Beyond PLA: Key Engineering Properties for Desktop FFF 3D Printing

Which engineering properties should concern desktop 3D printer operators?

Most FFF desktop 3D printer operators print everything in PLA, and there’s good reasons for that: it’s easy to print, inexpensive, readily available, and comes in basically any color you want.

But PLA is not the best material for many 3D printed applications. While it can easily print into a given shape, the situation changes when that part is actively used in real situations.

A typical example might be this: a 3D printed cup holder for the car is found to be catastrophically slumped when left out in the sun too long. It turned out that the PLA doesn’t have sufficient thermal resistance for that application.

It’s at that moment that 3D printer operators should consider thinking about the engineering properties. But what are the key properties to consider for different applications?

If you’re an engineer, you’d know all this. But if you’re not — and many Fabbaloo readers are not — then here’s a short list of some key engineering properties to consider. These properties are very often listed in the data sheets for the materials from your provider.

Glass Transition Temperature

The temperature at which the polymer transitions from a brittle, glassy state to a more pliable, rubbery state. This affects how the material behaves during printing and in the final product.

Heat Deflection Temperature

The temperature at which the polymer deforms under a specified load. This helps in understanding the thermal performance of the printed part under load — and the property that should have been investigated in the car example above.

Tensile Strength

The maximum stress the material can withstand while being stretched or pulled before breaking. This would be useful for applications where the part is being pulled.

Elastic Modulus

A measure of the material’s stiffness or rigidity. For some applications softer material is required for shock absorption, for example.

Impact Strength

The material’s ability to absorb energy and resist breakage under sudden impacts. If the part is being struck, dropped or otherwise impacted, this is important. PLA is quite brittle and tends to shatter because of this property.

Flexural Strength

The ability of the material to resist deformation under load. If you’re making a part that has to support a heavy weight, then this is the property to investigate.

Chemical Resistance

The material’s ability to resist chemical attack or degradation by solvents. If the part will be exposed to solvents or other chemicals it could degrade. In those cases you want to use a material that has strong chemical resistance.

Hydrolytic Stability

The resistance to chemical breakdown due to water exposure, important for parts exposed to humid environments, and especially for those being submerged.

Shrinkage

The reduction in size as the material cools and solidifies, which can lead to warping and dimensional inaccuracies. While this is important during printing, this might also occur in lesser degrees during operational usage should the ambient temperature vary considerably: dimensions could change.

UV Resistance

The material’s resistance to degradation when exposed to ultraviolet light. ABS in particular is susceptible to UV light, and can degrade. ASA is an alternative material with almost the same engineering properties as ABS, except that it has UV resistance.

Biodegradability

For applications where environmental impact is a concern, the ability of the polymer to degrade naturally over time. Does the material degrade on its own in a landfill, or does it require special treatment?

For a given application only a few of these properties might be important. But if you are aware of them, you can consider them when appropriate.