Summary: Ppqc

Read the summary and the most important questions on PPQC

• 1 Introduction Scheduling

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• Four basic design decisions

  1.Direction of Flow
  -undirectional (flowshop)
  -Multidirectional (jobshop)
  2.Management structure
  -Product layout
  -Process layout
  3.Physical layout
  -Product ->
  -Dock ->
  -Process ->
  -Operator 
  4.Hierarchy
  Each unit can have multiple internal units in any flow, management structure  and layout.

• Product Layout Vs Process Layout

  Performance
  
  
  +/-
      Quality
  +/-
  +
  Speed (efficiency)      
  -
  +            
  Dependability
  -
  -
  Flexibility
  +
  +
  Cost
  -
  
  Planning
  Short
  Transport Time
  Short
  Short
  Waiting Time (Cheap, but flexibility decreases)
  Long
  Long
  Changeover Time (Costly, machines are idle and people work)
  Short
  Usually short
  Processing time
  Short

• 2 Lean Production

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• The efficient flow is disrupted by

  
  Efficiency is disrupted by unnecessary activities
  -Job shops
  -High setup times
  -Machine disruptions
  -Defect in products rework
  -Individual differences in processing times
  -Unreliable suppliers

• Statical Process Control 

  In manufacturing context, the less consistent and predictive a process is, the more it costs. SPC uses histograms and control charts and will reduce variations and lower the costs.

• Four steps of JIDOKA

  -Discover abnormality
  -STOP
  -Fix the problem immediately
  -Investigate and correct root cause

• 3 Maintenance management

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• Structure of Maintenance types

  
  1.Corrective Maintenance2. Preventive Maintenance 
  
  2.1 Time based maintenance
  2.1.1 Age based maintenance
  2.1.2 Block based maintenance
  
  2.2 Condition based maintenance
  
  2.2.1 Continious monitoring
  2.2.2 Inspections
  
  2.3 Opportunistic Maintenance

• 4 Flows

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• Variability is the root of all evil, 6 types of variability

  
  
  
  
  Processing times, 
  Quality, 
  Customer orders, 
  Production sequence, 
  Setup-times, 
  Maintenance, 

• SMED and setup activities

  Single Minute Exchange of Dies
  
  
  
  
  
  
  
  
   Typical setup activities
  

  •   Getting and returning tools (external)
    
  •   Cleaning the machine (internal)
    
  •   Removing fixtures (internal/external)
    
  •   Adding fixtures (internal/external)
    
  •   Calibrating the machine (internal)
    
  •   Test runs / adjusting  (internal)
    

• SMED steps (4) and advantages

  - Distinguish internal from external activities
  - Convert internal to external activities
  - Improve the setup activities
  - Abolish the setup
  
  advantages
  - lower setup times
  - higher productivity or smaller batch size
  - no dedicated staff
  - scheduling setups not needed
  - try to reduce until it is not relevant anymore

• Pull Production definition and basic principles

  Schedule on the basis of predictions
  
  Pull: authorise based on system status
  
  Basic Principles
  - never run out of stock at any workstation 
  - don't have too much inventory
  - Only scheduling the final stage, the rest is automatic