Chap 16 Cutting Tools for Machining Chap 16

Chap. 16 Cutting Tools for Machining 산업시스템공학과 제조공학

Chap. 16 Cutting Tools for Machining

16 -1 Cutting Tools

16 -1 Cutting Tools

16 -1 Cutting Tools

16 -1 Cutting Tools

16 -4 Tool Failure and Tool Life Tool failure의 2가지 Type n ⅰ) slow-death : gradual tool wear - flank wear, crater wear n n ⅱ) sudden-death : 부러짐, 기계에 충격 tool 마모 하면, tool geometry 변경 → cutting force, power, surface finish, dimensional accuracy

16 -4 Tool Failure and Tool Life

16 -4 Tool Failure and Tool Life

16 -4 Tool Failure and Tool Life n wf : permissible tool wear on the flank n wf=0. 025～ 0. 03“ , 공구 마모 판정

16 -4 Tool Failure and Tool Life

16 -4 Tool Failure and Tool Life Tool Change time의 check n ⅰ) 정상상태에서 cutting 시간의 합 n ⅱ) tool wear의 monitoring n ⅲ) 절삭 volume의 누적합

16 -4 Tool Failure and Tool Life Taylor’s tool life model T : [min], V : [sfm] n n : exponent, tool material에 따른 상수 work material, 절삭조건에 영향을 받음 C : work material, feed, 모든 input parameter에 따른 상수

16 -4 Tool Failure and Tool Life 양변에 log를 취하면

16 -4 Tool Failure and Tool Life

16 -4 Tool Failure and Tool Life 예) V 1=1260, T 1=100 V 2=1000, T 2=250 그림 참조 n=0. 25 ∴

16 -4 Tool Failure and Tool Life n HSS의 n = 0. 14 ～ 0. 16 n uncoated carbide의 n = 0. 21 ～ 0. 25 n Ti. C = 0. 3 n polydiamond = 0. 33 n Ti. N = 0. 35 n ceramic coated = 0. 4

16 -4 Tool Failure and Tool Life n one tool material로 3 종류의 피삭재 절삭 시, 같은 slope 형성 n C는 work material에 따라 변동 n tool life가 1분일 때 C = V

16 -4 Tool Failure and Tool Life

16 -4 Tool Failure and Tool Life n n n, m, p : exponent K' : constant f : feed d : depth of cut

16 -5 Economics of Machining n tool life : cutting speed에 매우 큰 영향 (feed, depth of cut 보다) n speed 50%증가 → tool life 90% 감소 n feed 50%증가 → tool life 60% 감소 n depth of cut 50% 증가 → tool life는 15% 감소 n speed 증가 → cutting 시간 단축 tool 교환시간 증가

16 -5 Economics of Machining -Turning의 경우 n n n Ro : operator cost [￦/min] Rm : Machine rate [￦/min] tl : Handling time [min] tch : average tool change time [min] tc : cutting time [min] nt : tool change 횟수/unit piece (=L)

16 -5 Economics of Machining -Turning의 경우 n n n n Nt : unit piece/tool n : Taylor's tool life exponent C : Taylor's tool life constant B' : cutting path length = π∙D∙L/fr Ct : tool cost/cutting edge [￦/edge] T : tool life [min] V : cutting speed [m/min]

16 -5 Economics of Machining 4 Cost elements ① Handling cost : (Ro + Rm) tl ② Cutting cost : (Ro + Rm) → 소요시간 ③Tool change cost: (Ro+Rm)tchㆍnt = ④ Tool cost : Ctㆍnt = →tool 교환횟수

16 -5 Economics of Machining 1) Minimum cost Model n total cost = ①+②+③+④ =

16 -5 Economics of Machining n From Tool life equation

16 -5 Economics of Machining 2) Maximum Production Model (Minimum Production Time) Time elements : (1 unit piece를 절삭할 때) ① Handling time = tl ② Cutting time = ③ Tool changing time =

16 -5 Economics of Machining Total unit time =