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13 th^ January, 2022
JAZIB ALI (F2020134013)
ADDITIVE MANUFACTURING
1. WHAT IS ADDITIVE MANUFACTURING
In layman’s terms, additive manufacturing, often known as as 3D printing, is a manufacturing method in which a variety of materials are laid down layer by layer to construct a three-dimensional product to satisfy specific needs. A. Brief History of Additive Manufacturing This unique 3D printing technology creates physical 3D objects in 7 steps by converting digital files either created on a Computer-aided design (CAD), Computer-aided manufacturing (CAM) program, or a 3D scanner. Chuck Hull an American engineer of 3D Systems corporation is accredited with inventing 3D printing in 1983 known as solid imaging process called stereolithography (3D Printing), the first commercial rapid prototyping technology and also the STL file format. Thanks to Hull his contribution of STL file format, digital layer slicing, and infill strategies are still being used in many additive manufacturing processes today. More than enough statistics support the claim that the introduction of 3D Printing has revolutionized the industrial world in a way no other
product has achieved this momentous success in the last 35 years.There are many different 3D printing processes floating about.
2. ADDITIVE MANUFACTURING Additive manufacturing (AM) can be described as a technique of blending materials by either fusion, binding’s, or solidifying materials such as liquid resin and powders. It builds part in a layer-by-layer fashion using 3D CAD modeling. The terminologies such as 3D printing (3DP), rapid prototyping (RP), direct digital manufacturing (DDM), rapid manufacturing (RM), and solid freeform fabrication (SFF) can be used to describe AM processes. AM processes fabricate components using 3D computer data or Standard Tessellation Language (STL) files, which contain information regarding the geometry of the object. AM is very useful when low production volumes, high design complexity, and frequent design changes are required. It offers the possibility to produce complex parts by overcoming the design constraints of traditional manufacturing methods.. Although, AM has many benefits, its applications are still limited because of its low accuracy and long build times compared to CNC machines. It does not have the same constraints as CNC machining because it segregates the part in cross sections with a resolution equal to that of the process. Nevertheless, the accuracy and build time can be improved by employing suitable part orientation. Optimized part orientation can enhance the accuracy and diminish the building time and support volume, which in turn minimizes the part production cost. 3. DIVERSITY IN ADDITIVE MANUFACTURING "Three dimensional Data Display by Automatic Preparation of a three dimensional Model,” published by Kodama in the 1980s, was the first time AM was shown. In 1987, Chuck Hull (courtesy of 3D systems) invented STL, a technology that uses a laser to modify tiny layers of ultraviolet (UV) light sensitive liquid polymer. With fewer skilled personnel, quicker delivery times, and shorter product life cycles, it can successfully create complicated and customized items. Shown below is a graph to have a view on how greatly the AM market has grown in recent years making its market growth surpass $10 billion worldwide.
application. Brief details of each of these fi ve types are
given below:
- Subtractive Technology Subtractive technology is a technique for producing a desired geometry by removing layers of materials. Subtractive technologies have evolved dramatically over the previous two decades. Traditional code generation, such as G and M codes, have been supplanted by three dimensional complex surface modeling software. Unlike the computer numerical control (CNC) machines of the 1940s, the contemporary lineage of CNC machines is highly automated based upon the integration of computer-aided design (CAD)/ computer-aided manufacturing (CAM) systems
- Joining Technology Joining technology such as welding consists of joining two or more workpieces together to produce the required shape. Some of the commonly used joining processes are enlisted below. Welding Soldering Brazing Fasteners (including nut-bolt, nail, hook, clip, clutch, button, zipper, etc.) Adhesive bonding Resin bonding Cotter joint Knuckle joint, etc.
- Dividing Technology Dividing technology such as sawing is the opposite site of joining process.
•For Solid Materials: FDM: The working of FDM as shown in Figure is based on the principle of layered manufacturing technology. In this technology, the plastic raw materials (fi laments) are extruded through the nozzle, which is heated to melt the material. The nozzle head moves according to the tool path, which is generated for each layer.
FEF: This process was developed at the University of Missouri– Rolla,and it worked by extrusion of an aqueous ceramic paste. In this technology, the paste was extruded layer-by-layer into a build chamber, which was kept below room temperature in order to achieve the freezing of the paste. It was an environment-friendly approach because only water was utilized as the binding media. Solid loading as high as 60 vol.% had been achieved with this method using aluminum oxide (Al203).
technology, a pseudo-plastic paste mixed with ceramic particles was extruded to fabricate a part. The movement of the nozzle was controlled through the instructions generated by the software using the information from the CAD model. It is very similar to FDM, but its principle depends on the pseudo- plasticity, in contrary to solidifi cation in order to maintain parts shape.
- Liquid-Based AM: SLA: In SLA, a vat of liquid photopolymer resin is utilized to build parts in a layer-by-layer fashion. This part is subsequently hardened or cured using the UV light. The building platform moves down the object as the layers are being made after each new layer is cured.
