T1W9: TinkerCAD Keychain
Now Meeting in the Innovation Studio - Primary School Building Room 120!
This will be our last week in Term 1 - it has gone quickly! The top priority is getting everyone's night lights finished, and the other students should be working on the keychain design. There won't be time to print them in class (the 3D printers are not working) but I can print them at home if students email me the .STL files from TinkerCAD.
Both 6th and 8th graders say they have used TinkerCAD before, but if anyone needs a refresher follow the Starting Lessons tutorials to go over navigation and editing.
TinkerCAD works in Metric units to start with, each small square on the grid is 1mm. Changing the grid spacing to 0.5mm might make it easier to position your text - look for the "Snap Grid" control in the bottom right of the work area. A good key chain size is 50-80mm wide by 20-30mm high. It can be 3-5mm thick and there should be a hole in the end for the key ring of 4mm in diameter. Don't put the hole too close to the edge or the plastic can break under the strain of twisting keys.
Start by putting down a shape that will be the base of the keychain. You can make it rectangular, oval, or heart or star shaped if you want. Also look at the "Shape Generator" menu on the right side, I used the "SoftBox" to make a rounded rectangle.
Use the cylinder shape with the "hole" option to make a hole in one side of the base shape. The cylinder should be 4mm in diameter to allow for the key chain rings I have, and as high (or higher) than the base. When you select the base shape and the hole and click "Group" it will unify them into a single shape with a hole in it.
Then select text, enter the message of your choice, size it to fit on your base, and place it on top of the base shape. You can select different fonts, and you can adjust the "boldness" of the letters by changing the "Bevel" slider - I had best results with the "Sans Mono" font, which spaces the letters further apart.
We will export the .STL file that the 3D printing software uses next time. Here is my example keyring:
I make it a little fancier by adding a bezel around the outsize of the shape. The "SoftBox" object makes this easy, but you can do it by shinking your base shape a little and using it as a hole at the top of your base.
Exporting the .STL File
The output from TinkerCAD is a .STL file (stands for stereolithography) which breaks the shape that you designed up into a series of triangles in 3D space. The file just has the outside edges of the shape with no color or other information, and no instructions on how to actually print the object. You can generate the .STL file in TinkerCAD through the "Export" button in the upper right of the window. Include "Everything in the design" and select For 3D Print->.STL. The file will probably be downloaded and saved automatically on your Chromebook, using the name that TinkerCAD has chosen for your project. If you want to use a different name, click on the project name in the upper left of the window and type your new name.
Since we won't be printing the .STL files in class, send them to me at the email address I will give you in class and I will print them on my home printer. I'll try to use cool silky looking rainbow-colored filament to make the keychains really stand out!
Generating GCode for the 3D Printer
We won't have time to do this in class, but 3D printers need an extra step before they can print the shape you designed in TinkerCAD. A "slicer" program takes the 3D geometry in the .STL file and turns it into layer-by-layer instructions for printing the 3D object on the 3D printer. Most 3D printers use G-Code as their control language. G-Code was developed in the late 1970s as the control language for CNC (computer numeric control) machine tools like milling machines or routers. G-Code is a text language with lines that have a command that starts with the letter "G" and a number, and then have a series of numbers that are the physical locations for the machine to move. There are also G-commands to change the temperature of the printer nozzle and start and stop the flow of plastic. The exact content of the G-Code files therefore depends on the model of 3D printer you are using, so you have to configure the slicer program with settings for the type of 3D printer you are going to use, and a G-Code file made for one printer generally won't work on another (or may not have the right values).
Once the slicer program converts the .STL file to G-Code, the G-Code must be sent to the 3D printer. Some 3D printers are controlled directly by a computer over a USB connection, but most these days have their own smarts and work with a copy of the file that is either sent over the computer network by wire or Wifi, or copied to a flash drive or card that is then inserted in the printer. Most current printers have a control box and screen that let you select the file to print and change other settings before starting the printing.