Rapid prototyping and part manufacturing technology

Knowledge sharing by Guangdong Shunde Teamwork Model Technology Co., Ltd, whom with over 20 years rapid prototyping experience.

Email: ken@gdtwmx.com

Website: www.gdtwmx.com

RP (Rapid Prototyping) technology was born in the late 1980s, and the rapid prototyping (prototype) technology developed in the 1990s is recognized as a major breakthrough in the field of manufacturing technology in recent years. Its impact on manufacturing can be related to numerical control technology. The appearance is quite beautiful. RP system integrates mechanical engineering, CAD, numerical control technology, laser technology and material science technology. It can automatically, directly, quickly and accurately transform design ideas into prototypes with certain structure and function or directly manufacture parts, so that product design can be made. Rapid evaluation, modification and functional testing have effectively shortened the product development cycle, and can quickly respond to market demands and improve the competitiveness of enterprises.

The rapid prototyping technology completely eliminates the traditional “removal” machining method (partially removing the material on the blank larger than the workpiece to obtain the workpiece), and adopts a new “growth” stacking method (using a layer of small blanks to gradually stack into large workpieces). , the complex 3D machining is decomposed into a simple two-dimensional machining combination), therefore, it does not have to use traditional machining machines and tooling, only 10% to 30% of the working time and 20% to 35% of the traditional processing method At a cost, product samples or molds can be produced directly. Rapid prototyping has the above-mentioned outstanding advantages, so it has developed rapidly in recent years. It has become a pillar technology in modern advanced manufacturing technology and an indispensable means to realize Concurrent Engineering.

First, the background generated by RP&M technology

With the formation of global market integration, the competition in the manufacturing industry is fierce, and the speed of product development has increasingly become the main contradiction of market competition. In this case, the ability (cost and cycle) of autonomous rapid product development (rapid design and rapid tooling manufacturing) becomes the strength of the global competitiveness of the manufacturing industry. At the same time, in order to meet the increasingly individualized market demand, the manufacturing industry also requires strong flexibility in manufacturing technology, and can organize production in small batches or even in a single piece without increasing the cost of the product. Therefore, the speed of product development and the flexibility of manufacturing technology become critical.

For half a century, the development and popularization of technologies such as computers, CAD/CAM, NC, materials and lasers have also laid the foundation for the emergence of new manufacturing technologies on a technical level.

It is in this social context that RP&M-Rapid Prototyping/Parts Manufacturing was produced in the United States in the late 1980s and rapidly expanded to Europe and Japan, which is considered to be the field of manufacturing technology in recent years. A major breakthrough.

Second, the principle and main methods of RP&M

RP&M technology refers to the general technical name for the rapid manufacture of three-dimensional entities of arbitrary complex shapes by the CAD model of parts under computer control and management. It is the integration of many modern advanced technologies. Rapid prototyping technology uses the discrete/stacking forming principle to obtain the stacked paths and ways by discretely, and “stack” the materials by precise stacking to form complex three-dimensional entities. The analogy of the rapid prototyping system to the "3DSolid Printer" is very vivid.

The discrete/stacking process begins with a three-dimensional CAD model: first discretizes the CAD model, and cuts a certain direction (often taking the Z direction) into many layers, ie, layering, which is an information processing process; The layers are stacked in sequence, and the layers are combined to form a three-dimensional solid part, which is the physical embodiment of the CAD model. Each RP device and its operating principle are based on a layer-by-layer overlay process.

There are more than 30 specific processes for RP&M technology, most of which were developed by the United States. Here are the five most mature ways.

1. Three-dimensional printing (SLA, Stereolithgraphy Apparatus) forming technology

The basic working principle: the surface of the photosensitive resin is scanned by ultraviolet laser, so that it can be solidified regularly, from point to line, then to the surface, to complete the construction of one layer, each time generating a layer of the part. During the scanning process, only when the exposure amount of the laser exceeds the threshold energy required for the curing of the resin, the liquid resin undergoes polymerization to form a solid state. Therefore, during the scanning process, the scanning speed is automatically adjusted for different amounts of curing depth to match the amount of exposure produced and the amount of exposure required to cure a certain depth. After each layer has been cured, the lifting table is moved a distance of one ply thickness, and then the resin is applied to the previous layer to build a layer. So repeatedly, each new layer is adhered to the previous layer until the last layer of the part is made, becoming a three-dimensional entity. After the parts are stacked, some necessary post-processing is performed on the parts, and the entire manufacturing process is completed.

