A list of additive manufacturing companies with descriptions of their methods and techniques.
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Additive manufacturing (AM) or additive layer manufacturing (ALM) is a three-dimensional printing process that produces components and parts by adding layers of material to fabricate physical renderings of computer designs. The multiple layers of additive manufactured parts are composed of plastics, various types of metals, and ceramics.
The initial use of additive manufacturing was for the creation of prototypes. Since its introduction, the process has evolved and gained general use due to its ability to quickly produce complex geometries that were previously too expensive to manufacture. The many choices of materials and the limited amount of waste from AM has significantly increased its popularity and made it suitable for the manufacture of consumer goods and components for several industries.
The term additive manufacturing is a generic descriptor that encompasses different types of additive manufacturing processes. Each of the various processes have their own standards and parameters. Although all types of additive manufacturing involve adding layers of materials, they vary in how they complete the layering process. The types of additive manufacturing processes include binder jetting, direct energy deposition, material extrusion, powder bed fusion, sheet lamination, and vat polymerization or stereolithography.
In addition to the types of AM processes, there are three common technologies that the process uses, which are sintering, melting, and stereolithography. The differentiation between the technologies is in regard to the treatment of the raw materials during the additive manufacturing process.
The additive manufacturing process is a major deviation from traditional manufacturing, which involves the removal or shaping of workpieces using sharp tools, molds, and dies. Unlike traditional processes, additive manufacturing builds products, layer by layer, to produce complex geometric shapes. The concept for a product is created using a computer design program, such as computer aided design (CAD). From the CAD design parameters, the computer rendering is divided into layers that an additive manufacturing device can use to build the completed product.
The additive manufacturing process begins with a model produced by 3D printing software. In many cases, the designs are items that cannot be produced by traditional methods due to their intricacy, complexity, and precision details. Computer modeling customizes a product down to the smallest detail. This aspect of the process is fundamental and the reason for its use.
During the design phase, there are factors that are closely adhered to as rules of thumb to ensure the quality of the final product. Although each type of additive manufacturing process has different basic guidelines, there are certain features that are common to all, regardless of the method. They include:
As with all types of components, wall thickness is a major concern and is closely watched to avoid the failure of a component. In addition to wall thickness, and an aspect of part design that relates to wall thickness, is supports and overhangs, which can also determine the strength and durability of a component.
Once the CAD design has been approved, it is passed on to simulation modeling that tests the many aspects of the design using a digital representation. The function of CAD software is the creation of a design that fits the requirements of the final application. Included in the CAD rendering is the dimensions and features of a component that are used as guides for the manufacturing process.
As part of testing the effectiveness of the CAD rendering, it is subjected to computer generated simulations that mimic the types of real world stresses a component could experience. Simulation modeling is used in place of the physical molding of parts. The process allows for experimentation using digital representations. Simulation modeling tests help determine if a part will fail, how it might fail, and the amount of force a part can withstand before failing. Common forms of simulation modeling are Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA), and Non-Linear Stress Analysis.
The choice of simulation modeling for pre-processing is based on economics since prototyping can be too costly for testing certain parts. In addition, it enables engineers to test concepts and troubleshoot issues before ideas become critical or dangerous. Some of the factors that are caught by simulations are material warping and bonding issues. Additive manufacturers are able to address risks of production to reduce failures using the data collected from simulation modeling.
Once a design has been tested and approved, it's ready to be transmitted to the additive manufacturing process. Interoperability refers to the ability of computer systems to communicate and share information. With additive manufacturing, manufacturing equipment is unable to receive CAD files, like CNC machines. To overcome this difficulty, CAD files have to be translated into a computer language that additive equipment can understand.
Like all industrial equipment, additive manufacturing equipment is unable to conceptualize three dimensions, which requires that part and component designs be sliced into layers. Slicing software scans the layers of a model to tell additive equipment how to create the layers of the final product. Aside from devising the slices, slicer software tells additive equipment where to fill internal lattices and columns that strengthen and shape a product.
The different types of 3D slicer software that convert CAD models to .STL, .3DF, or .Obj includes a variety of software packages that are capable of converting 3D designs into 2D layers. As with CNC machines, tool paths or G-codes are used to direct the additive manufacturing process.
