Biointegration is essential for the successful performance of implanted materials and devices within the human body. With an increasing number and wide range of implant procedures being performed, it is critical that materials scientists and engineers effectively design implant materials which will create a positive biological and mechanical response with.
This book covers in detail the various aspects of joining materials to form parts. A conceptual overview of rapid prototyping and layered manufacturing is given, beginning with the fundamentals so that readers can get up to speed quickly. Unusual and emerging applications such as micro-scale manufacturing, medical applications, aerospace, and. Additive manufacturing or 3D printing, manufacturing a product layer by layer, offers large design freedom and faster product development cycles, as well as low startup cost of production, on-demand production and local production.
In principle, any product could be made by additive manufacturing. Even food and living organic cells can. This book introduces the role of Rapid Prototyping Techniques within the product development phase. It deals with the concept, origin, and working cycle of Rapid Prototyping Processes with emphasis on the applications.
Apart from elaboration of engineering and non-engineering applications, it highlights recent applications like Bio-Medical Models for Surgical Planning,.
The model is built upon a platform in a vat of photo sensitive liquid. A focused UV laser traces out the first layer, solidifying the model cross section while leaving excess areas liquid. In the next step, an elevator lowers the platform into the liquid polymer by an amount equal to layer thickness. A sweeper recoats the solidified layer with liquid, and the laser traces the second layer on the first.
This process is repeated until the prototype is complete. Afterwards, the solid part is removed from the vat and rinsed clean of excess liquid. Supports are broken off and the model is then placed in an ultraviolet oven for complete curing. Software: i. It has got three packages. Build Materials Used: Epoxy Resin, Acrylate Resin Epoxy Resin has better material properties and less hazardous but require large exposure time for curing.
Stereolithography Apparatus Operation: 1 The process begins with the solid model in various CAD formats 2 The solid model must consist of enclosed volumes before it is translated form CAD format into. STL FILE one which supports in addition to original file are then sliced into horizontal cross sections and saved as slice file.
Vector file. The V file contains actual line data that the laser will follow to cure the shape of the part. The four build files are downloaded to SLA which begins building supports with platen adjust above the surface level.
The first few support layers are actually cured into perforations into platen, thus providing a solid anchor for the rest of the part. By building, SLA uses laser to scan the cross section and fill across the surface of resin which is cured or hardened into the cross sectional shape.
The platen is lowered as the slices are completed so that more resin is available in the upper surface of the part to be cured. Final step is Post Processing. Clean the part in the alcohol bath and then go for final curing. Post Curing. Applications: 1 Investment Casting. What is rapid prototyping?
What is rapid prototyping systems? Classify rapid prototyping systems. What is the need and importance of rapid prototyping? Write a note on history of RP systems. Explain the principles and applications of stereolithography systems. Write a note on stereolithography? Explain the principles, process parameters and process details of stereolithography.
What is the need for a prototype in new product development. What are the applications of rapidprototyping in the medical field? What are the recent trends in rapidprototyping? List the application areas of stereolithography process. What are the advantages and disadvantages of stereolithography process?
Selective Laser Sintering was developed by university of Texas Austin in The build media for Selective Laser Sintering comes in powder form which is fused together by a powerful carbon dioxide laser to form the final product. DTM sinter station is the machine used for the process. Selective Laser Sintering begins like most other rapid prototyping processes with a standard.
DTM view software uses the. STL files. This software do the required orientation and scaling of parts. This machine has auto nesting capabilities which will place multiple part optimally in the build chamber for best processing speed and results. Once the. STL file is placed and parameters are set the model is directly built from the file. The model is built layer by layer like other rapid prototyping process so that the build piston will begin at the top of its range and will lower in increments of the set layer size as parts are built.
With the build piston at the top a thin layer of powder is spread across the build area by the roller from one of the feed piston. The laser then cures in a raster sweeps motion across the area of the parts being built. The part piston lowers and more powder is deposited and the process is continued until all of the part is built. The build media is removed from the machine.
It is a cake of powder. This cake is taken to the breakout station where excess powder is removed from the part manually with brushesthe excess powder that has been removed can be kept for recycling and can be reused. Some material needs additional finishing. It can use wide variety of materials to accommodate multiple application throughout the manufacturing process Applications: 1.
As conceptual models. Functional prototypes. As Pattern masters. Advantages: 1. Wide range of build materials. High throughput capabilities. Self-supporting build envelop. Parts are completed faster. Damage is less. Less wastage of material Disadvantages: 1. Initial cost of system is high. High operational and maintenance cost. Peripheral and facility requirement. Fused Deposition Modelling relies on standard STL data file for input and is capable of using multiple build materials in a build or support relationship.
