Metal Forging

1. Metal Forging Chapter 3.13

2. Forging • Metal is shaped to a desired form through plastic deformation • Types: open die, impression die, ring rolling, rotary swaging, cold heading • Terms: upset forging, draft, parting line, flash, gutter, rib, web

4. Typical Characteristics • Controlled grain structure is primary benefit • High strength (high strength to weight ratio) • Seldom have internal blemishes • Size is limited by facilities • Machining operation required in most cases

5. Bralla ASM Metals Handbook Vol.9 http://www.heungkuk.co.kr/hk_eng_prod_forg.html

6. Economics • Economically viable in large quantities for impression die parts or small quantities for open dies parts (but lots of skilled labor) • Tooling cost – may be high for impression die • Labor cost – may be high for open die • Finishing costs can be moderate

7. Design Recommendations • Parting line choice is critical • Ideal – in one plane perpendicular to die motion (pg. 3.185) • Economical – one flat die, one w/ impression (Fig 3.13.6) • Minimize side thrust forces – keep parting line < 75 degrees from principal plane (pg. 3.185) • No undercuts (pg. 3.185) • Use parting line to control grain (Fig. 3.13.7) • Flow horizontally if possible (Fig. 3.13.7)

8. Design Recommendations • Draft angle per material (Table 3.13.2) • Avoid ribs and bosses that are high and narrow, webs that are thin w/ variable thickness (Fig. 3.13.9) • Fillets and rounds (Table 3.13.3) • Consider machining allowances (pg. 3.190) • Tolerances: length and width, die wear, die closure, match, straightness, draft, radii (pg. 3.191)