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Rapid Prototyping & Manufacturing TechnologiesFig. 1.1 Differences between conventional machining and rapid prototyping1.3 Why RP&MThe application of the RP&M in the NPD can resolves the Fuzzy Front End – themessy getting started period of NPD process - would be relatively costly andtimely. However using RP&M enable manufacturers to schedule the right productbeing developed in a timely manner is the most important winning strategy. Thecombination of the RP&M and CAD technologies in blending with traditionaltechnologies and gradually formation of cross-functional team are the strategiesfor survival or strategies for empowering organization, people and facilities.1.4 Limitations of RP&MHigh precision RP machines are still expensive at around US$ 100 thousands to 1million and not easy to justify economically and many service bureaus in providingthe physical prototypes output services. However, as the RP technologies aregetting more mature while RP manufacturers are facing more head-to-headcompetition, the price will go down significantly in the near future such as thelaunch of V Flash priced at US$ 10 thousands. Most of the budget RP systems aredifficult to build parts with accuracy under +/-0.02mm and wall thickness under0.5mm. This is sufficient for prototypes built for concept evaluation and functionaltest.However, prototypes that will be used as master pattern for downstreamprocesses always require a much higher and consistent accuracy. Although thereare quite a large variety of materials that can be used in most RP processes, thephysical properties of the RP parts are normally inferior to those samples thatmade in proper materials and by the traditional tooling. The RP parts are notcomparable to traditional Computer Numerical Control machined (CNC) prototypeparts in the surface finishing, strength, elasticity, reflective index and othermaterial physical properties.Page 4IC Professional Training
1.5 The future market profile of RP&M systemsRapid Prototyping & Manufacturing TechnologiesThe future market profile of the rapid prototyping/manufacturing industry willhave two specific niches. The first one will be focused on Digital DirectManufacturing (DDM) of engineering parts for not only testing form fit, functionalevaluation, but also can be directly used in products. The second niche will belooking at the market requirement in another point of view. It will focus onconcept modeling or 3-Dimensional printing for design verification, preliminarymarketing tool and manufacturability studies. In this case, the most importantconsiderations are speed and low cost. The accuracy and resolution requirement isminimal so far it can provide the designer a reasonable representation of thedesign.2. Common Types of Rapid Prototyping TechnologiesWhile there are many ways in which one can classify the numerous RP systems inthe market, one of the better ways is to classify RP systems broadly by the initialform of its material, i.e. the material that the prototype or part is built with. In thismanner, all RP systems can be easily categorized into (1) liquid-based (2) solidbasedand (3) powder-based.Liquid-based RP systems have the initial form of its material in liquid state.Through a process commonly known as curing, the liquid is converted into thesolid state. The Stereolithography Apparatus (SLA) falls into this category.Solid-based RP systems encompass all forms of material in the solid state. In thiscontext, the solid form can include the shape in the form of wire, roll, laminates,pellets and powders. The Selective Laser Sintering (SLS), Three-DimensionalPrinting (3DP) Fused Deposition modeling (FDM) fall into this definition.2.1 Stereolithography Apparatus (SLA) – Liquid based RPStereolithography Apparatus (SLA) technology fabricates three-dimensional, solidobjects resin using a computer-directed, ultraviolet (UV) laser beam to curesuccessive layers of photo-sensitive polymer resin in a vat.SLA part is fabricated by laser spot instead of continues scanning on the resinwhich forms a thin solid layer on the surface of the liquid resin through thephotopolymerization. Figure 2.1 shows the schematic diagram of this spotscanning mechanism.Polymerization is the process of linking monomers and oligomers into largermolecules (polymers). When photoinitiators in the SLA resin are energized by thelaser spot energy exposure (Ec value in mJ/cm2) will undergoes thephotopolymerization process. It creates a thin layer of solid resin with thicknessabout 2-3 times thicker than the layer thickness (overcure). The total thickness ofPage 5IC Professional Training
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