2. Fused Deposition Modeling

Fused deposition molding refers to melting a hot melt material (ABS, nylon or wax) through a heater, and extruding the filament during the movement of the moving head, and depositing a thin layer according to the sectional shape of the part, so that the layer is stacked layer by layer. Make a part. During the deposition process, the nozzle is moved along the XY by the control of the horizontal stratification data, and the semi-flow fused filament is extruded from the FDM nozzle, and the amount of material flowing out from the extrusion head hole and the moving speed of the nozzle must be precisely controlled. It solidifies quickly when bonded to the previous layer, and the entire part is made on one piston. The piston can move up and down. When the layer is finished, the piston descends, leaving space for the next layer to be layered. FDM can be used in a wide variety of materials, and any material with thermoplastic properties can be used as a candidate.

3. Selective Laser Sintering (SLS)

The process utilizes the heat provided by the infrared laser beam to melt the thermoplastic material to form a three-dimensional part. A thin layer of thermoplastic powder material is evenly spread on the production area, and then the cross-sectional shape of the part is scanned on the surface of the powder by laser. The laser is scanned to form a solid, and the laser is not scanned, and the powder is still used as the next layer. The support can be removed after the forming is completed. After the upper layer is finished, a layer of powder is laid and the next layer is scanned. The process of layering and sintering of the selection is repeated until the last layer. A 3D solid is selected. Burned out. The equipment used by SLS is a laser, and the raw materials used are wax, polycarbonate, nylon, slender nylon, synthetic nylon and Metal Materials.

4.Laminated object manufacturing (LOM)

Layer-by-layer object fabrication techniques are a technique for manufacturing parts by layer-by-layer laser shear foil. The laser is used to cut the contour of the layer part, and the part other than the contour of the part is laser-cut into mesh-like pieces to be removed after the part is finished. Each layer of foil is coated with a hot sol, adhered to the previous layer by heat and pressure, and the layer of foil is layered into a solid block. When all the layers are bonded and sheared, the entire part is embedded in a large piece of support material, and the supporting pieces are removed to obtain the desired three-dimensional solid. The foil referred to herein may be a coated paper (paper coated with an adhesive coating), a coated ceramic foil, a metal foil or a foil of another material.

5. Solid Grinding (SGC, Solid Ground Curing)

It uses Mask technology to make a layer of photocurable resin as a whole, and it is not formed by layer-by-point illumination like SL equipment. The UV rays are irradiated onto the surface of a thin layer of liquid photosensitive resin through a glass cover. The light-transmissive portion of the glass cover has the same cross-sectional shape as the part, the cross-sectional shape of the part is solidified, and the rest is still a liquid resin, which is sucked off and then replaced with wax. it. The next layer of parts can be made on this basis. When all the layers of the part are made, the whole part is embedded in a large piece of wax. The wax can be removed by melting, and the rest is the part formed from the fully cured resin.

In addition, there are some more mature RP technologies, such as 3DP (Three-Dimensional Printing) process, namely 3D Printing or 3D printing, which uses a point-by-point spray adhesive to bond powder materials to make prototypes; BPM (Ballistic Particle) Manufacturing process, that is, ballistic particle manufacturing, which uses a nozzle with five-axis degrees of freedom to spray molten material to make a prototype; PCM (Patternless Casting Manufacturing) process, that is, no wood-die casting, which uses a point-by-point spray adhesive and The catalyst method is used to achieve the bonding between cast sand grains. This technology was successfully developed by Tsinghua University; the MJS (Multiple Jet Solidification) process, also known as multi-phase jet solidification, uses a piston to extrude molten material to continuously squeeze it. The nozzle method is used for stack forming; the CC (Contour Craft) process, also known as the contour forming process, uses a combination of a stacked profile and a cast molten material to make a prototype, which uses a simple mold for stacking contours. .

