Topic: VALUE STREAM MAPPING

Transcription

1 Topic: VALUE STREAM MAPPING Development of a Problem Solving Model for the Hong Kong Textiles and Clothing Industries Project HKRITA Ref. No. : RD/PR/001/07 ITC Ref. No. : ITP/033/07TP

2 Value Stream - Definition All of the steps required to bring a product or service from raw state through to the customer 2

3 Value Stream Mapping Definition A visual representation of the material and information flows a product takes from sales order to finished product. It is a diagnostic tool due to Shows the linkage between material and information flow of a product or processes Forms the basis for an implementation plan. Distinction between value add and non value add activities (Waste) 3

4 VSM Symbols 1) VSM Process Symbols Customer/Supplier Dedicated Process Shared Process Data Box Work cell 2) VSM Material Symbols Inventory Shipments Push Arrow Supermarket Material Pull FIFO Lane Safety Stock External Shipment 4

5 3) VSM Information Symbols Production Control Manual Info Electronic Info Production Kanban Withdrawal Kanban Signal Kanban Kanban Post Sequenced Pull Load Leveling MRP/ERP Go See Verbal Information 4) VSM General Symbols Kaizen Burst Operator Other Timeline 5

6 VSM Process Symbols Supplier --- when in the upper left, the usual starting point for material flow. Customer --- when placed in the upper right, the usual end point for material flow. Customer/Supplier Dedicated Process A process, operation, machine or department, through which material flows. It represents one department with a continuous, internal fixed flow path. A process operation, department or work center that other value stream families share. Estimate the number of operators required for the Value Stream being mapped. Shared Process 6

7 This icon goes under other icons. Having significant information/data required for analyzing and observing the system. E.g cycle time, changeover time, Lot size, uptime, etc Data Box Indicates multiple processes are integrated in a manufacturing workcell E.g cells usually process a limited family of similar products or a single product. Product moves from process step to process step in small batches or single pieces. Work cell 7

8 VSM Material Symbols Inventory - Represents storage for raw materials and finished goods, also show inventory between two processes. - While mapping the current state, the amount of inventory is counted by quick count, that amount is noted beneath the triangle. - If more than one inventory accumulation, use an icon for each. Shipments -Represents movement of raw materials from suppliers to the receiving dock/s of the factory. Or, the movement of finished goods from the Shipping dock/s of the factory to the customers - Represents the pushing of material from one process to the next process. Push means that produces something regardless of the immediate needs of the downstream process. Push Arrow 8

9 - This is an inventory supermarket (kanban stockpoint). - Like a supermarket, a small inventory is available one or more downstream customers come to the supermarket to pick out what they need. the upstream workcenter then replenishes stocks as required. - It reduces overproduction and limits total inventory. Supermarket Supermarkets connect to downstream processes with this "Pull" icon that indicates physical removal. Material Pull - First-In-First-Out inventory. Use it when processes are connected with a FIFO system that limits input. E.g an accumulating roller conveyor - Record the maximum possible inventory. FIFO Lane 9

10 Safety Stock - Represents an inventory safety stock - Avoid problems such as downtime, to protect the system against sudden fluctuations in customer orders or system failures. - Notice that the icon is closed on all sides, it means a temporary, not a permanent storage of stock Shipments from suppliers or to customers using external transport. External Shipment 10

11 VSM Information Symbols Represents a central production scheduling or control department, person or operation. Production Control Represents general flow of information from memos, reports, or conversation, frequency and other notes. Manual Info Electronic Info Represents electronic flow E.g electronic data interchange (EDI), the Internet, Intranets, LANs (local area network), WANs (wide area network). Also indicate the frequency of information/data interchange, the type of media used ex. fax, phone, etc. and the type of data exchanged. 11

12 - It triggers production of a pre-defined number of parts. - It signals a supplying process to provide parts to a downstream process. Production Kanban Withdrawal Kanban -Represents a card or device that instructs a material handler to transfer parts from a supermarket to the receiving process. -The material handler (or operator) goes to the supermarket and withdraws the necessary items. Signal Kanban - Used whenever the on-hand inventory levels in the supermarket between two processes drops to a trigger or minimum point. - When a Triangle Kanban arrives at a supplying process, it signals a changeover and production of a predetermined batch size of the part noted on the Kanban. - It is also referred as one-per-batch kanban. 12

