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Manufacturing Processes > Forming Processes > Spinning

 

Spinning

 

Process description

Forming of sheet-metal or thin tubular sections using a roller or tool to impart sufficient pressure for deformation against a mandrel while the work rotates.

Materials

  • All ductile metals that are available in sheet form. The most common metals used are carbon steels, stainless steels, aluminum alloys, copper alloys and zinc alloys.
  • Used on a more limited basis are: magnesium, tin, lead, titanium and nickel alloys.
Spinning

Process variations

  • Tube spinning: thickness reduction of a cylindrical section on a mandrel, either internally or externally.
  • Flame spinning: oxyacetylene flame heats material prior to forming. Permits rapid forming of parts with thick sections.
  • Shear spinning: point extrusion process reduces thickness of starting blank or shape to produce the final form.

Economic considerations

  • Production rates are low, typically 10–30/h.
  • Lead times are short. Simple mandrels made quickly.
  • Material utilization is moderate. Main losses occur in cutting blanks.
  • Flexibility is high: formers are changed quickly and setup times are low.
  • Production volumes are viable from 10 to 10 000. Can be used for one-offs.
  • Tooling costs are low.
  • Equipment costs are moderate.
  • Labor costs are high. Skilled labor is needed.Finishing costs are low. Cleaning and trimming required.

Typical applications

  • Flanged, dished, spherical and conical shapes
  • Nose cones
  • Missile heads
  • Bells
  • Light shades
  • Cooking utensils
  • Funnels
  • Reflectors

Design aspects

  • Complexity is limited to thin-walled, conical, concentric shapes. Typically, the diameter is twice the depth.
  • Cylindrical or cup-shaped pieces are the most difficult of the simple shapes.
  • Oval or elliptical parts are possible, but expensive.
  • Material thickness, bend radii, depth of spinning, diameter, steps in diameter and workability of the material are important issues in spinning.
  • Radii should be at least 1.5 times the material thickness.
  • Stiffening beads should be formed externally rather than internally.
  • No draft angle is required.
  • Undercuts are possible, but at added cost.
  • Maximum section is 75mm for automated spinning, but approximately 6mm for hand spinning.
  • Minimum section=0.1 mm.
  • Sizes ranging 16mm–17.5 m.

Quality issues

  • Skill and experience are required to cause the metal to flow at the proper rate avoiding wrinkles and tears.
  • Streamlined or smooth curves and large radii are an aid both to manufacture and improved appearance.
  • Associated problems are blank development and proper feed pressure.
  • Grain flow and cold working give good mechanical properties.
  • Surface detail is good.
  • Surface roughness ranging 0.4–3.2 µm Ra.
  • A process capability chart showing the achievable dimensional tolerances is provided.

costing