Multi-material 3D printing

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Multi-material 3D printing is the additive manufacturing procedure of using multiple materials at the same time to fabricate an object. Similar to single material additive manufacturing it can be realised through methods such as FFF, SLA and Inkjet (material jetting) 3D printing. By expanding the design space to different materials, it establishes the possibilities of creating 3D printed objects of different color or with different material properties like elasticity or solubility. The first multi-material 3D printer Fab@Home became publicly available in 2006. The concept was quickly adopted by the industry followed by many consumer ready multi-material 3D printers.

Contents

Multi-material 3D printing Technologies

Fused Filament Fabrication (FFF)

Single-Nozzle FFF Design Single nozzle.svg
Single-Nozzle FFF Design
Multi-Nozzle FFF Design Multi nozzle.svg
Multi-Nozzle FFF Design
A SLA Multi-Material Design A SLA multi-material design.svg
A SLA Multi-Material Design
Material Jetting 3D Printing Inkjet 3D Printing.svg
Material Jetting 3D Printing
Schematic of a Binder Jetting 3D Printer Schematic of a Binder Jetting 3D Printer.svg
Schematic of a Binder Jetting 3D Printer
The Prusa3d Multi-Material Upgrade Prusa Multi-Material Upgrade.jpg
The Prusa3d Multi-Material Upgrade

Fused Filament Fabrication (also known as Fused Deposition Modeling - FDM) describes the process of continuously extruding a line of thermoplastic material to form a three dimensional model. [1] The FFF process supports a variety of materials reaching from bio degradable ones like PLA to PETG, ABS and engineering grade materials like PEEK. This technology additionally allows for the use of flexible materials like TPU. [2] Two possible solutions to realise a multi-material FFF 3D printer are:

Single Nozzle Design

The single nozzle design combines the different materials before or in the melting zone of the print head such that the materials are extruded through the same nozzle. [2] For example: The different filaments can be cut and rejoined to a single strand of a mixed filament before being fed into the melting chamber. Such a technique is implemented in the Mosaic Palette. [3] Another example is the multi-material upgrade by Prusa3d, which is mounted on top of a single material printer to add multi material capabilities. [4] It uses a bowden style extrusion system with an additional axis to cut and select the material. To prevent impurities inside of the object a combined melting chamber has to be cleared from the previous material before a new one can be used. Depending on the implementation, the amount of waste material produced during the printing process may be significant. [2] In some implementations, the previous material may be used as in-fill to prevent waste, or to simultaneously print a different object in which color does not matter.

Multi-Nozzle Design

A printer with two print heads, that share 2 degrees of freedom. Independent Print Heads.jpg
A printer with two print heads, that share 2 degrees of freedom.

The multi-nozzle design features a separate nozzle for each material. [5] The nozzle can either be mounted on the same print head or on independent print heads. For this approach to work the different nozzles have to be calibrated to the exact same height relative to the print surface to circumvent the interference of an inactive nozzle with the printed object. Such a design reduces the amount of waste material during the printing process significantly [5] compared to a single nozzle design which does not use the previous material as in-fill or to print another object.

Stereolithography (SLA)

Stereolithography is the process of solidifying a photopolymer with a laser layer by layer to form a three dimensional object. To realize multi-material prints [6] with this technology, one can use multiple reservoirs for different photopolymers. A major problem with this approach is the removal of the not yet polymerised material as the print may contain cavities filled with the old material, which should be emptied before the next material can be used. [6] The photopolymer resins used for SLA can have highly different physical properties, generally being more brittle and having a lower heat deflection temperature. The SLA standard resins come in different colours and opacities. Besides the engineering grade materials like the ABS-like or PP-like resin, there exist bio-compatible ones used for medical applications and flexible resins. [2]

Material Jetting

Material Jetted Model of a Human Head Material Jetted Model of a Human Skull.jpg
Material Jetted Model of a Human Head

The process of material jetting, often also called Inkjet 3D printing, is similar to the 2D Inkjet printing procedure. The print head consists of multiple small nozzles which jet droplets of photopolymers on demand. [2] Each nozzle can extrude a different material, which allows for the creation of multi-material parts. [2] The droplets of material are then immediately cured using a UV light source mounted to the print head. In contrast to the FFF printing process, a layer is not formed by moving the print head along a pre-calculated path, but by scanning the layer line by line. The Statasys J750, for example, allows for full colour prints. The materials supported by the material jetting printing process are similar to the ones of the SLA process and hence share similar properties. [2] Additionally there have been advances in the field of material jetting metals by suspending nano metal particles in a fluid. After the removal of the support material the printed object has to be sintered to create a final metal part. [7]