By feeding the head with a plastic wire, solid objects are built "string by string". In this technique, filaments of heated thermoplastic are extruded from a tip that moves in the x-y plane. Like a baker decorating a cake, the controlled extrusion head deposits very thin beads of material onto the build platform to form the first layer.
The platform is maintained at a lower temperature, so that the thermoplastic quickly hardens. After the platform lowers, the extrusion head deposits a second layer upon the first. Supports are built along the way, fastened to the part either with a second, weaker material or with a perforated junction. Build Materials: 1 Investment Casting Wax.
Dry Blocks: a These are raw material feeding mechanisms and are mounted on back of head. To serve as a melting area for the material b The heating element is electronically controlled and has feedback thermocouple to allow for a stable temperature throughout.
This allows for smooth extrusion as well as time control on material placement. Tip: a The two tips are externally threaded and screwed up into the heating chamber exit and are used to reduce the extruded filament diameter to allow for better detailed modelling b. The tips are heated by heating chamber up to above the melting point of the material. Build Substrate: 1 The foam substrate is an expendable work table once which parts are built.
As for the first few layers of the part, the hot extrusion orifices are touching the substrate. Quick Slice software is used for this purpose. Part Size: The part must fit into the building box, if not it will either have to be scaled down to fit or be sectioned so that the pieces can be built separately and then bonded together later. Orientation and Positioning: Once the part has been built in appropriate built size, the part should be oriented in an optimum position for building.
The shape of the part plays an important role in this, in that some orientations may require less supporting of overhangs than the others.
Slicing: Once the part has been properly oriented and or scaled it must be sliced. Slicing is a software operation that creates thin horizontal cross sections of STL file that will later be used to create control code for the machine.
In Quick Slice, the slice thickness can be changed before slicing, the typical slices ranging from 0. Also editing function allows repair of minor flaws in the STL file with the options of closing and merging of curves. Build Parameters: A. Sets: Quick Slice uses sets or packages of build parameters. Sets contain all of the build instructions for a selected set of curves in a part.
Sets allow a part to be built with several different settings E. One set may be used for supporting structure of the part, one for part face, another for thicker sections of the part and still another for exposed surfaces of the part. This allows flexibility of building bulkier sections and internal fills quickly by getting finer details on visible areas of a part. Sets also allow chosen sections of a part to build hollow, cross hatched or solid if so desired.
Two of the build parameters commonly worked with are road width and fill spacing. Road Width: Road Width is the width of the ribbon of molten material that is extruded from the tip. When FDM builds a layer, it usually begins by outlining the cross section with a perimeter road, sometimes followed by one or more concentric contours inside of perimeters.
Next it begins to fill remaining internal area in a raster or hatched pattern until a complete solid layer is finished.
A fill spacing set at zero means that part will be built solid. Creating and Outputting Roads: Once all parameters have been set, road are created graphically by Quick Slice.
The user is then allowed to preview each slice if so desired to see if the part is going to build as required. Basically it displays in the command windows, the approximate amount of time and material to be used for given part. Build time estimate allows for a efficient tracking and scheduling of FDM system work loads.
Building a part: The FDM receives a SML file and will begin by moving the head to the extreme X and Y portions to find it and then raises the platen to a point to where the foam substrate is just below heated tips. After checking the raw material supply and temperature settings, the user then manually places the head at point where the part has to be built on the foam and then presses a button to begin building.
After that FDM will build part completely without any user intervention. Applications: a. Concept or Design Visualization. Direct Use Components. Investment Casting. Medical Applications e. Flexible Components. Conceptual modeling. Fit, form and functional applications and models for further manufacturing procedures. Investment casting and injection molding. Advantages: a. Strength and temperature capability of build materials.
Safe laser free operation. Easy Post Processing. Quick and cheap generation of models. Easy and convenient date building. No worry of possible exposure to toxic chemicals, lasers, or a liquid polymer bath. No wastage of material during or after producing the model. No requirement of clean-up. Quick change of materials. Process is slower than laser based systems. Build Speed is low.
Thin vertical column prove difficult to build with FDM. Physical contact with extrusion can sometimes topple or at least shift thin vertical columns and walls. Restricted accuracy due to the shape of the material used: wire of 1. What is selective laser sintering? Explain briefly selective laser sintering. What are the advantages and disadvantages of selective laser sintering. Explain the principles, process parameters, and process details of selective laser sintering.
What is the power source heat source used to heat-up the material? Explain data preparation for selective laser sintering. List the application areas of selective laser sintering. What is fusion deposition modelling? Explain briefly fusion deposition modelling. What are the advantages and disadvantages of fusion deposition modelling.
