Wednesday, 7 October 2015

Another 3D Printing glossary

In writing this glossary I looked through quite a few 3D printing glossaries. Below is a list of words that are or could be commonly used in the world of 3D printing without being specific to any particular print process. I hope that this does not over or under complicate things. 

3D Printing - see Rapid Prototyping 

Additive Manufacturing - see 3D Printing (in fact this usually refers to more industrial applications of 3D printing)

Auto-fix - this is short hand for "I'm naive and I don't mind surprising results!". Always be wary of anything offering to auto-fix your file and if you do see Diffing Tool.

Build Time - Depending on many factors this is how long it take to build a part in the printer. This is not the same as the total time needed to prepare the file and the printer, print the part, post-process the part, package and deliver. 

Diffing Tool - usually a software tool for comparing two pieces of text much loved by programmers for finding bugs. If you carry out a fixing procedure on the whole model it pays to step backwards and forwards to spot unexpected differences between before and after model states.

Error - this is what frequently happens if you do not look after your 3D printer properly or if your printers have just done too much hard work and something eventually breaks.

Faceting - When the triangulation of the print file is visible in the surface of the printed part.

Feature Size - the smallest features that can be physically printed. This can easily become an obsession. Often better to ask at what size a feature becomes clearly visible. There is always a big difference between the minimum size of structural elements and surface relief details.

File Size - There is an optimum level where mesh size is just right for the resolution of the printer. As triangles get increasingly small, files getting increasingly large and time is increasingly wasted. Files for 3D printing rarely need to be more than 20MB.

Hole - gaps in meshes used to define 3D prints. In the same way that holes in skin are bad for you, holes in meshes are bad for 3D prints too.

Layer - almost all 3D prints are created one layer at a time. Layering is often visible on the side walls of a print. Finer layer thickness is often desirable as layering is less evident visually.

Manifold - "in mathematics, a manifold is a topological space that resembles Euclidean space near each point. More precisely, each point of an n-dimensional manifold has a neighbourhood that is homeomorphic to the Euclidean space of dimension n". In 3D printing it means a mesh without holes - sometimes known as watertight.

Meshing - the process of converting a vector or NURBS model (the design file) to a triangulated mesh or shell used for 3D printing.

Normal - surface or triangle direction defining inside from outside of the model.

Post-processing -  This is the part that the manufacturers and resellers keep quite about. Up until this point it all looks pretty straightforward - then the work begins... 3D printing is not vending and alas is nothing like Star Trek's replicators.

Rapid Prototyping - until recently, rapid prototyping was the term used to describe what has come to be known as 3D printing - or additive manufacturing.

Shrinkwrap - often a last resort when fixing a hideously bad file quickly, the shrinkwrap tool in Materialise's famous Magics software really is magic. And like all good magic the shrinkwrap is most powerful when you can't tell its been used.

Support - parts with overhangs need to be supported as they are printed. Powder based systems are self-supporting whereas other printers need to print a support. Removing supports is usually no fun at all.

STL - the stereolithography file format was created so that people could print to the very first commercial 3D printers. It contains triangle coordinates and normal directions but does not contain unit, colour or indeed any other information.

Texture - in colour 3D printing this refers to an image file mapped on to the surface of the mesh containing colour information to be printed. Not to be confused with physical surface texture. Remember you need a colour 3D printer to print image textures.

Watertight - a manifold shell - i.e a part with no holes.

XYZ - cartesian coordinate system used to locate points in (Euclidian) space. Z usually denotes height in 3D printing but this is not always the case with software modellers.

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