Binder Jetting

A binder jetting 3D printer uses particles of a fine-grained powder, which are fused together using a binder, to form a three-dimensional object. [2] In principle, it consists out of two separate chambers: One functions as a reservoir for the powdered material, the other one as the printing chamber. To fabricate a layer of an object a blade pushes the material out of the reservoir and spreads it over the printing surface to create a thin layer of powder. A print head similar to the one found in a 2D inkjet printer then applies the binder to the layer to solidify and bind it to the previous one. [2] Although binder jetting does not allow for multi-material support, there exist printers, which feature a second print head to apply pigment to the layer after the binder to allow for full color prints. [2]

Workflow

Designing

Designing a three dimensional object is the first step in the workflow of 3D printing. This design process can be supported by software. Such CAD software is capable of creating, managing and manipulating different 3D geometric figures while giving the user feedback through a graphical interface. [8] Most CAD programs already support the annotation of a geometric figure with a material. The combination of different geometries then forms a single multiple material object. [8] However, not all file formats support the annotation of materials together with the geometry of the object.

Slicing

Slicing is the process of splitting a 3D model into layers to transform them into a sequence of G-Code instructions. [9] These instructions can be processed by a 3D printer to manufacture the corresponding model in either a bottom-up, top-down or even left to right manner. Before generating the instructions, support structures can be added to connect overhanging sections of the model to either the printing surface or other parts of the model. The support structures have to be removed in a post processing step after the print has finished. [9]

The slicing process for multi-material prints differs depending on the hardware used. For FFF based machines, instructions for changing the material have to be added. This comes with multiple computational challenges such as handling two print heads at the same time without them interfering with each other or clearing the melting chamber from the previous material. [10] For SLA based multi-material prints the slicing software has to handle the additional degrees of freedom arising from the possibility of moving the print from one resin tray to the next one. [6] The slicing procedure for material jetting printers involves the generation of multiple bitmap images representing the voxels of the object.

Post-Processing

3D printed objects may need to be post processed before they can be used as a prototype or a finished product. Such post-processing steps may including sanding the surface of the object to make it smoother or painting it to match the colours of the design. Depending on the printing method and the objects geometry, support structures may have to be removed. [9] The use of multi-material 3D printing reduces the amount of post processing needed for the same result, as colours can be printed directly. Furthermore, it is possible to use a water soluble material for printing the support structures, as their removal only involves placing the object into a water bath. [11]

Applications

Food 3D Printing

The rising trend of food 3D printing [12] supports the customisation of shape, colour, flavour, texture and nutrition of different meals. Multi-material 3D printing enables using multiple ingredients like peanut butter, jelly or dough in the printing process, which is essential for the creation of most foods.

Medical Applications

Multi-material 3D printing technology is often used in the production of 3D printed prosthetics. [13] It enables the use of different materials like a soft TPU on the contact points with the body and a stiff carbon fibre material for the corpus of the prosthetics. The prosthetics can therefore be adjusted to suit the varying needs and desires of an individual.

Another medical use case is the generation of artificial tissue structures. [14] The research focuses on creating tissue, that mimics human tissue in terms of feel, elasticity and structure. Such artificial tissues can be used by surgeons to train and learn on realistic models, which is otherwise hard or expensive to achieve. [15]

Current research focuses on 3D printed drug delivery systems [16] to efficiently deploy a medication or vaccine. Through the use of multi-material printing they create biocompatible structures that can interact with the human body on a cellular level.

