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An Introduction to Metal Additive Manufacturing (3D Printing)

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At Velo3D, we’re constantly striving to make metal additive manufacturing (AM) accessible for engineers and manufacturers across all industries. Oftentimes when speaking about AM, experts in the field can get bogged down in specific use cases, which can be difficult to understand for those new to the field, or those who may be learning about industrial metal AM for the first time.

In this introductory guide, we’ll look at metal AM from a high level, specifically laser powder-bed fusion printing, and we’ll explore how designs are created and translated for manufacturing, different iterations and applications of the AM process, and other post-processes involved to create a final, usable, production-ready part just like you would any other manufacturing process.

What is Metal AM and What is it Used For?

For the purposes of this article, we will use additive manufacturing and 3D printing to refer to the same general process. 3D printing tends to be a term used more broadly, however, and can encapsulate at-home 3D printers used by hobbyists, whereas additive manufacturing tends to be used more to describe industrial, technological, or professional applications.

The core technologies that undergird AM go back to the early and mid-1980s when the first patents were issued. For decades, 3D printing was primarily used for prototyping purposes. Rapid prototyping (RP) through 3D printing could bring a design concept to life much quicker than other precision machining processes meeting the form and fit of the design, if not always the function.

As the technology grew more sophisticated, it moved beyond the realm of desktop hobbyists, and is now used as a production manufacturing process for multiple innovative industries from energy and defense sectors to aviation, aeronautics, space, mining, and many more. Metal AM can now be used to produce high quality, industrial-grade precision parts, and it’s valued for its ability to boost performance, lower component weight, consolidate many disparate parts into single structures, and speed up time to market. It’s no surprise that some of the most forward-thinking companies, such as Chromalloy, LAM Research, and Honeywell, to name a few, are investing heavily in metal AM to drive their innovation.

A Closer Look at the Metal AM Process

The metal additive manufacturing process is really multiple processes that result in a finished part. For reference, Velo3D’s end-to-end AM solution uses Laser Powder-Bed Fusion (LPBF), which we’ll explain in more detail later. For now, let’s explore how the overall process works.

First, a high-powered computer translates the original three-dimensional design into two-dimensional print instructions. Next, a metal printer executes those instructions, lasing the part layer by layer onto individual layers of powdered metal. After the final layer is printed, the three-dimensional build can be removed from the printer, de-powdered and post-processed. Post-processing can include various heat treatments, machining, or surface polishing depending on the designer’s intent and environment in which the design will be used. For the purposes of explaining how the process works, let’s break down each of these stages and see how they work for both conventional and advanced metal AM processes.

It All Begins with Design

There are several considerations that engineers need to make when preparing a design for manufacturing. Many times, the perfect design, with highly optimized simulated performance, is impossible to actually produce. Engineers often need to move away from the most optimized design to bring their concept to reality—and the same sacrifices are made when updating or redesigning an existing, legacy part. Design for Manufacturing (DfM) is the discipline that assesses a part and converts that initial idea into a part that is producible with existing manufacturing technologies. Typically, engineers will have rough parameters for a part before making key decisions that can affect manufacturing.

These considerations include:

  • What is the scale of the operation? Meaning, how many of the finalized parts will need to be machined? This consideration can help determine which part production method makes the most sense.
  • What is the application? If a part is going to be used in a high-pressure environment, or in an industry with high standards and strict regulations, this consideration can help determine what materials need to be used in the manufacturing process.
  • What are budget and time constraints? Similarly, to scale, the required turnaround time for a part—which includes multiple iterations of the part and sourcing skilled labor to produce those iterations—and the budget allotted to create the part can influence the method of production.

The DfM process can be a complicated calculus, but when all of the decisions are made tend to end the same way: engineers are given the greenlight to produce a final design within the bounds of those key considerations. This design, typically done using computer-aided design (CAD) files, is usually a compromise between the initial, idealized design concept and the limitations of the production process and the materials.

In contrast, design for additive manufacturing (DfAM) tends to focus more on the manufacturability of parts specific to the additive process. Within DfAM, there is a greater emphasis on part consolidation and conserving material resources during the printing process. When designing for metal AM, an engineer will examine each specific feature of a part and break these features down into separate challenges based on the orientation of the part and feature. For example, considerations for low angles (overhangs), channels and apertures, and thin walls and high aspect ratios can present challenges when translating DfAM designs to final printed parts.

Because of these myriad challenges, the DfAM process can result in parts that stray significantly from the engineer’s original design intent. By designing a part strictly for conventional additive manufacturing, parts can lose critical functionality and/or performance. Part of the reason Velo3D excels in AM is we’ve unified the design and printing processes into one complete end-to-end solution, integrating both hardware and software, and keeping critical design features intact while preserving the part’s original design intent.

