At the moment, my main reason for learning Blender is for 3D printing. My 3D printer is on pre-order, so in the meantime I’m looking into various programs that can be used as part of the 3D printing workflow. I haven’t settled on any specific applications, yet. Also, without actually having a 3D printer to play with, I can’t be 100% confident with some of my notes below. I’m sure once I gain experience after many prints, I’ll have a better idea of what needs to be considered/executed during the export checklist.
Does the model have an appropriate origin?
From what I can tell, the majority of 3D printers and slicer applications consider Z to be the “up axis”. Consider Z=0 to be the printer bed. Blender models should sit on the XY-plane where Z=0. Also, (X,Y)=(0,0) is typically the center of the printer bed. Also, based on anecdotal evidence, it seems that the popular printing site Shapeways uses the Y-axis for up.
##Are the meshes grouped appropriately?
I need to do more research on this later, but it seems for 3D printing, all objects should be joined (I’m not sure if this is the correct term within the context of Blender as it applies to 3D printing.) Some sites also discuss the creation of meshes, and simplifying meshes, especially ones created from overlapping objects. There’s also a lot of talk about “manifold” meshes, which seems to refer to “water tightness” of objects (i.e. objects with possible missing faces.) I think this is content that will become more clear as I progress with Blender and experiment with prints.
##Is the model closed? How about the base?
I guess for 3D printing, this depends on the desired end result. If you want a printed pyramid to have no base, then omit it. It may not make sense to waste filament printing a base if you plan on gluing it into a diorama, for example.
##What axis is up? How about “handedness”?
and
Does the scale set in Blender come through?
The STL file generated by Blender does not contain “Scale” data. It only contains “Dimension” data. You can confirm this by exporting an object with scale data such as (0.5, 0.49, 0.22) to an STL file then starting a new Blender project by importing the STL file. You will see the scale for the object is (1, 1, 1). The “Dimension” data will be the same as the original Blender project.
STL files do not specify the unit of measurement for dimensions. That is, looking at an STL file, you will not know if the dimensions for the object are in millimeters, inches, cubits, etc. What is important is how printing software interprets these dimensions. The slicer software that loads an STL file and converts it into commands to be sent to a 3D printer makes assumptions about what 1 unit of distance in an STL file is in real life. One application may assume a 1x1x1-unit cube defined in an STL file should be printed as a 1x1x1-inch cube, and another will print the same STL file as a 1x1x1-cm cube.
There’s a number of different slicer programs. The three I’m currently looking at are Slic3r, Cura, and Simplify3D. All three of these applications assume STL units are in millimeters. So 1 unit in an STL file will translate to 1 millimeter printed. Slice3r and Simplify3D both use a right-handed coordinate system. I’m having difficulty confirming the coordinate system used by Cura. Pictures I’ve seen of the Cura UI seem to indicate both are used, so perhaps it’s configurable.
Often people will use a program such as Netfabb after exporting an STL file (but before opening it in a slicer) to repair any issues with the STL that could cause difficulties when 3D printing. Based on what I’ve seen, Netfabb uses a right-handed coordinate system.