一、Die history and die trend1、Die position in industrial productionWith mold components, with high efficiency, good quality, low cost, saving energy and raw materials and a series of advantages, with the mold workpieces possess high accuracy, high complexity, high consistency, high productivity and low consumption , other manufacturing methods can not match. Have already become an important means of industrial production and technological development. The basis of the modern industrial economy.Mold is a high-volume products with the shape tool, is the main process of industrial production equipment.The development of modern industrial and technological level depends largely on the level of industrial development die, so die industry to national economic and social development will play an increasing role. March 1989 the State Council promulgated "on the current industrial policy decision points" in the mold as the machinery industry transformation sequence of the first, production and capital construction of the second sequence (after the large-scale power generation equipment and the corresponding power transmission equipment), establish tooling industry in an important position in the national economy. Since 1997, they have to mold and its processing technology and equipment included in the "current national focus on encouraging the development of industries, products and technologies catalog" and "to encourage foreign investment industry directory." Approved by the State Council, from 1997 to 2000, more than 80 professional mold factory owned 70% VAT refund of preferential policies to support mold industry. All these have fully demonstrated the development of the State Council and state departments tooling industry attention and support. Mold around the world about the current annual output of 60 billion U.S. dollars, Japan, the United States and other industrialized countries die of industrial output value of more than machine tool industry, beginning in 1997, China's industrial output value has exceeded the mold machine tool industry output.According to statistics, home appliances, toys and other light industries, nearly 90% of the parts are integrated with production of chopsticks; in aircraft, automobiles, agricultural machinery and radio industries, the proportion exceeded 60%. Such as aircraft manufacturing, the use of a certain type of fighter dies more than 30,000 units, of which the host 8000 sets, 2000 sets of engines, auxiliary 20 000 sets. From the output of view, since the 80's, the United States, Japan and other industrialized countries die industry output value has exceeded the machine tool industry, and there are still rising. Production technology, according to the International Association predicts that in 2000, the product best pieces of rough 75%, 50% will be finished mold completed; metals, plastics, ceramics, rubber, building materials and other industrial products, most of the mold will be completed in more than 50% metal plates, more than 80% of all plastic products, especially through the mold into.2、The historical development of moldThe emergence of mold can be traced back thousands of years ago, pottery and bronze foundry, but the large-scale use is with the rise of modern industry and developed.The 19th century, with the arms industry (gun's shell), watch industry, radio industry, dies are widely used. After World War II, with the rapid development of world economy, it became a mass production of household appliances, automobiles, electronic equipment, cameras, watches and other parts the best way. From a global perspective, when the United States in the forefront of stamping technology - many die of advanced technologies, such as simple mold, high efficiency, mold, die and stamping the high life automation, mostly originated in the United States; and Switzerland, fine blanking, cold in Germany extrusion technology, plastic processing of the Soviet Union are at the world advanced. 50's, mold industry focus is based on subscriber demand, production can meet the product requirements of the mold. Multi-die design rule of thumb, reference has been drawing and perceptual knowledge, on the design of mold parts of a lack of real understanding of function. From 1955 to 1965, is the pressure processing of exploration and development of the times - the main components of the mold and the stress state of the function of a mathematicalsub-bridge, and to continue to apply to on-site practical knowledge to make stamping technology in all aspects of a leap in development. The result is summarized mold design principles, and makes the pressure machine, stamping materials, processing methods, plum with a structure, mold materials, mold manufacturing method, the field of automation devices, a new look to the practical direction of advance, so that pressing processing apparatus capable of producing quality products from the first stage.Into the 70's to high speed, launch technology, precision, security, development of the second stage. Continue to emerge in this process a variety of high efficiency, business life, high-precision multi-functional automatic school to help with. Represented by the number of working places as much as other progressive die and dozens of multi-station transfer station module. On this basis, has developed both a continuous pressing station there are more slide forming station of the press - bending machine. In the meantime, the Japanese stand to the world's largest - the mold into the micron-level precision, die life, alloy tool steel mold has reached tens of millions of times, carbide steel mold to each of hundreds of millions of times p minutes for stamping the number of small presses usually 200 to 300, up to 1200 times to 