3D Genius

Jargon buster

3D printing, like any complex activity, is awash with buzzwords, technical terms and impenetrable jargon. This ongoing guide should help you to navigate through the 3D keyword minefield.

 

3D scanner

Any of several processes whereby photographic processes are used to capture a 3D model from a solid object. 3D scanners are currently expensive, and require a lot of manual input to clean up scans before they’re fit for printing.

ABS

Acrylonitrile butadiene styrene is a polymer used as the extrudable filament in many 3D printers. It has a relatively high melting point compared to PLA, and is an oil-based material – it takes about 2kg of petroleum to make 1kg of ABS. It’s a strong and very resilient material, often used in conventional manufacturing for children’s toys: both Lego and Playmobil are made of ABS.

Additive manufacturing

The term used to describe any process (such as FDM and SLS) whereby a 3D model is build up in stages. It’s differentiated from ‘machining’ approaches, in which a solid material such as wood or plastic is carved and drilled to create the finished model.

Arduino

An open-source microcontroller named after an Italian historical character. Many 3D printers use an Arduino unit with an attached SD card reader, so that printers can produce standalone models without having to be tethered to a computer.

Bed

The base of a 3D printer using the FDM process. While the print head moves from side to side in the X and Y axes, the bed will step down in the Z axis as each layer is complete, ready for printing the next layer.

Blender

A free 3D modeling application published as open source software. Blender is notoriously hard to learn, but is capable of good results.

Bowden cable

The Bowden cable was invented in 1896 by Sir Frank Bowden, the founder of the Raleigh bicycle company, as a way to transmit the pulling power of a bicycle brake lever to the brake mounted on the wheel. In 3D printing terms, the Bowden cable is the plastic tube which feeds the filament from its reel to the hot end.

Build envelope

The maximum physical size of print that can be produced by a specific 3D printer. Build envelopes vary greatly, and are an important consideration when choosing a 3D printer.

CAD

Computer Aided Design is the catch-all term for the use of a computer system to produce 2D or 3D models. CAD is not a file format in itself; CAD programs all output 3D files in a variety of commonly-used formats, including OBJ and STL.

CNC

Computer Numerical Control is the term for an automated machine that interprets CAD programs in order to cut a variety of materials into specific shapes. Plywood, acrylic and other materials can be cut using CNC machines.

Cura

Cura is a 3D print preparation application optimised for the Ultimaker printer, but which can also be used with other RepRap machines. Available for Windows, Mac OS and Linux, it’s a free application that performs slicing operations with a high degree of user control.

Extruder

The part of a 3D printer that pushes the filament through the Bowden cable to the hot end. This usually takes the form of a knurled, rough-textured roller that grips the filament as it guides it through the cable.

FDM

Fused Deposition Modeling is the term used to describe a form of additive manufacturing in which plastic filament is melted and squirted onto a movable bed. This is the most common technology employed by home 3D printers. Both the full name and its acronym are the intellectual property of Stratasys Inc, which has led to many people instead using the term FFF (Fused Filament Fabrication).

FFF

Fused Filament Fabrication is a term coined by those working on the RepRap project as an open-source alternative to the trademarked FDM (see above). The two terms both refer to identical technologies.

Filament

3D printers that use the Fused Deposition Modeling process operate by melting a plastic filament, which is typically made of either ABS or PLA. The filament is available in a range of colours, and is supplied on reels of half a kilogram or more.

Fill

The interior structure of a 3D printed model. Rather than printing a model composed of solid filament, which is both time-consuming and wasteful of material, it’s common practice to print the unseen interior as a mesh of a specified density instead. A fill density of 20%, for example, will add tremendous strength while consuming far less material.

G-code

G-code is the file format used to store information that can be interpreted by CNC machines and 3D printers. It addresses every aspect of a 3D object’s manufacturing process, from the thickness of the layers to the printing temperature. A G-code file contains all the instructions needed to allow a 3D printer to build the finished object.

Hot end

The final stage in the printing process, the hot end is a metal block that’s heated to the temperature required to melt the filament for FDM printing. The hot end starts in contact with the printer bed, so that the first layer of filament is forced into the bed to ensure good adhesion.

LOM

Laminated Object Manufacturing is a rapid prototyping process in which thin layers of adhesive material are cut to shape and then glued together. Despite its low material costs, LOM has yet to gain traction as a serious 3d printing technology.

Mesh

The surface of a 3D object when defined as a computer model. Typically, a curved shape will be redefined as a series of flat triangles: the smaller the triangles, the finer the printed result.

Micron

A micron (or micrometre) is the term for one millionth of a metre, which is one thousandth of a millimetre (equivalent to roughly 0.000039 inches). Good 3D printers can print at a resolution of as little as 40 microns. For comparison, a human hair is typically 90 microns in diameter.

