BOOK REVIEW

Reenesh Jain

Shiv Guru Ashish

Inspections and the Structure of Production

This chapter talks about the Five elements of production which are objects of production, agents

of production, methods, space and time. They are akin to five Ws and one H where Objects of

production are What, Agents of production-Who, Methods of production-How, space-Where and

Time-When. To this an additional element of Why can be added. The process is a flow which

converts raw materials into finished goods. Processes are categorized into Work, Transportation,

Inspection and Delay. The chapter negates the common belief that process refers to large units of

analyses and operations to small. It says that process are very different from operations. The

process according to Shingeo is an integrated flow of objects beyond which people and machines

appear while looking from operations point of view various goods and appear on other side of

workers and machines.

The chapter discusses the conflict between Processes and Operations. It says that the processes are

customer focused and the operations are efficiency focused. According to the author too much

focus on either of them is undesirable and its responsibility of frontline supervisors to keep these

opposing demands in harmony. It says that the operations supplement the processes which attain

the principle goals of organization. The visibility of operations being high obscures the processes.

So if the process functions are inadequate the production cannot achieve much success.

Significance of Inspections

The inspections reveal and prevent defects in course of work, transportation and delays. However

to avoid inspections becoming a wasteful activity it is necessary to examine why the inspection is

being conducted. Various types of inspections and the differences between them have been

discussed.

Management functions and quality control

The Author talks about how management functions can be divided in terms of following stages:

1. Action

2. Movement from individual to group activity

3. Five categories of executive management

Action: Action has 7 stages:

1. Volition: The choice to start some new task or execute a decision

2. Policy: Set by a desire to do a specific task and a desire to do it in a specific way

3. Planning: For giving concrete shape to the policy

4. Execution: Actual Processes and operations

5. Control: For ensuring that processes and operations faithfully adhere to set standards

6. Monitoring : To check if there were any flaws in execution or planning

7. Satisfaction: Depending on the level of satisfaction new volition may be invoked

From individual activities to group:

As the organization grows, the responsibilities need to be divided. The executives handle volition,

policies and satisfaction. The managers take care of planning monitoring and control. Workers do

the actual execution of production process. The results of individual achievement affect the

organization as a whole.

Five Categories of Executive Management:

1. Technical: Ensuring technical capacity for design and manufacturing the product

2. Financial: Handling the requirement capital

3. Production

4. Marketing: To produce provided goods to market, close communication between

marketing and production is a must.

5. Personnel: Necessary to carry out the above four functions

Programming and planning help in setting standards for work conditions. Experimental planning,

methods prove useful in this process. However care needs to be taken that there are provisions for

linking the planning with control and execution. However perfect planning may not guarantee

perfect execution and control. Flaws in set standards, execution and deviations from standards

result in defects. If the control and execution are not carried in accordance with the planning then

defects will arise. Here the role of monitoring is important as it helps in comparing the results of

execution with the plans. By relaying information about defects they can be prevented in future.

However controlling will help you in quality maintenance not in quality improvement, for that you

will need to go back to planning stage. So anyone wishing to improve the quality will have to

consider poka-yoke at planning stage itself.

Inspections don’t reduce defects

This chapter talks about how sometimes the managers misinterpret inspection as defect prevention

technique rather than a defect detection technique. The author says that by employing more man

power and more rigorous inspection processes the most you can achieve is the reduction in number

of defects in delivered goods. Since the defects are generated during the process and the inspection

is done at the end of process, all you are doing is the discovery of defects so it is pointless to add

more workers hoping that inspection will reduce defects

Approaching the zero quality QC method

In this chapter the author talks about how he came across the Statistical quality control methods

like experimental planning methods, factor charts, histograms and control charts for informative

inspections. He found that how helpful these methods were in determining if the values were within

control limits and if the situation was normalized or not. His belief strengthened in the fact that

science of statistics was ultimate quality control method. The author also narrates how in the

factory of Yamada Electric he first discovered the method of Poka-Yoke when he came to know

about the issue of workers often forgetting to enclose a spring in the switch. It struck to him that a

method similar to check list can help in preventing the workers from forgetting to enclose the

spring. This made him realize that having some device that signals to the workers if they forget

something was the quickest road leading to attainment of zero defects. He gave the name Poka-

Yoke which was derived from Baka-Yoke (Fool-proofing in Japanese) because he found Baka-

Yoke demeaning in nature. Despite achieving good results from use of SQC he felt that there was

something missing as SQC was characterized by selective detection of abnormalities and then

taking a corrective action. To improve on this he came up with the idea of successive checks where

the person carrying out the next process will inspect the work of the predecessor. With help of

this he was able to bring down the inter-process defects to 0.016 which was around 6.5 percent

when only SQC methods were used. Gradually he realised the importance of 100% inspection

