Lean Manufacturing, Value Stream Mapping, Mapping the Current State

Example of a Simple Present State Mapping of a Process of Five Steps, in a real life situation the current state map will be much more complex than this simple example, however even the most complex one can be developed understanding this basic concept.

Value Stream Mapping, Current State Map

Note that it could exist a FIFO line between any operation but for sake of simplification will be omitted by now. Also note that there is a serious capacity excess on the forming operation.

Days of Inventory at Hand:

The inventory on hand in each operation is calculated by dividing the daily shipping quantity by the parts inventory.

Example:

How many days of inventory on hand is at the cutting operation station?

Daily shipping = 200 units per day

Parts inventory at cutting station = 1000

Inventory at hand for the cutting operation = 1000/200 = 5 days

Also the materials days inventory can be calculated for each particular station to know process bottle necks.

Example process capacity Vs inventory rate:

How many days of inventory is for the operation “cutting”

The CT= 50 Sec

Available time= 27,600

Up Time = 27,600 X 0.95 = 26220 Sec

Units per day capacity= (26220/50) = 524.4

Parts inventory= 1000 parts

Inventory to process at station “cutting” = (1000/524.4) = 1.9 days, we can perform the same calculations for all other operations.

Basic Attributes Definitions:

CT= Cycle Time: The time that takes to complete a given operation or process

CO= Changeover Time: The time that takes to change a tooling, prepare a production line, cell or a production unit for a new run.

Avail= Availability Time: Is the available working time available in one shift minus programmed brakes such as lunch time and resting brakes, normally given in seconds.

Example For the Cutting Operation:

If a working shift has 8.5 hour = 8.5X 60 = 510 minutes minus 0.5 hours lunch = 510 - 30 = 480 minutes minus two resting brakes of 10 minutes each will be 480 - 20 = 460 minutes or 27600 Seconds of available time

UT= Uptime %= (Availability-CO)/(Availability) all converted to seconds.

Example:

Considering a given tooling changeover time of 20 minutes, then the available uptime for the example will be:

UT= (460 - 20)/460 = 0.95 or 95%

Continue Future State Mapping Part One >>