100536263 managing quality
DESCRIPTION
managing qualityTRANSCRIPT
Managing Quality
• According to J.M. Juran: Quality is “Fitness for use”
• According to Philip Crosby: Quality is “Conformance to specifications”
Quality
Meeting, or exceeding, customer requirements now and in the future.
Dimensions of Quality
QUALITY
Quality of Design
• Determined before the product is produced
• Determined by market research• Translates the “requirements” of
customers into specifications
Quality of Conformance
Producing a product that meets the specifications
The Quality Cycle
MARKETINGInterprets customer needsWorks with customer to
design product to fitoperations
Interpretation of needs
CUSTOMERSpecifies quality needs
Needs
OPERATIONSProduces the product or
services
QUALITY CONTROLPlans and monitors
quality
Product
ENGINEERINGDefines design conceptPrepares specifications
Define qualitycharacteristics
Specifications
Implementation of quality improvement
Define quality attributes on the basis of customer needs
Decide how to measure each attributeSet quality standardsEstablish appropriate tests for each standardsFind and correct causes of poor qualityContinue to make improvements
Quality Costs
Quality Costs are classified into four categories:
• External failure costs,• Internal failure costs,• Appraisal costs, and• Prevention costs.
Statistical Process Control
• Assignable Causes,
• Random Causes.
Process Control Chart
x
y
Time
Upper control limit (UCL)
Center line (CL)
Lower control limit (LCL)
Average + 3 standard deviations
Quality measurement
average
Average - 3 standard deviations
Mean Charts
• The Goliath Tool Company produces slip-ring bearings, which look like flat doughnuts or washers. They fit around shafts or rods, such as drive shafts in machinery or motors. In the production process for a particular slip ring bearing the employees have taken 10 samples of 5 slip ring bearings (i.e., n=5). The individual observations from each sample are shown as follows:
Sample Observations1. 5.02 5.01 4.94 4.99 4.962. 5.01 5.03 5.07 4.95 4.963. 4.99 5.00 4.93 4.92 4.99 4. 5.03 4.91 5.01 4.98 4.895. 4.95 4.92 5.03 5.05 5.016. 4.97 5.06 5.06 4.96 5.037. 5.05 5.01 5.10 4.96 4.998. 5.09 5.10 5.00 4.99 5.089. 5.14 5.10 4.99 5.08 5.0910. 5.01 4.98 5.08 5.07 4.99
The company wants to develop mean and R-chart to monitor the process variability.
Control Charts for Attributes
• An electronic company manufactures several types of cathode ray tubes on a mass production basis. During the past month, tube type A has caused considerable difficulty. The following table contains data from 21 days of this troublesome period. 100 units are inspected each day. Compute the central line and 3-sigma control limits for a p-chart for this tube process.
Day Fraction Day Fraction Rejected Rejected
1 .22 12 .462 .33 13 .313 .24 14 .244 .20 15 .225 .18 16 .226 .24 17 .297 .24 18 .318 .29 19 .219 .18 20 .2610 .27 21 .2411 .21
C-chart• The Ritz Hotel has 240 rooms. The hotel’s housekeeping department is
responsible for maintaining the quality of the rooms’ appearance and cleanliness. Each individual housekeeper is responsible for an area encompassing 20 rooms. Every room in use is thoroughly cleaned and its supplies, toiletries, and so on are restocked each day. Any defects that the housekeeping staff notice that are not part of the normal housekeeping service are supposed to be reported to the hotel maintenance. Every room is briefly inspected each day by a housekeeping supervisor. However, hotel management also conducts inspection tours at random for a detailed, thorough inspection for quality-control purposes. The management inspectors not only check for normal housekeeping service defects like an inoperative or missing TV remote, poor TV picture quality or reception, defective lamps, a malfunctioning clock, tears or stains in the bedcovers or curtains, or a malfunctioning curtain pull. An inspection sample includes 12 rooms, i.e., one room selected at random from each of the twelve 20-room room blocks serviced by a housekeeper. Following are the results from 15 inspection samples conducted at random during a 1 month period:
• Sample Number of Defects
1 12 2 8 3 16 4 14 5 10 6 11 7 9 8 14 9 13 10 15 11 12 12 10 13 14 14 17 15 15
The hotel believes that approximately 99 percent of the defects are caused by natural, random variations in the housekeeping and room maintenance service, with 1 percent caused by nonrandom variability. They want to construct c-chart to monitor the house keeping service.