An important part of desktop FDM printers is the nozzle. Nozzles are categorized in several ways. Some of the most important factors to consider when choosing a nozzle are the size, material, and shape of the nozzle.
The diameter of the nozzle is, perhaps, the most important factor when choosing a nozzle. This is because of how much it affects the resolution of the print. The size directly dictates the horizontal resolution and affects the layer thickness, which determines vertical resolution.
Standard Sized Nozzles
The most common nozzle size, which is included with most printers, is .4 mm. This size is a good trade-off between resolution and speed. As a nozzle gets larger, the layer thickness increases, which decreases resolution but increases the print speed. As a nozzle gets smaller, the layer thickness decreases, which increases resolution but decreases print speed. A .4 mm nozzle rests between these two sides, which gives it both decent print speed and resolution.
Larger Sized Nozzles
While .4 mm is a more standard size, nozzles with much larger diameters are commercially available. A .8 mm nozzle is considered very large, but there are companies that make nozzles with diameters up to 1.2 mm.
Increased Speed and Composite Filaments
With a larger nozzle, it takes less layers to complete a print, which makes for quicker printing. This makes larger nozzles better for rapid prototyping. In addition, larger nozzles can be extremely useful when printing with composite filaments such as glass-fill, wood-fill, metal-fill, or other exotic filaments. This is because the large particles within the filament can easily clog smaller nozzles. A larger nozzle is also easier to unclog.
Loss of Resolution and Heat
The main disadvantage of a larger nozzle diameter is the loss of resolution. Since the nozzle is large, the vertical resolution decreases, which make larger nozzles more feasible for projects where details are less important. One other factor with large nozzles is the loss of heat. For nozzles larger than 1.0 mm, the filament may not heat thoroughly due to the wide nozzle diameter and the quicker flow rate.
Smaller Sized Nozzles
These nozzles are typically sized around .35 mm and can be as small as .15 mm. In fact, some companies are now experimenting with nozzles as small as .1 mm.
The main advantages for smaller nozzles are the increased resolution. Since smaller nozzles print with a thinner layer thickness, the printer can print with much finer details. However, certain printers are not always compatible with a smaller nozzle diameter. Some printers cannot print with the lower layer thickness that a smaller nozzle requires.
Better Infills and Supports
The smaller nozzle also allows for better infills and better support removal. A smaller nozzle can print much finer walls for a print, which results in infills that use less filament. Additionally, a smaller nozzle can print supports that are very fine. This allows for a clean and easy separation of the supports.
Slower Print Speed
The print speed for smaller nozzles is a large disadvantage. A smaller nozzle has a smaller layer thickness, which means that a print will require more layers and will take more time to print. For example, printing with a .25 mm nozzle could take up to three times longer than printing with a standard .4 mm nozzle.
Smaller nozzles are also much more likely to clog, especially when using low quality filaments or filaments that are not pure plastic such as glass-fill, wood-fill, and metal-fill. High quality PLA is needed when printing with a smaller nozzle to ensure that it does not clog.
Another important factor in the selection of 3D printer nozzles is the material that the nozzles are made from. Some of the most popular options are brass and steel, but there are also other options.
One of the most common nozzle materials is brass. Most printers come with a brass nozzle, and there are a few reasons for this. For one, brass nozzles are generally cheaper than most other nozzles. Fargo 3D Printing lists most brass nozzles at $7-9. This is because brass is relatively easy to machine.
Additionally, brass is a good thermal conductor, which means it is easy to maintain a consistent extrusion temperature. Brass is also corrosion resistant. This helps lengthen the lifespan of the nozzle.
Brass is a reasonably durable metal as well. It is a soft metal, but can hold up very well when non-abrasive filaments are used. However, these nozzles will easily wear down if used with abrasive materials such as glass-fill, fiberglass-fill, or carbon fiber filaments. In fact, brass nozzles can wear down significantly after printing as little as half a kilogram of abrasive filament.
The next most common nozzle material is steel. There are two different types of steel nozzles: hardened and stainless. These nozzles are a step above brass nozzles and are specially designed for abrasive filaments. They are best used with filled filaments or carbon fiber filaments. This allows them to use a wider range of filaments more effectively than brass nozzles.
Additionally, stainless steel nozzles have the added benefit of being able to print both medical grade and food grade prints. However, very few filaments are food or medical safe. There are a few filaments that have been approved by the FDA, and if you are looking for food safe prints, this would be the way to go.
While steel nozzles do hold up to abrasion much better than brass nozzles do, they do have one disadvantage. Steel nozzles cannot conduct heat as well. However, this is generally not a problem unless a very large nozzle diameter is being used.
In addition to Brass and Steel, there are also several other nozzle materials. These include copper, aluminum, tungsten, and ruby. While these do have different properties, they do not necessarily print any better than a brass or steel nozzle.
The last key factor with determining which nozzle to choose is the shape of the nozzle. Some different shape styles include the length and the width of the nozzle nose. One factor that can be important for some printers is the mass of the nozzle. Some nozzle shapes use less metal than others, which reduces the weight of the print head. This can be beneficial for Delta printers or other printers that need a lighter print head.
There are two different nose lengths when it comes to nozzles: short and long. With a short nose, the filament must travel a shorter distance after it is melted and before it is extruded. This gives the filament less time to cool before it leaves the nozzle. Conversely, a long-nosed nozzle has more distance for the filament to travel before it is extruded, which gives it more time to cool. A long nose will also result in a print that is slightly more ridged because the filament cools quicker once it is extruded.
There are two different nozzle widths: broad and narrow. When using a broad nose, there is a slight change in the surface quality of the top of the print. However, there is also some detail lost with a broader nose since the nozzle is wide enough to transfer heat to the already extruded filament. With a narrow nose, there is only one disadvantage. The extruded filament may bulge outwards and upwards, especially when using a low layer height.
Which Should You Choose?
Ultimately, which type of nozzle you choose depends on what you are looking to do with your printer. Projects that need finer details are best done with a smaller nozzle diameter, while a larger nozzle diameter would work well with project where speed is needed. Otherwise, a standard .4 mm nozzle should work.
If printing with abrasives, then a steel nozzle would be the best choice. If you want you print food safe objects, then stainless steel is the best option. For most other filaments or projects, a brass nozzle will do the job nicely.
As for nozzle shape, it depends mostly on what printer you are using and what nozzles are available for that printer. However, nozzle shape is the least important of these three categories. Choosing a nozzle based solely on the diameter and the material is the best option most of the time.