Changes

#Position: Position refers to the distance separating a feature and an (ideally) meaningful reference (i.e.: the distance between a hole and the side of a part, or between two holes). Thankfully, flaws pertaining to position are rare on a properly tuned printer, as the printer does not have any information about existing references other than the build plate. If tuned properly, the printer will always print a feature at a position (X,Y,Z) distance relative to another feature, because that is what the gCode will tell it to do. You can imagine, however, that if the part is warped, the 'build plate reference' is no longer valid, and such, warped parts almost always have features out of position ''<u>unless the meaningful reference (interfacing feature) used in the design is not the build plate</u>''. However, since the build plate reference is such an important one to define the Z position of features (for the printer, that is), making your meaningful reference something other than the build plate does not always guarantee you good positional tolerance independent of warping.

#Position: Position refers to the distance separating a feature and an (ideally) meaningful reference (i.e.: the distance between a hole and the side of a part, or between two holes). Thankfully, flaws pertaining to position are rare on a properly tuned printer, as the printer does not have any information about existing references other than the build plate. If tuned properly, the printer will always print a feature at a position (X,Y,Z) distance relative to another feature, because that is what the gCode will tell it to do. You can imagine, however, that if the part is warped, the 'build plate reference' is no longer valid, and such, warped parts almost always have features out of position ''<u>unless the meaningful reference (interfacing feature) used in the design is not the build plate</u>''. However, since the build plate reference is such an important one to define the Z position of features (for the printer, that is), making your meaningful reference something other than the build plate does not always guarantee you good positional tolerance independent of warping.

#Surface: The surface finish of a part is a rather complex subject. In 3D printing, and for typical applications of 3D printed parts, it mostly refers to the mean (statistical) difference between the height of cusps and valleys on a part and their deviation from that mean, at a macroscopic level. The most important consideration is that when 3D printing, most surface finishes are quite rough (deviate significantly from the mean), and thus are sanded down considerably to knock out the cusps left by the printer. This post processing can negatively affect the form of the final part.

#Surface: The surface finish of a part is a rather complex subject. In 3D printing, and for typical applications of 3D printed parts, it mostly refers to the mean (statistical) difference between the height of cusps and valleys on a part and their deviation from that mean, at a macroscopic level. The most important consideration is that when 3D printing, most surface finishes are quite rough (deviate significantly from the mean), and thus are sanded down considerably to knock out the cusps left by the printer. This post processing can negatively affect the form of the final part.

Note that ''<u>a proper mechanical fit between components demands a good tolerance on form, feature position, and surface finish</u>'', such that it is typically impossible to obtain a proper fit when 3D printing, and that if you are considering the 3D printing of critically interfacing components, 3D printing should not be used unless post processing <u>''is built into the design''</u>. For mechanical designs, you will notice that a main application is brackets. This is because brackets only need good positional tolerance on holes and mating faces, which 3D printing can almost always provide (the tolerance on form for holes is not that important since they are typically clearance holes). However, since some brackets are easily laser cut, 3D printing brackets is only done under certain specific conditions. It certainly has shown its commercial use in cost cutting by replacing intricate multi-part assemblies by ''generatively designed'' (we'll say computer generated for now) parts, as shown in the picture below.

Note that ''<u>a proper mechanical fit between components demands a good tolerance on form, feature position, and surface finish</u>'', such that it is typically impossible to obtain a proper fit when 3D printing, and that if you are considering the 3D printing of critically interfacing components, 3D printing should not be used unless post processing <u>''is built into the design''</u>. For mechanical designs, you will notice that a main application is brackets. This is because brackets only need good positional tolerance on holes and mating faces, which 3D printing can almost always provide (the tolerance on form for holes is not that important since they are typically clearance holes). However, since some brackets are easily laser cut, 3D printing brackets is only done under certain specific conditions. It certainly has shown its commercial use in cost cutting by replacing intricate multi-part assemblies by ''generatively designed'' (we'll say computer generated for now) parts, as shown in the picture below.

===Supports===

===Supports===

As explained in the 3D printing page, supports are sometimes required to support overhanging sections of a print. Due to the downsides of supports discussed below, it is typically better to avoid supports altogether when designing for 3D printing.

As explained in the 3D printing page, supports are sometimes required to support overhanging sections of a print. Due to the downsides of supports discussed below, it is typically better to avoid supports altogether when designing for 3D printing.