Value maps, also known as Value Stream Map (VSM) value flow graphs, are tools used to fully understand processes, both within the organization and in the supply chain. The main objective by which value maps are developed is that they allow us to broadly identify activities that do not add value to the process, in the same way they allow us to know the time associated with such activities.
In practice, value mapping has become an essential activity in the face of the formulation of improvement plans, in such a way that it is part of the process diagnosis (current VSM) and the proposal of improvement strategies (VSM future).
When mapping the value flow, we must answer a number of critical operations-related issues:
- What is the capacity of the production system?
- What are the process bottlenecks?
- What is the customer’s purchase rate?
- What is the available capacity, and what is its utilization?
- What are the process restrictions? Are these internal or external?
- How can we improve the process to meet business objectives?
A value map is a graphical representation of production elements and information that allows you to know and document the current and future state of a process. It is the basis for the analysis of the value that is provided to the product or service, and is the source of knowledge of the actual constraints of a company, since it allows to visualize where the value is and where the waste is.
Relevant Indicators of a Value Map
Takt time is an indicator of the customer’s frequency of purchase. For many experts this is an objective time at which the production system must adapt to meet customer expectations. It is calculated as follows:
Takt Time – Available Time / Demand
Workday: 8 hours per shift
Lunch time: 0.5 hours per shift
Number of shifts: 1 daily shift
Business days per month: 22 days per month
Monthly demand: 7,510 pieces per month
Available time (8 hours/shift) – (0.5 hours/shift) – 7.5 hours/shift
Available time (7.5 hours/shift) * (60 min/hour) – 450 min/turn
Available time (450 min/turn) * (1 shift/day) * (60 sec/min) – 27,000 sec/day
Daily Demand (7,510 Pieces/Month) / (22 days/month) – 341 pieces/day
Takt time (27,000 sec/day) / (341 pieces/day) – 79 sec/piece
That is, a customer buys a part every 79 seconds, so that the standard time per piece must be equal to or less than 79 seconds.
Individual cycle time
This is the standard time associated with each operation in the process. For example: The time associated with painting a part, or the standard time associated with packing it.
Total cycle time (Manufacturing Lead Time)
It is the time that all operations last, it is calculated by adding the individual cycle times.
Lead time GAP
This time interval is when forecasts should be made against future order points and quantities. The magnitude of the GAP is directly proportional to the errors in the forecasts.
Logistics Delivery Time (Lead Time Logistic)
It understands the time interval it takes for the organization from when it is supplied with raw materials, materials and inputs until the finished product is distributed to the customer.
How to make a Value Map step by step?
Basic symbology of a Value Map (VSM)
External sources: This symbol represents customers and vendors.
Transfer Arrow: This symbol represents the transfer of raw materials and finished product. From supplier to plant or plant to customer.
Transport by cargo truck.
Transport by train.
Transport by plane.
Operation of the process.
Information: Forecast, production plan, scheduling.
Data locker with process indicators.
Push arrow to connect the flow of materials between operations when it is carried out by a push system.
Drag arrow to connect the flow of materials between operations when it is performed using a pull system.
Arrow to connect the flow of materials between operations when it is carried out by a sequence: “first inputs, first outputs”
Inventory: Raw material, product in process, finished product.
Information transmitted manually.
Information transmitted electronically.
Kaizen Lightning: This symbol represents the points where improvement events focused on implementing the expressed Lean Manufacturing tool should be performed.
Load leveling: A tool used to intercept kanban batches and level production volume.
Timeline: Displays cycle times for activities that add value, and times for activities that do not add value.
Establish product families
In order to identify the product families on which we will apply the value map, it is necessary to take into account the operations that each product passes through, and the individual cycle time of those operations.
We can say that a product family is a group of references that go through the same operations and whose cycle times do not vary much from one reference to another.
Record the following information
- Cycle times for each operation in the process.
- Availability of each equipment in the process.
- Product change time for each operation (enlistment).
- Inventories at each stage of the process.
- Know the customer’s demand, the means by which you request, the frequency and quantity of orders.
- Forecasts used to predict demand and supply needs, the means by which it is ordered, the frequency and quantity of orders that are made to suppliers.
- Know the sequence of the process, the flow of materials and information.
Steps to Build a Value Flow Map
1. The map construction starts by placing the client symbol in the upper-right corner of the plane. We then connect the flow of information (manual or electronic) through which customer demand (forecast and actual orders) is related to production control. Next, production control relates to the requirements sent to the vendor with the material forecasts, connecting the flow of information by which the need for materials relates to suppliers.
2. The next step is to represent transportation from vendors to the company.
3. We draw the sequence of operations by setting the time of each operation, product change time, equipment availability, on-hand time, and in-process inventories.
4. We represent the production program that indicates the quantity to be processed by each operation, as well as the flow of information (manual or electronic) that relates these operations. We also represent transportation from the factory to customers.
5. We represent by a ladder the cycle times of each operation (added value) at the bottom of the steps; and the time that does not add value in the upper steps. Inventories must be recorded based on time and are part of what does not add value in the process. To do this we can divide the quantity of each inventory by the daily quantity required by the customer.
6. We calculate the takt time:
Available time – 27000 seconds / day
Daily Demand – 500 units / day
Takt time s 27000 / 500 x 54 seconds / unit
This means that the customer buys with an average frequency of 54 seconds per day, so that this time should be our production goal. Already in the Value Map we can see that there are processes to be improved and inventories to be reduced. The next step will then be to build the Future Value Map in which Kaizen improvement events will need to be identified.