The Origins of the Articulated Arm CMM
The ROMER arm finds its origins back in the early 1970's with the original Vector 1 tube measuring arm, developed at that time by ROMER co-founder Homer Eaton, of the Eaton Leonard corporation.
The ROMER arm finds its origins back in the early 1970's with the original Vector 1 tube measuring arm, developed at that time by ROMER co-founder Homer Eaton, of the Eaton Leonard corporation. All measuring arms produced since owe a debt to the original Vector 1. The Vector 1 tube measuring arm, sprung from the fertile imagination of Eaton, who had always had a fascination with tubes, going back to his high school days when he bent exhaust tubes for hot rods in his garage. The original patent was filed on April 18, 1974, and was eventually granted patent number 3,944,798, earning Homer Eaton the rightful title of the father of the articulated measuring arm.
The original Vector 1 was bench mounted and used a compact refrigerator sized computer to power the primitive software, also developed by Eaton. The device would capture the bend geometry of a bent tube such as an exhaust pipe, using a set of electrical contacts inside its V-shaped head.
It wasn't until later that the arm was re-imaged as a device to capture the geometry of all kinds of other objects—not just tubes—and advanced in computing technology made the devices at first "luggable", and then, with the advent of the laptop computer, truly "portable".
In 1986, Homer Eaton and Romain Granger partnered to found ROMER SARL (which are today the Hexagon Manufacturing Intelligence facilities producing ROMER arms in Oceanside, CA, USA, and Montoire, France). Their objective: to introduce a portable articulated arm into the metrology marketplace. The timing was nearly perfect with the advent of the personal computer, and the 3D measurement needs of the aerospace and automotive industries were rapidly emerging to create demand for such a product. The ROMER system 6 was born.
Homer Eaton, now retired, has been a lifelong inventor and entrepreneur. He has been involved with the research and development of measurement and inspection hardware, electronics, and software for the entirety of his career. With more than two dozen patents to his name, his contributions to the metrology industry will be felt for many years to come.
Bill Fetter interviews Homer Eaton: Eaton takes a walk down memory lane. A technology pioneer in his own right, he shares his discoveries and the progress of the articulating arm over the span of more than three decades:
FETTER: What problem were you trying to solve when you conceived the Vector 1?
EATON: I was trying to measure the geometric path of a bent tube shape, rather than the difficult convention of measuring the component features of lengths and angles.
FETTER: What level of precision where you looking to achieve at the time?
EATON: I was looking to achieve an accuracy of 1/32"...0.8 mm.
FETTER: Did you envision the product as a solution for mainstream metrology applications?
EATON: No, I did not at the time.
FETTER: Were there any huge "A-Ha!" moments in the history of the product that you remember in particular? If so, what were the circumstances surrounding them?
EATON: Yes, there was. The first was simultaneously measuring a point and a vector, and this was the origin of the "Vector 1," the articulating arm for measuring bent tube shapes. The second moment was the Infinite rotation where we digitized raw encoder signals and transmitted digital data through slip rings. And lastly was the GridLok concept of the arm inside a virtually unlimited measuring envelope, allowing leapfrogging without error stackup. The beauty is this was accomplished with virtually no hardware; it's just a mathematical feat involving triangles.
FETTER: At what point did you decide to make the jump from inspection of tubes to other components?
EATON: In 1974, George Goodreau, plant manager at Westinghouse, inspired me to build units for measuring steam turbine blades on the shop floor. We built a number of roll-around arms for this purpose.
FETTER: When did you realize this technology could be a truly portable device?
EATON: In the late eighties, Romain Granger convinced me that we could build an even lighter unit and fold it into a more compact shape by adding one more axis. It was about this same time Toshiba introduced the portable computer.
FETTER: What were the main initial impediments to portability?
EATON: There were three distinct roadblocks:
1. Having a portable computer. The "Vector 1" minicomputer weighed 40 pounds.
2. Being outcasts from the "CMM" world in a world of granite, walls, and arrogance.
3. Needing a rigid support base for the arm.
FETTER: What do you consider to be the most interesting application for the arm that you've seen?
EATON: Measuring a Steinway piano and letting metrology merge into the world of art.
FETTER: Which do you prefer to invent: Hardware or Software?
EATON: Hardware. It is more tangible, challenging, and creative.
FETTER: Your volumes of notebooks of ideas are somewhat legendary at ROMER. How many things in those notebooks do you suppose actually turned into products or product enhancements?
EATON: My notebook ideas turned into hardware, electronics, software...well over 50 products in the long run.
FETTER: Where do you draw your inspiration from?
EATON: Stress...the Mother of innovation!
FETTER: What were the most difficult design challenges throughout the history of the arm products?
EATON: The main challenges were the twisting of the wires at the arm joints, and the elimination of the mechanical coupling between the encoder and the arm axis.
FETTER: Thinking back over the entire history of these products, what feature or product are you the most proud of?
EATON: Definitely arm calibration. Creating the mathematical algorithms and artefact techniques for calibrating the arm was the fundamental basis for our success.