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RAPID TOOL

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Rapid Tool Rapid Tool is a technology invented by DTM Corporation to produce metal molds for plastic injection molding directly from the SLS Sinterstation. The molds are capable of being used in conventional injection molding machines to mold the final product with the functional material [16]. The CAD data is fed into the SinterstationTM which bonds polymeric binder coated metal beads together using the Selective Laser Sintering (SLS) process. Next, debinding takes place and the green part is cured and infiltrated with copper to make it solid. The furnace cycle is about 40 hours with the finished part having similar properties equivalent to aluminum. The finished mold can be easily machined. Shrinkage is reported to be no more than 2%, which is compensated for in the software. Typical time frames allow relatively complex molds to be produced in two weeks as compared to 6 to 12 weeks using conventional techniques. The finished mold is capable of producing up to tens of thousands injection-molded parts before breaking down. Laminated Metal Tooling This is another method that may prove promising for RT applications. The process applies metal laminated sheets with the Laminated Object Manufacturing (LOM) method. The sheets can be made of steel or any ther material which can be cut by the appropriate means, for example by CO2 laser, water jet, or milling, based on the LOM principle [17]. The CAD 3D data provides the sliced 2D information for cutting the sheets layer by layer. However, instead of bonding each layer as it is cut, the layers are all assembled after cutting and either bolted or bonded together. Direct Metal Laser Sintering (DMLS) Tooling The Direct Metal Laser Sintering (DMLS) technology was developed by EOS. The process uses a very high-powered laser to sinter metal powders directly. The powders available for use by this technology are the bronze-based and steel-based materials. Bronze is used for applications where strength requirements are not crucial. Upon sintering of the bronze powder, an organic resin, such as epoxy, is used to infiltrate the part. For steel powders, the process is capable of producing direct steel parts of up to 95% density so that further infiltration is not required. Several direct applications produced with this technology including mold inserts and other metal parts. ProMetal Rapid Tooling Based on MIT s Three Dimensional Printing (3DP) process, the ProMetalTM Rapid Tooling System is capable of creating steel parts for tooling of plastic injection molding parts, lost foam patterns and vacuum forming. This technology uses an electrostatic ink jet print head to eject liquid binders onto the powder, selectively hardening slices of an object a layer at a time. A fresh coat of metal powder is spread on top and the process repeats until the part is completed. The loose powder act as supports for the object to be bui lt. The RP part is then infiltrated at furnace temperatures with a secondary metal to achieve full density. Toolings produced by this technology for use in injection molding have reported withstanding pressures up to 30 000 psi (200 MPa) and surviving 100 000 shots of glass-filled nylon [19]. Copper Polyamide Tooling The Copper Polyamide tooling process from DTM (Austin, Texas) involves the selective laser sintering of a copper and polyamide powder matrix to form a tool. All of the sintering is between the polyamide powder particles. The process boasts an increase in tool toughness and heat transfer over some of the other soft tooling methods. These characteristics are provided by the copper and can give the user the benefits of running a tool with pressure and temperature settings that are closer to production settings. The primary disadvantage is the low material strength. Quick Cast Quick Cast, is a 3D Systems proprietary process, replaces traditional wax patterns for investment casting with stereolithography (SLA) patterns created in a robust, durable material, without tooling and without delay. The net result is Quick Cast patterns in as little as 2 to 4 days and quality metal castings in 1 to 4 weeks. The Quick Cast part resembles a beehive hatch pattern and ends up being about 80% hollow. It will burn out in the investment casting process with very little residue. PROCESS DESCRIPTION A Stereolithography Quick Cast pattern is created from an STL file. The pattern is leak tested to make sure it is air tight. An investment caster is chosen (based on experience & material required). Quick Cast pattern is given to the caste Caster puts part through ceramic coating process and performs firing procedure to burn out SLA pattern. Metal is poured into the fired ceramic shell. Ceramic shell is broken off to reveal metal part Soft Tooling is made out of Silicon Rubber Resin and due to its flexibility it is called Soft Tooling (also called Silicon Rubber Mould). Silicon Rubber Mould is used to pr oduce plastic prototype components (out of Polyurethane Resin) and in some cases wax patterns also for further Investment Casting. Hard Tooling Delivery of first article samples, 4 weeks (very simple parts) 12 weeks (normal complexity) longer for complex or parts requiring ceramic core tooling Delivery of production, 2 12 weeks after First Article approval. Highest tooling expense Lowest investment casting pattern cost Hard tooling will have the longest life. Simple tooling will last for hundreds of thousands of parts. Complex tooling with slides and cores will wear over time but can generally be refurbished. This is not normally necessary for many years. Yields the best surface finish and most consistent dimensional control. Soft Tooling Delivery of first article samples, 3 6 weeks Delivery of production, 2 12 weeks after First article approval Soft tooling is less costly than Hard Tooling Pattern cost is higher than Hard Tooling. This is because the tooling will cycle slower due to the poor thermal conductivity of mold material Life of soft