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Roll Piercing (New) (Manufacturing)

Rinng rolling is a specialized hot working process for making seamless thick-walled tubes. It utilizies two opposing rolls and hence ıt's grouped with the rolling processes. The process is basde on the principle that when a solid cylindrical part is compressed on its circumference, as in figure high tensile stresses are developed at its center. If compression is high enough, an internal crack is formed. In roll piercing, this principle is exploited by the setup shown in figure. compressive stresses on a solid cylindrical billet are applied by two rolls, whose axes are oriented  at slight angles (~6) from the axis of the billet, so that their rotation tends to pull the billet through the rolls. A mandrel is used to control the size and finish of the hole created by the action. The terms rotary tube piercing and Mannesmann process are also used for the tube-making operation. (M. Groover,  Fundamentals of Modern Manufacturing, pg.405)

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Flashless Forging (New) (Manufacturing)
İmpression-die forging is sometimes called cloesd-die forging in industry terminology. However, there is a technical distiction between impression-die forging and true cloesd-die forging. The distinction is that in closed-die forging, the raw workpiece is completely contained within the die cavity during compression and no flash is formed. The process sequence is illustrated in figur. The term flashless forging is appropriate to identify this process.

Flashless forging imposes requirements on process control that are more demanding than impression-die forging. Most important is that the work volume must equal the space in the die cavity within a very close tolerace. If the starting blank is too large, excessive pressure may cause damage to the die or press. If the blank is too small  the cavity won't be filled. Because of the special demands made by flashless forging, the process lends itself best to part geometries that are usually simple and symetrical and to work materials such as aluminium and magnesium and their alloys. Flashless forging is often classified as a precision forging process. (M. Groover, Fundamentals of Modern Manufacturing, pg. 412)

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