Dual Extrusion Printing
Notes for Using Two Extruders

Printing with two extruders allows for two-color models. For 3D printing with dual extrusion, there are additional steps when setting up g-code in Simplify3D as well as additional features to consider. The 3D printer will still only print with one extruder at a time. Each nozzle takes a turn during each layer that needs both colors.

The notes below discuss key items, yet not necessarily every detail. Part of 3D printing is the art of deciding how you want to do things and adjusting the details as you see fit.

Simplify3D has its own support page on this topic: Printing with Multiple Extruders.

TPHS .factory File for Dual Extrusion Printing

Download the appropriate .factory file for Simplify3D and use this as a framework to import your STL model files. You may need to right-click and choose "Save Target As..."

Two Colors, Two Models

Each printed color needs to be its own model. Ideally the individual models will fit perfectly together to form the overall model you intend to print. If there is overlap with the models, the printer will try to print both colors in the same space. Overlap can cause problems with the print and/or make it look messy.

Aligning Models: Once you have both models imported into Simplify3D they will need to be aligned. If the models were created together and exported with their position data, then you can realign them after importing. Double-click one model and click the "Reset Position" on the upper right. Also do this for the other model. In the list of models on the left, now select them both and group them together using "Group Selection" in the Edit menu. Now if you have the group selected and click on the "Center and Arrange" button, the grouped model will be centered. Or you may manually adjust the location of the group using the options on the right.

Two Colors, Two Processes

To tell the printer which extruder to use for each color, each extruder needs its own process. The default .factory file linked above already has two processes set up, one for the left extruder (known as T0 for "Tool 0") and one for the right extruder (known as T1 for "Tool 1"). You will need to know which color you plan to have in each extruder so you can prepare the g-code by assigning the appropriate processes to the correct models.

Assigning Models: Open the "Left Process" process by double-clicking. At the bottom of the dialog box that opens there is a button labeled "Select Models." Choose which models to print with the left extruder and click "OK." Click "OK" to close the large dialog box for the process. Do the same thing with the "Right Process" and assign the models to be printed with the right extruder.

If you have more than two models, you need to decide which color (i.e., which extruder) will be assigned to each model. Be sure that no model is selected twice.

Advanced Note: There may be reasons to have even more processes, such as if you want different amounts of infill or a different number of perimeters in different models of the same color. You can copy/paste the processes and then make the necessary adjustments. Just be careful that you assign models appropriately. Note that you may rename a process within the process dialog box to help keep track of which is which.

Prime Pillar and Ooze Shield

Using a prime pillar or an ooze shield is critical when working with more than one extruder. You may even want to use both. Without these features an extruder may not print immediately when it is its turn and cause the print to fail or not look good when done. Prime pillars and ooze shields may also catch drips preventing strings from sticking to the actual model.

See notes on the "Rafts, Skirts, & More" page for Prime Pillar and Ooze Shield for additional details about these items.

Setting Prime Pillar and/or Ooze Shield: Open the "Left Process" and go to the tab labeled "Additions." There you will see options for including or excluding a prime pillar and ooze shield. For the prime pillar you can choose how big you want it and its location relative to the model. For the ooze shield you have some options as well. For both the prime pillar and the ooze shield, you should have them set to print with "All Extruders" otherwise they will not help prime the flow of filament as needed.

Note: If you have a model that needs two colors within the lower layers of the print, but at some point only prints with one color for the rest of the way, you could create another process for the upper part that does not use a prime pillar or ooze shield. To create a new process, copy/paste the one you have already for that color. Then in the "Advanced" tab within the first process, select "Stop printing at height" and set a height value. In the new copy of the process, select "Start printing at height" and set the value to match the stop value. In the new process, you can disable the prime pillar and/or ooze shield.

Print Preview

As with single extrusion printing, when you think everything is ready, click on the "Prepare to Print!" button. You will see a dialog box about your multiple process print. Select all processes and make sure that "Continuous printing: layer-by-layer" is selected. Then click "OK." (If you get a message that the processes are not properly configured for the number of extruders, click "Yes" that you want to continue. The configuration in the downloadable .factory file will work for our printers.)

While in the print preview, I strongly recommend choosing the "Coloring" to be done by "Active Toolhead." This will display areas to be printed by the left toolhead T0 as blue and the areas to be printed by the right toolhead T1 as bright green. It will help you see how the model will print as it fits together. Of course, it is also useful to view the coloring by "Feature Type" to see what is going on within the print.

Note: Since an ooze shield wraps around the print, it may be difficult to see key features of the models in the print preview. If you have an ooze shield, you may want to remove it for the print preview to better see what is going on.  Once you are satisfied and ready to save the toolpaths (i.e., create the .gcode), make sure you return to the process settings and add the ooze shield back in for each process. Then "Prepare to Print!" and save the toolpaths.

Export G-Code & Print

Once you have all of the settings as desired, you are ready to create the g-code. Be sure to save your factory file as well. Export g-code from the print preview just as you would for a single extrusion print.

Be sure you remember which color filament you plan to print on the left and which on the right!

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Abby Brown
Torrey Pines High School, San Diego, CA
March 2019