Resin vs. FDM: 3D Print Strengths Compared

You can make 3D printed models from a variety of materials, such as acrylonitrile butadiene styrene (ABS), high-density polyethylene (HDPE), and polylactic acid (PLA). Arguably, resin and fused deposition modeling (FDM) prints top the most commonly used materials list. But how do they compare in terms of strength?

FDM prints are generally stronger than 3D resin prints. Specifically, the tensile strength of FDM prints ranges from 38-64MPa, while those of resins are generally lower at 23-55Mpa. Also, FDM prints have higher flexural strengths at 2.1-7.6GPa, while resins only average at 60.6MPa.

This article will compare the strengths of 3D printing resins with those of FDM materials. Read on for in-depth information on their tensile strength, flexural strength, elongation at break, and other mechanical properties like density and glass transition temperature.

A Comparison of the Strengths of Resin and FDM Prints

As I mentioned, FDM prints are generally stronger than resins. Notably, the former’s tensile and flexural strengths are higher than the latter.

Let’s explore their strengths and other mechanical properties in detail:

Tensile Strength

Tensile strength measures the amount of force required to pull an object apart. The higher the number, the stronger the material.

This measurement is generally measured in Pascals but is sometimes reported in megaPascals, MPa or GPa.

It’s a crucial consideration when selecting materials for an application. Specifically, materials with higher tensile strengths are well suited for applications where forces will be applied.

Flexural Strength (Bend Test)

The flexural strength measures the material’s ability to withstand bending without breaking. This property is important when considering applications with repeated impacts on one plane, like gear teeth and chain links.

It’s also crucial because it may affect the print head and layers bonding together during printing. Generally, the higher the value, the better – after all, you don’t want your models or objects to break.

The flexural strength of FDM prints ranges from 2.1-7.6GPa, while resins only have a value of 60.6Mpa. Therefore, FDM prints are stronger than resins compared using this metric.

Elongation at Break

This property measures a material’s ability to deform before it breaks. This measurement is different from the tensile strength, which only measures how strong a material is in one direction.

The elongation value tells you about the extent of deformation when disengaged. It’s a good indicator of flexibility.

In general, resins are more flexible than FDM prints.

Notably, the elongation of resins ranges from 8% to 50%, while FDM prints range between 3.5% and 50%.

Glass Transition Temperature

This property refers to the temperature at which materials undergo physical transformations like becoming flexible.

All polymers have a glass transition temperature, but not all are equal due to the numerous chemical combinations used in 3D printing filaments. For instance, the average for resins is 73°C (163.4°F) compared with 60-105°C (140-221°F) for FDM.

Density

The density of a material refers to the mass per unit volume.

Materials with higher densities are more heavy-duty and provide better contrast for what you’re trying to print. This can increase build quality, but it does add some weight.

Typically, FDM prints have a density of 1.0-1.4 grams per cubic cm (29.57-41.40 grams per fl oz), while resins average at 1.2 grams per cubic cm (35.48 grams per fl oz).

Melting Point

This property measures a material’s ability to withstand high temperatures without degrading.

Typically, FDM prints have a melting point of 173°C (343°F) compared to resins’ average of 150°C (302°F). Because of that, FDM prints are more suitable for industrial applications.

Key Takeaway:  A comparison of the strengths indicates that FDM prints are stronger than resins. Moreover, Tg values for resins are relatively low while FDM’s are higher. As a result, FDM printers can print with materials with higher melting points.

On the other hand, Resin printers have a lower glass transition temperature. This means they’re more flexible and can be used for applications where print flexibility is a deciding factor.

That said, this video demonstrates how FDM nuts and bolts are stronger than resin nuts and bolts:

3D Resins vs. FDM: Pros and Cons

Pros of 3D Resins

Highly Accurate

3D Resin prints are highly accurate in part geometry and even surpass FDM in accuracy. Because of that, the parts themselves are very functional.

For example, resin 3D printers produce better results than FDM when printing an injection mold.

In the former case, there are no strings or other excess material inside the mold, and it has very precise walls and flow channels.

This is because of how 3D resins work: first, you start with a liquid, usually made from two different chemicals which, when mixed, react to form solid layers via a process called photopolymerization.

Because of this, 3D Resin prints are great for printing molds due to their precision parts.

High-Resolution Parts and Are Flexible

3D Resin prints have very high resolution along the Z-axis (the direction that goes up and down far surpassing FDM’s), which leads to very smooth surfaces at microscopic levels.

In addition, 3D resins are very flexible and resilient because there’s no chance of warping during the printing process. This makes resin prints capable of achieving high strength-to-weight ratios compared to FDM prints.

Cons of 3D Resins

Potential Complications With Post-Processing

3D Resin printers use photopolymerization to harden their parts, which means post-processing has more steps than an FDM printer.

First, you must wash away the unhardened chemical to not affect other layers during printing. Then you need to sand or otherwise remove any excess material until your part is ready for use–sometimes even mechanically.

More Expensive but Weaker Than FDM

Although some FDM printers are more expensive than some resin printers, resin printing is typically much more expensive than FDM. This is because the printer is more complicated internally, using far more components than FDM printers.

