PLA vs ABS

Introduction

PLA and ABS are the most common materials for FDM, both these materials are thermoplastics, they can be a soft and moldable state once heated, and then return into a solid state once cooled. In the FDM process, these two plastic will be melted and then extruded through FDM printing nozzles to build up layer by layer, and produce final parts.

We will discuss the main differences between these 2 common plastics.

ABS

ABS is the abbreviation of Acrylonitrile Butadiene Styrene, it is a common thermoplastic in the injection molding industry. It is widely applied for production like LEGO, electronic housing, automotive bumper.

PLA

PLA is the abbreviation of Polylactic Acid, it is a biodegradable thermoplastic under the according correct conditions. This plastic is derived form renewable resources such as corn starch or sugarcane. It is one of the most popular bioplastics, which is widely used for various applications from plastic cups to medical implants.

Main Properties of PLA & ABS

PropertiesABSPLA
Tensile strength27 MPa37 MPa
Elongation3.5-50%6%
Density1.0-1.4 g/㎤1.3g/㎤
Melting temperatureN/A173℃
Glass Transition Temperature105℃60℃

Parts accuracy

Normally, the 3D printed parts tolerance and accuracy in FDM process are largely dependent upon printer calibration and model complexity. Both ABS and PLA can be used for dimensional accurate parts production, the printing detail size can be down to 0.8 mm, and minimum features down to 1.2 mm. The minimum wall thickness should be 1 to 2 mm, in order to guarantee adequate strength in wall elements. The tolerance of 0.5 mm is recommended for connecting or interlocking parts. Due to low printing temperature in FDM, comparing to ABS, PLA is less potential to warp and able to print sharper corners and features. This make PLA easier to print with than ABS.

Strength

ABS and PLA have similar tensile strength, both are adequate for various prototyping applications. ABS is often more preferred in reason of its higher ductility than PLA. As ABS has a higher flexural strength and better elongation before breaking than PLA, 3D printed ABS parts are employed for end-use application, while PLA parts are popular for rapid prototyping, its form is more critical than its function.

Surface finish and post processing

As the nature of FDM printing, both ABS and PLA materials layers are visible after printing. ABS material surface is typically a matte finish, while PLA is semi-transparent with a glossier finish.

Acetone is usually applied to smooth ABS parts surface in post processing, it will result to a glossy finish on surface. ABS can be sandblasted and drilled after printing. However, PLA printed parts require great care in sandblasting and machining process.

For aesthetic requirement, SLA or Material Jetting is recommend to produce with ABS or PLA materials.

Heat resistance

ABS has glass transition temperature of 105℃, and PLA has glass transition temperature of 60℃.

For high temperature application, ABS is more suitable than PLA. PLA will lose its structure and start to droop and deform rapidly, once it approaches temperature of 60℃, particularly in situation of under loading.

Biodegradability

PLA is stable in general atmospheric environment, it will biodegrade in industrial composition within 40 days or in water conditions with 48 hours. However, ABS is not biodegradable, it is only recyclable. PLA is widely applied for food related production, but it still need the filament manufacturer confirmation. This is recommendation of safety production.

Recommendation

ABS and PLA are both common FDM materials with similar cost. Comparing to PLA, ABS has better mechanical properties, and it is difficult to print.

PLA is the ideal material for in 3D printing with special aesthetic requirement. It is better suitable for parts with very fine details, in reason of its lower printing temperature and easier to print than ABS.

ABS is most suitable for application with strength, ductility, machinability and thermal stability requirement. We must notice that it is more prone to warping in printing process.