3D Printing

Intro

Choosing the right type of material to print a given object is becoming increasingly difficult as the 3D printing market sees the emergence of radically new materials. In FDM 3D printing, PLA and ABS have historically been the two main polymers (= type of plastic) used, but their initial dominance was mostly fortuitous. So there should not be any major road blocks for other polymers to play a key role in the future of FDM. We are now seeing new products become more popular, both pure polymers and composites. In this study, we focus on the main pure polymers that exist in the market today: PLA, ABS, PET, Nylon, TPU (Flexible) and PC. We sum up the key differences between their properties in snapshot profiles, so that users can make a quick decision about the best polymer to use for their application.

Methodology

If you are familiar with our previous studies, you know that we usually grade materials along the three main categories: mechanical performance, visual quality and process. In this case here, we decided to further break down these categories to paint a clearer picture of the polymer’s properties. The choice of material really depends on what the user wants to print, so we listed the key decision criteria needed to choose a material (other than cost and speed):

grading criteria

Ease of printing: How easy it is to print a material: bed adhesion, max printing speed, frequency of failed prints, flow accuracy, ease to feed into the printer… etc.

Visual quality: How good the finished object look. More info on how we test it here

Max stress: Maximum stress the object can undergo before breaking when slowly pulling on it.

Elongation at break: Maximum length the object has been stretched before breaking.

Impact resistance: Energy needed to break an object with a sudden impact.

Layer adhesion (isotropy): how good the adhesion between layers of material is. It is linked to “isotropy” (=uniformity in all directions): the better the layer adhesion, the more isotropic the object will be.

Heat resistance: max temperature the object can sustain before softening and deforming.

We are also providing additional information that are not captured in the diagram, for one of two reasons:

  • They are neither “good” nor “bad” in essence, they are just properties that will be suitable for some applications, and not for others, such as rigidity.

or

  • We don’t have a good quantitative assessment of it, but we know it is an important factor, such as humidity resistance or toxicity.

Results

We ranked each material along each criteria on a 1 (=low) to 5 (=high) scale. These are relative grades for the FDM process, they would probably look quite different if other manufacturing technologies were taken into account. Using the data from OptiMatter, we ranked the polymers along the different criteria considered:

chemistry comparison

Rearranging the data by polymer, here are the profiles we get:

PLA profileABS profile

PET profileNylon profileTPU profilePC profile

PLA is the easiest polymer to print and provides good visual quality. It is very rigid and actually quite strong, but is very brittle.

ABS is usually picked over PLA when higher temperature resistance and higher toughness is required.

PET is a slightly softer polymer that is well rounded and possesses interesting additional properties with few major drawbacks.

Nylon possesses great mechanical properties, and in particular the best impact resistance for a non-flexible filament. Layer adhesion can be an issue however.

TPU is mostly used for flexible applications, but its very high impact resistance can open other applications.

PC is the strongest material of all, and can be an interesting alternative to ABS as the properties are quite similar.

Conclusion

Choosing the right polymer is critical to get the right properties for a 3D printed part, especially if the part has a functional use. This article will help users find the right material depending on the properties they need. However, material suppliers also often provide blends or add additives to modify the properties of the pure polymer (e.g. adding carbon fiber to make the material stiffer). We are not addressing these more complex formulations in this article, but you can find data on some of these products in our optimization tool OptiMatter.

Disclaimer

  • The grades given in this article are for an average polymer representing the general chemistry, but the performance will vary depending on the actual product or supplier the user buys from.
  • All the data underlying our grades in this study was measured by 3D Matter, with the exception of Heat Resistance, for which we used the glass temperature given by multiple filament suppliers
  • For the sections called “Additional considerations”, we are using a combination of third-party assessments and of our own observations.
  • The Nylon type we are talking about in this article is Nylon 6, not Nylon 11 or 12.
  • Visual quality is tested without any significant post-processing. There are ways to smoothen the prints and improve the visual quality of a given polymer significantly (e.g. using acetone vapor on ABS).
  • The toxicity of 3D printing polymers is still not very well understood, and is a factor that might play a bigger role in the future. We are basing our comments regarding toxicity on one study by Azimi et al.[1]

[1] Azimi et al, Emissions of Ultrafine Particles and Volatile Organic Compounds from Commercially Available Desktop Three-Dimensional Printers with Multiple Filaments, Environmental Science & Technology, 2016

PLA and ABS (Plastic)

PLA and ABS are the most popular materials on 3D Hubs. This comparison will help you select the best option for your project.

