Rapid manufacturing and its Practical Versions - Assignment Example

Summary Rapid manufacturing has been in the making since the sixties but its practical versions became available only in the 1980’s. It has emerged as a major developing mode of manufacturing compared to conventional manufacturing processes employed over the centuries. There is strict credence to the belief that rapid manufacturing may well over take conventional manufacturing techniques and it may also replace them altogether in certain areas. Various modes of rapid manufacturing are available such as Selective Laser Sintering, Fused Deposition Modelling, Stereo Lithography, Laminated Object Manufacturing and Selective Laser Melting amongst others. Each method poses certain advantages and disadvantages over other system and so each method is suited to certain applications. In the longer run rapid manufacturing is poised to redefine manufacturing as we know it by creating a greater focus for additive manufacturing in place of subtractive manufacturing. Acknowledgement I would like to express my gratitude to { } for helping me complete the prerequisites to complete this research report. Table of Contents Summary 2 Acknowledgement 2 Table of Contents 3 Introduction 4 Methodology of Research 4 Details Of The Development Of Each Rapid Manufacturing Technology And Its Current Status 4 Selective Laser Sintering (SLS) 5 Fused Deposition Modelling (FDM) 6 Stereo Lithography (SLA) 8 Laminated Object Manufacturing (LOM) 10 Selective Laser Melting (SLM) 11 Details Of The Future Perspective Of Each Rapid Manufacturing Technology 12 Selective Laser Sintering (SLS) 12 Fused Deposition Modelling (FDM) 12 Stereo Lithography (SLA) 12 Laminated Object Manufacturing (LOM) 13 Selective Laser Melting (SLM) 13 Discussion on The Impact Of Rapid Manufacturing Technologies To Design And Manufacturing Practices In The Future 14 Conclusion 14 Bibliography 15 Introduction Rapid manufacturing is a manufacturing technique used to fabricate physical parts using 3D CAD (Computer Aided Design) files or through computer data based on additive and subtractive techniques. The basic contention is to minimise human intervention through automation. (Wright, 2001) The process is based on the concept of 3D printing which adds subsequent layers of material using 3D CAD models. The process can be dated back to the 1980’s and was subsequently labelled as rapid prototyping. Initially rapid manufacturing was used to manufacture design concept models only but with the passage of time rapid manufacturing has become competitive. Rapid manufacturing was initially favoured as it lowered costs in producing prototypes through the elimination for any need for tooling, dyes, forging or other such processes. Newer advances in rapid prototyping have made the technology competitive enough to warrant mass manufacturing through newer rapid prototyping machines. (RedEye, 2009) Various technologies for rapid manufacturing have developed over time and these will be discussed in terms of their development, details of future perspectives and the impacts of rapid manufacturing in design and manufacturing. Methodology of Research This research will be conducted using secondary methods based on literature review and internet searches. Official sources of information and journals will be utilised to conduct research. Details Of The Development Of Each Rapid Manufacturing Technology And Its Current Status Rapid manufacturing emerged as an idea in the 1960’s and two decades of development managed to produce working rapid prototyping devices. The concept behind rapid manufacturing is the use of additive processes in comparison to subtractive processes used for regular machining manufacturing applications. While subtractive manufacturing techniques are centred on removing excess material, additive manufacturing techniques are centred on adding the specified amount of material to manufacture products. Successive layers of material are deposited horizontally in small thicknesses until the final product is produced in rapid manufacturing. All rapid manufacturing operations are dependent on CAD (Computer Aided Design) and CAM (Computer Aided Manufacturing) processes and systems. Typically rapid manufacturing systems rely on STL (stereo lithography) and surface scans to generate data for physical models. There are myriad rapid manufacturing technologies in use and in development but this text will discuss major rapid manufacturing technologies only. Selective Laser Sintering (SLS) A high powered laser is utilised in SLS. Typical lasers include carbon dioxide lasers. The contention is to fuse small powder like particles of either plastic, ceramic, glass or metal through laser fusion. The laser element fuses powder material on a selective basis using 3D models of the desired product. A powder bed is included that houses the powder to manufacture the part. Initially powder is deposited on the powder bed and the