From supply chain control to revolutionizing the way core parts are designed, metal AM is a disruptive force across countless industries.
In this article we’ll look at the unique challenges engineers face when producing one application in particular, turbopumps, and how Velo3D’s advanced metal AM solution is redefining that process in design, manufacturing, and qualification.
What are turbopumps?
Turbopumps are essential components in everything from rocket engines to race cars. These core parts work by converting mechanical energy into pressure. The main working element of a turbopump is the impeller, which can either be open or closed (shrouded).
Impellers are comprised of numerous blades attached to an internal hub that need to withstand high RPM, intense pressure, and sometimes corrosive environmental conditions.
Another key component is the volute section which channels the fluid and further controls the pressure rise.
What makes turbopumps so difficult to produce?
Turbopumps and the impellers and volutes that comprise them are a unique challenge for engineers in both design and production.
The main challenge in design is to achieve a balance between moving the fluid with a high velocity and avoiding the harmful effects of cavitation. This balance requires precise blade and channel geometries. Furthermore, the parts need to withstand high RPM stresses, rotating at 10s of thousands of RPM.
Traditional manufacturing (CNC machines) techniques struggle when producing shrouded impellers because the internal channels are often difficult to access with a drill bit.
Shrouded impellers have long relied on five-axis machining in manufacturing, for example, with both the bottom impeller and shroud created as separate pieces, which are then brazed or welded together using EBM.
Parts without direct line of sight to the machining surface require different machining techniques or may even be impossible to manufacture.
This process tends to be costly and low yield, and the resulting production lifecycle can take months and require multiple manufacturing phases before a final part is ready for operational spin testing.
This limits the design window for engineers trying to fully optimize these parts.
Volute sections create additional challenges. With an almost organic sloping reduction in diameter throughout the spiral channel, circular volutes tend to be cast. This creates significant lead time issues if an engineer can find a supplier. For small quantity orders, this can be difficult.
The complexity and manufacturing delays of turbopumps makes them a prime candidate for AM. However, conventional AM systems struggle for many of the same reasons as traditional solutions.
Conventional printers struggle with the low angles caused by blade design and the shroud of the impeller. To overcome these low angles, many AM engineers will try to add supports or orient (tilt) the part while it is printing.
With supports, a post processing machinist will need to remove the supports and recondition the supported surface. This is often difficult or impossible for the same reasons that traditional manufacturing cannot make the part—no clear line of sight access to the surface.
Tilting the part creates even more challenges. Printing is a process of melting and solidifying metal, layer after layer, for thousands of layers. This process of heating and cooling the metal creates stress.
Printing asymmetrically at a tilt causes the part to print out of round or ‘warped.’ Tilting the part results in prints that cannot be balanced and will fail a spin test. For parts that eventually rotate at very high RPM, this proves problematic.
How advanced metal AM transforms turbopump design and production
The Velo3D advanced end-to-end metal AM solution is uniquely suited to the challenges of turbopump design and manufacturing.
Sapphire® printers can execute on ambitious impeller designs without compromising design intent.
The Velo3D solution uses an advanced SupportFree™ process, which means it’s can achieve low angles and overhangs well below 45 degrees without the need for exhaustive support structures.
This is especially valuable in components like shrouded impellers, where these support structures can be nearly impossible to remove. And if removed, risk damaging the surfaces of the critical flow channels. This can reduce the performance of the part and harm part lifetime.
Not only does the Sapphire® metal 3D printer eliminate the need for supports, but it also eliminates the need for tilting the part. This means that the parts print true to the design intent without warping.
Engineers are able to balance and spin test these impellers, avoid damage to the surface finish, and reduce post processing cost and risk. The result is a balanced part with reduced pressure drop and consistent, efficient flow pathways.
As a complete end-to-end solution, Velo3D also features process monitoring software which is critical to part validation in industries such as aerospace and energy with high levels of oversight.
Assure™ software monitors the build and the printer through every layer of the process, continually ensuring that the build is successful. When the build is finished, engineering teams are left with extensive reports to the integrity of the part which can serve as the foundation for qualification.
By integrating the design, production, and qualification process onto one system, Velo3D creates a reliable, repeatable system.
When a part is successfully designed and produced to the required standard, those build parameters and instructions can be applied on-demand. We call the resulting design file a “Golden Print file”, meaning that part can be printed on any Velo3D printer anywhere in the world using the same material.
The supply chain agility that stems from this repeatability means drastically reduced lead times for replacement parts.
Are you interested in learning more about Velo3D’s advanced metal AM solution? Get in touch with one of our experts today to see how we’re revolutionizing manufacturing.