Improvement of Overall Efficiency (UPH) of Assembly Production Line in Refrigerator Factory through Time Study and Kaizen-Based Line Balancing: A Case Study from Pakistan's Appliance Industry

Mian Farazul Haq; Sahar Noor

Authors

Mian Farazul Haq University of Engineering and Technology, Peshawar, Pakistan
Sahar Noor University of Engineering and Technology, Peshawar, Pakistan

Keywords:

Line Balancing, Time Study, Takt Time, Kaizen, Value Stream Mapping, Manpower Allocation

Abstract

Importance of Study: The following reasons explain why the study was conducted at local facilities: Unbalanced workstations and undocumented work procedures prevent many local facilities from operating at the desired level. The present study examines the general assembly line of the largest refrigerator manufacturing plant in Pakistan, which is currently operating at 80 units per hour (UPH) against a designed capacity of 120 UPH.

Novelty Statement: The study combines time study, Kaizen, line balancing, and manpower optimization into a single statistically validated model, which is rarely reported in the literature, particularly in the context of the appliance industry in Pakistan, using a real factory case.

Material and Method: The structured methodology adopted for improvement included detailed time study, bottleneck diagnosis using Yamazumi charts, station redesign based on Kaizen, line balancing, ergonomic interventions, and manpower reallocation across all 67 workstations.

Result & Discussion: Seven bottleneck stations were identified, with cycle times of 41–43 seconds, all exceeding the takt time of 28.125 seconds. Six stations were reduced to 27-28 seconds (or less) by Kaizen interventions. Station S44 (Helium Recovery) was reduced from 43 seconds to 29 seconds, just slightly above the takt time because of the minimum cycle time of the equipment, however, the ability to do parallel processing at S44 allowed the throughput at that station to be doubled, eliminating it as a station bottleneck. The line throughput increased from 80 UPH to 120 UPH (+50%), with the binding constraint eliminated. A paired t-test was then performed on the cycle times of all 67 stations, and the improvement was found to be statistically significant (t = 2.785, df = 66, p = 0.007). Labour Cost per Unit decreased by 33% (Rs 500 per unit to Rs 333 per unit) and the capacity grew by some 7,800 units per month.

Conclusions: It is seen that the use of time study and Kaizen along with line balancing can be used to overcome the large gaps in the efficiency achieved and the developed model can be used in other high volume assembly lines.

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