) is a3D printingprocess that uses a continuous filament of athermoplasticmaterial. This is fed from a large coil, through a moving, heated. Molten material is forced out of the print heads nozzle and is deposited on the growing workpiece. The head is moved, under computer control, to define the printed shape. Usually the head moves in layers, moving in two dimensions to deposit one horizontal plane at a time, before moving slightly upwards to begin a new slice. 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.was coined by the members of theRepRapproject to give a phrase that would be legally unconstrained in its use, given patents covering

Fused filament printing is now the most popular process (by number of machines) for hobbyist-grade 3D printing. As other techniques, such a photopolymerisation and powder sintering, may offer better results at greater cost, they still dominate commercial printing.

The3D printer heador3D printer extruderis a part in material extrusion-type printing responsible for raw material melting and forming it into a continuous profile. A wide variety of materials are extruded, including thermoplastics such asacrylonitrile butadiene styrene(ABS),polylactic acid(PLA),high-impact polystyrene(HIPS),thermoplastic polyurethane(TPU),aliphatic polyamides(nylon),[1]and recently alsoPEEK.[2]Paste-like materials such as ceramics and chocolate can be extruded using the fused filament process and a paste extruder.[3]

Additive manufacturing(AM), also referred to as 3D printing involves manufacturing a part by depositing material layer by layer. There is a wide array of different AM technologies that can make a part layer by layer including material extrusion, binder jetting, material jetting and directed energy deposition.[4]

These process have varied types of extruders and extrude different materials to achieve the final product using layer by layer addition of material approach. The3D Printer Liquefieris the component predominantly used in Material extrusion type printing.

Extrusionin 3-D printing using material extrusion involves a cold end and a hot end.

Thecold endis part of an extruder system that pulls and feed the material from thespool, and pushes it towards the hot end. The cold end is mostly gear- or roller-based supplying torque to the material and controlling the feed rate by means of astepper motor. By this means the process rate is controlled.

Thehot endis the active part which also hosts the liquefier of the 3D printer that melts the filament. It allows themolten plasticto exit from the smallnozzleto form a thin and tacky bead of plastic that will adhere to the material it is laid on. the hot end consists of a heating chamber and a nozzle. The hole in the tip (nozzle) has a diameter of between 0.3mm and 1.0mm. Different types of nozzles and heating methods are used depending upon the material to be printed.[5]

Some type of 3-D printing machines can have a different type of extrusion system which may not have a heating chamber- the heat is supplied from another source, e.g. alaser.

The ways extruders are mounted on the rest of the machine have evolved over time into informal mounting standards. These informal standards include:[5]

Such factor standards allows new extruder designs to be tested on existing printer frames, and new printer frame designs to use existing extruders.

In Fused Deposition Modeling a filament

of plastic material is fed through a heated moving head

that melts and extrudes it depositing it, layer after layer, in the desired shape

lowers after each layer is deposited. For this kind of 3D printing technology additional vertical support structures

are needed to sustain overhanging parts

Timelapsevideo of ahyperboloidobject (designed byGeorge W. Hart) made ofPLAusing aRepRapPrusa Mendel 3D printer for molten polymer deposition.

Fused deposition modeling(FDM) is anadditive manufacturing(AM) technology commonly used for modeling, prototyping, and production applications as trademarked byStratasysInc.[6][7]. It is one of the techniques used for3D printing. FDM works on an additive principle by laying down material in layers; a plastic filament or metal wire is unwound from a coil and supplies material to produce a part. Thus, FDM is also known as a solid-based AM technology.[8]

Fused deposition modeling (FDM) was developed byS. Scott Crumpin the late 1980s and was commercialized in 1990 byStratasys.[9][10]With the expiration of the patentUS 5121329 Aon this technology there is now a large open-source development community (calledRepRap), as well as commercial andDIYvariants, which utilize this type of 3D printer. This has led to two orders of magnitude price drop since this technologys creation.[11]

FDM begins with a software process which processes anSTL file (STereoLithography file format), mathematically slicing and orienting the model for the build process. If required, support structures may be generated.[12]The machine may dispense multiple materials to achieve different goals:

1. One may use one material to build up the model.

2. Use another as a soluble support structure.[13]

3. One could use multiple colors of the same type of thermoplastic on the same model.

The model or part is produced byextrudingsmall flattened strings of molten material to form layers as the material hardens immediately after extrusion from the nozzle.

A plastic filament is unwound from a coil and supplies material to anextrusion nozzlewhich can turn the flow on and off. There is typically an accurately controlled drive that pushes the filament into the nozzle.

The nozzle is heated to melt the material. The thermoplastics are heated well past theirglass transitiontemperature and are then deposited by an extrusion head.

