Additive Manufacturing (AM) enables the direct transformation of digital data into fabricated 3D models having a free form. This results in the formation of parts and devices that are geometrically complex. These parts can even be customized without any additional expenses. Design for manufacturing typically means that designers need to tailor their designs to accommodate limitations associated with the conventional manufacturing processes in order to ensure the feasibility of fabrication. However, this may lead to limitations and restrictions in the designers’ creative freedom for developing new products.
With abilities of 3D printing/Additive Manufacturing (AM) technology, these limitations can be eradicated. In order to take benefit out of these unique abilities, it is necessary to assist designers in exploring the unexplored regions of design spaces. We present a Design for Additive Manufacturing (DFAM) method that focuses on providing boundless design freedom to designers by getting rid of the constraints of conventional manufacturing processes.
Some uses of DFAM are:
- Fabrication of designs which have geometrically complex structures
- Creation of integrated models for the elimination of assembly procedures
- Fabrication of customized jigs and fixtures
- Enhanced functionality using complex integrated designs
FDM (Fused Deposition Modeling:
Fused deposition modeling, or FDM, is a unique method of 3D printing that utilizes additive manufacturing technique for producing 3D objects. Its wide range of applications includes prototyping, small-batch manufacturing, and hobbyist usage. Several methods of 3D printing have been developed or are in the process of development, but FDM printing remains the most common, simplest and cost-effective. This technology is for the masses.
FDM Printer and Platform
It is important to understand the process of FDM/FFF additive manufacturing.
• Additive manufacturing: This refers to the molten material, or the additive, being extruded from the inter in layers so that a 3D object can be built up one layer at a time.
• Molten material: In order for the material to be extruded, it must be fused, and for this purpose 3D printers use a heat source. Based on the type of material used, the nozzle may be heated using electric resistance coils for melting the material.
• Fused layers: The heating of the material allows for the layer of fresh, molten material to fuse well to the existing layers to create a strong and durable bond.
• Multi-directional printer extruder head and nozzle: Fused deposition modeling 3D printers have nozzles that move in both horizontal and vertical axes to get the required shape. Computer-aided manufacturing (CAM) software is used to control the direction of the extruder head and nozzle during the printing process. The nozzle head is then elevated or the platform on which the 3D printed object is taking shape is lowered to create depth.
• Infill Percentage: 3D printing is employed to manufacture objects having density from hollow to solid. How closely to one another the roads of material are deposited determines the infill percentage which then determines density and strength of the object. Common infill percentages for 3D printers can be 0, 5, 10, 15, 20, 25, 50, 75 and 100 percent.
Types of FDM Printed Materials
Different types of materials can be used for fused filament fabrication 3D printing.
Thermoplastics are the most widely used and are very popular. They include:
• ABS: Most small-level and home 3D printers use ABS, Acrylonitrile Butadiene Styrene, to fabricate many items from tools to toys. The filament form of ABS is used for FDM printing. The advantages of ABS include the different colors it is available in and its excellent strength. It is affordable as well, as it is produced in many non-proprietary forms.
• PLA: It’s a biodegradable plastic that is gaining popularity as an eco-friendly alternative to conventional plastics. The limitation is that it doesn’t have a long life or flexibility as ABS. PLA filament finds application in FDM/FFF printing while PLA resins are used in other types of 3D printing. Transparent and colored PLA is also used.
• Nylon, aka Polyamide: Nylon filament is a popular choice in FDM printing due to its many benefits. It is highly flexible, has high strength and is durable. Nylon can be easily colored prior to or after printing but is used in natural white too, so is often referred to as white plastic. Interlocking and moveable parts can be fabricated with nylon.
• PET flexible plastic: Polyethylene terephthalate (PET) is used in many commercial applications including plastic bottles and carpet fibres. PET is essentially hard, light and flexible, so it is a good choice for lightweight objects that don’t need to have too much strength.
These are the most popular plastics used in 3D printers, but not the only thermoplastics available. The list includes:
• Polycarbonate (PC) – It is very strong, and resistant to heat and impact. It has a high tensile strength and is used in the automotive and aerospace industries.
