Direct metal printing helps manufacture lean and green heat exchanger

Direct metal printing by 3D Systems, On Demand Manufacturing helped the University
of Maryland’s Center for Environmental Energy Engineering (CEEE) develop a more
efficient heat exchanger while meeting their ‘lean and green’ manufacturing

The CEEE is working with Oak
Ridge National Laboratory to develop the next generation of miniaturised
air-to-refrigerant heat exchangers for HVAC and refrigeration applications. For
this project, funded by the US Department of Energy’s Building Technologies Office, only one type of
manufacturing could satisfy CEEE’s lean and green mandate: direct metal
printing (DMP) using 3D Systems’ On Demand Manufacturing service.

Greater efficiency in less time

CEEE provides innovative solutions and technology transfer to meet
industrial research and development challenges. 3D Systems On Demand
Manufacturing is the world’s leading provider of unique, custom-designed parts,
offering instant online quotes, expertise in 3D design and printing, and proven
manufacturing services support.

CEEE partnered with 3D Systems to increase the efficiency of a 1kW
heat exchanger by 20 percent while reducing weight and size. Thanks to the DMP
approach, the manufacturing cycle for the heat exchanger was reduced from
months to weeks.

Making it manufacturable

Heat exchangers are used widely across the world in any application
where heat, cool air or refrigeration is required. At a global level, heat
exchange is a multi-billion-dollar industry touching everything from consumer
goods to automotive and aerospace engineering.

CEEE’s extensive experimental and theoretical research has led to
automated design algorithms for creating unique shapes for tubes and fins used
in heat exchangers. In addition to achieving an optimal air-side thermal
resistance, key objectives also included minimising the size and weight of the
heat exchangers. However, these innovative designs require new ways of

Vikrant Aute, director of CEEE’s Modeling and Optimization Consortium,
explains that most of these optimised designs are simply not economically
manufacturable today as they are too complex technically with small feature
sizes and extremely thin material thicknesses.

This is where the unique capabilities of direct metal printing come into
play – by removing the complexity.

Direct metal printing, in this case 3D Systems’ ProX DMP 320 system enabled CEEE to prototype
its heat exchanger with non-conventional, variable shapes that weren’t possible
to manufacture using traditional forming techniques such as extrusion or
stamping. According to Aute, DMP allowed them to manufacture highly
unusual tube shapes in the form of a hollow droplet to carry the refrigerant.

3D Systems On Demand Manufacturing provided input into the design
of the heat exchanger to ensure that it could be manufactured efficiently.

Jonathan Cornelus, business development manager at 3D Systems On Demand
Manufacturing says the ProX DMP 320 allows them to deliver open-channel
diameters and feature sizes as small as 250 microns in a reliable and
repetitive way. He adds that high pressure and leak-tight exchanger walls can
be built as thin as 200 micrometres, which is a true game-changer for heat exchanger

Better design in one part

Working together, CEEE and 3D Systems optimised the heat exchanger
design so it could be printed as a single part that requires minimal secondary finishing
operations. Manufacturing can be completed in weeks instead of months, enabling
CEEE to test designs much earlier and more often during the research program.
The one-part design also helps ensure greater reliability.

Observing that assembly by brazing extremely thin tubes to a manifold using
conventional manufacturing technologies can be painstaking with very low
reliability when it came to leakages under high pressure conditions, Aute says DMP
technology eliminates any need for assembly since the part is produced in one
continuous operation, no matter how complex the parts or how delicate the

The ProX DMP 320 not only handles very complex parts at no extra cost, but
also meets CEEE’s lean and green goals.

Pre-set build parameters developed by 3D Systems based on the outcome of
nearly half-a-million builds, provide predictable and repeatable print quality
for almost any geometry.

A totally new architecture simplifies set-up and delivers the
versatility to produce all types of part geometries in titanium, stainless
steel or nickel super alloy. Titanium was chosen for the CEEE heat exchanger
project, based on its lack of porosity and the ability to provide extremely
thin, but very strong walls.

Exchangeable manufacturing modules for the ProX DMP 320 system reduce
downtime when moving among different part materials while a controlled vacuum
build chamber ensures that every part is printed with proven material
properties, density and chemical purity. The small portion of non-printed
material can be completely recycled, saving money and providing environmental

CEEE performed extensive testing on the new heat exchanger design, using
infrared cameras to verify that heat was dispersed uniformly over the exchanger
and that all the narrow, droplet-shaped exchanger channels were open and
functioning fully. Results showed that the DMP-manufactured heat exchanger
performed as expected.

Adding mean to lean and green

The unique capabilities of direct metal 3D printers such as the ProX
line are rapidly turning the DMP technique from an experimental prototyping
tool into a mainstream production asset for manufacturers worldwide.

3D Systems’ Cornelus says DMP is being used in new applications as well
as massive improvements for existing projects in upper-end aerospace and
industrial equipment markets, especially in cases where reduced space, low
weight and high efficiency are critical concerns.

He adds that CEEE’s heat exchanger application exemplifies the
importance of DMP in the lean manufacturing space for creating low-volume,
high-complexity metal components. These parts are now performing critical
functions under challenging conditions such as continuous stress, high
pressure, repeated use and extreme temperatures.

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