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The Lean process analysis will reveal flow process problems. Lean techniques can be used to analyze flow at a total process (macro) level or a process step (micro) level.

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Quick reference

Lean Flow Analysis

The Lean process analysis will reveal flow process flow problems. Lean techniques can be used to analyze flow at both a total process (macro) level or at a process step (micro) level.

When to use

This analysis is normally done during the Analyze phase. By that time the value stream map is complete including the data in the data boxes.

Instructions

Lean flow analysis focuses on identifying those areas of the process that create flow problems such as bottlenecks or flow constraints. There are both visual and numerical analyses that can be used.

Cycle Time Map

The cycle time map shows on a linear time scale where the process is spending value-added time and where it is not. The map often further refines that analysis but adding organizational swim lanes or swim lanes for major workstations. This visual analysis technique highlights the areas of non-value-added time that are often overlooked. If total cycle time reduction is a goal for the project, it is often much easier to reduce the non-value-added time than it is to change the value-added time.

Tangled Flow

Another visual analysis approach is to look for tangled flow. If the map that was created was a process map that showed all the branches and loops, the tangled flow is immediately obvious. If a value stream map is created, the value stream will always be a straight line with no tangled flow showing. However, in this case, the indications of tangled flow can be seen by the effect that it is having on the data box values. At the point of constraint, there will often be large quantities of WIP inventory, large delays, and poor yield. Another effect that creates tangles is when item information becomes separated from the item during the process. Syncing those together again often creates a bottleneck.

TAKT

TAKT is the pulse rate of the process if it is well-designed. In an ideal process, each step is completed within the allowed TAKT time and every item moves to the next step at the same time. This simplifies scheduling and can quickly identify when there is a quality issue or other performance problem because something doesn’t move when it should. The TAKT time can be calculated by dividing the amount of time available for process work during a week by the number of items required from customer demand during a week. The resulting number is the TAKT time for each workstation.