Third, the unique characteristics of RP&M technology

RP&M technology is different from traditional removal forming (such as turning, milling, planing, grinding, etc.), assembling (such as welding), or forced forming (such as casting, forging, powder metallurgy) and other processing methods, but using material accumulation Prototyping parts prototypes, rapid prototyping technology demonstrates the advantages of the following aspects over many traditional processing methods. (1) Directly driven by the CAD model, it is of great significance to shorten the product development cycle, reduce development costs and improve the competitiveness of the enterprise market by automatically, quickly and accurately transforming the design ideas into product prototypes of certain functions or even directly manufacturing parts.

(2) It is possible to quickly and directly produce arbitrarily complex parts without any tools, molds and tooling fixtures, without the limitations of the tools in the conventional machining methods.

(3) In the process of surface manufacturing, the transformation (layering) of CAD data can be fully automated, rather than the need for sophisticated manual technicians in CNC Machining to convert into complete process NC code.

(4) The processing of arbitrarily complex parts is only required to be performed on one piece of equipment, and no preparation work such as conventional tools or tooling is required. The development cost and cycle of new products have been greatly shortened, and the processing efficiency is far better than that of CNC machining.

(5) Equipment investment is lower than Cnc Machine tools.

(6) No intervention or less intervention during the forming process.

Fourth, the application of RP&M technology

The application of RP&M technology is developing rapidly. A notable indicator is the rapid increase in the number and revenue of RP&M service organizations. In the mid-to-late 1990s, the number of foreign RP&M services increased at a rate of 59% per year. It can be said that foreign countries have entered the RP&M as an important part of product development from the familiar, wait-and-see, and tentative application stages of RP&M processes, and improve products. The stage of developing quality and speeding up product development. Rapid prototyping technology greatly reduces the risk of new product development and shortens the development cycle of new products.

RP&M has been widely used in various fields of the national economy. In the early days of the RP industry, the automotive and aerospace industries dominated the RP market, which accounted for more than half of the market, but RP quickly introduced to other industries. It is currently used in general manufacturing, household appliances, aerospace, engineering structural model manufacturing, aesthetics and related engineering, medical rehabilitation and archaeology, and is still evolving into new areas.

Rapid Tooling technology developed in the manufacturing industry based on the RP system, Quick Casting and Quick Powder Sintering for fast parts Manufacturing. The following are some of the main aspects of RP&M applications. 1. Application in Product Design - Rapid Product Development The application of RPDRP&M in RPD is shown in Figure 1.

The key role and significance of RP&M in product development is obvious. We use CAD technology, rapid prototyping technology and rapid prototyping to complete the design and shape work, saving time and outstanding benefits. It is not subject to any limitations of complex shapes and can quickly turn a design on a computer into a physical prototype that can be further evaluated. The RP&M series of devices provides users with not only a conceptual model, but to a large extent, it provides products that can be fully validated from fit, assembly and performance testing.

The model generated by the RP is also a better intermediary for the communication between the design department and the non-technical department. Can significantly improve the success rate of new products into production. In view of this, foreign countries often use rapid prototyping systems as peripheral devices for CAD systems.

In general, using QRP&M rapid product development technology can reduce product development costs by 30% to 70% and reduce development time by more than 50%. For example, an automobile company adopts RP&M technology to meet the new emission standards of the country. The development cycle is shortened from 4 months to 1 month in the traditional method, which greatly shortens the time-to-market of its new products. Another example is that the optical camera body uses RP&M technology in only 3 to 5 days (from CAD modeling to prototyping), which costs 5000 marks, while the traditional method takes at least 1 month and consumes 30,000 marks.

At present, laser rapid prototyping technology has been maturely applied to product design evaluation and review, product engineering function test, etc., and has become a means of communication between manufacturers and customers.

2. Quick Tool (RT, Rapid Tooling)

Molds are an important aspect of rapid tool manufacturing technology applications, and rapid prototyping and automated manufacturing ensure rapid tooling.

The RP prototype is accurately copied into a mold by means of silicone rubber, metal powder, epoxy resin powder and low melting point alloy. The life of these simple molds is 50 to 1000 pieces, which is suitable for the trial production stage. For the manufacture of long-life steel molds, it is a three-dimensional lap from the original shape, grinding the whole graphite electrode with a lap, and then processing the steel mold on the EDM machine with electrodes. This process is characterized by fast and efficient, time-consuming 1/5 of traditional manufacturing, and improved accuracy.

