Rule based DFM analysis for direct metal laser sintering. Direct metal laser sintering (DMLS) is one type of additive manufacturing process that allows layer by layer printing of metal parts having complex geometries directly from 3D CAD data. It uses a high-energy laser to sinter powdered metal under computer control, binding the material together to create a solid structure. DMLS is a net shape process and allows the creation of highly complex and customized parts with no extra cost incurred for its complexity.
DMLS is being used to fabricate complex metal parts that are difficult to do so using traditional manufacturing processes thus gives immense freedom to the designer while designing the component. However, there are certain Design for Manufacturability (DFM) considerations that should be taken care of while designing the parts to be printed. DFM provides guidance to the design team in making the product structure more compliant to the given manufacturing process. It removes the wall between the designing and manufacturing phases of product development thus enables designers to take advantages of all the inherent costs and other benefits available in the manufacturing process. The early considerations of DFM principles and guidelines can lead to significant cost and time cutting in the final development of the product. Some of the common guidelines for DMLS are:
The size of the part that can be printed depends upon the printer that is being used. With the current technology a maximum build size of 228 X 228 X 304 mm can be achieved. [1] Hence, the size of the part to be printed should be within required dimensions. DMLS has a minimum sintering width (depends on laser diameter) varying from 0.6 mm to 0.9 mm. This defines the minimum external feature size of the part and thus the design with any external features having smaller dimensions must be avoided. [2]
The accuracy and surface roughness of the part depends on the powder grain size ranging between 50 μm to 100 μm. The layer thickness which lies between 0.02 mm and 0.05 mm determines the resolution in the vertical direction. Therefore, the regions of the parts which require high accuracy should be designed with planned allowance of 0.1 mm to 0.5 mm and secondary finishing and/or machining operations should then be used to achieve the required accuracy. [2]
In DMLS, powder bed supports the parts and keep them held in place. However, support structures are explicitly required for most of the downward facing surfaces that make an angle less than 45 degrees with the powder bed. This is because powder bed alone is insufficient to hold the liquid phase of the metal that is created when laser is scanning the powder. Support structures are also required to restrict curling/warping of the melted powder due to high-temperature gradients. The overhangs having angles less than 45 degrees should be avoided if possible at the design stage. The main advantage of this is to reduce material usage and the post processing requirement of removing support structures from the designed components. [3]
The total number of layers required to build the whole part is directly proportional to the height of the part measured along the build direction. Every layer of the part to be printed requires tightly laying compacted thin layer of powdered material using roller, tracing of laser according to the 3D data fed to the machine in the horizontal plane and incremental lowering of powder bed for the successive layer to be laid. These processes require a significant amount of time thus redesigning the product for smaller heights may save manufacturing time greatly. [4] The build orientation should be such that the height of the part should be least along the build direction.
The main direction of heat flow which is generated by the laser at the top is along the build direction due to the fact that powder bed lying at the bottom is the major heat sink. The layered addition of material and the directional heat flow in DMLS lead to the growing of microstructural grains along the build direction leading to anisotropic properties. [5] The structure printed through DMLS has weaker properties along the build direction. This anisotropy can be removed using heat treatment methods but they are highly energy intensive and costly processes. Hence, it is advisable to consider the anisotropy in the very beginning of designing such structural parts and the direction of largest stress in the structure should lie in the horizontal plane.
Being an additive manufacturing technique, DMLS doesn't incur any extra cost for the complexity of the part. The build volume along with the number of layers is what determines the production cost and time. DMLS eliminates the need for tool production however such technologies are impervious to economies of scale. Therefore, it is recommended to design parts with least amount of superfluous volumes, building only the relevant geometries. [6] Furthermore, the parts should be designed to avoid assembly requirements because printing sub-assembly with intricate geometries is now possible. [7]
Powder metallurgy (PM) is a term covering a wide range of ways in which materials or components are made from metal powders. PM processes are sometimes used to reduce or eliminate the need for subtractive processes in manufacturing, lowering material losses and reducing the cost of the final product. This occurs especially often with small metal parts, like gears for small machines. Some porous products, allowing liquid or gas to permeate them, are produced in this way. They are also used when melting a material is impractical, due to it having a high melting point, or an alloy of two mutually insoluble materials, such as a mixture of copper and graphite.
