1、Load-oriented manufacturing control just-in-time production for job shops,Production Planning & Control 1994 Vol.5. Wolfgang Bechte Hannover consultant firm1998/08/18 ,Introduction,A technique for job shops supporting the JIT concept - Using load-oriented order release, entry (Bechte, Kettner 1980)
2、- Manufacturing control system is designed by Krautzig. - Implemented in many factories (Wiendahl, Bechte 19871991)Basic principles & technique for Load-oriented manufacturing control Detailed computational procedure refer to more theoretical publication written by Wiendahl(1993), Bechte(1988),conte
3、nt,1. Objectives of load-oriented manufacturing control 2.Structure of load-oriented manufacturing control 3. Basic concept in load-oriented manufacturing control 4.Overview of a load-oriented manufacturing control system 5.Example of the control system,1. Objectives of load-oriented manufacturing c
4、ontrol,Reducing lead-time and WIP . Keeping actual lead-time on stable lowest possible level. - Permanently In/Out put, inventory and average lead time of W/C are monitored and compared with their planned values in dynamic wayAt the same time determine Bottlenecks, short & mid-term capacity planning
5、Furnishing realistic due-date scheduling and capacity planning,2. Structure of load-oriented manufacturing control,Flow of orders for one single machineIllustrating events, a hierarchicalcontroller levels, sections,Figure 1.Funnel model of job shop,Multi-level closed-loop control systemHigher contro
6、ller level depends on the performance of the lower one.,Company,DISPOSITION,Job Shop,Machine,Sales,Due Date,Lead time,Utilization,Mfg.,Assembly,Receiving,Shipping,Supplier,Customer,Disturbances,Prod Schedule Long Term Capacities,Order Entry Mid term Capacities,Order release Short term Capacities,Ope
7、ration Sequences Capacities Loading,Figure2. Multilevel closed-loop control system,.,3. Basic concept in load-oriented manufacturing control 3.1 Basic relationship at a Work center,Four simple rules for regulatingInput, Output, Inventory and Lead time1) constant inventory- keep In/Output the same on
8、 a avg. 2) changing inventory- change input 3) Average lead time- adjust In/Out ratio 4) Individual lead time to be even- apply FIFO rule while dispatching Avg.lead time = Avg. Inv.Avg. Output,Queuing orders,Avg. Output,Avg. Input,Avg. Inventory,Input,Initial Inventory,Avg. Lead time,Avg. Inventory,
9、Output curve,Input curve,Output,Final Inventory,Control Period,Load Hours,Time days,Completed Orders,Arriving Orders,Figure 3. Basic relationship and throughput diagram,Basic relationship at work center to plan the Input, Output, Inventoryand Lead timeload limit = Planned output * (Planned lead time
10、 + Planning period)Planning period,3. Basic concept in load-oriented manufacturing control 3.2 Principle of Load limiting and Load conversion,AddingLoad,Remaining Load,Load limit,Planned Input,Actual Inventory,Planned lead time,Case A,case B,Today,Planning Period,Planned Inv. (Buffer),Planned output
11、(capacity),Figure4. Load limiting,.,In case that exceeding loads happens Load limiting reject or prefer ordersor variesRequired capacity = present load *planning period planned lead time + planning period,Rejected Load,Allowed load,Load limit,Exceeding load,Present Load,Planned lead time,Required Bu
12、ffer,Required capacity,Figure5. Short-term capacity planning using the load limit,Required Input Curve,Required output curve,.,Order release should consider the work center loads and capacitiesFour type of loadsIn case of B,D a statistical estimation is needed ; Load conversion factordepreciation fa
13、ctor = planned output / Load limit = planning period planned lead time + planning period Limiting and balance work in process by order release.,PlannedInv. (I),(D),Load limit,Planned lead time,Today,Planned Inv. (Buffer),Planned output(capacity),(D),Planned Release(I),Ideal Released Curve,Full load,
