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Making Molybdenum Ion Propeller Module with 3D Printer

July 10, 2019

Researchers in Beijing are exploring better ways to identify ionic optics and make molybdenum parts by 3D printing. Their research results were recently published in "3D printing of molybdenum in ion thruster grids and holding electrodes".

The main components of ion thruster are ion optics and maintainer. Optics plays a major role in the geometric structure of the engine. However, their erosion limits the life of ion thrusters. The function of the holder is to protect the hollow cathode from ion bombardment and open the cathode discharge. Metals and carbon materials are usually used to make the necessary electrodes. Molybdenum is a commonly used metal material for the manufacture of ion optics and maintainers.


In the manufacturing room of SLM machine, the manufacturing piston (left) is connected with the manufacturing plate, and the powder conveying piston (right) is distributed on it with metal powder. The printing process begins when all the required powder is loaded onto the powder conveying piston and its surface is flat and aligned with the manufacturing plate on the piston.

Graphite is the traditional choice for materials with carbon-based materials (thermal expansion coefficient) CTE close to zero and sputtering rate lower than molybdenum, because of its affordability and high industrial understanding of its manufacturing methods, although researchers say that pyrolytic graphite and carbon composites are also used for ion optics mounted on important thrusters. On devices.

In order to simplify the manufacture of ion optics, Beijing University of Technology has carried out a research, whose core is the 3D printing of molybdenum for electronic propeller parts. Several healthy electrodes have been produced. Researchers chose selective laser melting (SLM) for the project, mainly because of its ability in metal printing, but also because of the accuracy level provided, especially in aerospace applications.


At the end of the SLM manufacturing process, four sets of screen and accelerator grids and several cube samples are available. After manufacture, the parts are surrounded by sintered powders which are removed and used in the next process.

A Bit research project has created several 3-D printed ion optics devices to further examine the concept of extra-manufactured ion optics. Another study measured energy density, involving:

laser power
Laser scanning speed
Patterns Filling Spacing
Layer thickness

Molybdenum was printed by SLM, and as the research progressed, they decided to use ionic optical materials to install the ion source in the laboratory for testing.

"Several sets of screen and accelerator grids are printed on different manufacturing processes, and the output is studied to verify that SLM devices can generate optical devices of required thickness and locate aperture arrays correctly. The researchers examined these grids and found that they met the design requirements.


The deviation of the scanning system is opposite to that of the scanner. Because of the excessive energy provided by the laser, the grid distributed in the lower part of the plate presents a combustion region.

Despite the fact that the researchers say "no challenges have emerged so far", 3D printing of the custodian is still in the development stage. Researchers say that since neither optical elements nor storage devices are "specially needed components", SLM molybdenum is not required to provide e with the same mechanical properties as solid metals.

"The results show that when the energy density applied in the preparation process approaches the maximum energy density, the mechanical and thermal properties of SLM molybdenum are similar to those of solid metals, thus producing refractories with a value of about 300 jmm-3. This fact is related to the porosity of the output, which decreases with the increase of energy density, "the researchers concluded. Sputtering ablation behavior of selective laser melting materials has not yet been evaluated, but it must be studied before additional components can meet the real application of electric propulsion.

With the development of new materials and processes, new engine alloys and even robotic technology by organizations like NASA, 3D printing is becoming more and more popular in aerospace applications.

Source from: https://creality3dpro.store/