6.2. Nozzle Sizes

If you haven’t tried a different nozzle height yet, you’re missing half the fun. A nozzle swap is the simplest and most impactful change you can make to your 3D printer.

Prusa summed it up nicely in their YouTube video on nozzle sizes.

That’s like buying a DSLR camera and never changing the lens. It definitely works, but you’re limiting yourself.

Note

These notes are based on my experiences with the Prusa i3 Mk3 and Artillery/Evnovo Sidewinder X1 printers. If you are using a different printer, please verify the hardware details are similar.

According to the Prusa survey results, only 22% of users have tried another nozzle size, despite the fact that it’s one of the cheapest and simplest modifications you can make to an otherwise-stock 3D printer. Part of this is no doubt due to trepidation about changing something that’s working. Hopefully, I’ve gathered some notes here to set your mind at ease and expand on some of the information on working with alternate nozzle sizes on the Prusa i3 printers.

6.2.1. What changing the nozzle size does

The size of the nozzle opening influences a lot of factors that aren’t immediately obvious. It’s a good idea to understand the effects to avoid making frustrating mistakes as you experiment.

6.2.1.1. Nozzle diameter

The diameter of the nozzle opening determines resolution in the horizontal (X-Y) plane. This means that it will affect detailed features on the top surfaces of your prints. A 3D printer is going to have a difficult time printing any details smaller than the nozzle diameter.

  • If you’re doing fine detailed prints, too large of a nozzle can result in missing details and dull corners. Slicers will skip details that are too small to be printed the specified nozzle, or at best, try to approximate them.

  • If you’re printing large functional parts with minimal detail, a finer nozzle won’t gain you anything. You’ll add significant print time with no real gain. A larger nozzle will move a lot more filament in a given amount of time and significantly speed up print times.

In general, use a nozzle small enough to print the finest details in your print, but no smaller. Go as large as you can to speed up prints.

6.2.1.2. Extrusion width

Nozzle size impacts the range of extrusion widths you can print with. This affects how wide a perimeter wall is printed with a single pass.

6.2.1.2.1. Minimum extrusion widths

You can use extrusion widths narrower than your nozzle, but with some caveats:

  • The quality of thin lines may be poor, particularly for external perimeters.

  • Thin walls must also be printed with low layer heights to preserve good inter-layer adhesion. See Maximum layer heights below.

6.2.1.2.2. Maximum extrusion widths

The wider the extrusion, the fewer perimeter walls you have to print to achieve the desired wall thickness. The ability to use wider extrusion widths is one of the big wins with larger nozzles. Keeping extrusion widths to 120% or below of the nozzle size is recommended for good print finish with most nozzles.

If you are using quality nozzles, you can use considerably wider extrusions. Take a look at the E3D drawing for the V6 series nozzles and you’ll find some interesting details.

  • The A dimension in the drawing designates the diameter of the nozzle opening.

  • Unlike cheap clone nozzles, E3D uses a different thickness for material surrounding the nozzle opening, designated by the B dimension in the drawing.

The diameter of the nozzle in the B dimension varies, but is roughly double the size of the A dimension for the opening. This means that you can print at up twice the nozzle opening and still have sufficient pressure to get the squish necessary for good inter-layer adhesion. There are a couple of limitations to this:

  • Physics still apply. Speeds are still constrained by your hotend maximum volumetric rate. Reduce speeds as you increase extrusion widths or layer heights.

  • Wider external perimeters may suffer poor finish if the extrusion width exceeds the nozzle B dimension. Limiting wider extrusions to internal perimeters and infill may work best.

Nozzle squish provides better inter-layer adhesion

Fig. 6.3 Nozzle squish provides better inter-layer adhesion

Note

The C dimension of the E3D nozzles – the length of the opening – is also interesting. Theoretically, this is the optimal amount of retraction necessary to avoid oozing if you have otherwise calibrated your filament extrusion multiplier. I’ve had mixed luck with this.

6.2.1.3. Layer height

Nozzle diameter directly affects the layer heights that you can successfully print. Layer height determines resolution in the vertical (Z) plane.

  • At lower layer heights, curved vertical surfaces are smoother. Vertical detail is improved and prints look more finished.

  • At higher layer heights, vertical detail is lost but speed and strength are improved. Thick layers start to look like toothpaste.

