Question

Problem 4a: Describe the two RP processes - Fused Deposition Modeling (FDM) and Stereolithography Apparatus (SLA) based on (1) the process (in some details), (2) the energy source, (3) work volume, (4) material, (5) costs, (6) advantages and (7) disadvantages. Problem 4b: Describe briefly with figure one of the four AM of metals processes you have studied. What are the post processing methods you can consider for the process you have just selected?

Answer 1

Answer 4a) -

Fused Deposition Modeling :-

Fused deposition modeling (FDM), sometimes also called filament freeform fabrication, is a 3D printing process that uses a continuous filament of a thermoplastic material.[1] Filament is fed from a large spool through a moving, heated printer extruder head, and is deposited on the growing work. The head part of printer is moved under computer control to define the printed shape. Usually the top moves in two dimensions to deposit one horizontal plane, or layer, at a time; the work or the print head is then moved vertically by a small amount to begin a new layer.

1) Process :-

A fused deposition modeling (FDM) machine melts a plastic filament and extrudes it through a nozzle. The melted material is then pour down on the build platform, where it cools and solidifies. By laying down layer on layer the part is made.

Extrusion head Support material spool Part support structure Built part Build platform Build material spool © additively.com

stepper motor filament- filament width small gec large gear bearing - extruder hot end thermistor or thermocouple heater extrusion width

FDM requires support structures which anchors the parts on the build platform and supports overhanging structures. Through the utilization of a second nozzle, the support structure are often inbuilt a special material. Several parts are often produced at an equivalent time as long as they're all anchored on the platform.

2) Energy :- The process starts with importing an STL file of a model into a pre-processing software. This model is oriented and mathematically sliced into horizontal layers varying from 0.127 - 0.254 mm thickness. A support structure is made where needed, supported the part's position and geometry. After reviewing the trail data and generating the toolpaths, the info is downloaded to the FDM machine.

The system then runs in X, Y and Z axes, drawing the model one layer at a time. This process is analogous to how a hot glue gun extrudes melted beads of glue. The temperature-controlled extrusion head is fed with thermoplastic modelling material that's heated to a semi-liquid state. the top extrudes and directs the fabric with precision in ultrathin layers onto a fixtureless base. The results of the solidified material laminating to the preceding layer may be a plastic 3D model built up one strand at a time.

3) Work Volume :- Maximal building envelope: 914x610x914 mm3
Minimum featured size: 0.178 mm
Typical tolerance: +/-0.178 mm (can be improved through post-processing)
Minimum layer thickness: 0.178 mm

4) Material :- Various materials are available with different trade-offs between strength and temperature properties. also as acrylonitrile butadiene styrene (ABS)polymer,polycarbonates,polycaprolactone, polyphenylsulfones and waxes. water-soluble material are more likely be used for creating temporary supports while prototyping is ongoing , because this soluble support material is quickly dissolved with specialized mechanical agitation equipment utilizing a precisely heated caustic soda solution.

5) Cost :- How much do parts cost?
The cost to make a neighborhood on FDM depends on the time and materials wont to create the part. Since FDM builds upon layers, complexity is a smaller amount of a problem on cost and rather it's the work to make mass that consumes resources. Therefore, creating bigger parts becomes costly using FDM. Small parts are often created for under $50, with larger parts costing more.

How quickly can parts be manufactured?
Like cost, the time it takes to make a neighborhood using FDM depends on the dimensions of the part. Each layer created requires time to line before subsequent layer are often placed on top and therefore the process to continue. So it are often seen that dimensionally longer parts with mass will take longer to make instead of smaller, hollow parts. The home in tame it takes to make these parts will vary from a few of hours to multiple days.

6) Advantages/Disadvantages :- Fused deposition modeling process can build fully functional parts in standard plastics. However, they need an anisotropy within the z-direction (vertical direction) and a step-structure on the surface.

Fused deposition modeling works with standard materials, as an example ABS or PC. So that, parts have good mechanical properties and are durable over time. Parts are often post-processed as any plastic part produced with conventional manufacturing.

Through the deposition of extruded material layer-by-layer, parts have an anisotropy within the z-direction (vertical direction), the surface features a step-structure and fine details can't be realized.

Stereolithography Apparatus :-

Stereolithography process is also known as stereolithography apparatus, optical fabrication, resin printing or photo-solidification. This may be kind of 3D printing technology used for creating models, prototypes, patterns, and production parts at the time of layer by layer fashion using photochemical processes by which light causes chemical monomers and oligomers to cross-link together to make polymers.[1] Those polymers then structure the body of a three-dimensional solid. Stereolithography are often wont to create prototypes for products in development, medical models, and hardware , also as in many other applications. While stereolithography is fast and may produce almost any design, it are often expensive.

