posbul1a Drum –Buffer-Rope Based on : R. Holt, Ph.D., PE Principy Resource : http://www.allaboutlean.com/drum-buffer-rope/ imaginace Simplified Drum Buffer Rope (S-DBR) Principy Most importantly, it does try to constrain the work-in-progress and aims to prevent an overloading of the system. As such it can be considered sort of a pull system like Kanban or CONWIP, and hence Drum-Buffer-Rope is superior to the traditional push systems. Push –MRP-II Pull –JIT- kanban= WIP=NV WIP=NV Nejdůležitější je omezení rozpracovanosti a díky tomu zabránit přetížení systému. Jako takový to může být považován Kanban nebo CONWIP, které jsou postaveny na principu PULL. Metoda Drum-Buffer-Rope, je mixem obou systémů a o mnoho lepší než tradiční PUSH systém. Při řízení a kontrole toku se musí brát do úvahy to, že se pozice úzké místa může měnit. System not controlled (neregulovaný systém) Based on pictures taken from CH.Hohman show System not controlled and modification DBR Systém, který není řízený a modifikace takového systému na principu DBR. Based on pictures taken from CH.Hohman show Rope opened raw material valve Zpětná vazba pro kontrolu množství vstupujícího materiálu na vstupu sysému - LANO Based on pictures taken from CH.Hohman show We Measure Operational Efficiency * Work flows from left to right through processes with capacity shown. * Process A B C D E RM FG Capability (Throughput Rate) Parts/Day 7 9 5 8 6 Excellent Efficiency--Near 100% Chronic Complainer Too Much Overtime Market Request 11 RM = raw material FG = finished goods Reward Based on Efficiency * Work flows from left to right. * Process A B C D E Capability(Throughput Rate) Parts/Day 7 9 5 8 6 Both found ways to look busy and appear to have a capacity of 5 parts/day. RM FG „horní tok“ „dolní tok“ In reality... Process A B C D E Potential P/D 7 9 5 8 6 Reality 5 5 5 5 5 * Processes A and B won’t produce more than Process C for long. RM FG P/D=parts/day Then Variability Sets In * Processing times are just AVERAGE Estimates (procesní časy jsou pouze průměrné odhady) * Process A B C D E Reality 5±2 5±2 5±2 5±2 5±2 * RM FG 7 9 5 8 6 What’s an Average? 50% Process A B C D E Reality 5±2 5±2 5±2 5±2 5±2 Probability 0.5 0.5 0.5 0.5 0.5 * Half the time there are 5 or more per day at each process--Half the time less Two at a time: 0.25 0.25 Over all: 0,5*0,5*0,5*0,5*0,5=0,03125=3% Chance of 5 per day !!! RM FG 7 9 5 8 6 RM=Raw Material ->komponenty, FG=Finished Goods->výrobky Previous Solution (not good one !): Inventory WIP 5 5 5 5 5 Total 25 in WIP Process A B C D E Variable 5±2 5±2 5±2 5±2 5±2 Process * Put a one day of inventory (WIP) at each process! RM FG 7 9 5 8 6 WIP= Work in Progress = NV=Nedokončená výroba Před každý stroj dáme rezervu jednoho dne, což je reprezentováno maximálním průtokem úzkého místa za jeden den RM=Raw Material ->komponenty, FG=Finished Goods->výrobky System Variability Takes OveràChaos Variable 5±2 5±2 5±2 5±2 5±2 Process WIP 3 0 10 8 4 Total 25 RM FG Process A B C D E Inventory (WIP) quickly shifts position. (Velikost NV před každým strojem mění svou velikost) Inventory manager tries to smooth it out. (Manažer skladu se to snaží tuto situaci vylepšit) Distribution problems result. Costs go up! (Větší problémy v distribuci, náklady stoupají) 7 9 5 8 6 System Variability Takes Over--Chaos WIP 3 0 10 8 4 Total 25 RM FG An Average of 5 means sometimes 3 and some times 7 Process A B C D E 7 9 5 8 6 System Variability Takes Over--Chaos WIP 3 0 10 8 4 Total 25 Variable 5±2 5±2 5±2 5±2 5±2 Process Shifting work-in-process creates large queues at some locations. This makes work wait longer to be processed. Other workstations are starving for work (B) The work they could do is delayed because they have no input material. They can’t take advantage of their extra capability. So....... ? RM FG 7 9 5 8 6 Process A B C D E System Variability Takes Over--Chaos WIP 3 5 10 8 4 Total 25 Variable 5±2 5±2 5±2 5±2 5±2 Process So… Management Helps! Management puts in more work (Inventory) (rate of input RM) to give everyone something to do (Cost world approach)! Result: It takes longer and longer from time of release until final shipping. More and more delay!!!!!!!!!!! RM FG Process A B C D E ->X 30 7 9 5 8 6 TOC Steps to Continuous Improvement Step 1. Identify the system’s constraint. Step 2. Exploit the system’s constraint. Step 3. Subordinate everything else to the above decision. Step 4. Elevate the system’s constraint. Step 5. If a constraint is broken (that is, relieved or improved), go back to Step 1. But don’t allow inertia to become a constraint. Five Steps Applied to Flow Operations A B C D E 7 9 5 8 6 * WIP Total Step 3. Subordinate Everything Else (Rope) - feedback Step 4. Elevate the Constraint ($?->extra costs,depreciation) Step 5. If the Constraint Moves, Start Over Five Focusing Steps RM Step 1. Identify the Constraint (The Drum) - CRT FG Step 2. Exploit the Constraint (Buffer the Drum) – time reserve 12 12 12=2,5 dne práce pro úzké místo Rope= Lano-zpětná vazba FG Understanding Buffers A B C D E 7 9 5 8 6 RM •The “Buffer” is Time! (Buffer=nárazník je čas!) •In general, the buffer is the total time from work release until the work arrives at the constraint. •Contents of the buffer alters (see below) •If different items spend different time at the constraint, then number of items in the buffer changes •but Time in the buffer remains constant. WIP Total 12parts/5parts per day=2.5 Days We need more than one Buffer FG A B C D E 7 9 5 8 6 RM There is variability in the Constraint. To protect our delivery to our customer we need a finished goods buffer. Finished Goods Buffer There is variability in our suppliers. We need to protect ourselves from unreliable delivery. Raw Material Buffer Buffer Time is Constant-Predictable FG A B C D E 7 9 5 8 6 RM Finished Goods Buffer Constraint Buffer 2.5 Days Raw Material Buffer Finished Goods Buffer 1 Day Processing Lead Time is Constant Raw Material Buffer 2 Days=10/5 12 FG Buffer Management A B C D E 7 9 5 8 6 RM Constraint Buffer WIP Total 12/5=2.5 Days Time until Scheduled at Constraint 0 2.5 Days WO17 WO14 WO15 WO16 WO10 WO11 WO12 WO13 WO18 WO19 WO21 WO20 WO = Work Order A B C D E FG Problem Identification 7 9 5 8 6 RM Time until Scheduled at Constraint 0 2.5 Days WO10 WO20 WO12 WO13 WO21 WO15 WO16 WO17 WO18 WO19 Delayed Parts WO11 WO14 WO19 WO19 OK (Green) Watch WO14 (Yellow) Constraint schedule is in jeopardy! (Red Zone Hole) Additional Buffers * Constraint Buffer (as we discussed) •Protects the Constraint from running out of work * Finished Goods Buffer •Protects customer delivery from Constraint variation * Raw Material Buffer •Protects the Release of material from suppliers * Assembly Buffer •Facilitates speedy flow of products https://www.youtube.com/watch?v=8yehd2ZsKH0