Examples of 3D slicer software are:
The list of slicer software extends far beyond the five versions listed above and includes PrusaSlicer, KISSlicer, Slic3r, AstroPrint, Octoprint, and Mattercontrol. In additive printing, the choice of a slicer is critical to the making of a product. The number of slicers is long and ever growing as new technologies are developed. Additive manufacturing professionals work closely with their clients providing detailed information regarding the importance of slicers and their use.
The additive manufacturing technology being used during the printing phase can take several forms. In the most basic form, print heads alternate between placing layers of powder material with layers of binding liquid. In general terms, this layer upon layer and binding is referred to as binder jetting. With other forms of additive manufacturing, lasers are used in place of binding liquids to cure layers.
In the case of thermoplastic materials, layers are heated and applied and allowed to dry before applying the following layer. Each of the differing methods includes a unique process for securing the layers and includes laser sintering and electron beam melting (EBM). The many methods for completing additive manufacturing provides a variety of alternatives that producers can use to manufacture high quality products.
Part of the function of slicers is to offer a 3D graphic area that helps in visualizing how models are transformed into layered representations. Although not all slicers are the same, there are features that are the same for all types. Aspects that are common to all slicers are:
Shell – The shell is the first section of the product being formed and its walls. It includes the parameters that determine the perimeter of the print. In essence, the shell is the outline of the product that defines the shape of the layers. The settings for the shell are included in the slicing software that defines the G codes. In most instances, the thickness of the shell is a little higher than the required amount to provide mechanical strength and toughness.
Of the various aspects of the model, the shell is the most noticeable element that heavily influences the mechanical properties of the final product. It includes the top and bottom and walls. The shell establishes the vertical exterior that the top and bottom cover.
Wall Thickness – The wall thickness in additive manufacturing is influenced by several factors and is measured in millimeters. The wall thickness has to be large enough for wall strength and adhesion. The thickness of walls affects the strength, stability, surface finish, and appearance of the created object. For additive manufacturing, wall thickness is influenced by layer height and the diameter of the applicator’s nozzle. With resin based additive manufacturing, wall thickness is dictated by the curing properties of the liquid resin.
There can be printability issues with walls that are too thin. Equipment may avoid printing such walls or the formation of the walls can produce holes and gaps that weaken the structure of the object being formed. In all cases, thin walls lack strength and are too fragile, which makes them prone to breakage under stress. The general rule for wall thickness is the thickest wall that can be printed without causing overuse of materials and thermal stress.
Supports – Support structures are added to support overhanging or bridge structures during slicing. How much an overhang can support itself depends on the stiffness of its material. As the stiffness of a material increases, the further an overhang can extend. The complexity of the model determines the use of supports or if the model has an irregular structure. Models that have cylindrical, conical, or cuboid shapes or when the upper and lower widths of the model are the same, supports are not needed.
A basic rule for adding supports is the 45-degree principle. If the overhang, from the vertical, is less than 45o, supports will not be needed. When the overhang is greater than 45o from the vertical, supports will be required. A failure to properly use supports can lead to printing failure.
Adhesion Layers – Adhesion layers relate to the strength of the bonding between layers. Good adhesion ensures that layers fuse to create a strong and durable final product. Quality adhesion guarantees the ability of a part to endure mechanical stress and harsh environmental conditions. Factors that influence adhesion are temperature, type of material, and printer settings. To overcome problems related to adhesion, slicers offer different structures.
Brim – Brims are attached to the edge of the model and extend from the print bed. They support part structure during the printing process and keep the print in place during printing. Brims prevent warping and ensure contact with the bridge plate is rigid. They are referred to as brims because their positioning resembles the brim of a hat.
Raft – A raft is a flat piece of material that supports the base. It is wider than the first layer and similar to the brim. Unlike the brim, the raft is placed under a part to provide support.
Skirt – The skirt is extruded on the bed before the printing process begins. It primes the extruder and establishes a smooth flow of filament. Monitoring the skirt helps in detecting issues with leveling and adhesion before the modeling process begins. Skirts can be adjusted in the settings tab in relation to its position, amount of plastic being primed, and even the extruder.
Brims are a type of skirt that is attached to the edges of the model. They are printed with more outlines to create a ring around the part, like the brim of a hat. Brims hold down the edges to prevent warping and help adhesion.
Additive manufacturers explain the methods that they have chosen to produce products and assist their clients with their understanding. The unique qualities of additive manufactured products necessitate clients have an understanding of the process and its benefits. Close partnerships with additive manufacturing suppliers enhance the quality of products being produced.
