Father Of The Practical CMM, James Coggin (RIP)


QC Rick

I am a member of cmmguys forum and we happen to be lucky enough to have two members who were involved in CMM technology from nearly its initial beginnings, Joe Watson and Dick Considine. Joe and Dick have been kind enough to share some stories of the earliest times in CMM history.
The following entry (there are many more wonderful stories) outlines a special person in CMM history, James Coggin.

"Father Of The Practical CMM"

About 1965 Sheffield started to build Coordinate Measuring Machines or CMMs. Initially, they were more of a curiosity than anything with which you would really want to have to measure parts. Each part to be measured had to be very carefully and precisely aligned to the machine's axes. Any measurements you took had to be recorded by hand from a digital readout. Even then, one would have to subsequently process the readings to account for the size of the CMM's probe to arrive at meaningful measurements that even resembled those on your part's engineering drawing. And without them, you could not know if the measured part was within its allowed tolerances. CMMs did not sell well at all back then. People found other ways to inspect their parts.

In 1967 it was a Sheffield electrical engineer named James R. Coggin who conceived the idea of combining a CMM with a new type of small computer, then termed a minicomputer. He wrote the specifications for the world's first CMM software product to be used to direct the inspection of a part, replacing all of those painful manual alignments and computations with automated ones in the computer. Sheffield's Engineering department had no computer programmers at the time so Jim sought an outside firm to do the programming work.

Working for a contracting firm, I just happened to arrive at the right place and time and soon found myself helping my supervisor there write that first CMM software package in accordance with Jim's software specifications.

The following year, Jim Coggin wrote another CMM software specification. This time it was for a more advanced use of a CMM. It involved the taking of many measurements dynamically while the CMM was being moved by an operator across the contoured surface of a part, a capability that would soon come to be called manual scanning. That made it another world's first. I was called upon to again write for Sheffield the software described by Jim's specification.

In the world of precision measurement, steel behaves a little like rubber and it is important to apply the least force one can to avoid deflecting the very thing you are measuring. Jim worked out how to combine the data from a "soft" or "compliant" probe with the data from the CMM so as to dramatically reduce the gaging force applied to the part being measured.

Besides the standard CMM products and software, Jim also worked on several special applications including a notable one that involved the inspection of critical nuclear reactor parts that positioned fuel rods. This system used those new soft probe capabilities. I started writing the software for that project at my old job but when given the chance, I changed companies in 1968 and went to work for Sheffield directly and finished writing that software as a Sheffielder, working right alongside Jim.

Things really began to take off for us in the CMM business. By 1970, Jim had masterminded yet another world's first and we delivered a prototype CMM just in time to be presented at an industrial show that fall in Chicago. This time, it was the world's first servoed CMM inspection system. That is, the CMM which had always been pushed around by a trained operator with just the right "touch" now inspected parts totally by itself. The CMM had become a very specialized robot. The machine was exhibited for a week at that show. All day long of every day, attendees stood four deep around that machine just to watch it run flawlessly time after time and ask questions. It was clear that this was to be the future of much of the CMM market.

Within a couple more years, we had the servoed CMM automatically scanning contoured parts, again using soft probes. For each job, Jim decided what needed to be done electrically and in software. He engineered the electrical systems and I wrote the software. We were a good team to be sure.

Later, Jim moved into Technical Writing and later still, other positions at Sheffield. Never again did we work so closely as we did for those few very special years and never since has the CMM business appeared to advance so rapidly as it did in that magical time.

Some who knew James Coggin generally may have considered him to be a rather meek man, seemingly confused sometimes by the details of his own electrical designs. But it was clear to me that underneath, he was not afraid to try new things and to take well thought out risks. Those traits paid off very well for both him and for Sheffield.

In my opinion, in many respects James R. Coggin should be recognized as the father of the practical CMM system. Granted that if he had not conceived of adding a minicomputer to a CMM or the other things, those things would eventually have been done by someone else. But the fact remains that he did conceive of those things and he did bring them into existence first. Today, his general designs still underly the CMM business the world over.

Jim's curiosity and skill laid the foundation for the line of work that kept me gainfully employed and happy for more than 32 years of my life. I owe him a lot.

I am most saddened to have to report that April 13, 2010, the world of the CMM lost an important founding father when James R. Coggin passed away at the age of 79.

This photograph circa 1972 shows Jim Coggin with one of his special CMM systems that measured contoured parts with a soft probe on a servoed CMM.
Author: Joe Watson

(Photos not attached)


Talking about Minicomputers, I'd love to get my hands on a working PDP-11, but I realize this is probably a pipe dream. :topic:

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