Designing a Salue Stream Flow Through Shared Resources
ISE Magazine January 2019 Volume: 51 Number: 1
By Kirk Bolton
A shared resource is deﬁned as a process that produces parts for multiple product families. And while it can be challenging to incorporate shared resources into the overall value stream, implementing ﬂow in these complex environments is essential to creating an autonomous operation that can fuel business growth.
The product family matrix
The ﬁrst step in designing value stream ﬂow through shared resources is to determine which processes are, in fact, shared. To accomplish this task, organizations use a valuable tool called a product family matrix.
Once an organization determines product families, each becomes one value stream. Therefore, when the organization begins to map a value stream, it is really mapping the ﬂow of one product family from end to end, which includes the upstream shared re-sources.
Value stream mapping with shared resources
When an organization understands which processes are dedicated and which are shared, it can begin mapping the value stream. The ﬁrst step is to capture all processes required to bring the product from raw material to the customer. Since both dedicated and shared processes will be on the value stream map, the latter are indicated with the # symbol inside the process box.
In addition to listing the processes required to build the product, an organization also needs to list the inventory observed before those processes. Usually, there are two types: Inventory for the product family being mapped and “other” inventory for the other product families not being mapped.
To capture inventory for dedicated processes on a value stream map – i.e., inventory for the product family being mapped – an organization simply counts the inventory waiting to be consumed before each dedicated process. Then, on the lead-time ladder, this inventory number gets expressed in terms of the demand for the product family being mapped.
For example, if the demand for a product family is eight units per day and there are 24 units found before a manual deburr process dedicated to that product family, then the 24 units found before the manual deburr process represent three days of inventory (24 units / 8 units per day = 3 days). This amount would be shown on the lead-time lad-der.
When inventory is found before a shared resource, organizations follow a process to document the mixed inventory on the value stream map. When the demand for the other product families on the shared resources is known, the progression of work is as follows.
- Add the dedicated and non-dedicated inventories together.
- Divide the sum by the total demand on the shared resource.
The result is the number of days’ worth of inventory in front of the shared resource and would be the number put on the lead-time ladder.
However, if the demand for the other product families is not available, the inventory must be separated into the product family inventory being mapped and all “other” product families. To do this, an organization would list the family inventory being mapped on the bottom, e.g., 24 units, then list the inventory for all “other” families on the top, e.g., 180 units. Since an organization usually knows the demand for the family being mapped, it would then divide the inventory present by the demand.
Six key questions to ask
Once an organization has created the current state value stream map, the next step is to proceeds with designing the future state using the eight lean guidelines: takt time; ﬁnished goods strategy; continuous ﬂow; FIFO (ﬁrst in, ﬁrst out); pull; schedule only one point; interval; pitch. reating ﬂow through shared resources also involves reviewing these six key questions in the following manner:
- If the answer to question one is yes, then skip to questions four through six.
- If the answer to question one is no, but the answer to question two is yes, skip to questions four through six.
- If the answers to questions one and two are no, then question three is a yes by default. So skip to questions ﬁve and six.
- Can the product families be extended? This question is meant to ask about further dedicating equipment that is currently shared to speciﬁc product families.
- Can process families be created with dedicated equipment? When a single product family cannot be dedicated to a process, an organization must try to dedicate multiple families to a given process.
- Can ﬂow be created through the true shared resource? If the answers to both questions one and two are no, then all that is left to consider is whether an organization will de-sign ﬂow or pull through the “true” shared resource. A true shared re-source is one that cannot have any level of dedication.
- Can an operation balance to created continuous ﬂow? To understand whether continuous ﬂow can be created where there are shared resources, the ﬁrst step is to look at both the takt and interval for the area.
- How will the shared resources know what to make next? In a continuous ﬂow cell, it is simple to know what to work on next: Whatever is coming down the assembly line from the previous process.
- How will the shared resources be managed? This last question is a bit tricky. In reality, an organization does not want to “manage” the shared re-source at all.
Simplifying complex shared resources for business growth
Most organizations use an abundance of personnel to keep tabs on orders on the shop ﬂoor and prioritize “hot” orders. In addition to shared resources, this means an organization has competing schedulers, planners, expeditors and others from different areas all trying to satisfy customers.
But when shared resources do not have to be managed because they are incorporated into the self-healing value stream, little intervention is required by management to get the product to the customer. Instead, product will already ﬂow or be pulled from one process to the next based on a dynamic system de-sign that mirrors the future state value stream map. By scheduling only one point in the value stream, all other processes know what to work on without a schedule, minimizing the need for prioritization, expedites and so on.
An organization can then teach people who work in the ﬂow to ﬁx it on their own when it begins to break down – and the answer cannot be, “contact a supervisor or manager.” Once managers are no longer busy at-tending meetings, reading status emails or intervening to ﬁx ﬂow, they will be able to spend their free time helping to grow the business, acquiring new customers, improving brand recognition and much more.