MJM: In MJM, multiple nozzle jets to supply a UV curable polymer or wax as required. When the printed polymer gets out of the head, the UV lamp fl ashes to cure the material. The MJM prints parts on a moving platform that moves down after the current layer is cured in order to continue the process. It is a cost-eff ective technique because it can fabricate parts in a lesser amount of time. The MJM process is safe and quiet and therefore can be used for printing polymeric parts in the laboratory environment. However, in this process, the strength of parts and part quality are relatively poor.
- Powder-Based AM: Also know as Powder bed fusion (PFB) is a subset of AM, whereby a heat source usually laser or thermal print head is used to consolidate material in powder form to form 3D objects. 3DP: In 3DP, a liquid binder is utilized to bond the powder materials. The powder layer is spread on the building platform and the binder liquid is extruded through nozzles depending on the cross section of the 3D model. This process does not require additional support structure, instead the support is provided by the unbound powder particles
EBM: The electrons are emitted from a fi lament, which is heated at above 2500°C. These high-energy electrons are accelerated through the anode. The magnetic fi eld of lenses focuses the beam and electromagnetically scans the layers. The powder particles are fed by gravity from hoppers and are raked into layers across the building table. The entire process is carried out under vacuum, which eliminates impurities and yields high strength.
SLM: In SLM, the part is fabricated layer-by-layer through selectively melting the metal powder using a laser in SLM. The mechanical properties of parts manufactured by SLM are nearer to those produced through conventional manufacturing techniques. The implementation in industries is limited due to several obstacles. One of the primary hindrances is the presence of high residual stresses and large deformations in the part. Moreover, it is diffi cult to maintain consistent quality during the build-up process, thus causing varying porosity within the part. PRO METAL: Pro metal can be defi ned as a 3DP process to build injection tools and dies. It is a powder-based process in which mainly stainless steel is used as the raw material. The printing process occurs when a liquid binder is sprayed on to the steel powder. The powder is located in a powder bed which is controlled with the help of pistons. After fabrication of each layer, the bed lowers down and the feed piston provides the material for the subsequent layers. In case of a mold, no post- processing is needed; however, the building of a functional part requires sintering, infi ltration, and fi nishing processes.
LMD: In this technology, the 3DP head is generally connected to a robotic arm, which comprises nozzles to deposit metal powder on the building platform. The laser beam provides the required energy and melts the powder particles to fabricate the desired geometry.
Powder bed Fusion processes especially selective laser sintering is one of the early industrial additive manufacturing techniques. This method uses a laser or electron beam to melt the powdered material and fuse them together to create a solid object. Direct metal laser sintering, selective laser sintering, Multi Jet Fusion, Electron beam melting, selective laser melting, and Selective heat sintering are the main types of powder bed fusion. Advantages:
- There is a range of post-processing methods available that can give objects a very smooth finish.
- For this reason, PBF (powder bed fusion) is often used to manufacture functional metal parts for applications in the aerospace, automotive, medical, and dental industries.
- It is suitable for visual models and prototypes, large range of material options.
- SHS (Selective Heat Sintering) has an ability to integrated support structure, powder acts as an integrated support structure. Disadvantages:
- The limitations of PBF tend to be surface roughness and shrinkage or distortion during processing, as well as the challenges that arise from powder handling and disposal.
- Lack of structural properties in materials, size limitations, high power usage, finish is dependent on powder grain size.
3) Binder Jetting
BINDER JETTING USES A BINDING AGENT USUALLY IN LIQUID
FORM AND SELECTIVELY DEPOSITS ONTO POWDERED MATERIAL.
THE PRINT HEAD AND A POWDER SPREADER DEPOSIT
ALTERNATING LAYERS OF BONDING AGENT AND BUILD
MATERIAL TO FORM A 3D OBJECT.
ADVANTAGES:
• PARTS CAN BE MADE WITH A RANGE OF DIFFERENT COLORS,
USES A RANGE OF MATERIALS; METAL POLYMER AND CERAMICS.
• THIS PROCESS IS GENERALLY FASTER THAN OTHERS, THE
TWO-MATERIAL METHOD ALLOWS FOR A LARGE NUMBER OF
DIFFERENT BINDER-POWDER COMBINATIONS AND VARIOUS
MECHANICAL PROPERTIES.
DISADVANTAGES:
• IT IS ALWAYS NOT SUITABLE FOR STRUCTURAL PARTS DUE TO
THE USE OF BINDER MATERIAL.
• ADDITIONAL POST PROCESSING CAN ADD SIGNIFICANT TIME
TO OVERALL PROCESS.
4) Metal Extrusion
Metal Extrusion was originally developed and patent by S. Scott Crump under Fused Deposition Modeling (FDM) in the 1980s. In this additive manufacturing technique, the continuous filament of thermoplastic is fed through a heated nozzle, before being deposited layer by layer onto the build platform to create the object. Advantages:
