What Is 3D Printing?

(Why FDM is the best option for final products?)

Technical Focus | 2 May 2017

3D printing is becoming the talk of the town at the speed of wildfires.

Less known as Additive Manufacturing, 3D printing is a technology that produces three-dimensional objects with successive layers of materials controlled by computers. There are different processes used in 3D printing, and the main differences among them are the way layers are deposited to form parts, and the materials used. But all of them start with a 3D model created by Computer Aided Design (CAD). Then a software “slices” the model into layers and produces a file containing machine instructions tailored to a specific type of 3D printer building up the part layer by layer.

Current costs of metal 3D printing is so high that it doesn’t allow to produce end-use parts, except for very specific high value-added cases such as the reactor fuel nozzles of aircraft engines. However, when it comes to plastic, the technologies have developed, mature enough to deploy in a wide range of direct applications.

Here is all you need to know about it!


Four Widely Used 3D Printing Technologies

Resin-based SLA (Stereolithography)

SLA is the oldest technology in the history of 3D printing. It works by focusing an ultraviolet (UV) laser on a vat of photopolymer resin, solidifying the UV-sensitive resin layer by layer. SLA-printed products are known for impeccable surface quality and high detail precision. This technology is widely used in the production of dental mould. However, it is hardly used for printing final products due to UV alteration of the material over time.

Powder-based SLS (Selective Laser Sintering)

SLS uses laser beams to heat up the certain areas that need to be bonded together on a fine powder platform while the rest of the platform remains loose powder. SLS is a means of rapid prototyping and needs no support material. It is a more popular among specialist as both the equipment (high powered laser) and consumables (micro-sized powder) require sophisticated environment and procedures to operate safely.

Filament-based FDM (Fused deposition modelling)

The same as other processes, FDM starts with CAD model. Receiving the instruction, the printer will heat up the thermoplastic filaments into melting point before extruding it throughout nozzle onto the print bed. FDM is considered simple-to-use and eco-friendly, widely applied in multiple industries such as automobile, food and beverage sector etc. Different kinds of thermoplastic used in FDM include ABS and PC filaments which are both functional and durable.

Jet Spray – PolyJet

PolyJet 3D printers work similarly to inkjet printers, but rather than jet drops of ink, PolyJet 3D printers jet UV-cures tiny droplets of liquid photopolymer. PolyJet technology is known for its capability of building a single piece of 3D part with multiple types of materials and colors. It enables fine details and ultra-thin walls as fine as 16 microns, which means it is able to build very precise and high-quality surface parts. PolyJet is mainly thriving in film, fashion and medical industries.

       (image: New Equipment Digest)


Let’s compare the technologies!

Technologies FDM SLA SLS PolyJet
Materials Durability

+

+

Strength

+ +

Safety

+

+

Costs Consumables cost

+ +

+

Machines cost

= +

=

Operation cost

+ +

+

Printer Capabilities Printing speed

+ =

+

Resolution

=

+ =

+

Surface quality

+ =

+

(Note: “+”: high      “=”: average      “-“: low )

A quick guide to choose the technology smartly:

  • Choose FDM for any production with reasonable accuracy requirements and average to high mechanical requirements.
  • Choose SLA for quick production requiring high level of accuracy and low durability, example: dental moulds.
  • Choose SLS for very high added value parts with high mechanical requirements and durability, example: aerospace.
  • Choose PolyJet for small, highly detailed prototypes and master patterns, example: film props.

Why FDM is the best option for the majority of end-use products?

Reason One: materials

FDM builds parts in the same strong and durable plastics used in plastic injection, CNC machining and other traditional manufacturing methods. There is a large variety of materials available for FDM printers at cheap prices, while resins for SLA and powders for SLS are expensive and hazardous. Companies are familiar with the FDM materials and therefore are more confident in introducing an innovative technology that uses the same material. They can skip the time-consuming material requalification process when implementing 3D printing, and eventually shorten the process of changing the production method.

On the other hand, SLA and Jet Spray technologies uses photopolymer which has never been used in traditional manufacturing and does not provide any assurance in terms of durability. SLS uses almost exclusively nylon, largely limiting the variety of products and applications.

Technology FDM SLA SLS PolyJet
Materials ABS, PC, PLA, Nylon (polymers) Liquid UV-sensitive resins (photopolymers) Usually polyamide (Nylon), metal Liquid UV-sensitive resins (photopolymers)

Reason Two: cost effectiveness

FDM is the most cost-effective technology for now among the four mostly used 3D printing technologies for 3 reasons.

  1. Low CAPEX: in comparison to SLA, SLS and PolyJet, FDM printers can be respectively up to 10 and 100 time cheaper (FDM: 1K$, SLA – Jet Spray: 10K$, SLS: 100K$)
  1. Inexpensive consumables: materials used in FDM are cheap and accessible as already fully standardized and commoditized thanks to the plastic injection industry.

e.g. 1 kg of filament can be bought for $10 and even cheaper when purchased in large volumes, while the powder for SLS costs about $100 per kg, the resin used in SLA from $150 per litre, and the resin for Jet Spray from $300 per kg.

  1. Low operational costs: thanks to the low cost of machines, more and more “print farms” are developing using multiple printers at the same time. Even though the FDM printing speed is limited compare to the other technologies, the print farms allow to lower significantly the labour costs which is the main impact on operations costs. For example, VOODOO Manufacturing, currently employ one technician to manage 40 printers and seek to further automatize the printer management to reach a ratio of 400 printers per employee. (read VOODOO article here)

Thanks to its cost effectiveness, FDM is economically viable to produce end-use parts by 3D printing in place of plastic injection, especially for small-to-medium volume production.

And what about quality finishing

Quality is an issue as whole when talking about a manufacturing solution. We will soon publish a study performed together with TUV-SUD dedicated to that topic to show how we ensure that FDM produced parts systematically reach the technical specifications of Home Appliance products.

To sum it up, FDM is definitely the cheapest 3D printing process as well as the one which provides the best level of quality assurance for a wide variety of end-use parts.

This is the reason why, at Spare Parts 3D, so far we choose FDM to print plastic spare parts.