If you’re looking to purchase your first 3D printer, upgrade your existing machine, or simply learn more about the printing industry right now, you’ve come to the right post. While Stereo Lithography, Laser Sintering, and Powder Printing techniques are going strong, Fused Deposit Modeling (FDM) and PolyJet are the current leaders of the 3D printing pack. However, though both FDM and PolyJet each assemble 3D models layer by layer, the materials, processes, and benefits differ greatly.
Let’s break it down.
What’s the Difference Between FDM and PolyJet 3D Printing Technology?
FDM uses a thermoplastic filament and extrudes material in a continuous bead of semi-molten material from a print head. Once deposited, set and cooled, a new layer is formed. This process then repeats many times over to produce the final part. PolyJet, on the other hand, uses liquid polymers. These are jetted in liquid form from a carriage (with accuracy as fine as 0.1 mm) onto the work space and cured through UV light exposure. As with FDM, the process is repeated until the part is fully formed.
FDM models can undoubtedly withstand higher temperatures than PolyJet, making them generally more robust and durable. There’s also the option to choose from varying thermoplastics that can withstand everything from extreme temperature to harsh chemicals. FDM is therefore better suited to printing models that are larger, functional, or require mechanical/industrial strength.
Director of Brown University’s Design Workshop, Christopher Bull, described FDM as, “quick, inexpensive, and widely available.”
“It fits when there's a need for a relatively low fidelity prototype, perhaps early in a design project,” according to Bull.
Eric Bredin, VP of Marketing EMEA at global 3D printing leader Stratasys, says that with FDM, “manufacturers can use a range of high performance thermoplastics to produce extremely durable parts for full-functional testing and production applications.”
“These include a range of tough ABS materials, ASA, advanced ULTEM 9085 and 1010 resins, and carbon-filled nylon. The ULTEM materials in particular provide high strength-to-weight ratio and are FST (flame, smoke, and toxicity) compliant, ideal for aircraft interior applications.”
However, because the layers tend to be thicker with FDM, they can sometimes be visible.
What’s more, Associate Professor of Additive Layer Manufacturing Group at the University of Warwick, Dr. Gregory J Gibbons, says some FDM materials also require manual removal of the support structure.
“This limits the ability to manufacture complex parts,” Gibbons said. “Also, part accuracy is compromised for systems that do not have a heated chamber, usually the low cost or very large envelope system.”
PolyJet is suited to more detailed or finer textured parts such as concept models, prototypes, consumer products, and electronics. Models can be rigid, flexible, transparent, opaque, or coloured – a major advantage to the technique.
For example, faced with time consuming design processes, Italian eyewear designer Safilo produces photorealistic frames 60 percent faster than traditional prototyping methods by using PolyJet techniques. Designers can create functional parts without assembly or painting, allowing for more design iterations early in the design process and unlocking creative freedom amongst designers.
However, Gibbons points out that: “With PolyJet, you can only build using acrylate resins, which have poor thermal tolerance and do not fully replicate the properties of the end use product materials.”
Cost and Dimensions
The initial purchase cost for FDM and PolyJet is roughly the same, but the usage varies considerably.
With FDM, parts are constructed from material that’s already semi-solid when deposited, making it a relatively “supported” system. So, FDM requires fewer support structures and less raw material than PolyJet.
While FDM printers will need a continual supply of nozzles and build trays, PolyJet machines may need to have their print heads replaced after every 2,000 hours of use. Subsequently, PolyJet can prove more expensive in the long run.
While PolyJet provides “higher fidelity” and “a wider range of materials that gets the designer closer to fully functional models,” FDM works better in a student workshop environment because of its greater cost efficiency, according to Bull.
“At Brown, we are educating engineers and we primarily use FDM machines so students can beat on them, take them apart and re-configure, without us worrying too much about the cost.”
Both PolyJet and FDM technologies offer similar sizes for the maximum part size from a single system. PolyJet parts can be built up to 39.3 x 31.4 x 19.6 in. and FDM parts can be built up to 36 x 24 x 36 in.
However, with FDM, if your part is larger than the FDM dimensions, the design file can be split into multiple sections, with each piece built on a separate machine and then bonded together. The model then has the strength and functionality of a single part.
What Does the Future Hold for FDM and PolyJet?
We will continue to see “further development of high performance thermoplastics” used in FDM machines, says Gibbons. However, there is competition on the horizon.
“FDM may struggle to survive against the competition provided by the new higher rate technologies such as HP Jet Fusion,” he said.
“With PolyJet, there may be more functional use of the digital printing capability to improve the performance of parts, for example, the ability to impart different thermal or electrical properties selectively into the parts.”
Increasing user demands will force 3D printing technologies to develop over time, says Bull.
“Users will always ask for higher resolution, a wider range of materials, and lower cost, so I think the printing technology will continue to evolve to provide the resolution. Rapid prototyping materials is an active research topic, and I'm hopeful that the range will expand. In terms of cost, there might be some new business models that help drive down the per part cost while maintaining the convenience of having in-house fabrication.”
Stratasys say they are continually looking to the future.
“We’re helping future-ready leaders advance their industries through innovation specifically fit for purpose,” said Bredin.
“We are already seeing a growing demand for large-scale, production systems for aerospace and automotive manufacturing. This is exemplified by recent previews of our innovative 3D demonstrators based on next generation FDM technology, including the Stratasys Infinite-Build 3D Demonstrator developed in collaboration with Boeing and Ford, and the Robotic Composite 3D Demonstrator, designed in conjunction with Siemens.
“Turning 3D printing on its side, the Stratasys Infinite-Build 3D Demonstrator can produce prototypes, tools and production parts of infinite length and optimised specifically for large-scale, lightweight manufacturing applications. For industries dependant on tough, lightweight composite materials, the Robotic Composite 3D Demonstrator combines additive manufacturing and a 7-axis robotic system to produce cost-effective composite parts within a highly competitive timeframe.”
The recently previewed FDM-based Continuous Build 3D Demonstrator meets the future need for low-volume production and mass customization.
Composed of a modular unit with multiple 3D print cells working simultaneously, the system is driven by a central, cloud-based architecture, setting a new standard of production throughput with additive manufacturing. It automatically ejects completed parts and commences new ones. Each 3D print cell can produce a different job and more cells can be added to increase production capacity as and when demand requires.
Bredin said the technology is designed to produce parts in a continuous stream with only minor operator intervention.
In an area of such significant development and ongoing evolution, the changes within the industry are continual and complex. The transformational journey of 3D printing undoubtedly has the potential to further expand its reach and capacity in the future – and it seems to be doing just that.
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