The nozzle can be moved in both horizontal and vertical directions by a numerically controlled mechanism. The nozzle follows a tool-path controlled by acomputer-aided manufacturing(CAM) software package, and the part is built from the bottom up, one layer at a time.Stepper motorsorservo motorsare typically employed to move the extrusion head. The mechanism used is often an X-Y-Z rectilinear design, although other mechanical designs such asdeltabothave been employed.

Although as a printing technology FDM is very flexible, and it is capable of dealing with small overhangs by the support from lower layers, FDM generally has some restrictions on the slope of the overhang, and cannot produce unsupportedstalactites.

Myriad materials are available, such asAcrylonitrile Butadiene Styrene(ABS),Polylactic acid(PLA),Polycarbonate(PC),Polyamide(PA),Polystyrene(PS),ligninrubber, among many others, with different trade-offs between strength and temperature properties. In addition, even the color of a giventhermoplasticmaterial may affect the strength of the printed object.[14]Recently a German company demonstrated for the first time the technical possibility of processing granularPEEKinto filament form and 3D printing parts from the filament material using FDM-technology.[2]

During FDM, the hot molten polymer is exposed to air. Operating the FDM process within aninert gasatmosphere such asnitrogenorargoncan significantly increase the layer adhesion and leads to improved mechanical properties of the 3D printed objects.[15]An inert gas is routinely used to prevent oxidation duringselective laser sintering.

Flow geometry of the extruder, heating method and the melt flow behavior of a non-Newtonian fluid are of main consideration in the part.

A plastic filament is supplied from a reel, either commercially available or home made, and fed into a heated liquefier where it is melted. This melt is then extruded by a nozzle while the incoming filament, still in solid phase, acts as a plunger.

The nozzle is mounted to a mechanical stage, which can be moved in thexyplane. As the nozzle is moved over the table in a prescribed geometry, it deposits a thin bead of extruded plastic, called a road which solidifies quickly upon contact with substrate and/or roads deposited earlier.[16]

Solid layers are generated by following a rasterizing motion where the roads are deposited side by side within an enveloping domain boundary.

Once a layer is completed, the platform is lowered in thez directionin order to start the next layer. This process continues until the fabrication of the object is completed.

For Successful bonding of the roads in the process control of the thermal environment is necessary. Therefore, the system is kept inside a chamber, maintained at a temperature just below the melting point of the material being deposited.

During extrusion thethermoplastic filamentis introduced by mechanical pressure from rollers, into the liquefier, where it melts and is then extruded. The rollers are the only drive mechanism in the material delivery system, therefore filament is under tensile stress upstream to the roller and under compression at the downstream side acting as a plunger. Therefore, compressive stress is the driving force behind the extrusion process.

The force required to extrude the melt must be sufficient to overcome the pressure drop across the system, which strictly depends on the viscous properties of the melted material and the flow geometry of the liquefier and nozzle. The melted material is subjected to shear deformation during the flow.Shear thinningbehavior is observed in most of the materials used in this type of 3-D printing. This is modeled using power law for generalized Newtonian fluids.

The temperature is regulated by heat input from electrical coil heaters. The system continuously adjusts the power supplied to the coils according to the temperature difference between the desired value and the value detected by the thermocouple, forming aNegative Feedbackloop. This is similar to Heat Flow rate in Cylindrical Pipe.

FDM, a prominent form ofrapid prototyping, is used for prototyping and rapid manufacturing. Rapid prototyping facilitates iterative testing, and for very short runs, rapid manufacturing can be a relatively inexpensive alternative.[17]

FDM uses thethermoplasticsPLA, ABS, ABSi,polyphenylsulfone(PPSF),polycarbonate(PC), PETG andUltem9085, and among others.[18]These materials are used for their heat resistance properties. Ultem 9085 also exhibits fire retardancy making it suitable for aerospace and aviation applications.

FDM is also used in prototyping scaffolds for medical tissue engineering applications.[19]

Modified Groove Mount, Round Mount, Heatsink

Wood, ABS, Nylon, PLA and PET Materials

Wood, ABS, Nylon, PLA and PET Materials

Direct (Bowden with printed adapter)

PTFE Holder, PTFE Liner, Stainless Steel Barel, Aluminum Heater Block, Brass Nozzle

Direct (Bowden with printed adapter)

Direct (Bowden with printed adapter)

Groove Mount, Groove Mount for Bowden, Flat Plate

Several projects and companies are making efforts to develop affordable 3D printers for home desktop use. Much of this work has been driven by and targeted atDIY/enthusiast/early adoptercommunities, with additional ties to the academic andhackercommunities.[22]

RepRapis one of the longest running projects in the desktop category. The RepRap project aims to produce afree and open source hardware(FOSH) 3D printer, whose full specifications are released under theGNU General Public License, and which is capable of replicating itself by printing many of its own (plastic) parts to create more machines.[23][24]RepRaps have already been shown to be able to printcircuit boards[25]and metal parts.[26][27]

otheropensource hardwareproject forDIY3D printers.