Through the integration of design software and printers in an advanced metal AM system, engineers are able to achieve optimal design geometries with greater complexity without compromise, consolidate necessary parts without sacrificing design intent, and get the assurance they need that the part they designed will translate when printed.

How The Metal AM Printing Process Works

Once the design phase is completed, there are a number of forms the additive manufacturing printing process can take. Each printing process is suited for different applications, some of the most common forms of AM printing are:

  • Stereolithography Apparatus (SLA)
  • Selective Laser Sintering (SLS)
  • Fused Deposition Modeling (FDM)
  • Digital Light Processing (DLP)
  • Laminated Object Manufacturing (LOM)
  • Selective Laser Melting (SLM)
  • Laser Powder Bed Fusion (LPBF)
  • Direct Metal Laser Sintering (DMLS)
  • Electron Beam Melting (EBM)
  • Binder Jetting (BJ)
  • Material Jetting (MJ) Polyjet and Wax Casting Technology
  • Rapid Plasma Deposition (RPD)

At Velo3D, we use a modified version of Laser Powder Bed Fusion (LPBF) that incorporates some proprietary, game-changing twists. But through the lens of LPBF we can explore how metal AM printing works on a practical level.

In LPBF, the metal printer contains a build chamber that is kept fully inert and is often pumped with argon gas to remove traces of oxygen or humidity within the atmosphere of the chamber. Even the slightest presence of oxygen can cause impurities and embrittlement in the final part.

Once the conditions are set within the chamber, layers of metal powder are laid down in what’s called the powder bed. Hyper-specialized lasers are then used to heat the powder bed and melt the metal dust into a liquid in the desired shape of the object. Layer by layer, the powder bed is pulled over the object using a recoater blade; the laser melts the powder into the desired shape, and bonds it to the layer beneath it until there is a finished object.

In many LPBF applications, the printing process also includes supports, or scaffolding integrated into the build. When printing with metal, the laser melts each layer which then cools and solidifies quickly. As the metal continues to cool, it contracts. Layer after layer of melting, solidifying, and contracting build up stress in the metal. If not properly accounted for, this stress can warp the metal or even crack the part. To offset this stress, engineers use supports to hold the parts down to the build plate.

For conventional metal 3D printers that lack the sophisticated printing recipes of a Velo3D Sapphire printer, supports are very common. In what some might call “The Million Dollar Staple Gun Approach”, engineers utilizing expensive industrial printers end up producing as much support material as the actual part. This material tends to be the same expensive and difficult-to-machine superalloys required for high-performing designs. Often more than half of the total printed mass ends up being wasted support material that, in post-processing, will need to be removed.

In contrast, Velo3D has pioneered a SupportFreeTM printing process which enables engineers to achieve complex geometries and low angles without the need for support structures to hold the object in place. Our standardized library of highly sophisticated process recipes enables engineers to print their designs without the reliance on supports, and has helped unlock further innovation for applications, such as microturbines, heat exchangers, turbopumps, and more.

Post-Processing for Metal AM

At the end of the printing process, teams are left with what amounts to essentially a rough draft of the object. The final phases of metal 3D printing are then set in motion. After printing, the part and build plate are buried under un-melted metal powder. An operator will vacuum up as much of the powder as possible for reuse on future parts. After this step, an operator can remove the build plate and metal part (still welded to the plate). Further powder removal steps may be required to completely clean the part.

Depending upon the application and metal used, an operator may need to heat treat the part before removing it from the build plate. Due to the high level of stress that can accumulate during a print, parts that are not properly stress relieved can warp or even crack when cut from the plate. Other heat treatment steps can affect the material properties. Processes like HIP (Hot Isostatic Press) and Solution and Age may be required depending upon the part specifications.

For many metal AM parts, additional machining can be used to remove supports and to achieve target tolerances that are difficult to reach on as-printed parts. Once supports are removed, the part can be milled, drilled, and polished inside and out to achieve the required specifications or improve properties including surface quality, geometrical accuracy and other mechanical properties. Oftentimes, internal surfaces are treated using abrasive flow machining to enhance surface finish and remove impurities leftover from the build and lingering support structures.

Finally, when the part is finished, it needs to be thoroughly evaluated and tested to ensure optimal function and that it meets strict regulatory requirements set for specific industries. Velo3D works to ensure quality by integrating these analysis measures within the printing process itself using advanced metrology and part validation sensors and software.

There is a lot to learn about additive manufacturing. Whether you’re just scratching the surface of 3D printing, or you’re interested in exploring metal AM as a parts manufacturing solution for industrial applications, there is a universe of innovation awaiting you on the journey. Velo3D is a pioneer in the metal AM space, enabling innovators to bring even their most complex designs to life, without compromise.

If you’re interested in learning more about the Velo3D metal AM process, contact one of our expert engineers today.

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