14、Converted Load,Figure6. Derivation of conversion using the load limit,A considering the available capacities of a short-term planning periods(12Week)Planned orders were scheduled backwardSelects periodically those of the planned ordersStep1. Establish urgent orders Step2. Release wotrkable orders Ti
15、me limit,3. Basic concept in load-oriented manufacturing control 3.3 Technique of load-oriented order release,.,If capacities is needed Load-oriented release require appreciate decision,c,b,a,a,c,a,b,b,a,c,Planning period,Time limit,today,Time Days,Due,Over due,Future,Non-Urgent,Order 4,3,1,2,Workab
16、le,Workable,Unworkable,Omissible,A,B,C,Work centers,Load Hours,Load limit,Released Load,Remaining Load,Figure 7. Steps of Load-oriented order release,3. Basic concept in load-oriented manufacturing control 3.4 Technique of load-oriented order entry,The ideas of Load-oriented order entry is to avoid
17、overloaded weeksChecks the scheduled operation dates against available capacities for a midterm planning horizon (ex 12 weeks) Realistic due dates are offered and the expected bottlenecks are indicated.Initiation capacity changes in advance if possibleOverload weeks Free date,.,.,Cumulative Load,Cum
18、ulative Capacity,Backlog,OverloadWeeks,Underload weeks,Planning horizon,Today,Time week,Free Date,Overload Portion 83%,Total Load 100%,Load hour,Figure 8. Cumulative load and capacity of a work center,.,.C is a critical work center,A,B,C,D,E,A,B,C,D,E,Overload Weeks,Today,Time week,Work center,A,B,C
19、,D,E,Free Date,Order Lead Time,Operation Lead Time,Realistic Release Date,Realistic Delivery Date,Planning Horizon,Figure 9. Establishing a realistic delivery date of an order,4.Overview of a load-oriented manufacturing control system,1. Routing data 2. Order data 3. Item data 4. Shop calendar 5. Ca
20、pacity data 6. Transaction data 7. Control data: detailed tables for w/c and free definable group,.,.,Shop Calendar,Capacity Data,Planning Data,Transaction Data,Item Data,Order Data,Routeing Data,PROGRAM Transaction Data,PROGRAM Control Data,PROGRAM Shop Calendar,Program Graphs Reports,PROGRAM Opera
21、tion Sequencing,PROGRAM Order Release,PROGRAM Order Entry,DIALOG Capacities,DIALOG Operation Complete,DIALOG Order Release,DIALOG Order Entry,Capacities Entries,Capacities Release,Capacities Sequences,Graphs Reports,Control Data,CONTROL SYSTEM(PC),BASIC SYSTEM(HOST),PLANNING SYSTEM(PC),Figure 10. Lo
22、ad-oriented manufacturing control system showing the data flow,5.Example of the control system,1. The method of basic throughput diagrams is extended (Figure 1 with diagrams) 2. Operation Throughput Element3. Planned and actual average lead time are computed for each inventory as well as average due
23、-date dev. For release, input, output and delivery,Entry,Release,Input,Output,Delivery,Disposition,Indirect,Direct,Downstream,Upstream,Open,Cycle,Total lead time,Wait after operation,Transport,Wait before operation,Setup,Run,Interoperation time,Process time,Direct Load time,.,4. Pump-building factor
24、ycharacteristics products 9000 pumps Manufactured parts 26000 different items Manpower(Job shop) 180 persons Work centers 130 (mainly 2 shifts) Orders 350 per week Operations 4,5 per order (Max 20) Run times 3,7 per operation Lot sizes 30 per order(1-1000) Factory began to work with the new system i
25、n 1987Improvement (compared 1991 with 1987)Inventory was twice as high in 1987 Most delivery higher than in 1987 Cycle lead time(release delivery)were cut from almost 8weeks to 5weeks Due-date deviations 4.5 to 1 week (lateness) Total lead time(entrydelivery) 14weeks to 9 weeks,Conclusion,Load-oriented manufacturing control system enables the factory 1. Reducing lead time and inventories2. Keeping actual lead time on a planned level3. Meeting the planned due dates4. Maintain an appropriate work-center utilization results in safer scheduling foundation for JIT production,
