Qimpro Convention 2008: Winner of the QualTech Prize
14 Aug 2008
Godrej & Boyce Manufacturing Co.
Presenter: Hitesh Kakkar, Associate General Manager
Improvement of "first pass yield" by 87 per cent
Background
Over a century old, Godrej & Boyce started out in 1897 as a lock maker, and later diversified into safes, security equipment, toilet soap and vegetable oil. The company's appliance division manufactures and/or marketing refrigerators, washing machines, air conditioners, DVD players and microwave ovens.
The company has won a number of award in recent times, including the Reader's Digest survey in 2006 which awarded Godrej Appliances Gold in the Refrigerator category for being the most trusted brand. It has also won the CNBC Consumer Awaaz Award for the most preferred refrigerator for the second time in 2006, as in the previous year.
Introduction
The case pertains to the manufacture of refrigerators. The valve plate assembly forms an integral part of a compressor. Compressors with defective valve plate assemblies are rejected, resulting in a drop in the "first pass yield", or FPY in the compressor assembly department. That in turn adversely impacts the throughput of the compressor manufacturing plant.
The objective of the project was to improve this first pass yield in the compressor assembly department from the existing 51.5 per cent to 95 per cent.
Diagnosis and remedies
The team initiated the project with the identification of all possible causes through a process mapping exercise, and then plotting a fish-bone diagram. They then used the six sigma approach and the Shainin design of experiment (DOE) tools to pinpoint major causes for valve plate assembly defects.
Using Paired comparison analysis, a technique for working out the relative importance of different options, the team went about finding out whether the `problem' was caused due to the 'assembly process', or due to 'any of the components in the assembly'.
The team then used the component search technique to find out which particular component was the cause of the problem. This technique relies on interchanging one component at a time between a defective and a non-defective assembly, followed by a measuring of the responses. This was then followed by a paired comparison to pinpoint the dimension (surface finish of seat) of the component causing the problem.
The existing process tolerance for the surface finish of the valve plate seat was at 0.40 Ra, while the paired comparison showed that the leakage would be zero if the surface finish was maintained within 0.23 Ra.
As the process capability test showed that the current process was not capable of providing the new specifications of the surface finish consistently, a burnishing operation was introduced in the process to achieve the required surface finish of the valve plate seat. Variation analysis was then carried out to check for consistency of the newly introduced burnishing process.
Sustaining the gains, and the benefits
The team updated the new specification of the surface finish, and also updated the quality plan in the controlled ISO9000:2000 document with the new specification of the surface finish and the burnishing process. A pre-control run chart was also introduced to monitor the process.
The direct benefits of the process was an improvement in the first pass yield by 87 per cent, from 51.5 per cent to 95.8 per cent, along with financial savings of Rs22.5 lakh per annum at the Mohali unit. Other intangible benefits include an increase in customer satisfaction on account of lower power consumption, team work at the plant, higher motivation levels amongst employees, a first hand learning and exposure to the power of the Shainin DOE tools, and knowledge sharing.
