Optimizing and Controlling Processes

- Statistical Process Control (SPC)- Control Charts

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Statistics

What is Statistics? o A branch of mathematics used to summarize, analyze, and

interpret a group of numbers or observations.

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Process Control

o What is it? Process Control consists of the systems and tools used to ensure that processes are well defined, performed correctly, and maintained so that the completed product conforms to established requirements.

o Process Control is an essential element of managing the production floor to ensure the Quality, safety….etc and reliability of the Out put.

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Statistical Process Control Defined

o Statistical Process Control (SPC) is a method for monitoring, controlling and, ideally, improving a process through statistical analysis. SPC is applied in order to monitor and control a process.

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Reasons for Statistical Process Control

o The Reasons for SPC is to improve product quality and simultaneously reduce costs, and to improve product image in order to successfully compete in world markets.

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Statistical Process Control Benefits

o Quality of the end product or service can be detected -monitored and corrected on line.

o To reduce waste . o To ensure better Quality output-products/service.. o SPC also indicates when an action should be taken in a

process, but it also indicates when NO action should be taken, weight control

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Steps Involved In Using Statistical Process Control

o Proper Statistical Process Control starts with planning and data collection. Statistical analysis on the wrong or incorrect data is rubbish, the analysis must be appropriate for the data collected.

o Be sure to PLAN, then constantly re-evaluate your situation to make sure the plan is correct.

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Where can Statistical Process Control be used ?

o Statistical Process Control can be used anywhere measurements and performance specifications are utilized Statistical Process Control is mostly associated with Manufacturing But… can also be used in:– Marketing– Medical/Healthcare– Service Industries– And many other fields

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Statistical Process Control

Types of Variation: :o Special Cause Variation

(something changed)

o Common Cause Variation(normal variation)

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Steps Involved In Using Statistical Process Control

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Steps Involved In Using Statistical Process Control

Plano Identify the problem and the possible causes. The QC tools described in

this manual can help organizations identify problems and possible causes, and to prioritize corrective actions.

Doo Make changes designed to correct or improve the situation.

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Steps Involved In Using Statistical Process Control

Studyo Study the effect of these changes on the situation. This is where control

charts are used – they show the effects of changes on a process over time. Evaluate the results and then replicate the change or abandon it and try something different.

Acto If the result is successful, standardize the changes and then work on

further improvements or the next prioritized problem. If the outcome is not yet successful, look for other ways to change the process or identify different causes for the problem.

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Elements of a Successful SPC Program

o Management Leadershipo A Team Approacho Emphasis on reducing variabilityo successful Communication results throughout organization

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(SPC)- 7 BASIC TOOLS

1. Check Sheet 2. Stratification 3. Scatter Diagram 4. Histogram 5. Pareto Chart 6. Control Chart 7. Cause and Effect Diagram

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Control charts Description

o Control chart is a tool used to study how a process changes over time. Measurements are plotted in time order.

• A control chart always has: : o a central line for the averageo an upper line for the upper control limito a lower line for the lower control limit

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Control charts features

Control charts have four key features:1. Data Points2. The Average or Center Line3. The Upper Control Limit (UCL)4. The Lower Control Limit (LCL)

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Control charts o Show the variation in a measurement during the time period

that the process is observed.o Monitor processes to show how the process is performing and

how the process are affected by changes to the process. This information is then used to make quality improvements.

o Help to identify special or assignable causes for factors that impede peak performance.

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Statistical Basis of the Control Chart

Types the control chart:o Variables Control Charts– These charts are applied to data that follow a continuous

distribution (measurement data).o Attributes Control Charts– These charts are applied to data that follow a discrete

distribution.

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Statistical Basis of the Control Chart

Variables Control Charts :o measure length, weight, temperature o measure variability in lengthAttributes Control Charts :o Good / bado works / doesn’t

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When to Use a Control Chart?

o When controlling ongoing processes by finding and correcting problems as they occur.

o When determining whether a process is stable (in statistical control).

o When determining whether your quality improvement project should aim to prevent specific problems or to make fundamental changes to the process.

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Sampling Plan

o A sampling plan is a detailed outline of which measurements will be

taken at what times, Sampling plans should be designed in such a

way that the resulting data will contain a representative sample of

the parameters of interest and allow for all questions

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Types of Sampling Plans

Single-Sampling Plan

• A decision to accept or reject a lot based on the results of one random sample from the lot.

Double-Sampling Plan

A plan in which management specifies two sample sizes and two acceptance numbers.

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Sequential-Sampling Plan

A plan in which the consumer randomly selects items from the lot and inspects them one by one.

Sampling by Attribute Sampling by Variable

Types of Sampling Plans

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Thank You!

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