How Additive Manufacturing Complements Conventional Plastics Production
Isaac Maw posted on August 06, 2019 |

Injection molding, as a process for mass-producing plastic parts, has been refined over multiple decades and is a massively efficient way to produce high volumes of identical plastic parts. In the age of mass-produced goods, this was ideal.

Today, with the advent of digital manufacturing, the demand is rising for customized products tailored to the individual. It’s not enough to offer a customized product. Manufacturing processes must now also be flexible enough to accommodate custom work at mass production speed.

In response to this demand for “mass customization,” production of high-value and low-volume parts has started to shift to industrialized 3D printing, known as additive manufacturing (AM). However, most high-volume parts continue to be made with traditional injection molding (IM) techniques because the cost of engineering and moldmaking is amortized across many parts. So, these two options accommodate both low-volume custom orders and high-volume, mass-production orders. But what about manufacturers that need to produce custom parts at scale—is this a new growth area?

According to EOS, the solution lies in the industrial additive manufacturing ecosystem. This includes not just the additive machines, but also the design, materials, process and software which can be optimized to support flexible production of custom parts at a global scale. Solution engineering is fundamental for deploying AM effectively in serial production. This means rethinking and reengineering the material, process and system of the product design in order to take full advantage of the capabilities of AM.

In this way, AM  and traditional molding complement each other, serving each type and scale of need for plastic production.

Taking Advantage of AM Capabilities

With industrial polymer 3D printers, powder-based technology, such as selective laser sintering (SLS), is most suitable. Parts can be arrayed in the build chamber in three dimensions, supported by the unfused powder, allowing the relatively long cycle time (10+ hours in many cases) to be offset by the high productivity per print cycle.

“Today’s SLS processes are competitive with precision injection molding on parameters such as repeatability and cost, at least at low-medium volumes,” explained Fabian Krauss, global business development manager for polymers at EOS. “Without tooling time or tooling cost, AM is much more cost effective than injection molding.”

This graph from Jabil shows how the cost of injection molding, including mold cost, compares with AM. Jabil actively uses EOS, HP and Ultimaker printers in their production operations for consumer goods, automotive parts, jigs and fixtures, and medical device manufacturing.

In this graph, the gray curve represents the cost per part of injection molding and additive. While IM requires high volumes in order to amortize the cost of molds, additive parts cost the same per part no matter the volume. The blue line represents a hypothetical future cost reduction in the AM process.
In this graph, the gray curve represents the cost per part of injection molding and additive. While IM requires high volumes in order to amortize the cost of molds, additive parts cost the same per part no matter the volume. The blue line represents a hypothetical future cost reduction in the AM process.

This basic cost comparison does not capture the full story, however. Comparing AM and IM directly ignores the opportunities to redesign, customize and optimize products at the product lifecycle level.

Solution Engineering: Going Beyond Deposition Differences

The ‘tip of the iceberg’ is a tired analogy, but in this case it’s fitting. The fact that AM allows for production of plastic parts without a mold is the 5 percent of the iceberg above the waterline. The other 95 percent is below the surface. This is where solution engineering comes in.

When designing a 3D printing solution for a polymer part, engineers have the opportunity to step back and reexamine the part from a system level, considering the entire lifecycle of the part. In additive manufacturing, your part’s digital twin is not just a static model of what will be manufactured—it’s a dynamic part of the manufacturing process.

(Image courtesy of Aetrex Technologies via EOS.)
(Image courtesy of Aetrex Technologies via EOS.)

3D printed custom orthotics from Aetrex technology is another ideal use case that illustrates the concept of solution engineering. Without 3D printing, most orthotic insoles use layers of foam and plastic to provide the desired properties. Instead, Aetrex uses generative design and optimization technology to design “digital foam,” which uses a variety of lattice structures to create different elasticity and compression properties across the insole. This allows digital scan data of any foot to be translated to an insole using one material and printed in one part. This process was incubated at EOS’ technical center near Austin, Texas.

Here are a few examples of disruptive opportunities for additive manufacturing in plastic production:

  • A part made of an expensive material could be optimized using generative design, creating a lattice-structured part which uses less material and has less weight
  • A metal part could be replaced by a polymer part with the same characteristics
  • A one-size-fits-all product could be replaced with personalized, custom products which provide greater value to a wider set of customers
  • An assembly of several parts could be printed as one piece
  • A product supported by an inventory of spare parts could use a digital inventory and print spare parts on demand at local facilities
  • An assembly jig could be designed, printed and in use on the line the same day

Mass Customization: The Disruptive Potential of Polymer AM in Production

Mass customization is a fascinating application for AM. Today’s consumer is already familiar with customization in products such as custom insoles, hearing aids or mouthguards. In these applications, AM simply reduces the high cost of custom manufacturing. For example, Aetrex technology uses foot scan data to generate an accurate custom orthotic using different structures, called ‘digital foam,’ in one layer. This allows the company to produce a customized product on demand and locally, with no inventory cost.

However, when it comes to purely cosmetic customization, the concept may at first seem foreign. As consumers in today’s mass-production world, we understand the concept of economies of scale and may see customization as an unnecessary, extravagant feature. Some may ask, “why would I need my car customized?” It’s difficult to break free of this way of thinking, but with digital manufacturing enabled by additive processes, it’s feasible for a run of unique parts to cost the same as a run of identical parts. So, the question is not “why customize?” but rather “why not customize?”

(Image courtesy of BMW Group.)
(Image courtesy of BMW Group.)

The British carmaker Mini is owned by BMW, a company which has embraced AM in production. Mini Yours Customized allows customers to design and order customized parts, such as rocker panels and trim, online. Parts are produced on-demand and shipped directly to the customer.

What’s the Future of Polymer AM in Production?

Given the disruptive capabilities of plastic 3D printing across the manufacturing sector, the question is: will AM replace injection molding? “No,” said Krauss.  “AM technology opens up new avenues for design and manufacturing of plastic parts, but this doesn’t necessarily mean AM needs to outperform IM on mass production. It simply gives manufacturers alternatives when working in areas where IM isn’t optimal.”

As AM gains adoption in various manufacturing industries, it’s unlikely to directly replace injection molded parts in production. Rather, established paradigms of mass production will begin to share market space with new approaches, which are enabled by the capabilities of AM. This is exciting not only for product designers and manufacturers, but also for consumers.

According to EOS, next steps for getting started with AM begin with identifying an application. This could be prototyping, low-volume production, or jigs and fixtures, for example. Next, develop your application solution, considering not just the process but also the design and lifecycle of the part. From there, certification and ramp-up pave the way to establishing full-scale digital manufacturing facilities.

For more information about EOS plastics manufacturing technology and solutions engineering, visit EOS.

EOS has sponsored this article.  All opinions are mine.  --Isaac Maw

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