Digital technologies/3D printing/3D printing- Intermediate/Dual Colour and Dual Extrusion

Dual colour prints refer to a technique that can print multiple colours on one model using one nozzle head. This is achieved by switching the filament during the printing process. Dual extrusion refers to printing a model with 2 nozzles to extrude two different filaments. This will allow for mixing colours, gradients, or patterns. It can also print models using two different materials for different parts of the object for complex geometries that would otherwise be difficult to achieve.

Dual colour prints are achievable using the Ultimaker 2+ printers.  In order to change the colour during the print, a script is added to the g-code telling the printer to stop the print at a certain instance. This is done during the slicing process in Cura.

1. Click on “Extensions” in the top menu bar.
2. Select “Post-processing” -> “Modify g-code”.
3. Click on “Add a script”
4. Select “Pause at height”

At this point, there will be many different settings to modify. First, determine if you would like to pause at a height value (mm) or at a layer number. Choosing a layer number would be a simpler option in ensuring that the print ends when a full layer is completed. The layer number can be seen in the “Preview” mode on Cura. The model can then be sliced like normal. Once the print stops, the material can be changed (ask the staff) to complete the print in a different colour.

How to Dual Colour Print with an UltiMaker 3

Step by step process for printing with an UltiMaker 3.

To do dual extrusions, we need to get two separate 3D models (if they are part of the same part they can be merged later)

Open Cura and make sure the printer selected is Ultimaker 3. If not, change it by clicking on the printer drop down menu (top left) and selecting the right one. Printers can also be added by clicking on “Add printer.”

Open the two models in Cura by opening the file explorer tab in the top left corner beside the printer's name. You can also go on “File -> Open files (CTRL +O).”

The next step is to set the print core and the materials. You can do that by clicking on the sidebar print core option as shown below. Both print cores should be set at AA 0.4. Material is set to PLA by default, but you can change by going under material and selecting one of the approved printing materials.

The colour of the filament loaded in the printer will determine the two colours of your print therefore there is no need to choose the colour on Cura.

At this point we need to assign a print core to each one of the two models. All objects are set to be printed with the print core 1 by default. If you want to change the print core, select the model by clicking on it. Next, select Per Model Settings (on the left side of the screen), then Print Model with Print Core 2.

After the print core settings are done, you can merge the two parts of your model together. First, you select both parts by holding shift and left clicking both parts. They should be outlined in blue. Then right click and select “Merge Models.”

If you are using recommended mode, it just becomes a single model, and you can adjust different settings as you would do for a single extrusion. The changes will be applied to both settings at the same time. If you need to adjust settings for one print core, you need to switch to custom mode.

The last step is slicing by clicking “Slice” and save the gcode on a USB stick which will be inserted into the printer. Put the USB stick into the printer, select “Print.” The printer will read the drive and display the available gcodes. Select your file and the print will start.