Introduction: Dual Extrusion 3D Prints Using Sketchup and Simplify3D

About: Unfortunately the owner of this site has passed away however it has not been closed to allow other users to hopefully benefit from some of the projects.

Note that this instructable pre-dates the latest version of Simplify3D and its support for dual extrusion printers.

This instructable illustrates how Sketchup can be used to create dual extruder (e.g. two color) 3D prints using Simplify3D as the slicer.

Our demo task is to produce a rectangle of black plastic with the name "Sara", in grey plastic, embedded into the surface of the black plaque. This is a simple example but the techique is scalable and the Sketchup instructions should work with other slicers.

The Sketchup file for this example is attached below.

Step 1: Setting Up the Framework

We are going to use the Sketchup Layers feature to help us organize the individual elements of our model. There will be three layers with the default layer containing the bounding box that will align everything for the slicer.

To get started create a frame in the default layer with a height less than the layer height that you will print. In this example I am using a height of 0.1mm given that I will print at 0.2mm. Simplify3D will ignore this shape when it slices your model. Note that it will also ignore anything that it thinks is part of this shape so don't have anything touching it!

Step 2: Create Your Model Using Sketchup Layers for Each Color

Create two new layers in Sketchup with one being for each color that is needed for your model. You can either design element by element in the appropriate layer or, more likely, develop the model and then segregate into appropriate Sketchup layers. Remember that you move things from layer to layer using the entity info form (right click).

For demonstration purposes I have only two elements of my model with the plaque being one (with an indent for the letters "Sara") and the actual letters being the other.

The two little rectangles in the upper left and right corners are intended to serve as "prep" areas for the extruders and will serve in a similar manner as an initial skirt would do for a single extruder model. You should have one of these for each color as part of the two layers. The "prep" objects should be as tall as the last place where both nozzles are used.

Please see the caveat at the end of this instructable for a discussion about this technique.


  1. Make sure that the base of your model, the bounding box, and the two prep areas are all on the same place on the Z axis!
  2. The "prep" should really be on the default layer as it makes it easier to select the model for export (you can to a select all without having to deselect the prep object). For the purposes of this demo it was easier to show it as I have.

Step 3: Export ".stl" Files From Sketchup

Now we create four ".stl" files for import into Simplify3D:

  • The first file to export is the prep file for first color. In the case of the example this is Grey. Select the grey layer and make the black layer invisible. Then select the bounding box from the default layer and the prep rectangle from the grey layer. Export this selection to a ".stl" file (in this case "GP.stl"). This will be the "Prep" file.
  • The second file to export will consist of the model components to be printed in the first color. This should be everything in the grey layer with the exception of the prep rectangle (which could live in it's own layer or in the default layer). This will be the "Model" file (in this case G.stl).
  • Repeat the above for the other color creating a file with the prep rectangle and another with the model components to be printed in black.

The above files should be imported into Simplify3D with the "Prep" file preceeding the "Model" file for each color. This seems to be important to ensure the order in which they are handled. I am not entirely sure why!

When the above files are imported into Simplify3D they will be distributed as best they can on the illustrative build platform as shown above.

Step 4: Create a Process for Each ".stl" File

A process needs to be created for each of the ".stl" files imported in the last step. Order is important as the "prep" file should be processed before the "model" file.

The starting point for these process files needs to be the "(both extruders)" profile so both extruders are heated.

For the example the grey filament is on the right extruder and the black filament is on the left extruder. The settings important to printing with dual extruders, for two color models, are:

  • In Layer: Set the "primary extruder" as appropriate to the color.
  • In Additions: Make sure that "skirt and brim" is not selected as our "prep" process handles the skirt.
  • in Infill: Make sure that the extruder for infill is the same as is being used for the current color.
  • In Support: Choose the extruder for support, if it is needed, as appropriate.

All other settings should be as needed for whatever materials are being used for printing.

Step 5: Assign Each Model to a Process

At the bottom of the process form there is a button that will allow you to assign models to that process. It should be used to marry each process with the appropriate ".stl" file. For our example we want to marry the grey prep file ("gp.stl") with the profile "gp" and the grey model file ("g.stl") with profile "g".

Step 6: Prepare to Print!

The imported model files should now be consolidated into a single stack for printing. This is done by holding the "Shift" key and pressing the "Center and Arrange" button. If all has gone well with your handling of the bounding box in Sketchup you should see the four models come together for printing as shown above.

Once this is done you can press the "Prepare to Print" button. At this point you will be asked to select what processes to print. Select them all (there should be four of them) and make sure that the "continuous" printing selection is also checked.

Print it!

Step 7: The Result

The first photo above shows the print paused after the first layer. Obviously you can see the two extruder prep areas as well as how the first layer has been printed. There is still quite a bit of ooze that needs to be sorted out.

The second is at completion of the print job. The third is the final product. Again, on both of these photos you can see ooze mess. I think the product looks pretty good but obviously there is some tuning to be done.

At this point the keen observer will have noticed that the design called for a black plaque with grey letters and what was delivered was the reverse! Oh well.

Step 8: Caveat in Regards to Nozzle Priming Process

The process that is presented here attempts to prime the extruder nozzles using what are in effect sacrificial objects. This is not a 100% solution as Simplify3D does some things that will cause this mechanism to be ignored once in a while.

There is a good discussion of this topic on the Simplify3D message board. What is needed is for Simplify3D to have support for nozzle prep as a feature.

Since it is not a feature I have tried to put something together that is reasonably easy to implement and works better than nothing. Hopefully a lot better than nothing. My observation of printing movements leads me to make the following recommendations (repeated here from the text):

  1. The "prep" objects should be as tall as the last place where both nozzles are used
  2. The process to print a "prep" object should be in front of the object (or objects) that will be printed in the same color.
  3. The models imported for printing should have the "prep" object ahead of other models to be printed in the same color.

I don't have any science behind this estimate but it feels like this will result in at least 80% of the time having a good prep of the nozzle before starting a color.

As I state above, I believe that Simplify3D needs to support some form of nozzle prep as a feature for doing dual colour prints. Unless of course it is in there and I have missed it!

What I have done here works, most of the time, but can be a real pain given some other ideosyncracies of the product. One of those being that when a factory file is saved Simplify3D changes the order of the processes to what looks like an alpha sort? So, what I had arranged in order of my desired process is gone. Further, every time you make a change to a file that is part of your process you need to reload that file, and if the order is impacted by that reload, you need to reload all the files. Then you have to tell each process what file it is supposed to handle. It would be REALLY nice if there was a simple refresh function. I can't be the only person who does things iteratively?

I really like a lot about Simplify3D and use it as my primary slicer for "normal" printing. I am not sure that it will be my primary slicer for dual color prints but I have not explored other options yet.

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