In this chapter, a literature studies were explained by the researcher which include literature studies related to particularly 3d printing in industries. By contrast, 3D printing is the process of creating an object using a machine that puts down material layer by layer in three dimensions until the desired object is formed. A previous research also had been stated and summarized in order to show the parameters selected for this experiment. All of the information in this chapter was obtained from the resources of journals, books and also website.
Today you can make parts, appliances and tools in a wide variety of materials right from your home or workplace. Using a computer, simply create, modify or download a digital 3D model of an object. It removes the long process of manufacturing for batch of one. Compared to traditional machining, 3D printing is a process of creating objects directly by stacking layers of material on each other until the required product is obtained.
The layers are stacked up in a variety of ways depending on the technology being used. (Shiwpursad Jasveer, Xue Jianbin, 2018).
3D printing, also referred to as additive manufacturing or rapid prototyping technologies, has gained popularity during recent years due to rapid technical development in the area. It is simpler, cheaper, smaller and more convenient to use than traditional manufacturing technology. 3D printing has had the most profound impact on the biomedical feld. A number of medical schools and centers have adopted 3D printers in their education and training programs.
(siewhui, pan, 2018).
There is a variety of printing technologies to create an object from digital design. The main difference between these processes are in the way of deposited layers to create the object and type of each material used. Some methods melt or soften material to produce the layers, while other used different sophisticated technologies.
Each method has its own advantages and drawbacks. Here are some common technologies
The need to reduce time and manufacturing cost while maintaining or improving quality and repeatability is a known challenge in industry. This challenge is even more realistic in composite part fabrication, where many manufacturers are seeking new methods to reduce product development costs and cycle times. FDM has been used widely for prototyping for many years. To some extent, its ability to provide a variety of pattern, mold, and tooling options that can significantly reduce costs and cycle times has been demonstrated.
The Fused Deposition Modeling (FDM) process is an additive manufacturing technology. This process involves using a work head or extruder to melt a thermoplastic supplied in the form of a wire or filament and to extrude the molten thermoplastic through a small nozzle to deposit the material along a pre-planned path using computer control. It was first developed and implemented by Scott Crump from Stratasys, founded, in the 1980s.
FDM is mainly used for single and multipart prototyping and low-volume manufacturing of parts, including structural components. Fused Deposition Modeling generally employs the use of an extruder mounted on a Computerized Numerically Controlled (CNC) machine. In this process, the build material is loaded into the heated extruder nozzle in continuous spools of modeling filament. The build material is liquified and constructed in a layer-by-layer fashion on a build platform. As the liquid leaves the extruder head, it hardens and new layers are deposited on top, until the process is completed.
FDM is a clean, simple-to-use, office-friendly 3D printing process. FDM technology builds the most accurate part of any additive fabrication system. FDM uses real production grade thermoplastics. (ojas, pranitar, 2016).
The movement of the extrusion head is controlled by servo motors or stepper motors. Depending on the part, only available for multi- extrusion 3D printing, sometimes support structures are needed to maintain the structural integrity of the part as well as give a starting point and support for overhangs for layers to be built on. These supports are constructed from a fine lattice structure of the build material or from a wax such as polyvinyl alcohol (PVA). After the part is completely done, the support structure is removed.
Despite the advantages of FDM, there are some downside, for instance, the extruder temperature plays an important role in controlling the viscosity of the liquefied product. The temperature must not be too high, to allow easy low through the nozzle orifice, yet it should not be too low, otherwise the deposed filament would not provide enough structural support for the subsequent layers. The printing speed also plays an important role, this will cause the part will or will not have strong bonding and will or will not affect the surface finish of the part.
Thermoplastics are more and more penetrating the market of filaments for fused deposition modeling (FDM) 3D printing. They have the clear advantage of reducing cost, easy to implement and can be recycled. All FDM materials have a lot in common. Each material is similar in terms of loading and building parts, office compatibility, and is safe enough to handle with no protective gear. Also, parts produced by each material are dimensionally stable and durable enough for demanding applications.
For production of finished goods, there are no shortcuts. Material stability and durable performance is key. So, carefully consider the mechanical, thermal, electrical and chemical properties and any changes that result from aging or environmental exposure. Most of the existing FDM machines use thermoplastic materials which are in a filament form for the extrusion and deposition purpose. Acrylonitrile Butadiene styrene (ABS) and Polylactide (PLA) thermoplastics are predominantly used in the process. ABS is amorphous in nature and having high impact resistance. Low thermal conductivity, heat resistance and toughness, bio-degradability and biocompatibilities are the key advantages of PLA (Ranvijay Kumar, Rupinder Singh, Ilenia Farina, (2018)).
PLA is a more printable material and has mechanical properties significantly higher than most other plastics except some kinds of polycarbonate, nylon, and composite blends. It’s had great potential because it is renewable, compostable, and biocompatible. (Ana Pilar Valerg, Moises Batist, Jorge Salguero and Frank Giro, (2018))
Polylactic acid (PLA) is one of the most common filaments utilized by hobbyists inside the 3D printing community. It’s is an environmentally friendly plastic and made of completely natural materials. It is a blend of corn starch and sugar cane derivatives that meet food-grade and biodegradability guidelines.
As a 3D printing material, PLA is solid and stands up to UV light superior than ABS plastic. It’s greener than most materials, with the special cases of clay, chocolate, and wood. In any case, it ought to be famous that in case you’re utilizing PLA for dining applications such as glasses or plates, some of the color shades may contain toxins. PLA in its natural state is straightforward, but color choices for PLA change, making it reasonable for making toys and artistic things. Blending different colors is additionally possible. PLA ordinarily prints well at 220°C, discharges no toxic fumes, and smells like hotcakes. It remains flatter and sticks to the printer bed way better than other plastics when the fabric cools. It’s also simple to re-heat PLA with a lighter or a hot air gun, such as, in arrange to repair, bend, or assemble pieces together. Be that as it may, finishing PLA is more tiring than ABS.
