In most slicer software, you can observe that the whole set of slicer settings isn’t available to the user by default, with the slicer only displaying the options that are essential to the printing process.
On the other hand, the more advanced settings require the user to make them visible through filters, as such parameters are optimizations rather than essentials and can be detrimental to the printing process when misused.
Today, we will be looking into one of the more advanced features in PrusaSlicer, known as external perimeters first, which is a feature that can considerably contribute to the printing process when activated in the correct scenarios.
So, what is the external perimeters first feature in PrusaSlicer?
Activating the external perimeters first feature in PrusaSlicer instructs the 3D printer to print the perimeters starting from the outside and moving inwards, as opposed to the standard order of printing the inner perimeters first and moving outwards.
Next up, we will take a more detailed look into the external perimeters first feature of PrusaSlicer, find out how to activate this feature, discuss the scenarios where it makes sense to use the feature, and take a quick look at other perimeter-related parameters in PrusaSlicer.
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What Is the External Perimeters First Feature in PrusaSlicer?
While the external perimeters first feature in PrusaSlicer has the ability to perform a considerable modification on how the printing process will conduct, it’s also a feature that is pretty uncomplicated to understand.
The external perimeters first feature in PrusaSlicer is an expert feature that makes the 3D printer invert the order it uses for printing perimeters, causing the printer to start from the outside perimeters and move gradually towards the inside.
The change in perimeter print order gives the model better dimensional accuracy at the cost of reduced surface smoothness, introducing a trade-off that makes its activation only suitable in some scenarios, which is why it is considered an expert feature.
To better understand the difference this feature causes, we would highly recommend printing the same test model with and without it and observing the results, as seeing the differences first-hand is, without a doubt, the most straightforward to know how a slicer setting impacts a model.
How to Activate the External Perimeters First Feature in PrusaSlicer?
As the external perimeters first parameter only consists of a checkbox, without any other extra parameters that require configuring, activating this feature is pretty straightforward once you know where to find it.
Activating the external perimeters first feature in PrusaSlicer is a straightforward task that you can perform in a few seconds by following the step-by-step guide we have shared below:
- Click the Print Settings tab located at the top of the PrusaSlicer window.
- Click the Expert button located at the top-right of the PrusaSlicer if you haven’t already, making expert settings, such as external perimeters first, visible.
- Locate the external perimeter first label under the Advanced section of Print Settings, and click the checkbox next to it to activate the feature.
If you would like to keep the external perimeters feature permanently active for the profile you’re configuring, don’t forget to click the diskette icon located next to the dropdown menu at the top-left corner (below the tabs) of the PrusaSlicer window, which will update the preset.
When to Use the External Perimeters First Feature in PrusaSlicer?
The requirement of having a good understanding of when to activate the external perimeter first feature is why this feature resides in the Expert section of PrusaSlicer’s settings, as enabling this feature in some scenarios can cause more harm than good.
We recommend using the external perimeters first feature in PrusaSlicer whenever you would like to increase the dimensional accuracy of the model you’re printing as much as possible, such as printing functional parts where the correct dimensions are vital for the part to fulfill its purpose.
On the other hand, as activating this feature is highly likely to cause the surface finish to become worse, we would recommend refraining from using it for models with aesthetic purposes, especially considering that dimensional accuracy won’t be as much of a concern in such scenarios.
Other Perimeter-Related Parameters in PrusaSlicer
Aside from external perimeters first, there are a few more perimeter-related options you can configure in PrusaSlicer to improve your prints, which we will take a quick look at in this section.
Below, we have listed the perimeter-related settings you can find in PrusaSlicer, along with their descriptions:
- Avoid crossing perimeters – Re-configures the travel move patterns of the printhead to ensure that it avoids crossing perimeters whenever possible, which can be helpful to combat oozing issues.
- Detect bridging perimeters – Instructs the 3D printer to automatically apply bridge flow and speed settings for the overhanging and bridging parts of the perimeters.
- Extra perimeters if needed – Allows the 3D printer to add extra perimeters to ensure no gaps in sloping walls.
- Perimeters – Determines the number of perimeters to generate for each print layer.
- Infill before perimeters – Instructs the 3D printer to print the infill before the perimeters.
- Only retract when crossing perimeters – Disables retraction unless the printhead moves above perimeters.
- Infill/perimeters overlap – Determines the percentage of overlap between the infill and the perimeters, which can be helpful to ensure that there are no gaps between the perimeters and the infill.
While the external perimeters first feature of PrusaSlicer is definitely handy in many scenarios, knowing when to activate and when to deactivate is vital to obtain the maximum benefit possible while avoiding the downsides.
To quickly recap, when you activate the external perimeter first feature in PrusaSlicer, the 3D printer will start printing the outer perimeters of the model and gradually move inwards instead of printing with the standard order of printing the inner perimeters first and moving outwards.
Activating the external perimeters first is known to help with the dimensional accuracy of the model you’re printing, but the increase in accuracy can come with the drawback of losing smoothness on the outer surface of the 3D printed model.
Mike started his 3D printing journey with the Anet A8 when it first came out back in 2017, and has been obsessed with 3D printers ever since. Nowadays, he primarily uses his Ender 3 to print functional parts that make his life more convenient whenever possible.