Section 55. Value Stream Map


55. Value Stream Map

Overview

The Value Stream Map (VSM) is a key Lean Sigma tool in any project involving an overly complex process, or a desire to accelerate a process. Value Stream Mapping is used heavily in Lean projects[96] and Kaizens. Here the tool is similar, but there are some subtle differences, primarily in the detail of the map and its look.

[96] A good reference here is Learning To See by Rother and Shook.

VSM in Lean Sigma is similar to the traditional flowcharting approach used in many other Process Improvement initiatives, with three key distinctions:

  • The map is centered around the Primary Entity in the process. For example, if the Primary Entity is an order, then the main horizontal center flow of the map is for the order and what occurs to it.

  • The activities on the map are evaluated for the value they bring to the end Customer.

  • Measures of performance for the process are integrated into the map.

There are two versions of the VSM used in Lean Sigma:

  • High-level VSM sketched out in the Define Phase to begin to understand the process and populated with metrics during the Measure Phase

  • Detailed VSM created in the Measure Phase to get a detailed understanding of the process flow

An example of a high-level VSM is shown in Figure 7.55.1.

Figure 7.55.1. Example high-level Value Stream Map.[97]


[97] Taken from SBTI's Transactional Process Improvement Methodology training material, format adapted from Learning To See by Rother and Shook.

The high-level map contains the major steps in the process, along with process metrics such as Cycle Times, Defect Rates, and Inventory levels. It also shows the control triggers, Suppliers, Inputs, and typically the Outputs and Customers (although not shown in Figure 7.55.1).

The detailed VSM in contrast breaks the process down into each component step as can be seen from Figures 7.55.2 and 7.55.3.

Figure 7.55.2. An example of a detailed Value Stream Map under construction.


Figure 7.55.3. Magnified section of detailed Value Stream Map examining patient flow (prior to adding metrics).


The detailed map shows in microscopic detail exactly what happens to the Primary Entity as it progresses through the process. In Figure 7.55.2, associated procedures and documentation are attached to the VSM for Team reference. The magnified view of another VSM shown in Figure 7.55.3 highlights the difference in terms of value between steps in the process. Steps are either

  • VA

  • Non-Value Added but Required (NVAR) by the business or Required Waste

  • NVA or Pure Waste

Logistics

Construction of both the detailed and high-level VSM is a Team-based activity and absolutely should not be done in isolation by the Belt. Belts sometimes try to partially construct the VSM before a Team meeting to speed up the process, but this typically ends up taking more time and often Team members fail to buy-in to the end result.

Creating the high-level VSM from the P column in the SIPOC can take as little as 30 minutes, the detailed version however requires at least 34 hours of Team time. Sections of the process might have to be validated with other personnel, so they might have to be drawn in at appropriate times too.

The detailed VSM requires at least a 1215 feet length of empty wall space and is typically done on butcher paper. Multiple packs of three-inch square sticky notes are required, preferably in different colors along with different colors of pens.

After completion, the maps are incredibly useful as training tools, and so on, but, for some reason, have a short lifespan (sticky notes tend to fall off, and so on), so transferal to electronic form using Flowcharting Software should be done promptly.

Roadmap

The roadmap to creating a detailed VSM is as follows:

Step 1.

Prepare the workspace as described in the preceding logistics section.

Step 2.

Identify for the process:

  • The Primary Entity

  • Any secondary entities such as orders, information, and charts.

  • The exact starting point(s) of the process

  • The exact ending point(s) of the process

Step 3.

Nominate one person on the Team to be the Primary Entity. They continue to ask, "Okay, what happens to me now?" This sounds a little crazy, but seems to work well. I am jokingly known within one client Team as "Ian the Order" after facilitating a VSM session.

Step 4.

Step through the process, activity by activity just from the Primary Entity's perspective. This usually takes the form of the following:

  • Arrive at site

  • Wait

  • First activity

  • Wait

  • Next activity

  • Wait, and so on

Each activity (including Waits) should be written legibly, one per sticky note and placed on the paper in a stream horizontally down the center (this is the Value Stream; value is added to the Entity as it passes down this path). Some standard symbols are used, as shown in Table 7.55.1, so that anyone in the organization who picks up a map can immediately understand it.

