The paper aims to investigate the waste in a job shop environment and proposes an assessment method aimed at helping companies to identify root causes of waste.
The seven wastes (overproducing; processing; inventory; transporting; producing defects; time waiting; and motion waste) and their relationships were explored. A waste matrix was developed to quantify in a percentage form the relationships among wastes and represents a probability that a certain type of waste will affect others or be affected by others. An assessment questionnaire was employed to allocate the source of waste and differentiate between the levels of waste. The waste matrix and the assessment questionnaire were incorporated in the assessment method to rank the existing waste in a job shop.
The developed model serves as guidelines for simplifying the search of waste problems and identifies opportunities for waste elimination. A case study was conducted to validate the model; and the results of the assessment and the real situation concur.
This paper has investigated a method to allocate waste, quantify it and discuss the relationships among wastes without quantifying the potential savings. Further research should be done in order to investigate the level of reduction in effort and time as a result of implementing the method.
The approach provides a method by which managers can identify the sources of waste, differentiate between the levels of waste and rank their significance.
The simplicity of the matrix and the comprehensiveness of the questionnaire contribute to the achievement of accurate results in identifying the root causes of waste. The new model provides an insight into on where to concentrate effort by weighing the contributions of the different waste types.
