3D printing is redefining the way we approach design and engineering. The ability to build multiple bodies, layer by layer, doesn’t hold us to the confines of spacial limitations or physics. For the ship in the bottle example above, we can take the approach of building the bottle around our ships, instead of worrying about how to fit the ship through the bottleneck. But now comes the question of how do we make the ship its own part inside our bottle? How is both the clear bottle and black ship produced in a single print job? That’s where the art of producing multibody STL’s for 3D printing comes into play.

stl files

Stage 1: Part Creation

stratasys stratasys


For this example, I will be working with a single part that has letters placed inside a block.  In order to create separate bodies I first extruded cut out my word and then reuse the sketch to extrude the new letter bodies into the same space (making sure ‘Merge result” is turned off).

This means I have no gaps that need to be filled by support material nor do I have any overlapping bodies. I’ll also add some appearances to my main block and letters to better see what is going on internal to my part. Notice that I have 8 Solid Bodies in my part: 1 for the block and 7 for the letters.

Stage 2: Save Bodies Command

save command

I now have the geometry that I’d like to print out. In order to print my 3D design, I need to generate an STL file type to send to the printer processing software (Objet Studio for this project). If I just try to save it out as is, I only get a single file that will be printed out as a solid, single material block, which is not our desired outcome.

stl stl


What I’m looking for is each of my 8 Solid Bodies to have an associated STL file. To do that I need to save each body out individually using the Save Bodies command.  You can use the “Auto-assign Names” feature to quickly name these objects or you can save each body as a descriptive name. The key feature that needs a descriptive name is the block that will be printed in clear. This name gives the printer tech the information he needs to process this body using the Vera Clear material. The last step in this stage is to Create an Assembly with the body files. The Create Assembly option in the Save Bodies side panel allows me to create and save a new assembly. I’ll create our STLs from this assembly in the next stage.

Stage 3: Saving Out STL Files

saving stl

I’m now done with my part file and I will finish up using the assembly file I just created. By reapplying my appearance settings, I can verify that my part is the same, with the exception that the 3 features from my original part have become 8 parts in an assembly.

stl stl


I’m now ready to save my assembly as STL files. I accomplish this by doing a File -> Save As and changing the “Save as type” to STL (*.stl) and selecting the Options button. This opens up the Export Options window where I can edit my resolution in terms of deviation and angle between the triangles which generate the printed part. There is an important check box in this options menu that needs to be unchecked to create a multi-material printed part, and that is the “Save all components of an assembly in a single file.” If this is turned on, I lose the ability to pick bodies to apply different materials to in the printing processing phase. This time, my STL preview shows me that my number of files being saved is 8, unlike when there was just a single file before.

Stage 4: Print Processing

print processing print processing


I can now send these 8 STL files to our printer machine to do some pre-processing of the files. Objet Studio allows me access to apply different material variations to specific bodies, as well as orienting my example block in the machine. When I first bring my STL files into Objet Studio, I need to make sure that the Assembly check box is turned on, since this gives me access to edit the individual parts.  I can then select the materials for the different parts.  For the main clear box, I’ve selected VeraClear and for the letters I’ve chosen the FLX9050 version of TangoBlack.


Once I’m happy with my selections I hit the “Build” button in the command manager of Objet Studio and let the printer do the rest of the work! Here are some of the examples in our Syracuse office of multibody print jobs.

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