3D PRINTING - LIQUID AND SOLID BASED ADDITIVE MANUFACTURING
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This document provides information on liquid-based and solid-based additive manufacturing systems. It discusses stereolithography (SLA) and fused deposition modeling (FDM) in detail. SLA uses a laser to cure liquid resin layer-by-layer, and was the first commercialized AM process. FDM extrudes melted thermoplastics through a nozzle to build parts layer-by-layer. Both techniques can create prototypes, models, and some end-use parts, with SLA providing better accuracy and surface finish.
3D PRINTING - LIQUID AND SOLID BASED ADDITIVE MANUFACTURING
- 1. UNIT 3 LIQUID BASED AND SOLID BASED ADDITIVE MANUFACTURING SYSTEMS
- 2. CLASSIFICATION OF ADDITIVE MANUFACTURING SYSTEM It can categorized into 3 types • Liquid-Based • Solid-Based • Powder-Based
- 3. Liquid Based System – Stereolithography Apparatus (SLA) • Stereolithography (SLA) was founded in 1986 by Charles W Hull and Raymond S Freed and 1987 first commercial AM process was developed • SLA is a additive manufacturing technology for producing models, prototypes, and patterns. • The first developed AM technique is SLA . • There are several models/Products available in SLA SLA 250/30A SLA 250/50 SLA 250/50 HR
- 4. Process Of SLA • 3D systems stereolithography process creates three-dimensional plastic objects directly from CAD data. • The SLA process begins with vat filled with photo-curable liquid resin and elevator table just below the surface of liquid resin. • The operator loads 3 dimensional CAD model file into the system. • The translator converts CAD data into STL file. • The control unit slices the model and support into a series of cross-section from 0.025 mm to 0.5 mm thick. • The computer controlled optical scanning system directs and focuses the laser beam • It solidifies 2 dimensional cross section corresponding to the slice of surface of photo curable liquid resin to a depth greater than one layer thickness.
- 5. Process Of SLA • The elevator table drops enough to cover the solid polymer with another layer of liquid resin. • A leveling wiper moves across the surface to recoat next layer of resin on the surface. • The laser then draws next layer. • The process continues building the part from bottom up until the system completes the part. • Finally the part is raised from vat and cleaned the excess polymer. • The parameters are used Heat energy, layer thickness and polymer density.
- 8. Process Of SLA • The Main components of SLA are: Control computer Control panel Laser Optical system and Process chamber
- 9. Process Of SLA The workstation used by SLA system known as 3D LIGHT YEAR exploits the full power of windows NT operating system and delivers far richer functionality then UNIX based Maestro system. Maestro includes following softwares: (1) 3dverify Module. This module can be accessed to confirm the integrity and/or provide limited repair to stereolithography (STL) files before part building without having to return to the original CAD software. Gaps between triangles, overlapping or redundant triangles and incorrect normal directions are some examples of the flaws that can be identified and corrected. (2)View Module. This module can display the STL files and slice file (SLI) in graphical form. The viewing function is used for visual inspection and for the orientation of these files so as to achieve optimal building.
- 10. Process Of SLA (3) MERGE Module. By using MERGE, several SLI files can be merged into a group which can be used together in future process. (4) Vista Module. This module is a powerful software tool that automatically generates support structures for the part files. Support structures are an integral part to successful part building, as they help to anchor parts to the platform when the part is free floating or there is an overhang. (5) Part Manager Module. This software module is the first stage of preparing a part for building. It utilizes a spreadsheet format into which the STL file is loaded and set-up with the appropriate build and recoat style parameters. (6) SliceTM Module. This is the second stage of preparing a part for building. It converts the spreadsheet information from the Part Manager module to a model of three-dimensional cross sections or layers. (7)Converge Module. This is the third and last stage of preparing a part for building. This is the module which creates the final build files used by the SLA.
- 11. Principle Of SLA • The SLA process is based fundamentally on following priniciple: (1) Parts are built from a photo-curable liquid resin that cures when exposed to a laser beam (basically, undergoing the photopolymerization process) which scans across the surface of the resin. The raw material is Photosensitive thermoset polymers used in this process. (2) The building is done layer by layer, each layer being scanned by the optical scanning system and controlled by an elevation mechanism which lowers at the completion of each layer.
