Nozzle size and impact on printing

  1. Introduction

Nozzle width is a much-discussed problem on 3D FDM printers.

Most 3D printers come standard with a 0.4 mm nozzle. This means that the outlet of the printed plastic strip has a diameter of 0.4 mm.

The diameter of the nozzle is particularly important when we want to influence the maximum layer height and define the quality of details on the upper layers.

2. Low-level

Minimum layer height

The minimum layer height we can define for our printer is NEVER determined by the diameter of the nozzle, but only by the minimum movement of our printer's Z axis.

This is popularly known as 'the magic number'.
If we look at most of the FDM printers sold, they all use a stepper motor and propeller shaft to define the Z axis.

The minimum movement of the Z-axis is therefore determined by the number of steps the motor can make within 1 rotation and the step of the screw (screw pitch).

The most common stepper motors for the Z-axis drive have a step of 1.8°, which means that the minimum switch-on action is 1 command for the stepper motor 1.8 degrees, or that the motor needs 200 steps to perform 1 complete rotation.

Looking at the threaded rod used on the Z-axis, this is usually (on the most common printers like Creality) an 8 mm pitch screw. This means that if we were to put a nut on that screw and turn the screw a full rotation, the nut would have moved 8 mm along the threaded screw.

So the minimum movement of our printer Z-axis is 8 mm / rotation divided by 200 steps / rotation = 0.04 mm / step

3D printers with advanced stepper motor drivers (like TMS2208, TMS2209,...) can do micro-stepping, which means they can position somewhere between two steps by sending a differential signal to position the motor somewhere between two steps, but it must be said, the accuracy is never as high as when using full steps.

Maximum layer height

The maximum layer height, on the other hand, is definitely determined by the diameter of our mouthpiece:

If we were to define layer heights above 70% of the nozzle diameter, the layers would no longer adhere as much, due to the rounding on the printed filament.

It is therefore recommended never to print layer heights above 0.28 mm when printing with a 0.4 mm.


3. Overall impact of nozzle diameter on printing

As we have seen in the previous chapter, the diameter of the mouthpiece will determine the maximum layer height that can be chosen in order to still have a good layer attachment.

As the layer height can be directly related to the speed at which a print is finished (the thicker the layers, the fewer layers need to be printed for the same item), the diameter of the nozzle will have an even greater impact, as the wall thickness will also change with the diameter of the nozzle:

For the same wall thickness (let us assume 2.4 mm walls), the number of walls would be for different nozzle diameters:

Diameter of the mouthpieceWall thicknessNumber of walls
0.2 mm2.4 mm12
0.4 mm2.4 mm6
0.6 mm2.4 mm4
0.8 mm2.4 mm3

As we can see from the table above, the thicker the diameter of the nozzle, the fewer walls we need to achieve the same wall thickness and thus print those items much faster.

Examples of slicing with different nozzle diameters and layer heights:

In the table below we do an exercise where we slice the same part, with the same basic settings regarding print speed, fill percentage and wall thickness in mm. Top and bottom are always printed with 4 layers (will also vary in thickness due to layer height)

We will only change the diameter of the nozzle and the layer height and see what impact t his has on the overall print time.

REMEMBER: thicker nozzle diameters will also have an impact on the printed infill, because the infill lines have the width of the nozzle diameter and are therefore thicker when using a larger nozzle diameter.

The layer height will always be a multiplication of 0.04 (the magic number for Z)

Nozzle diameterMax Layer Height (0.7 * Nozzle diameter)Layer HeightWall thickness (mm)Number of wall linesPrint duration
0,20,140,122,4125h 30 min
0,40,280,122,463h 5min
0,40,280,22,462h 2min
0,40,280,282,461h 36min
0,60,420,22,441h 33min
0,60,420,282,441h 13min
0,60,420,42,440h 58min
0,80,560,22,431h 18min
0,80,560,282,431h 01min
0,80,560,42,430h 48min
0,80,560,562,430h 39min

When using the same layer thickness but changing nozzle width, the printing time will change because we need less walls as the nozzle diameter gets thicker.