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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.
Forging 20
2. Fillet and Corner Radii
Die Cavity Design FactorsDie Cavity Design Factors
Forging 21
- Straight die - Simple locked die - Compound locked die - Counter locked die
3. Parting Line
Die Cavity Design FactorsDie Cavity Design Factors
Forging 22
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
Forging 23
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
Forging 25
Forging 26
Flash Design
• Flash thickness - s
• Flash land - b
• Die-land Ratio - b/s
Forging 27
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
Forging 28
3. Neuberger and Mockel
4. Vieregge
5
1
0
d0.017d s 0
3h0 drhdd
30
sb
020 2/21
Forging 29
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
Forging 30
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
Forging 32
New Trends in Forging Technology
1. Liquid forging (THIXO FORMING)
2. Isothermal forging
3. Powder forging
4. Orbital forging
5. Incremental forging