- 12. Photopolymers There are many types of liquid photopolymers – solidified by exposure to electro-magnetic radiation, including wavelengths in the gamma rays, X-rays, UV and visible range, or electron-beam (EB) UV-curable photopolymers are resins There are a large variety of them and some may contain fillers and other chemical modifiers to meet specified chemical and mechanical requirements The process through which photopolymers are cured is referred to as the photopolymerization process.
- 13. PHOTOPOLYMERIZATION • Polymerization is the process of linking small molecules (known as monomers) into chain-like larger molecules. • When the chain-like polymers are linked further to one another, a cross-linked polymer is said to be formed. • Photopolymerization is polymerization initiated by a photochemical process whereby the starting point is usually the induction of energy from the radiation source. It terminates for recombination.
- 15. The free-radical photo polymerization process Photo initiator molecules, Pi, which are mixed with the monomers, M, are exposed to a UV source of actinic photons, with energy of hν . The photo initiators absorb some of the photons and are in an excited state. Some of these are converted into reactive initiator molecules, P•, after undergoing several complex chemical energy transformation steps. These molecules then react with a monomer molecule to form a polymerization initiating molecule, PM•. This is the chain initiation step. Once activated, additional monomer molecules go on to react in the chain propagation step, forming longer molecules, PMMM• until a chain inhibition process terminates the polymerization reaction.
- 16. Advantages and Disadvantages The main advantages of using SLA are: (1) Round the clock operation. The SLA can be used continuously and nattended round the clock. (2) Good user support. The computerized process serves as a good ser support. (3) Build volumes. The different SLA machines have build volumes ranging from small to large to suit the needs of different users. (4) Good accuracy. The SLA has good accuracy and can thus be used or many application areas. (5) Surface finish. The SLA can obtain one of the best surface finishes amongst RP technologies.
- 17. (6) Wide range of materials. There is a wide range of materials, from general-purpose materials to specialty materials for specific applications. The main disadvantages of using SLA are: (1) Requires support structures. Structures that have overhangs and undercuts must have supports that are designed and fabricated together with the main structure. (2) Requires post-processing. Post-processing includes removal of supports and other unwanted materials, which is tedious, time consuming and can damage the model. (3) Requires post-curing. Post-curing may be needed to cure the object completely and ensure the integrity of the structure.
- 18. Applications The SLA technology provide methods for reducing time to market, lowering product development costs, gaining greater control of their design process and improving product design. (1) Models for conceptualization(an elaborated concept), packaging and presentation. (2) Prototypes for design, analysis, verify ,functional testing. (3) Parts for prototype tooling and low volume production tooling. (4) Investment casting, sand casting and molding. (5) Tools for fixture and tooling design, and production tooling. It is used as a tooling for Injection moulding.
- 19. Solid Based System – Fused Deposition Modelling (FDM) • Fused Deposition Modelling (FDM) was founded in early 1990 by Stratasys.Inc. • FDM is a additive manufacturing technology for producing models, prototypes, and patterns. • There are several models/Products available in FDM FDM 3000 FDM Maxum FDM Titan
- 20. Process of FDM • In this patented process , 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 SupportWork software. • 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. Support structure required when the CAD model having an angle of below 45 degree. • The modelling 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. Support material is used to support overhanging sections and undercutting sections.
- 21. Process Of FDM • 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. Reduce the warpage of processed parts by printing with raft on, proper bed preparation and using sticking agent. • 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 • Secondary material, or release material, is used to produce the support structures.
- 22. Fused Deposition Modeling (FDM) Z-motion Melting head with XY-motion Build material wire spools: (a) Part (b) Support Extrusion nozzles Part Support Foam base Materials: ABS, Polycarbonate (PC), Polyphenylsulfonen (PPSF)
- 23. Principle Of FDM • 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.
- 24. Advantages of FDM (1)Fabrication of functional parts: FDM process is able to fabricate prototypes with materials that are similar to that of the actual molded product. With ABS, it is able to fabricate fully functional parts that have 85% of the strength of the actual molded part. This is especially useful in developing products that require quick prototypes for functional testing. (2)Minimal wastage: The FDM process build parts directly by extruding semi-liquid melt onto the model. Thus only those material 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 WaterWorks 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.
- 25. Advantages of FDM (4)Ease of material change: Build materials, supplied in spool form (or cartridge form in the case of the Dimension or Prodigy Plus), 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. • Restricted accuracy • Slow process • Unpredictable shrinkage Disadvantages of FDM
- 26. APPLICATION OF FDM • FDM can be used in following general application: (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.