Explain the principle, process parameter, process details of fusion deposition modelling. List the application areas of fusion deposition modelling. What is the heat source used in fusion deposition modelling? Size was made more manageable and the system sealed to prevent exposure to photopolymers, but it was still very large. Instead of using a laser to expose and harden photopolymer element by element within a layer as is done in stereo lithography, SGC uses a mask to expose the entire object layer at once with a burst of intense UV light.
The method of generating the masks is based on electrophotography xerography. Highlights 1. Large parts of xxmm can be fabricated quickly. High speed allows production of many parts.
Masks are created. No post curing required 5. Milling step ensures flatness of subsequent layers. Wax supports model, hence no extra support is required. Create a lot of wastes. Spray photosensitive resin:At the beginning of a layer creation step the flat work surface is sprayed with photosensitive resin. Development of photo maskFor each layer a photo mask is produced using cubitals proprietary ionographic printing technique. Expose photo maskThe photo mask is positioned over the work surface a powerful UV lamp hardens the exposed photosensitive resin.
Vacuum uncured resin and solidify the remnants After the layer is cured all the uncured resin is vacuumed for recycling leaving the hardened area intact the cured layer is passed beneath a strong linear UV lamp to fullycure in and solidify any remnants particles as shown in figure. Wax is applied to replace uncured resin areaWax replaces the cavities left by vacuuming the liquid resin. The wax is hardened by cooling to provide continuous solid support for the model as it is fabricated extra supports are not needed.
The top surface is milled flatIn the final step before the next layer, the wax resin surface is milled flat to an accurate reliable finish for next layer. Advantages The entire layer is solidified at once. Reduction in the part build time for multipart builds. Larger prototypes can be nested to utilize the build volume fully. No post curing is required.
Disadvantages The system is large, noisy and heavy. It wastes a large amount of wax which cannot be recycled. SGC systems are prone to breakdowns. The resin models of SGC are not suitable for investment casting because coefficient of thermal expansion is more than ceramics in resin which may lead to cracks in casting. LOM is actually more of a hybrid between subtractive and additive process.
In that models are built up with layers of cross section of the part. Hence as layers are been added, the excess material is not required for that cross section is being cut away. LOM is one of the fastest RP processes for parts with longer cross sectional areas which make it ideal for producing large parts. System Hardware: 1 LOM system is available in two sizes.
LOM produces parts up to 10x15x14 inches. LOM produces parts upto20x30x24 inches. The process of continuous slicing is called slice on the fly. The feed spindle holds the roll of virgin material whereas the take up spindle serves to store the excess material after the layer is cut.
A heated roller travels across the face of the part being built after each layer to activate adhesive and bond the part layer together. An invisible 25Watts CO2 laser is housed on the back of the LOM and reflected off three mirrors before finally passing through a focusing lens on the carriage.
The carriage moves in the X direction and the lens moves in the Y direction on the carriage, thus allowing focal cutting point of laser to be moved like a plotter pen while cutting through build material in the shape desired. This X and Y movement allows for two degrees of freedom or essentially a 2-D sketch of part cross section.
The part being built is adhered to a removable metal plate which holds the part stationary until it is completed. The plate is bolted to the platen with brackets and moves in the Z direction by means of a large threaded shaft to allow the parts to be built up. This provides the third degree of freedom where in the LOM is able to build 3D models. Some smoke and other vapors are created since the LOM functions by essentially burning through the sheets of material with a laser, therefore LOM must be ventilated either to the outside air or through a large filtering device at rates around cubic feet per minute.
The following description of operation is described with paper as build material. Now there are several parameters the user must consider and enter before building the part. Part Orientation: The designed shape of the parts to be built in LOM must be evaluated for determining the orientation in which to build the parts. First Consideration: Accuracy desired for curved surfaces:Parts with curved surfaces tend to have a better finish if the curvatures of the cross sections are cut in the XY plane.
This is true due to the fact that the controlled motion of the laser cutting in the XY plane can hold better curve tolerances dimensionally than the layered effects of XZ and YZ planes.
If a part contains curvatures in more than one plane, one alternative is to build the part at an angle to the axis. The benefits here are too full as the part will not only have more accurate curvatures but will also tend to have better laminar strength across the length of the part. Second Consideration: Time taken to fabricate a part: The slowest aspect of build process for LOM is movement in Z direction or time between the layers.
This is mainly because after laser cuts across the surface of the beam material, the LOM must bring more paper across the top face of the part and then adhere to the previous layer before the laser can begin cutting again. For this reason a general rule have come for orienting long narrow parts is to place the lengthiest sections in the XY plane.
