3D Printing in Plastics

Published on 29 Jan, 2019

3D printing, one of the seven disruptive technologies of this century, is also among the top 10 technologies that are expected to transform the coming decades. The technology finds application in several industries, such as industrial aerospace & defence, consumer products, automotive parts, industrial machinery, and healthcare, to manufacture products using polymers, ceramics and metals. However, more than 70% of the market is currently dominated by 3D printing of polymer-based materials due to the ease of process, availability of material and low cost.

To print 3D parts, various technologies have been developed till date, such as Fused Deposition Modeling (FDM), Stereolithography (SLA), Selective Laser Sintering (SLS), Material Jetting (MJ), Drop on Demand (DOD), Direct Metal Laser Sintering (DMLS), Electron Beam Melting (EBM), Metal Binder Jetting, and Sand Binder Jetting. Of these, FDM and SLA are the most used. SLA was developed by 3D Systems in 1986 and FDM by Stratasys in 1988. The key reason for their adoption is that they were the early entrants in the market.

Comparison of FDM and SLA 3D Printing Technology

Over time, many technologies were developed in parallel, including several incremental innovations in FDM and SLA 3D printing technology. Today, FDM and SLA remain the leader in 3D printing of plastic materials. The two have been compared below.

Parameters

FDM

SLA

Material details

Base material

Typical thermoplastic materials used: PLA, ABS, PETG, Nylon, PEI (ULTEM), ASA, TPU

Photopolymers: Epoxy or acrylate-based resins

Material distribution method

Extrusion

Vat (tank, vessel)

Binding technique

Heat

Light (laser)

Dimensional details

Layer thickness

0.05–0.127 mm

0.05–0.015 mm

Wall thickness

1 mm

5 mm

Print volume

200 x 200 x 200 mm – desktop 1000 x 1000 x 1000 mm – industrial

145 x 145 x 175 mm – desktop 1500 x 750 x 550 mm – Industrial

Support

Not always required (dissolvable available)

Larger support required

Smallest possible detail

140 micron

250–800 micron

Quality

Printed product quality

Low to medium

High

Surface texture

Rough (“staircase” effect) but can be polished

Smooth; often shiny

Accuracy

Lowest

Highest

Mechanical failure

Gradual deformation until fracture

Almost no deformation until sudden fracture

Compatibility

 

Food compatibility

Leakage due to micro-gaps

Only with special resins (can be expensive)

Chemical compatibility

Leakage due to micro-gaps

Yet to be defined

Post processing

Object removal from bed after printing

Easy

Difficult

Applications

Low-cost rapid prototyping; basic proof-of-concept models; low-volume production of complex end-use parts

Functional prototyping; dental applications; jewellery prototyping and casting; model-making

Pros

Fast; low-cost consumer machines and materials

High value; high accuracy; smooth surface finish; range of functional applications

Cons

Warping; misalignment of layers; shrinking of lower parts; low accuracy; low details; limited design compatibility

Average build volume; sensitive to long exposure to UV light

Cost

Low cost (printers inexpensive, material inexpensive)

High cost (printer medium-priced, resins can be expensive)

Overall rating of the technology based on various parameters

4/5

 3/5

From the data, it is evident that FDM has more benefits over SLA and, hence, is widely used. Even from the latest market share perspective, FDM commands around 69% in the 3D printing market, whereas SLA has less than 15%.

A study by Wohlers Associates in 2013 revealed that around 10,000 industrial units were sold in 2013. It also showed that of the overall units sold, Stratasys, which is mainly into FDM 3D printing, had the highest market share. Referring to another study by Gartner in 2015, of the 244,533 units estimated to have been sold that year, FDM-based 3D printers (industrial + desktop) totalled 232,336 units (Industrial + Desktop) of the total 244,533 units expected to be sold that year. Hence, it can be firmly concluded that currently FDM is a highly adopted 3D printing technology for both industrial and desktop units.

FDM-based 3D printers would remain the industry standard for the next few years, given the advantages the technology has over others. Also, due to the low cost (of FDM printers as well as filament material), these printers are in huge demand in schools and universities for educational and research purposes.

Challenges of SLA & FDM Printers

  • Cost – FDM printers use nozzles and filament rolls. As most FDM printers use the same standardized filament roll, filament prices have been declining over the past few years. On average, 1 kg of PLA filament can be bought for $25. SLA printers not only use resin but the resin tank also has to be replaced after 2–3 litres of resin have been printed. Prolonged use causes smudging in the tank, making it difficult for the light source to project the image precisely on the resin. On average, resin tanks cost around $40–80. The replacement of built platform also costs around $100. Even the resin used for 3D printing costs around $80–100 a litre. Overall, SLA 3D printing technology is costlier than FDM 3D printing.
  • Material availability – Availability of materials has not been a major challenge; however, newer grades of materials, available at a lower cost and capable of imparting desired properties to end products, need to be developed. FDM printers use standard filament rolls, supplied by printer supplying companies or various other service providers. This reduces dependence on printer supplying companies and ensures the latter’s monopoly is kept under control.
  • In case of SLA 3D printing, the resin material is proprietary and cannot be interchanged between printers from different makers. This creates dependence on printer supplying companies and gives them significant pricing power.

Latest Polymer Grades Developed for SLA & FDM

Recent materials developed for FDM 3D printing technology:

  • PolyMide CoPA Nylon material – This material, introduced by Polymaker, is based on the Warp-Free technology. It improves the printability of nylon, which has been a problem in the domain.
  • Polyetheretherketone (PEEK) – It is a semi-crystalline, high-performance engineering thermoplastic. The material is rigid, opaque (grey) and combines several mechanical properties, including resistance to chemicals, wear, fatigue and creep. It also has very high resistance to heat (can withstand temperatures of up to 260°C or 480°F).
  • Polyether ketone ketone (PEKK) – It has been developed by Stratasys for industrial grade FDM printers. PEKK has both amorphous and crystalline material properties. Due to its unique mechanical, physical and chemical properties, the material can be used in a wider range of applications than PEEK.
  • Carbon fibre mix filament resin – Combining carbon fibre with filament makes the material rigid, strong and very light (in terms of weight).
  • Conductive graphene filament resin – Combining polylactic acid (PLA) with graphene, which conducts electricity, helps in printing electric circuits without the need to add wire post processing.

Recent materials developed for SLA 3D printing technology:

  • Kapton – It is an aromatic polymer comprising carbon and hydrogen that can be used to 3D print components used for insulating space craft and satellites from extreme heat and cold.
  • Nanocrystalline hydroxyapatite (nHA) polyethylene glycol diacrylate (PEGDA)/nHA‐PEGDA – The material has enhanced biocompatibility and mechanical properties.
  • Functionalized SLA resins – These graphene-based materials serve as fillers to functionalize SLA resins.

Conclusion

3D printing has been evolving over the years. Growth is mainly driven by improvements in printer technology and printing materials. Different companies are conducting research independently or in collaboration with printer supplying companies to develop better grades of materials (with improved properties) that also cost less. Currently, FDM and SLA are the two most widely used 3D printing technologies in manufacturing components in various industries using polymers. FDM 3D printing technology accounts for the major share in the market due to key advantages such as low cost and availability of material. Going forward, too, it would continue to be the market leader for rapid printing prototypes and producing other parts where accuracy as well as surface finish is not of great concern.




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