Using RP/RT technology to manufacture molds compared to traditional CNC machining methods, the cycle is shortened by 1/3 to 1/10, and the cost is reduced by 1/3 to 1/5.

The solid model generated by RP is used as the core or mold sleeve, and combined with the techniques of precision casting, powder sintering or electrode grinding, it can quickly manufacture the functional molds or tooling equipment required for the production of the enterprise. The manufacturing cycle can be compared with the traditional Cnc Cutting method. Shorten by 30% to 40%, but the cost is reduced by 35% to 70%. The higher the geometric complexity of the mold, the more significant this benefit.

3. Fast direct manufacturing

Rapid prototyping technology can also be used to make plastic, ceramic, metal and various composite parts using material accumulation.

V. Relationship between RP&M and related technologies

RP&M integrates cutting-edge technologies in various disciplines such as mechanical engineering, computer control, CAD, numerical control technology, inspection technology, and laser materials. It is a typical high-tech.

1. Relationship between RP&M and CAD technology

The generation and development of CAD technology not only provides a simple and easy means for people to quickly display and modify the design, but more importantly, this method can enable people to obtain complete data, easy to modify and further processing, such as processing Data or data format files required to form RP&M, etc. Obviously, CAD is the premise and foundation for implementing RP&M, and it is often the bottleneck of RP&M in application. At the same time, the development of RP&M technology has promoted the development of CAD technology, such as data exchange interfaces and layered software.

2. Relationship between RP&M technology and materials science

Materials are the key to achieving RP&M. Each RP&M process has unique requirements for its materials. For example, SLA processes use specialty photocurable resins, LOM processes use adhesive-coated paper, and FDM processes use wax, ABS, and nylon. Etc., SLS uses a variety of metal and non-metal powder materials. The nature of the material not only affects the quality of the prototype, but also has a decisive influence on the application of the prototype. More importantly, it is a guarantee of the feasibility of the forming process. The development of materials science, especially the emergence of new materials, will have a major impact on the development of RP&M technology. At the same time, the development of RP&M technology will put forward new requirements for materials science and promote the development of material design technology.

3. Relationship between RP&M and CNC technology

At present, these four mature processes, SLA, LOM, SLS, FDM, etc. must use numerical control technology to achieve their forming motion control. In addition, the application of numerical control technology in RP&M technology also includes the control of processing parameters. Such as the compensation system in the SLA process, temperature compensation, power control and material feed control in LOM and FDM processes. Compared with the cutting CNC technology, RP&M requires fast scanning speed, high parking accuracy and low load. CNC technology is the basis of RP&M technology, and RP&M technology also proposes new research topics for CNC technology.

4. Relationship between RP&M and laser technology

The development and application of laser technology is one of the prerequisites for RP&M technology, and it is also a guarantee for the further development of RP&M technology. There are two main types of forming methods for RP&M technology: one is laser-based photocuring, cutting or melting; the other is non-laser direct stacking. The laser has the characteristics of energy concentration, easy control, small spot size and constant wavelength, especially suitable for RP&M technology. At present, the development is relatively complete, and the RP&M processes that use more applications, such as SLA, LOM, and SLS, use laser as the energy source.

5. Relationship between RP&M and other related technologies

In addition to being closely related to the above disciplines, RP&M technology is closely related to mechanical science, modern design theory, electronic technology and testing technology. Mechanical science laid the foundation of RP&M's process, determined the main framework and application goals of RP&M technology; modern design theory provided scientific theoretical guidance for prototype design; electronic and information technology integrated the subsystems of RP&M technology to form coordination The whole; the inspection technology ensures the quality of the form.

