3D printing and scanning
This week, we explore additive manufacturing and the objects that are uniquely made possibly through the addition/accretion of multiple layers, rather than through the subtractive processes of cutting and grinding. We also explore 3D scanning technology, using sensors (often infrared) to detect depth and light scattering and recreate a 3D model of a real world object.
For this module's 3D printing assignment, I returned to my final project concept: the self-assembly, geodesic dome (for ultimate deployment in zero-gravity via a cubesat). Working from the solidworks models from the first week, I saved .stl files and submitted these for printing. Due to equipment issues with the Stratasys Dimension printer, we used the Eden objet printer. This proved to be a particularly fortuitous choice, as the objet printer produces a rubber-like printing material that provides a tighter, more forgiving fit for interlocking parts. Below, you can see the pentagon tile and hexagon tile. I printed only three of each, to test the fit with the magnets. The test was successful, and I can now move on to printing the rest of the parts!
Why are these pieces worthy of additive manufacturing?
The parts you see below include recessed holes for magnet joints. These holes are angled with respect to the top and bottom faces, meaning they recess in and produce a flush mating face for the magnet to magnet bonding. This hole angle would be particularly difficult to achieve with a traditional 3 axis mill, as the mill could not simply go down straight into the part. We would have to arrange the part on it's side, and have the mill drill into the edge surface...but the other side of the object is not flat, so we would not be able to set it down on the milling surface. This would require custom clamping, or perhaps a 4 axis mill to achieve the recessed hole angle. With these considerations, I believe these parts merit additive manufacturing.
With the tiles now printed, I began inserting the magnets and testing the magnet joints! I'm happy to report that the magnet strength is more than sufficient to keep the tiles bonded, and that the dimension tolerances I accounted for in SolidWorks were correct. The tiles' angled edges mate smoothly with the relevant hexagon and pentagon neighbors, and the magnets fit snugly in the holes. As mentioned above, the slight give and rubber-like property of the Eden prints also help the mating fit.
Additional 3D print testing
The designs below are not my own, but I selected them for testing the 3DWox printer we have in the lab (the machine shown below). The 3DWox offers a climate controlled, heated chamber that keeps the temperature of the print bed and surrounding air consistent--this yields better adhesion for each subsequent layer of extruded plastic, and therefore, a better print. I selected the two shapes for their interesting organic features, thin edges, and complicated layering (particularly in the porous, "cellular" piece).
A few points on using the 3dWox:
- Download and open the 3dWox free desktop software
- From the File menu, select Load Model and choose an .stl file to import (other file types may be supported as well)
- Scale down the print as needed, with the tool bar on the right side of the software interface. You can also rotate the model, add or remove support material, and change the position of the print on the bed.
- Use the settings menu on the left side of the screen to confirm printing material (PLA for our prints) and print speed.
- When you're satisfied with what's about to be sent to the printer, go to the File menu again and "Save G-code". Take this file to the printer, either by sending a command to the printer from the software interface (if you're networked to the printer) or by plugging in a USB stick (with the relevant file) to the touch interface on the 3dWox.
- Start your print, and note the time estimate! Be sure to clear the platform of any prior prints and waste material. Make sure the door to the climate controlled chamber is firmly closed.
For the 3D scanning part of this week's assignment, I used the "Sense" handheld tool. You can see screenshots of the scanning software interface below. The first shows what the scanner sees of my face, parlayed onto the screen:
The second is a self-referential scan: scanning the screen that displays what the scanner is seeing.
The third shows a partially processed scan of my head and shoulders, where I'm using the erase tool to clean up the point cloud
After completing and "solidifying" the scan for 3d printing, I was able to submit an .stl of the scan to the 3dWox for printing!
Notes on using the 3D scanner
- Move slowly and deliberately around the object you are trying to scan. Moving too fast will cause the program to lose tracking.
- It's fine to overlap, and scan over an area multiple times as you move around an object to get a 360 degree view.
- Optimize for the proper distance between your object and the scanner. You will see the resolution improve and deteriorate as you move closer or farther away.
- Try to keep your object inside the target icon area that's shown on the screen, for best processing.
- Clean up the initial scan, to remove disembodied areas (that aren't connected to anything else) or extreme peaks/stray areas that would be difficult to 3d print (if printing is your final goal).