Rapid Manufacturing-The Next Industrial Revolution

Transcription

1 INSTITUTE OF TECHNOLOGY, NIRMA UNIVERSITY, AHMEDABAD , DECEMBER, Rapid Manufacturing-The Next Industrial Revolution A. Prof. Deepa Yagnik A. Institute of Diploma Studies, Nirma University Abstract-- Rapid Prototyping (RP) is the term given to a set of processes that can quickly fabricate any given three-dimensional object into a model or prototype, directly from a CAD file via the additive deposition of individual cross-sectional layers of the part. With increased competition from the global economy & the challenge of delivering new customized products more quickly than before, several technologies collectively known as Rapid Manufacturing (RM) have been developed. Rapid manufacturing is a process that employs concept of RP to produce directly end-use items without molding, casting or machining. This is why RM is heralded as the next industrial revolution of digital age. This paper focus on different RM technologies, its advantages & applications. Keywords -- rapid prototyping, rapid manufacturing, multiphase jet solidification, selective laser sintering, laser engineered net shaping. R I. INTRODUCTION apid Prototyping (RP) is two decade old technology to quickly produce tangible objects directly from a 3D CAD model and is being used to shorten and simplify the product development cycle for many applications including aerospace, automobile and home appliances etc., It involves adding material successively, in layers, to create a solid of a predefined shape. Over the years, RP has evolved from producing prototypes for form, fit and functional testing to producing final end products for functional use. the market. Components made by RP techniques are no longer used only as visualization tools or for assembly testing. The next natural step for these techniques is to produce functional parts directly from metals and ceramics. This started the transition phase of rapid prototyping to rapid manufacturing. Nowadays, rapid manufacturing (RM), i.e. fabrication of end-use parts directly from RP machines, have been the subject of a lot of research. Experts have envisioned the wide ranging advantages that exist when rapid manufacturing is implemented. The application of different RM technologies focus on the initial cost and time savings that are realized when tooling is eliminated. The current future trend is shifting towards RM, thus eliminating the need for most prototype tooling and production tooling. RM is the next frontier for researchers, publishers & users of advance technologies. Fig 1 represents different RM technologies. II RAPID MANUFACTURING TECHNOLOGY OVERVIEW Research in the rapid manufacturing of metallic components is relatively new, there are currently numerous different directions in RM technology development. These technologies can be grouped according to their fundamental metal deposition working principles as seen in Figure2 Fig.1- Schematic representation of RM technology In the beginning, RP was mostly used for the fabrication of prototypes made from polymers as communication and inspection tools. The fabrication of conceptual and functional prototypes made from polymers is already well established in Fig.2- Classification of Rapid Manufacturing technologies (A) Non-laser based technologies: It involves the selective deposition of metal material. Currently, Multiphase Jet Solidification (MJS) is the only

2 2 INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN TECHNOLOGY, NUiCONE 2011 non-laser based technique being developed. It selectively deposits its preheated material through a nozzle. (B) Laser based technologies: It involves the use of a laser to selectively join the metallic material. As can be seen in Figure 2, this can be done through sintering, cladding, or binding. 1) Laser sintering It involves the use of a high powered laser to selectively melt the surfaces of pure metallic powders in order to create the part. The part typically undergoes subsequent infiltration in order to create a fully dense part. 2) Laser cladding It Uses an extremely high-powered laser, metal particles are completely melted and selectively deposited on a substrate. 3) Laser binding It involves the use of a laser to bind a second phase in order to hold the metallic particles together. These parts are then required to undergo a debinding stage and a sintering stage. Selective laser sintering (SLS) working principle is the use of a C02 laser to fuse and sinter metallic powder one layer at a time (fig-4). In this process a thin layer of powder is first deposited from the raised part-build cylinder onto the partbuild area. The laser beam guided by the galvano mirrors is scanned onto the powder bed to form solidified/sintered layers. The powder in other areas remains loose and acts as a support. After the building-area drops one-layer thickness (typically mm) another powder layer is deposited. The cycle is repeated until the 3-D part is complete. III DIFFERENT RAPID MANUFACTURING TECHNOLOGY Non laser technology - Multiphase Jet Solidification (MJS) Multiphase Jet Solidification (MJS) is a process in which a powder-binder mixture is passed through the machine as feedstock, where it is first heated above its solidification point to achieve a suitable viscosity (fig 3). It is then squeezed out of nozzle by a pumping system & deposited layer by layer (the deposition head unit is mounted on a xyz-table that is controlled by a computer system). Low viscous materials (liquefied substances or powder-binder~pastes) are extruded through an x-y-z~controlled jet and parts of different materials e.g. stainless steel are fabricated layer by layer up to the final extension. Fig.3- Working principle of MJS process Fig.4- Working principle of SLS process Laser technology Laser Engineered Net Shaping (LENS) Laser Engineered Net Shaping is able to fabricate fullydense metal parts with good metallurgical properties at reasonable speeds (fig -5). A high power laser is used to melt metal powder supplied coaxially to the focus of the laser beam through a deposition head (C). The laser beam typically travels through the center of the head and is focused to a small spot by one or more lenses (B). The X-Y table (D) is moved in raster fashion to fabricate each layer of the object. Typically the head is moved up vertically as each layer is completed. The laser beam may be delivered to the work by any convenient means. A simple right angle mirror (E) is shown, but fiber optics could also be used. Metal powders (A) are delivered and distributed around the circumference of the head either by gravity, or by using an inert, pressurized carrier gas (G). Even in cases where it s not required for feeding, an inert shroud gas (F) is typically used to shield the melt pool from atmospheric oxygen for better control of properties, and to promote layer to layer adhesion by providing better surface wetting. Laser technology - Selective laser sintering (SLS)