While more expensive, if printed at the same resolution as an FDM printer, a resin print would likely be weaker than its FDM equivalent. As I mentioned earlier, FDM prints generally have higher tensile and flexural strengths.

High Maintenance

Because 3D Resin printers are more complex internally, they are also much more expensive to maintain in general.

Before you order your first printer, you should always ask yourself what you plan to use it for since there are many types of resins. 

Their properties vary greatly across brands and grades – some are better suited for certain purposes than others.

Pros of FDM Prints

Less Expensive

FDM printers are generally less expensive than most resin 3D printers. Therefore, FDM printers are better for schools, libraries, or individuals shopping on a budget.

This makes FDM the best and practical option for those starting out with 3D printing.

Stronger Option

From the discussion above, FDM prints are stronger than resin prints.

This is because of two reasons:

• FDM printers use plastics with higher tensile and flexural strengths.
• The lower resolution means there are fewer chances for weaknesses along the printed part.

Faster Prints

Parts from FDM printers tend to build quickly and without much post-processing. This is because:

• FDM printers can use standard filaments like ABS and PLA, which are already strong enough for most purposes, but with FDM, you don’t need as high a resolution as resin printers typically require.
• Both ABS and PLA only require limited support structures during the printing process, which means more area is available to print on, making for faster prints.

Cons of FDM Printers

Lower Resolution

FDM prints are only as good as their resolution, which is around 50-400 microns. This means that printed parts of FDM printers won’t be smooth at microscopic levels. Depending on your printer’s settings, this can be reduced, but it’ll always leave a roughness.

Limited Customization

FDM printers print using a process called Fused Filament Fabrication.

This means that instead of printing droplets from resins, the machine uses a filament to create layers on top of each other, building up your part.

The problem with this is that you cannot customize these filaments beyond color and strength.

Because of this, while some specialty filaments may work in FDM printers for some applications, they won’t always give you what you want because their properties don’t meet your requirements.

Crucial Factors To Consider When Choosing 3D Print Material

Now that you know some of the pros and cons of FDM prints let’s discuss some crucial factors to consider when choosing 3D print material.

Heat Resistance

High heat resistance is essential for many objects that’ll be put into daily use. 3D printed parts that won’t break or warp at high temperatures are much more useful than those that will. Therefore, it’s important to look for materials that can withstand high temperatures.

Flexibility

It’s important to look for flexibility if your part will be exposed to movement and stress.

This can include anything from moving parts on cars, releasing tools after injection molding, to mention but a few.

If the material doesn’t have high fatigue resistance, it can break much easier than others under these circumstances.

Chemical Resistance

The 3D printed part will likely come into contact with a lot of chemicals in its lifetime.

Therefore, it’s crucial to find a material that can resist corrosion.

Look for materials with chemical resistance. Notably, they shouldn’t react with the elements and should also be resistant to chemicals like acids and bases.

If you pick materials that react with the elements, your part won’t last long, meaning more replacements. As a result, you may end up spending more and getting less value for money in the long term.

Fatigue Resistance

If you’re looking to print a moving or constantly used part, it’s important to pick one with fatigue resistance. This means that it should be able to withstand multiple impacts without easily breaking.

If you pick a material that doesn’t have fatigue resistance, it’ll break much faster under these circumstances. This can be especially problematic if you’re designing parts for machinery or tools that’ll constantly be in motion.

Precision

Some 3D printing technologies offer finer resolutions than others.

For example, FDM printers may have great accuracy with some materials but low precision with others.

However, resin 3D printing offers high-precision prints at relatively affordable costs with the correct settings. This makes them more desirable than FDM prints, which are only as good as their resolution.

Resin 3D printers are also great for printing detailed parts.

Safety

The material you choose must be safe for use around your home, family, and pets.

It’s also essential to pick a material that can release no formaldehyde to ensure the safety of those who will use it after printing.

For this reason, go with the safest material available to you. This way, you can have complete peace of mind knowing that your product is safe and won’t cause harm to your family or anyone else who may come in contact with it.

Application Area

Every object or part has different requirements depending on its application. Some may need high-temperature resistance, whereas others may need fine detail.

This is why it’s important to consider the area where you’ll use your part and what it would need to withstand before printing it. Only then can you make an informed decision about 3D printer material selection that gives you the best possible outcome for your needs.

Once you decide on the material type, the next step is to narrow down to specific resins. In that regard, here are some options to consider that are available on Amazon.com:

• Recommended resin: ELEGOO Water Washable 3D Printer Resin (notable selling points include exceptional precision, quality pigments, and fast curing).
• Recommended FDM: SUNLUU PLA 3D Printer Filament (notable selling points include great layer adhesion, a smooth finish, and remarkable strength).

The Bottom Line

When it comes to choosing 3D printer material, there are many things to consider. I’ve talked about the properties of FDM and resin and given you some crucial considerations to keep in mind before making a decision.

Here’s a roundup of the key takeaways:

• FDM prints are generally stronger and withstand higher temperatures than resins.
• Resins offer better resolution and experience less warping.
• Consider where you’ll use the print and what it needs to withstand before choosing the material to use.