Metal Sheet Spinning process | Advantages and Disadvantages of Spinning

Introduction

SPINNING is a method of forming sheet metal into seamless, axisymmetric shapes by a combination of rotation and force. On the basis of techniques used, applications, and results obtainable, the method can be divided into three categories: Manual spinning , Power spinning, Tube Spinning.

Sheet metal Spinning Process
Sheet metal Spinning Process
Applicability
Manual spinning is used to form flanges, rolled rims, cups, cones, and double-curved surfaces of revolution (such as bells). Several typical shapes formed by manual spinning are shown in Fig. 1. Products include light reflectors, tank ends, covers, housings, shields, and components for musical instruments. Manual spinning is also extensively used for the production of aircraft and aerospace components, often with mechanical assistance for increased force.
Classification Of Metal Spinning Processes:
Manual (Conventional) Spinning
  • Practiced by pressing a tool against a circular metal preform.
  • Involves no significant thinning of work metal; essentially a shaping process.
  • Used for prototype manufacture or in production runs less than 1000 pieces.
Power Spinning
  • Metal is deformed using high shear forces.
  • Use of automated CNC machines.
  • Significant thinning of metal preforms.
  • Suitable for high production runs.
Tube Spinning

Thickness of cylindrical parts reduced by spinning them on  cylindrical mandrel rollers.

Steps in Spinning Process

Step 1 :Metal Forming
This step involves the laying down of the material onto the mandrel.
It is accomplished with short inside to outside moves.Material gets easier to form as the part is closer to completion

 

Steps In Sheet Metal Forming Process
Steps In Sheet Metal Forming Process

Step 2 :Trimming 
Parts having been spun are trimmed at the end to blunt sharp edges and also to bring the component to the desired length.

Step 3 : Finishing

Finishing is done at very high RPMs (1200+) so that a minimum of force need be applied and verysmooth strokes can be used. The flat side of Duckbill spinning tool is used for straight surfaces an rounded side for curves and radii.

Sheet-metal Spinning Machine Specification: 
  • Machines for spinning are specified by the diameter and length of the largest component that can be spin
  • They are also specified by the maximum load that can be applied to the work.
  • The capacity of spinning machines ranges from 0.455m in diameter and 0.380m in length to 6m in diameter and 6m in length.
  • Metal spinning machines can be both vertical or horizontal.
  • Machines used for spinning large diameters, such as 1.8m or more are usually vertical.
  • Mostly lathe based machine tools ( both conventional and CNC-based) are employed for spinning operation.
  • Most modern machines used for spinning are at least semi-automated; that is, they are loaded and unloaded by the operator, but the entire spinning cycle is controlled automatically.
Advantages and Disadvantages
Manual spinning has several advantages over a competitive process such as press forming:
  • Tooling costs less, and investment in capital equipment is relatively small
  • Setup time is shorter
  • Design changes in the workpiece can be made at minimum expense
  • Changes in work metal composition or thickness require a minimum of tool changes
The disadvantages of manual spinning include:
  • Skilled operators are required, because uniformity of results depends greatly on operator skill
  • Manual spinning is usually slower than press forming
  • Available force is more likely to be inadequate in manual spinning than in press forming Equipment
Application Of Sheet Spinning :
The following are examples of products that can be manufactured by metal spinning:
  • Vases, baskets, basins and bowls.
  • Bottoms for tanks, hoppers and kettles.
  • Housings for blowers, fans, filters and fly-wheels.
  • Ladles, nozzles, orifices and tank outlets.
  • Cones, covers and cups.
  • Funnels, cylinders, domes and drums.
  • Rings, hemispheres and shells.
  • Vents, venturis and fan wheels.
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