opensource3d printers

3d printing technology

2011-12-08T19:06:00.001+05:30

Here I presented the traditional methods involved for 3d printing such as stereolithography method, Fused deposition modeling, Selective laser sintering, direct laser sintering, 3 dimensional printing, Inkjet printing, jetted photopolymer method and laminated object manafacturing

After finishing this we will go to to the open source reprap projects and there i will tell u how i am going to construct the reprap pursa menndel

Stereolithography (SLA)

Stereolithography (SLA) is the most widely used rapid prototyping technology. It can produce highly accurate and detailed polymer parts. It was the first rapid prototyping process, introduced in 1988 by 3D Systems, Inc., based on work by inventor Charles Hull. It uses a low-power, highly focused UV laser to trace out successive cross-sections of a three-dimensional object in a vat of liquid photosensitive polymer. As the laser traces the layer, the polymer solidifies and the excess areas are left as liquid. When a layer is completed, a leveling blade is moved across the surface to smooth it before depositing the next layer. The platform is lowered by a distance equal to the layer thickness (typically 0.003-0.002 in), and a subsequent layer is formed on top of the previously completed layers. This process of tracing and smoothing is repeated until the build is complete. Once complete, the part is elevated above the vat and drained. Excess polymer is swabbed or rinsed away from the surfaces. In many cases, a final cure is given by placing the part in a UV oven. After the final cure, supports are cut off the part and surfaces are polished, sanded or otherwise finished.

Fused Deposition Modeling (FDM)

Fused Deposition Modeling (FDM) was developed by Stratasys in Eden Prairie, Minnesota. In this process, a plastic or wax material is extruded through a nozzle that traces the part's cross sectional geometry layer by layer. The build material is usually supplied in filament form, but some setups utilize plastic pellets fed from a hopper instead. The nozzle contains resistive heaters that keep the plastic at a temperature just above its melting point so that it flows easily through the nozzle and forms the layer. The plastic hardens immediately after flowing from the nozzle and bonds to the layer below. Once a layer is built, the platform lowers, and the extrusion nozzle deposits another layer. The layer thickness and vertical dimensional accuracy is determined by the extruder die diameter, which ranges from 0.013 to 0.005 inches. In the X-Y plane, 0.001 inch resolution is achievable. A range of materials are available including ABS, polyamide, polycarbonate, polyethylene, polypropylene, and investment casting wax.

Selective Laser Sintering (SLS)

Selective Laser Sintering (SLS) was developed at the University of Texas in Austin, by Carl Deckard and colleagues. The technology was patented in 1989 and was originally sold by DTM Corporation. DTM was acquired by 3D Systems in 2001. The basic concept of SLS is similar to that of SLA. It uses a moving laser beam to trace and selectively sinter powdered polymer and/or metal composite materials into successive cross-sections of a three-dimensional part. As in all rapid prototyping processes, the parts are built upon a platform that adjusts in height equal to the thickness of the layer being built. Additional powder is deposited on top of each solidified layer and sintered. This powder is rolled onto the platform from a bin before building the layer. The powder is maintained at an elevated temperature so that it fuses easily upon exposure to the laser. Unlike SLA, special support structures are not required because the excess powder in each layer acts as a support to the part being built. With the metal composite material, the SLS process solidifies a polymer binder material around steel powder (100 micron diameter) one slice at a time, forming the part. The part is then placed in a furnace, at temperatures in excess of 900 °C, where the polymer binder is burned off and the part is infiltrated with bronze to improve its density. The burn-off and infiltration procedures typically take about one day, after which secondary machining and finishing is performed. Recent improvements in accuracy and resolution, and reduction in stair-stepping, have minimized the need for secondary machining and finishing. SLS allows for a wide range of materials, including nylon, glass-filled nylon, SOMOS (rubber-like), Truform (investment casting), and the previously discussed metal composite.

Direct Metal Laser Sintering (DMLS)

Direct Metal Laser Sintering (DMLS) was developed jointly by Rapid Product Innovations (RPI) and EOS GmbH, starting in 1994, as the first commercial rapid prototyping method to produce metal parts in a single process. With DMLS, metal powder (20 micron diameter), free of binder or fluxing agent, is completely melted by the scanning of a high power laser beam to build the part with properties of the original material. Eliminating the polymer binder avoids the burn-off and infiltration steps, and produces a 95% dense steel part compared to roughly 70% density with Selective Laser Sintering (SLS). An additional benefit of the DMLS process compared to SLS is higher detail resolution due to the use of thinner layers, enabled by a smaller powder diameter. This capability allows for more intricate part shapes. Material options that are currently offered include alloy steel, stainless steel, tool steel, aluminum, bronze, cobalt-chrome, and titanium. In addition to functional prototypes, DMLS is often used to produce rapid tooling, medical implants, and aerospace parts for high heat applications.