Netfabb

A commercial 3D print preparation application, Netfabb is able to prepare, repair and slice 3D models in preparation for printing. The full version is Netfabb Studio, but Netfabb Engines are cut-down versions customised specifically for individual 3D printer models. See www.netfabb.com.

OBJ

OBJ is a 3D object file format that was developed by Wavefront Technologies in the early 1990s. Most 3D software is able to export OBJ files, and some 3D printing programs (such as Netfabb and Meshlab) can read objects created in this format.

PLA

Polylactic Acid is a form of polyester used as the extrudable filament in some 3D printers. Made from a variety of natural sugar sources, such as corn starch or sugar cane, it melts at a lower temperature than ABS and is biodegradable.

Raft

A latticework platform that supports the object being printed. Some 3D printers require a raft to enable the model to be held securely; others need a raft only if the object has limited points of contact with the bed, such as the legs of a table.

Rapid prototyping

The process of creating a one-off solid representation of a 3D design prior to commencing the manufacturing process. Before the rise of cheap 3D printers, rapid prototyping was an expensive and time-consuming business.

RepRap

RepRap stands for Replicating Rapid Prototyper, and is an open source collaborative project intended to devise a 3D printer that’s capable of printing many of its own constituent parts. The goal is to allow communities to create their own 3D printers without having to invest in expensive equipment. Four RepRap models have been released to date.

Retraction

The process of pulling the filament back from the hot end during printing. If printing a single unit object such as a cup, no retraction is necessary; but if printing a complex object such as a hand, retraction is needed to prevent the molten filament from forming strings between the fingers.

Skinning

The smaller the layer height used to print a 3D model, the finer the model – but the longer the print will take. 3D preparation software allows the outer skin to be printed at double resolution (in other words, half the layer height) to give the model a smoother final appearance.

Sketchup

Previously published by Google, Trimble Sketchup is a free, easy-to-use 3D modeling application. Although designed as an architectural tool, many designers use Sketchup to create printable 3D designs.

Skirt

Before printing a model, some G-code programs instruct the printer to first print a thin bounding line a short distance from the object’s edges. This forms the dual function of ensuring that the object will fit on the print bed, and initiating the extrusion process so that the filament flows smoothly.

SLA

Stereolithography is a process devised in 1986 whereby solid objects are built up by focusing a beam of ultraviolet light onto a basin of liquid polymer. The process is used mainly for rapid prototyping, as it’s ideal for the preparation of complex models. A Kickstarter project, Formlabs, aims to market an affordable home SLA printer, but has run into legal patent infringement problems.

Slicing

The process by which a 3D model (usually in STL format) is turned into a G-code file that can then be interpreted by a 3D printer. Slicing involves defining the object as a sequential series of layers, printed from the bottom up. The thinner the layers, the finer the resulting print.

SLS

Selective Laser Sintering is a method of 3D printing whereby a bath of plastic powder is subjected to a high power laser, which fuses the powder together to form a solid object. When printing is finished, the remaining powder is blown away and can be reused. Unlike FDM, the SLS process can produce very complex objects; but SLS printers are typically very much more expensive than FDM machines.

Stepping motor

A motor capable of very precise small movements, as opposed to the high-speed spinning produced by regular motors. Stepping motors are used to control the position of the print head on each of the X and Y axes, while a third stepping motor shuffles the bed down along the Z axis after each layer is printed; a fourth stepping motor is used to push the filament through the Bowden cable.

STL

Short for stereolithography, STL is a file format used to describe 3D models. It differs from formats such as OBJ in that it specifies the surface of the model only, but not the colour or texture. STL is the most common format used when exchanging and publishing 3D models suitable for printing. All CAD applications can export STL files, but design programs such as Photoshop and Poser cannot; instead, they export OBJ files that need to be converted to STL format.

Support material

FDM printers print layer after layer, from the bottom up. Since they’re unable to print on thin air, any parts with serious overhanging elements need to be supported by additional material, which is then trimmed away after the print is finished. Some preparatory software is able to calculate and define this support material automatically, and to insert it as part of the resulting G-code.

Thingiverse

A community website owned by Makerbot Industries, thingiverse is a site where designers can upload 3D models in the form of STL files. Other users can then download and print these files, which are often modified and republished with improvement and enhancements.

X, Y, Z axes

Taken from traditional geometry, the X and Y axes (devised by Rene Descartes in 1637) are the forward/backward, left/right motion of the 3D print head as it prints each layer in two-dimensional space. The Z-axis is the vertical component, controlled by a stepper motor that jogs the print bed down when each layer has been printed.

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