Business Process Improvement and Innovation Many Unhappy Returns

Over a six month period motor failures rose dramatically. Initial Pareto analysis showed that the majority of these failures were at a key customer where sales exceeded €4.3 million per annum. Customer dissatisfaction with rising failure rates caused management to be concerned at the risk of losing the customer to a competitor. A Six Sigma project was set up. The team discovered that the main failures were related to poor shaft flat surface finish, poor paint finish and poor quality cast rotors. They divided the project into three sub projects with separate Six Sigma project teams, all coordinated by one Black Belt and including a representative of the key customer on the teams. They found that the poor paint finish was caused by handling errors, rubbing during packing and incorrect paint mixing.
Gauge R & R studies showed that the surface finish measurement system was inadequate. Multi vari studies showed that poor surface finish was worst approximately midway down the flat length as a result of variation in tooling and operator cutting procedures. Milling machines were set incorrectly, programmed incorrectly and used worn cutters.

Solution

The shaft surface finish was improved by replacing milling components and purchasing a new arbor. A design of experiments on shaft flat surface finish, following on from the earlier multi-vari studies, quantified the precise relationship between spindle speed, feed rate and direction on the resulting surface finish. An improved surface finish measurement system was installed and user re-training was carried out. New paint handling and packing standard operating procedures and visual work instructions were developed and staff were trained how to apply them. Paint spray gun cleaning standard operating procedures were introduced. Improved casting process capability was achieved by replacing worn tooling.

Business Benefits

Direct failure costs reduced by 32%. Defect rates fell from 140,000 to almost zero. The €4.3 million sales per annum customer account was retained following specific feedback from the customer’s representative on the Six Sigma project team. The capability of both the shaft flat surface process and arbor process were improved dramatically.