7.2. 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.

7.2.1. 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.

7.2.1.1. 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.

7.2.1.2. 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.

7.2.1.2.1. 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.

7.2.1.2.2. 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.

Fig. 7.3 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.

7.2.1.3. 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.

7.2.1.3.1. 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.

7.2.1.3.2. 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.

Fig. 7.4 Maintaining width-to-height ratio for good extrusion cross section

7.2.1.3.3. Recommended minimum and maximum layer heights

Todo

update to reflect layer height based on extrusion width

Here’s a quick table showing a safe range of minimum and maximum layer heights for different nozzle sizes. I recommend starting in this range ti get familiar with new nozzles before experimenting with more extreme settings.

Table 7.1 Recommended safe minimum & maximum layer heights by nozzle size
Nozzle Size	Minimum Layer Height	Maximum Layer Height
0.15mm	0.04	0.12
0.20mm	0.05	0.16
0.25mm	0.06	0.20
0.30mm	0.08	0.24
0.35mm	0.09	0.28
0.40mm	0.10	0.32
0.50mm	0.13	0.40
0.60mm	0.15	0.48
0.80mm	0.20	0.64
1.00mm	0.25	0.80

7.2.1.4. 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:

Fig. 7.5 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:

Fig. 7.6 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:

Fig. 7.7 20mm XYZ calibration cube printed with 0.40mm nozzle at 0.20mm layer height

And the same print with a 0.80mm nozzle:

Fig. 7.8 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.

7.2.2. Print speed

The relationship between nozzle size and print speeds is complex. Most slicer software provides settings for linear speed – the amount of time to move from point A to point B – but that’s only half the story. Linear speed only affects how quickly the nozzle moves. Volumetric throughput – the amount of plastic actually laid down during a move – much more.

7.2.2.1. Understanding maximum volumetric speed (hotend throughput)

The key to successful printing at larger sizes is understanding the limitations of your printer hardware. The hotend on your printer is the part that actually heats and melts the filament. Every hotend has a limited capacity which is expressed as the “maximum volumetric speed” or rate it can handle. If you attempt to push more filament than this through the hotend, you’ll eventually encounter a variety of problems, including:

Under extrusion and uneven layers.
Extruder click and skips.
Nozzle and hotend jams.
Increased extruder motor heat.

The E3D V6 hotend that ships with the Prusa i3 Mk3 can process (melt) PLA filament through a 0.4mm nozzle at a rate of roughly 15 mm³/s, though 11.5 mm³/s is more realistic. For more information on calculating the maximum volumetric rate you can use with your hotend and nozzle, see my notes on calibrating maximum hotend volumetric rate.

Calculating maximum volumetric rates is straightforward:

$Max. Volumetric Rate = Layer Height \times Extrusion Width \times Speed$

7.2.2.2. Calculating maximum safe speeds based on volumetric speed

Given a maximum volumetric rate, layer height, and extrusion width, we can calculate a safe maximum speed:

$Max. Speed = \frac{Max. Volumetric Rate}{Layer Height \times Extrusion Width}$

Now we have to adjust the relevant slicer settings. The amount of work you have to do will depend on the slicer you’re using.

7.2.2.2.1. PrusaSlicer and maximum volumetric speeds

PrusaSlicer has some very useful settings for throttling linear speeds without having to make repetitive minute adjustments for each printed feature type. You can enter your usual print settings based on desired print quality and PrusaSlicer will throttle speeds in the generated gcode if, and only when, necessary to keep your maximum volumetric rate within the limit you set. This allows one setting to avoid a host of problems with under-extrusion, extruder skips, and nozzle jams.

7.2.2.2.2. Calculating safe maximum linear speeds with other slicers

Unfortunately, we have a bit more work to do if we want to use another slicer. We want to set layer height and extrusion width based on our print needs, trading off quality for faster print times. You first need to determine the maximum hotend volumetric rate your printer can work with using a specific filament and nozzle. This will give you an approximate “red line” value that you should not exceed to avoid hardware problems. In reality, you want to reduce this – probably by half – for print quality.

Let’s use the maximum volumetric speed of the E3D V6 hotend printing PLA through a 0.4mm nozzle of 11.5 mm³/s. We can determine the maximum safe print speed using the formula:

$Max. Speed = \frac{11.5 mm^3/s}{Extrusion Width \times Layer Height}$

Using this formula, we can calculate safe maximum linear print speeds for common nozzle sizes. Prusa recommends a maximum linear speed of 200 mm/s for the Prusa i3 Mk3, so your maximum speeds should generally stay below that.

Todo

Add print speed calculation table data

If you want to try my experimental print parameter calculation spreadsheet, feel free to give it a try here. If you have any problems using it, please let me know using one of the contacts listed at the bottom of this page.

7.2.2.3. Smaller nozzle impacts on speed

A smaller nozzle diameter limits both the layer heights and maximum extrusion widths that can be printed.

Lower layer heights dramatically increase print time.
Narrower extrusion widths increase the number of perimeters that must be printed to produce a specific wall thickness. This is somewhat offset by the ability to print at faster linear speeds with smaller nozzles.

In general, smaller nozzles are great for detail, but are slow and produce more fragile parts.

For more detail on printing with small nozzles, please refer to Selecting nozzle sizes for detailed prints.

7.2.2.4. Larger nozzle impacts on speed

A larger nozzle diameter expands the maximum layer heights and extrusion widths that can be printed.

Thicker layers allow much faster printing, particularly when using single-wall vase mode prints. This is a tremendous benefit for tall prints with translucent materials.
Wider extrusion width means stronger walls with fewer perimeter passes. There is a penalty in much slower linear speeds are required with larger nozzles.

In general, larger nozzles are great for strong, functional parts that print quickly, but lack detail.

For more detail on printing with large nozzles, please refer to Selecting nozzle sizes for large prints.

7.2.2.5. Make it up in volume

You can lay down thicker lines and save having to print as many perimeters with a thicker nozzle. You have to print slower with a larger nozzle, but you’ll finish prints sooner by printing fewer perimeters.

To really get a sense for what’s going on, take a look at the extruder visualizer movement on this print using a 0.80mm nozzle at 0.48mm layer heights and 0.96mm wide extrusions:

For more detail on why printing slower with a larger nozzle may speed your prints up significantly, see my notes on speed.

7.2.3. 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.

7.2.3.1. 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 7.2 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

7.2.3.2. 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 7.3 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

7.2.3.3. 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 7.4 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

7.2.3.4. 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 7.5 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

7.2.4. 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.