The DMLS process can be performed by two different methods, powder deposition and powder bed, which differ in the way each layer of powder is applied. In the powder deposition method, the metal powder is contained in a hopper that melts the powder and deposits a thin layer onto the build platform. In the powder bed method (shown below), the powder dispenser piston raises the powder supply and then a recoater arm distributes a layer of powder onto the powder bed. A laser then sinters the layer of powder metal. In both methods, after a layer is built the build piston lowers the build platform and the next layer of powder is applied. The powder deposition method offers the advantage of using more than one material, each in its own hopper. The powder bed method is limited to only one material but offers faster build speeds.

Three Dimensional Printing (3DP)

Three Dimensional Printing (3DP) technology was developed at the Massachusetts Institute of Technology and licensed to several corporations. The process is similar to the Selective Laser Sintering (SLS) process, but instead of using a laser to sinter the material, an ink-jet printing head deposits a liquid adhesive that binds the material. Material options, which include metal or ceramic powders, are somewhat limited but are inexpensive relative to other additive processes. 3D Printing offers the advantage of fast build speeds, typically 2-4 layers per minute. However, the accuracy, surface finish, and part strength are not quite as good as some other additive processes. 3D Printing is typically used for the rapid prototyping of conceptual models (limited functional testing is possible).

The 3D printing process begins with the powder supply being raised by a piston and a leveling roller distributing a thin layer of powder to the top of the build chamber. A multi-channel ink-jet print head then deposits a liquid adhesive to targeted regions of the powder bed. These regions of powder are bonded together by the adhesive and form one layer of the part. The remaining free standing powder supports the part during the build. After a layer is built, the build platform is lowered and a new layer of powder added, leveled, and the printing repeated. After the part is completed, the loose supporting powder can be brushed away and the part removed. 3D printed parts are typically infiltrated with a sealant to improve strength and surface finish.

Inkjet printing

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 jewelry, 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., such as the ModelMaker (MM), use a single jet for the build material and another jet for support material. 3D Systems has implemented their MultiJet Moldeling (MJM) technology into their ThermoJet Modeler machines that utilize several hundred nozzles to enable faster build times.

The inkjet printing process, as implemented by Solidscape Inc., begins with the build material (thermoplastic) and support material (wax) being held in a melted state inside two heated reservoirs. 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. Both the build material and support material instantly cool and solidify. After a layer has been completed, a milling head moves across the layer to smooth the surface. The particles resulting from this cutting operation are vacuumed away by the particle collector. The elevator then lowers the build platform and part so that the next layer can be built. After this process is repeated for each layer and the part is complete, the part can be removed and the wax support material can be melted away.

Jetted photopolymer

Jetted photopolymer is an additive process that combines the techniques used in Inkjet Printing and Stereolithography. The method of building each layer is similar to Inkjet Printing, in that it uses an array of inkjet print heads to deposit tiny drops of build material and support material to form each layer of a part. However, as in Stereolithography, the build material is a liquid acrylate-based photopolymer that is cured by a UV lamp after each layer is deposited. For this reason, Jetted Photopolymer is sometimes referred to as Photopolymer Inkjet Printing. The advantages of this process are very good accuracy and surface finishes. However, the feature detail and material properties are not quite as good as Stereolithography. As with Inkjet Printing, the most common application of this technology is prototypes used for form and fit testing. Other applications include rapid tooling patterns, jewelry, and medical devices.

Two companies that have developed jetted photopolymer devices include Objet Geometries Ltd. and 3D Systems. The equipment designed by both companies deposits the photopolymer build material as described above, but differs in the application of support material. Objet, an Israeli company, commercialized their PolyJet technology in 2000. In the PolyJet system, the support material is also a photopolymer that is deposited from a second print head and cured by the UV lamp. This support material does not cure the same as the build material and can later be washed away with pressurized water. 3D systems commercialized their InVision systems in 2003. These jetted photopolymer devices use a separate print head to deposit a wax support material. After the part is completed, the wax is melted away.