  • ABS (Acrylonitrile Butadiene Styrene) is a common thermoplastic well known in the injection molding industry. It is used for applications such as LEGOs, electronic housings and automotive bumper parts.
  • PLA (Polylactic Acid) is a biodegradable (under the correct conditions) thermoplastic derived from renewable resources such as corn starch or sugarcane. It is one of the most popular bioplastics, used for many applications ranging from plastic cups to medical implants.

Introduction
PLA and ABS are the 2 most common FDM desktop printing materials. Both are thermoplastics meaning they enter a soft and moldable state when heated and then return to a solid when cooled. Via 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 these two commonly used materials.

The table below compares the main properties of ABS and PLA:

Properties* ABS PLA
Tensile Strength** 27 MPa 37 MPa
Elongation 3.5 – 50% 6%
Flexural Modulus 2.1 – 7.6 GPa 4 GPa
Density 1.0 – 1.4 g/cm3 1.3 g/cm3
Melting Point N/A (amorphous) 173 ℃
Biodegradable No Yes, under the correct conditions
Glass Transition Temperature 105 ℃ 60 ℃
Spool Price*** (1kg, 1.75mm, black) $USD 21.99 $USD 22.99
Common Products LEGO, electronic housings Cups, plastic bags, cutlery
Material properties of ABS vs. PLA
*Sourced from MakeItFrom
**Sourced from Optimatter for a test specimen with 100% infill, 0.2mm layer height printed in a linear pattern
*** Sourced from Amazon ABS & PLA

Part accuracy

Generally the tolerances and accuracy of FDM printed components are largely dependent upon printer calibration and model complexity. However ABS and PLA can be used to create dimensionally accurate parts, printing details down to 0.8mm and minimum features down to 1.2mm. For connecting or interlocking parts a tolerance of 0.5mm is recommended and using a minimum wall thickness of 1-2mm will ensure adequate strength and adhesion in wall elements.

Due to its lower printing temperature PLA, when properly cooled, is less likely to warp (making it easier to print with) and can print sharper corners and features compared to ABS.

Strength
With similar tensile strengths ABS and PLA are both adequate for many prototyping applications. ABS is often preferred due to its improved ductility over PLA. With a higher flexural strength and better elongation before breaking 3D printed ABS can be employed for end use applications while PLA remains popular for rapid prototyping when form is more critical than function.

Impact test of PLA vs. ABS

Surface finish and post processing
The nature of printing with FDM means that for both ABS and PLA the print layers will be visible after printing. ABS typically prints in 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 is regularly machined after printing and can easily be sanded. PLA can also be sanded and machined however greater care is required.

If the aesthetics of a part are critical then SLA or Polyjet may be more appropriate methods of 3D printing.

A 100 micron ABS print with Acetone treatment (Left), a 100 micron ABS print (middle) and a 200 micron ABS print (right).

Heat resistance

For high temperature applications ABS (with a glass transition temperature of 105°C) is more suitable than PLA. PLA has a glass transition temperature of 60 °C meaning it can rapidly lose its structural integrity and can begin to droop and deform, particularly if under load, as it approaches this temperature.

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 however it is recyclable. PLA is regularly used for the production of food related items however clarification of a PLA plastic when intended to be used in conjunction with food should be obtained from the filament manufacturer.

PLA food industry prototypes
Rules of thumb
ABS and PLA are the most common desktop FDM printed materials and are typically similar in cost.
ABS is best suited for applications where strength, ductility, machinability and thermal stability are desired. It can be used as a final functional part.
PLA is ideal for 3D prints with greater detail or sharper edges and due to its lower printing temperature can be easier to print with.

SLS Nylon

It’s the perfect all-rounder: easy design rules, strong and slightly flexible. Nylon allows for functional end products and complex designs. Its surface is a bit grainy, but it can be polished for a smooth finish.

Nylon prints are laser sintered on industrial 3D printers. The technology gives you a high degree of form freedom and you can even print moving parts in one go.

SLS Nylon is printed using Selective Laser Sintering (SLS) technology

SLS (Selective Laser Sintering) uses a laser to shape and form extremely thin layers of powdered material by melting it together one-by-one to create a solid structure.

The advantage of this process is that the excess unmelted powder acts as a support to the structure as it is being produced which allows for complex shapes to be made and no additional supports are required.

