LEAN Basic Tools Concepts - Part 5

TOTAL PRODUCTIVE MAINTENANCEPurpose: To reduce scheduled and unscheduled down time from typical levels of 30% to below 5%
 
Preventive Maintenance: Maintenance that occurs at regular time or usage intervals
Predictive Maintenance: Maintenance that is performed based on signals or diagnostic techniques

•TPM Metrics
Operation Equipment Effectiveness or OEE = Availability Level X Operating Level
X Quality Level
MTTF: Mean time between failure
MTTR: Mean time to repair

When to use it -  When planned and unscheduled downtime are contributing to poor

How to do it -
Rework: Assess current operating conditions
•Evaluate machine/resource utilization, productivity, etc.
•Tally maintenance repair costs (parts and labor, extra training time, etc.)
Phase 1: Return equipment to reliable condition
1.Clean thoroughly
2.Place a defect tag (can be color coded) on all equipment showing categories of what needs to be done. Record in a project notebook.
3.Perform repairs
Phase 2: Eliminate breakdowns
1.Review defect tags from Phase 1
2.Eliminate factors leading to failure
3.Improve accessibility to machines/parts
Phase 3: Develop TPM database
1.Document all preventive and predictive maintenance activities
Phase 4: Eliminate defects
1.Provide for early detection of problems by training all relevant personnel in preventive and predictive maintenance techniques
2.Install visual controls (see slides 46-48)
3.Implement 5S housekeeping techniques (see slides 26–31)
4.Regularly review and improve machine performance Improve safety

MISTAKE PROOFING AND PREVENTION (POKA-YOKE)

Purpose : To prevent mistakes from occurring or making it impossible to pass mistakes on to the next step in the process

Examples: Mistake Prevention
•Machine operations that make it impossible or very difficult to produce a defective product. Does not require human assistance
•Electronic checklist built into a product or process/procedure
Mistake Proofing
•Devices or systems that either prevent the defects or inexpensively inspect each item to determine if it is defective
•Software programming that makes it impossible to move onto the next step without accurately completing prior steps
When to use it - When rework to correct errors or process delays downstream are hurting Process

How to do it - There are two basic Poka-yoke approaches
A.Control/Warning Approach
•Shuts down the process or signals personnel when an error occurs
•Dials, lights and sounds bring attention to the error
•Prevents the suspect work from moving on until the process step is complete
•Process stops when irregularity is detected (may be necessary if too costly to implement mistake proofing)
•High capability of achieving zero defects
B.Prevention Approach
•Employs methods that DO NOT ALLOW an error to occur or be produced
•Gives 100% elimination of mistakes (100% zero defects)
 
7 Steps to Mistake Proofing
1.Describe the mistake and its impact to customers
2.Identify the process step where the defect is discovered and the step where it is created
3.Detail the standard procedures where the defect is created
4.Identify errors in or deviations from standard procedure
5.Investigate and determine the root cause of deviations
6.Brainstorm methods to eliminate or detect the deviation early
7.Create, test, validate, and implement mistake proofing devices/procedures

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