Laminated Object Manufacturing (LOM)

The first commercial Laminated Object Manufacturing (LOM) system was shipped in 1991. LOM was developed by Helisys of Torrance, CA. The main components of the system are a feed mechanism that advances a sheet over a build platform, a heated roller to apply pressure to bond the sheet to the layer below, and a laser to cut the outline of the part in each sheet layer. Parts are produced by stacking, bonding, and cutting layers of adhesive-coated sheet material on top of the previous one. A laser cuts the outline of the part into each layer. After each cut is completed, the platform lowers by a depth equal to the sheet thickness (typically 0.002-0.020 in), and another sheet is advanced on top of the previously deposited layers. The platform then rises slightly and the heated roller applies pressure to bond the new layer. The laser cuts the outline and the process is repeated until the part is completed. After a layer is cut, the extra material remains in place to support the part during build.

All the images courtesy by :http://www.custompartnet.com/

Additive manafacturing (Rapid prototyping)

2011-12-02T18:47:00.001+05:30

Additive Manafacturing:

Additive fabrication refers to a class of manufacturing processes, in which a part is built by adding layers of material upon one another. These processes are inherently different from subtractive processes or consolidation processes. Subtractive processes, such as milling, turning, or drilling, use carefully planned tool movements to cut away material from a workpiece to form the desired part. Consolidation processes, such as casting or molding, use custom designed tooling to solidify material into the desired shape. Additive processes, on the other hand, do not require custom tooling or planned tool movements. Instead, the part is constructed directly from a digital 3-D model created through Computer Aided Design (CAD) software. The 3-D CAD model is converted into many thin layers and the manufacturing equipment uses this geometric data to build each layer sequentially until the part is completed. Due to this approach, additive fabrication is often referred to as layered manufacturing, direct digital manufacturing, or solid freeform fabrication.

The most common term for additive fabrication is rapid prototyping. The term "rapid" is used because additive processes are performed much faster than conventional manufacturing processes. The fabrication of a single part may only take a couple hours, or can take a few days depending on the part size and the process. However, processes that require custom tooling, such as a mold, to be designed and built may require several weeks. Subtractive processes, such as machining, can offer more comparable production times, but those times can increase substantially for highly complex parts. The term "prototyping" is used because these additive processes were initially used solely to fabricate prototypes. However, with the improvement of additive technologies, these processes are becoming increasingly capable of high-volume production manufacturing, as will be explored in the section on applications.

Additive fabrication offers several advantages, listed below.

Speed - As described above, these "rapid" processes have short build times. Also, because no custom tooling must be developed, the lead time in receiving parts is greatly reduced.
Part complexity - Because no tooling is required, complex surfaces and internal features can be created directly when building the part. Also, the complexity of a part has little effect on build times, as opposed to other manufacturing processes. In molding and casting processes, part complexity may not affect the cycle times, but can require several weeks to be spent on creating the mold. In machining, complex features directly affect the cycle time and may even require more expensive equipment or fixtures.
Material types - Additive fabrication processes are able to produce parts in plastics, metals, ceramics, composites, and even paper with properties similar to wood. Furthermore, some processes can build parts from multiple materials and distribute the material based on the location in the part.
Low-volume production - Other more conventional processes are not very cost effective for low-volume productions because of high initial costs due to custom tooling and lengthy setup times. Additive fabrication requires minimal setup and builds a part directly from the CAD model, allowing for low per-part costs for low-volume productions.

With all of these advantages, additive fabrication will still not replace more conventional manufacturing processes for every application. Processes such as machining, molding, and casting are still preferred in specific instances, such as the following:

Large parts - Additive processes are best suited for relatively small parts because build times are largely dependent upon part size. A larger part in the X-Y plane will require more time to build each layer and a taller part (in the Z direction) will require more layers to be built. This limitation on part size is not shared by some of the more common manufacturing methods. The cycle times in molding and casting processes are typically controlled by the part thickness, and machining times are dependent upon the material and part complexity. Manufacturing large parts with additive processes is also not ideal due to the current high prices of material for these processes.
High accuracy and surface finish - Currently, additive fabrication processes can not match the precision and finishes offered by machining. As a result, parts produced through additive fabrication may require secondary operations depending on their intended use.
High-volume production - While the production capabilities of additive processes are improving with technology, molding and casting are still preferred for high-volume production. At very large quantities, the per-part cost of tooling is insignificant and the cycle times remain shorter than those for additive fabrication.
Material properties - While additive fabrication can utilize various material types, individual material options are somewhat limited. As a result, materials that offer certain desirable properties may not be available. Also, due to the fabrication methods, the properties of the final part may not meet certain design requirements. Lastly, the current prices for materials used in additive processes are far greater than more commonly used materials for other processes.

