The purpose of this tutorial is as a supplementary document for an introductory 3d printing workshop run by the University College Dublin Electronics Society. The goal of the workshop was to allow members to create their own personalized 3d printed coins. Both Google Sketchup and Cura are much more powerful, and can do far more than what is outlined in this tutorial, but this is aimed as an introduction to both programs.
In the workshop we use Ultimaker 2 3d printers, if you have access to a different printer, the steps are almost identical except for the machine setup stage. You must enter the specifications of your machine for this step.
Step 1: Download the Software
For this workshop well be using two pieces of software, a computer aided design software package, in our case this will be Google Sketchup, and a slicing software which will be Cura.
Sketchup Make can be downloaded from here for free: http://www.sketchup.com/download
Cura can be downloaded from here: https://ultimaker.com/en/products/cura-software/list
The download of Cura that will be used in this tutorial is 15.04.6. Feel free to get a newer version, however the layout is quite different so getting one of those might makes these notes largely redundant.
When setting up Cura, you’ll need to add a new machine with the built in wizard. The machines we use are Ultimaker 2’s
Step 2: Sketchup Setup
Download the Sketchup files available on this Instructable. You'll only need the '.skp' files for this tutorial, but I have included the'.stl' files too as this is a more standardized format for working with across many CAD programs in case you want to work using one of these packages instead. Open these files using Sketchup. Note, while it isn’t overly important, whenever you open Sketchup you will be presented the option of selecting a template. It is easiest to select one that will work in millimetres, and particularly the 3d printing one located at the bottom of the list of templates. Doing this simply sets the standard units that Sketchup will work with. The coins downloaded from the website are all similar designs, so it is recommended that you take a look at all of them then decide on just one design that you want to print.
Step 3: Creating 3d Text
For this intro to CAD we will attempt to write some 3d text that will be placed on the surface of the coin. To do this we will use a feature called 3d text. It may be already available towards the top of your screen but if not you probably need to enable the specific toolbar. To do this click on View -> Toolbars… and enable the ‘Construction’ toolbar. This will add a set of 5 features at the top of the screen. Now select the 3d text feature. You will then be presented with a dialogue box asking you to enter text. This is the text that we will place on the coin. It is recommended that you keep the text as short as possible, your initials would be a good example. This is because the printer will struggle to print the small details if you have a large amount of characters in your text. The text box also has a value labelled as height, this is a measure of how tall the text is, in terms of xy axis. A value of 10mm is a good starting point but this can be scaled later if it is not correct. To make it 3d you need to make sure the extrude option is checked. This will allow you to edit a value field below that of the height field. This is how far the text will be extruded in the z axis. To be flush with the coin it is best to keep this around the 1.5mm mark. Once you are happy with the settings you can hit place which generates the text in the workspace.
Step 4: Placing the Text
Next is to place the text correctly. Once you generate the text you have the immediate option of putting it into the workspace. It is best to place this initially at the origin. This is so as you have a reference in 3d space as to where it is and can be moved from here. You may find now that the text isn’t the right size or in the correct position. This can be changed using the move and scale features. Like before if you don’t have them available you’ll need to enable the toolbar, which in this case is the ‘getting started’ toolbar.
To move the text around, use the ‘Move’ feature. Note that when you are using this feature it can move in any direction you want, but the program will also snap to the x, y and z axis when you approach moving in these direction. This is very useful in this case as we don’t want to move in the z direction, only in the xy plane. Moving in the x direction is indicated when the line showing the direction of translation of the text object in the workspace turns red. Similarly of the y axis when the line turns green. So to position the text we will do so by moving in a series of individual x and y direction moves. The distance of a single move can be done by eye or more precisely by typing the distance, which will be in whatever standard units you chose as a template on start up, immediately after you make a move. For example, if say, we want to move in the x direction 4mm, I would manually move the object in the direction I want to go, place it some distance from the start point on this line, then type in 4 and hit enter. The text object then shifts to 4mm from the start position in the direction I moved it in. The measurement values are seen in the bottom right of the screen. These unfortunately are not selectable by mouse click, but rather can be accessed only by typing into the keyboard immediately after doing an operation, and will only effect the immediately last operation.
We can also scale the text, this can be done using the scale feature, also located in the ‘getting started’ toolbar. Using this feature adds green cubes to the six faces of the text object. These are what you use to scale. These cubes are associated with their corresponding opposite cube. So moving one of these will scale the model in whatever direction taking the opposite as a fixed point. So for example selecting a cube in the centre of a face will move that face towards or away from the opposite cube, scaling the length, or width, or height individually. Using a centre cube will only effect one face at a time. Using a corner will scale all three faces at once in a similar fashion, and moving an edge will scale the two faces directly connected to that edge. The scale factor can once again be typed to scale by a precise amount. Scaling by a value from 0-1 will shrink the model, greater than 1 will grow it. You can scale by negative amounts, which will invert the object in the direction of scaling and scale by the value.
Step 5: Saving and Exporting the Model
Once the text is positioned, you will want to export the file. You probably will want to save a file in the native Sketchup file type also so you can revisit the model later if you wish. To export the model as something that Cura can read you need to go file-> export->3d models… It is possible in Sketchup to download extensions using the extension warehouse that will allow you to export to a more standard format but for our purposes it is unnecessary. A file type is available to you in export model called .dae. This is the file we will use.
Step 6: Cura
For this demo we will be doing batch prints of several coins at a time to speed up the process. To do this give your '.dae file from sketchup to one person at your table, so they can all be printed from one gcode file later. Depending on when you start printing you may be able to collect your coin by the end of the day if not, you will be able to collect your coins from the engineering building foyer tomorrow.
Once you successfully exported the file, go to cura and import all the coin files from everyone at your table into the build area by selecting file-> load model files… If everything worked well your model will be imported into Cura. Cura will automatically arrange the coins to fit the build area. Cura has the option of changing many variables associated with the print however for this small print we will not be using these. The Ultimaker is finely tuned to work exceptionally well with the standard settings so these are what we will use. The material we will be using for this project is PLA. Since 3d printing is a slow process we want to print the coin as fast as possible for this exercise, so select the ‘Fast Print’ option. You will not need any support structure for this print or bed adhesion. If you have done all the steps correctly the print should take about ten minutes to print per coin on the build plate. The print time is displayed towards the top left of the screen once the program has sliced the model. Once you are happy you can save the file on one of the sd cards for the 3d printers. This is done under file-> save gcode… then select the location of the sd card. It is probably a good idea to save the gcode as something unique as there will be other files on the sd card from old print jobs and doing this will make it easier to find the file.
Step 7: Starting the Print
Note: this step is exclusively for using with an Ultimaker 2, other printers will vary in their setup. Save the gcode to the SD Card using a memorable name. Insert the SD Card. Ensure the printer is on – it will light up if it is. Using the wheel to the right of the screen navigate to 'print' by spinning the wheel and clicking it, Then select the file you uploaded on the from the list of files. Wait for the printer to heat up and enjoy as your 3D printed piece is made.