1500 times. In the meantime, in order to meet product updates quickly, with the short duration (such as cars modified, refurbished toys, etc.) need a variety of economic-type mold, such as zinc alloy die down, polyurethane rubber mold, die steel skin, also has been very great development.From the mid-70s so far can be said that computer-aided design, supporting the continuous development of manufacturing technology of the times. With the precision and complexity of mold rising, accelerating the production cycle, the mold industry, the quality of equipment and personnel are required to improve. Rely on common processing equipment, their experience and skills can not meet the needs of mold. Since the 90's, mechanical and electronic technologies in close connection with the development of NC machine tools, such as CNC wire cutting machine, CNC EDM, CNC milling, CNC coordinate grinding machine and so on. The use of computer automatic programming, control CNC machine tools to improve theefficiency in the use and scope. In recent years, has developed a computer to time-sharing by the way a group of direct management and control of CNC machine tools NNC system.With the development of computer technology, computers have gradually into the mold in all areas, including design, manufacturing and management. International Association for the Study of production forecasts to 2000, as a means of links between design and manufacturing drawings will lose its primary role. Automatic Design of die most fundamental point is to establish the mold standard and design standards. To get rid of the people of the past, and practical experience to judge the composition of the design center, we must take past experiences and ways of thinking, for series, numerical value, the number of type-based, as the design criteria to the computer store. Components are dry because of mold constitutes a million other differences, to come up with a can adapt to various parts of the design software almost impossible. But some products do not change the shape of parts, mold structure has certain rules, can be summed up for the automatic design of software. If a Japanese company's CDM system for progressive die design and manufacturing, including the importation of parts of the figure, rough start, strip layout, determine the size and standard templates, assembly drawing and parts, the output NC program (for CNC machining Center and line cutting program), etc., used in 20% of the time by hand, reduce their working hours to 35 hours; from Japan in the early 80s will be three-dimensional cad / cam system for automotive panel die. Currently, the physical parts scanning input, map lines and data input, geometric form, display, graphics, annotations and the data is automatically programmed, resulting in effective control machine tool control system of post-processing documents have reached a high level; computer Simulation (CAE) technology has made some achievements. At high levels, CAD / CAM / CAE integration, that data is integrated, can transmit information directly with each other. Achieve network. Present. Only a few foreign manufacturers can do it.3、The trend of the die(1) mold software features integratedDie software features of integrated software modules required relatively complete, while the function module using the same data model, in order to achieve Syndicated news management and sharing of information to support the mold design, manufacture, assembly, inspection, testing and production management of the entire process to achieve optimal benefits. Series such as the UK Delcam's software will include a surface / solid geometric modeling, engineering drawing complex geometry, advanced rendering industrial design, plastic mold design expert system, complex physical CAM, artistic design and sculpture automatic programming system, reverse engineering and complex systems physical line measurement systems. A higher degree of integration of the software includes: Pro / ENGINEER, UG and CATIA, etc.. Shanghai Jiaotong University, China with finite element analysis of metal plastic forming systems and Die CAD / CAM systems; Beijing Beihang Haier Software Ltd. CAXA Series software; Jilin Gold Grid Engineering Research Center of the stamping die mold CAD / CAE / CAM systems .(2) mold design, analysis and manufacture of three-dimensionalTwo-dimensional mold of traditional structural design can no longer meet modern technical requirements of production and integration. Mold design, analysis, manufacturing three-dimensional technology, paperless software required to mold a new generation of three-dimensional, intuitive sense to design the mold, using three-dimensional digital model can be easily used in the product structure of CAE analysis, tooling manufacturability evaluation and CNC machining, forming process simulation and information management and sharing. Such as Pro / ENGINEER, UG and CATIA software such as with parametric, feature-based, all relevant characteristics, so that mold concurrent engineering possible. In addition, Cimatran company Moldexpert, Delcam's Ps-mold and Hitachi Shipbuilding of Space-E/mold are professional injection mold 3D design software, interactive 3D cavity, core design, mold base design configuration and typical structure . Australian company Moldflow realistic three-dimensional flow simulation software MoldflowAdvisers been widely praised by users and applications. China Huazhong University of Science have developed similar software HSC3D4.5F and Zhengzhou University,Z-mold software. For manufacturing, knowledge-based intelligent software function is a measure of die important sign of advanced and practical one. Such as injection molding experts Cimatron's software can automatically generate parting direction based parting line and parting surface, generate products corresponding to the core and cavity, implementation of all relevant parts mold, and for automatically generated BOM Form NC drilling process, and can intelligently process parameter setting, calibration and other processing results.