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The history of fluted roll manufacturing

When Charles Langston was asked to build a single facer for David Weber over 100 years ago, the task of forming the fluted rollers must have been daunting. How to make a 40" wide "gear" with "teeth" about 10% in size of a normal gear tooth, and all the while having a geometry and smoothness that would not cut or mar the straw paper used for medium. Previous "Fluters" were hand cranked, were only about 10" wide, and had rollers made of brass. Charles took the flute form from these early linen fluters, and determined how to apply it to his process. A process which was called DRAW CUTTING. (In the Mills Machinery fluter collection there is an 1885 "Star" linen fluter that has a flute form identical to todayís "B" Flute)

DRAW CUTTING involved mounting a roller on a moving table, and actually shaving each and every flute into the machining surface. The flute form was filed into the "cutter", itsí tip was placed against the roll and the flute was "scraped" into the surface, removing very little material with each pass. A "B" Flute roll of Charles Langston original design would have had 78 flutes, and "draw cutting" as this process was called was extremely slow. Draw cutters are still used to this day, but on specialty corrugating rolls that are small in diameter and short on length.

MILLING was the second-generation process. As normal machine tools evolved, the thought of vertical milling began to take shape. Commercial milling machines were modified to have longer beds, and Brown and Sharpe was contracted to manufacture milling cutters which had the flute form. These cutters started as single line forms, and were a good productivity increase over draw cut rolls. The finish was not quite as smooth, but the timesavings warranted its use. In the 1950ís and 1960ís Cincinnati Milacron was convinced to built compound milling machines that had two milling heads and a base that would hold a pair of rollers at the same time. Later, flute form mill tools would contain 3 or 4 cutting teeth for a further increase in productivity, but this would lead to slightly inaccurate form generation. With corrugator machine speeds increasing, this presented quite a negative effect. The solution was to mill perhaps 99% of the flute form and then draw cut the final 1%.

GRINDING of the final flute form was introduced in the early 1970ís. Chrome plating had shown that the roll wear on the flute tips could be slowed down, but the valleys and flanks had nearly the same wear rate characteristics as before. Corrugating rollers then required increased base metal hardness, and this new hardness required grinding to prevent skips and tears. Grinding presented its own production problems but these were rectified with time. The rolls were rough milled for most of their geometry, then mounted in the grinders to produce the final form. From a manufacturing standpoint, it then became a permanent struggle as grinding offered an avenue to utilize base rollers that were harder still, with grinding process improvements that would accommodate the base metal hardness increase. This battle matured when the alloy steel forging had a hardness of about 62 Rc. At this point, any additional hardness would lead to process cracking of the forging surface, regardless of the production process used to manufacture flute forms. Grinding was a very accurate, but extremely slow process, usually requiring over 150 production hours for each roll in the grinder.

CREEP FEED was a process that would allow the elimination of the rough milling operation, and allow the rolls to be set up only once as raw forgings, and removed as completely finished rolls. While others were looking at automated flexible machining multi-stations to achieve the results, the proponents of creep feed were searching for the Holy Grail, a single machine that could be set up accurately once, and also have the inherent flexibility with but one tool center to do the entire process, without the slowness of a conventional grind. Creep feeding was not invented by the corrugating industry. General Electric had developed the process in its Turbine Division to manufacture turbine blade "roots", where they could grind the complete depth in one pass. However, the GE process material was only 2" long, and at this point corrugating rollers were approaching 115" in length. Scale increase was not going to produce the desired results, as heat generation would anneal the base metal making it useless. Significant R&D effort was required.

Paul Weise, who was formerly the Chief Engineer with Rolls Royce Aerospace on the development of the Concorde engines, George Mills who was Chief Engineer for Langston, and the Materials and Process Engineering Department of the University of Bristol in the UK undertook the challenge. Their goal was to determine if a process could be developed that was independent of length and heat generation constraints. Their pioneering work in the late 80ís proved that it could be done, and the challenge was to find a manufacturer who could build the machine to do it. After several false starts, The Mattison Machine works of Rockford Illinois undertook the task of building such a machine. In the ensuing years, Creep feed grinding has proven that it can make the most accurate, dimensionally stable, roller surface in the industry.

 

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Last modified: 05/13/09