the goal.ppt

1、The Goal,A Process of Ongoing Improvement Eliyahu M. Goldratt and Jeff Cox,The Goal,Back to the story: Q. Where does Alex and company find the bottleneck? They find two bottlenecks, NCX-10 and Heat Treat Q. What is thier first approach to improving the flow through the bottlenecks and ultimately imp

2、roving productivity. 1. Move QC in front of bottlenecks. 2. Make a list of all late jobs and what components from those jobs flow through the bottleneck machines. They then create a schedule/list in due date order and instruct the bottleneck operators to only work on those jobs in that order.,The Go

3、al,Back to the story: Q. Does this scheduling system work (e.g. get late jobs completed while always keeping bottleneck running)? A. No, because the late job components are not always waiting in front of the bottleneck machines. Q. What do they do to rectify this? A. Create a red tag (parts that tra

4、vel through the bottleneck) / green tag system for all jobs throughout the plant such that any job with a red tag which arrives at a machine is given priority. If they are in the middle of a run, then if the run takes longer than 30 minutes to complete, stop that job and start the red tag job. If no

5、 red tags, then ok to process green tag jobs. If more than one red (or green tag), then process job with lower number on tag.,The Goal,Back to the story: Q. What do they do next to further off-load the Herbies / bust the bottleneck? Gold tags placed on parts that have traveled through the bottleneck

6、 everyone extra careful not to damage. Dedicate personnel at NCX-10 and Heat Treat even though they are idle much of the time, just dont let machine idle. Send out some portion of heat treat parts to vendor in town. Found old equipment (that is less efficient) to run in parallel to NCX-10. Fully loa

7、d furnace when possible (e.g. mix batches). Reduce setup time with new fixtures. Were able to process some parts differently so heat treat wasnt required.,The Goal,Back to the story: Q. What were the results of these bottleneck busting tactics? New monthly shipping record from old record of 2 millio

8、n to new record of 3 million. 57 customer orders shipped versus old record of 31. WIP Inventories reduced 12%.,The Goal,What happens next? The bottlenecks are apparently expanding material is backing up at the milling machines, and non-bottleneck parts (green tags) are not reaching assembly even tho

9、ugh all bottleneck parts (red tags) are available at assembly.,The Goal,What happens next? Jonah revisits plant and discusses relationship between bottleneck(X) and non-bottleneck(Y) machines. Y X 3) Y A 4) Y Product A X Y X S X Product B S E M B L Y,The Goal,Jonah believes the “new bottlenecks” are

10、 not real bottlenecks, but self-created bottlenecks. Why? Material is being “released” to the plant just to keep the non-bottleneck machines busy. This improves these machines efficiency measures, but does not help the goal. Jonah: “A system of local optimums is not an optimum system at all; it is a

11、 very inefficient system”. Lesson: Do not try to make non-bottlenecks work all the time. They should be idle some of the time!,The Goal,So how do you go about fixing the problem of keeping the non-bottleneck machines working at the same rate as the bottleneck? Recall the boy scout hike: Herbie is in

12、 the middle of the line and cannot be moved, so how do you keep the kid in the front walking at the same pace as Herbie? Alexs kids: use a rope and a drum. Rope: Attach a rope from Herbie (bottleneck machine) to the kid at the front (assembly). The length of rope represents inventory. Drum: Herbie t

13、ells the kid at the front to slow down or speed up (beats the drum). Need some kind of signaling or communication between assembly and the bottleneck.,The Goal,How is the rope and drum concept implemented in the plant? Identified it takes about 2 weeks from when parts are released to the floor until

14、 they get to bottleneck. Setup system that monitors when inventory is processed at the bottleneck. Material required 2 weeks later is then released to the floor. Non-bottleneck parts are released according using the same principle but tied to assembly.,Bottleneck,Material Release,2 weeks lead time,C

15、ommunicate release,The Goal,What is the result of this new release system? WIP is down. Revenues are up. Efficiencies dropped initially, but have come back up. The backlog of orders is completely gone (satisfied customers). How does management respond? Happy Somewhat skeptical success will last Want

16、s 15% more revenue next month!,The Goal,In order to improve by another 15% what does Jonah suggest as the “next logical step”? Cut batch sizes for non-bottleneck parts in half. What is the impact of reducing these batch sizes? WIP for non-bottleneck parts reduced by half. Significantly reduce time p

17、arts spend in plant. Leads to increased responsiveness (from 6-8 weeks to 3-4 weeks). What about the time to handle increased number of setup? Doesnt matter if occurs on non-bottleneck operations.,Process Time,Setup Time,Queue Time,Wait for Assembly Time,Time parts spend in the plant,The Goal,Also t

18、o help get the 15%, Alex calls the marketing/sales manager and bets him he can reduce lead time to fill orders. What does Alex expect to gain by reducing lead times to ship from what used to be 4 months to 4 weeks? Increased sales! The bottleneck had moved to customer demand. Quick response on promi

19、sed due dates should translate to a competitive advantage.,The Goal,Everything is going good now except it looks like part costs are going up. However, in reality all costs have gone down. How can this be? The accounting rules: Cost per part = raw material + direct labor + burden cost Burden cost is

20、 all the indirect labor costs. Burden = direct labor x burden factor Cost per part has risen because more setups are occurring because of smaller batch sizes. However, workers were idle, so the increased number of setups didnt really increase costs.,The Goal,What other performance measure made them

21、not look as good as they actually were. Answer: Inventory Inventory is counted as an asset on the balance sheet. When the plant worked hard to reduce inventories to improve their throughput and responsiveness, it looked as if their assets had fallen.,The Goal,Sacred Cows Slaughtered: Worker efficien

22、cy Optimal batch size Releasing work to the floor to keep people busy Accounting rules,The Goal,Why Alexs plant was successful: Change in Focus from the “cost world” to the “throughput world”,Cost,Throughput,Inventory,Throughput,Inventory,Cost,The Goal,What process did they use to shift their focus

23、to the “throughput world”? The Theory of Constraints Step 1: Identify the systems constraints (NCX10 and oven) Step 2: Decide how to exploit the systems constraint (dont take lunch break on bottleneck machines) Step 3: Subordinate everything else to the above decision (red tags and green tags) Step 4: Elevate the systems constraint (bring back