3 INSTITUTE OF TECHNOLOGY, NIRMA UNIVERSITY, AHMEDABAD , DECEMBER, A newer RP technology, Optoform uses viscous pastes as its working material.similar to SLA, Optoform uses a UV laser to solidify the paste layer by layer. The material is composed of resin, some fillers, and a photoinitiator. The building speed is about 25 mm/hour, and there is no waiting time during the recoating.after building on the Optoform machine, postprocessing is required consisting of debinding and sintering steps. Currently two types of polymers and one ceramic material are commercially offered. Research on the production of metal parts with this technology has been recently abandoned because of the poor resultant material properties. IV MATERALS Fig.5- Working principle of LENS process OTHER METAL RP TECHNOLOGIES # 3D Printing (3DP) This technology involves the use of a printer head to selectively deposit a binder polymer over a bed of metal powder. The selectively bound part, when later removed from the bed, is a relatively low-density (about 50%) Green part. The green part is then subsequently fired and infiltrated to make a dense metal part. Stainless steel-bronze parts have been made with this technology. # Shape Deposition Manufacturing (SDM) This technology combines laser cladding with subtractive machining. A laser is used to melt powdered metal in order to deposit metal; a milling machine is then used to create a nearnet shape component. This process has been proven to successfully make functionally graded materials. # Laminated Object Manufacturing (LOM) This technology has been traditionally used to cut stacks of paper layers with a laser. Recent research from Japan shows interest in using the same technology to create metal parts from several layers of cut sheet metal. #Ultrasonic Object Consolidation (UOC) This technology utilizes solid-state joining techniques to deposit layers of tape to form solid aluminum parts. The process involves depositing several layers of aluminum tape, followed by a trimming step in order to produce near-net shape parts.the process is extremely fast but is currently limited to aluminum. There exist limits on the aspect ratio of the part due to the trimming stage of the process. The bonds between each layer of the part also provide anisotropic material properties. Also, this technology does not enjoy the freedom to build complex geometries, such as overhanging structure, cannot be built. # Optoform Metals: A variety of metals are currently available including alloys of 17-4, 15-5 or 316L Stainless Steel, Maraging Steel, Cobalt Chromium (Stellites), Inconel 625 and 718, Aluminum alloys ( AlSi10Mg) and Titanium alloys (e.g. Ti6AlV4) Polymers: The variety of non-metallic materials used includes an array of photopolymers based on acrylics as well as an assortment of wax-like substances, polyamide powder (filled or not with glass/carbon fibers or aluminum) and ABS plastic. Addition of rigid particles and clay to polymers can produce a number of desirable effects on the mechanical properties of parts. The knowledge of existing materials and the nature of complexity in processing them by laser will be helpful in achieving functional requirements of parts for present and future applications. Although many materials have been developed, there is still a need for research into new materials. It should be noted that RM processes are still a relatively new and therefore continued development of the technology and understanding of process fundamentals is needed to carry the technique forward. V ADVANTAGES OF RAPID MANUFACTURING Shorter cycle time Part building can be made directly from CAD data resulting in much shorter process chain compared to traditional subtractive process No tooling Absence of tooling requirement contributes to significant lead time reduction. Complex geometrical designs The layer by layer building mechanism allows greater geometrical freedom in making parts which were previously impossible with traditional methods. Automation Process being highly automated, allows unattended overnight part building, increase machine utilization & reduce unit cost.