• TPE (NinjaFlex) – Thermoplastic elastomer (TEP) is the best choice when elasticity is important for the design, and it offers a very smooth feeding and good build platform adhesion.
• PETT or T-glase (tough glass) – It offers high biocompatibility and is FDA-approved for various types of food containers.
Beyond plastics, these materials can also be used for 3D printing:
• Metals: Stainless steel, gold and titanium
• LayWood/WPC: A wood/polymer composite
• Ceramics: Must be fired and glazed post-printing
• Paper
• Food: Chocolate, sugar, pasta and meat.
Reasons to use FDM Printing
• Fast prototypes: FDM is close to rapid prototyping for form, fit and functionality of the design.
• Affordability: One can save a lot of money with 3D prototyping. FDM delivers prototypes at not only a tiny fraction of the time but also at a much lower cost than conventional prototyping requires. The prototype can be edited and reprinted just as quickly and affordably.
• Complex design: FDM is the best choice for producing parts with few geometrical limitations, so it works perfectly well for producing complex geometry including undercuts.
• Marketing: This type of 3D printing can also be used to produce objects for marketing purposes, in a cost-effective, perhaps a model one wants to pitch to a client for advertising or to a toy manufacturer for general production.
• The right material for every job: The wide range of materials, those listed above, is another advantage for fused deposition modelling. If you have questions about materials, we’ll help you select the right material for your project.
• Strong bonding of parts is possible: If the design is large, it can be FFF printed in various parts that can be fused together to make a finished product that is very strong and durable.
SLS Also popularly known as SLS (Selective Laser Sintering)
The process involves the creation of 3-Dimensional physical models by the selective melting of polymer powder in a layer by layer fusion. This process employs micro-sized PA-based powder which is selectively sintered using a highly focussed CO2 laser beam. During the pre-irradiation stage for each layer, the entire bed is heated to a temperature below the sintering temperature for the material in order to reduce the thermal distortion to the part and increase the diffusion rate of atoms in order to obtain an acceptable scanning velocity. The irradiation stage enables solid state sintering between the polymer particles and consequently facilitates fusion of the irradiated layer to the previous sintered one.
This digital data is converted into an STL (Standard Tessellation Language) file format. The STL file is then digitally sliced into layers equivalent to the layer thickness desired during the fabrication of the part. For each sliced layer, the laser selectively fuses powdered material by scanning cross-sections of the object on the surface of a powder bed.
After each cross-section is scanned, the powder bed is lowered by one layer thickness, a new layer of material is applied on top and the process is repeated until the part is completed.
Advantages
• Extremely high design complexity is achievable.
• Parts fabricated from a real thermoplastic material, PA-based.
• High strength and durability of parts.
• Various types of surface finish possible with post-processing solutions.
Applications
• Fit and functional models for mechanical and thermal testing.
• Parts can be used for rapid tooling, soft tooling and short-run production cycles.
• Ideal for functional testing in load-bearing applications.
SLA (Stereolithography)
It is a Rapid Prototyping process for producing models, prototypes, patterns from 3D CAD data.
In this technology, 3D models are built from liquid a photosensitive polymer that gets solidified when exposed to ultraviolet light. The model is built upon a platform which is situated just below the surface in a vat of liquid. A low-power highly focused ultraviolet laser traces out the first layer, solidifying the object’s cross section while leaving excess areas liquid. After, an elevator incrementally lowers the platform into the liquid polymer. A sweeper re-coats the solidified layer with liquid, and the laser traces the second layer atop the first. This process repeats until the process is complete. Afterward, the solid part is removed from the vat and rinsed clean of excess liquid. Supports are removed and the model is then placed in an oven for complete curing.
Advantages
• SLA process can build complicated parts which cannot be possible by the conventional manufacturing process.
• High-quality surface finish.
• Clear model with a good resolution.
Applications
• Parts with precise features and high-quality visualization models.
• Assembly parts with accurate fit and functionality.
• Models are used for CFD and stress analysis.
• Master patterns for tools and vacuum casting.