6 Guidelines for Moving Toward a Lean Value Stream

Though, by definition, it’s impossible to achieve a lean value stream — because lean thinking and practice aim for perfection, a goal with a constantly shifting future state — value-stream mapping can keep you on the path of continuous improvement. Specifically, the mapping process and resulting map help identify and eliminate waste in any value stream because every lean value stream features common characteristics. So, whether your organization is in the manufacturing, construction, food service, or another industry, or you oversee administrative functions such as accounting and finance, HR, and IT, the following guidelines ensure you continuously improve your value stream.

1. Produce to your takt time

“Takt time” is how often you should produce one part or product — or complete one task to deliver a service — based on the sales rate. Consequently, it is a proxy for customer demand. 

2. Develop continuous flow wherever possible

Continuous flow refers to having each step in the production process complete one part of the product or service and immediately pass it to the next step without delay or creating in-process inventory between steps.

3. Use supermarkets to control production where continuous flow does not extend upstream

In the spots of the value stream where continuous flow is impossible and batching is necessary, resist the temptation to schedule these processes via an independent scheduling function. Instead, control their production by linking them to their downstream customers through a supermarket-based pull system. A supermarket is where a predetermined amount of standard inventory is stored, usually adjacent to the supplying process.

4. Try to send the customer schedule only to one production process

By using supermarket pull systems, you will typically need to schedule only one point in the value stream. This point is called the pacemaker process because how you control production at this process sets the pace of production for all upstream processes. 

5. Distribute the production of different products evenly over a set time at the pacemaker process, thus leveling the production mix

Most assembly departments probably find it easier to schedule long runs of one product type to avoid changeovers. However, this approach creates serious problems for the rest of the value stream and customers, such as: 

• Increases the lead time from order to delivery 
• Swells in-process inventories

The more you level the product mix (aka “heijunka”) at the pacemaker process, the more quickly you will be able to respond to different customer requirements while holding less inventory.

6. Create an “initial pull” by releasing and withdrawing small, consistent increments of work at the pacemaker process, thus leveling the production volume

Too many companies release large batches of work to the shop floor processes, which causes several problems, such as:

• There is no sense of “takt” or pull from the customer to which the value stream can respond.
• Responding to changes in customer demand becomes very complicated.
• The state of production becomes difficult to monitor.

Establishing a consistent, level production pace creates a predictable production flow. Consequently, this allows management to see problems more easily and take corrective action faster. 

A good place to start is to regularly release only a small, consistent amount of production instruction (usually between 5 to 60 minutes worth) at the pacemaker process while simultaneously taking away an equal amount of finished goods. We call this practice a paced withdrawal. And the pitch is the consistent increment of work.We calculate the pitch based on the pack-out quantity (the number of parts one finished-goods container holds) or a multiple or fraction of that quantity. For example, if your takt time is 30 seconds and your pack-out quantity is 20 pieces, your pitch is ten minutes (30 seconds x 20 pieces = 600 seconds or 10 minutes). In other words, every 10 minutes: a) give the pacemaker process instruction to produce one pack quantity and b) take away one finished pitch quantity.