tooling is limited. Life will depend upon the complexity of part. The more complex the shorter the life Surface finish and dimensional control is not as good as Hard Tooling A single SLA (stereolithography) or Objet pattern is generally used to make the tooling SELECTIVE LASER SINTERING (SLS) Advantages (1) Good part stability. Parts are created within a precise controlled environment. The process and materials provide for directly produced functional parts to be built. (2) Wide range of processing materials. A wide range of materials including nylon, polycarbonates, metals and ceramics are available, thus providing flexibility and a wide scope of functional applications. (3) No part supports required. The system does not require CAD developed support structures. This saves the time required for support structure building and removal. (4) Little post-processing required. The finishing of the part is reasonably fine and requires only minimal post-processing such as particle blasting and sanding. (5) No post-curing required. The completed laser sintered part is generally solid enough and does not require further curing. (6) Parts obtained are tough. (7) There is no wastage material. 5.1.2.3 Disadvantages (1) Large physical size of the unit. The system requires a relatively large space to house it. Apart from this, additional storage space is required to house the inert gas tanks used for each build. (2) High power consumption. The system requires high power consumption due to the high wattage of the laser required to sinter the powder particles together. (3) Poor surface finish. The as-produced parts tend to have poorer surface finish due to the relatively large particle sizes of the powders used. (4) Parts are porous in nature. (5) Parts are brittle. (6) Long-time are required to heat up the material chamber before building the parts and to cool down after the building is over. Process The SLS Process The SLS process creates three-dimensional objects, layer by layer, from CAD-data generated in a CAD software using powdered materials with heat generated by a CO2 laser within the system. CAD data files in the STL file format are first transferred to the system where they are sliced. From this point, the SLS process starts and operates as follows: A thin layer of heat-fusible powder is deposited onto the partbuilding chamber. The bottom-most cross-sectional slice of the CAD part under fabrication is selectively drawn (or scanned) on the layer of powder by a heat-generating CO2 laser. The interaction of the laser beam with the powder elevates the temperature to the point of melting, fusing the powder particles to form a solid mass. The intensity of the laser beam is modulated to melt the powder only in areas defined by the part s geometry. Surrounding powder remain a loose compact and serve as supports. When the cross-section is completely drawn, an additional layer of powder is deposited via a roller mechanism on top of the previously scanned layer. This prepares the next layer for scanning. Steps 2 and 3 are repeated, with each layer fusing to the layer below it. Successive layers of powder are deposited and the process is repeated until the part is completed. As SLS materials are in powdered form, the powder not melted or fused during processing serves as a customized, built-in support structure. There is no need to create support structures within the CAD design prior to or during processing and thus no support structure to remove when the part is completed. After the SLS process, the part is removed from the build chamber and the loose powder simply falls away. SLS parts may then require some post-processing or secondary finishing, such as sanding, lacquering and painting, depending upon the application of the prototype built. Principle The SLS process is based on the following two principles: (1) Parts are built by sintering when a CO2 laser beam hits a thin layer of powdered material. The interaction of the laser beam with the powder raises the temperature to the point of melting, resulting in particle bonding, fusing the particles to themselves and the previous layer to form a solid. (2) The building of the part is done layer by layer. Each layer of the building process contains the cross-sections of one or many parts. The next layer is then built directly on top of the sintered layer after an additional layer of powder is deposited via a roller mechanism on top of the previously formed layer. The packing density of particles during sintering affects the part density. In studies of particle packing with uniform sized particles [3] and particles used in commercial sinter bonding [4], packing densities were found to range typically from 50% to 62%. Generally, the higher the packing density, the better would be the expected mechanical properties. However, it must be noted that scan pattern and exposure parameters are also the major factors in determining the mechanical properties of the part. Applications The system can produce a wide range of parts in a broad variety of applications, including the following: (1) Concept models. Physical representations of designs used to review design ideas, form and style. (2) Functional models and working prototypes. Parts that can withstand limited functional testing, or fit and operate within an assembly. (3) Polycarbonate (RapidCastingTM) patterns. Patterns produced using polycarbonate, then cast in the metal of choice through the standard investment casting process. These build faster than wax patterns and are ideally suited for designs with thin walls and fine features. These patterns are also durable and heat resistant. (4) Metal tools (RapidToolTM). Direct rapid prototype of tools of molds for small or short production runs. Specifications 1. Laser type 2. Laser power 3. Spot size 4. Maximum scan speed 5. XY resolution 6. Work volume, XYZ 7. Minimum layer thickness 8. Size of unit 9. Layering time per layer 10. Power supply FUSED DEPOSITION MODELING (FDM) Process In this patented process [12], a geometric model of a conceptual design is created on