Process

Several different additive fabrication processes are commercially available or are currently being developed. Each process may use different materials and different techniques for building the layers of a part. However, each process employs the same basic steps, listed below.

Create CAD model - For all additive processes, the designer must first use Computer-Aided Design (CAD) software to create a 3-D model of the part.
Convert CAD model into STL model - Each form of CAD software saves the geometric data representing the 3-D model in different ways. However, the STL format (initially developed for Stereolithography) has become the standard file format for additive processes. Therefore, CAD files must be converted to this file format. The STL format represents the surfaces of the 3-D model as a set of triangles, storing the coordinates for the vertices and normal directions for each triangle.
Slice STL model into layers - Using specialized software, the user prepares the STL file to be built, first designating the location and orientation of the part in the machine. Part orientation impacts several parameters, including build time, part strength, and accuracy. The software then slices the STL model into very thin layers along the X-Y plane. Each layer will be built upon the previous layer, moving upward in the Z direction.
Build part one layer at a time - The machine builds the part from the STL model by sequentially forming layers of material on top of previously formed layers. The technique used to build each layer differs greatly amongst the additive process, as does the material being used. Additive processes can use paper, polymers, powdered metals, or metal composites, depending upon the process.
Post-processing of part - After being built, the part and any supports are removed from the machine. If the part was fabricated from a photosensitive material, it must be cured to attain full strength. Minor cleaning and surface finishing, such as sanding, coating, or painting, can be performed to improve the part's appearance and durability.

Applications:

Additive fabrication processes initially yielded parts with few applications due to limited material options and mechanical properties. However, improvements to the processing technologies and material options have expanded the possibilities for these layered parts. Now, additive fabrication is used in a variety of industries, including the aerospace, architectural, automotive, consumer product, medical product, and military industries. The application of parts in these industries is quite vast. For example, some parts are merely aesthetic such as jewelry, sculptures, or 3D architectural models. Others are customized to meet the user's personal needs such as specially fitted sports equipment, dental implants, or prosthetic devices. The following three categories are often used to describe the different application of additive fabrication and may be applied to all of the above industries.

Rapid prototyping - Prototypes for visualization, form/fit testing, and functional testing
Rapid tooling - Molds and dies fabricated using additive processes
Rapid manufacturing - Medium-to-high volume production runs of end-use parts

Rapid prototyping

Additive processes are primarily used for the fabrication of prototypes. Initially, this was because the production of end-use products demanded better mechanical properties and lower costs. While these layered parts now offer higher quality and lower costs, other reasons still exist for using additive processes for the fabrication of prototypes. Firstly, prototypes are needed during the design stage and must be produced quickly. Additive processes have short build times and do not require any custom tooling to be created. Secondly, additive fabrication is more cost effective for low quantities than other processes. Again, this is primarily because no costly tooling is required.

The prototypes created through additive fabrication can serve many purposes. The prototype may simply be used for form testing, which is visually assessing the 3D form and design of the part and being able to communicate redesign or manufacturing requirements to other engineers. Prototypes are also frequently used for fit testing, in which the part's compatibility with other components of an assembly can be evaluated. In such form and fit applications, the material and mechanical properties are usually of little concern. Some additive processes produce prototypes used for functional testing, in which the part is tested under the operating conditions of the final product. For this application, the material and mechanical properties are significant and therefore only some additive fabrication processes are used towards this end.

By using additive fabrication to produce prototypes, much time and money can be saved in the product design process. The quick fabrication of a prototype means that more designs can be considered and tested in a shorter period of time. Also, potential manufacturing problems that are caused by the part design can be identified before full production begins. Not only does the design process move quicker, but the quality of the design is likely to improve as well.

Rapid tooling

Mold and dies, the custom tooling for molding and casting processes, are geometrically complex parts that require high accuracy, low surface roughness, and strong mechanical properties. Machining these tools using CNC milling or EDM can be the most time consuming and costly step in the molding or casting process. As a result, using additive fabrication to create the tooling offers a fast and cheap alternative known as rapid tooling. As previously explained, additive fabrication excels at producing highly complex parts without great impact on build time. Also, the highly skilled and expensive labor required to machine a mold is not required. As a result, rapid tooling can enable high-volume production of quality parts without the large initial cost and lead time for the tooling. Rapid tooling also offers the potential for many improvements to the mold design, including complex cooling channels that are more efficient, the use of multiple materials, and functionally grading materials to optimize performance.

