Determining Schedule Signal Logistics

Determining Schedule Signal Logistics

Once you have selected the scheduling signal, you need to determine the signal and material logistics. You, and your team, need to determine how material and the kanban signal will move from the production process to downstream customers. You will also need to determine how the signal will make it back to the production process.

If you have not already done so then this is the perfect time to take a fieldtrip to the production process. During this fieldtrip, walk the path of the materials. Start at the production process and follow the same path the material takes to its customer. Look for stops, staging problems, and convenient ways to move the signals. Take this opportunity to determine the who, what, and when of the process. As Figure 5-17 shows, you must create a continuous loop of material and signals flowing from the production process to the customer and back again.

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Figure 5-17: The Kanban Design Must Create a Continuous Flow of Materials and Signals.

One of the first logistic decisions will be how the material will be staged or whether you need to change how you currently stage your production material. Consider how the layout facilitates maintenance of the kanban cycle when making the staging decision. Also, do you want to keep the material in one spot or dispersed to the customer cells ? Consider how your organization manages material storage and stage the material where the highest kanban discipline will be maintained .

Consider the logistics of how the material moves into and out of the staging area. Look at the rotation issues and the ability to maintain order in the staging area.

When you have made the staging decision, make a drawing of the final layout. The drawing does not need to be fancy ”use a CAD drawing, MS Excel, or just a simple pencil drawing. The drawing helps to explain the flow and can serve as a training aid later. Figure 5-18 shows an example flow diagram drawn with MS Excel.

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Figure 5-18: Kanban Flow Diagram.

As part of the design, you and your team will also need to decide where the scheduling signal will be located. When making this decision, remember the intent of the signal is to provide information for the production operators to make scheduling decisions. With this in mind, locate the scheduling signal as close to the operation as possible and in a very visible position. At the same time, position the scheduling signal so that you "pull" material through the production process instead of "pushing" it.

Make sure the signal location is also convenient to keep updated as production occurs. For kanban cards signal, locate the card post forward of the material storage area. This step will help in keeping the signal updated.

Develop Rules for the Kanban

Once the team has selected a kanban signal, it's time to develop the rules that govern its operation. The rule should address:

  • The part numbers covered by the kanban

  • How the design works ”how the cards, magnets, etc., move

  • The meaning of the scheduling signals and how to interpret them

  • Any scheduling rules of thumb (if required)

  • The preferred production sequence (if one exists)

  • Who to go to and what the "helpers" should do when contacted

  • Any special quality or documentation requirements

Remember, you are drafting the rules to communicate how to run the kanban and to allow the process operators to schedule the line. The only way the production operators can take over scheduling the line is by the rules providing clear direction and scheduling guidance.

The rules should be specific and designed to make sense for your operation and the process. The rules should assign responsibilities by function (avoiding names ) and should not allow buck-passing of responsibility. Finally, never forget this basic thought when developing the kanban rules: If you want something to happen in a certain way, it better be spelled out in the kanban rules!

When you discuss how the pieces of the kanban will be manipulated, be specific:

  • If this happens, then do this.

  • The kanban card will be placed in _____ when ______ occurs.

  • Move the magnet to the _____ when this occurs.

  • When _____ happens, call ____ at ext. _____.

  • Complete this form and fax to _____.

Once again, if you want the signals to move in a specific way, then you must tell everyone. Also, don't forget to tell everyone who, how, and when the scheduling signals (kanban cards, containers, faxbans) get back to the production process.

When you draft the scheduling rules make them easy and unambiguous to follow. Think through possible misconceptions and correct them so they will not occur. Spell out what signals a normal changeover. Spell out what signals an emergency changeover. Seek feedback to make sure that everyone else is as clear about how to interpret the signals as you and your team.

Additionally, the scheduling rules should contain clear-cut decision rules. The decision rules should help the production operators make consistent production scheduling decisions based on the stated priorities. The rules should provide rate information, if applicable , to allow the operator to develop production expectations. The decision rules should contain instructions on when and whom to call for help. Also, the rules should include all the "everyone knows this" items that everyone seems to forget from time to time. If you want the operators to schedule the line based on demand, then you have to give them the tools to do it.

If a preferred scheduling sequence exists, then list the preferred sequence in the rules. When developing a preferred sequence, specify the sequence in terms of normal operations. Potential items that can drive preferred sequences might include changing between paint colors, common raw materials, or common operational equipment. Whatever it might be, if you use these factors to schedule the line today, then include them in the rules by defining a preferred operating sequence. Also, make it clear that the schedule will deviate from the preferred sequence when red signals appear.

The rules should clearly state what the operators do when they get a red signal. The red signal is meant as a danger warning. Many people think red means hit the emergency stops and immediately change over. However, red means that a stock out will occur and action needs to be taken as soon as possible. Set the red levels at a point where you have time to react , not just to watch the kanban crash and burn.

Finally, use the kanban rules to develop a scheduling system that does not allow backsliding. Don't allow hidden forecast or MRP systems to really control the kanban. Make the production operators and the production managers use the scheduling signals to determine the schedule position and make decisions. Later, if you discover backsliding, figure out what is happening and make the necessary changes. Figure 5-19 shows a draft set of rules for the ten-part number example from Chapters 3 and 4.

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  1. Empty containers will serve as the signals for Scheduling Line 1.

  2. Scheduling rules:

    • Fill all the containers with the same profile before switching to the next profile unless a red signal occurs.

    • Look at the control point for empty buggies to determine the next item to be produced. Select the next profile that has exposed the yellow blocks.

    • If more than one profile is in the yellow zone (and no red signals exists), then run profiles (with containers in the yellow zone) in this sequence:

      1. 3502

      2. 3505

      3. 3508

      4. 3509

      5. 3511

      6. 3503

      7. 3504

      8. 3506

      9. 3507

      10. 3510

    • If a red signal occurs, then notify a supervisor and begin making plans to change over to this profile.

      • The supervisor should confirm this is a valid red signal before changing over.

    • When no yellow (or run) signals exist, then notify the supervisor and prepare to shut down the line.

  3. Movement of containers. The attached drawing shows them flow of containers for this kanban. (Reference Figure 5-15)

    • Line A technicians will move containers from Line A to the product storage area.

    • Work center operators will return the empty containers to the empty container storage area.

  4. If you receive rejected material, then contact your supervisor immediately. All rejected material will be treated as consumed product until released from quality hold.

  5. If you have any questions regarding these rules, then see your supervisor or the materials scheduler.

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Figure 5-19: Kanban Rules for the Ten-Part Number Example from Chapters 3 and 4.