QUALITY CONTROL

PRESENTED BY RAZIA HAMEED

2015-AG-194

QUALITY CONTROL

“Quality control is the regulatory process through which we measure actual quality performance, compare it with standards, and act on the difference”

What is QC Tools? To make rational decisions using data

obtained on the product, or process, or from the consumer, organizations use certain graphical tools.

Graphical methods are easy to understand and provide comprehensive information; they are a viable tool for the analysis of product and process data.

7 Basic Tools• Pareto Chart• Check sheet• Cause & Effect Diagram• Control Chart• Histogram• Scatter Diagram• Stratification or Flow chart

Pareto Chart Pareto chart, named after Wilfredo Pareto, is a type of chart that contains both bars and a line graph, where individual values are represented in descending order by bars, and the cumulative total is represented by the line.

Check sheet The check sheet is a form (document) used to collect data in real time at the location where the data is generated. The data it captures can be quantitative or qualitative. When the information is quantitative, the check sheet is sometimes called a tally sheet.

Cause & Effect Diagram Common uses of the diagram are product design and quality defect prevention to identify potential factors causing an overall effect. Each cause or reason for imperfection is a source of variation. Causes are usually grouped into major categories to identify these sources of variation.

Control ChartsThe control chart is a graph used to study how a process changes over time. Data are plotted in time order. A control chart always has a central line for the average, an upper line for the upper control limit and a lower line for the lower control limit.

Histogram A histogram is a graphical representation of the distribution of numerical data. It is an estimate of the probability distribution of a continuous variable (quantitative variable) and was first introduced by Karl Pearson

Scatter DiagramAlso called: scatter plot, X–Y graph. The scatter diagram graphs pairs of numerical data, with one variable on each axis, to look for a relationship between them. If the variables are correlated, the points will fall along a line or curve. The better the correlation, the tighter the points will hug the line.

Flow ChartA flowchart is a formalized graphic representation of a logic sequence, work or manufacturing process, organization chart, or similar formalized structure. Flowcharts use simple geometric symbols and arrows to define relationships.

Causes of Variation in QualityCHANCE CAUSES

1. Machine vibrations2. Voltage variations3. Composition variation of material, etc.

ASSIGNABLE CAUSES1. Lack of skill in operation2. Wrong maintenance practice3. New vendors4. Error in setting jigs and fixtures5. Raw material defects