Physical Properties

The capability of switching between different materials is essential for controlling the physical properties of a 3D printed object. Besides being able to manipulate the strength of an object through micro-structures, the user can switch between harder or softer materials in the printing process to affect the rigidity of the object. Hard and soft material combination is also applied to fabricate biomimetic structure with desired properties. [17] The use of materials of different colour or elasticity can affect the looks and the haptics of the resulting object. Additionally, it is possible to reduce the amount of post-processing needed by choosing a suitable material for the support structures or the outer hull of the part. [18]

Rapid Prototyping

Multi-material 3D printing enables designers to rapidly manufacture and test their prototypes. The use of multiple materials in a single part enables the designer to create functional and visually appealing prototypes. An example of how 3D printing can be included in the design process is automotive design. [19] There, it is necessary to quickly test and verify a prototype to get the design approved for production. The reduced post-processing steps induced by the multi-material 3D printing technology result in a shorter fabrication time. Additionally, multi-material 3D printing reduces the part count of the produced prototypes compared to traditional fabrication methods like milling or molding, because the assembly of multiple parts with different materials is no longer required.

File Formats

There exist multiple file formats to represent three dimensional objects which are suitable for 3D printing. Yet not all of them support the definition of different materials in the same file as the geometry. The table below lists the most common file formats and their capabilities:

An overview of 3D printing file formats
File FormatMode of OperationMulti-Material SupportRemarks
STL raw, unstructured triangulated surfaceNoMulti-material support can be achieved by saving one STL mesh per material, which results in multiple files for the same 3D objects.
OBJ vertices, texture mapping, vertex normals and facesNoMulti-material support can be easily achieved with the companion file format MTL.
3MF vertices and triangles saved as XML YesBacked by the 3MF Consortium as a new standard file format for 3D printing.
VRML vertices and edges, UV-mapped textures YesDesigned particular for the World Wide Web. Predecessor of the X3D file format.
X3D vertices and edges, UV-mapped textures YesFeatures capabilities for including animations.
PLY vertices, faces and otherNoSuccessor of STL with support for colours.

Related Research Articles

<span class="mw-page-title-main">Inkjet printing</span> Type of computer printing

Inkjet printing is a type of computer printing that recreates a digital image by propelling droplets of ink onto paper and plastic substrates. Inkjet printers were the most commonly used type of printer in 2008, and range from small inexpensive consumer models to expensive professional machines. By 2019, laser printers outsold inkjet printers by nearly a 2:1 ratio, 9.6% vs 5.1% of all computer peripherals.

<span class="mw-page-title-main">Stereolithography</span> 3D printing technique

Stereolithography is a form of 3D printing technology used for creating models, prototypes, patterns, and production parts in a layer by layer fashion using photochemical processes by which light causes chemical monomers and oligomers to cross-link together to form polymers. Those polymers then make up the body of a three-dimensional solid. Research in the area had been conducted during the 1970s, but the term was coined by Chuck Hull in 1984 when he applied for a patent on the process, which was granted in 1986. Stereolithography can be used to create prototypes for products in development, medical models, and computer hardware, as well as in many other applications. While stereolithography is fast and can produce almost any design, it can be expensive.

<span class="mw-page-title-main">3D printing</span> Additive process used to make a three-dimensional object

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.

<span class="mw-page-title-main">3D Systems</span> American 3D printing company

3D Systems Corporation is an American company based in Rock Hill, South Carolina, that engineers, manufactures, and sells 3D printers, 3D printing materials, 3D printed parts, and application engineering services. The company creates product concept models, precision and functional prototypes, master patterns for tooling, as well as production parts for direct digital manufacturing. It uses proprietary processes to fabricate physical objects using input from computer-aided design and manufacturing software, or 3D scanning and 3D sculpting devices.

<span class="mw-page-title-main">Solid ink</span> Type of ink used in printing

Solid ink is a type of ink used in printing. Solid ink is a waxy, resin-based polymer that must be melted prior to usage, unlike conventional liquid inks. The technology is used most often in graphics and large-format printing environments where color vividness and cost efficiency are important.

<span class="mw-page-title-main">Rapid prototyping</span> Group of techniques to quickly construct physical objects

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.

<span class="mw-page-title-main">Powder bed and inkjet head 3D printing</span> 3D printing technique

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.

Construction 3D Printing (c3Dp) or 3D construction Printing (3DCP) refers to various technologies that use 3D printing as a core method to fabricate buildings or construction components. Alternative terms for this process include "additive construction." "3D Concrete" refers to concrete extrusion technologies whereas Autonomous Robotic Construction System (ARCS), large-scale additive manufacturing (LSAM), and freeform construction (FC) refer to other sub-groups.

<span class="mw-page-title-main">Fused filament fabrication</span> 3D printing process

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.

