Feb 2, 2016
After tackling Maintenance and General 3D Printing Techniques, now it’s time for your next lesson from Ultimaker School. Today we’ll go through some important points about materials – literally, the building blocks of every print.
As we’re all becoming product designers, 3D printing materials are becoming more and more important. Which materials are strong? Which ones wear the fastest and which ones are flexible? How do these materials behave when being 3D printed? And do they survive the test of time? These are important questions and can determine whether your project will be a success or a failure. To get the best information I sat down with the talented Material and Processing team at Ultimaker, together with colorFabb’s expert Gijs Houdijk.
Users move onto more functional items, perhaps repairing things around the house, upgrading tools, etc. But will PLA still do the trick?
In this part you’ll read about:
- Guidelines for ABS, PLA and CPE
- Food safe 3D printing
- What material to use
- ColorFabb Specials (Woodfill, Copperfill, Bronzefill)
At the moment the most commonly used materials for 3D printing are PLA (Polylactic Acid) and ABS (Acrylonitrile Butadiene Styrene), both available as filament. Materials can be also delivered in other shapes such as pellets, resin, powder, or granules. But for FFF (Fused Filament Fabrication) 3D printing filament is the most common form.
Back in the day, 3D printing started with ABS because it was the most commonly available filament on the market. Not long after PLA reported for duty as a corn-based biodegradable and more user-friendly alternative. As you might expect, there are a lot of differing opinions about which material is the best choice for each purpose, so I’ll present you with the characteristics of each and let you be the judge. We always recommend you experiment and play around with a variety of filaments – trial and error can sometimes be the greatest teacher.
We always recommend you experiment and play around with a variety of filaments – trial and error can sometimes be the greatest teacher.
Guidelines for ABS, PLA and CPE
You may not realize it, but you’re very familiar with ABS even if you don’t own a 3D printer. ABS is the same plastic used by LEGO for their bricks. Nowadays ABS is one of the more popular materials to print with, probably because it was the pioneer material used for 3D printing. However, it has some intrinsic shortcomings that can disappoint the inexperienced user. ABS has a glass transition temperature – the temperature at which the polymer softens – of about 105˚C and the printing temperature usually varies between 230˚C and 260˚C. ABS has the tendency to shrink when it cools down and can lead to deformation (warping) and delamination (cracking) of your print. Warping occurs at the bottom of a 3D printed object and a heated bed can be used to prevent this.
Delamination can occur at higher parts of your 3D print and is more difficult to avoid. The use of an enclosed frame or a work-around to keep the flow of air out and the heat in, could help to prevent these undesired effects caused by shrinkage.
CPE and ABS are usually printed with lower speeds because of the maximum temperature of the printer (Remember my previous post? When increasing speed you must also increase temperature). The fans mounted on the side of your Ultimaker make 3D printing overhangs and small details possible, but this can worsen layer bonding. Thicker layers and bigger nozzle sizes usually create stronger objects!
Warping occurs at the bottom of a 3D printed object and a heated bed can be used to prevent this.
Deciding on what is the best temperature for your ABS print requires a more careful approach than with PLA. The temperature range over which PLA changes from a liquid to the point where it carbonizes is much larger than ABS. So for most people this means PLA is more user friendly as the exact printing temperature you choose is less crucial.
Much like a regular 2D inkjet printer a 3D printer can generate fumes when heating materials up. These fumes are not by definition harmful, but they could be a concern when printing above the maximum temperatures advised on the Material Safety Data Sheets by suppliers. Therefore, printing ABS must be done in a well-ventilated area and preferably with an additional extraction system (for example, you could use a kitchen extractor hood). In contrast to ABS, PLA is not currently known to be hazardous.
PLA and ABS are just the start
Many users have started their journey into 3D printing making lots of Yoda heads, vases, gadgets, busts and other fun prints – mostly with PLA. But at some point they get more familiar with the idea of owning a 3D printer and then they start seeing the huge potential in applying it to daily life. They'll start to move onto more functional items, perhaps repairing things around the house, upgrading tools, etc. But will PLA still do the trick? Or do you need another material with different properties? A tougher material with a higher temperature resistance? And should these be biodegradable?
ColorFabb’s expert Gijs tells us: “At colorFabb we generally like to make the distinction between functional prints and gadgets. For functional prints, we advise using durable materials such as XT and nGen, or Ultimaker’s own material CPE. PLA is a great printing material, but it’s not stabilized and it can lose mechanical properties over time, becoming brittle. Therefore it doesn’t make sense to use such a material to repair or improve things. For that you’ll need a material that will last. XT and nGen are co-polyesters from Eastman (a partner of colorFabb), designed for durable applications.”
Co-polyesters are plastics known to retain their strength, transparency and other mechanical properties even when exposed to chemicals, making them very durable. Co-polyesters can be found in markets such as medical, packaging, home appliances, consumer goods, cosmetics and many more.
Food safe 3D printing
Food safe printing is another hot topic at the moment in 3D printing. But as you can imagine, developing a material that’s safe to put in your mouth is really quite complex. The problem lies in the way a 3D model is created, and this has a huge effect on the final result. For example, melting the filament is a delicate process – if the temperature gets too high, your filament will burn up, carbonize and degrade. This has a negative effect and can even completely undermine the food safe label of the filament or pellets used to make the filament.
