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One of the best techniques for controlling a process to perform in a particular manner is to prevent it from performing in any other manner. There are methodologies that can be used to create prevention of process problems: Poke Yoke and Five S Disciplines.

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Quick reference

Prevention as Control

One of the best techniques for controlling a process to perform in a particular manner is to prevent it from performing in any other manner. There are methodologies that can be used to create prevention of process problems, Poky Yoke and Five S Disciplines.

When to use

When designing a solution in the Improve phase, Poka Yoke and Five S Disciplines should be considered. However, both are as much about a mindset change as a product or process design change; so they need to be trained and reinforced in the Control phase until they become part of the culture.

Instructions

Lean Six Sigma is inherently a corrective action methodology because it seeks to solve an existing problem. However, the solution can and should include elements of preventive action that would act as a barrier against future problems. There are two methodologies that are preventive action enablers and both can be used in the design and implementation of the Lean Six Sigma solution.

Poka Yoke

Poka Yoke means mistake proofing or error proofing. It consists of elements of a product or process design that either prevent a mistake from occurring or make the mistake immediately obvious to the operator or user so that they fix it before they continue with the process or use the product. Poka Yoke is a principle-based methodology, so there are no formulas or statistics. The five Poka Yoke principles are:

  • Part Characteristics – An attribute of the part, such as size, shape, or color, is used to direct the operator or user. Example: Square peg cannot go in a round hole.
  • Error Detection Sensors – Added detection sensor or inspection step that warns the operator or user that an error has just occurred. Example: A continuity check for a wiring step to make sure all the wires are connected.
  • Equipment and Tooling Positioning – The design of tooling, equipment or fixtures so that it assembles correctly and guides the work piece to the proper location. Whereas the part characteristic principle involved part redesign, this principle does not redesign the part but rather redesigns what handles the part. Example: Equipment for fabricating items will not start if there is no raw material on the work surface.
  • Counters – An attribute of the process or product is counted to ensure that it is operating correctly. Example: A timer counts the minutes for a drying operation before the work piece can move to the next step.
  • Template and Checklists – A template or checklist is used to guide the operator or user on what to do next. Example: A setup and installation guide accompanying a new computer.

Five “S” Disciplines

The Five “S” Disciplines are a workplace organization methodology. By cleaning and organizing the workplace, the chance to introduce special cause errors into the process is reduced and it is easier to see when a process problem is occurring. When the disciplines have been fully implemented, they become a mindset and culture for the organization. These Five "S" disciplines should be followed in the order shown.

  1. Sort (Seiri) – Sort all the items found in the workplace and group them by use. If not required in the workplace, return them to the appropriate location.
  2. Set in Order (Seitton) – Organize the remaining items to put them in logical order as they are used. Design the workstation for efficiency. This is sometimes called Straighten.
  3. Shine (Seiso) – Clean and maintain the workplace and all equipment. This minimizes breakdowns and contamination of work items.
  4. Standardize (Seiketsu) – Create standard procedures and standard operations where appropriate. Standardize the workstation for tools, parts, and equipment storage so that the operator always knows where to find and store everything.
  5. Sustain (Shitsuke) – Once the first four disciplines are in place, perform periodic audits and training to maintain the disciplines.