<span class="mw-page-title-main">Inkjet technology</span>

Inkjet technology originally was invented for depositing aqueous inks on paper in 'selective' positions based on the ink properties only. Inkjet nozzles and inks were designed together and the inkjet performance was based on a design. It was used as a data recorder in the early 1950s, later in the 1950s co-solvent-based inks in the publishing industry were seen for text and images, then solvent-based inks appeared in industrial marking on specialized surfaces and in the 1990's phase change or hot-melt ink has become a popular with images and digital fabrication of electronic and mechanical devices, especially jewelry. Although the terms "jetting", "inkjet technology" and "inkjet printing", are commonly used interchangeably, inkjet printing usually refers to the publishing industry, used for printing graphical content, while industrial jetting usually refers to general purpose fabrication via material particle deposition.

<span class="mw-page-title-main">DFM analysis for stereolithography</span>

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.

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.

<span class="mw-page-title-main">Applications of 3D printing</span>

In recent years, 3D printing has developed significantly and can now perform crucial roles in many applications, with the most common applications being manufacturing, medicine, architecture, custom art and design, and can vary from fully functional to purely aesthetic applications.

<span class="mw-page-title-main">3D printing processes</span> List of 3D printing processes

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.

Material extrusion-based additive manufacturing (EAM) represents one of the seven categories of 3d printing processes, defined by the ISO international standard 17296-2. While it is mostly used for plastics, under the name of FDM or FFF, it can also be used for metals and ceramics. In this AM process category, the feedstock materials are mixtures of a polymeric binder and a fine grain solid powder of metal or ceramic materials. Similar type of feedstock is also used in the Metal Injection Molding (MIM) and in the Ceramic Injection Molding (CIM) processes. The extruder pushes the material towards a heated nozzle thanks to

3D printing speed measures the amount of manufactured material over a given time period, where the unit of time is measured in Seconds, and the unit of manufactured material is typically measured in units of either kg, mm or cm3, depending on the type of additive manufacturing technique.

<span class="mw-page-title-main">3D food printing</span> 3D printing techniques to make food

3D food printing is the process of manufacturing food products using a variety of additive manufacturing techniques. Most commonly, food grade syringes hold the printing material, which is then deposited through a food grade nozzle layer by layer. The most advanced 3D food printers have pre-loaded recipes on board and also allow the user to remotely design their food on their computers, phones or some IoT device. The food can be customized in shape, color, texture, flavor or nutrition, which makes it very useful in various fields such as space exploration and healthcare.

<span class="mw-page-title-main">3D concrete printing</span> Additive manufacturing process using concrete

3D concrete printing, or simply concrete printing, refers to digital fabrication processes for cementitious materials based on one of several different 3D printing technologies. 3D-printed concrete eliminates the need for formwork, reducing material waste and allowing for greater geometric freedom in complex structures. With recent developments in mix design and 3D printing technology over the last decade, 3D concrete printing has grown exponentially since its emergence in the 1990s. Architectural and structural applications of 3D-printed concrete include the production of building blocks, building modules, street furniture, pedestrian bridges, and low-rise residential structures.

A 3D printed medication is a customized medication created using 3D printing techniques, such as 3D printed tablets. It allows for precise control over the composition and dosage of drugs, enabling the production of personalized medicine tailored to an individual's specific needs, such as age, weight, and medical condition. This approach can be used to improve the effectiveness of drug therapies and to reduce side effects.

<span class="mw-page-title-main">FDM printing file formats</span> Data protocol used in 3D printing

FDM printing is one of the most popular types of 3D printing, it is used throughout different engineering industries and also has a great number of individual users that enjoy 3D-printing as a hobby. FDM printing is so popular because it can produce near finished models of hardware with a very short manufacturing process also known as Rapid prototyping. This kind of printing was first developed and patented in 1989 by Stratasys and has made lots of advancements in the past few decades becoming much cheaper and accessible.

