Metal Forging Chapter 3.13

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

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

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

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

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)

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)