Feintool - Orbital technology

Basic principles 

In the plastic metal forming processes, of which orbital forging is one, the parts are usually formed in one or more steps. It is common today that we strive for cold forming ? i.e. upsetting or extrusion of the slugs at room temperature. This has the following economic and technological reasons:

• Elimination of heating equipment and related energy consumption 
• Increased strength of the finished part
• Improved accuracy and surface finish

In cold forming, the friction on the die surface restricts the radial flow of the material. The stress is the highest in the centre and decreases towards the edge of the piece part. The max. stress (ómax) increases with the surface friction. In conventional cold forming, ómax can be several times higher than the yield point (óF). While in conventional cold forming the force is applied over the entire surface of the piece part, in orbital forging it is applied only on a small segment. The orbiting upper die rolls over the piece part. Therefore, friction is reduced substantially and the metal can flow much easier in radial direction (rolling friction instead of sliding friction).The max. stress (ómax) is only slightly higher than the yield point (óF). Since the contact surface and the friction are much smaller in orbital forming, the force (F) required for forming is also much lower. Compared to conventional cold forming, the orbital forging process offers the following advantages:

• smaller presses (investment, space requirement)
• smaller stresses in dies (tooling costs)
• longer die life
• reduction of noise and vibrations

The material is formed between the upper and lower dies while the upper die is orbiting. Forming force is therefore applied only to a portion of the billet. The area under pressure moves in a rolling motion over the entire workpiece, thus creating a forming action. The upper die does not rotate. 

y = Orbital angle
1 = Billet
2 = Finished part
3 = Upper die
4 = Lower die
5 = Ejector

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