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Why Do 3D Printers Make an Outline Before Printing?

You may have noticed that the printer makes an outline, called a skirt, of the object you’re printing, and this outline is wider or larger in comparison. So why is there a need to outline?

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If you’re new to 3D printing, there may still be many things you don’t understand about how it works. You may have noticed that the printer makes an outline, called a skirt, of the object you’re printing, and this outline is wider or larger in comparison. So why is there a need to outline?

Before printing, a 3D printer makes an outline to ensure that the heated nozzle is primed and ready to print smoothly and evenly. The nozzle sometimes doesn’t extrude filament immediately, so the outline gives it time to work through this slight blockage before it starts printing the first layer. 

Read on to find out more about why a skirt is essential when printing 3D objects.

Why Is a Skirt Important in 3D Printing?

The skirt or outline of your main print is an important element in 3D printing because it helps give you a smooth finish for your 3D model. But its initial goal is to help you build a good first layer, which is the foundation for the piece you are printing. 

A skirt also helps ensure there are no issues with your 3D model during the rest of the printing process.

It’s good practice to print a single-layer skirt before it starts printing the main object or model. This single-layer outline or skirt is an effective method to get the filament extruding and flowing evenly from the 3D printer’s nozzle before it starts forming your object.

Building an overall good first layer is critical to the success of your 3D print output. Moreover, a skirt can also help prevent adhesion-related issues. And it does so without actually using much filament.

How Does a Skirt Work in 3D Printing?

In 3D printing, a skirt or outline for 3D printing is like testing a pen on the corner of your sheet of paper before you start drawing or writing. A 3D printer works by extruding or expelling melted plastic filament through its heated nozzle. 

It usually takes a while until the printer builds up enough pressure to extrude the filament needed to form full layers for a solid foundation. The skirt, therefore, provides the necessary allowance while this pressure accumulates.

It’s common to see a small blob or clump of plastic filament coming out of the nozzle after laying down your outline. This blob is usually the leftover material from your last 3D print and isn’t a part of your current piece. As such, you wouldn’t want this clump of excess plastic coming out while printing the very important first layer of your 3D object. 

The outline helps ensure that this leftover material being squeezed out doesn’t make it to the crucial first layer of your current 3D project as you start printing. It allows this blob of leftover plastic to be extracted before the first layer is even printed.

Other Benefits of a Skirt

A skirt is a reliable way of seeing how well the bed of your 3D object is leveled. You can also see whether the printer’s nozzle and the filament are creating enough contact with the surface of the bed. With this, you can create a first layer that is sturdy.

When your printer’s nozzle is too high off the bed’s surface, it won’t create sufficient downward pressure. Therefore, the first layer of your 3D model can’t stick firmly to the bed. 

Similarly, the filament won’t flow through evenly when the nozzle is too close to the bed. A heated nozzle that’s too close can even scrape the surface of the bed.

Additionally, using a skirt allows you to assess how well the printing is doing. 

After printing out a couple of layers of the skirt, you can easily gauge if your print is doing well. You can also see if you need to troubleshoot and stop the process before you waste too much filament. 

If your print isn’t flowing as smoothly and evenly as it needs to, you may need to adjust certain settings. Consider adjusting the bed temperature and the printing temperature to clean the printer’s nozzle or adjust the bed’s level.

Skirts can also function as a draft or thermal barrier that protects your 3D prints. A skirt around a bed, for instance, can provide a certain degree of insulation from drafts that can easily change temperatures in the room. Changes in temperatures can contribute to surface warping.

What Happens When You Don’t Use a Skirt?

If you don’t use an outline or skirt in 3D printing, it won’t change the fact that your printer’s nozzle will still need to get primed. Priming will still take place, and your printer will do so on the first layer of the 3D piece you’re printing

This, in turn, could lead to issues related to adhesion and poor first layer quality.

So, in knowing how important a skirt or outline is, the question is more of why shouldn’t you opt to use an outline. It can also be why you shouldn’t opt for another adhesion solution.

How To Add a Skirt to Your Print

While adding a skirt is straightforward, it may also depend on the kind of slicing software you’re using. 

Go to your slicing software, then go to settings. Under print settings, you can select the adhesion options.

For instance, in Cura slicer, you can scroll down to the Build Plate Adhesion row then press the down arrow to expand. Put “Skirt” beside the Build Plate Adhesion Type. And beside the Skirt Line Count key in the number of skirts you want to use for your prints.


Using an outline for 3D printing ensures that you get a clean, smooth, and even 3D object afterward. The skirt protects the first layer of your piece, which is the very foundation of any 3D object. It also gives your nozzle the time to prime itself and get ready to print.

There’s no need to worry about filament waste when using a skirt, though, because it uses up very little. The assurance of getting a good-quality 3D object after printing also saves you the amount of filament you’ll otherwise be wasting if you print an entire bad piece.

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About Ben

I started 3D printing since 2013 and have learned a lot since then. Because of this I want to share my knowledge of what I have learned in the past years with the community. Currently I own 2 Bambulab X1 Carbon, Prusa SL1S and a Prusa MK3S+. Hope you learn something from my blog after my years of experience in 3D printing.