Selecting Nozzle Sizes for Detail Prints

There’s a tendency to think that using a smaller nozzle size yields better detail. That’s true to an extent. It is difficult to print details in the XY (horizontal) plane smaller than your nozzle size, so fine details do require a smaller nozzle to print reliably. However, the converse is also true. A nozzle small enough to pick out the detail can usually print that detail just as well as a smaller nozzle. You don’t gain anything by going any smaller than required.

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.

We’ll start with a part with detail in the XY (horizontal) plane that we want to capture:

Part with horizontal detail

Fig. 27 Part with horizontal detail

There are two detail areas that we want to pick out for highlighting:

  1. The bolts on the geared idler wheel at the front.
  2. The vertical bars on the wheel mechanisms (bogeys).

We can see these results using Slic3r Prusa Edition in Preview mode.

Todo

Add printed results.

The impact of nozzle size on print detail

Here are the results sliced using a 0.40mm nozzle at 0.10mm layer height:

0.40mm nozzle detail at 0.10mm layer height

Fig. 28 0.40mm nozzle detail at 0.10mm layer height

The 0.40mm nozzle is simply too large to pick out the bolts and vertical bars we’re after. With a much larger nozzle, we’d be at risk of not being able to print the tracks, resulting in a very flimsy part. Print time is just under an hour.

Here are the results with a 0.35mm nozzle at 0.10mm layer height:

0.35mm nozzle detail at 0.10mm layer height

Fig. 29 0.35mm nozzle detail at 0.10mm layer height

With a 0.35mm nozzle, we’re able to pick out the bolts, but the vertical bars are still missing. Print time has increased to 1 hour and 8 minutes.

Here are the results with a 0.30mm nozzle at 0.10mm layer height:

0.30mm nozzle detail at 0.10mm layer height

Fig. 30 0.30mm nozzle detail at 0.10mm layer height

With a 0.30mm nozzle, we can pick out the bolts and vertical bars nicely. The squished springs at the top of the wheel assemblies is incomplete though. Print time has remained almost the same, just shy of 1 hour and 8 minutes. I suspect the difference is due to the slicer having to back track to fill in small gaps with the 0.35mm nozzle.

Here are the results with a 0.25mm nozzle at 0.10mm layer height:

0.25mm nozzle detail at 0.10mm layer height

Fig. 31 0.25mm nozzle detail at 0.10mm layer height

With a 0.25mm nozzle, we can pick out the bolts and vertical bars, as well as the squished springs, with ease. Print time has increased to 1 hour 32m, slowing down our job significantly, but all the desired detail is there.

Here are the results with a 0.20mm nozzle at 0.10mm layer height:

0.20mm nozzle detail at 0.10mm layer height

Fig. 32 0.20mm nozzle detail at 0.10mm layer height

At 0.20mm width, things still look good, but print times are now up to 1 hour 55m for no significant gain in actual visible detail. Have we really gained anything?

Here are the results with a 0.15mm nozzle at 0.10mm layer height:

0.15mm nozzle detail at 0.10mm layer height

Fig. 33 0.15mm nozzle detail at 0.10mm layer height

With a 0.15mm nozzle, we’re at the peak of FDM precision using today’s consumer technologies. Detail is clearly visible, yet we’re paying a significant price time-wise at 2 hours and 13m.

Right-sizing nozzle sizes for XY detail

In this example the 0.25mm nozzle seems to be the best balance of XY plane detail and speed. Here’s a closer comparison using our ultra-fine 0.15mm nozzle and the “right” sized 0.25mm nozzle:

0.15mm nozzle detail at 0.10mm layer height

Fig. 34 0.15mm nozzle detail at 0.10mm layer height

0.25mm nozzle detail at 0.10mm layer height

Fig. 35 0.25mm nozzle detail at 0.10mm layer height

The smaller nozzle doesn’t add appreciable detail and takes more than 40 minutes longer to print even on this small part. More importantly, the part printed with the larger nozzle will be significantly stronger and durable in use.

Right-sizing layer heights for Z detail

The same factors come into play when selecting layer heights. Thinner layer heights only help if there’s actual detail or resolution that impacts the final print. Here’s our model printed using a 0.30mm nozzle at 0.20mm layer height, double the previous example:

0.25mm nozzle detail at 0.20mm layer height

Fig. 36 0.25mm nozzle detail at 0.20mm layer height

Print time has dropped roughly 30m, and the part will be stronger. Visually, they’re nearly identical, especially once they’re primed and painted and put on the gaming table.

Adaptive layer heights and nozzle sizes

Some slicers are starting to incorporate adaptive layer heights, allowing each layer to vary depending on the amount of detail. As of Nov 11, 2018, Slic3r Prusa Edition only provides this as a manual feature, requiring the user to manually select layers for finer detail. Cura and KISSlicer provide automatic adaptive layer features that let the slicer vary layer height based on the curvature of vertical surfaces. KISSlicer takes this the furthest, with very granular control over the amount of overlap between adjacent layers, and allowing separate models on the build plate to use varying layer heights.

Consider your nozzle size if you plan on using adaptive layer heights. Remember that the nozzle will affect the lowest and highest layer heights. If you want to benefit the most from this features, you want to print thick layers as much as possible to reduce print times, while still being able to achieve low layer heights for vertical detail. Using an unnecessarily fine nozzle may greatly reduce the range of available heights. Here are examples using a maximum layer height of 80% of nozzle size:

  • A 0.15mm nozzle can print up to 0.12mm layers.
  • A 0.25mm nozzle can print up to 0.20mm layers.

Todo

Add pages for additional slicers.

Conclusions

In short, use a nozzle small enough to pick up the details you want to show, but no smaller:

  1. There is no benefit to printing with a finer nozzle than required. Show the detail you want, but there’s nothing gained by going smaller.
  2. The same thinking goes for layer heights. Thin enough to show the detail, but no thinner than necessary.

Print times suffer significantly as your reduce nozzle size and layer heights, and parts are significantly more fragile

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 Nov 11, 2018