Did you know a typical airliner can have as many as six heat exchangers per engine and up to 20 heat exchangers per aircraft? It’s no wonder then that aviation and aerospace rely heavily on heat exchangers to function.
If a mechanical or electronic system produces heat, that heat must be dissipated to ensure the integrity and ongoing function of the system itself.
But designing and manufacturing heat exchangers using age-old traditional manufacturing technique present many manufacturing challenges. To start, they are meticulous parts with many intricate features that must often be brazed together.
What can aviation and aerospace design engineers do to overcome these challenges?
By deploying the revolutionary metal additive manufacturing process (AM) pioneered by VELO3D, industries that rely on heat exchangers can cut costs, drastically reduce manufacturing time, and create a distributed supply chain—all without sacrificing the design and quality of the parts they need.
In this article I’m going to cover the flaws in current heat exchanger manufacturing and explain the benefits metal AM with VELO3D provide at every stage of the process.
Diagnosing the inefficiencies of traditional manufacturing processes
When we zoom out and look at the current landscape of heat exchanger manufacturing, there are flaws at nearly every step.
Traditional brazing, while “tried and true,” has been used since the ancient Egyptians. As aircraft, spacecraft, and other revolutions in industrial processes have pushed the limits of technology, the underlying parts that are essential to their operations have largely stayed static.
These traditional manufacturing processes are rife with inefficiencies and inaccuracies, which fall into five main categories:
As I said before, the manufacturing of heat exchangers is an especially meticulous process when done by hand.
Heat exchangers rely on multipart assemblies—an array of cooling fins, for example—which increases the surface area available for heat dissipation and/or transfer.
These part totals can be in the hundreds, and each of these parts needs to be individually tooled using dedicated equipment for each material and in dedicated vacuum ovens that must be carefully controlled for moisture and residual contaminants.
The time and cost associated with this process is astronomical. Contracting out skilled workers is a major concern during a time when the American Welding Society predicts a 400,000-welder shortage by 2024.
As a result, a turnaround time on a single design iteration of a heat exchanger can take anywhere from 12 to 18 months.
The cost associated with this highly specialized process can be as much as $100 per weld joint, with potential add-on costs for inspection, rework, vapor degreasing, and additional welding to integrate the unit into a finished good.
Brazing and welding are also environmentally taxing processes, producing several harmful byproducts such as trichlorethylene, hydrofluoric acid, and hexavalent chromium—substances that are outright banned or heavily regulated by environmental agencies.
As more companies express a commitment to environmental, social, and corporate governance (ESG), these potentially hazardous processes are going to need to be reevaluated.
After all these steps, it’s still not a guarantee that the heat exchangers produced will meet the quality standards needed to be integral components of an engine.
Placing manufacturing in the hands of any human, no matter how skilled, leaves the process open to technician-to-technician variance, which makes it inherently unrepeatable and, in some cases, unreliable.
With VELO3D metal AM, however, these barriers to manufacturing are mitigated or removed entirely.
How Metal AM Revolutionizes the Manufacturing Process
Additive manufacturing offers improvement at nearly every point of inefficiency in traditional brazing and welding processes because it largely removes the need for hands-on, specialized labor in assembly.
By pivoting the process to sophisticated, next-generation 3D printers, manufacturing becomes significantly less expensive and lead times are reduced dramatically.
What’s more, with AM, the process becomes repeatable, removing errors and enabling on-demand printing within a vertically integrated supply chain.
Fundamentally, metal AM economizes the manufacturing process by consolidating the hundreds or thousands of parts that need to be brazed and welded together into a single part.
A laser-focused, full-stack approach to metal AM
At VELO3D, the printing process revolves around laser powder bed fusion (LPBF): using simple-yet-sophisticated design software, Flow™, the part is “sliced” into individual layers. The print file is then uploaded onto the Sapphire® printer to produce the part.
When the print button is pressed, the powder is laid in the chamber and melted using lasers, layer-by-layer, until a finished part emerges.
The build is monitored layer-by-layer with the Assure™ software where control charts monitor the process chamber, and abnormalities are identified with 3D topographical maps. It’s one thing to print small test specimens, but it’s another to print complete heat exchangers that can meet performance requirements.
