Polylactic Acid (PLA)
PLA is the material most commonly used by the 3D printing community. This is primarily because it is an environmentally friendly, low-cost material that can be used for many types of projects. From a printing perspective, it has the fewest requirements; it does not explicitly need a heated bed to produce high-quality prints, it can be printed at relatively low temperatures and it is far less likely to warp (when the printed shape contracts and deforms after cooling, causing parts of the print to lift off the build surface).

Why you would print with PLA:

As mentioned above, PLA is a low-cost material and provides adequate strength and durability for most projects. It is also available in a wide range of colours, so you'll be able to find the perfect shade for your product.

Examples:

Indoor decorative items, figurines, phone stands, indoor plant pots, etc.

Why you would not print with PLA:

PLA has a low heat resistance so if your product is expected to be used in high temperatures (up to 50 degrees C) or outdoors for a prolonged period of time, PLA is not recommended. For example, if you are planning to leave the product in the car for an extended period of time, PLA can deform on a hot day. Also, PLA is not flexible so if this is what you need from your product, PLA may not be up to the job.

Acrylonitrile Butadiene Styrene (ABS)

ABS is also a popular material used in products where more durability is required; the most well-known example is its use by LEGO. Although it is not as strong as PLA, it is tough, with increased impact and wear resistance. However, it can be a challenge to print with ABS compared to PLA, due to its tendency to warp and its increased hardware and storage requirements (a heated bed is recommended to aid the first layer adhering to the build surface and airtight storage is required when the filament is not in use due to its hygroscopic properties).

Why you would print with ABS:

ABS would be used for a product that needs to withstand high temperatures (up to 90 degrees C) or one that needs to be tough and durable. It is also a relatively low-cost material, therefore an ideal material if you’re looking to produce products in large batches whilst keeping costs to a minimum.

Examples:

Outdoor decorative items, toys, blocks, etc.

Why you would not print with ABS:

ABS would not be the ideal choice of material if you need your product to be strong and rigid. Other materials (such as PLA and carbon fibre-filled nylon) would also be a better choice if you require a high degree of dimensional accuracy for your product.

Glycolized Polyester (PETG)

PETG has increased in popularity over the last few years. This is because it combines the strength of PLA with the durability and impact-resistance of ABS. PETG is commonly used in the manufacture of water bottles which points us towards another one of its properties; water resistance. It is easier to print than ABS, with minimal warpage and allows for greater dimensional accuracy.

Why you would print with PETG:

If you require your product to be semi-flexible, water resistant and have a smooth surface, then PETG is the material to use. 

Examples:

Indoor and outdoor decorative items, plant pots, snap-fit parts, water bottles, mechanical parts, etc.

Why you would not print with PETG:

PETG does not have the temperature resistant qualities of ABS, so if your product needs to handle temperatures between 80-100 degrees C then ABS may be the better option. It is also relatively flexible, so if you require your product to be completely rigid, PETG may not be the right choice.

Thermoplastic Polyurethane (TPU)

TPU is a flexible thermoplastic used in cases where fatigue-resistance and flexibility are the most important properties for a product. It also has great impact resistance and is often used as a vibration-dampening aid. However, it can be difficult to print with and often needs to be printed at a slow speed to get the best results. As with ABS, TPU also requires airtight storage when the filament is not in use due to its hygroscopic properties.

Why you would print with TPU:

If your product needs to be flexible and fatigue-resistant or it's primary use is related to vibration-dampening or shock absorption then TPU would be the material that best fits your requirements.

Examples:

Remote-controlled car tires, phone cases, door stops, flexible toys, etc.

Why you would not print with TPU:

if you require your product to be rigid and hold a significant amount of weight then TPU will not be the right material to use due to its flexible properties. It does not have a particularly high temperature resistance (up to around 70 degrees C) and detailed prints using TPU can also be a challenge to get right.

Other Fun Filaments

Wood-Filled PLA:

This type of material is a mixture of PLA and wood dust / cork. Objects printed with wood-filled PLA have a wooden look and feel. This material isn't particularly abrasive and so it can be printed with a standard brass nozzle. However it can cause clogs over time, so a larger nozzle size is recommended.

Glow in the Dark PLA:

As the name suggests, this material has glow-in-the-dark properties which can make for some amazing prints. However, be aware that this material is highly abrasive and can ruin a brass nozzle very quickly (i.e. potentially within one print). Your printer should be fitted with a hardened steel nozzle before printing with this material.

Marble PLA:

This material attempts to emulate the look of marble, and does so fairly well in my opinion. It is not abrasive so a standard brass nozzle can be used. However, there may be some difficulties experienced when printing the first layer, so using this material may take a few tests before you get this right.

Metal-Filled PLA:

As you can guess, this material is a mixture of PLA and fine metal powder. The metal powder can range from copper and brass to steel, and many others depending on the manufacturer. This is another highly abrasive material so your printer should be fitted with a hardened steel nozzle before use.

Carbon Fibre-Filled Nylon:

This material brings the properties of nylon and carbon fibre together; nylon is impact and abrasion-resistant, as well as being tough and fairly flexible. Adding carbon fibre to it significantly increases its strength and stiffness. This gives products printed with this material a variety of strengths, as well as a unique look and feel. Again, carbon fibre is highly abrasive so your printer should be fitted with a hardened steel nozzle before printing this material.

What to watch out for when you are using exotic filaments:

Some of these filaments can be printed without too many additional requirements, but others will require special attention in terms of slicer settings and in some cases specific hardware as well. Make sure you take the necessary precautions to avoid damaging your printer.