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Physicists Use Milling Machine with CNC Solution to Produce Precision One-Off Parts Capable of Seeing Into Space

Astronomers and physicists become milling machine operators at the University of Hawaii Institute For Astronomy as they manufacture parts used for instruments in state of the art telescopes.

When you enter the laboratories at the University of Hawaii's Maikalani Institute For Astronomy (IFA) Advanced Technology Research Center on the island of Maui and hear talk of light years, dark energy and space telescopes, it quickly becomes apparent that this is not your typical machine shop. The machining for instrumentation developed here involves some of the most sophisticated techniques on Earth, which is a pun of cosmic irony, as the workpieces produced here are primarily used to help evaluate happenings in deep space.

The state of Hawaii and the island of Maui in particular have some of the best conditions on Earth for nighttime telescopic observation, as well as the best in the world for daytime solar viewing.



The Maikalani facility provides laboratory workspace for Physicists and Astronomers performing advanced metrology and optical fabrication, novel optics design, optical/infrared sensor development and a creative workspace. Maikalani literally means "knowledge we gain from the cosmos".

As the Lab Director, a world-class physicist, Dr. Joe Ritter explains, "At the IFA, our excellent staff and faculty invent, design and build novel instruments for use in state of the art telescopes. Among other technologies, we are working to develop a novel generalized conformal diffraction grating. Gratings are optical components used to split light into component colors for the study of the chemistry of stars." Ritter and his assistant John Valliant are also the machinists. They exchange their hats from physicists to milling machine operators, using a Spinner MC650-5A, equipped with Sinumerik 840D solution line CNC, to produce parts from high-conductivity copper and aluminum 6061-T6 grades, among other alloys.

The researchers chose the Spinner MC650-5A for its accuracy and predictable degrees of variation.



Since the Spinner is used at the IFA exclusively for precise one-off parts, the search for the right machine focused on equipment that had among the industry-highest standards of accuracy and precision. The novel conformal gratings under development at the lab are designed with variable pitch and spacing dimensions to correct optical aberrations and also focus and split infrared light for future deep space spectroscopy instrumentation.

As Ritter explains, "Accuracy is everything in optics. Most of the machining centers I evaluated were in the +/-25 micron (~0.001") range for accuracy. We settled on a 3+2 axis machine with 100 nanometer precision scales with interferometric remapping on the 840D sl CNC. Because we do experimental fabrication work and optics typically need to be made to micron level tolerances, it was imperative to have a feedback control on the machine tool with a known accuracy and predictable degrees of variation." As an example, though not suitable for visible light, the optics Ritter discussed required accuracies of a few microns-good enough for infrared optics. Other technologies being developed by Ritter at IFA include novel photonic meta-materials for future space telescopes intended for studying exoplanets and the evolution of our universe.

Sample parts produced on Spinner machine, mostly copper and aluminum, include many that become diffraction gratings used on highly sensitive instruments for deep space exploration projects.



Dr. Ritter cited the age-old challenge for educational and research institutions, when searching for such precision machinery, namely, budget constraints. In this case, the lab was fortunate, according to Ritter, as they became aware of a demo machine from Spinner, available from Lois Hill and Robert "Mac" McPherson of MacHill Machinery in South Carolina. During the purchase and commissioning, Ritter emphatically noted, "The Spinner technician Herr Siegfried Jungk, who trained us, was exceptionally talented and particularly knowledgeable and helpful. Ritter also noted that the Siemens ShopMill software included with the CNC package, was "an easy-to-use program for getting the multi-axis machining up and running for basic drilling and facing."

While invariably the smart guys in any room, Dr. Joe and John Valliant are not machinists by trade, so they were using both Shopmill and CAD/CAM programs like Mastercam with the highly-specialized G-code generator and post-processor needed to create precision path cuts, then running them directly on the mill to quickly begin cutting, an absolute necessity in their one-off world of custom parts.

Dr. Joe Ritter and John Valliant, who run the Spinner machine at the lab.



"For some optics, the millions of coordinates we use for every workpiece are pushing the control to the limit, but it responds well. Plus, the teach-in functionality of the Sinumerik 840D sl CNC and its software package keep us running very efficiently," according to Valliant, who worked in the lab as a University of Hawaii-Maui college student and has learned CNC machining on the go. In an environment where 0.1 of a wavelength of light is the desired target for accuracy, this is no small achievement. Valliant adds, "Once you're comfortable with this machine and the control, the process is very intuitive."

Dr. Ritter, who is constantly pushing the boundaries on novel orbital space telescope designs, notes that the state of Hawaii and the island of Maui in particular have some of the best conditions on Earth for nighttime telescopic observation, as well as the best in the world for daytime solar viewing. The National Science Foundation will soon build the world's largest solar telescope on Maui. Maui is a little known hotbed of technology development. In addition to solar research and deep space observations, the Institute for Astronomy partners with many nations to push the boundaries of human knowledge, while training future scientists.

University of Hawaii Institute For Astronomy telescopes are able to see the solar system and into deep space with greater clarity than at any other location on the planet, according to Dr. Ritter.



Currently, the Institute is engaged in developing technology to make other new scientific discoveries possible. They include the largest camera on earth, new high contrast off axis telescopes, instruments using electronic cameras and spectrographs for the telescopes on Mauna Kea, Haleakala and, in Chile, detectors such as ultra-sensitive mega-pixel infra-red CCD arrays, plus adaptive optics to help overcome the image blurring caused by Earth's atmosphere.

Mac McPherson, the Spinner machine dealer and importer for North America, adds, "We do considerable business with academics and it's always challenging, owing to the unique nature of their machining needs. In this case, an optic grid pattern with high accuracy was the biggest hurdle. We were able to supply the Spinner demo machine within budget and with the proper tooling included. The lab actually built their own custom fixturing for their work and Siemens helped to develop a special post-processor program."

"Na Kilo Hoku" means "the watchers of the stars" and the instrument components made here certainly help them do just that -- and also gain knowledge from the cosmos for us all.

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