Selective laser sintering (SLS) is an additive manufacturing (AM) technique that uses a laser as the power and heat source to sinter powdered material, aiming the laser automatically at points in space defined by a 3D model, binding the material together to create a solid structure. It is similar to selective laser melting; the two are instantiations of the same concept but differ in technical details. SLS is a relatively new technology that so far has mainly been used for rapid prototyping and for low-volume production of component parts. Production roles are expanding as the commercialization of AM technology improves.
3D printing or additive manufacturing is the construction of a three-dimensional object from a CAD model or a digital 3D model. It can be done in a variety of processes in which material is deposited, joined or solidified under computer control, with the material being added together, typically layer by layer.
Ceramic forming techniques are ways of forming ceramics, which are used to make everything from tableware such as teapots to engineering ceramics such as computer parts. Pottery techniques include the potter's wheel, slip casting and many others.
Design for manufacturability is the general engineering practice of designing products in such a way that they are easy to manufacture. The concept exists in almost all engineering disciplines, but the implementation differs widely depending on the manufacturing technology. DFM describes the process of designing or engineering a product in order to facilitate the manufacturing process in order to reduce its manufacturing costs. DFM will allow potential problems to be fixed in the design phase which is the least expensive place to address them. Other factors may affect the manufacturability such as the type of raw material, the form of the raw material, dimensional tolerances, and secondary processing such as finishing.
Titanium powder metallurgy (P/M) offers the possibility of creating net shape or near net shape parts without the material loss and cost associated with having to machine intricate components from wrought billet. Powders can be produced by the blended elemental technique or by pre-alloying and then consolidated by metal injection moulding, hot isostatic pressing, direct powder rolling or laser engineered net shaping.
Electron-beam additive manufacturing, or electron-beam melting (EBM) is a type of additive manufacturing, or 3D printing, for metal parts. The raw material is placed under a vacuum and fused together from heating by an electron beam. This technique is distinct from selective laser sintering as the raw material fuses have completely melted. Selective Electron Beam Melting (SEBM) emerged as a powder bed-based additive manufacturing (AM) technology and was brought to market in 1997 by Arcam AB Corporation headquartered in Sweden.
Rapid prototyping is a group of techniques used to quickly fabricate a scale model of a physical part or assembly using three-dimensional computer aided design (CAD) data. Construction of the part or assembly is usually done using 3D printing or "additive layer manufacturing" technology.
Digital modeling and fabrication is a design and production process that combines 3D modeling or computing-aided design (CAD) with additive and subtractive manufacturing. Additive manufacturing is also known as 3D printing, while subtractive manufacturing may also be referred to as machining, and many other technologies can be exploited to physically produce the designed objects.
Selective laser melting (SLM) is one of many proprietary names for a metal additive manufacturing (AM) technology that uses a bed of powder with a source of heat to create metal parts. Also known as direct metal laser sintering (DMLS), the ASTM standard term is powder bed fusion (PBF). PBF is a rapid prototyping, 3D printing, or additive manufacturing technique designed to use a high power-density laser to melt and fuse metallic powders together.
Binder jet 3D printing, known variously as "Powder bed and inkjet" and "drop-on-powder" printing, is a rapid prototyping and additive manufacturing technology for making objects described by digital data such as a CAD file. Binder jetting is one of the seven categories of additive manufacturing processes according to ASTM and ISO.
Solid Concepts, Inc. is a custom manufacturing company engaged in engineering, manufacturing, production, and prototyping. The company is headquartered in Valencia, California, in the Los Angeles County area, with six other facilities located around the United States. Solid Concepts is an additive manufacturing service provider as well as a major manufacturer of business products, aerospace, unmanned systems, medical equipment and devices, foundry cast patterns, industrial equipment and design, and transportation parts.
