What is value stream?
Value stream include all activities for a product from raw materials to finished goods, and finally deliver to customers, all the actions, both value added and non value added.
Why need value stream mapping?
- Value stream mapping shows the connection between products flow and information flow
- Value stream mapping can intuitively understand customer demand
- Value stream mapping shows the source of waste in value chain
- Value stream mapping is a tool to improve and optimize all parts of value stream
- Value stream mapping also provide the base to implement lean production
How to make value stream mapping?
- Choose a product or product family to analyze (considering yearly volume, representative product, e.g.)
- Draw customer & add customer data box (order quantities, order size, shipment schedules, lead time, e.g.) to define customer requirements
- Draw main suppliers & add data box for suppliers
- Draw process steps (process steps is a point in a value stream where flow stops and inventory has an opportunity to accumulate)
- Collect process data (Number of operators, number of shifts, OEE, scrap rate, changeover time, changeover frequency, batch size, cycle time, processing time e.g.)
- Collect inventory data (total pcs stored)
- Draw external material flow (draw deliveries from supplier and to customer, add data box for frequency of deliveries and box size)
- Draw push or pull systems for internal material flow
- Calculate processing time/manufacturing lead time
Main Icons for value stream mapping
Value stream mapping
Tips for drawn value stream mapping
- Always start from the customer
- Should get actual data by walking on the shop floor for the observation data
- Value stream mapping is not a process map or layout of the factory
- Create both the current and future value stream mapping
- Value stream mapping should create by a team
- Value stream mapping is a tool to drive continues improvements
Takt time & cycle time
Takt time: How frequently we must produce a quality piece to meet customer expectations
Cycle time: cycle time have operator cycle time and machine cycle time
- Operator Cycle Time - The total time required for an operator to complete one cycle of operation, including walking, load/unload, inspect, etc
- Machine Cycle Time– The total time between the instant the on button is pressed and the point at which the machine returns to its original position after completing the target operation
Examples to calculate Takt time
- If the customer weekly demand is 90000 pcs, factory 6 days working and 3 shifts/day
- Total pieces required per shift = 90000/6/3= 5000 pcs/shift
- A shift is 8 hours standard working time, equals to 480 minutes, minus breakdown time, clean time which can not used for producing
- Availability time per shift = 480(standard time)-30(breakdown time)-10(clean time)=440 minute
- Takt time = 440/5000= 0.088 pcs/second or 5.28 pcs/minute
The difference between value stream
mapping & process map?
Value stream mapping is different from process map, but they compliment each other