1) Process :-

It is an additive manufacturing process that, works by focusing an ultraviolet (UV) laser on to a vat of photopolymer resin.[13] With the assistance of computer aided manufacturing or CAD (CAM/CAD) software,[14] the UV laser is employed to draw a pre-programmed design or shape on to the surface of the photopolymer vat. Photopolymers are more sensitive to ultraviolet rays, so that the resin is photochemically solidified and forms one layer of the specified 3D object.[15] Then, the build platform lowers one layer and a blade recoats the highest of the tank with resin.[4] This process is repeated for every layer of the planning until the 3D object is complete. Completed parts must be washed with a solvent to wash wet resin from their surfaces.[16]

In stereolithography it is also possible to print objects "bottom up" by employing a vat with a transparent bottom and focusing the UV or deep-blue polymerization laser upward through rock bottom of the vat.[16] An inverted stereolithography machine starts a print by lowering the build platform to the touch rock bottom of the resin-filled vat, then moving upward the peak of 1 layer. The UV laser then writes the bottom-most layer of the specified part through the transparent vat bottom. Then the vat is "rocked", flexing and peeling rock bottom of the vat faraway from the hardened photopolymer; the hardened material detaches from rock bottom of the vat and stays attached to the rising build platform, and new liquid photopolymer flows in from the sides of the partially built part. The UV laser then writes the second-from-bottom layer and repeats the method . this bottom-up mode is that the build volume are often much bigger than the vat itself, and merely enough photopolymer is required to stay rock bottom of the build vat continuously filled with photopolymer.

Lenses - X-Y scanning mirror Laser beam Laser Vat Elevator Liquid photopolymer Sweeper Layered part Build platform Copyright 2008 CustomPartNet

2) Energy Source :- This process requires the utilization of supporting structures which attach to the elevator platform to stop deflection thanks to gravity, resist lateral pressure from the resin-filled blade, or retain newly created various sections during the vat rocking process of bottom up printing. Supports are typically created automatically during the preparation of CAD models and may even be made manually. In both situation, the supports must be removed manually after printing.

3) Work Volume :- Stereolithographic process models are used as an aid to diagnosis, preoperative planning and implant design and manufacture. This might involve planning and rehearsing osteotomies, for instance . Surgeons use models to assist plan surgeries[23] but prosthetists and technologists also use models as an aid to the planning and manufacture of custom-fitting implants. as an example , medical models created through stereolithography are often wont to help within the construction of Cranioplasty plates.

4) Advantages/Disadvantages :-

Advantages
One of the benefits of stereolithography is its speed; functional parts are often manufactured within each day. The length of your time it takes to supply one part depends upon the complexity of the planning and therefore the size. Printing time can last anywhere from hours to quite each day . Prototypes and styles made with stereolithography are strong enough to be machined and may even be wont to make master patterns for injection molding or various metal casting processes.

Disadvantages
Although stereolithography are often wont to produce virtually any synthetic design, it's often costly, though the worth is coming down. Common photopolymers that when cost about US$200 per liter, are now US$40 per liter, and professional SLA machines can cost US$250,000. Since 2012, however, public interest in 3D printing has inspired the planning of several consumer SLA machines which may cost considerably less: from US$3,500 for the shape 2 by Formlabs, Beginning in 2016, substitution of the SLA and DLP methods employing a high resolution, high contrast LCD panel has brought prices right down to below US$200. The layers are created in their entirety since the whole layer is displayed on the LCD screen and is exposed using UV LEDs that lie below. Resolutions of .01mm are attainable. Another disadvantage is that the photopolymers are sticky, messy, and wish to be handled. Newly made parts got to be washed, further cured, and dried.

Answer 4b) -

Photopolymerization printing techniques, like stereolithography, digital light processing, continuous liquid interface production, two-photon polymerization, and lithography-based 4D printing, utilize photosensitive polymer resins, which are selectively cured layer by layer using laser or digital light projection source. These lithographic 3D printing techniques are being increasingly wont to fabricate composite materials and ceramic (Al2O3, ZrO2, etc.) objects. The mixture of nano- and microscale fillers into photoresins can, however, end in challenges like a rise in viscosity of the resin, inhomogeneity thanks to settled filler particles and lightweight scattering. during this chapter, the elemental processes involved in photopolymerization-based 3D printing are introduced. Strategies to beat the aforementioned challenges, like modification of process parameters, dispersion processes, and surface treatment, are going to be described. Recent progress within the development of functional photoactivated resin formulations and composites and their applications, starting from 4D printing to the energy field.

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