(3) mold software applications, networking trendWith the mold in the enterprise competition, cooperation, production and management, globalization, internationalization, and the rapid development of computer hardware and software technology, the Internet has made in the mold industry, virtual design, agile manufacturing technology both necessary and possible. The United States in its "21st Century Manufacturing Enterprise Strategy" that the auto industry by 2006 to achieve agile manufacturing / virtual engineering solutions to automotive development cycle shortened from 40 months to 4 months.二、The injection and Compression MoldingInjection molding si principally used for the production of the thermoplastic parts, although some progress has been made in developing a method for injection molding some thermosetting materials. The problem of injecting a melted plastic into a mold cavity form a reservoir of melted material has been extremely difficult to solve for thermosetting plastics which cure and harden under such conditions within a few minutes. The principle of injection molding is quite similar to that of die-casting. The process consists of feeding a plastic compound in powdered or granular form from a hopper through metering and melting stages and then injecting it into a mold. After a brief coolling period, the mold is opened and the solidified part ejected. Injection-molding machines can be arranged for manual operation, automatic single-cucle operation, and full automatic operation. The advantage of injection molding are:(i) a high molding speed adapted for mass production is possible;(ii)there is a wide choice of thermoplastic materials providing a variety of usefull properties;(iii)it is possible to mold threads, undercuts, side holes, and large thin sections.Several methods are used to force or inject the melted plastic into the mold. The most commonly used system in the larger machines is the in-line reciprocating screw.The screw acts as a combination and plasticizing unit.As the plastic is fed to the rotating screw,it passes through three zones as shown: feed,compression, and metering. After the feed zone, the screw-flight depth is gradually reduced,forcing the plastic to compress. The work is converted to heat by shearing the plastic, making it a semifluid mass. In the metering zone, additional heat is applied by conduction from the barrel surface. As the chamber in front of the screw becomes filled, it forces thescrew back, tripping a limit switch that activates a hydraulic cylinder that forces the screw forward and injects the fluid plastic into the closed mold.An antiflowback valve prevents plastic under pressure from escaping back into the screw flights.The clamping force that a machine is capable of exerting is part of the size designation and is measured in tons. A rule-of-thumb can be used to determine the tonnage required for a particular job. It is based on two tons of clamp force per square inch of projected area. If the flow pattern is difficult and the parts are thin,this may have to go to three or four tons.Many reciprocating - screw machines are capable of handing thermosetting plastic materials.Previously these materials were handled by compression or transfer molding.Thermosetting materials cure or polymerize in the mold and are ejected hot in the range of 375℃～410℃.Thermoplastic parts must be allowed to cool in the mold in order to remove them without distortion.Thus thermosetting cycles can be faster.Of course the mold must be heated rather than chilled,as with thermoplastics.The importance of Injecting the mold are :⑴、Plastics have the density small, the quality light, the specific tenacity big, theinsulating property good, the dielectric loss low, the chemical stability strong, the formation productivity high and the price inexpensive and so on the merits,obtained day by day the widespread application in the national economy andpeople's daily life each domain, as early as in the beginning of 1990s, the plastic annual output already surpassed the steel and iron and the non-ferrous metalannual output sum total according to the volume computation.In mechanical and electrical (for example so-called black electrical appliances), domains and so on measuring appliance, chemical, the automobile and astronautics aviation, theplastic has become the metal the good substitution material, had the metalmaterial plastic tendency.⑵、Take the automobile industry as the example , as a result of the automobilelightweight, the low energy consumption development request, the automobile spare part material constitution occurred obviously has modelled the band steelthe change, at present our country automobile plastic accounts for 5% which the automobile was self-possessed to 6%, but overseas has reached 13%, forecast according to the expert, the automobile plastic bicycle amount used will also be able further to increase.On modern vehicles, regardless of is outside installs the assorted items, the internal installation assorted items, the function and the structural element, all may use the plastic material, outside installs the assorted items to have the bumper, the fender, the wheel hub cap, the air deflector and so on; After the internal installation assorted items have in the display board, thevehicle door the board, the vice-display board, the sundry goods box lid, the chair, the guard shield and so on; The function and the structural element have the fuel tank, the radiator header, the spatial filter hood, the fan blade and so on.Statistics have indicated, our country in 2000 automobile output more than 200 tenthousand, the vehicle amounted to 1,380,000 tons with the plastic.Looked from the domestic and foreign automobile plastic application situation that, theautomobile plastic amount used already became one of weight automobileproduction technical level symbols.