a CAD software which uses IGES or STL formatted files. It can then imported into the workstation where it is processed through the QuickSlice and SupportWorkTM propriety software before loading to FDM 3000 or similar systems. For FDM Maxum and Titan, a newer software known as Insight is used. The basic function of Insight is similar to that of QuickSlice and the only difference is that Insight does not need another software to auto-generate the supports. The function is incorporated into the software itself. Within this software, the CAD file is sliced into horizontal layers after the part is oriented for the optimum build position, and any necessary support structures are automatically detected and generated. The slice thickness can be set manually to anywhere between 0.172 to 0.356 mm (0.005 to 0.014 in) depending on the needs of the models. Tool paths of the build process are then generated which are downloaded to the FDM machine. The modeling material is in spools very much like a fishing line. The filament on the spools is fed into an extrusion head and heated to a semi-liquid state. The semi-liquid material is extruded through the head and then deposited in ultra thin layers from the FDM head, one layer at a time. Since the air surrounding the head is maintained at a temperature below the materials melting point, the exiting material quickly solidifies. Moving on the X Y plane, the head follows the tool path generated by QuickSlice or Insight generating the desired layer. When the layer is completed, the head moves on to create the next layer. The horizontal width of the extruded material can vary between 0.250 to 0.965 mm depending on model. This feature, called road width , can vary from slice to slice. Two modeler materials are dispensed through a dual tip mechanism in the FDM machine. A primary modeler material is used to produce the model geometry and a secondary material, or release material, is used to produce the support structures. The release material forms a bond with the primary modeler material and can be washed away upon completion of the 3D models. Principle The principle of the FDM is based on surface chemistry, thermal energy, and layer manufacturing technology. The material in filament (spool) form is melted in a specially designed head, which extrudes on the model. As it is extruded, it is cooled and thus solidifies to form the model. The model is built layer by layer, like the other RP systems. Parameters which affect performance and functionalities of the system are material column strength, material flexural modulus, material viscosity, positioning accuracy, road widths, deposition speed, volumetric flow rate, tip diameter, envelope temperature, and part geometry. Advantages and Disadvantages The main advantages of using FDM technology are as follows: 1. Fabrication of functional parts. FDM process is able to fabricate prototypes with materials that are similar to that of the actual molded product. 2. Minimal wastage. The FDM process build parts directly by extruding semi-liquid melt onto the model. Thus only those materials needed to build the part and its support are needed, and material wastages are kept to a minimum. There is also little need for cleaning up the model after it has been built. 3. Ease of support removal. With the use of Break Away Support System (BASS) and Water Works Soluble Support System, support structures generated during the FDM building process can be easily broken off or simply washed away. This makes it very convenient for users to get to their prototypes very quickly and there is very little or no post-processing necessary. 4. Ease of material change. Build materials, supplied in spool form are easy to handle and can be changed readily when the materials in the system are running low. This keeps the operation of the machine simple and the maintenance relatively easy. 5. No post curing required. 6. The machines is less expensive. 7. Part building can be carried out unattended. 8. The material has a large self-life and remains unaffected if not removed from packing provided. The main disadvantages of using FDM technology are as follows: 1. Restricted accuracy. Parts built with the FDM process usually have restricted accuracy due to the shape of the material used, i.e., the filament form. Typically, the filament used has a diameter of 1.27 mm and this tends to set a limit on how accurately the part can be built. 2. Slow process. The building process is slow, as the whole cross-sectional area needs to be filled with building materials. Building speed is restricted by the extrusion rate or the flow rate of the build material from the extrusion head. As the build material used is plastic and their viscosities are relatively high, the build process cannot be easily speeded up. 3. Unpredictable shrinkage. As the FDM process extrudes the build material from its extrusion head and cools them rapidly on deposition, stresses induced by such rapid cooling invariably are introduced into the model. As such, shrinkages and distortions caused to the model built are a common occurrence and are usually difficult to predict. 4. The strength is low in the vertical direction 5. Surface finish are inferior to other processes. Applications FDM models can be used in the following general applications areas: 1. Models for conceptualization and presentation. Models can be marked, sanded, painted and drilled and thus can be finished to be almost like the actual product. 2. Prototypes for design, analysis and functional testing. The system can produce a fully functional prototype in ABS. The resulting ABS parts have 85% of the strength of the actual molded part. Thus actual testing can be carried out, especially with consumer products. 3. Patterns and masters for tooling. Models can be used as patterns for investment casting, sand casting and molding. Parameters 1. 2. 3. 4. 5. 6. 7. 8. 9. Build size Accuracy Layer road width Layer thickness Support structures Size Weight Power requirements Modelling materials

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