References

  1. ↑ Gibson, Ian; Rosen, David W.; Stucker, Brent (2010), Gibson, Ian; Rosen, David W.; Stucker, Brent (eds.), "Extrusion-Based Systems", Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing, Springer US, pp. 160–186, doi:10.1007/978-1-4419-1120-9_6, ISBN   978-1-4419-1120-9
  2. 1 2 3 4 5 6 7 8 9 10 Gebhardt, Andreas (2011). Understanding Additive Manufacturing. Hanser. ISBN   978-3-446-42552-1.
  3. ↑ "Mosaic Platte 2" . Retrieved 2020-01-31.
  4. ↑ "Original Prusa i3 Multi Material 2.0". Prusa3D - 3D Printers from Josef Průša. Retrieved 2020-01-31.
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  6. 1 2 3 Choi, Jae-Won; Kim, Ho-Chan; Wicker, Ryan (2011-03-01). "Multi-material stereolithography". Journal of Materials Processing Technology. 211 (3): 318–328. doi:10.1016/j.jmatprotec.2010.10.003. ISSN   0924-0136.
  7. ↑ "Technology". Xjet. Retrieved 2020-01-31.
  8. 1 2 SARCAR, M. M. M.; RAO, K. MALLIKARJUNA; NARAYAN, K. LALIT (2008-05-05). Computer Aided Design and Manufacturing. PHI Learning Pvt. Ltd. ISBN   978-81-203-3342-0.
  9. 1 2 3 Evans, Brian (2012), "3D Printer Toolchain", in Evans, Brian (ed.), Practical 3D Printers, Apress, pp. 27–47, doi:10.1007/978-1-4302-4393-9_2, ISBN   978-1-4302-4393-9
  10. ↑ "Get started with Cura: Printing with two colors". ultimaker.com. Retrieved 2020-01-31.
  11. ↑ Ni, Fei; Wang, Guangchun; Zhao, Haibin (2017). "Fabrication of water-soluble poly(vinyl alcohol)-based composites with improved thermal behavior for potential three-dimensional printing application". Journal of Applied Polymer Science. 134 (24). doi:10.1002/app.44966. ISSN   1097-4628.
  12. ↑ Sun, Jie; Peng, Zhuo; Zhou, Weibiao; Fuh, Jerry Y. H.; Hong, Geok Soon; Chiu, Annette (2015-01-01). "A Review on 3D Printing for Customized Food Fabrication". Procedia Manufacturing. 43rd North American Manufacturing Research Conference, NAMRC 43, 8-12 June 2015, UNC Charlotte, North Carolina, United States. 1: 308–319. doi: 10.1016/j.promfg.2015.09.057 . ISSN   2351-9789.
  13. ↑ Mohammed, Mazher Iqbal; Tatineni, Joseph; Cadd, Brenton; Peart, Greg; Gibson, Ian (2017-02-09). "Advanced auricular prosthesis development by 3D modelling and multi-material printing". KnE Engineering. 2 (2): 37. doi: 10.18502/keg.v2i2.593 . ISSN   2518-6841.
  14. ↑ US 10290236,Bernal, Andres,"Method for fabricating simulated tissue structures by means of multi material 3D printing",published 2019-05-14, assigned to Bioniko Consulting LLC
  15. ↑ "Medical Visualization Part 2 of 3: Uses". GarageFarm. 2018-02-08. Retrieved 2018-02-08.
  16. ↑ Gregory, David A.; Zhang, Yu; Smith, Patrick J.; Zhao, Xiubo; Ebbens, Stephen J. (2016). "Reactive Inkjet Printing of Biocompatible Enzyme Powered Silk Micro-Rockets". Small. 12 (30): 4048–4055. doi: 10.1002/smll.201600921 . ISSN   1613-6829. PMID   27345008.
  17. ↑ Islam, Muhammed Kamrul; Hazell, Paul J.; Escobedo, Juan P.; Wang, Hongxu (July 2021). "Biomimetic armour design strategies for additive manufacturing: A review". Materials & Design. 205: 109730. doi: 10.1016/j.matdes.2021.109730 .
  18. ↑ Altenhofen, Christian; Luu, Thu Huong; Grasser, Tim; al, et (2018). "Continuous Property Gradation for Multi-material 3D-printed Objects". Solid Freeform Fabrication 2018: 1675–1685.[ permanent dead link ]
  19. ↑ "How Audi uses full color multi-material 3D printing in automotive design - Make Parts Fast". www.makepartsfast.com. Retrieved 2020-01-29.
  1. 3D Printing Timeline
  2. STL 2.0: A Proposal for a Universal Multi-Material Additive Manufacturing File Format
  3. 3D Printing File Formats
  4. The PLY file format
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