In short, RP&M technology is a multi-disciplinary technology integration. It is the result of coordinated development of various disciplines, and at the same time, it adds new research content to the development of various disciplines. Sixth, the development of RP&M technology

RP&M technology is one of the fastest growing manufacturing technologies in the world. It has been in the prosperous stage since its first appearance in the United States in 1986. It is known as a major revolutionary breakthrough in the industry in the past 10 years. In the past, the world installed a total of 300 units, and by 1995 the world installed capacity of 1,000 units, distributed in more than 40 countries on six continents. According to the 1998 market research report of Wohlers Associates, Inc., the average annual sales of RP&M equipment increased by 58.7% from 1993 to 1997, and the RP&M output increased at an average annual rate of 53.6%. In 2001, there were 8,000 sets of RP equipment in the world, distributed in more than 60 countries and regions, and the United States and Japan accounted for 60%. The main reason why RP&M technology is so popular is that it can quickly turn design ideas into three-dimensional entities with certain structure and function, and produce prototypes and even parts at low cost, which greatly meets the rapid development of new products in today's increasingly competitive market. Claim.

With the rapid development of RP&M technology, the number of institutions studying RP&M technology in the world is increasing. According to statistics, hundreds of universities, research institutions and enterprises in the world are currently researching and developing RP&M technology. The research and application of foreign RP&M technology is mainly concentrated in the United States, Europe and Japan. In terms of technology, materials and applications, the overall situation is that the United States is ahead of Europe and Japan, and Europe and Japan are equally divided. China's development in this area started late, but it has developed rapidly. According to Wohlers Associates, the United States, in 2002, the number of RP&M equipment in China was second only to the United States and Japan, ranking third in the world.

1. Foreign development status

(1) Development of RP&M process equipment

At present, RP&M's process equipment is developing very fast, and many companies have developed their own equipment. There are seven major RP&M manufacturers in the United States, namely 3Dsystmes, Helisys, DTM, Stratasys, Sanders, Prototype, Soligen and BPM, of which BPM has closed down due to poor management. There are six in Japan, namely CMET, D-MEC, Teijin Selki, Kira Corp, Mitsui Zosen and Denken Engineering. There are three in Europe, namely EOS in Germany, Cubital in Israel and F&S in Israel.

(2) Development of RP&M forming materials

Forming materials are a key part of the development of RP&M technology. The forming materials currently used in foreign countries are already abundant, as shown in Table 1.

(3) Development of RP&M software

Software is the soul of the RP&M system. Among them, the data conversion and processing software as a CAD to RP interface is one of the keys.

Major foreign RP&M system manufacturers generally develop their own data conversion interface software, such as 3D SYSTEM's ACES, QuickCast, Helisys' LOMSIice, DTM's Rapid Tool, Stratasys' Quicklice, Supprtwoks, AutoGen, Cubital's SoliderDFE, Sander Prototype ProtBuild and ProtoSupporl, etc. Due to the difficulty and relative independence of CAD and RP&M data conversion interface software development, many third-party softwares have emerged as bridges between CAD and RP systems. Some of the more well-known third-party interface softwares in foreign countries include: Bridge Works, Solid View of Solid Concept, Magicics of Materialise of Belgium, STL Manager of POGD of the United States, Still View of American Igore Tebelev, and Surface of American Imageware. RP&M, etc.

2. Status quo of China's RP&M development

China's research on this new technology started from the "Eighth Five-Year Plan" period and made breakthrough progress during the "Ninth Five-Year Plan" period. In the first year of the "Ninth Five-Year Plan", the government listed the technology in the "Ninth Five-Year Plan" project. The National Natural Science Foundation also listed the RP as a key project for advanced manufacturing technology. At the same time, in the "Ninth Five-Year Plan" national scientific and technological research, Advanced manufacturing technology is listed as one of the key areas of funding, and several important aspects of advanced manufacturing technologies, such as precision forming, CAD promotion, parallel design and concurrent engineering, agile manufacturing, virtual manufacturing, etc. are all related to RP. Even the main support is RP. This marks the beginning of a new level of domestic RP&M technology research.

China has developed four RP&M processes, equipment and supporting materials such as SLA, LOM, FDM and SLS, and its scientific and technological achievements have been commercialized. In 2002, the number of rapid prototyping equipment in China was nearly 1,000 sets, ranking second in the world after the United States and Japan, 60% of which were made by China. China has independently developed several rapid prototyping manufacturing technologies such as moldless sand manufacturing (PLC), low temperature ice type (LIR P) process and ultraviolet light rapid prototyping machine without laser, which has attracted great attention from domestic and foreign counterparts.