Additive manufacturing takes several forms. Each of the forms uses unique technologies to create complex products with precise geometric shapes. The common denominator for all types of additive manufacturing is their adherence to producing products and parts layer upon layer using an assortment of plastics, metals and ceramics. Additive manufacturing is a precision process that produces objects with high tolerances and limited waste.
AM can be classified into three general groups, which are sintering, melting, and stereolithography. With sintering, the base material is heated without being liquified from which high-resolution objects are created. Melting involves melting the raw material using laser technology and electron beams to fuse powder particles together to produce intricate shapes with refined microstructures. The final general category is stereolithography that uses ultraviolet lasers projected into a vat of photopolymer resin, a process known as photopolymerization.
Binder jetting involves depositing an adhesive binder onto layers of powdered ceramic based material, glass, gypsum, or metal. During the process, the print head moves over the platform placing droplets of binder material. When a layer is complete, the bed moves downward and the process repeats, continuing until a part is complete. Operators may infiltrate cyanoacrylate to the process to enhance a part’s mechanical properties.
The fully layered part is in its green state when it leaves the 3D process and may be placed in an oven to achieve a sintering of a part’s grain structure. Materials used for binder jetting include metals and ceramics. It is commonly used to produce packaging, toys, and figurines. Due to the use of infiltration, metal parts produced by binder jetting have good mechanical properties and can be relatively functional.
Direct energy deposition involves melting the base material as it is deposited on a specific surface where it solidifies, fusing the applied materials. A nozzle mounted on a multi axis arm allows for variable depositing. A special sealed chamber with limited oxygen is used to complete the process. Electron beam DED systems are performed in a vacuum while laser based DED systems use an inert chamber.
Powder or wire is the form of the deposited material. Powder offers greater accuracy when being deposited while wire is more efficient in regard to material use. The normal thickness of layers varies between 0.25 mm and 0.5 mm. The rate of cooling times affects the grain structure of the final piece. All weldable metals are used in the DED process with polymers and ceramics also included.
Material extrusion deposits a filament of composite or thermoplastic material in layers to form a 3D part. The filament comes from a heated extruding nozzle mounted on a movable arm. As material passes through the nozzle, it is heated before being deposited. Material extrusion is a slow process that is less accurate than other forms of additive manufacturing. The nature of material extrusion makes it applicable for rapid prototyping.
Material extrusion is known as Fused Filament Fabrication (FFF). Normally used by DIY hobbyists, material extrusion lacks dimensional accuracy and is anisotropic, which limits its industrial use.
Powder bed fusion fuses powdered materials to form a solid object with a laser, thermal energy, and electron beam. The heat source determines each layer using accurate calculations to define the structure’s contour, mapping a fusing sequence or raster pattern.
The powder bed fusion process begins by spreading a layer of powder over the bed. The particles are melted to the form of the designed pattern by a laser. Once the first layer is completed, the building platform shifts downward to allow the forming of the next layer. The subsequent layers are bonded until a uniformly shaped part is produced.
Once the completed part cools, it is broken out and unused powder is repurposed. The extracted part is subjected to post processing to enhance its aesthetic appeal, modify features, and augment its functionality.
The two forms of PBF are laser based and binder based. With laser based, high powered lasers fuse powder particles and do selective laser sintering. Binder based PBF uses a liquid binder and a computer controlled system. Once a part is completed, it is placed in an oven to remove binder material and sinter the powder into a solid part. Powder bed fusion comes in several forms, which are chosen in accordance with the type of part being produced.
Sheet lamination takes several forms based on the material being used and the forming method. In addition, the process is categorized according to the bonding method, such as adhesive, thermal, or ultrasonic welding. Another distinction is when bonding occurs, which can be before or after shaping.
As with all forms of additive manufacturing, the basic principles of sheet lamination are the same for all methods, with slight variations. The initial step in the process is feeding bonded or unbonded material onto the build platform. With Selective Deposition Lamination (SDL) and Ultrasonic Additive Manufacturing (UAM), the layers are bonded together, and the 3D shape is cut out. Computer-Aided Manufacturing of Laminated Engineering Materials (CAM-LEM) sheet lamination cuts the layers into the designed shape and then bonds them.