13 - A location where kanban signals reside for pickup. - Often used with two-card systems to exchange withdrawal and production kanban. Kanban Post - Represents a pull system that gives instruction to subassembly processes to produce a predetermined type and quantity of product (one unit), without using a supermarket. Sequenced Pull A tool to batch kanbans in order to level the production volume and mix over a period of time Load Leveling 13

14 Scheduling using MRP/ERP or other centralized systems. MRP/ERP Gathering of information through visual means. Go See Represents verbal or personal information flow. Verbal Information 14

15 VSM General Symbols Used to highlight improvement needs and plan kaizen workshops at specific processes that are critical to achieving the Future State Map of the value stream. Kaizen Burst Operator -Represents an operator. -It shows the number of operators required to process the VSM family at a particular workstation. Other useful or potentially useful information. Other -The timeline shows value added times (Cycle Times) and non-value added (Wait) times. -Use this to calculate Lead Time and Total Cycle Time. Timeline 15

16 Value Stream Analysis Mapping Define and Pick the product or product family Create Current State Value Stream Mapping (CSM) Value Stream Mapping Create Future State Value Stream Mapping (FSM) Develop an implementation plan and Execution 16

17 Use Incorporate Manufacturing/Service Considerations to introduce Value Stream Mapping Process At least four steps to address the wastes using value stream mapping. Use icons to identify processes (Step 1) Record the data (E.g. Cycle time (CT), Change Over Time (CO), Utilization Time (UT), throughput, setup time), for processes in value stream maps (Step 2) Analyze materials use and need in a materials line for value stream maps. (Step 2) Find Lean and opportunities in future state value stream maps. (Step 3 and 4) 17

18 Stage 1 Define and Pick the product or product family 1. Understand business goals and customer objectives 2. Select champion and value stream leaders based on proven criteria for success 3. Define product families based on common processes and equipment Product-Volume Chart Product-Process Matrix 18

19 Stage 2 Create Current State Value Stream Mapping (CSM) 1. Define the scope of the value stream map. 2. Set agreement on the symbols, icons, data to use. 3. Sketch a map. 4. Gather and create as much information about causes of waste (include customer, suppliers, the material moves between processes and the inventory levels etc.) 5. Build a Current State Value Stream Mapping. 6. Make a list of remarks for further improvements. 19

20 Record Data for Processes in Value Stream Maps Uncover wastes in value stream mapping is to select one or two performance metrics to measure for each process in the value stream. Collect data about current state (This step required additional time and/or resources. For instance, Weigh the amounts of scrap and wastes generated by each process during a shift This data collection allow to appropriately target Lean improvement efforts on the highest priority problems, and thereby achieve the greatest benefits. 20

21 Analyze materials use and need in a materials line for value stream maps. (Step 2) Raw materials are often a large source of a product s costs, so looking explicitly at the material flows in a value stream is another way to leverage greater gains. Draw a materials line on the bottom of a value stream map that shows two types of data: 1. Amount of raw materials used by each process in the value stream; 2. Amount of materials that end up in the product and add value from a customer s perspective. The materials line equal to timeline on value stream maps, and can be developed for any type of resource (e.g. water, energy, total materials, and/or a critical substance used in the product). 21

22 Draw a Current State Value Stream Map Step1. Draw customer, supplier and production control icons. Step2. Enter customer requirements per month and per day. Step3. Calculate daily production and container requirements. STEP 1 STEP 2 STEP 3 STEP 3 22

23 Step4. Draw outbound shipping icon and truck with delivery frequency. Step5. Draw inbound shipping icon, truck and delivery frequency. STEP 5 STEP 4 23

24 Step6. Add process boxes in sequence, left to right. Step7. Add data boxes below. STEP 6 STEP 7 24

25 Step8. Add communication arrows and note methods and frequencies. Step9. Obtain process attributes and add to data boxes. Step10. Add operator symbols and numbers. STEP 8 STEP 10 STEP 9 25

26 Step11. Add inventory locations and levels in days of demand and graph at bottom. Step12. Add push, pull and FIFO icons. Step13. Add other necessary information. STEP 13 STEP 11 STEP 12 26

27 Current State Value Stream Map STEP 14 STEP 16 STEP 15 27

28 Step14. Add working hours. Step15. Cycle and Lead Times Step16. Calculate Total Cycle Time and Lead Time Cycle Time = Actual time required for a worker to complete one cycle of his job process Lead Time = The period of time between the initiation of any process of production and the completion of that process. 28

