Question

Define the concept of statistical process control

Explain briefly the rationale for SPC

What is meant by variation in processes?

Describe how the seven tools are used when implementing SPC.

Answer 1

• Statistical process control means statistical tools and techniques which are used to control process of the firm .Basically it is a quality control method which is used to control the quality of the product and maintain consistency in the process with improvement.

Rationale for SPC is to improve quality of the product by reducing cost.

Steps to follow for this are as follows:-

1.Continous improvement of process that will lead to improve quality of product and service.to improve process it is necessary to understand it and eliminate the unwanted variations.

2.Minimum wastage of googs should take place as due to this cost of good produced is decreased which will lead to enhancing the quality of the product.

3. Proper sampling must be conducted as it is less costly to check some samples as compared to checking each every unit produced.

Variation in proceses are of two types which occur thar are (a) controlled &(b)uncontrolled.

controlled variations are caused due to normal causes & uncontrolled variations are caused due to specific causes.

In case of normal causes the process is stable i.e we can predict the how the process will behave tomorrow on the basis of todays prediction and can take steps accordingly to stabilize it.

In case of special causes it is difficult to predict how the process will behave on the basis of today's prediction .

Seven tools used in SPC are:-

1.checksheets:-checksheets are used to find the frequency and location of area of failure.the team members collect data based on sample observations in order to identify patterns.it is an easy to understand method to learn how certain events occur.

2.stratification:-segregating a group of measurements ,observations,or any other data into subgroups on the basis of certain characteristics is known as startification.eg.1,2,3,4 machines are used in production so with help of startification method the observer will see in which machine the maximum breakdown is occuring .on the basis of this, more efforts are put to solve the problem of that particular machine and after that it pases to other machines.

3.Cause & Effect diagram:-The objective of cause and effect method is to cure the causes and not merely list the symptoms.

(A) It begins with agreeing on the effects.i,e Problem statement.

(B) Generate the causes with help of checksheets or brainstorming.

(C)Place the problem in the box category and add brainstormed ides.basically asking why does this happen for each cause.

(D)Identify the roots of causes of the problem by finding the factors that are repeated and finally take actions to solve them.

4.Pareto Analysis:-This technique is used for assessing uneven distribution of wealth. it is uses to differentiate between major fators that contribute towards the most unsatisfactory situations.Normally it is used to for fixing the priorities for selection of the problem to taken up serially from among those listed in brainstroming.

In some cases the listed problems are grouped depending upon the nature and their recurrence could be projected in terms of percentages.

5.Scatter Diagram:- It is a simple device for ascertaining whether two variables are related to each other .It is a dot chart . these are used to test the possible cause and effect relationship.They shoe whether relation exist if yes then what is the strength of correlation.

6.Histogram:- It displays the distribution of data by bar graphing the number of units of anything in seprate categories.It takes measurement of data and display it in disrtibution .It shows the negative or positive deviation from the skewnwss of the curve .It can shoe variability i.e how much spread is there in the curve,They start with unorganized set of numbers.

7.Control charts:-They are used to study a process when characteristics is a measurement such as processing time , waiting time , cost of revenue.They are more sensitive in detecting special cause variations .Control charts are an essential tool of continuous quality control. Control charts monitor processes to show how the process is performing and how the process and capabilities are affected by changes to the process. This information is then used to make quality improvements. Control charts are also used to determine the capability of the process.