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Lecture 30 - Total Quality Management (Continued). The contents of this chapter include all of the following: Variables and attributes, control charts for variables, parameters, control charts for attributes, tolerances, process capability, understanding continuous improvement, deming 14 points, TQM, seven quality tools, maintenance and reliability, reliability, product failure rate, providing redundancy, maintenance cost, total productive maintenance.
Lecture 30 Total Quality Management (Continued) Books • Introduction to Materials Management, Sixth Edition, J. R. Tony Arnold, P.E., CFPIM, CIRM, Fleming College, Emeritus, Stephen N. Chapman, Ph.D., CFPIM, North Carolina State University, Lloyd M. Clive, P.E., CFPIM, Fleming College • Operations Management for Competitive Advantage, 11th Edition, by Chase, Jacobs, and Aquilano, 2005, N.Y.: McGrawHill/Irwin • Operations Management, 11/E, Jay Heizer, Texas Lutheran University, Barry Render, Graduate School of Business, Rollins College, Prentice Hall Objectives • • • • • • • • • • • • • • • • Variables and attributes Control charts for variables Parameters Control charts for attributes Tolerances Process capability Understanding continuous improvement Deming 14 points TQM Seven quality tools Maintenance and reliability Reliability Product failure rate Providing redundancy Maintenance cost Total productive maintenance Variables and Attributes • Attributes data refers to quality characteristics that either conform to specification or do not (examples: visual inspection for color, missing parts, scratches, gonogo gauging) Either the part is within tolerance or it is not. Control Charts for Variables • • • The purpose of control charts is to help distinguish between chance variations and variations due to assignable causes Variables are characteristics that have continuous dimensions Control charts for the mean, (xbar), and the range, (R), are used to monitor processes that have continuous dimensions Control Charts for Variables • ✓ The xbar chart tells whether changes have occurred in the central tendency of a process The Rchart values indicate that a gain or loss in uniformity has occurred Parameters • • Two basic parameters used: – Mean measure of central tendency – Range measure of dispersion The range is defined as the difference between the largest and smallest items in one sample Control Charts for Attributes • • Attributes are typically classified as defective or nondefective Two kinds of attribute control charts: ① Those that measure the percent defective in a sample pcharts ② Those that count the number of defects per unit of output ccharts Tolerances • • Tolerances are limits of deviation from perfection and are established by the product design engineers to meet a particular design function Both the USL and LSL are related to the product specification and are independent of any process Two Types of Defect • • • Excessive Spread, Incapable Process – Range – Standard deviation Mean Shift Both the USL and LSL are related to the product specificationandareindependentofanyprocess VariablesandAttributes ã Variablesdatacanbemeasuredonacontinuousscale (examples:weight,dimensions,pH,temperature, pressure,etc.) Maintenance ỵ Two types of maintenance Preventive maintenance – routine inspection and servicing to keep facilities in good repair ỵ Breakdown maintenance emergency or priority repairs on failed equipment ỵ ImplementingPreventiveMaintenance Need to know when a system requires service or is likely to fail ỵ High initial failure rates are known as infant mortality ỵ Once a product settles in, MTBF generally follows a normal distribution ỵ Good reporting and record keeping can aid the decision on when preventive maintenance should be performed ỵ ComputerizedMaintenanceSystem Data Files Output Reports Equipment file with parts list Inventory and purchasing reports Equipment parts list Maintenance and work order schedule Equipment history reports Repair history file Inventory of spare parts Personnel data with skills, wages, etc Data entry – Work requests – Purchase requests – Time reporting – Contract work Cost analysis (Actual vs standard) Work orders – Preventive maintenan ce – Scheduled downtime – Emergency maintenan ce Maintenance Costs The traditional view attempted to balance preventive and breakdown maintenance costs ỵ Typically this approach failed to consider the true total cost of breakdowns ỵ Inventory ỵ Employee morale ỵ Schedule unreliability ỵ MaintenanceCosts Total costs Costs Preventive maintenance costs Breakdown maintenance costs Optimal point (lowest cost maintenance policy) Maintenance commitment Traditional View Maintenance Costs Costs Total costs Full cost of breakdowns Preventive maintenance costs Maintenance commitment Optimal point (lowest cost maintenance policy) Full Cost View Maintenance Cost Example Should the firm contract for maintenance on their printers? Number of Breakdowns Number of Months That Breakdowns Occurred Total: 20 Average cost of breakdown = $300 Maintenance Cost Example Compute the expected number of breakdowns Number of Breakdowns Frequency Number of Breakdowns Frequency 2/20 = 6/20 = 8/20 = 4/20 = Expected number of = breakdowns ∑ Number of breakdowns x Corresponding frequency = (0)(.1) + (1)(.4) + (2)(.3) + (3)(.2) = 1.6 breakdowns per month Maintenance Cost Example Compute the expected breakdown cost per month with no preventive maintenance Expected breakdown cost = Expected number of x breakdowns = (1.6)($300) = $480 per month Cost per breakdown Maintenance Cost Example Compute the cost of preventive maintenance Preventive maintenance cost = Cost of expected breakdowns if service contract signed Cost of + service contract = (1 breakdown/month)($300) + $150/month = $450 per month Hire the service firm; it is less expensive Increasing Repair Capabilities Well-trained personnel Adequate resources Ability to establish repair plan and priorities Ability and authority to material planning Ability to identify the cause of breakdowns Ability to design ways to extend MTBF How Maintenance is Performed Operator Maintenance department Manufacturer’s field service Depot service (return equipment) Competence is higher as we move to the right Preventive maintenance costs less and is faster the more we move to the left Total Productive Maintenance (TPM) Designing machines that are reliable, easy to operate, and easy to maintain ỵ Emphasizing total cost of ownership when purchasing machines, so that service and maintenance are included in the cost ỵ Developing preventive maintenance plans that utilize the best practices of operators, maintenance departments, and depot service ỵ Training workers to operate and maintain their own machines ỵ EstablishingMaintenancePolicies ỵ Simulation Computer analysis of complex situations ỵ Model maintenance programs before they are implemented ỵ Physical models can also be used ỵ ỵ Expert systems ỵ Computers help users identify problems and select course of action End of Lecture 30 ... employees ỵ Profits becoming losses ỵ Reduced value of investment in plant and equipment ỵ MaintenanceandReliability ỵ The objective of maintenance and reliability is to maintain the capability of the... Product Failure Rate (FR) Basic unit of measure for reliability Number of failures FR(%) = Number of units tested x 100% Number of failures FR(N) = Number of unit-hours of operating time Mean time between... printers? Number of Breakdowns Number of Months That Breakdowns Occurred Total: 20 Average cost? ?of? ?breakdown = $300 Maintenance Cost Example Compute the expected number of breakdowns Number of Breakdowns