FDM 3D printers work by extruding melted thermoplastic in order to build up 3D objects one layer at a time.
Many different types of plastic are available for 3D printing but the two most popular are ABS (Acrylonitrile Butadiene Styrene) and PLA (Polylactic Acid).
A recent poll I ran in my 3D Printing Facebook Group revealed that twice as many people preferred PLA to ABS. Even though the survey sample size was quite small, this is a result I’ve seen before and is probably because PLA is generally more user friendly than ABS.
However, different filament types are more suited to different 3D printing jobs, so it’s important to discuss the pros and cons of ABS and PLA, so you can decide which to use for your specific 3D printing requirements.
Ease of Use
As I mentioned a minute ago, PLA is popular mostly because it’s so easy to 3D print with. ABS is more prone to shrinking, warping and cracking so the failure rate for ABS 3D prints is higher than for PLA.
PLA is made from organic materials so also smells more pleasant when 3D printing. ABS is a petroleum based plastic so can smell quite nasty.
As PLA is less prone to shrinking, warping and cracking it can also be used without a heated bed, whereas ABS needs one to 3D print successfully. This means that PLA can be used with cheaper and simpler 3D printers.
When it comes to visual qualities PLA generally scores a little higher than ABS. PLA is translucent and can have a very glossy finish to it if good quality material is used. PLA can also be used to print finer details and sharper edges than ABS.
Both ABS and PLA can be sanded and machined if needed after 3D printing, but ABS is slightly easier to post process. ABS can also be vapour polished using acetone fumes if a glossy finish is required.
If aesthetics are a main criteria for your 3D printing project, then maybe FDM printing isn’t the right solution and other technologies like Selective Laser Sintering or Photopolymerization might be more appropriate. You can Outsource Your 3D Printing to a service company if you need to use these more expensive technologies for the occasional project.
PLA usually scores a little higher for tensile strength, but the ‘elongation at break’ is about the same as for ABS. Elongation at break is the maximum length an object stretches before it breaks.
One of the main reasons why people would use ABS rather than PLA is due to it’s impact resistance. PLA is quite brittle but ABS is more impact resistant.
If you’re looking for strength rather than aesthetics then ABS might be a better material to use than PLA.
As well as strength, there are other qualities we need to look at when assessing a materials durability.
Remember that whether a material is porous or not, the nature of FDM printing and layer lines means that the final product will likely by quite porous anyway.
PLA is UV resistant, whereas the surface of ABS can degrade when exposed to UV light. I have however heard reports that PLA can fade slightly if left in direct sunlight for long periods of time.
See also the sections below on layer adhesion, heat resistance and biodegradability.
Whilst ABS is considered stronger than PLA, the layer adhesion is generally lower. This has an impact when Orientating Your 3D Designs before printing, because if strength is needed along the layer lines then you might need to flip the object 90 degrees if possible, or use PLA instead of ABS.
If you need a high level of heat resistance then using any type of thermoplastic probably isn’t a good solution. Due to the very nature of thermoplastics they melt when heated, so you might want to consider printing in metals or ceramics.
Should you only need a small degree of heat resistance then ABS might be sufficient. With a glass transition temperature (where a material ceases to be brittle) of 105 degrees Celsius ABS is much more heat resistant than PLA, which has a glass transition temperature of only 60 degrees Celsius.
Interestingly the actual melting point of PLA (when it becomes liquid) is 175 degrees Celsius, but ABS doesn’t have a specific melting point as it’s amorphous. This means it’s melting point varies widely depending on a number of different factors and happens gradually.
Whatever thermoplastic you use, remember that in direct sunlight objects can become quite hot and PLA can soften and lose it’s shape very easily. Consider using a lighter colour which will help reflect heat and light, keeping the object cooler in use.
PLA is made from organic materials like corn starch or sugar cane so is biodegradable under the right circumstances. For example it can degrade significantly in water in a matter of a few years.
ABS is petroleum based so isn’t biodegradable. This is one reason why PLA is more Environmentally Friendly than ABS. As well as being made from organically sustainable materials, PLA won’t damage the environment so much when it’s disposed of.
When comparing prices between ABS and PLA they both vary widely depending on the quality of the filament. However, PLA is usually slightly more expensive, but the cost difference is so minimal that other pros and cons should take a higher priority than any small Potential Cost Savings.
The toxicity of different 3D printing materials isn’t very well understood at the moment, but as more research is undertaken and results become available this may be a big issue in the near future.
This also applies to the fumes emitted when the plastics are heated and melted.
As we mentioned earlier, vapour polishing can be used to reduce the layer lines and create a glossy finish on ABS products. Acetone is also used to fuse ABS parts together, while PLA is quite tricky to glue at all.
However, acetone is toxic and the fumes produced can be very dangerous, especially when it’s warmed to deliberately produce more of them. Acetone should always be used with caution and if possible it’s use should be avoided completely.
Even though ABS is considered more toxic than PLA, it’s still worth considering that many consumer products are already made from ABS and have been for many years, including electronics casings and even Lego bricks.
For simplicity this discussion has been limited to the two most popular filament types, ABS and PLA, but there are many other different types of filament available like PET, Nylon, TPU and PC.
As well as these there are even more compound filaments which are thermoplastics infused with wood, bronze, copper, steel, carbon, ceramic and a whole number of other interesting materials.
When it comes to making the decision between ABS and PLA though, hopefully I’ve given you enough information to make an informed decision. If in doubt, for the beginner, PLA is probably more popular due to its safety and ease of use.
Also, if you’re new to all this why not download my Free Beginners Guide to 3D Printing eBook.
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