Nozzle Sizes

Note

These notes apply to the Prusa i3 Mk3 printer. If you are using a different printer, please verify the hardware details are same. These pages may be a bit rough as I revise them and add new material. Please check back regularly for updates.

If you haven’t tried a different nozzle height yet, you’re missing half the fun. 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.

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.

What changing the nozzle size does

The diameter 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.

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 prints, too large of an opening can result in missing details. Many slicers will skip smaller details, or at best, try to approximate them. On the other hand, if you’re printing larger functional parts with minimal detail, a finer nozzle won’t gain you anything. You’ll add significant print time with no real gain.

Layer height

Nozzle diameter directly relates to 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 start to 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 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.

FDM printing relies on adhesion between layers as filament is laid down. A certain amount of squish (compression) is desired to push the hot new layer onto the cool layer below. The less squish, the less adhesion, resulting in brittle walls. As you increase layer height, you are effectively reducing the ratio between the height and width of the extrusion – the squish – and making the extrusion more round. When layer heights exceed 80% of the nozzle size, adhesion between layers is very poor. Keeping layer heights greater than 25% of the nozzle size is recommended, although you can experiment with this setting.

Table 1 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

Extrusion width

Nozzle size also impacts extrusion width. This affects what details can be printed as noted above, but also affects how wide a perimeter wall is printed with a single pass. The wider the extrusion, the fewer perimeter walls that must be printed to achieve the desired wall thickness. Limiting extrusion to up to 120% of the nozzle size is recommended. Narrower extrusions can be used, but beware the effect of reducing the ratio of extrusion width to layer height as noted above.

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 Slic3rPE 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. 23 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. 24 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 Slic3rPE 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. 25 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. 26 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 prints done with a larger nozzle move more slowly, they move more plastic.
  • Vertical (Z) resolution is the same. A larger nozzle can still print fine layer heights.
  • 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.
  • Perimeter thickness is greatly increased for the same number of moves. The resulting parts are significantly stronger. You can reduce the number of perimters 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.

Calculating maximum safe speeds based on volumetric speed

Slic3r Prusa Edition and maximum volumetric speeds

Slic3r Prusa Edition has some very useful settings for throttling linear speeds without having to make repetitive minute adjustments for each printed feature type.

Calculating safe maximum linear speeds with other slicers

Layer height and extrusion width are going to be selected based on our print needs. Since we also know the maximum volumetric speed of the E3D V6 hotend is 11.5 mm3/s, we can determine the maximum safe print speed using the forumula:

Max. Speed = 11.5 mm3/s / (Extrusion Width X 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 you maximum speeds should generally stay below that.

In the tables below, a range of layer heights have been selected appropriate to the nozzle opening diameter. Speeds that exceed 200 mm/s are capped and shown italicized.

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.

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.

Selecting nozzle materials

Nozzle materials don’t have an immediatelly obvious impact on prints, but they do vary signifcantly in cost.

Plain brass

Brass nozzles are the most common and inexpensive. Brass has good heat transfer characteristics, so moves filament efficiently. Brass is a relatively soft material, so can be worn away when printing abrasive materials such as glow-in-the-dark, carbon fiber or other filled filaments. Brass works well at all sizes, and the nozzles are inexpensive enough to try several sizes without a significant investment. I’ll usually try a plain brass nozzle for experimenting with different settings.

Stainless steel

Stainless steel nozzles are really meant for producing food-safe prints, and don’t gain the average user anything. They cost more and don’t provide any benefit.

Nickel-plated copper

Nickel-plated copper nozzles have better heat transfer characteristics than plain brass, and the nickel coating is less “sticky”. Sticky materials like PETG are less likely to stick to the nozzle, so may be easier to print with. In my experience, this makes no real difference. Costs are between plain brass and hardened steel. I use nickel-plated copper nozzles for nozzles smaller than 0.40mm.

Hardened steel

Hardened steel nozzles are recommended if you want to try metal, wood, carbon fiber or other exotic fills. Hardened steel nozzles don’t transfer heat as well, so you may want to bump print temperatures up slightly. Hardened steel nozzles work fine for everyday printing, so I’ll mount one and use it for any materials. I use hardened steel nozzles for nozzle sizes of 0.40mm and up.

Ruby and other exotics

The Olssen Ruby nozzle is designed for printing exotic, high-temperature materials. While it can be used for printing other materials, it is an expensive way to do so. The ruby itself can be fragile. With the high cost, you’ll also be limited in the number of nozzles you can try. Hardened steel is as good an alternative in most hobbyist 3D printing situations.

Guidelines for printing with different nozzle sizes

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

  • Extrusion widths up to 1.2 X nozzle opening diameter. I haven’t found any suggestions for minimums, other than “close to nozzle width”.
  • Layer heights between 0.25 and 0.80 X nozzle opening diameter.
  • 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.

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 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

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 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

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 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

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 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

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 it and a 0.40mm nozzle if you use the same layer heights. You gain the flexibility of printing 0.48mm-thick layers when you want it, and those wider extrusions will cut down on the number of perimeters.

I prefer to buy genuine E3D nozzles for the sizes I care about.

  • For detail work:
    • 0.25mm nickel plated copper
    • 0.35mm nickel plated copper
  • For functional parts:
    • 0.40mm hardened steel
    • 0.60mm hardened steel

I’ve purchased one of the craptastic nozzle packs off Amazon for experimenting with other sizes I won’t use often. The nozzles are crude and probably will fail printing anything but PLA. They’re good enough to do a few prints with to get a feel for the differences between sizes. The included tools are very handy.

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 forums or Reddit where I lurk in many of the 3D printing-related subreddits.

Last updated on Oct 28, 2018