Table 7.55.1. Value Stream Map Symbols and Meanings

Name

Description

Graphic

Start

Draws attention to beginning of the process.

Stop

Draws attention to end of process.

Flag

Shows connection to another page or point on the map; the number denotes where the connection links. It can also represent the input or output points of sub-processes.

Activity

Also known as a Task, Step, or Operation, this represents points in the process where the entity is changed as the result of work being done. The label is typically Verb Noun, for example:

  • Enter Customer Name

  • Add Catalyst

  • Update General Ledger

Metrics are added below the Task to reflect the current levels of

  • Cycle Time (C/T = ??)

  • Quality Rate (Reject = ??, Accuracy = ??)

  • Changeover Time (C/O = ??), and so on

Trigger

Not to be confused with connectors or arrows between process steps, this symbol denotes a trigger from one step to another, generally in electronic form, for example:

  • Signal from surgery to preparation area to request next patient

  • Signal from operations area to warehouse for more materials

Transport

Again, not to be confused with connectors or arrows between process steps, this symbol shows movement of the Primary (or a secondary) Entity and is used when the transport adds additional cycle time to the process or adds risk. The label is typically Item Transported via Mechanism, for example:

  • Send Quote via Mail

  • Send Patient via Wheelchair

Decision

Identifies where a decision creates a branch in the process flow. The symbol label is the question itself, for example:

  • Are all fields complete?

  • Does the product meet specification?

Each decision symbol can contain only one question. The decision should have two or more exit lines, each labeled with an answer to the question, for example:

  • Yes

  • No

Decisions start two or more mutually exclusive paths, but a single entity can only take one of the paths. The entity proceeds through path "A" or path "B," not both

When a decision and, thus, a branch occurs during mapping, to reduce confusion it is best to follow and map one path to its conclusion before returning to the split and mapping the second path, and so on.

Store

Identifies a point at which an entity (or its parts) is physically stored. The entity is usually conveyed or placed in some sort of storage waiting for a trigger to release it. A store is not just a queue. The label is Store Item at Location, for example:

  • Store Hamburgers in Warmer. Burgers are made ahead of time waiting for the trigger of an order placed.

  • Store Parcels in Express Pickup Box. Mail waits in a box or on a shelf for pickup, the trigger being the arrival of the courier, for example.

Wait / Delay

Indicates that time is being consumed in the process by

  • A scheduled or planned delay

  • An activity or decision in another process

The label is Wait for Noun Verb, for example:

  • Wait for Management Approval

  • Wait for Customer Review

Parallel Processing, Split and Join

Parallel processing occurs when two or more activities in a single process can be performed at the same time, thus reducing the overall time required to complete the process.

Prerequisites for parallel processing:

  • Path "A" tasks must be independent of Path "B" tasks

  • A separate resource is available for each path

The activity at which a parallel process is initiated is called a Split, at which point the entity is "cloned." Each of the clones then proceeds through different paths, for example, Order Faxed to Warehouse. This creates a cloned copy of the Order, one at the point of faxing, the other in the warehouse.

The activity at which a parallel process is terminated is called a Join, at which point the pieces of an individual entity are recombined to form a new "whole" entity. Each piece brings with it the results of the activities through which it passed.

Loop

Entities normally flow to the next activity in the sequence. Typically initiated by a decision, a Loop is the flow structure at which an entity flows backward to a previous activity. An example might be "Is the Entity Accurate?" If not, then the entity has to be reworked in some way.


Step 5.

Return to the start point of the process and map the path of the Secondary Entities in the process. These are not resources, such as staff, but objects, information, and so on, that supports the Primary Entity as it flows through the process.

Step 6.

Return to the start point of the process, and, discussing each step in turn, determine if the steps are

  • Value Added. Place a green dot on the sticky note. VA activities are those that

    • Change the size, shape, fit, form, or function of material or information (for the first time) to meet customer demands and requirements.

    • Or (specific to healthcare) contribute to a change in, or maintenance of a Patient's health status to meet customer (Patient/Physician) demands and requirements.

