Note: Shell and top/bottom settings are separated into two categories. The top/bottom settings can be found here.

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.

Outer wall inset

This setting causes the outer wall to be moved slightly more towards the inside.

The aim of this setting is to improve dimensional accuracy when using a line width smaller than the nozzle size. When the outer wall is printed with a smaller line than the nozzle size, the material can flow outward more than the desired line width, making the print wider than desired. Moving the outer wall slightly inside causes the nozzle to overlap with the inner walls, forcing the material in the location adjacent to the inner wall. This only works when printing the outer wall after the inner walls.

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.

Optimize wall printing order

If this is enabled, Cura will spend some extra slicing time to optimise the order in which the walls are printed. The goal is to reduce the number of travel moves and retractions by printing walls that surround the same part after one another.

The model on the left is printed as normal, the model on the right has an optimized wall printing order.

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. Printing the outer walls first improves dimensional accuracy, 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.

Minimum wall flow

Compensating for overlaps in wall lines will reduce the flow rate of some of the walls. This can be problematic, because it can reduce the flow rate arbitrarily low, down to 1% if the walls almost completely overlap. Printing at extremely low flow rates doesn't work well. It tends to form a droplet pattern instead of continuously extruding lines.

This setting will turn those lines with extremely low flow rate into travel moves, effectively snapping their flow rate to 0%. The material will still ooze out as with normal travel moves, but will not form beads.

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.

The model on the left has the option disabled, the model on the right has thin walls printed.

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.

This 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.

This model has a Z-seam positioned 'user specified' in the top left corner.

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.

Z seam relative

When the seam is placed in a user-specified location according to the 'z-seam alignment' setting, you can enter coordinates for where the seam must be located. Normally those coordinates specify some location on the build plate, such as the back of the printer. If this setting is enabled, those coordinates will be taken relative to the position of the model.

The models on the left have a Z-seam positioned on one place on the build plate, the models on the right have the seam located relative to each model individually. The input 'z-seam alignment' values are the same for both images!

Continue reading about Top/bottom settings.