Essential Quality Tools for Process Improvement

Posted on Dec 9, 2024 in Other subjects

Quality Tools

Poka-Yoke

Poka-Yoke can be translated as “error-proofing” or “fail-safe.” These techniques aim to prevent human error, especially in manufacturing processes, helping to achieve zero defects and eliminate many quality inspections. The underlying philosophy is that if nothing else, there is always the possibility it will work correctly. There are different types:

  • Control or blocking: Prevents a defect or locks the machine.
  • Informational and warning: Reports or alerts in the presence of a defect.

Commonly used techniques and devices include non-symmetrical parts, sensors or limit switches, mechanical stops, templates, and warning lights.

Brainstorming

Brainstorming is a group technique for obtaining a multitude of ideas about a given topic. The rules that should be followed are:

  • Small groups of 3 to 8 people.
  • Everyone must understand the problem to be solved.
  • Freedom of expression without fear of ridicule, respecting the right to speak.
  • No idea should be criticized; all should be noted.
  • There must be a moderator.
  • Build upon the ideas of others.
  • No evaluation until the end.

Given these rules, the phases to apply this technique are:

  1. Definition of the problem: Everyone should understand it clearly. The objective can be to find the causes of the problem or to find solutions.
  2. Exposition of ideas: Interventions are made in rounds, and if someone has no ideas, they pass their turn. The facilitator writes down all ideas.
  3. Selection of the best ideas. A model of the minutes for each brainstorming session should be created.

Histograms

Histograms serve to interpret data visually. They represent the frequency distribution of a variable grouped into classes.

The number of classes (K) is determined by the number of data:

  • Below 50: 5-7 classes
  • 50 to 100: 6-10 classes
  • 100 to 200: 7-12 classes

The class interval (width of the rectangle H) should be rounded to manageable values.

Example: Make a histogram with the following data:

351.7, 355.3, 360.7, 357.6, 349, 351, 355.1, 357.4, 353.5, 349, 351, 353, 356, 355.6, 350.9, 353.6, 353, 355, 359.4, 352.2, 356.1, 355, 357, 358.9, 353.2, 357.3, 359.1, 357, 359, 361

K = 5-7 (since there are fewer than 50 data points)

Range = 360.7 – 349 = 11.7

H = Range / K = 11.7 / 6 = 1.95 ≈ 2 (rounded to a manageable value)

Cause and Effect Diagram

Also known as a Fishbone or Ishikawa Diagram, or 6M. It is a graphic representation of the logical relationships between causes that produce a defined effect. It allows you to highlight and classify families and prioritize the causes of a certain effect. This technique can be combined with other quality tools such as brainstorming. It is represented as follows:

This diagram helps solve problems in the absence of quantifiable data. The steps to follow are:

  1. Select the effect: The feature to be improved or the problem to be solved.
  2. List of causes: Brainstorming can be used.
  3. Classify families: In productive processes, the 6Ms are frequently used: Material, Labor, Environment, Methods, Machines, and Maintenance.
  4. Trace the outline of the chain of causes for each family: If necessary, respond to questions such as where, why, and when. The most likely causes may have to be selected in order to put them into practice and check their effectiveness.

5S

5S is a quality practice for maintaining the working environment. Its name comes from Japanese:

  • Seiri (Classification)
  • Seiton (Organization)
  • Seiso (Cleaning)
  • Seiketsu (Hygiene)
  • Shitsuke (Discipline and Commitment)

It is a practice originating in Japan but now applied worldwide, given its strong results due to its simplicity and effectiveness.

1. Classification and Discard

Having just enough and the right amount. Separate the things that are necessary for our work from those that are not, and keep only the necessary items in the appropriate place and in the adequate number.

To implement the first S, we ask the following questions:

  • What can we discard?
  • What do we have to keep?
  • What needs to be repaired?
  • What can be sold?
  • What can be useful for another person or department?

2. Organization

A place for everything and everything in its place. Everything must have a unique and exclusive place where it can be found before use and returned to after use. Study where things should be placed, thinking about the people who have to use them and the frequency of use.

For the second S, we can ask:

  • Can we reduce the stock?
  • Should this be close at hand?
  • Do we all call the device the same way?
  • What is the best place for everything?

3. Cleaning

Workers deserve the best and cleanest environment. Cleaning must be done by everyone. Each worker should have an area designated as their area of responsibility that needs to be kept clean.

For the third S, we can ask:

  • How do you think it can be kept clean at all times?
  • What tools, time, and resources do you need?
  • Can your workplace be considered clean?
  • What do you think would improve with more cleaning?

4. Hygiene and Display

Hygiene is the maintenance of cleanliness and order. The display emphasizes the ongoing management of hygiene. Visual management involves a responsible group making periodic visits throughout the company, detecting areas for improvement, and notifying the person in charge of the 5S in that area. Color management involves the same group placing red stickers or cards where improvements are needed and green cards where particular care is taken.

Questions for the fourth S:

  • What types of notices or warning signs do you think are needed in your workplace?

5. Commitment and Discipline

Order, routine, and advancement. This ensures that improvement becomes a routine, another part of the job. 5S is the best example of continuous improvement.

Question:

  • Explain the reasons why you think you can commit to this system.