Once the shape is achieved, the print block and outer edges are removed revealing the 3D product. The layer thickness for sheet lamination determines the quality of the final product and is determined by the machine and process being used. A wide range of materials can be used with sheet lamination, from paper up to various metals. Polymers use heat and pressure to create shapes while paper relies on pre-applied adhesives that are activated by heat and pressure. The term sheet lamination covers seven general forms of the process each of which is capable of producing different products and parts with metal based processes capable of producing hybrid metal parts.
Vat polymerization exposes liquid polymers to ultraviolet light that turns liquid into solids. A digital light projects a CAD design into a vat of liquid polymers layer by layer. After the exposure of the initial image, the vat is drained and the next layer is exposed to UV light, a process that is repeated until the vat is drained and the 3D object is left.
The material for vat polymerization is a photopolymer or light activated resin that changes properties when exposed to light, which causes its molecules to chain link. Stereolithography is a photopolymerization technology, which is one of the three main types of vat polymerization.
Vat polymerization is used to produce jewelry, injection molding prototypes, and various dental and medical applications. Since produced pieces are brittle, vat polymerization is limited as to the applications for which it can be used.
Multijet printing, known as material jet (MJ), forms layers like a 2D printer, depositing photoreactive material instead of ink. The droplets of material solidify when exposed to UV light. Slices from the software form the layers of the object to be printed. The material for MJP is a thermoset photopolymer resin. Different printheads in the printer can release different materials in each layer, which allows for the creation of full color multi-material parts.
The parts produced by MJP can have rigid and flexible elements in a single piece. As with other forms of additive manufacturing, dissolvable supports are used for various types of applications. Unlike other forms of 3D printers, MJP printers can build layers as thin as 16 microns (μm).
MJP is similar to selective laser sintering (SLS) and direct metal laser sintering (DMLS) that use plastics and metals to fuse them into layers to form a product. Unlike SLS and DMLS, MJP deposits droplets of photoreactive material that solidifies when exposed to UV light. The layers of MJP are formed by the succinct placement of the metal droplets. The process allows for the production of delicate, complex features with internal cavities.
As anyone in the additive manufacturing industry will tell you, the seven additive manufacturing methods described above are a sampling of the many unique technological methods used by the industry to produce complex and intricate geometries. The services that additive manufacturers provide encompass a wide range of capabilities that enable them to meet the requirements of many industrial applications. Close collaboration with additive manufacturing companies enables customers to identify and have manufactured parts that precisely match customer expectations.
With conventional manufacturing, materials are chosen by their properties for a process. They begin in one form and are transformed to a usable form. This traditional view of materials does not apply to additive manufacturing where the properties of materials are established with a parts geometry. Although raw materials have an impact, regarding chemical makeup, size, and particle distribution, process constraints determine the strength, ductility, porosity, and surface finish of completed objects.
Although the properties of materials present challenges for additive manufacturing, it also provides opportunities for adapting and adjusting various aspects of a component’s composition. When material properties of an object are determined by a part’s geometry, properties can be precision controlled in specific regions of a part, such as stiffness or flexibility.
The first use of 3D printing was stereolithography, a form of vat polymerization where resin was cured to form plastic parts. Modern additive manufacturing uses thermoplastics such as PLA and ABS for filament driven systems with high performance plastics like PEEK and PEKK becoming popular. Powder based nylons and TPU are used for bed fusion processes. Although thermosets are commonly used with vat polymerization, they are starting to be used with extrusion and laser sintering methods. Polymers for additive manufacturing come in solid filament form, pellets, liquid resins, and powders.
Powder bed fusion techniques, such as Direct Metal Laser Sintering (DMLS), SLM, and EBM Electron Beam Melting (EBM), are additive manufacturing methods that commonly use metals. Aluminum, titanium, stainless steel, Inconel and cobalt chrome meet the parameters of additive manufacturing. Reflective metals are difficult to shape with additive manufacturing and require the use of different techniques, such as blue lighting. Metals are matched to processes that will accept them since not all processes accept all metals.
Metals for additive manufacturing are provided in wire or powder form and can also be mixed with other materials. Bound metal deposition systems apply filaments or rods embedded with polymers to build green parts. In some instances, metal powder is suspended in resin or a paste format.
All metals can be processed by additive manufacturing as long as they can be provided in powder form. Obviously, metals that burn at high temperatures cannot be processed safely by additive manufacturing techniques that use sintering or melting and are processed by methods that use extrusion through a nozzle.