Hints & tips

  • Work with the process operators to get their insight on the most difficult steps. These should be the first candidates for Poka Yoke.
  • The Templates and Checklists principle works best for occasional processes. Operators have a tendency to get “numb” to checklists on routine items, so avoid this approach for frequent routine processes.
  • When implementing Five S, ensure that you include the operators in the discussion and the activity, so that it does not appear to be used as a disciplinary process against them.
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  • 00:05 Hi, I'm Ray Sheen.
  • 00:06 One of the best ways to control problems is to prevent them from ever occurring.
  • 00:11 Part of good process control is problem prevention.
  • 00:15 Let's look at some tools to help with this.
  • 00:18 You've probably heard the old saying that an ounce
  • 00:22 of prevention is worth a pound of cure.
  • 00:24 Well, that's what we're talking about right now, the prevention.
  • 00:28 Just to be clear, corrective actions are correcting existing defects or problems.
  • 00:33 The process has already failed.
  • 00:36 Preventive actions are taken before a failure occurs, and
  • 00:39 act as a barrier to prevent the possibilities of a problem or a defect.
  • 00:44 Generally speaking, a Lean Six Sigma project is a corrective action.
  • 00:48 The business has identified a problem that it wants the team to fix.
  • 00:52 So our process improvement activities have been focused on finding the root cause or
  • 00:57 causes and eliminating or controlling them.
  • 00:59 But in our control plan, we can and should provide preventive actions so
  • 01:04 that the problem or similar ones do not impact the process in the future.
  • 01:09 In that way, we can sustain the process improvement.
  • 01:12 There are two excellent methodologies that we can use to do this.
  • 01:16 They both originated in Japan, Poka Yoke and 5S.
  • 01:20 I'll start with a discussion of Poka Yoke, which is the Japanese term for
  • 01:25 mistake-proofing or error-proofing.
  • 01:27 Poka Yoke acknowledges that people make mistakes.
  • 01:30 You're having a bad hair day, or you're distracted, maybe you're tired, or
  • 01:35 you misunderstand the situation.
  • 01:37 Whatever the case, we make mistakes.
  • 01:40 Poka Yoke principles attempt to insulate the process from these mistakes.
  • 01:44 They do this by either making it impossible to actually make the mistake,
  • 01:49 you can't put the square peg into the round hole even if you try.
  • 01:53 Or they make the mistake so obvious that it is immediately recognized by
  • 01:57 the operator and fixed before the process continues.
  • 02:00 The alarm or buzzer goes off when the barcode machine scans the wrong part for
  • 02:05 the assembly.
  • 02:06 Now there are five Poka Yoke principles.
  • 02:08 These are not an analytical methodology.
  • 02:11 There are no equations or statistics.
  • 02:13 Rather, the team considers each of these principles and
  • 02:17 asks themselves if they can apply them in a way to prevent mistakes.
  • 02:21 The first principle is part characteristics,
  • 02:23 back to the square peg in the round hole.
  • 02:26 But you can also use characteristics such as size, color, and weight.
  • 02:30 Next is error detection sensors.
  • 02:32 This is when an automated device identifies that something was done wrong.
  • 02:37 Like you're entering data in on a web page,
  • 02:39 and you get a message saying that you haven't completed one of the fields.
  • 02:43 Third is the equipment positioning.
  • 02:45 This is one of the most popular approaches used
  • 02:47 with Lean Six Sigma manufacturing projects.
  • 02:50 New tooling or gauging is designed that guides the parts into the proper position
  • 02:55 ensures that the steps are completed in the proper sequence.
  • 02:58 The item being produced does not change.
  • 03:00 Rather, it is the support equipment around that that changes.
  • 03:04 Fourth is often the easiest to implement.
  • 03:07 It is account of a process parameter that can indicate when something unusual is
  • 03:11 happening.
  • 03:12 One of the most common is to put a timer that counts seconds or minutes for a step.
  • 03:17 If the step takes too long,
  • 03:19 a warning signal is sent to say that an investigation should be started.
  • 03:24 The last one is checklists and templates.
  • 03:26 These are very good ways of reminding people to do things and
  • 03:29 to give them the order that they should do them.
  • 03:32 One caution though, with templates and checklists,
  • 03:35 they work best for occasional steps or occasional processes.
  • 03:38 People who use these on a routine basis have a tendency to get numb to
  • 03:43 the checklist or template.
  • 03:45 Now let's look at 5S.
  • 03:47 I briefly mentioned this in an earlier session.
  • 03:49 I'd like to go into a little more detail now.
  • 03:51 The 5S disciplines are workplace organization methodology.
  • 03:55 They may not directly impact process design, but
  • 03:58 they indirectly impact performance by providing an orderly workplace that is
  • 04:03 less likely to be introducing special cause variation.
  • 04:07 That's why these disciplines lead to increased efficiency and effectiveness.
  • 04:11 There are fewer mistakes made when the 5Ss have been deployed.
  • 04:16 Experience has shown many of the common process errors are eliminated because
  • 04:20 of distractions and uncertainty in the workplace have been eliminated.
  • 04:24 Let's look at each of the 5S disciplines.
  • 04:26 They are named with Japanese words that start with an S sound and
  • 04:30 have been translated into English words that start with the letter S.
  • 04:34 And with the 5S disciplines,
  • 04:36 there is a definite order in which you should be applying these to a workplace.
  • 04:40 First is sort.
  • 04:41 This just means to sort through everything at the workplace and
  • 04:45 to organize it into the appropriate piles or stacks.
  • 04:47 This reduces the likelihood that the wrong form or the wrong item is used.
  • 04:52 Next is to set an order.
  • 04:54 Think of this as putting things in the correct order that they will be used.
  • 04:58 This can reduce the amount of movement and simplifies the flow.
  • 05:02 It's obvious what should be done next because it's the next thing in the line.
  • 05:06 Third is shine.
  • 05:08 This means to clean and maintain all the equipment.
  • 05:11 By doing this, the likelihood of an unexpected breakdown or
  • 05:15 failure is reduced, which reduces the chance of special cause variation.
  • 05:19 Fourth is to standardize.
  • 05:21 The first three disciplines often did not require any process redesign or
  • 05:25 additional costs.
  • 05:26 This step may.
  • 05:28 In this case, we create a standardized place for all tools and equipment.
  • 05:32 We standardize on how similar steps are done.
  • 05:35 We are removing variation, which will lead to fewer defects and less waste.
  • 05:40 And then finally, there is the discipline of sustain.
  • 05:44 Once these other disciplines are in place, they're continually practiced.
  • 05:48 The disciplines are audited, they are included as part of the standard operating
  • 05:52 procedures and incorporated into operator training.
  • 05:55 Ultimately, they become part of the culture of the organization.
  • 06:00 Poka Yoke and 5S are two good methodologies for
  • 06:04 preventing problems from occurring.
  • 06:07 While some of the principles will be built into your solution,
  • 06:11 they can also be a mindset for how to manage an ongoing process.

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