Shell settings

Wall extruder

This setting defines which extruder should print the walls. It can be set for the inner or outer wall separately.


Example: Use two colors of the same material to create outlines on 3D prints.

Wall thickness and wall line count

This setting adjusts the thickness of walls of the model. Ultimaker Cura rounds the wall thickness to a multiplication of the line width. In general, a wall thickness of two or three times the line width is sufficient. A higher value will create a sturdier model and decreases the chance of leaks, while a lower value can significantly decrease the print time and filament costs.

Instead of setting a thickness in millimeters, you can also set a number of walls. When you set the wall line count, the wall thickness is calculated and will grey out.

Example: A value of 1 mm, results in three walls of 0,35mm = 1,05mm wall. The model on the left has three walls, the model on the right has two walls.

Outer wall wipe distance

At the end of every outer wall, a short path is traveled without extrusion. This results in a reduced seam when traveling from the outer wall to other parts of the 3D print. It is visible in the layer view by short travel moves right over the outer wall.


Top surface skin

Top surface skin is the top-most layer of skin, which can be adjusted separately. This allows one to print at higher quality which results in a better surface finish. It has the following settings to change:

Top surface skin extruder

The extruder can be set for the top surface skin layers. The second extruder may contain a different print core or material.

Top surface skin layers

This setting defines how many layers of all top skin layers will be affected by the setting. Two or three layers are often enough to have an improved surface quality.

Top surface skin pattern and line directions

The pattern can be set separately to get a different visual effect. If set to lines, the angle of the lines can also be set for more precise control.

Top surface print speed

The speed can be changed to enhance the print's surface quality. Print it at the same speed as the outer wall to get a smooth finish.

This model has a top surface skin pattern of horizontal lines.

Top/bottom extruder

This setting defines which extruder should print the top and bottom layers. Different colors or nozzle sizes can be used for the second extruder.


Top/bottom thickness

With the top/bottom thickness you can set the thickness of the solidly printed top and bottom layers of the print. A higher value ensures all gaps on the top and bottom layers are closed completely. However, this can also increase the print time and amount of filament used.

It is advised to always use a multiple of the layer height for the thickness of the top and bottom. This means, for example, that with a layer height of 0.15 mm, it’s better to set the top/bottom thickness to 0.6 mm rather than 0.7 mm.

Top-bottomThickness.pngThe model on the left has a top/bottom thickness of 1.4mm, the one on the right is just 0.7mm.

Separate top or bottom thickness
You can also set the thickness of the top and bottom layers separately. This is especially useful for the top as you may need a few layers to close it properly and prevent “pillowing”. By using fewer layers for the bottom you can save material and print time.

Number of top/bottom layers
Instead of setting a height in millimeters for the top or bottom layers, you can set a specific number of layers. The resulting height in millimeters will be calculated automatically depending on the layer height set. Example: Number of top layers 12 * 0.1mm layer height = 1.2mm top layer thickness.

Top/bottom pattern

Ultimaker Cura allows you to choose from different printing patterns for the top and bottom layers. These are the available patterns:

  • Concentric: The pattern is printed from the outside to the center of the print.
  • Lines: A diagonally printed pattern with travel moves on the shell of the model.
  • Zig-zag: A diagonally printed pattern with connections on the shell of the model.

TopBottomPattern.pngLines, zig-zag, concentric, and 'line direction' with custom value [90]

Bottom pattern initial layer

This refers to the pattern of the layer that is printed directly onto the build plate. It can be changed separately. Use this feature to get models with specific bottom visuals.

Top/bottom line direction

This setting allows you to change the direction in which the top and bottom skin lines are printed. Normally, they print in a diagonal direction. This is the fastest and uses both the X- and Y-motors. Changing the direction can have a visual effect. Multiple numbers can be entered to change the line direction each layer, for example: [90,0] this creates a horizontal-vertical direction.

Outer wall inset

This setting compensates the position for the outer wall, if the line width chosen is smaller than the nozzle. For example: A line width of 0.35 with a 0.40mm nozzle leaves a gap of 0.05mm on both sides of the actual printed line. A compensation of 0.025 is set to compensate for the outermost part.

Outer before inner walls

This setting determines which walls are printed first, the outer or the inner walls. When enabled, the outer walls are printed first and X-Y dimensions are more exact. The downside is that overhang quality is decreased.

Alternate extra wall

This setting adds an extra wall every other layer. This way the infill gets caught between the walls, resulting in stronger prints. For example, if you set the wall line count to two walls and enable alternate extra wall, it will print two walls on even-numbered layers and three walls on odd-numbered layers.