Hints & tips

  • Visual analysis tools are easier for operators and stakeholders to understand; so use them when appropriate.
  • A value stream map is very useful when working with a process that regularly produces similar items. However, a process map is often better for the unusual process because it shows the tangled flow.
  • If a step is longer than TAKT and can’t be shortened because of the nature of the work at that step, then the resources to do the work at that step must be increased, so that they are working multiple units in parallel. I still run with TAKT, but now I have every other resource moving their item at the pulse point.
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  • 00:05 Hi, I'm Ray Sheen,
  • 00:07 we've been focusing on some of the quality problem-solving analysis.
  • 00:11 Well now, I want to shift gears to the Lean analysis, and
  • 00:13 we'll start by looking at Lean flow.
  • 00:15 I'll start with an analysis at the total process perspective and
  • 00:21 end at the step level.
  • 00:23 So let's take a look at total process flow.
  • 00:26 In the measure stage, we talked about measuring total time and
  • 00:29 measuring value added time.
  • 00:31 I even talked about calculating the ratio of value added time over total time.
  • 00:35 Now we want to analyze all of that to find problems.
  • 00:38 In my opinion, the best tool for that is the cycle time map.
  • 00:42 On this map, we create swim lanes for organizations or major work cells.
  • 00:47 The horizontal axis is the timeline with a duration of process start to process
  • 00:52 finish.
  • 00:53 Then within each lane we show a bar for each step.
  • 00:56 The length of the bar is the amount of value added time at that step.
  • 01:00 If there is no value added time, the length of that bar is therefore zero.
  • 01:05 Between each of the step bars,
  • 01:06 we have a bar that is the length of the non-value added time.
  • 01:10 I find it easier to read this map if I make the colors of the bars for
  • 01:14 value added time different from the color for non-value added time.
  • 01:18 Of course, you can get the value-added time and
  • 01:20 non-value-added time from the data box or time ladder on your value stream map.
  • 01:26 Make certain when drawing this map that you're using times based upon
  • 01:30 a full 24-hour clock and 7-day workweek.
  • 01:33 This is what the customer feels, so that is what we want to use.
  • 01:37 We talked about that back when we discussed the measurements in
  • 01:40 a previous module.
  • 01:41 Now you can focus your analysis and identify improvement opportunities in
  • 01:46 the areas where there are large blocks of non-value added time.
  • 01:49 I've often found when discussing how Lean analysis can reduce the amount of
  • 01:53 time in a process.
  • 01:54 But there is resistance,
  • 01:56 people saying that they already are working as fast as they can.
  • 02:00 Then we collect the data and draw the cycle time map.
  • 02:03 I explained that I'm not trying to remove any time from the value added activities.
  • 02:08 In fact, we often even add time to those activities to improve the quality who
  • 02:11 would want to find and reduce or the non-value added activities.
  • 02:15 And this map shows that there are some big chunks of that time buried in the process.
  • 02:20 The next thing to analyze in your value stream map or process map is looking for
  • 02:24 tangled flow.
  • 02:26 The value stream map should only show the straight line flow of the process leading
  • 02:30 to the customer.
  • 02:31 If you're using a process map, you may be showing lots of branches and loops and
  • 02:36 a value stream map is ignored, because they don't represent first past successful
  • 02:40 yield of that step moving towards the customer.
  • 02:44 One of the best ways to find tangled flow is to look for
  • 02:46 areas in the process where the items are getting slowed down and stacked up.
  • 02:50 There's a bottleneck at that point which is constraining the flow.
  • 02:54 Investigate the constraint or bottleneck,
  • 02:56 determine what can be done to allow the majority of the process items to continue
  • 03:00 to flow smoothly through that point.
  • 03:02 Another thing that will slow process down is that there are decisions that must
  • 03:06 be made in the process by individuals who are not the primary process operators.
  • 03:11 These decisions will slow the process and create bottlenecks.
  • 03:14 That is because the item must wait until the decision maker has time to do their
  • 03:18 review and analysis and made a decision.
  • 03:21 All of that is non-value-added time.
  • 03:23 In addition, there's the likelihood that the decision maker will sometimes
  • 03:28 make the wrong decision and reject a good item or
  • 03:30 send an inaccurate item to the next step.
  • 03:33 As much as possible, we want to remove these external decisions and
  • 03:37 design the process and train the operators so that they know
  • 03:40 they have a good process item and can move it on without any external reviews.
  • 03:44 A final thing to watch for in the flow is when information about a process item gets
  • 03:49 separated from the item itself.
  • 03:51 This may be paper records or electronic records, but
  • 03:54 they start to follow a different flow for a portion of the process,
  • 03:58 and then they must sync back up and get reconnected.
  • 04:01 Inevitably, one of the flows the item or
  • 04:03 the information goes faster than the other, and
  • 04:06 then we have something in the process waiting for the other one to catch up.
  • 04:11 Not to mention that sometimes an item or information is lost or rejected while
  • 04:16 separated, or the items or information changed sequencing in one of the flows.
  • 04:20 Now, the rethinking of data and items becomes difficult,
  • 04:24 causing further delays and confusion.
  • 04:27 Try to avoid separating the item and
  • 04:29 information about the data item until the end of the value stream map.
  • 04:33 The final analysis for this module is the analysis of the flow at the step level.
  • 04:38 In a well-designed Lean process,
  • 04:40 every item moves to the next step in the process at the same time.
  • 04:44 The process takes on a pulse rate or
  • 04:46 a cadence of everything moving one position forward.
  • 04:50 This cadence is called the TAKT time, from a German word for
  • 04:53 an orchestra conductor baton that taps out the beat for the orchestra.
  • 04:58 For this to work, each step must be designed so
  • 05:00 that it can be completed within the TAKT time interval for the process.
  • 05:05 The great thing about using this approach is that, the problems in
  • 05:08 the process are immediately visible, the item did not move.
  • 05:13 Now, when you are initially analyzing the process, if you find
  • 05:16 steps that are longer than the TAKT time, those will require additional resources,
  • 05:21 often placed in parallel in order to keep up with the rest of the process.
  • 05:25 And this step will hide problems.
  • 05:27 This is because we don't expect the item to move at the same speed as
  • 05:31 everything else when it is in that step, so
  • 05:33 we don't recognize a problem when it first occurs within that step.
  • 05:37 It's only when the delay becomes a problem becomes excessive that we finally realize
  • 05:40 what is happening.
  • 05:42 I've also seen a poorly designed process slow all the other steps to wait for
  • 05:46 the process step that has the longest time and treat that as the TAKT.
  • 05:50 This leads to missed deliveries and angry customers and stakeholders.
  • 05:55 To calculate the TAKT time is quite easy.
  • 05:58 It is a number of work hours for that process in a week or a day
  • 06:01 divided by the demand for completed units through that process in a week or a day.
  • 06:06 So for example, if we have a 40 hour work week, we have 2400 work minutes.
  • 06:12 If we need to ship 200 units in a week,
  • 06:15 then we need to complete a unit every 12 minutes, that is the TAKT time.
  • 06:20 The work at every workstation should be analyzed to see if it can complete in 12
  • 06:24 minutes and the unit can be moved at the process pulse rate the TAKT time.
  • 06:30 Lean analysis is normally focused on flow analysis,
  • 06:34 the cycle time map, TAKT time and even a view looking for
  • 06:39 tangled flow are the tools to conduct your Lean flow analysis.

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