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1、Load-oriented manufacturing control just-in-time production for job shops,Production Planning & Control 1994 Vol.5. Wolfgang Bechte Hannover consultant firm 1998/08/18 ,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),con
3、tent,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
4、 control,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 way At the same time determine Bottlenecks, short & mid-term capacity plann
5、ing Furnishing realistic due-date scheduling and capacity planning,2. Structure of load-oriented manufacturing control,Flow of orders for one single machine Illustrating events, a hierarchical controller levels, sections,Figure 1.Funnel model of job shop,Multi-level closed-loop control system Higher
6、 controller 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 Capacit
7、ies,Operation 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 regulating Input, Output, Inventory and Lead time 1) constant inventory - keep In/Output t
8、he same on 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,A
9、vg. Inventory,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, Inventory and Lead time load limit = Planned output * (P
10、lanned lead time + Planning period) Planning period,3. Basic concept in load-oriented manufacturing control 3.2 Principle of Load limiting and Load conversion,Adding Load,Remaining Load,Load limit,Planned Input,Actual Inventory,Planned lead time,Case A,case B,Today,Planning Period,Planned Inv. (Buff
11、er),Planned output(capacity),Figure4. Load limiting,.,In case that exceeding loads happens Load limiting reject or prefer orders or varies Required capacity = present load * planning period planned lead time + planning period,Rejected Load,Allowed load,Load limit,Exceeding load,Present Load,Planned
12、lead time,Required Buffer,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 capacities Four type of loads In case of B,D a statistical estimation is needed ; Load conversio
13、n factor depreciation factor = planned output / Load limit = planning period planned lead time + planning period Limiting and balance work in process by order release.,Planned Inv. (I),(D),Load limit,Planned lead time,Today,Planned Inv. (Buffer),Planned output(capacity),(D),Planned Release(I),Ideal
14、Released Curve,Full load,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 backward Selects periodically those of the planned orders Step1. Establish urgent orders Step2.
15、 Release wotrkable orders Time 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,Workable,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 entr