laser scans a section. After each scan of the laser, the powder bed piston is lowered by a certain increment and new powder is deposited on top. The laser is applied again and the process repeats itself. Most SLS machines use pulse laser because fusion is a function of peak laser power rather than application of laser duration. The laser alone does not supply all the heat needed for fusion, instead the SLS machine preheats the subject powder to below its melting point so that the laser has to use as less energy as possible. (Prasad et al., 2005) SLS machines may use single component or two component powders which are either powder mixtures or coated powders. The single component powders are treated by lasers for surface melting. The solid non melted cores are fused to each other as well as to previous layers. (Prasad et al., 2005) Another major capability of SLS systems is the fact that they can process a wide variety of materials. The range of usable materials includes polymers (nylon, polystyrene), metals (titanium, steel, and alloys), green sands as well as composites. Around one hundred percent density can also be achieved in terms of material properties in comparison to conventional manufacturing processes. Another major advantage is that multiple parts can be manufactured simultaneously on the powder bed which raises productivity levels. Also the product being created does not require any support structures as the surrounding powder provides an effective support. Dr. Carl Deckard is accredited with developing and patenting SLS technology while at the University of Texas at Austin somewhere in the mid eighties. His work was sponsored by DARPA. (ProtoCAM, 2011) Fused Deposition Modelling (FDM) FDM is a leading additive manufacturing technology that was developed by S. Scott Crump in the late eighties. The technology was made commercially available in 1990. This technology allows prototyping, modelling as well as commercial production. Depending on the nature of the part being created, the FDM modelling device generates adequate support structures too. Support structures are often created out of another material and are disposable. Thermoplastics are used primarily for FDM. These thermoplastics are first liquefied and the deposited using an extrusion head. The extrusion head follows the path defined by the relevant CAD / CAM interface. Material is deposited in consecutive layers that are layered on top of each other. Extrusion begins with the lowest layer and finishes at the top layer. Often the material is deposited in layers that are as low in thickness as five thousands of an inch. The extrusion is additive by principle. Often a plastic wire or a metal filament is unwound from a coil which is used as the supply material for the extrusion head. The head is ended using an extrusion nozzle that can turn the flow of material on and off as desired. Stepper and servo motors are employed to move the extrusion head and nozzle in either direction. The FDM process can utilise several materials that are selected based on tradeoffs between temperature properties and strength. Typical FDM machines can easily utilise ABS (acrylonitrile butadiene styrene) polymers, polycaprolactones, waxes, polycarbonates as well as polyphenylsulfones. Supports used to support the product being created are generally made out of water soluble compounds. Generally when manufacturing is complete, the supports are dissolved using a weak sodium hydroxide solution. Stereo Lithography (SLA) Another additive manufacturing process is stereo lithography where certain photopolymers are used along with UV (ultra violet) lasers to fuse the polymers. The parts produced are using a layer to layer technique where successive layers are deposited. The resin used for SLA purposes is often liquid and the laser traces a certain cross section on each path over the liquid resin. The exposure of the liquid resin to UV lasers causes it to cure. The traced pattern solidifies as a result and tends to stick to the layer just below it. After each successive tracing and solidification routine takes place, the SLA platform rises in small increments. These increments can vary between two thousands and five thousands of an inch. This elevation procedure is followed by the movement of a resin coated blade that deposits newer material on top of the previous layers. This new layer is liquid and the entire tracing and solidification routine is repeated again. The entire part is formed in this manner layer by layer and once complete the excess resin is removed. The removal takes place through immersion in a chemical bath followed by a curing procedure in a UV oven. (Asberg et al., 1997) SLA techniques suffer from certain inherent problems that limit their commercial and pervasive use. The part being created needs to be supported using support structures that need to be embedded in the elevator. Moreover, as the 2D cross sections are created and the blade reapplies