29 Completed Current Value Stream Map 29

30 Stage 3 Create Future State Value Stream Mapping (FSM) Supporting Improvements 1. What is the process improvements need to be addressed immediately? Material Flow 2. Where can implement flow? 3. Where should you reduce batch size to improve responsiveness? Customer Delivery Strategy 4. Should you build to customer order or finished goods? 5. What single point will you schedule to customer requirements? Information Flow 6. How will you schedule or pull material from upstream? 30

31 Future Value Stream Mapping STEP 1 STEP 5 STEP 4 STEP 3 STEP 2 STEP 6 31

32 Steps 1.Calculate Takt Time Takt Time is the average time between production units necessary to meet customer demand. Takt Time = Available time Number of units From the example 32

33 2. Identify Bottleneck Process The bottleneck process is the operation with the longest cycle time. (From the example, this is machining at 44 seconds.) Cycle Time Bottleneck Process Operation The bottleneck is important because it: 1. Determines total system output. 2. Becomes the primary scheduling point 33

34 3. Identify Lot Sizing/Setup Opportunities Present lot size is 1000 pieces, about two day's production. This requires at least 3-6 days finished goods and prevents daily adjustments to mix or demand. If the lot size were simply cut, it would allow faster response but additional setup time in machining would use available time. Machining could not meet the average customer requirements. However, if a focused setup reduction is made on machining and setup becomes minutes, a batch size of 500, or even 250 is feasible. The mapping team established this as a goal, noted by a Kaizen Burst. 34

35 4. Identify Potential Workcells The balance chart shows cycle time for each of the five process steps. Machining and honing operations are closely balanced. Cycle times for clean/deburr, inspection and packaging are quite short in comparison. Short cycle time may due to the low utilization in workcell. operations Clean/ Deburr inspection packaging Cycle time The shortest Relatively long short equipment specialized, high-speed little workbench and hand tools little workbench and hand tools Balancing the operation Number of operators Clean/deburr scaled down as manual or semimanual operation Workcells are lot more involved than suggested here. Important to make reasonable guesses about the general configuration. A Kaizen Burst identifies a need for more work. 35

36 5. Determine Kanban Locations With a workcell for five processes, scheduling between them becomes a trivial case. They will be directly linked with continuous or small-batch flow. Kanban can apply at two other locations, between cell and supplier or customer The detailed design of the kanban system is shown as a Kaizen burst. Inventory levels are current best estimates. 6. Establish Scheduling Methods Kanban and direct links now schedule all operations short term. Both the workcell and the supplier, however, need forecasts to plan staffing and possible changes in inventory levels. The map shows this monthly information flow. (Especially for Purchasing) 7. Calculate Lead and Cycle Time. The final step in the Future State Map is to complete the timeline at bottom, and calculate Lead Time, Cycle Time and Work Time. 36

37 Stage 4 Develop an implementation plan and Execution 1. Formulate an implementation plan based on the future state map. 2. Start to implement. 3. Review the progress 4. Re-map the process 37

38 Results In this example, the mapping team estimates Lead Time reduction of 85% Productivity increase of 25% Inventory will decrease about 85% Many additional, but unpredictable benefits are also likely 38

39 Limitations of Value Stream Mapping 1. The Problem of Over-hype This situation sets up unrealistic expectations and diverts attention from important aspects of complex problems. 2. Non-Technical Aspects of Lean There may also be quality issues that the company could address through Six Sigma or TQM techniques. 5S can clean up the plant, improve safety and further raise productivity. Value Stream Mapping addresses none of these directly. 3. Fuzzy Definitions The map does not begin to capture "all specific actions" "Value Stream" conjures a vision of water running through a series of value-adding activities. But many icons do not depict value adding activities, do not touch the product and do not flow like a stream. 39

40 4. High Variety Situations VSM was developed and popularized in the automotive industry. Automotive plants are highly focused factories with a narrow family of products for a few customers. VSM works well in these situations. 5. Symbology Affects Thinking Many VSM symbols may lead the user to employ these technique seven when they are inappropriate. 6. Training A VSM group requires training on symbols and mapping techniques and on the Lean Manufacturing elements that the symbols represent. This contrasts with Process Mapping which only requires a trained facilitator. 40

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