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The PPA tool is an advanced method for solving complex problems whose causes are of a technical nature.

Introduction

The PPA tool is an advanced method for solving complex problems whose causes are of a technical nature. It is particularly suitable for recurring problems and when there are several causes to the same problem.

Step 1 – Analyze the data and define the scope

The first step will be to rely on the 5W2H to define the problem and the scope of the problem we want to analyze.

Step 2 – List the process points and evaluate the standards

The process points are ultimately the different parts that are in contact with the place of appearance of the defect. For example, we manufacture syrups that we deliver in cartons of 20. We have a problem of depression on the cartons, which sometimes generate a deformation of the cases inside the carton. We will define the following for our example :

Process Point

Point of support between the pusher of the packager and the cardboard

Standard

Speed ahead : 10m/mn

Step 3 – List the systems and subsystems

The challenge is to be able to list all the conditions necessary to ensure the proper functioning of the Process Point. Frequently, to perform the same function, several systems or subsystems can intervene. We will schematize this to bring clarity to the problem.

For example, we will find the following elements :

  • Oil system : set of elements that allow the proper functioning of the hydraulic elements of our equipment. Subsystems can be: piping, valve, piston…
  • Air system : set of elements to ensure the arrival of air in the elements in need (cylinder …). The subsystems can be: filter, pressure controller, seal…
  • Transmission system : set of elements to rotate the equipment. We will find the engine, the chains, the gears, the cams … like subsystems.
  • Electrical system : elements allowing the arrival of the electric energy to the parts in need: electric motor, the box of relay, the detectors … like subsystems.

 

In our case, we have defined the following map :

Step 4 – Evaluate functions and controls needed

For each of the systems and subsystems identified, we will check their correct functioning using the following 5 questions :

    • Goal : What should the system or subsystem do ?
    • Function : What does the component bring to the purpose of the system or subsystem ?
    • Component : What is the list of system components or subsystem ?
    • Principle : How components work together to provide the function ?
    • Standard : What are the conditions for this to work ?

By taking our example, this gives :

Name

Hydraulic cylinder

VHM 48 CTD

Goal

Provide energy to advance the pusher.

Principle

Convert hydraulic pressure into motion.

Function

Convert the 100 bar of oil pressure into one with a feedrate of between 5 and 15 m/min

Component

Seal

Stem

Tip

Tube

Valve

Screw + washer + bolt

Cam

Standard

Output speed of the stem

Adjustment and condition of motion transformation cams

Checking the status of the various components

Step 5 – Detail the controls and operations

Then go into detail and check all the standards we have. We will list each of the criteria and define the standard state in which these elements must be. That’s the point of the tool, it’s often the standards that are not delivered. This step has been reset and defined if necessary.

In our case, the checklist is the following :

Evaluation criteria

Value and Tolerances

What we have

Improvement actions if what we have does not correspond to the standard

Consequence if we can not implement an improvement

Output speed

10 ± 1

14

Change the cylinder

Trace on the cardboard

Cam

45° ± 5

45

Bad thrust that can cause a defect

In the case where we do not have any suggestions for obvious improvements and what we have does not match the standard, then we will conduct an analysis 5 Why to identify the root cause of our problem and see if a solution on a underlying cause could eradicate our problem.

Etape 6 – QM Analysis

To ensure the proper functioning of the criteria that have caused us problems, we will set up or update the QM matrix. We will therefore define :

      • The parameter to control
      • The standard value and its tolerance
      • The means of measurement and the method
      • The control frequency
      • The person in charge of checking.

In our case, we added a control point initially every month, by a maintenance technician. It will come with its output speed meter and will check the standard value. If he does not get it, he will change it. 

Etape 7 – The 5 conditions of 0 defects

Finally, last step, we will apply the 5 questions for the 0 defect vis-à-vis the solution implemented. This will allow us to consolidate the solution and find new alternatives in the event. As a reminder, the 5 questions are :

      1. Are the conditions clear ?
      2. Are the conditions simple to hold ?
      3. Are the conditions variable ?
      4. The variability conditions are easily verifiable ?
      5. Are the conditions easy to restore ?
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