If you’ve searched for information on layer heights, it’s very likely you’ve come across references to “magic” layer heights. Typically, these suggest using multiples of 0.04mm (e.g. 0.04mm, 0.12mm, 0.16mm) to evenly match extrusion stepper motor resolution. This is good advice, but the Prusa i3 Mk3 printer has much finer resolution. Layer heights on the Mk3 should be based on a multiple of 0.0025mm, which means that any value up to two decimal places after the decimal point is equally beneficial. Just choose any value of 0.XXmm and you’re fine. When in doubt, experiment.

6.2.1.3.1. Minimum layer heights

Keeping layer heights greater than 25% of the nozzle size is recommended, although you can experiment with this setting. There are two considerations for minimum layer heights:

  • Using too low of a layer height can create back pressure from the nozzle, creating surface blemishes and extruder skips.

  • The printer layer height minimum setting in PrusaSlicer is used to set a lower limit for adaptive variable layer heights. You want a realistic range for the slicer to use when adjusting heights automatically.

6.2.1.3.2. Maximum layer heights

FDM printing relies on adhesion between layers as filament is laid down. A certain amount of compression (squish) is desired to push the hot new layer of filament onto the cool layer below. The less squish, the less adhesion, resulting in brittle walls.

As you increase layer height, you are effectively producing extrusions with a more rounded cross-section, reducing the ratio between the height and width of the extrusion. When layer heights exceed 80% of the nozzle size, adhesion between layers is reduced.

Ultimately, your maximum layer height depends on your extrusion width. In order to maintain the desired oval or “stadium” extrusion cross section, a width-to-height ratio of roughly 3:2 works well so long as the width is less than the B dimension of the nozzle.

Maintaining width-to-height ratio for good extrusion cross section

Fig. 6.4 Maintaining width-to-height ratio for good extrusion cross section

6.2.1.4. Example prints

I cranked out some sample prints to show the effects nozzle size has on a print. These are all 20mm cubes printed with Prusa default PLA defaults, no tuning and no post-processing. Our first examples are printed with the following settings:

  • Max volumetric speed 15 mm3/s (PLA)

  • 2 perimeters

  • 20% infill

  • 0 top layers

  • 5 bottom layers

  • Default PrusaSlicer extrusion width (calculated from nozzle size)

The first example shows a cube printed with a 0.40mm nozzle:

20mm cube printed with 0.40mm nozzle

Fig. 6.5 20mm cube printed with 0.40mm nozzle at 0.20mm layer height

Next, the same model printed with the same base settings and a 0.80mm nozzle:

20mm cube printed with 0.80mm nozzle

Fig. 6.6 20mm cube printed with 0.80mm nozzle at 0.20mm layer height

The next comparison uses an XYZ calibration cube printed with the following settings:

  • Max volumetric speed 15 mm3/s (PLA)

  • 2 perimeters

  • 20% infill

  • 5 top and bottom layers

  • Default PrusaSlicer extrusion width (calculated from nozzle size)

Here are the results with a 0.40mm nozzle:

20mm XYZ calibration cube printed with 0.40mm nozzle

Fig. 6.7 20mm XYZ calibration cube printed with 0.40mm nozzle at 0.20mm layer height

And the same print with a 0.80mm nozzle:

20mm XYZ calibration cube printed with 0.80mm nozzle

Fig. 6.8 20mm XYZ calibration cube printed with 0.80mm nozzle at 0.20mm layer height

A few things to notice:

  • All printed in roughly the same amount of time (~33 minutes). While the nozzle speeds used with the larger nozzle are much slower, significantly more plastic is extruded during each move.

  • Vertical (Z) resolution is the same. A larger nozzle can still print fine layer heights within limits.

  • Horizontal (XY - top surface) resolution is much finer with the smaller nozzle. Although these prints don’t highlight it, details smaller than the nozzle size will not print reliably. The slicer simply won’t produce output for features that are too small.

  • You can see a significant difference in smoothness on top of the cube printed with the smaller nozzle. Narrower extrusion widths produce smoother and more even top surfaces.

  • Perimeter thickness is greatly increased for the same number of moves when printing with a larger nozzle. The resulting parts are significantly stronger. You can reduce the number of perimeters printed and still achieve the same wall thickness.

  • Infill is similarly thicker and stronger with larger nozzles. Less of it needs to be printed, further saving time. Not as many infill extrusions are required for the same density.

  • Corners and edges are more rounded with the larger nozzle, but not grotesquely distorted.

  • Overhangs and bridges sag more easily with larger nozzles. Heavier extrusions distort more easily.

6.2.3. Guidelines for printing with different nozzle sizes

Here are some general rules-of-thumb I’ve found reading a variety of sources:

Todo

Update with more current findings.

