Question

A six-station rotary indexing machine performs the machining operations shown in the table below, with processing times and breakdown frequencies for each station. Transfer time is 0.15 min. A study of the system was undertaken, during which time 2000 parts were completed. The study also revealed that when breakdowns occur, the average downtime is 7.0 min. For the study period,

Station	Operation	Process Time	Pi( breakdown)
1	Load Part	0.78 min	0
2	Drill three holes	1.25 min	0.02
3	Ream two holes	0.90 min	0.01
4	Tap two holes	0.85 min	0.04
5	Mill Flats	1.32 min	0.01
6	Unload parts	0.45 min	0

determine: 1) Average hourly production rate______________. 2) Line uptime efficiency______________. 3) How many hours were required to produce the 2000 parts__

Answer 1

Solution:

Given, number of workstation (n) = 6, slowest workstation time T_s= 1.32 min. (Taken from the Table, processing time), Transfer time T_r = 0.15 min, Average downtime T_d =7.0 min

Frequency of Line stop F = n P_i = 6 (0+0.02+0.01+0.04+0.01+0) = 0.48 stops / cycle.

Ideal cycle time T_c = T_s + T_r = 1.32 +0.15 =1.47 min

Production time T_p = T_c + F* T_d = 1.47 + 0.48 * 7 = 4.83 min.

(1) Average hourly production rate

R_p = 1/ T_p = 60 / 4.83 = 12.42 parts/ hr.

(2) Line up-time efficiency

E= T_c / T_p =1.47 / 4.83 =0.3043= 30.43%

(3) Time required to produced 2000 Parts

T= 2000 / R_p = 2000 / 12.42 = 161.03 hr.

hence time required to produced 2000 parts is 161.03 hr.