Engineers Ask: Where Do I Source Complex Metal Parts in 2022?


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It’s 2022, yet some seemingly basic questions remain unanswered at our doorstep. For engineers, one of those concerns is sourcing custom, intricately-featured metal parts. With an ever-widening array of new manufacturing technologies and services at their disposal, engineers have more capabilities to choose from than ever before, but, ironically, this has only added to their difficulty of decision-making.

Demanding part requirements may seem like they would inherently narrow the selection pool of viable options to obtain a part, but all too often it seems the opposite is true.

Part Sourcing and Where to Start

Before committing to a procurement strategy, it helps to understand the entire landscape of options. At a high level, that means two primary choices: insource or outsource. Naturally, it’s not so simple as that, as even then there are plenty of branches:

  • Internal 3D printing prototyping resources
  • Internal machine shops
  • External machine shops
  • Broad service providers
  • Focused vertical suppliers

Each of those categories, in turn, has its own subdivisions of choice:

  • Implementation speed
  • Speed of iteration/lead times at steady state
  • Capacity for simultaneous projects
  • Impact on personnel (operating time/effort/extra people to operate)
  • Facilities required
  • Scaling (where do I go for prototyping, then production?)
  • ROI (service provider is immediate, in-house equipment requires on-going use to justify)

While neither of those lists is exhaustive by any stretch, at a quick glance that’s five primary sourcing options each with seven impact areas – 35 discrete considerations to map out just to shake out an overview of available options. And that’s the at-a-glance; many of these areas, like scaling, are flow charts in and of themselves with arrows branching forward and back from prototyping to bridge production to mass production, as appropriate.

Let’s examine the overarching options for sourcing and how understanding each might inform a decision map for sourcing complex metal parts. We’ll narrow it down to simple pros and cons for each, rather than a deep dive into seven categories for each of five options.

Internal 3D Printing Resources for Prototyping

The premise: prototyping designs on internal 3D printers that will later be outsourced for production.


The good news about in-house 3D printing is speed. Once internal expertise and resources have been built up, getting a project in process is a matter of assignment, design, and action. That’s the promise, of course, of localized manufacturing: convenience and agility.


All the upfront investment, all the training, is on you, and that represents extensive time and cost. Metal 3D printing is expensive. Even if the prototyping is all polymer, ready to scale up through a third-party supplier to final metal form, all inherent design considerations come back to metal and that final production process. This can add a layer of complexity in development to already complicated designs.

Internal Machine Shops

The premise: prototyping and scaling into production through an internal machine shop.


Extending beyond rapid prototyping, in-house machine shops comprise more scalable setups with potentially more extensive manufacturing technology for which more engineers are familiar designing. These internal installations keep everything in-house, enabling localized production and natural IP protection in terms of limited eyes on a project.


Limitations are inherent in terms of having access only to the equipment and materials on hand, as well as the accompanying expertise and capacity. Few internal shops are prepared to rapidly handle unique, complex parts or large spikes in demand, and most have established backlog queues where a part will wait. Experienced machinists demonstrate impressive creativity in finding workarounds for some of these challenges, but an internal shop may not always be the possible solution for sourcing complex parts quickly, nor for scaling production internally.

External Machine Shops

The premise: prototyping and scaling into production through a third-party machine shop.


Sending a job out for an external machine shop removes barriers of internal equipment investment, and all that accompanies, opening up new possibilities for equipment and expertise. The ROI is immediate as soon as parts are delivered, ensuring an understood transactional relationship. Scale-up and supplier diversification, too, can be easier as once a design is perfected it can be as easy as adjusting the quantity number on an order to ramp up, and new vendors can be vetted in parallel.


Adding logistical steps necessarily increases the time to having the part in hand, especially if multiple iterations are required. Shopping around for the right machine shop requires some investigative work as well, to ensure that the selected shop is able to thoroughly understand project requirements, and provide the right level of quality on complex parts.

Diversified Third-Party Service Providers & Marketplaces

The premise: prototyping and scaling into production through an external service bureau that offers a range of different manufacturing technologies.


Service bureaus like Protolabs, Xometry, FATHOM, Fast Radius, and others offer increasingly expansive technology platforms and materials options. They’re a cost-effective option to quickly test out a variety of different manufacturing processes, without the large upfront capital investment of bringing one in-house. These companies can 3D print for rapid prototyping before moving into a final production technology of choice to suit scale.


Different teams at the service provider work on different technologies, increasing touch points (and design/IP handling), potentially introducing lapses in communication or failure points. Bureaus generally operate commercially available equipment purchased from OEMs, so the advantage of using one is more economic than getting access to otherwise-unavailable technical capabilities. Limits remain in place in terms of a bureau’s installed technology base, as each provider offers a different range of capabilities, and each must be vetted prior to starting a new project to ensure the provider has relevant experience to meet the appropriate part requirements for a project.

Focused Vertical Suppliers

The premise: prototyping and scaling into production through a vertically-integrated supplier focused on a single manufacturing technology.


A focused vertical supplier develops and operates their own technology, and enables instant access to chosen manufacturing technology and design expertise. This targeted technology strategy builds deep cradle-to-grave know-how for maximizing the potential of a single suite. Fewer touch points mean fewer opportunities for failure, as well as fewer vendors to set up. Since the focused vertical supplier has developed their own technology in-house, they can potentially modify or refine their processes to accommodate parts that were initially outside the capabilities of their tech, a key advantage of these suppliers over third-party service bureaus who are only running standard, commercially available systems.


The limitation is inherent in this strategy: one process suite will be used end-to-end. If it’s not the right fit, you’ll need to look elsewhere to procure the parts you need.

The Decision is Yours

Ultimately, the decision of supplying complex parts comes down to what you need, when you need it, and the relationship you need to form – and can support.

About the Author

Arian Aghababaie, PhD, is the Co-Founder, President, and Chief Strategy Officer at Holo, where he leads product, marketing, and strategy. With over a decade in the additive manufacturing industry, he has an extensive background in leading teams bringing new 3D printing technologies to market. At Holo, he sets the vision for applying the company’s metal additive manufacturing technology to production applications, helping drive product development acceleration for R&D and production teams of customers across a wide variety of manufacturing industries. Prior to Holo, Arian built and led the team at Autodesk that successfully developed and launched the Ember 3D printer – the first open-source stereolithography platform. He previously co-founded The Invention Works, which developed low-cost, high-resolution stereolithography technology and was acquired by Autodesk. Arian received his undergraduate degree in aerospace engineering and his PhD in rocket nozzle fluid dynamics from the University of Bristol. He lives in San Francisco and enjoys cooking, boxing, and playing the piano.

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