PLA vs. ABS: what’s the difference?

PLA and ABS are 2 of the most common FDM printing materials. Both are thermoplastic, meaning they enter a soft, moldable state when heated and then return to a solid state when cooled. Through the FDM process, both are melted and then extruded through a nozzle to build up the layers that create a final part. This article will discuss the main differences between the two common materials.

What are ABS and PLA?

ABS (acrylonitrile butadiene styrene) is a common thermoplastic material well known in the injection molding industry. It is used for applications such as LEGO, electronic housings and car protection parts.

PLA (polylactic acid) is a biodegradable (under the right conditions) thermoplastic material derived from renewable resources such as corn starch or sugar cane. It is one of the most popular bioplastic materials, used for many applications from plastic cups to medical implants.

Accuracy of one part

In general, the tolerance limits and accuracy of FDM printed components are highly dependent on printer calibration and model complexity. However, ABS and PLA can be used to create parts with exact dimensions, printing details as small as 0.8mm and features as small as 1.2mm. For connecting or interlocking parts we recommend a tolerance of 0.5 mm and the use of a minimum wall thickness of 1-2 mm, which will ensure adequate resistance of the wall elements.

Because of its lower printing temperature, PLA, when properly cooled, is less likely to warp (making it easier to use in printing) and can print both corners and other features sharper than ABS.

Energy

With similar tensile strengths, ABS and PLA are both suitable for many prototyping applications. ABS is often preferred due to its better ductility than PLA. With higher flexural strength and better elongation before breaking, 3D printed ABS can be used for end-use applications, while PLA is better for rapid prototyping when form is more important than function.

Surface finishing and post-processing

The nature of FDM printing means that for both ABS and PLA, the print layers will be visible after printing. ABS typically prints with a matte finish, while PLA is semi-transparent, often resulting in a glossier finish

Acetone is often used in post-processing to smooth ABS, also giving the part a glossy finish. ABS can be easily sanded and is often machined (e.g. drilled) after printing. AND PLA can also be sanded and machined, however more care is required.

If the appearance of a part is extremely important, we recommend printing using SLA or material setup.

An acetone-treated 100-micron ABS print (left), a 100-micron ABS print (center), and a 200-micron ABS print (right).

Heat resistance

For high-temperature applications, ABS (glass transition temperature of 105 °C) is more suitable than PLA (glass transition temperature of 60 °C). PLA can quickly lose its structural integrity and begin to warp, especially when subjected to stress when it approaches 60°C.

Biodegradability

PLA is stable in general atmospheric conditions and will biodegrade within 50 days in industrial composters and 48 months in water. ABS is not biodegradable, but it is recyclable. PLA is regularly used to make food-related products, however it is recommended to obtain confirmation from the filament manufacturer that it is safe.

PLA prototypes for the food industry

Basic rules

• • ABS and PLA are the most common materials used in FDM technology and usually have similar costs.

• • ABS has superior mechanical properties but is more difficult to print than PLA.

• • PLA is ideal for 3D prints where aesthetics are important.

• • Due to the lower printing temperature it is easier to print and therefore more suitable for parts with fine details.

• • ABS is best suited for applications where strength, ductility, workability and thermal stability are required. ABS is more prone to deformation.