and high-pressure injection required by micro injection molding technology, but this mode uses mechanical transmission devices, There are transmission clearance errors and accumulated mechanical deformation errors, which affect the precision control and rapid response of the equipment. However, linear motor drive has the problems of low thrust and high cost. At present, only medical Murray company in the United States and Fanuc company in Japan have adopted this drive mode

(2) plasticizing method: the plasticizing unit of micro injection molding machine adopts screw type or plunger type. Due to the poor plasticizing effect of plunger type, it has not become the mainstream of current development. Although the plasticizing effect of screw type is good, there are still problems such as difficult processing of small-size screws, limited service life and long plasticizing time. Therefore, new environment-friendly and efficient plasticizing methods need to be further explored, such as ultrasonic plasticizing, microwave plasticizing and laser plasticizing. At present, the German IKv Research Center has studied the ultrasonic plasticizing method of injection molding machine and made gratifying progress

(3) injection materials: most micro injection molding machines take polymer as the injection object, and the molding scope covered by micro injection molding technology includes not only polymer but also powder feed. Due to powder feeding

Copyright © 2011 JIN SHI