Compensate wall overlaps

With this setting, the extrusion on printed parts is reduced where the print head has to go over a thin area twice. This way all walls are printed without the part being over extruded. The setting can be enabled for the outer or the inner walls separately.


Fill gaps between walls

For fine details, the printer might need to print areas that are thinner than the nozzle size. This can happen between the outer and inner walls where the model ends in sharp corners. This option allows these gaps to be filled after printing both walls. The illustration shows a droplet which has to be printed.

Note: See how the fill gaps option influences the travel moves. The printer has to come back to the gap at later times to fill it.


Filter out tiny gaps

Some gaps between walls are so small that the extra travel path is not worth the extra extrusion to compensate for it. Enable this feature to fill those minuscule gaps anyway, if needed.

Print thin walls

This setting allows walls to be printed that are thinner than the nozzle size. Since the nozzle cannot physically do this, the paths might still be over extruded if enabled, however, they will not be completely removed.

Horizontal expansion

Horizontal expansion can be beneficial if the tolerance of the print is important. Due to a slight deformation of plastics, the actual dimensions of the print may not completely correspond with the dimensions of the digital model. By adjusting the horizontal expansion value you can compensate for this slight deviation. A higher value will increase the X/Y size of the model, while a negative value decreases the X/Y size.

HorizontalExpansion.pngThis model with a screw-hole has been expanded -0.1mm, 0mm, +0.1mm

Initial layer horizontal expansion

This feature has the exact same effect as horizontal expansion, except that it is only applied to the layer printed on the build plate. This may help in overcoming over extrusion on the first layer, increasing the dimensional accuracy. A value of half the line width is advised.

Hole horizontal expansion

This feature has the exact same effect as horizontal expansion, except that is it only applied to closed holes on the X,Y plane of every layer, and not on the outside part of the model. This may help overcome screw holes that shrink too much and need to be compensated for.

Note: Where horizontal expansion adds material with a positive value, this feature removes material with a positive value. Example: A value of 1 will make the hole bigger by 1mm in every direction!

Z-seam alignment

This setting allows you to choose where each new layer in the Z direction starts and affects where the seam of the model will be. This is useful for models with consecutive equal layers as the seam can be visible. By changing the Z-seam alignment you can decrease the visibility of the seam. The options available are:

  • User-specified: Set a coordinate for the X and Y direction of the Z-seam. This coordinate is absolute by default. Example: X 100, Y 200 will move the seam to the center back of the model.
  • Shortest: The next layer starts at the endpoint of the previous layer. This is the fastest way of printing, but also creates the most visible seam.
  • Random: The next layer starts at a random point of the previous layer, which eliminates the chance of a seam. Print time will increase due to the necessary travel moves.
  • Sharpest corner: This puts the seam in the sharpest inward or outward corner of the model, when available. This is the best method to completely hide the seam.

Seam corner preference

The Z-seam is hidden as much as possible by default. However, for some projects, specifically those that require post-processing, exposing the seam can be necessary for the post-print processing. To do so, you can adjust the following settings:

  • None: The seam will remain on the Z-seam alignment location.
  • Hide seam: The seam will be hidden as much as possible.
  • Expose seam: The seam will be exposed as much as possible.
  • Hide or expose: The seam will be hidden when possible and exposed when there is no other option.

No skin in Z gaps

Small gaps between the layers in the Z-direction of a model can be “fixed” by using this setting. Enabling it will ensure the layers will fuse together by printing infill between the bottom and top of the gap. If you disable this setting, it won’t fill the gap and will simply print the bottom and top as they appear in the model.

Extra skin wall count

By using this setting, the outermost part of the top/bottom pattern will be replaced by a number of concentric lines. Using one or two lines can improve roofs that start on infill material and ensure that they come out sturdier and with a smoother surface.


Enable ironing

Ironing is a technique where the nozzle travels over the top-most layer after printing it, to iron the top layers to a smooth surface. The settings for ironing can be adjusted to get the desired surface finish:

  • Only highest layer: This setting will apply ironing only to the very last printed layer.
  • Pattern: A pattern can be chosen to iron.
  • Line spacing: Determines the space between every line.
  • Flow: While ironing, this percentage of material is extruded on top of the last layer.
  • Inset: Ironing is applied to an offset of the outer edge of the model in the X-Y direction.
  • Speed, acceleration, and jerk: The speed of ironing can be adjusted to fine-tune the process.



Continue reading about Infill settings.

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