This post describes the computer aided design (CAD) file that we will be using to create our part. While we could have created our own 3D model, after perusing the Thingiverse website we decided that there are plenty of CAD models available that would satisfy our design requirements. We are basing our CAD design off of the Thingiverse project known as “The 3D Printed Marble Machine #2” http://www.thingiverse.com/thing:795952. This marble machine is an ideal start for our project because it includes a marble transport mechanism and a complex track. The design consists of the following components:
Figure 1. The screw used to transport the marble.
Figure 2. Additional screw components are the cap that holds the screw in place seen below.
Figure 3. Additionally, there is a part of the cap that allows the user to spin the screw using their finger.
Figure 4. Finally, the track itself as one large part.
Note: All of these images were taken from the The 3D Printed Marble Machine #2 Thingiverse page.
We need to consider the complexity of each part and the what the best printer setting will be for each. The screw is one of the most important pieces and thus needs to be carefully printed. The caps will be the easiest parts to print and can be accomplished at the same time. The track will be a very large print since it is one piece and will require a significant amount of material.
These parts are the first part of our CAD design. Going forward, we would like to make some additional changes to the parts and print some new ones. The first change we want to make is to use a transparent material for the cylinder surrounding the screw. This would allow the user to see the ball as it travels from the end of the track to the top. Additionally, we would like to attempt to print the marbles themselves. In order to make the marbles functional, we will have to convert the Solidworks file to a very fine STL file and print with a very small layer thickness. If there is enough time, we would also like to explore printing individual parts of a new track that could snap together.
One of the biggest challenges we faced was separating the cylinder from the rest of the track. To isolate the cylinder that surrounds the screw, we used an evaluation trial Magics 20. First we tried Meshlab, MeshMixer and the SolidWorks STL plug-in. These three options failed due to the file being to complex (too many triangles), failed during the boolean operation, or the result of the boolean operation was unsatisfactory. Magics was able to handle the large STL file size. We loaded the entire track STL file into Magics, and created a second object that was a cylinder identical in size to the part we wanted to isolate. By mating the cylinders’ top faces and outer curves, we were able to line the parts up perfectly. From here, we performed a boolean operation to only keep the intersection of the two parts, and this produced an isolated cylinder part. Some images of this process are seen below.
Figure 5. This shows the process of separating the cylinder from the track. As can be seen, a second cylinder was created (seen in green).
Figure 6. This image shows the process of lining up the cylinder with the track in Cura. Since the program does not have an alignment feature, this was particularly difficult.
