The Ultimate Guide to FDM 3D Printing and Material Selection

Choosing the right filament is an important part of getting a successful FDM 3D print. While PLA is often the obvious starting point, different materials offer very different levels of strength, flexibility, temperature resistance, durability and surface finish.

The best material depends on what the part needs to do, how it will be used and what you want the finished part to look like.

At Print My Part, we regularly help customers select the most appropriate material for prototypes, functional components and one-off replacement parts. Here are some of the key factors to consider.

What is FDM 3D printing?

FDM (Fused Deposition Modelling) is one of the most widely used forms of 3D printing. The process works by heating a plastic filament and depositing it layer by layer to create the finished component.

FDM is particularly useful for:

• Functional prototypes

• Concept models

• Enclosures and housings

• Jigs and fixtures

• Replacement parts

• Low-volume components

• Testing product designs before manufacture

One of the advantages of FDM is the wide range of engineering materials available. However, choosing the right one can be difficult if you're not familiar with their properties.

PLA – Great for prototypes and visual models

PLA (Polylactic Acid) is one of the easiest materials to print and is often the first choice for general-purpose prototypes.

It produces good dimensional accuracy and a relatively clean surface finish, making it particularly useful when you're primarily interested in checking the size, shape and appearance of a design.

Advantages

• Easy to print

• Good dimensional accuracy

• Good surface finish

• Relatively inexpensive

• Available in a huge range of colours

• Good for visual prototypes

• 
  

Limitations

PLA isn't usually the best choice for functional components that will experience significant heat, impact or long-term outdoor exposure.

It has a relatively low heat resistance and can soften or deform when exposed to elevated temperatures.

Best for: concept models, visual prototypes, fit checks and general-purpose parts.

PETG – A good all-round functional material

PETG is often a good step up from PLA when you need a prototype to perform some real-world function.

It offers a useful combination of strength, toughness and temperature resistance while remaining relatively straightforward to print.

PETG is also more resistant to moisture and many chemicals than PLA.

Advantages

• Good strength

• Good impact resistance

• Better temperature resistance than PLA

• Good chemical resistance

• Suitable for functional prototypes

• Relatively easy to print

• 
  

Limitations

PETG can be more prone to stringing than PLA and doesn't always produce quite as crisp a surface finish.

Best for: functional prototypes, brackets, housings, fixtures and general engineering parts.

ABS – Tough and suitable for demanding applications

ABS has been used in engineering applications for many years and remains a popular FDM material.

It offers good toughness and better temperature resistance than PLA and PETG, making it suitable for components that may experience higher temperatures or impact.

However, ABS can be more difficult to print successfully because it is prone to warping and requires careful control of the printing environment.

Advantages

• Good impact resistance

• Good temperature resistance

• Tough

• Suitable for functional components

• Can be post-processed relatively easily

• 
  

Limitations

• More difficult to print

• Prone to warping

• Requires good temperature control

• Can produce fumes during printing

  
  

Best for: functional prototypes, automotive components, housings and parts exposed to higher temperatures.

ASA – Better for outdoor applications

ASA is similar to ABS but has improved resistance to UV exposure and weathering.

This makes it particularly useful when a component will be used outdoors.

For example, if you're developing a replacement bracket, enclosure or mounting component that will spend its life outside, ASA may be more appropriate than PLA or ABS.

Advantages

• Good UV resistance

• Good weather resistance

• Good impact resistance

• Good temperature resistance

• Suitable for outdoor applications

• 
  

Limitations

• More difficult to print than PLA or PETG

• Can warp

• Benefits from an enclosed printer

  
  

Best for: outdoor components, automotive parts, enclosures and products exposed to sunlight.

TPU – When you need flexibility

Not every component needs to be rigid.

TPU is a flexible filament that can be used to produce rubber-like components such as:

• Seals

• Gaskets

• Protective covers

• Flexible hinges

• Grips

• Feet

• Shock-absorbing components

TPU is available in different hardnesses, allowing the flexibility of the finished component to be varied.

The downside is that flexible materials can be more challenging to print, particularly at higher speeds.

Best for: flexible and impact-absorbing components.

Nylon – For demanding functional parts

Nylon is an engineering-grade material offering high toughness, good wear resistance and excellent mechanical performance.

It can be particularly useful for components such as gears, brackets, clips and mechanical parts that will experience repeated loading.

However, nylon is more demanding to print and is highly hygroscopic, meaning it absorbs moisture from the atmosphere. Proper drying and storage are therefore important.

Best for: mechanically loaded components, wear parts, clips, brackets and engineering prototypes.

Don't just choose a material based on strength

One of the most common mistakes when selecting a filament is simply asking:

"Which material is strongest?"

Strength is only one consideration.

For a real product, you may also need to consider:

Temperature

Will the component be exposed to heat?

A material that works perfectly well in an office environment may deform inside a vehicle on a hot summer's day.

UV exposure

Will the part be exposed to sunlight?

If so, UV resistance may be more important than ultimate strength.

Impact

Does the part need to withstand being dropped or knocked?

A tough material may be more appropriate than a stiff but brittle material.

Flexibility

Does the component need to bend?

TPU or another flexible material may be more suitable than a rigid engineering plastic.

Wear

Will two components repeatedly rub against each other?

Material choice becomes particularly important for moving components and mechanical assemblies.

Surface finish

Do you need a visually attractive prototype, or is the component purely functional?

PLA can often produce an excellent-looking prototype, while an engineering material may be more appropriate for a functional test.

Consider the printing process as well

The material isn't the only factor that affects the performance of an FDM component.

Print orientation, layer height, wall thickness, infill and geometry can all have a significant effect on the finished part.

For example, FDM components are inherently anisotropic because they are built layer by layer. A part may therefore behave differently when loaded across the layers compared with along the layers.

This means that simply selecting a strong material doesn't automatically result in a strong component.

The part should be designed and orientated with the intended loads in mind.

Which FDM filament should you choose?

As a general starting point:

Material	Good for	Main advantage
PLA	Visual prototypes	Easy to print and good finish
PETG	Functional prototypes	Good all-round performance
ABS	Engineering parts	Toughness and temperature resistance
ASA	Outdoor parts	UV and weather resistance
TPU	Flexible components	Elasticity and impact absorption
Nylon	Mechanical components	Toughness and wear resistance

There isn't one "best" filament. The right material depends on what the part needs to achieve.

Need help choosing the right material?

If you're unsure which material is appropriate for your component, you don't necessarily need to make the decision yourself.

At Print My Part, we can consider the intended application, loads, environment, required finish and quantity before recommending an appropriate material and manufacturing process.

For some projects, FDM will be the ideal solution. For others, MJF, SLA, SLS, CNC machining, vacuum casting or injection moulding may provide a better result.

The important thing is to select the manufacturing process and material based on what the part actually needs to do — rather than simply choosing the cheapest or most readily available option.

Have a part you need designing or manufacturing? Get in touch and we can recommend the most appropriate approach for your project.