  • Non-Value Added but Required. Place a blue dot on the sticky note. These activities do not bring value to the Customer, but are needed for some reason by the business or for legal or regulatory reasons. They could in theory be designed out if some process changes were made. Examples might include

    • Entering data into a system

    • Performing a quality check

  • Non-Value Added (Pure Waste). Place a red dot on the sticky note. These are the activities in the process that are not required by anyone and would best be removed completely. There is often contention here, because people do not like to find out that a large portion of their work brings no value. It is important for Belts to really challenge the Team on each activity. After they get the hang of it and they understand that no one is casting aspersions on their abilities, there is typically at least one Team member that jumps in with gusto and puts the appropriate dots on the sticky notes. Examples of NVA activities include (some of these could arguably be required by the business, but challenge them anyway)

    • Waiting

    • Reworking entities

    • Scrapping entities

    • Transporting entities

    • Motion

    • Load/Unload

    • Secondary inspections

    • Storing

Step 7.

Validate the basic VSM with other stakeholders in the process to ensure nothing is missing and the map is representative of the current process. Often disagreements arise; try to see these as opportunitiesif people are doing the process differently, then that can lead only to an improvement if methods are aligned to be the best.

Step 8.

Populate the steps in the VSM with process performance data. This might include

  • Takt Times

  • Process Lead Time

  • Cycle Times

  • Changeover Times

  • % Overall Equipment Effectiveness

    • % Uptime

    • % Quality

    • % Pace

  • Shift hours

For the process as a whole a Delay Ratio can be calculated as


For more detail on the Process Lead Time, see "TimeProcess Lead Time" in this chapter. The standard Lean definition of Processing Time is all of the time in the process (whether it is VA, NVAR, or NVA) along the value stream (i.e., just related to the Primary Entity) minus the Waits. A preferable tweak to this is to consider the VA activity Processing Time for the Primary Entity, which gives a truer indication of the fat in the process:


An impossibly perfect Lean process would have a Value Ratio of 1.0. Most processes run closer to 100.

Interpreting the Output

The VSM is a key tool to identify unnecessary waste and risk in the process as follows:

  • NVA activities should be the first target of any project Team. A few of them are Quick Hits and require little to no resource to remove. Others might take some reorganization of the process to remove. NVAR activities can also be a targetsome can be removed quite quickly with a change of procedure or policy. Challenging a business, regulatory, or legal "requirement" often identifies that there is no requirement.

  • Multiple Start points in a process can be a problem if the streams aren't quickly merged, or there are inconsistencies between streams. Seek to merge the multiple Starts into a single main stream as quickly as possible.

  • Multiple Stop points in a process always seem to create problems, usually because there is no way to reconcile the end points. Seek to bring streams back together before the end of the process, or preferably don't have them separate in the first place.

  • Improvement to Decisions is an obvious quick win in most projects. Decisions initiate branches and loops; thus, incorrect decisions initiate incorrect or unnecessary branches or loops. Each Decision should have the following elements:

    • A clearly articulated and VA Purpose

    • An accountable Decision Maker

    • Inputs necessary to make the decision, usually information and an entity

    • Criteria by which to make the decision

    • Alternative paths for the entity to take (clearly related back to the criteria)

    • An appropriate amount of Time to make the decision

  • Parallel Processing seems at first glance to be a wonderful thing to do in any process. In reality the splitting or cloning of an entity brings its own problems, because as soon as any work is done on either clone, they are no longer clones, just parallel entities unless work is done to reconcile them. This reconciliation can be a huge undertaking and is often a major source of defects. Also, if the work content in the two paths is not balanced, then one clone ends up waiting at the join for another clone(s) to arrive.

  • Loops always cause an increase in the amount of time required to complete the process and often disrupt the processing of other entities in the system. Consider focusing on reducing the number of entities going through the loop as a key part of any project.

  • Triggers that allow the entity to move from step to step in the process are fertile ground for opportunities. Often an entity gets stalled at the sender when

    • The recipient doesn't know it is ready at the sender

    • The sender doesn't know that the entity is ready to send

    • The sender doesn't know that the recipient is ready to receive




Lean Sigma(c) A Practitionaer's Guide
Lean Sigma: A Practitioners Guide
ISBN: 0132390787
EAN: 2147483647
Year: 2006
Pages: 138

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