4 4 INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN TECHNOLOGY, NUiCONE 2011 Low material waste Since the process only forms the desired part, there is almost no waste formed in contrast to conventional machining. The absence of waste enhances energy efficiency, as energy is not used to transport or dispose of waste. With the elimination of traditional parts machining, petroleum-based cooling fluids are no longer a necessary waste byproduct. Energy Efficiency Only the energy necessary to form the part is expended, and waste is eliminated. This contrasts with conventional machining, in which energy is used to smelt metal into ingots, which become billet materials. These billet materials are then machined, removing a great deal of the material to produce the final part. The energy used to create the original block of material is wasted. VI APPLICATIONS Rapid tooling To address a wider range of applications sooner, Rapid prototyping is also often used as the starting point for making conventional fabrication processes faster, cheaper and better. Rapid prototyping is used in two ways to accomplish this: Molds may be directly fabricated by an RP system, or RPgenerated parts can be used as patterns for fabricating a mold. Rapid tooling was one of the first, important application for rapid manufacturing. Tooling is a low-volume, highlycustomized product & engineers were early to see the potential benefits. Rapid tooling can provide dramatically shortened fabrication time while lowering costs. In high-value applications such as the fabrication of injection molds, typical savings cited are in the 10% to 25% range, & literally months can frequently be taken off the time to obtain parts (fig -6). Fig.7 - Injection Mold with conformal cooling channel fabricated by LENS Aerospace The aerospace industry has been one of the early adopters of rapid manufacturing technology. Parts for aircraft are made in small quantities, are often complex and must meet stringent requirements. Price is almost always secondary to function. This is essentially the definition of a high value-added application - which is exactly the type of application that rapid manufacturing is most appropriate for at present. Parts for the International Space Station and other projects were being made as long as several years ago by Boeing using selective laser sintering. A major area of interest is in the application of additive manufacturing technology to the fabrication of jet engine components. For example, turbine blades have complex shapes and must meet extremely stringent specifications. Several methods of using additive fabrication to make highstrength blades with single crystal structures are being investigated. Rapid manufacturing technologies can be used to improve blade finishes and for repair, and laser powder forming technologies for fabricating sensors within blades. Fig.8 Impellers fabricated by SLS process Fig.6 - Injection mold fabricated by LENS Advanced injection molds can also be fabricated with conformal cooling channels (fig -7) and using multiple and/or graded materials to further improve thermal and wear characteristics. These enhancements, unique to additive fabrication, typically lead to a 20 to 30% increase in throughput for a mold. Fig.9 Titanium engine valve fabricated by LENS process Automotive

