3D printing opens up a whole world of creation for people right in their own workshop. You can make simple trinkets, complex models and things that simply cannot be realized by traditional manufacturing methods. The ability to put together a model, visualize it, and then have it sitting there in front of you is awesome.
Suddenly you can test fits and clearances in hours instead of days. Recently NASA managed to print a rocket nozzle with a honeycomb internal structure they reduced the weight significantly without compromising the ability to handle the intense strains the part comes under, this would not have been easy to realize with traditional subtractive manufacturing like milling.
Today I want to show you a trick to handling complex shapes that include a lot of overhangs and changes in direction. Also I wanted an excuse to print a space ship. I am printing these models on our Lulzbot Taz5 that we have in the lab but if you want to start smaller with something still quite capable look at the LulzBot Mini which will take up less space on your desk.
For complex models like this you can handle then in three different ways. The first method would be using support structures to support overhangs. A lot of the software you use to generate the gcode used by the printer has the ability to automatically add supports to places that might needed. You can configure what overhangs are acceptable and what need to be supported based on your printer and material. once the print is done you cut out the supports and clean up where they touched the model. With some effort you can get to a pretty good surface finish but it take some time after printing. Below is a render from Lulzbot's CURA version showing supports in blue, they would have been extensive and taken a while to clean up with a lot of work to get a smooth layer on the underside.
Another method is an extension of the support method. If you have access to a 3D printer with two extruders, meaning it can print in two materials at the same time. There are some materials specifically designed to be used in support system and they easily dissolve away in water like PVA or other chemicals like HIPS. This process can take a bit and helps if you keep the liquid warm and agitate it regularly but once done you can have a nice finished piece without a ton of work after printing but you do have to have a dual extruder printer. We didn't have a dual extruder printer on hand so that left me with the third option.
The last method I am going to talk about is the one I typically use for complex things. I break them apart into multiple pieces and reassemble them later. On a lot of models you can start to see the lines on which you can break them apart to print with minimal, and sometimes, no support structure. On this spaceship certain parts just make sense to print separately, they could be reoriented to reduce overhangs. In the images below you can see the divisions I made and how they end up on the print bed letting me print without any supports. I tore off the wings so they could print upright and split the main body in half so the antennas could be vertical.
After printing I put the model together using some super glue which holds really well to the HIPS material I was using but should do fine on PLA or ABS as well. Some clean up with a sharp knife and you have a good looking 3D model more complex than a single print would have allowed and ready for paint.