  • Limit extrusion widths at up to 1.2 X nozzle opening diameter. I haven’t found any suggestions for minimums, other than “close to nozzle width”. Your slicer will usually not produce output for features that are much smaller than the nozzle size.

  • Limit layer heights to between 0.25 and 0.80 X nozzle opening diameter for reliable results.

  • Keep flow rate below the E3D V6 hotend maximum of 11.5 mm3/s.

Here are some summary settings for the three most common nozzle sizes. The Prusa-provided maximum print speeds for the Prusa i3 Mk3 is 200mm/s. I have capped speeds at that rate and noted these in italics. Different layer heights are shown for each size, corresponding to the minimum and maximum recommended layer heights for each size. I’ve rounded all speeds down.

6.2.3.1. Printing with a 0.25mm Nozzle

At this size you can use very thin layers which will appear almost satin-like. Layer lines are nearly invisible. Small horizontal detail can be printed accurately.

Table 6.2 Recommended Maximum Speeds for 0.25mm Nozzle at 0.30mm Extrusion Width by Material

Layer Height

PLA (11.5 mm3/s)

PETG (8 mm3/s)

0.06mm

200 mm/s

200 mm/s

0.10mm

200 mm/s

200 mm/s

0.15mm

200 mm/s

177 mm/s

0.20mm

191 mm/s

133 mm/s

6.2.3.2. Printing with a 0.40mm Nozzle

This is the default nozzle size, with a good balance of horizontal and vertical detail. Speeds remain high at typical detail layer heights.

Table 6.3 Recommended Maximum Speeds for 0.40mm Nozzle at 0.48mm Extrusion Width by Material

Layer Height

PLA (11.5 mm3/s)

PETG (8 mm3/s)

0.10mm

200 mm/s

166 mm/s

0.15mm

159 mm/s

111 mm/s

0.20mm

119 mm/s

83 mm/s

0.32mm

74 mm/s

52 mm/s

6.2.3.3. Printing with a 0.60mm Nozzle

As you get above 0.60mm, nozzle sizes really impact speeds and layer width. Horizontal detail is largely missing, but wide extrusions and massive layer heights allow functional parts to be printed quickly. You’ll notice the extruder moving much faster.

Table 6.4 Recommended Maximum Speeds for 0.60mm Nozzle at 0.72mm Extrusion Width by Material

Layer Height

PLA (11.5 mm3/s)

PETG (8 mm3/s)

0.15mm

106 mm/s

74 mm/s

0.20mm

79 mm/s

55 mm/s

0.32mm

49 mm/s

34 mm/s

0.48mm

33 mm/s

23 mm/s

6.2.3.4. Printing with a 1.00mm Nozzle

At larger layer heights, print lines start to look like toothpaste. The result is almost a 3D 8 bit appearance. Some have likened it to turning anti-aliasing off. Printing at this volume really isn’t practical for the Prusa i3 Mk3, but the results are certainly interesting. The extruder wheel spins like a ferris wheel when printing at this size.

Table 6.5 Recommended Maximum Speeds for 1.00mm Nozzle at 0.8mm Extrusion Width by Material

Layer Height

PLA (11.5 mm3/s)

PETG (8 mm3/s)

0.32mm

29 mm/s

20 mm/s

0.48mm

19 mm/s

13 mm/s

0.64mm

14 mm/s

10 mm/s

0.80mm

11 mm/s

8 mm/s

6.2.4. Conclusions

If I weren’t switching back and forth between trying out miniatures and functional prints, I’d leave a 0.60mm hardened steel nozzle mounted most of the time. For a lot of prints, it’s hard to tell the difference between a 0.60mm and a 0.40mm nozzle if you use the same layer heights. You gain the flexibility of printing 0.48mm wide extrusions with 0.32mm thick. Those wider extrusions can cut down on the number of perimeters and thicker layers can reduce the number of layers that need to be printed.

In short: Use a nozzle small enough to pick up the details you want to show, but no smaller. There is no benefit to printing at a higher resolution than required, and print times suffer significantly as your reduce nozzle size. The same thinking goes for layer heights. Thin enough to show the detail, but no thinner than necessary. Don’t let using a larger nozzle keep you from using lower layer heights where it makes sense.

Contact and feedback

You can find me on the Prusa support forums or Reddit where I lurk in many of the 3D printing-related subreddits. I occasionally drop into the Official Prusa 3D discord server where I can be reached as bobstro (bobstro#9830). You can email me directly at projects@ttlexceeded.com.

Last modified Apr 2, 2021. Last build on Apr 19, 2021.