new material, the lateral strain produced tends to misalign the created cross section. This can be stopped by using adequately supporting structures that are created along with the original desired part. Supports therefore are a requirement of production and must be removed once the part is complete. Compared to other rapid manufacturing techniques, this technique can be seen to waste more material. (Kalpakjian & Schmid, 2006) Stereo lithography can be traced back to Charles W. Hull who invented a complete working arrangement in 1986 and patented it accordingly as US Patent 4,575,330 which was titled “Apparatus for Production of Three Dimensional Objects by Stereo Lithography”. (Photo Polymer, 2008) Laminated Object Manufacturing (LOM) LOM is differentiated from other rapid manufacturing techniques in its finishing of the product. The process relies on gluing or joining substrates of various substances successively as layers. The layers are often composed of plastic, paper or metal. The layers or laminates are already adhesive coated to ensure that they stick as soon as they are deposited. Each layer is successively joined and then cut into required shape using either a knife (or similar blade based device) or a laser cutter. Typically the laminates are heated and are then put in place with a heated roller. A laser typically traces out the required dimensions of the product to be fabricated. Cross hatches are employed next to remove the excess material that has been snipped off. The platform with the completed cross section moves down and out of the way of the cutter. A new sheet is installed using the heated roller technique listed above. The entire process repeats itself in a similar manner until the final product is created. (Laminated Object Manufacturing, 2006) Although LOM may seem to be a back water technique in rapid manufacturing but this is not true. Instead the LOM technique offers certain advantages that make it uniquely suited for certain applications. For one thing the materials used for LOM are cheaply and readily available. The paper models that are created using LOM possess wood like finish and workability characteristics making them highly suited to producing uniquely surfaced furniture. Moreover, LOM may be used to create relatively large parts as no chemical reactions are needed to complete the fusion process. Therefore, LOM is highly suited to applications such as making furniture or ornamental devices. (eFunda, 2011) LOM was initially developed by Helisys Inc. (now Cubic Technologies). Selective Laser Melting (SLM) SLM is a derivative of SLS and involves operations performed largely on metals. Typically ytterbium lasers are used as heating sources to melt and fuse metal powder. While SLS also serves polymers, SLM is more often directed at creating metal parts. The chief reason behind this is that SLS fuses the metal to a large degree only while SLM typically welds the metal together. The atmosphere within the working chamber of a SLM machine is void of oxygen (oxygen levels are kept below 500 ppm to avoid oxidation). (Abe et al., 2003) Efforts at welding metal powder using laser beams spans many decades tracing its origin to the sixties. The current drive to create SLM machines can be traced back to a project at the Fraunhofer Institute in Aachen Germany somewhere in the mid nineties. The developed process was commercialised by MTT Technologies (formerly known as MCP) in collaboration with the original researchers Dr. Fockele and Dr. Schwarze. (Gibson et al., 2010) SLM is generally used to create metal parts that possess intricate geometry such as thin walls or excessively curving helixes etc. It is also used to create thin walls as well as channels and hidden voids. Applications can be found in the aerospace and medical industry in large part. (Wohlers, 2010) Details Of The Future Perspective Of Each Rapid Manufacturing Technology Selective Laser Sintering (SLS) SLS is bound to grow especially as rapid manufacturing machines become cheaper to purchase. The wide range of applications of SLS is currently limited by the initial costs that range in the hundreds of thousands for one machine. However as SLS machines become cheaper their use will increase. Currently SLS machines are used to create products for the aerospace, medical, dental, architecture, automotive and other allied industries. Most of the produced products include specialised applications or spare parts such as jigs and fixtures or dyes. If SLS can be made cheap enough, most spares used in these industries will trace their origins to SLS manufacturing techniques. SLS is more of a commercial production technique than a prototyping technique. Fused Deposition Modelling (FDM) FDM has found use as both a rapid prototyping technology as well as a rapid manufacturing technology for commercial applications. The wide ranges of plastics that are used in FDM encourage its use as a commercial production technique for small