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General principles for 3D printing

Release time:2018-08-10

Modeling[edit]

 
CAD model used for 3D printing
 
3D models are generated from 2D pictures taken at the Fantasitron 3D photo booth at Madurodam

3D printable models may be created with a computer-aided design (CAD) package, via a 3D scanner, or by a plain digital camera and photogrammetry software. 3D printed models created with CAD result in reduced errors and can be corrected before printing, allowing verification in the design of the object before it is printed.[26] The manual modeling process of preparing geometric data for 3D computer graphics is similar to plastic arts such as sculpting. 3D scanning is a process of collecting digital data on the shape and appearance of a real object, creating a digital model based on it.

Printing[edit]

 
Timelapse video of a hyperboloid object (designed by George W. Hart) made of PLA using a RepRap "Prusa Mendel" 3D printer for molten polymer deposition

Before printing a 3D model from an STL file, it must first be examined for errors. Most CAD applications produce errors in output STL files,[27][28] of the following types:

  1. holes;
  2. faces normals;
  3. self-intersections;
  4. noise shells;
  5. manifold errors.[29]

A step in the STL generation known as "repair" fixes such problems in the original model.[30][31] Generally STLs that have been produced from a model obtained through 3D scanning often have more of these errors.[32] This is due to how 3D scanning works-as it is often by point to point acquisition, reconstruction will include errors in most cases.[33]

Once completed, the STL file needs to be processed by a piece of software called a "slicer," which converts the model into a series of thin layers and produces a G-code file containing instructions tailored to a specific type of 3D printer (FDM printers).[citation needed] This G-code file can then be printed with 3D printing client software (which loads the G-code, and uses it to instruct the 3D printer during the 3D printing process).

Printer resolution describes layer thickness and X–Y resolution in dots per inch (dpi) or micrometers (µm). Typical layer thickness is around 100 μm (250 DPI), although some machines can print layers as thin as 16 μm (1,600 DPI).[34] X–Y resolution is comparable to that of laser printers. The particles (3D dots) are around 50 to 100 μm (510 to 250 DPI) in diameter.[citation needed] For that printer resolution, specifying a mesh resolution of 0.01–0.03 mm and a chord length ≤ 0.016 mm generate an optimal STL output file for a given model input file.[35] Specifying higher resolution results in larger files without increase in print quality.

Construction of a model with contemporary methods can take anywhere from several hours to several days, depending on the method used and the size and complexity of the model. Additive systems can typically reduce this time to a few hours, although it varies widely depending on the type of machine used and the size and number of models being produced simultaneously.[36]

Traditional techniques like injection moulding can be less expensive for manufacturing polymer products in high quantities, but additive manufacturing can be faster, more flexible and less expensive when producing relatively small quantities of parts. 3D printers give designers and concept development teams the ability to produce parts and concept models using a desktop size printer.[37]

Seemingly paradoxic, more complex objects can be cheaper for 3D printing production than less complex objects.[citation needed]