The way an FFF 3D printer operates makes a food safe model challenging as well. The surface of tiny layers which make up the entire model are a potential breeding ground for bacteria, which doesn’t help getting a model labelled as ‘food safe’. But this doesn’t mean it will never be possible. A lot of users are already exploring ways to smooth out all layers in various post-processing methods. Filament manufacturers are also busy developing new materials and here at Ultimaker we are working hard to make our beloved 3D printers smarter and more accurate. For example, Ultimaker CPE filament is food safe approved and the emissions of volatile compounds while printing are not harmful – as opposed to ABS that can release styrene.
The fans mounted on the side of your Ultimaker make 3D printing overhangs and small details possible, but this can worsen layer bonding. Thicker layers and bigger nozzle sizes usually create stronger objects!
What materials to use
Now that 3D printing is gaining momentum, it’s also getting the attention of many material manufacturers and the range of filaments is growing rapidly. ColorFabb takes a leading role in this growth by creating a range of materials with interesting characteristics like:
- PLA-filled filaments: WoodFill, BronzeFill, and CopperFill
- Co-polyester filaments: XT and nGen
So now it’s time for some more specific information about 3D print filaments. What is what, and when do you use it? Read on to find out.
PLA: PLA is used for its nice finish, easy and fast printing characteristics and for the large amounts of colours and varieties available. PLA is usually not as durable compared to the alternative materials. PLA can be smoothened using chloroform. The glass transition temperature for PLA is 60ºC. The ideal print temperature for PLA is between 190ºC and 210ºC and the heated bed temperature should be between 60ºC and 65ºC.
ABS: ABS can be used for mechanical parts which need to keep their strength at higher temperatures and keep their rigidity. ABS isn’t designed to be flexible, which is a benefit. ABS is more matte in appearance than other materials but it can become very shiny after acetone vapour smoothing, so it's not just for mechanical parts. However, ABS has poor chemical resistance, while CPE and XT have excellent chemical resistance, which is why ABS can be made smoother by acetone vapour. Acetone is safer – although very flammable – than the chloroform used to smoothen PLA. The glass transition temperature for ABS is 90ºC. The Ideal print temperature for ABS is between 235ºC and 250ºC. Higher is usually better. ABS tends to warp due to the cooling down of the material so some additional bed adhesion may help improve the print quality. Lowering the fan speed or even turning them off will also help. The bed temperature for ABS is 110ºC
CPE: CPE is easier to print than ABS and is very strong. It can be used for mechanical parts that do not heat up and for parts that could benefit from some flexibility. In contrary to ABS it can bend a little bit. It’s safer in terms of fumes and particle emissions while printing. It’s also chemical resistant and is said to be water-tight. CPE can’t be made smoother using chemical vapours. Transparant prints are also possible using the natural color of CPE. Using thick layers and a wider thread than your actual nozzle size (like 0.5mm extrusion with a 0.4mm nozzle) will benefit the transparency. The glass transition temperature for CPE is 75ºC. The ideal printing temperature for CPE is between 235ºC and 250ºC. Your heated bed should be dialed in at 65ºC and it is recommended to use a glue stick for additional adhesion.
Third party filaments
Thanks to Ultimaker’s open filament system you can also use third party filaments in the printer. Some examples from colorFabb are:
XT: This material is a low-odour, styrene-free 3D printing filament. ColorFabb XT is made with Eastman Amphora 1800 3D polymer, which complies with certain U.S. Food and Drug Administration (FDA) regulations for food contact applications. It also means you’ll be able to make a lot of things that are more functional, durable, efficient, attractive and exhibit superior toughness. XT does have a high processing temperature range of 240˚C/260˚C.
nGen: nGen is an all-round material suitable for most general 3D printing activities. At its core nGen is an Eastman Amphora 3300 3D polymer, which results in a good melt stability. It retains these material properties very well, which means more stable results with less waste of time and material. NGen processes at lower temperatures, 220˚C to 240˚C, than XT which makes it a good alternative for users who can’t work with XT due to its higher processing temperature range. For the best impact resistance users should opt for colorFab XT or Ultimaker’s CPE. So it's as easy to use as PLA but with XT-like mechanical properties.
Gijs Houdijk tells us more about colorFabb's special filaments:
WoodFill: WoodFill is a PLA based filament which offers makers a wood-like aesthetic and tactile experience for their 3D printed models. A lovely woodshop scent fills the room when you print with WoodFill thanks to the almost 30% woodfibres that are added to the PLA/PHA mix. The added PHA also adds a bit of flexibility to the regular PLA. The fibres don’t offer an enhanced mechanical performance but they are purely intended as an aesthetical enhancement. It is advised to print with thick layers to minimize the time WoodFill stays in the heated nozzle.
CopperFill: CopperFill is a special composite made up of 80% copper powder. This results in a material that is about four times heavier than regular PLA and has a totally different tactile experience. After printing this material can be sanded, buffed and polished to reveal the metallic particles and create a realistic copper look. The material is not conductive and not stronger then regular PLA/PHA. CopperFill is not abrasive and can be used with regular brass nozzles.
BronzeFill: BronzeFill was released as colorFabb's first metal infused filament and is a composite filament made up of roughly 80% bronze powder. This results in a material about four times heavier than regular PLA and creates a new tactile finish. If you haven’t tried metal infused filaments before, BronzeFill is the ideal candidate to start with. It’s really easy to find good printing settings for and even easier in terms of buffing and polishing. After printing this material can be sanded, buffed and polished to create a realistic bronze look. This material is not conductive either and also not stronger then regular PLA/PHA. BronzeFill is not abrasive and can be used with regular brass nozzles too.
We hope that you've gained some more insight on this subject by reading this post. It was a pleasure writing it all down for you. Thanks to Gijs Houdijk for sharing some of his knowledge with us!
If you have any further questions let us know down in the comments below.