and critical plastic products. Recently, the use of Ultem 9085 in FDM applications is pointing to the fact that FDM may find increasing use in aerospace and aviation application. Ultem 9085 is a preferred fire retardant used in aerospace and aviation based applications. Stereo Lithography (SLA) SLA is a largely expensive process in terms of rapid manufacturing. The typical resin used is between $80 and $210 per litre and a typical SLA machine can cost between $100,000 and $500,000. Typical applications of SLA products are master patterns for casting, blow molding, thermoforming etc. Although the more intricate master mold patterns produced can be justified in terms of the cost but pervasive application of SLA cannot be justified for all kinds of master patterns. Moreover, SLA is largely limited to the metal and plastic working industries for pattern creation. In these terms, the future of SLA seems limited to its current applications only. Only if the cost can be lowered further could there be chances that SLA use would find growth. SLA could still be used to create rapid prototypes which easily justify their costs. Laminated Object Manufacturing (LOM) LOM has been in use for a very long time and can be seen as the earliest of the rapid manufacturing technologies. It is being diversified as time passes and the conventional use for creating furniture through wood laminates use has given way to newer applications such as creating plastic and polymer parts. The dimensional tolerances achieved using LOM are often crude and could still be improved further. Moreover, the waste material is a constant disadvantage that is part of the process of LOM. These issues may seem to hold LOM’s future back but this is hardly the truth. This is because LOM makes it easy to manufacture large parts at relatively very low costs compared to other processes used in rapid manufacturing. This is the very reason why LOM is growing fastest compared to other rapid manufacturing techniques. Not only can LOM create interesting shapes for commercially viable industries but it also helps to lower increasing labour costs. Selective Laser Melting (SLM) SLM is still an expensive technique that is being utilised for specialised applications such as aerospace and medical devices etc. The need to control the atmosphere content and the energy costs needed to operate the lasers to produce enough energy for welding cum fusion are major reasons why SLM is still expensive and restricted to specialised applications. With the current trends in the development of SLM machines, the future seems to be restricted to specialised applications only. However, if the processing costs as well as the cost of metallic powders can be lowered far enough, SLM will find increasing use in the metal working industry. Discussion on The Impact Of Rapid Manufacturing Technologies To Design And Manufacturing Practices In The Future Rapid manufacturing technologies are set to redefine how conventional manufacturing is carried out. Rapid manufacturing has often been labelled as the industrial revolution of manufacturing. (Easton, 2008) In due course of time as 3D printing becomes cheaper there are significant chances that conventional manufacturing processes such as forging, casting and the like may eventually give way to rapid manufacturing. This may seem to be a tall claim right now but in the longer run 3D printing offers a one stop solution in comparison to conventional manufacturing. For example to manufacture a typical vehicle spindle, the manufacturer needs to create casting patterns, cast the spindle and machine the spindle to acceptable tolerances. In comparison, the 3D printing realm offers direct plug and play service for 3D printing machines where a CAD object can be translated into a physical object in no time at all. The move towards home based 3D printers signifies how popular rapid manufacturing is becoming. It also highlights that massive research is being undertaken in the field of 3D printing which will lead to substantial progress soon enough. Conclusion Rapid manufacturing offers a host of advantages over other conventional manufacturing processes as listed in the arguments above. However, currently rapid manufacturing is limited by certain factors namely cost and complication. With greater research applied to rapid manufacturing, there are large chances that rapid manufacturing will eventually overtake conventional manufacturing in most manufacturing sectors. Bibliography Abe, F. et al., 2003. Influence of forming conditions on the titanium model in rapid prototyping with the selective laser melting process. In Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science., 2003. Asberg, B. et al., 1997. Feasibility of design in stereolithography. Algorithmica, Special Issue on Computational Geometry in Manufacturing, 19(1-2), pp.61-83. eFunda, 2011. Highlights of Laminated Object Manufacturing. 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