【正文】 s to be set up. Withdrawals (pull) from the supermarket will control stamping’s production of leftdrive and rightdrive parts. Because stamping is a batch process by nature, Acme will start with a signal kanban (a minmax kanban often used in largebatch operation) to control stamping. The kanban card (actually a metal triangle) for left or rightdrive parts will be brought from the supermarket to the stamping press’ scheduling board every time the number of stamped parts remaining in the supermarket drops to a trigger (“minimum”) point. Stamping no longer receives a schedule from production control. When the triangle kanban arrives at the stamping press, it initiates a changeover and production of a predetermined batch size of a particular part. Stamping places newly stamped parts into small totes, which are moved into a marked area in the stamping supermarket. 33 KEY QUESTIONS FOR THE FUTURE STATE Question 5: What single point in the production chain (the pacemaker process) should Acme schedule? Since all process steps downstream of the pacemaker process need to occur in a flow, in the Acme example, the scheduling point is clearly the welding/assembly cell. Scheduling any further upstream process does not make sense because it is planned to introduce a pull system between stamping and weld/assembly. This single scheduling point will regulate Acme’s entire steeringbracket value stream. 34 KEY QUESTIONS FOR THE FUTURE STATE Question 6: How should Acme level the production mix at the pacemaker process? When the daily delivery is made to the assembly plant, 30 trays of leftdrive brackets (600 pieces) and 16 trays of rightdrive brackets (320 pieces) are typically loaded onto the truck at one time. If no one is careful, the 46 production kanban removed from these trays before loading will be send back to the weld/assembly cell in a batch. If this happens the weld/assembly cell will probably batchproduce these parts. That is, the cell will produce all 30 trays of leftdrive brackets, and then change over to make the 16 trays of rightdrive brackets, which would look like this: 1st shift 2nd shift LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLRRRRRRRRRRRRRRRR From a valuestream perspective batching is the wrong way to go. If the weld/assembly cell levels the mix of brackets it produces evenly over the shift, then the stamping press (with a shortened setup time) will have plenty of time to react to the cell’s pull for leftdrive and rightdrive parts. It will have time to replenish what was taken away without the need for much inventory in the stamping supermarket. With leveling, which implies more frequent changeovers, the cell’s production mix of trays of brackets would look like this: 1st shift 2nd shift RLLRLLRLLRLLRLLRLLRLLRLLRLLRLLRLLRLLRLLRLLRLLR 35 KEY QUESTIONS FOR THE FUTURE STATE Question 7: What consistent increment of work should Acme release and take away at the pacemaker process? Returning all 46 kanbans (two shifts worth) to the cell at once would provide no sense of takt time to the cell. Batching the volume of work like this must be avoided. A natural increment of welding/assembly work in Acme’s case is the 60 second takt time x 20 pieces per tray = 20 minutes. This is the steeringbracket pitch, which corresponds to one kanban for one tray of 20 steering brackets. This pitch means that Acme will practice paced release of work instruction and paced withdrawal of finished goods at its weld/assembly cell. Each column in Acme’s steeringbracket loadleveling box represents a 20minute pitch increment. The two rows are designated for leftdrive and rightdrive kanban. Every 20 minutes, a material handler brings the next kanban (the next increment of work) to the weld/assembly cell and moves the justfinished tray of brackets to the finished goods area. If a tray is not finished at the 20minute pitch increment, then Acme knows there is a production problem. 36 KEY QUESTIONS FOR THE FUTURE STATE Question 8: What process improvements will be necessary for Acme’s value stream to flow as the future state design describes? Achieving the material and information flows we envision for Acme stamping requires the following process improvements: Reduction in changeover time and batch sizes at the stamping press, to allow faster response to downstream usage. Elimination of the long time (10 minutes) required to change between leftdrive and rightdrive fixtures in welding, to make possible continuous flow and mixed production from welding through assembly. Improvement in ondemand uptime of the second spotweld machine, as it will now be tied to other processes in a continuous flow. Elimination of waste in the weld/assembly cell, to reduce total work content down to 168 seconds or less (Which allows use of 3 operators at the current demand level.) 37 FUTURE STATE MAP FIRST VIEW Source: Learning to See Value Stream Mapping to Add Value and Eliminate Muda, Mike Rother and John Shook 2 shifts 18,400 pieces/mo 12,000 “L” 6,400 “R” Tray = 20 pieces 1 x daily WELD + ASSY Takt = 60 seconds 2 shifts C/O = 0 Uptime = 100% total work content = 168 seconds SHIPPING Staging First View of the