(SQC only used sampling inspection) to achieve zero defects. He realised that performing the

inspections at the source itself will eliminate the cause of defect because defects are result of some

condition or action. “Quality is the shadow cast by motion” is the phrase used by the author to

emphasize on the point that errors occur due to operating conditions (5 elements of production

discussed in the first chapter) so by controlling these functions zero quality control can be achieved

by use of Poka-Yoke. The basic concept of quality control system are

1. Use of source inspection

2. Use of 100 percent inspection rather than sampling inspections

3. Minimizing the time needed to carry out corrective actions

4. Use of Poka-Yoke devices

At the end of this chapter author concludes that use of statistics is extremely effective in planning

however it may not always be effective in control and execution phases. So SQC can be an

excellent technique for making methods more rational but is not the best approach for attaining

zero quality control.

Inspection system

Author has suggested three major inspection technique to identify the defects:

1. Judgment inspection 2. Informative inspection 3.Source inspection

Judgment inspection

It is lowest level of inspection. Main objective of this inspection is simply to find the defective

item in the process.

It is used to segregate finished product in defective or acceptable product after processing has been

completed. This method do not contribute significantly towards lowering the defect rate in the

plant. The purpose of this method is to keep defective item from moving on to customers or

subsequently processes.

Informative inspection

Informative inspection contains both defect detection and the feedback process to the process.

When a defect occurs, information to that effect is fed back to the work process involved. Based

on the feedback received action to correct the method of operation is done.

Informative inspection is divided into three categories:

Statistical Quality Control System (SQCS)

Successive Check System (Sucs)

Self-Check System (SeCS)

Statistical Quality Control System (SQCS)

In SQC system statistics is used to set control limits which differentiate between normal and

abnormal process. It includes control charts to reduce future defects by feeding back the

information about defects to the offending processes.

Two limits have to be established in using control charts:

1. Specification limits: Tolerance limit demanded by product function

2. Control limits: limits within which normal operation will fall.

If specification limits are greater than control limits, all items processed under usual work

condition may be satisfactory. But if specification limits are narrower than control limits, it is

possible that, portions of production outside the specification limits will show defects. If an

abnormality is observed, the information is fed back to the process where the abnormality

occurred.

There is two major drawbacks in the SQCS:

1. Abnormalities appear irregularly and randomly. Since we cannot predict when they will

show up, the probability that statistical sampling will find abnormalities is far lower than

100 % inspection.

2. Control chart involved a considerable time lag between the discovery of an abnormality

and the corrective action. During this time probably a substantial number of defects will

appears.

Successive Check System (SuCS):

Successive check is a quality inspection system where each person checks the work done by the

previous process. Theoretically, successive checks can accomplish 100% inspection.

For example, if A finishes processing an item, he or she passes it on to B at the next process. B,

first inspect the item processed by A and if it found non defective then B carries out the further

processing. If the defect is discovered in an item coming from previous process, the defective item

is immediately passed back to the earlier process.

Self-Check System (SeCS)

In Self-check system, actual workers are involved in conducting 100% inspection to check for

defects. This makes instant correction action possible since it permits abnormalities to be

discovered within the process where they occur rather than at subsequent processes.

Two major drawbacks in this system is:

1. Workers may forget to perform checks on their own.

2. They may compromise when inspecting items that they have worked on.

Source Inspection:

Source inspection is inspection method based on the idea of discovering errors rather than defects

and performing feedback and action at the error stage. This helps to keep those errors from turning

into defects. A combination of source inspection and mistake-proofing devices is the only method

to get zero defects.

Source inspections fall into two categories:

1. Vertical Source Inspection 2. Horizontal Source Inspection

Vertical source inspection is to control upstream processes in case where they contain the causes

of defects. Horizontal source inspection refers to an inspection method based on the idea of

detecting defect source within processes and then conduction inspection to keep errors from

turning into defects.

Poka Yoke System Function

Poka-yoke system fall into regulatory function categories, and setting function categories.

Poka-yoke regulatory function

Two regulatory function are performed by poka-yoke system

Control Method:

These are methods that, when abnormalities occur, shut down machine or lock clamps to halt

operations, thereby preventing the occurrences of serial defects.

Warning Methods:

In this case worker’s attention is captured by means of light or buzzer if any abnormalities occurs

in the system. This approach provides less powerful regulatory function than control methods since

defects will continue to occur if workers do not notice these signal.

Poka-yoke setting function

The setting function of poka-yoke system is divided into three sub categories:

Contact methods: In this method sensing devices detect abnormalities in product shape or

dimension by detecting whether a sensing device makes contact with a part or object within the

process.

Fixed value methods: This method is applied when a fixed number of operations are

required within a process, or when a product has a fixed number of parts that are attached to it.

Motion step methods: Detect whether a motion or step has happened within a certain period

of time.

%Uniqueness Test

Fist 1,000 words: 98%

Second 1,000 words: 95%