Back to Basics – Why Additive Manufacturing? What 3D Printing Technology?

Contribution by Sam Green

Additive Manufacturing (AM), often referred to as 3D Printing, has been around for at least 30 years. At some point in the 2010’s it really began to turn the corner in terms of general awareness and its adoption by mainstream manufacturers – those companies producing physical products in industries such as consumer goods, automotive, aerospace, and medical devices. Many are intimately aware of what additive is and the different benefits conveyed to an array of applications, and some may not be. This blog series is intended as a back-to-basics approach if you’re looking to make some sense of the many different things you may have read or seen about AM. Furthermore, this series will help you make a more informed choice if you’re at the stage of looking to select the 3D printing technology that’s right for your specific needs.

At the heart of AM is the value it can deliver to the product development process. Why? Because that’s where the greatest pressures in terms of efficiency and effectiveness are being applied in many parts of the manufacturing world today. And as a result, that’s where AM has the most to offer.

To illustrate the point this chart showcases a simple fact - that vehicle longevity is getting shorter. For light vehicles introduced during the 1980s, they typically lasted 8.6 years before the introduction of new innovations. Today that number is down to 6.7 years. And the same trend has occurred for cars and trucks. This indicates that the overall life of the product goes down, meaning there is a need for a 22% faster development process, compared to in the 1980s.

Basically, the industry today is expected to recover its investment in 10 percent less time than just a few years back.

Additive Manufacturing, through its ability to deliver from a relatively fixed, low-cost investment, unique one-off parts, or batches of parts without the massive outlay in production-line capital equipment which demands scale or production, and hundreds of thousands to millions of parts to recoup that investment. This means that additive manufacturing can add breadth, depth, agility and complexity to the traditional manufacturing process. And this gives manufacturers the breathing room they need to still innovate and still deliver on their required quality assurance – even as timelines and budgets get tighter.

This makes additive manufacturing ideal for prototyping, low rates of initial production (LRIP), custom manufacturing, bridge manufacturing, and spare parts as products move into obsolescence.  

But not all additive manufacturing is the same. Different additive technologies give rise to a different set of advantages and trade-offs. Just using the example of plastics 3D printing to illustrate my point:

• Inkjet-based multi-jet printing (MJP) using UV-cured photopolymer-based resins, remains relatively low cost and versatile, with the ability to selectively deposit material onto a flat build tray at relatively high speed. Final parts have good surface quality and isotropic strength. But such resin parts are typically for prototyping applications only. MJP printers can also utilize their separate print head nozzles to jet a differently-composed support material that can be easily dissolved or washed away without damage to the final part.
• Stereolithography (SLA) printers use similar UV-cured photopolymer materials, but uses a more complex laser-based system in place of a printer head, and a vat to contain the liquid material in place of an empty build tray. SLA delivers excellent levels of accuracy, surface finish and detail resolution  - but at the expense of overall print speed.
• Projector-based imaging printers (sometimes referred to as DLP) work in a similar way to Stereolithography – with a vat of photopolymer resin. But the SLA vector laser process is replaced with a projector-image layer-by-layer process that allows for much faster print speeds. The limitation is typically only the XY part dimensions allowed by the projector.
• Selective Laser Sintering (SLS) offers parts made of true thermoplastics such as Nylons – allowing manufacturers to create tough functional parts in the same final material as the end product. But dealing with plastic powders may require a carefully controlled thermal environment to ensure good yield and repeatability.
• Extrusion/Deposition printing (Sometimes referred to as FDM) also has the benefit of using true thermoplastics and systems are typically robust and lower-cost, with the ability to scale the technology easily to very large part sizes. The trade-off is typically build speed, fine-detail resolution and isotropic strength.

These are just my own interpretations of the pros and cons of course, but the good news is that many of the points I’ve listed above are fast becoming historical generalities. The industry continues to evolve at a rapid pace, and many of these drawbacks are being overcome or eliminated altogether in novel ways.

A few examples:

• UV-cured Photopolymers materials found in MJP, SLA and projector-based imaging, historically relegated to prototyping purposes only, are now more environmentally stable and long-lasting, making them, for the first time, more suitable for tooling and end use final parts.
• The relatively slow print speeds of vector-based Stereolithography are being overcome with the innovative use of synchronous dual lasers and dedicated algorithms to shorten build times.
• High speed cameras and monitoring systems can ensure better thermal management within the SLS printing process,  with new post-processing systems delivering final part surface quality indistinguishable from traditionally manufactured parts.
• We also begin to see the cross-over and hybridization of technologies and systems – where you can find a choice of additive printing methods and even additive and subtractive within the same piece of equipment.

In our next series of blog posts, we will delve into some of these highlighted examples in more detail, hopefully with the intention of making sense of each technology and helping you make the right decision for your additive manufacturing requirements.