Some limitations still exist in using rapid tooling. First, additive fabrication does not offer the high accuracy or finishes of machining, so secondary operations are typically required. Also, unlike additive fabrication, machining is able to use hard materials that offer great durability. As a result, rapid tooling is typically only used for low-to-medium volume productions. Lastly, as explained earlier, additive fabrication processes have smaller part size limitations and are unable to produce very large tooling.

The most common method of rapid tooling uses additive processes to fabricate the tooling indirectly by first creating a pattern. This pattern is then used to form the mold or die. Patterns are already used in manufacturing processes that use non-permanent molds, such as sand casting and investment casting. In these processes, a pattern is traditionally machined from wood, plastic, or soft metal and used to form the mold. Additive fabrication offers a fast alternative for creating these patterns, which can be re-used many times and offer similar properties to wood or plastic patterns.

Indirect tooling from additive fabrication can also be used to form re-usable molds for processes like vacuum casting or injection molding. Vacuum casting can use molds formed by pouring silicon rubber or room temperature vulcanizing (RTV) rubber around the rapid tooling pattern and allowing it to harden into the shape of the mold. These rubber molds can be used to form up to 50 plastic parts out of various polymers. Rapid tooling patterns can also be used to form metal/ceramic composite molds for injection molding which can produce up to 1,000 plastic parts.

Another type of rapid tooling is direct tooling, which is the use of additive fabrication to directly produce the mold without the need for a pattern. This approach was initially not viable because of the high accuracy and durability required for molds. However, with improvements in additive technologies and materials, direct rapid tooling is now possible. For example, Selective Laser Sintering and Electron Beam Melting have been used to directly fabricate metal molds, capable of producing hundreds of thousands of parts. However, secondary operations are still typically required to improve the finishes and tolerances of the mold.

Rapid manufacturing

Rapid manufacturing, a relatively new application for additive fabrication, is the medium-to-high volume production of end-use products using additive technologies. Initially, these processes weren't considered for large scale production due to limitations in the mechanical properties and surface finishes that they could attain. However, with improvements to additive technologies and materials, most additive processes are capable of, or being considered for, producing end-use products out of plastics, metals, composites, and ceramics.

Rapid manufacturing does have its limitations and is best suited for parts that take advantage of the additive process. As explained earlier, additive technologies excel at producing highly complex geometries, relatively small parts, using multiple materials, and functionally grading materials to improve performance. For parts that are very large, geometrically simple, or require high tolerances and surface finishes, other more conventional processes are still preferred.

Assuming that the desired part quality can be achieved, rapid manufacturing can offer many cost benefits over conventional manufacturing. Firstly, additive fabrication does not require any tooling which can be very costly and time consuming to produce for molding and casting processes. Also, additive processes typically have lower labor costs than conventional processes. This is due to the fact that parts are built directly from the CAD model and the process is highly automated. The labor costs are mainly attributed to the setup process, which becomes less significant with higher volume productions.

Despite the above advantages, at a certain production volume conventional processes remain the more cost effective choice. This cut-off for rapid manufacturing exists for several reasons. First, the cost benefit of not incurring tooling costs becomes less significant at high production volumes. When manufacturing hundreds of thousands of parts, the per-part cost of tooling becomes less of an issue. Next, the material cost for rapid manufacturing can be quite high because additive processes use less widely available materials. However, as rapid manufacturing becomes more commonplace, these material prices will drop. Lastly, part build times can not compete with the short cycle times of molding and casting processes, which are of great advantage at large production volumes. As additive technologies improve, rapid manufacturing will become more viable for large scale productions. A short time ago, additive manufacturing processes were only cost effective for production volumes of 100-500 parts. Now, production volumes of 10,000-15,000 parts are being seen.

3d printing

2011-12-01T14:30:00.001+05:30

“	Three-dimensional printing makes it as cheap to create single items as it is to produce thousands and thus undermines economies of scale. It may have as profound an impact on the world as the coming of the factory did....Just as nobody could have predicted the impact of the steam engine in 1750—or the printing press in 1450, or the transistor in 1950—it is impossible to foresee the long-term impact of 3D printing. But the technology is coming, and it is likely to disrupt every field it touches.	”
—The Economist, in a February 10, 2011 leader Hi friends ! I am arun and I am going to explain all about the fast growing technology which going to make our life in to very comfortable thing.This is going to happen with new 3d printers. So what is 3d printer? The answer is simple. Printer which has ability to print the 3d model in a plastic/solid form where u can touch , feel the model in real time within a short period of duration Me and my friends are here to work out the technology for the Indian Market. Please share us your knowledge and it will help us to create a better technology in future.