5 INSTITUTE OF TECHNOLOGY, NIRMA UNIVERSITY, AHMEDABAD , DECEMBER, Formula 1 car parts Customized dashboard air ducts Custom seats, steering wheels etc. Military Weapons and Parts Customize warheads: Additive fabrication allows producing complex hollow features that optimize weight and inertia. Additive technologies which produce more robust parts are most frequently used in military applications with this technique it would be possible to customize warheads with features designed for specific missions. Wheels for tracked vehicles such as tanks: Laminated object manufacturing (LOM)-based method is being put to use in embedding sensors and electronic systems to provide remote monitoring of vehicle component condition and engine health. The technique is also used in making armor from composites and in field-repair of titanium and other types of parts. complex devices would automatically deliver medicine directly to the organ. Dental Numerous rapid manufacturing approaches to the fabrication of dental restorations are commercially available or under development. These range from using a model generated by RP methods for casting dental materials, to the direct fabrication of the dental restorations themselves. Direct metal laser sintering (DMLS) technology to fabricate the metal framework of a bridge with up to six teeth from a specially-developed cobalt-chrome alloy. The building time of an individual crown works out to only three minutes. This contrasts sharply with the manual process which permits a trained technician to make only about ten crowns in an entire workday. Fig 10 Additively fabricated warhead Medical Rapid manufacturing technology can make pills with tightlycontrolled time release profiles. For example, dosage forms can be produced to provide pulsed, monotonic, rapid, or constant release. Multiple drugs in the same pill can be synchronized with each other. One use of this technique is to optimize dosage timing while providing precisely synchronized relief from side-effects with a second drug. It's also possible to isolate a toxic core within a non-toxic region of a pill. This can be helpful in lowering exposure of manufacturing personnel to harmful ingredients or in providing more effective drug release to a patient. An expert system can be used to drive an additive fabrication process for producing small batches of pills with varying release profiles, sizes, internal architectures, active ingredient concentrations and other characteristics. This technique would be useful for optimizing dosages or in drug testing. Fast-dissolving medication forms can be prepared as well as tiny pills for implanting at the root of a tooth or drug delivery devices for attaching to the outer surface of the eye. These Fig.11 bridge by DMLS It's no longer necessary for technicians to mount, embed, cast, de-flask or spend much time cleaning the molded product. The frameworks emerge from the machine at full density and ready to be veneered with ceramic after very little finishing. The slight roughness of the sintered parts also works to good advantage in this application improving the adhesion of the ceramic. Another good example is the ability of Three Dimensional Printing to accurately match tooth color. Sports Helmets, protective & other wearable accessories, footwear, bats, rackets, grips, dive fins & face masks for scuba, recoil pads, sighting ribs & other custom gun components etc. A special heat-reflective helmet was made for a Dutch sculler who competed at the 2004 Athens Olympics. The helmet was designed to reflect sunlight without restricting airflow for optimal heat exchange, and was made from nylon using selective laser sintering. Additive fabrication of golf club heads is one of the first applications

6 6 INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN TECHNOLOGY, NUiCONE 2011 Consumer Items Custom jewelry has long been made using rapid prototyping to create wax and other types of patterns for transfer into precious metals Other fashion item is shoes for the fashion runway Fashion accessories for the home are also possible, in the form of custom lampshades and furnishings. Textile Accessory items such as zippers, grommets and belts can be fabricated right along with a garment to either lower costs and/or provide unique designs. It may also be possible to fabricate the garment in the folded state Industrial Applications Processes such as selective laser sintering (SLS) and Three Dimensional Printing (3DP), which use intrinsic materials in a powdered state, frequently produce parts which are porous in nature. While this is often undesirable and must be corrected by secondary operations such as infiltration, there are plenty of parts like Filters, Gas storage cells, Batteries etc. for which porosity is a functional requirement. Many of these can take advantage of rapid manufacturing. Filters: Three dimensional printing processes has been used in the past to fabricate large, efficient ceramic filters for coalfired power stations, diesel engines and food manufacturing applications. Filters made by rapid manufacturing are generally geometrically complex and offer improved characteristics such as low back-pressure. Additional work is going in filter fabrication for biomedical and life science applications especially using SLS technology. VII Conclusions: Rapid Manufacturing has a promising future with a powerful list of potential benefits. Rapid manufactured parts are especially suitable for the fabrication of small number of pieces and mass customization. Direct fabrication of metal products of high density and excellent mechanical properties is possible by using rapid manufacturing techniques. The aeronautic, automotive and medical industries are the main markets. VIII References: [1] N.Hopkinson, R.J.M. Hague, P.M.Dickens- Rapid manufacturing [2] [3] Christopher B. Williams, Rapid Prototyping with Metals:A Review of Technology and Associated Material Properties [4] Edson Costa Santosa, Masanari Shiomia,, Kozo Osakadaa, Tahar Laouib, Rapid manufacturing of metal components by laser forming [5] F. Miani,DIEGM University of Udine, Via delle Scienze 208, I Udine Italy, Recent developments of direct metal laser sintering [6]Worldwide guide to rapid prototyping, [7]Pham, D.T., Dimov, S.S. and Lacan, F. Selective laser sintering: Applications and Technological capabilities, Jonourall.of Eng. Manuf. Vol. 213, 1999 pp Porus Machine Parts: The additive fabrication of heated manifolds, nozzles and similar components used in injection molding provides greater functionality than can be obtained with standard techniques. The devices are made from powdered metals or other materials and infiltrated with thermally conductive materials. Biomedical Applications The future of bio-manufacturing which combines principles of RP and Bio-science can form complicated bio tissue scaffolds, is a potential technology to make artificial organs. fig.12 fig.13 Figure 12 shows final metal implant made by FDM Figure 13 shows titanium hip implant made by LENS