Forging 17

Advantages of Press Forging over Drop Forging

- Press forging is quieter than drop forging.

- Press forging is faster (one operation).

- Alignment of the two die halves can be easily maintained.

- Structural quality of the product is superior.

- More accurate parts are obtained.

Forging 18

Machine Forging

- The quality of the forging is better.

Advantages

Limitations

- Not convenient for heavy job, due to handling difficulty.

- Forging machines have a higher productivity and their maintenance is much cheaper.

- The upsetting process can be automated.

- Intricate, nonsymmetric jobs are difficult.

- The maximum diameter is limited to 25 cm.

Forging 19

Die Cavity Design FactorsDie Cavity Design Factors

1. Draft

3o - 7o for external surfaces

5o - 10o for internal surfaces

1o if automatic ejectors are employed

Is the angle of taper put on all sides to facilitate its quick removal from the die cavity after forging.

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2. Fillet and Corner Radii

Die Cavity Design FactorsDie Cavity Design Factors

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- Straight die - Simple locked die - Compound locked die - Counter locked die

3. Parting Line

Die Cavity Design FactorsDie Cavity Design Factors

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4. Shrinkage and Die wear

For steel, shrink allowance is about 16 mm per metre.

For forging weight up to 4.5 kg., die wear allowance is 0.4-0.8 mm.

For forging weight 9 kg.-22.5 kg., die wear allowance is 1.6-2.4 mm.

Die Cavity Design FactorsDie Cavity Design Factors

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5. Mismatch

6. Finish Allowance

Die Cavity Design FactorsDie Cavity Design Factors

Forging 24

Force - Travel Diagram Basic types of Material Flow

Closed Die Forging

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Flash Design

• Flash thickness - s

• Flash land - b

• Die-land Ratio - b/s

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sA0.015 s

1. Bruchanov and Rebelski

b/s from table 13.8

Determination of Die Land Ratio

2. Voigtlander

00.016d s

0d63

sb

Determination of Die Land Ratio

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3. Neuberger and Mockel

4. Vieregge

5

1

0

d0.017d s 0

3h0 drhdd

30

sb

020 2/21

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mA = mE+mG+mZ

mA - mass of initial stock in kg. mE - mass of forged part in kg. mG - mass of flash material mZ - mass of fiery particles

mA = W. mE

Ref. - H.Tschatsch, Praxiswissen Umformtechnik, Vieweg, 1997. (in German)

Initial Stock Size

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Kf1 = resistance to deformation at 1 s-1

Stress, Force and Work

- Strain rate 0h

V

- Resistance to deformation m

fk f1k

- Resistance to deformation at the final stage

fkY wek

- Maximum Force wed kA F

- Work F

fhm kV W

Average strain

0

Vn

hAdhm

Forging 31

Example

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New Trends in Forging Technology

1. Liquid forging (THIXO FORMING)

2. Isothermal forging

3. Powder forging

4. Orbital forging

5. Incremental forging