⑶、Injection of a molding formation as plastic workpiece most effective formationmethods because may by one time take shape each kind of structure complex, the size precise and has the metal to inlay a product, and the formation cycle isshort, may by mold multi-cavities, the productivity be high, when massproductions the cost isvery inexpensive, easy to realize the automatedproduction, therefore holds the extremely important status in the plasticprocessing profession.Statistics have indicated, plastic mold composition allmolds (including metal pattern) 38.2%, the plastic product gross weight about 32% is uses in injecting the formation, 80% above engineering plasticsproduct all must use the injection formation way production. 4. counts according to the customs, our country in 2000 altogether imported mold 977,000,000 US dollars, in which plastic molding forms altogether 550,000,000 US dollars, occupied for 56.3%,2001 years altogether to import mold 1,112,000,000 US dollars, in which plastic molding forms altogether 616,000,000 US dollars,accounted for 55.4%.From the variety, the import volume biggest is the plastic molding forms.⑷、Counts according to the customs, our country in 2000 altogether importedmold 977,000,000 US dollars, in which plastic molding forms altogether550,000,000 US dollars, occupied for 56.3%, 2001 years altogether to import mold 1,112,000,000 US dollars, in which plastic molding forms altogether616,000,000 US dollars, accounted for 55.4%.From the variety, the import volume biggest is the plastic molding forms.In compression molding the palstic material as powder or preforms is placed into a heated steel mold cavity,Since the parting surface is in a horizontal plane ,the upper half of the mold descends vertically.It closes the mold cavity and pressures for a predetermined period.A pressure of from 2 to 3 tons square inch and a temperaure at approximately 350F converts the plastic to a semiliquid which flows to all parts of the mold ually from 1 to 15 minutes is required for curing,altough a recently developed alkyd plastic will cure in less than 25 secends. The mold is then opended and the molded part removed.If metal insers are desired in the parts,they should be placed in the mold cavity on pins or in the holes before the plastic is loaded.Also, the preforms should be preheated before loading into the mold cavity to eliminate gases,inprove flow,and decrease curing time.Dieletric heating is a convenient method of heating the preforms.Since the plastic material is placed directly into the mold cavity,the mold itself can be simpler than those used for other molding precesses.Gates and sprues are unnecessary.This also results in a saving in material,because trimmed-off gates and sprues would be a complete loss of the thermosetting plastic.The press require the full attention of one operator.However,several smaller presses can be operated by one operator. The presses are conveniently located so the operator can easilymove from one to the next.By the time he gets around to a particular press again,that mold will be ready to open.the thermosetting plastics which harden under heat and pressure are suitable for compression molding and transfer molding.It is not practical to moid shermoplastic materials by these methods,since the molds would have to bealternately heated and cooled.In order to harden and eject thermoplastic parts form the mold,cooling would be necessary.Types of molds for compression molding.The molds used for compression molding are classified into four basic types, namely ,positive molds,landed positive mold,flash-type molds,and semipositive molds.In a positive mold the plunger on the upper mold enters the lower mold cavity.since there are no lands or stops on the lower die ,the plunger completely trap the plastic material and descends with full pressure on the charge.A dense part with good electrical and physical properties is produced.The amount of plastic placed in the die cavity must be accurately measured,since it determines the thickness of the part .A landed positive mold is similar to a positive mold except that lands are added to stop the travel of the plunger at predetermined point.In this case,the lands absorb some of the pressure that should be exerted on the parts.The thickness of the parts will be accurately controlled,but the density may vary cansideraby.In a flash-type mold,flash redges are added ti the top and bottom molds.As the upper mold exerts pressure on the plastic,excess material is forced out between the flash ridges where it forms flash.This flash is further compressed.becomes hardened,and finally stops the downard thavel of the upper mold.A slight excess of the plastic material is always chared to ensure sufficient pressurs to produce a dense molded part.This type of mold is widely used because it is comparatively easy to construct and it controls thickness and density within colse limits.The semipositive mold is a combination od the flash type and landed posive molds.In addition to the flash ridges,a land is employed to restrict the travel of the upper mold.