VELO3D deploys a proprietary process that enables new levels of design freedom and performance beyond legacy AM systems. One example of this is enabling engineers to design without restrictions in the aspect ratio (or height) of the thin features.
VELO3D’s non-contact recoater plays a key role in ensuring the thin fins are printed without being disturbed (bent over) by the recoater during the powder deposition process, and our SupportFree™ technology also allows for printing down to 0° (parallel to the build plate) with fewer supports.
Heat exchangers by nature are hollow structures, and internal supports cannot be removed. Therefore, printing with fewer supports isn’t just a matter of less post-processing; it affects whether the design can be printed or not.
Finally, VELO3D’s process control also plays a key factor in heat exchanger yield. Flow™ software has specific processes for heat exchangers that have been designed to ensure that the heat exchangers are leak tight – regardless of position on the build plate.
This allows several heat exchangers to be printed simultaneously in production. Not only can 325-micron (.013”) walls be printed leak free but they can be printed consistently leak free to ensure high yield in production.
Designing at the limit
To harness the full potential of metal AM, it is important for the heat exchanger engineer to consider the AM manufacturing process to balance the multiple system requirements.
For example, metal AM heat exchangers often have higher thermal performance due to the higher surface roughness, which promotes mixing of the fluids, however, this also can create a higher pressure drop of the fluids across the heat exchanger.
To counteract this, fewer fins or walls might be required to achieve the balance of thermal performance and pressure drop. Additionally, the geometric limits vary as a function of print angle. The higher the angle to the build plate, the thinner the geometry can be.
For example, the VELO3D Sapphire® can print vertical (90°) fins at 150-microns (.006”) thick (irrespective of recoater orientation). However, the limit at a 45° print angle is 220-micron (.009”). As the heat exchanger is designed, the engineer will need to keep print orientation in mind to achieve optimal (thinnest) geometries in the areas where it matters most to performance.
Finally, metal AM heat exchangers allow a flexibility around design integration that is unparalleled with the conventional (brick) heat exchangers.
To unlock this potential, design and system engineers must work together closely to find the optimal packaging and integration solution. In the extreme case, heat exchangers can be fully integrated into surrounding parts as a single printed part.
When taken as a whole, the VELO3D printing process slashes the printing time per design iteration to as little as four weeks, with the added ability to print multiple iterations simultaneously.
The heat exchangers produced are optimized in their surface area, volume, and integration with surrounding systems; they’re also 99.9% density right out of the printer, with mechanical properties better than cast, and approaching forged metal.
And, because the printing process takes place within an inert, sealed chamber, no toxic byproducts are released into the air, which helps fulfill ESG mandates.
Heat exchangers on demand
The use of metal AM for heat exchangers removes the overall reliance on disparate vendors and enables companies to vertically integrate their parts manufacturing supply chain.
At VELO3D, our full-stack approach to metal AM enables a complete end-to-end manufacturing process that is controlled from design, to printing, to quality assurance.
First, the print preparation process using our Flow™ software collapses multiple steps from CAD to STL file to build file with hundreds of different laser calibrations into a simple, two-step process; CAD files are translated to a single VELO Print file which is compatible on any VELO3D Sapphire® printer worldwide.
This revolution in part traceability ensures that a heat exchanger designed in California can be printed for a corresponding team on a VELO3D printer in the UK while upholding the same quality standards.
VELO3D validates every part printed as it’s being printed using our Assure™ quality assurance software.
Comprehensive build reports of both the parts and the printers themselves give engineering teams the confidence of knowing that the print was successful, and every aspect of the part upholds rigorous standards.
Because this process is consistent and repeatable, if there are errors in the print, they can be easily corrected in design to solve for any issues.
When taken as a whole, the revolutionary metal AM manufacturing process pioneered by VELO3D is a game changer for countless industries that rely on heat exchangers from aviation and aerospace to energy and space.
For a detailed look at out how VELO3D advanced metal AM helps the aerospace and
defense industries streamline and innovate, download our latest whitepaper: Yes, You CAN Achieve the Parts You Want with Additive Manufacturing
You can also get in touch with a member of our expert engineering team today to learn how VELO3D can transform your heat exchanger manufacturing process.