3D-Print Verfahren
SLS ist ein Druckverfahren, bei dem Objekte durch das Verschmelzen des Pulvers unter Verwendung eines Lasers Schicht für Schicht aufgebaut sind. Auf einem Pulverbett wird eine Schicht von 0,1 mm. Kunststoff dosierte Pulver. Während des Prozesses des Pulvers wird immer eine Schicht auf einer anderen Schicht mit Pulver angeordnet. In jeder Schicht wird das Pulver lokal durch einen starken Laserstrahl geschmolzen (gesintert) . Als Ergebnis wird das Pulver ausgehärtet, und erzeugt schließlich ein vollständig Objekt in 3D. Nach dem Verfahren und der Kühlung des gesamten Pulverblocks wird das Produkt aus dem Bauvolumen entnommen und das überschüssige Pulver entfernt. 3D-Druck ist dabei übrigens eine nachhaltige Technologie. Die Abfallstoffe werden auf ein Minimum reduziert und das Material wiederverwendet wird (dies bedeutet viel weniger Abfall verglichen mit herkömmlicher Herstellung).

Vorteile SLS 3D-Druck

  • SLS-Druckmodelle sind sehr stark und von hoher Qualität
  • Ideal Technik für die Erstellung von funktionalen Produkten und gut aussehenden Ansicht Modelle
  • Eine geeignete Technik für validieren von gut funktionierenden Prototypen
  • Auch Kleinserien sind mit dieser 3D-Drucktechnologie möglich
  • SLS-Druckmodelle sind auch ideal für eine Veredelung  (Farben, Beschichtung, Lackierung)

Materialien und Eigenschaften SLS

Neben Nylon (PA2200) stehen auch eine Reihe von anderen Materialien für diese 3D – Drucktechnologie zur Verfügung; wie PA1101 (elastisches Nylon), PA3200 (glasfaserverstärktes Nylon), Alumide (mit Aluminium gefülltes Nylon) und CarbonMide (mit Kohlenstoff gefülltes Nylon).

PA2200 

PA1101 

PA3200 (GF) 

Alumide 

Prime Part 

CarbonMide 

 Erweiterbarkeit  1650 MPa 1600 MPa 3200 MPa 3800 MPa 75 MPa 6100 MPa
 Zugfestigkeit  48 MPa 48 MPa 51 MPa 48 MPa 8 MPa 72 MPa

Mindestwanddicke 
0,8 mm 1 mm 1,5 mm 1,5 mm 1,5 mm 2 mm
 Schichtdicke  0,1 mm 0,12 mm 0,12 mm 0,1 mm 0,1 mm 0,15 mm
 (Druck) Farbe weiß, grau und rot weiß weiß grau metallic weiß schwarz
SLS Nylon HD

SLS Nylon is an HD Material

3D Hubs HD stands for the highest quality engineering grade 3D printing materials printed on industrial 3D printers. All Hubs that offer HD prints are certified by us first to ensure that your toughest demands are met.

HD Industrial Quality
HD prints are made on industrial machines, ensuring optimal and consistent quality

HD Reviews

At least 80% of all the HD Hub reviews need to be a full 5-star rating


HD Communications

Discuss the finer points of your print requirements directly with the Hub that knows what you need

HD Speed
HD Hubs will provide unmatched turnaround time for your 3D printing projects

More Info can be found here: SLS Nylon HD

Weitere Informationen zu den Polyamide (Kurzzeichen PA) Nylon.

Ceramic 3D-Materials

Aluminium Oxide Al2O3

Al2O3, more commonly known as alumina, is the most widely used and well researched ceramic material, attributable to its ready, worldwide availability, easy processing and low cost. Aluminium oxide is exceptionally tough and can meet most mechanical and chemical requirements.

It is preferred particularly for its high-temperature stability and extraordinary hardness, surpassed only by few materials (e.g. diamonds, SiC).

In gem-quality form it is known as the precious stones ruby and sapphire, in which the final colour appearance is produced by diffusing a low concentration of chromium and titanium into the stones.

Zirconium Oxide (zirconia) ZrO2

ZrO2 has the highest mechanical strength, with properties similar to steel (Young’s modulus, coefficient of thermal expansion), as well as very low thermal conductivity. Thanks to its excellent tribological properties, it has attracted particular attention in technology (sliding components) and in medical applications (artificial hip joints). The final properties of ZrO2 are determined by variable additions of dopants such as Y2O3, thereby widening the areas of application significantly compared to other ceramics.

ZrO2 is in a development stage. Only research jobs can be currently accepted.

Tricalcium phosphate

TCP is a biocompatible, resorbable material used in medicine to restore bone loss. It is progressively degraded diffusing nutrients that are resorbed by the surrounding tissue, and gradually replaced by new bone. Once fully degraded, the TCP implant is completely replaced by natural bone.

In order to degrade TCP and build up a new bone tissue the structure of TCM must mimic natural bone tissue. Since bone structure exhibits high interconnectivity, additive production is the only relevant production method here.