TRI-D is a 3D printed metal rocket engine. Students from the Students for the Exploration and Development of Space at University of California, San Diego built the metal rocket engine using a technique previously confined to NASA, using a GPI Prototype and Manufacturing Services printer via the Direct metal laser sintering (DMLS) method. UCSD students were the first group in the world to 3D print a rocket engine of its size, other than NASA as of February 2014. The Tri-D engine cost US$6,800.
Fused filament fabrication (FFF), also known as fused deposition modeling, or filament freeform fabrication, is a 3D printing process that uses a continuous filament of a thermoplastic material. Filament is fed from a large spool through a moving, heated printer extruder head, and is deposited on the growing work. The print head is moved under computer control to define the printed shape. Usually the head 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. The speed of the extruder head may also be controlled to stop and start deposition and form an interrupted plane without stringing or dribbling between sections. "Fused filament fabrication" was coined by the members of the RepRap project to give an acronym (FFF) that would be legally unconstrained in its use.
In design for additive manufacturing (DFAM), there are both broad themes and optimizations specific to a particular AM process. Described here is DFM analysis for stereolithography, in which design for manufacturability (DFM) considerations are applied in designing a part to be manufactured by the stereolithography (SLA) process. In SLA, parts are built from a photocurable liquid resin that cures when exposed to a laser beam that scans across the surface of the resin (photopolymerization). Resins containing acrylate, epoxy, and urethane are typically used. Complex parts and assemblies can be directly made in one go, to a greater extent than in earlier forms of manufacturing such as casting, forming, metal fabrication, and machining. Realization of such a seamless process requires the designer to take in considerations of manufacturability of the part by the process. In any product design process, DFM considerations are important to reduce iterations, time and material wastage.
3D metal moulding, also referred to as metal injection moulding or (MIM), is used to manufacture components with complex geometries. The process uses a mixture of metal powders and polymer binders – also known as "feedstock" – which are then injection moulded.
Digital manufacturing is an integrated approach to manufacturing that is centered around a computer system. The transition to digital manufacturing has become more popular with the rise in the quantity and quality of computer systems in manufacturing plants. As more automated tools have become used in manufacturing plants it has become necessary to model, simulate, and analyze all of the machines, tooling, and input materials in order to optimize the manufacturing process. Overall, digital manufacturing can be seen sharing the same goals as computer-integrated manufacturing (CIM), flexible manufacturing, lean manufacturing, and design for manufacturability (DFM). The main difference is that digital manufacturing was evolved for use in the computerized world.
Design for additive manufacturing is design for manufacturability as applied to additive manufacturing (AM). It is a general type of design methods or tools whereby functional performance and/or other key product life-cycle considerations such as manufacturability, reliability, and cost can be optimized subjected to the capabilities of additive manufacturing technologies.
A variety of processes, equipment, and materials are used in the production of a three-dimensional object via additive manufacturing. 3D printing is also known as additive manufacturing, because the numerous available 3D printing process tend to be additive in nature, with a few key differences in the technologies and the materials used in this process.
Cold spray additive manufacturing (CSAM) is a particular application of cold spraying, able to fabricate freestanding parts or to build features on existing components. During the process, fine powder particles are accelerated in a high-velocity compressed gas stream, and upon the impact on a substrate or backing plate, deform and bond together creating a layer. Moving the nozzle over a substrate repeatedly, a deposit is building up layer-by-layer, to form a part or component. If an industrial robot or computer controlled manipulator controls the spray gun movements, complex shapes can be created. To achieve a 3D shape, there are two different approaches. First, to fix the substrate and move the cold spray gun/nozzle using a robotic arm; the second one is to move the substrate with a robotic arm, and keep the spray-gun nozzle fixed. There is also a possibility to combine these two approaches either using two robotic arms or other manipulators. The process always requires a substrate and uses only powder as raw material.