三、The latheThe lathe is one of the most useful and versatile machines in the workshop, and capable of carrying out a wide variety of machining operations. The main components of the lathe are the headstock and tailstock at opposite ends of a bed , and a tool-post between them which holds the cutting tool. The tool-post stands on a cross-slide which enables it to move sidewards across the saddle or carriage as well as along it , depending on the kind of job it is doing .The ordinary centre lathe can accommendate only one tool at a time on the tool-post , but a burret lathe is capable of holding five or more tools on the revolving turret . The lathe bed must be very solid to prevent the machine from bending or twisting under stress.The headstock incorporates the driving and gear mechanism, and a spindle which holds the workpiece and causes it to rotate at a speed which depends largely on the diameter of the workpiece. A bar of large diameter should naturally rotate more slowly than a very thin bar , the cutting feed-shaft from the headstock drives the tool-post along the saddle , either forwards or backwards , at a fixed and uniform speed. This enables rotation of the shaft, and therefore the forward or backward movement of the tool-post. The gear which the operator will select depends on the type of metal which he is cutting and the amount of metal he has to cut off. For a deep or roughing cut the forward movement of the tool should be less than for a finishing cut.Centres are not suitable for every job on the lathe . The operator can replace them by various types of chucks, which hold the work between jaws, or by a front-plate, depending on the shape of work and the particular cutting operation. He will use a chuck, for example, to hold a short piece of work , or work for drilling , boring or screw-cutting .A transverse movement of the tool-post across the saddle enables the tool to cut across the face of the workpiece and give it a flat surface. For screw-cutting , the operator engages the leadscrew, a long screwed shaft which runs along in front of the bed and which rotates with the spindle. The lead-screw drives the tool-post forward along the carriage at the correct speed, and this ensures that the threads on the screw are of exactly the right pitch. The operator can select different gear speeds , and this will alter the ratio of spindle and laedscrew speeds and therefore alter the pitch of the threads. A reversing lever on the headstock enables him to reverse the movement of the carriage and so bring the tool back to its original position.The purpose of any machine tool is to remove metal. Each machine tool removes metal in a different way. For example , in one type (the lathe )metal is removed by a single point tool as the work is rotated , whereas in another type(the milling machine) a cutter is rotated and metal is removed as the work is progressed beneath it .Which machine tool is to be used for a particular job depends to a large extent upon the type of machining required . There is , however, a certain amount of overlapping and some machine tools can be utilized for several different operations but it must not be assumed that the particular machine tool is restricted to the operation shown.The machine tools which will be found in the modern toolroom are as follow：⑴Lathes for turning ,boring and screwcutting, ect. The primary purpose of the latheis to machine cylindrical forms. The contour is generated by rotating the work with respect to a single-point cutting tool.⑵Cylindrical grinding machines for the production of precision cylindrical surfaces.The cylindrical grinding machine is used for precision grinding cylindrical mould parts. Metal is removed by the action of abrasive grinding wheel which is broughtinto contact with a contra-rotating workpiece.⑶Shaping and planning machines for the reduction of steel blocks and plates to therequired thickness and for ‘squaring up’these plates .As the primary purpose of a shaping machine is to produce flat blocks. The workpiece is mounted on a table and a reciprocating single-point tool removes metal in a series of straight cuts.⑷Surface grinding machines for the production of precision flat surfaces . Anexcellent surface finish combined with accuracy can be achieved on hard or soft steel with the surface grinding machine. The workpiece is mounted on a table which is reciprocated beneath a rotating abrasive grinding wheel and metal is removed in a series of straight cuts.⑸Milling machines for the rapid removal of metal , for machining slots, recesses,boring holes, machining splines, etc. Milling is an operation in which metal is removed from a workpiece by a rotating milling cutter. The workpiece can be moved in three directions at right angles to each other with respect to the cutter.The three directions are longitudinal, transverse and vertical, respectively.⑹Tracer-controlled milling machines for the accurate reproduction of complexcavity and core forms.The principle of tracer-controlled milling machine is similar to that of the vertical milling machine in that an end mill cutter is used to remove metal in a series of cuts. With tracer-controlled milling, however , the required form is generated by causing a tracer, directly coupled to a cutting head , to followa template or a model.In addition to the above list of major machine tools there is, of course, ancillary equipment without which no toolroom would be complete. This includes power saws , drilling machines, toolpost grinders, hardening and polishing facilities, ect.四、Electric discharge machiningElectric discharge machining is the latest process being used extensively in the moldmaking field. It can be applied to soft and hard metals, and it exters no mechanical forces that might be detrimental to frail parts. The process is constantly being improved not only in terms of new machines being capable of producing better。
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