How to Stop 3D Print Pillowing (Best Settings)


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3D Print Pillowing

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low top layer count

‘Pillowing’ occurs on the top surface of an object. It looks like there are gaps in the surface layer, along with little bumps or pillows. You’ll normally see pillowing on prints with a wide, flat top surface rather than those with narrow tops.

The signs of pillowing are easy to notice. They include:

  • A rough-looking top layer on your print. You’ll notice that the top of the print looks bumpy and uneven like a thin sheet of cloth spread on top of rocks.
  • A pillow-shaped pattern on top of the print. This is a result of improper cooling of top layers, causing them to warp in the infill below. 
  • Holes on top of the print.

What Causes 3D Printing Pillowing?

In general, pillowing is caused by a top layer that is too thin and/or improper cooling of that layer. Under certain circumstances, insufficient infill can also contribute to the problem.

Let’s take a look at what you can do to prevent pillowing from happening.

Infill Settings

The easiest way to prevent pillowing is to increase the thickness of the top layer of your object. In most 3D slicer applications, this can be done by going to the advanced settings tab and looking for “Bottom/Top Thickness”.

In most cases, you want to have a top layer that is at least 6 layers thick. This means that if you are printing with a 0.1 mm layer height, you want to set your Bottom/Top Thickness to 0.6 mm.

If this doesn’t solve the problem, you can increase the Bottom/Top Thickness setting to 0.8 mm. In general, the thinner your layer height, the more top layers you’re going to need to sufficiently cover the infill on your object.

Thin layer height means more layers

On the subject of infill, the less you have the more difficult it becomes to lay down a top layer. 

While not a direct cause of pillowing, insufficient infill can contribute to the problem by causing your top layer to droop and sag, especially when you add in additional layers.

Poor top layer benchy
This is another example of low layer count on the top layer causing pillowing. Increase layer count, improve cooling and address any under extrusion to remedy this fault. 

Therefore, it is always a good idea to slightly increase your infill percentage when attempting to prevent 3D printer pillowing from occurring.

Similarly, the infill pattern you use can solve pillowing in your prints. A coarse infill grid requires many layers to close up, and is therefore prone to pillowing.

On the other hand, concentric and lightning patterns give better support to the top layer. As a result, they require less material and are easier to fill up to a smooth finish. 

Cooling & Overheating Issues

Poor cooling settings causing 3D printing problems on the top layers
This is a textbook example of the effects of poor cooling. Note as the design gets narrow at the top, each layer has less time to cool before the next is extruded on top of it. 

When you’re printing the top layers of your object, it’s very important that you are cooling the print material properly. 

If the top layer takes too long to cool, it may sag in between the infill layers and curl up where it touches the infill layers. This is especially true when you are using a thin layer height. 

The result is an uneven surface that becomes bumpy and uneven as the top layers are added.

Make sure that your cooling fans are operating correctly both prior to printing and as the top layer of your object is being laid down. Make sure that the fans are pointed in the right direction and are circulating air in the direction of the object that you are printing.

It’s essential to maintain steady cooling for filaments that melt at high temperatures. For instance, ABS filament requires more time to reach its melting point of 105°C (221°F) compared to other filaments. It also needs longer to cool down and become solid.

If the heating/cooling stage is not controlled, pillowing is likely to occur in the top layers of the prints. 

A high print speed can lead to pillowing, particularly with high temperature filaments. If you’re printing too fast, the material doesn’t have enough time to cool and merge well with previously printed layers. This causes under extrusion which comes with a pillowing effect. 

On the contrary, a slow print speed gives you precision in your prints, but causes overheating. A sweet spot is one that allows enough time for your filament to cool and layers to adhere perfectly.

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