Metal Spinning, Book 1, from which material for this presentation was taken, was published in 1975. It provides a basic introduction to the metal spinning process useful to engineers and buyers in designing and purchasing formed metal components. A new AMSA publication, now being readied for printing, will describe the latest state-of-the-art techniques and the high-tech CNC and other equipment available to implement them.
History
Metal spinning is one of the oldest techniques for the chipless production of circular hollow metal components. History records evidences that metal spinning was known to Egyptians of hieroglyphic days. Results of the craft appear in the histories of most countries since that time. The process was introduced into our country about 1840 and was first used almost exclusively for the production of fine gold, silver and pewter hollowware and chalices.
By the end of the century it was being used for making chandelier parts. Only the soft nonferrous metals were employed in industrial applications as late as the first World War. Around 1920 a few daring men of the industry began to experiment with tougher materials, heavier gauges, and larger diameters. Due to its versatility, metal spinning is often employed today for production of small, medium, and large lot sizes.
The Process
In metal spinning, a disc of metal is revolved at controlled speeds on a specialized machine similar in design to a machine lathe. Instead of the clamping chuck common on a machine lathe, a wood or metal spinning mandrel is used, the form of which corresponds with the internal contour of the part to be produced. The blank is clamped between spinning mandrel and a follower on the tailstock spindle. The mandrel, blank, and follower are then set in rotation. Spinning tools or spinning rollers are forced against the rotating blank by hand or auxiliary power. Employing a series of axial and radial (swivel) strokes, the blank is spun onto the mandrel causing the metal to flow to the shape of the desired part. Although the metal is usually cold when spun, it appears to flow somewhat like a piece of clay on a potter's wheel. With this forming technique, material thickness generally changes slightly from blank to finished component.
General Information
The blank diameter is generally larger than the diameter of the finished component, and its size is determined from the surface area of the finished part. Pressure on the spinning tool or roller may be exerted by hand, air or hydraulics. The availability of hydraulic spinning machines and automatic template-controlled devices has made metal spinning, normally associated with prototype and limited-production runs, competitive in the mass-production of many shapes. The use of precision templates and automatic machinery has also insured the repeatability of each part.
Because of the rotation, parts usually are symmetrical and circular in cross-section in the metal spinning process. However, many spun parts are cut into segments or welded into intricate assemblies that bear little resemblance to the original spun components.
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