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Rotary Forging, General Forging Machine (GFM) and Swaging

Updated Wednesday, 22nd November 2017

A circular housing contains a rotating shaft (rotor) holding free moving anvils. At the end of each anvil is a die. The dies surround a centrally placed workpiece. Revolving around the rotor is a cage holding loosely rotating rollers. As the cage rotates, the rollers impact on the anvils, which effectively hammer the stationary workpiece into the required form. GFM is used to reduce the diameter of rods, tubes or pipes.

GFM rotary former

Diagram to demonstrate 'Rotary forging, General forging machine (GFM) and Swaging' see article Copyrighted  image Icon Copyright: The Open University

(Front elevation)

Diagram to demonstrate 'Rotary forging, General forging machine (GFM) and Swaging' see article Copyrighted  image Icon Copyright: The Open University

(Side elevation)

Rotary swaging

The workpiece is stationary, while the hammers rotate. Construction resembles a roller bearing. The anvils are free to move rapidly in a slot of the rotating shaft, and are thus hurled against the rollers which, in turn, knocks them back.

Diagram to demonstrate 'Rotary forging, General forging machine (GFM) and Swaging' see article Copyrighted  image Icon Copyright: The Open University Diagram to demonstrate 'Rotary forging, General forging machine (GFM) and Swaging' see article Copyrighted  image Icon Copyright: The Open University

Manufacture:

  1. The GFM rotary forging machine consists of four rotatable adjustable housings in which eccentric shafts drive the forging hammers at speeds up to 210 strokes min-1.
  2. Two manipulators, one on either side of the machine, are used to hold the workpiece.
  3. The four-hammer system contains the workpiece on all sides, which eliminates the tensile stresses developed in conventional hot forging.
  4. The high rate of working leads to heat generation to compensate for radiation losses, so that multiple passes can be used to produce a forging in a single heat. This leads to substantial energy and labour savings compared with conventional forging.
Diagram to demonstrate 'Rotary forging, General forging machine (GFM) and Swaging' see article Copyrighted  image Icon Copyright: The Open University

Materials:

  1. Can rotary forge or swage most forgeable materials.
  2. Some “difficult-to-forge” materials by conventional techniques can be rotary forged or swaged because of the prevention of tensile forces that would normally cause tensile cracking on upset surfaces.

Design:

  1. The GFM rotary forging technique gives greater precision than conventional hot forging techniques, which in turn reduces machining allowances and costs.
  2. Rotary swaging can produce exceptionally smooth surfaces to close tolerance.
  3. Tube can be drawn-out lengthwise, and the use of a mandrel can be employed to form internal contours inside the tube.
Diagrams to demonstrate GFM and Swaging - see article Copyrighted  image Icon Copyright: The Open University

See Also: Hot extrusion, Conform process and Orbital forging.

This article is a part of Manupedia, a collection of information about some of the processes used to convert materials into useful objects.

 

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