Search results

The main purpose of this paper is to explore the use of solid lubricant during orthogonal machining of carbon steels. This is a pioneer work in Nigeria. Most works have been on oblique cutting using conventional oil as lubricants.

Different steels (low, medium and high carbon) were machined at different cutting conditions and tool geometries to determine the effects on surface characteristics while applying solid lubricant.

The results showed considerable improvement in the surface finish with the use of solid lubricant. There was also a decrease in surface roughness values as compared to wet machining.

Further works on solid lubricant's effects on cutting force and residual stress could be done.

From the findings of this work, solid lubricant use can be advocated as a better alternative to conventional cutting fluid. It is easily recoverable from the chips after machining.

So far, in Nigeria, solid lubricant has not been exploited as coolant during machining. This paper will be a platform for other researches on solid lubricants as coolant during cutting/machining in Nigeria.

This study aims to focus on proposing a new memory-type chart called progressive mean exponentially weighted moving average (PMEWMA) control chart. This memory-type chart is an improvement on the existing progressive mean control chart, to detect small and moderate shifts in a process.

The PMEWMA control chart is developed by using a cumulative average of the exponentially weighted moving average scheme known as the progressive approach. This scheme is designed based on the assumption that data follow a normal distribution. In addition, the authors investigate the robustness of the proposed chart to the normality assumption.

The variance and the mean of the scheme are computed, and the mean is found to be an unbiased estimator of the population mean. The proposed chart's performance is compared with the existing charts in the literature by using the average run-length as the performance measure. Application examples from the petroleum and bottling industry are also presented for practical considerations. The comparison shows that the PMEWMA chart is quicker in detecting small shifts in the process than the other memory-type charts covered in this study. The authors also notice that the PMEWMA chart is affected by higher kurtosis and skewness.

A new memory-type scheme is developed in this research, which is efficient in detecting small and medium shifts of a process mean.