Because of the FOSH aims ofRepRap, many related projects have used their design for inspiration, creating an ecosystem of related or derivative 3D printers, most of which are also open source designs. The availability of these open source designs means that variants of 3D printers are easy to invent. The quality and complexity of printer designs, however, as well as the quality of kit or finished products, varies greatly from project to project. This rapid development of open source 3D printers is gaining interest in many spheres as it enables hyper-customization and the use ofpublic domaindesigns to fabricateopen source appropriate technology. This technology can also assist initiatives insustainable developmentsince technologies are easily and economically made from resources available to local communities.[28][29]

The cost of 3D printers has decreased dramatically since about 2010, with machines that used to cost $20,000 now costing less than $1,000.[30]For instance, as of 2017, several companies and individuals are selling parts to build variousRepRapdesigns, with prices starting at aboutGB99/US$100[31][32]. The best selling desktop FDM printer[33],Prusa i3 MK2, costsUS$900assembled orUS$600for self-assembly kit[34].

The open [35]has developed printers for general use with anything that can be squirted through a nozzle, from chocolate to silicone sealant and chemical reactants. Printers following the projects designs have been available from suppliers in kits or in pre-assembled form since 2012 at prices in the US$2000 range.

TheLulzBot3D printers manufactured byAleph Objectsare another example of an open-source application of fused deposition modeling technology. The flagship model in the LulzBot line, the TAZ printer takes inspiration for its design from the RepRap Mendel90 andPrusa i3models. The LulzBot 3D printer is currently the only printer on the market to have received the Respects Your Freedom certification from theFree Software Foundation.[36]

Customer-driven product customization and demand for cost and time savings has increased interest in agility of manufacturing process. This has led to improvements in RP technologies and in particularly ofFused Deposition Modeling.[16]The Development of Extruders is going rapidly because of open source 3-D printer movement caused by products like RepRap. Consistent improvements are seen in the form of increased heating temperature of liquefier, the over-all control and precision of the process and improved support for wide variety of materials to print, including ceramics.

The ways extruders are mounted on the machine has also evolved over time into informal mounting standards. These informal standards include the Vertical X Axis Standard, the Quick-fit extruder mount, the OpenX mount, etc.

The majority of fused filament printers follow the same basic design. A flat bed is used as the starting point for the print workpiece. A gantry above this carries the moving print head. The gantry design is optimised for movement mostly in the horizontal X & Y directions, with a slow climb in the Z direction as the piece is printed.Stepper motorsdrive the movement through eitherleadscrewsortoothed beltdrives. It is common, owing to the differences in movement speed, to use toothed belts for the X,Y drives and a leadscrew for Z. Some machines also have X axis movement on the gantry, but move the bed (and print job) for Y. As, unlikelaser cutters, head movement speeds are low, stepper motors are universally used and there is no need to useservomotorsinstead.

Many printers, originally those influenced by theRepRapproject, make extensive use of 3D printed components in their own construction. These are typically printed connector blocks with a variety of angled holes, joined by cheap steelthreaded rod. This makes a construction that is cheap and easy to assemble, easily allows non-perpendicular framing joints, but does require access to a 3D printer. The notion ofbootstrapping3D printers like this has been something of a dogmatic theme within the RepRap designs. The lack of stiffness in the rod also requires eithertriangulation, or gives the risk of a gantry structure that flexes and vibrates in service, reducing print quality.

Many machines now use box-like semi-enclosed frames of either laser-cut plywood, plastic or pressed steel sheet. These are cheap, rigid and can also be used as the basis for an enclosed print volume, allowing temperature control within it to control warping of the print job.

A handful of machines use polar coordinates instead, usually machines optimised to print objects with circular symmetry. These have a radial gantry movement and a rotating bed. Although there are some potential mechanical advantages to this design for printing hollow cylinders, their different geometry and the resulting non-mainstream approach to print planning still keeps them from being popular as yet. Although it is an easy task for a robotsmotion planningto convert from Cartesian to polar coordinates, gaining any advantage from this design also requires the print slicing algorithms to be aware of the rotational symmetry from the outset.

A different approach is taken with Rostock pattern printers, based on adelta robotmechanism.[37]These have a large open print volume with a three-armed delta robot mounted at the top. This design of robot is noted for its low inertia and ability for fast movement over a large volume. Stability and freedom from vibration when moving a heavy print head on the end of spindly arms is a technical challenge though. This design has mostly been favoured as a means of gaining a large print volume without a large and heavy gantry.

As the print head moves the distance of its filament from storage coil to head also changes. This tugging on the filament is another technical challenge to overcome, if it is not to affect print quality.

RepRap Wiki Category:Thermoplastics

Universal Paste extruder Ceramic, Food and Real Chocolate 3D Printing

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