Mistake Proofing

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Principles


Purpose

Mistake Proofing is used to implement methods that will ensure a process is defect-free all the time. It applies to any process where repetitive steps occur which could be skipped, performed out of order, or not conducted correctly. It ensures that tasks can only be done the right way.



Anatomy

mistake proofing principles

Reference: Quality Planning and Analysis

Terminology

A. Principle – There are 5 basic principles involved in mistake proofing

B. Objective – The main difference between each of the principles

C. How – A generic description of how the principle is implemented

D. Preference – Always use the highest principle possible

Planning - Part 1


Purpose

To serve as a guide to identify and implement mistake proofing devices to prevent errors or defects.

Anatomy

mistake proofing planning

Reference: Quality Planning and Analysis

Terminology

A. Details of Operation/Process Step, Product/Service or part identification and Date

B. Description of the defect which is the subject of the exercise

C. Separate descriptions of where, in the process, the defect is first made and detected

D. Graph of the rate of defect production as a function of time
E. Itemized list of process steps where defects are occurring. One step is entered in each box

F. For each defect-producing process step entered in the previous box, list the defects which occur at the specific step

G. For each defect-producing process step, list the possible causes for the production of the defect

H. Red Flag Conditions - Provision for special accounting for particularly dangerous or costly defect/error situations. Root Cause of the error or defect


Major Considerations

The Chart assumes a reactive effort, i.e. a problem already exists. We should, however, use the tool in a proactive mode, stopping defects from ever occurring by mistake-proofing products, services and processes at the design stage

Application Cookbook

1. Describe the defect or potential defect and indicate the defect rate

2. Identify the operation where the defect is, or can be, discovered

3. Identify the operation where the defect is, or can be, made

4. Detail the sequence of events in the standard method or operation

5. WATCH the operation being done and detail the steps that differ from the standard method

6. Identify error conditions that could be contributing to the defect (tools, environmental, gauging, etc.), and ask why the error occurs until the root cause is determined

7. Generate ideas for determining methods to eliminate the error Do not try to develop the device yet

8. Identify the device required to prevent the error or defect

9. Try out the device. If it doesn't work, try again

10. Test the device to make sure it worked. Ask operators for assistance in evaluating worst case scenarios

Planning - Part 2


Purpose

To serve as a guide to identify and implement devices to prevent errors or defects

Anatomy

mistake proofing planning

Reference: Quality Planning and Analysis

Terminology

A. Root Cause of the error or defect

B. For each defect-producing process step, brainstorm and list ideas for ways to eliminate the errors which occur at the specific step

C. Indicate where in the process the defect or error should be detected or prevented, either before it is made, as it is being made, or after it is made

D. Description of the improvement(s) for eliminating the defect or error

E. Current state of the process

F. Device or method for eliminating the defect or error

G. Cost of implementing the improvement

H. Length of time needed to install the improvement

I. Team members involved in the exercise


Major Considerations

The Chart assumes a reactive effort, i.e. a problem already exists. We should, however, use mistake proofing in a proactive mode, stopping defects from ever occurring by mistake proofing products, services, and processes at the design stage

Application Cookbook

1. Describe the defect or potential defect and indicate the defect rate

2. Identify the operation where the defect is, or can be, discovered

3. Identify the operation where the defect is, or can be, made

4. Detail the sequence of events in the standard method or operation

5. WATCH the operation being done and detail the steps that differ from the standard method

6. Identify error conditions that could be contributing to the defect (tools, environmental, gauging, etc.), and ask why the error occurs until the root cause is determined

7. Generate ideas for determining methods to eliminate the error Do not try to develop the device yet

8. Identify the Mistake Proofing device required to prevent the error or defect

9. Try out the Mistake Proofing device. If it doesn't work, try again

10.Test the device to make sure it is mistake proof. Ask operators for assistance in evaluating worst case scenarios

From Mistake Proofing to Six Sigma Tools.

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