Acrylonitrile butadiene styrene (ABS) is one of the most successful engineering thermoplastics material with high performance in the engineering application. ABS have a desirable property which is good mechanical properties, chemical resistance and easy processing characteristic. (N Sa’ude, M Ibrahim, MHI Ibrahim, MS Wahab, R Haq, OMF Marwah, RK Khirotdin, (2018))
ABS,is a commonly utilized plastic fabric and a great material of choice for 3D printing. The reason it has been adopted so broadly is that it can be molded in addition to being extruded. ABS is cheap and can be recycled. A drawback is that it is made of oil, requiring 2 kg of oil to create 1kg of ABS plastic.
Cold ABS is marginally more adaptable than PLA. It stretches before it breaks, making it superior suited for some applications. In any case, daylight and ABS don’t get along. UV makes it delicate, and thus, it is best avoided for outdoor activities. ABS print at a marginally higher temperature than PLA but it discharges harmful vapor when running the process and requires ventilation; in any case, there has been some talk about as to whether it is unsafe.
Finished part can be joined in conjunction with glue or mellowed with petroleum solvents, which moreover gives it a cleaned look. ABS has more post-process and paint choices than PLA.
Vibration-assisted machining (VAM) combines precision machining with small-amplitude tool vibration to improve the fabrication process. It has been applied to a number of processes from turning to drilling to grinding.
There is a need to eliminate or reduce the use of cutting fluids during machining due to their ecological hazards. To achieve better surface finish, high accuracy and high precision at low cost, the vibration is introduced, in any one of the tools, workpiece and working medium in conventional and advanced machining, hence is called Vibration Assisted Machining (VAM) (Maroju, Kanmani, Vamsi, Venugopal (2014))
Vibration-assisted machining (VAM) adds small-amplitude, high-frequency tool displacement to the cutting motion of the tool. For appropriate combinations of cutting velocity, tool amplitude and frequency, the tool periodically loses contact with the chip. As a result, machining forces can be reduced and thinner chips can be generated. This in turn leads to improved surface fnishes, better form accuracy, and near-zero burr compared to conventional machining. Tool life, especially of diamond tools cutting ferrous materials, is dramatically extended by VAM. When cutting brittle materials, VAM has also been found to increase the depth of cut for which ductile-regime cutting can be achieved, allowing complex optical shapes to be made without grinding and polishing.
Types of VAM based on modes of vibration (a) 1-Dimensional VAM, (b) 2-Dimensional VAM
Increasing in the interlayer adhesion strength is attributed to the increase in polymer reptation due to ultrasonic vibration-induced relaxation of the polymer chains from secondary interactions in the interface regions.
(Alireza, Pu Han, Julio, Adithya and Hsu (2019))
As it is considered as one of the important characteristics in any functional part manufactures by conventional and unconventional processes it does the same with the FDM built parts. Surface Roughness is considered as one major challenging quest for the researches today and many of them are working on the ways to produce products with less surface roughness which will be a great addition to the functional prototypes.
Because it is considered as one of the imperative characteristics in any useful part manufactures by ordinary and offbeat processes it does the same with the FDM built parts.
Surface Roughness is considered as one major challenging journey for the researcher nowadays and numerous of them are working on the ways to create products with less surface roughness which is able to be an extraordinary expansion to the useful models. Surface roughness can be improved by implementing better build orientation, slicing strategy, use the best built parameters and post-processing. (Maidin S. and Muhamad M.K., 2015)
Surface roughness on printed prototypes increases is due to the immanent drawback in the layered manufacturing. They can be classified as layered thickness and staircase effect. The layer thickness of the part also plays an important role in surface finishing. The geometric inaccuracies and surface finishing problem can thus be controlled by minimizing the layer thickness. But minimizing the layer thickness results in maximization of build time. As the increasing layer of thickness, the surfaces roughness also increases. In any AM process, the layer by layer building process introduces an error on the amount of material used compared to the volume specified by the computer aided design model. (Mohammad Taufik, Prashant Kumar Jain, 2014). This error will be causing the staircase effect on the surface and mostly affect the dimensional accuracy and surface finish for part build as well.
A typical approach to minimize staircase defects is to print with thinner layers, which increases the accuracy of the surface approximation. This, however, is achieved at the expense of a large increase in print time (Hai-Chuan Songa, Nicolas Raya, Dmitry Sokolovb, Sylvain Lefebvrea,b (2017))
Vibration plays an important role in engineering components. When the excited frequency of component matches with its natural frequency, resonance condition occurs which leads to failure of component. Hence, it is necessary to find the natural frequency of the component. (S. Krishna Chaitanya, Dr. K. Madhava Reddy, Sai Naga Sri Harsha. Ch (2015))
By applying ultrasonic vibration on 3d printing, it will result in good bonding strength layer by layer on thermoplastic part. Having said that, ultrasonic vibration can improve the surface roughness and improving the process stability thus will prevent staircase defect.
Ultrasound is a proven technology that has been extensively used for machining and it has been claimed to improve surface quality for work piece. The use of ultrasonic vibration in different manufacturing processes well documented for more than 50 years. (S. Maidin, A.S. Mohamed, S.B. Mohamed, J. H.U. Wong and Sivarao (2017))
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