The use of different metals to produce different components and parts:
Composites are unique materials that are ideal for additive manufacturing. The combining of composite materials can take place prior to being deposited or during processing. Polymers with chopped carbon and glass fibers are widely used for short runs and composite layup tools. Metal matrix composites (MMCS) are blends of metal alloys and ceramics or other materials. In some instances, sheets of material are fused with layers of polymer. The different blends and composition of composites takes several forms, a factor that differentiates additive manufacturing from other processes.
As with certain metals, ceramics are used with specific additive manufacturing processes. Ceramic materials are not used with laser based systems due to the materials low absorption rate, which makes them difficult to print. They are widely used with extrusion, material jetting, and vat polymerization photopolymerization methods. Composites of ceramic slurry or blended materials are used to build green parts that can be sintered.
All of the positive aspects of additive manufacturing are found in ceramic materials. It can be used to produce complex intricate geometries and for rapid prototyping. Ceramic materials, as with most additive manufacturing, produce minimum waste and can be used to manufacture customized parts.
As with any manufacturing process, additive manufacturing has advantages and disadvantages with the major advantage being the lack of complexity in the fabricating of parts. With traditional manufacturing, getting something produced can take a major investment and a great deal of time. Additive manufacturing removes many of the obstacles associated with traditional manufacturing and can quickly produce any part.
When additive manufacturing was first introduced in the 1970s, it was a prohibitive process that had not been perfected. In the years since, the cost of additive manufacturing has been rapidly falling. Modern industrial printers are affordable and can produce products using any type of material. Complex and intricate parts can be efficiently produced using CAD software, which makes AM an affordable option.
Additive manufacturing addresses several issues related to material costs. Unlike subtractive manufacturing, additive manufacturing has extremely limited waste, with some processes producing no waste. Certain after processing functions may need to be performed, such as removing supports or burrs, but overall waste is extremely minimal. In essence, every particle of powder, wire, or resin is used to the utmost, which translates into significant cost savings.
In addition, low cost easily accessible materials can be used for additive manufacturing. The ease of consolidating parts is an additional savings factor since it lowers material and energy costs.
In all of the discussions of AM, the factor that is mentioned the most is prototyping, which takes very little time with additive manufacturing. From computer rendering to the physical part can happen in a day or a few days and does not require tooling, setup, complex planning, or any type of machining. It is simply a matter of getting an idea, entering it into a computer, and sending it to an AM machine, a cost effective and efficient process.
Although AM is unable to handle high volume production runs, it is able to produce less than a hundred products, quickly, efficiently, and at high tolerances. The elimination of the need to create tooling, molds, and machining speeds up the production process and enables the manufacturing of a few high quality parts in days instead of months.
Another cost factor that is eliminated with additive manufacturing is inventory. In traditional manufacturing, warehouses are used to store parts for delivery. Errors, volume, and facilities are costly. With additive manufacturing, parts are produced as needed and kept in a virtual inventory that can be updated, changed, and produce parts on demand.
There may be instances when a customer requires a part that is no longer kept in inventory and is unavailable. If the parameter of a part is retained in a computer file, it can be reproduced using additive manufacturing. This virtual part inventory makes it possible to phase out physical inventory and still be able to supply old parts.
For old components, new and more durable materials that weren’t available when an old part was developed can be used to produce new versions to enhance the durability, strength, and reliability of old components. When customers require the replacement of an old worn out part, they can receive a replacement of high quality.
With traditional production, complex parts require several steps, more material, and labor to be assembled. The process of assembly is costly and requires hours of work. Additive manufacturing can print a completed assembly as a single piece, saving time and money. Regardless of the complexity and intricacy of an item, it can easily be programmed and produced.
AI is being used by engineers to produce designs from downloaded data. AM and AI can work together to produce parts that meet the production parameters of the AM process. They can work in tandem to generate designs and offer improvements and suggestions to maximize production and efficiency. Every part produced closely adheres to the required specs of the design.
Lattices are strong, lightweight, and difficult to produce using traditional manufacturing. AM can produce strong, tough, intricate lattice structures with less waste. The process is capable of producing reinforced parts and assemblies that have minimal weight and material costs that save money on new part production and support.
One of the spectacular aspects of additive manufacturing is its ability to work with any type of material, which means that specialty parts and products can be made from any type of material including nitinol, gold, and carbon fibers. AM is able to produce high heat resistant, water repellent, high strength, and durable items, regardless of the types of required materials.
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