There are some third party software renders that have automatic testing functions that will strategically place parts in optimum orientations for the selected section. Cross Hatching: Cross Hatching is necessary to get rid of excess paper on the individual layers. Basically the operator puts in a range of layers for which we want a certain cross hatch pattern for sections of the part that do not have integrate features or cavities, a larger cross hatch can be set to make a part build faster but for thin walled sections and hollowed out areas, a finer cross hatch will be easier to remove.
The cross hatch size is given in values of X and Y. Therefore the hatch pattern can vary from square to long thin rectangles. A very small hatch sizes will make for easy part removal. However if the part is rather large or has large void areas it can really slow down the build time. This is the reason for having varying cross hatch sizes throughout the part. The LOM operator can either judge where and how the part should be cross hatched visually or use long slice to run a simulation build on the computer screen to determine layer ranges for the needed hatch sizes.
Laser Power: It is the percentage of total laser output wattage. For e. This value will be different for various materials or machines but essentially it is set to cut through only one sheet of build material.
Heater Speed: It is the rate at which hot roller passes across the top of the part. The heater speed effects the lamination of the sheet so it must be set low enough to get a good bond between layers.
Material Advance Margin: It is the distance the paper is advanced in addition to length of the part. Support Wall Thickness: It controls the outer support box walls throughout a part. The support wall thickness is generally set 0.
Compression: It is used to set the pressure that the heater roller exerts on the layer. It is measured in inches which are basically the distance the roller is lifted from its initial track by the top surface of part. Values for compression will vary for different machines and materials, but are typically 0.
What is solid ground curing? Explain briefly solid ground curing. What are the steps involved in producing a part by solid base curing? What are the advantages and disadvantages of solid ground curing? Explain the principles and machine details of solid ground curing? List the applications of the solid ground curing. What is laminated object manufacturing? Explain briefly laminated object manufacturing. Explain the principles and machine details of laminated object manufacturing.
What are the advantages and disadvantages of laminated object manufacturing? What is the heat source employed in laminated object manufacturing.
List the applications of laminated object manufacturing. What is the material used to form a prototype in LOM process? In what form the material is fed into the system? The systems are usually small, inexpensive, quiet, and require very little or no training to operate.
For these reasons, the systems are targeted to reside in design office environments, where they can ideally be operated much like a standard printer, only the prints from these systems are in three dimensions. Thermal Ink jet Printer Ink jet printing comes from the printer and plotter industry where the technique involves shooting tiny droplets of ink on paper to produce graphic images. RP ink jet techniques utilize ink jet technology to shoot droplets of liquid-to-solid compound and form a layer of an RP model.
The additive fabrication technique of inkjet printing is based on the 2D printer technique of using a jet to deposit tiny drops of ink onto paper. In the additive process, the ink is replaced with thermoplastic and wax materials, which are held in a melted state.
When printed, liquid drops of these materials instantly cool and solidify to form a layer of the part. For this reason, the process if often referred to as thermal phase change inkjet printing. Inkjet printing offers the advantages of excellent accuracy and surface finishes. However, the limitations include slow build speeds, few material options, and fragile parts.
As a result, the most common application of inkjet printing is prototypes used for form and fit testing. Other applications include jewellery, medical devices, and high-precisions products. Several manufactures have developed different inkjet printing devices that use the basic technique described above. Inkjet printers from Solidscape Inc. The inkjet printing process, as implemented by Solidscape Inc. These materials are each fed to an inkjet print head which moves in the X-Y plane and shoots tiny droplets to the required locations to form one layer of the part.
In fact, there are no real restrictions when working with complex designs. By using rapid prototyping services , product designers and engineers have the ability to produce detailed 3-D models very quickly to any design they can dream up, and with the latest technology, very good accuracy. For all prototype companies, speed and accuracy are very critical. Depending on the finished part, component, or model required by the customer, prototyping companies use a variety of materials.
For example, in the metal cast area, 3-D prototypes can be constructed from a special prototyping wax. Various methods of prototype casting are used with these patterns. Vacuum plaster and low-temperature furnace methods are commonly paired with prototyping wax patterns in the prototype metal field. Rapid prototyping services also fabricate many parts in plastics. This is especially valuable because of the great prevalence of thermoplastic materials in product design now days; used in everything from automobiles to all sorts of industrial, medical, and consumer products.
The reason is that thermoplastic components can be designed to complex shapes, molded in color, and often are capable of resisting both heat and chemicals. In many cases these must be durable parts that require extensive functional testing.
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