The chapter contains a case study in which simulation was used to improve production planning in a semiconductor wafer manufacturing facility. Chapter 9, “Semiconductor Manufacturing Scheduling and Dispatching,” .. provides an overview of the state of the art in production scheduling of semiconductor wafer fabrication facilities.
A HISTORY OF PRODUCTION SCHEDULING
INTRODUCTION
FOREMEN RULE THE SHOP
In the late 19th century, manufacturing companies were concerned with maximizing the productivity of the factory's expensive equipment. Foremen ran their stores and coordinated all activities necessary for the limited number of products they were responsible for.
THE RISE OF FORMAL SYSTEMS
- The production control office
- Henry Gantt and his charts
- Loading, boards, and lines of balance: other tools
The planalog was a board (up to six feet wide) that hung on a wall. See Figure 1-1.) The plate had multiple rows into which gauges of various lengths (from 0.25 to 5 inches long) could be inserted. The vertical bars indicate, for each part, the number of units completed to date, and the thick line indicates the number.
FROM CPM TO MRP: COMPUTERS START SCHEDULING
- Pr oj ect scheduling
- Production scheduling
- Production planning
- The implementation challenge
- BETTER SCHEDULING ALGORITHMS
- Types of algorithms
- The role of representation
- ADVANCED SCHEDULING SYSTEMS
- Mathematical programming
- Other solution approaches
- It takes a system
- CONCLUSIONS
Early computerized production scheduling systems used input terminals, centralized computers (such as the IBM 1401), magnetic tape units, disk storage units, and remote printers (O'Brien, 1969). The problem in production planning is to determine which parts of the mine should be mined each month over the next five years.
McKay, K.N., and Wiers, V.C.S., 2005, Human Factors in Planning and Scheduling, in Handbook of Production Scheduling, Herrmann J.W., ed., Springer, New York. Newman, A., Martinez, M., and Kuchta, M., 2005, An overview of long-term and short-term production scheduling at LKAB's Kiruna mine, in Handbook of Production Scheduling, Herrmann J.W., ed.
THE HUMAN FACTOR IN PLANNING AND SCHEDULING
INTRODUCTION
This specific lack of adaptation is what we will call the human factor in the success or failure of the planning methodology. In this chapter we will review research conducted on the human factor in planning and scheduling.
SCHEDULING AND SEQUENCING
In unstable situations like this, sequencing is only part of the problem and the Theory of Scheduling 7^ Theory of Sequencing. When sequencing is only part of the problem and the human scheduler is expected to provide the remaining knowledge and skill, other issues may remain.
THE HUMAN ELEMENT 1 Introduction
- Recent empirical research on scheduling
- The decision level - cognitive scheduling models
- Issues relating to the use of formal decision processes
- Individual differences
In order to do this, a good understanding of the human scheduler was deemed necessary. The GEMS model (Generic Error Modeling System, Reason (1990)) is an adapted version of the decision theory of Rasmussen.
CONTEXT OF SCHEDULING IN PRACTICE 1 Introduction
- Organization perspective
- Task perspective
- Daily activities
At one of the factories studied, the information and types of information used by the scheduler in dealing with operationally feasible (and desirable) schedules were collected and analyzed. This supports the problem-solving view of the scheduler's role and the view of normal/exception information processing.
INTEGRATING SCHEDULING AND SEQUENCING
- A u t o n o m y a n d u n c e r t a i n t y .1 Shop types
- Smooth shop
- Social shop
- Stress shop
- Sociotechnical shop
- Complexity
- Transparency
We can relate the GEMS model presented in Section 0 to these features by equating routine—the GEMS concept—with formalization—. In a smooth workshop, there is little uncertainty in the detailed information or execution phases and consequently there is no need for human intervention and problem solving, i.e. recovery.
DESIGNING DECISION SUPPORT SYSTEMS 1 Design model
- Semantics and the scheduler's ontology
- Task support
In order for the system to be adopted quickly and to reduce the disruptive nature, it is possible for the decision support system to adopt the users' terminology and support their meta-objects. The menus and functions also change on the first of the month and are different if the system was not used on the first of the month and is now later in the month.
CONCLUSION
The flowshop system also alluded to earlier in this chapter has menus that change on Fridays (present different tasks and certain functions have improved processes). Second, the section on semantics and planner ontology discussed how planning support systems should speak the language of the planner. Finally, it was emphasized that decision support systems should support a planning task, which goes beyond offering a number of functions that are structured differently in the eyes of the planner than the day-to-day activities they are intended to support.
ACKNOWLEDGEMENTS
S., 2001, From anecdotes to theory: reviewing knowledge of human factors in planning and scheduling, in: Human performance in planning and scheduling, B.L. A., 1995a, Common sense realities in printed circuit board manufacturing planning and scheduling, International Journal of Manufacturing Research. S., 1996, A quantitative field study of the decision behavior of four shop floor programmers, Production Planning and Control.
ORGANIZATIONAL, SYSTEMS AND HUMAN ISSUES IN PRODUCTION PLANNING,
SCHEDULING AND CONTROL
THE GAP - MODEL ^DEVIANCE'
- Classical scheduling theory
- Hierarchical planning and control
The gap referred to here concerns the limitations in the applicability and relevance to practice of many of the theoretical models and algorithms. Outputs: The classical theory assumes that schedule generation is the main problem and, once generated, is the end of the scheduling problem. MRPII-type thinking is the control logic of the manufacturing planning and control modules of many of the leading ERP vendors and in that sense it can be said to be the dominant planning and control paradigm.
STUDIES OF PRACTICE
- A model of human scheduling practice in manufacturing
- Socio-technical principles in planning, scheduling and control
Much of the literature views the planning and scheduling of FMS as a purely technical problem. Maintenance tasks: tasks that must be performed to successfully meet the requirements of the job, e.g. The reality of the current system may deviate from formal procedures established some time in the past.
INTEGRATING ORGANIZATIONAL, SYSTEMS AND HUMAN PERSPECTIVES
- Knowledge management in PSC processes
- PROCHART ~ a PSC design methodology
It has also generated significant interest from business and industry because of the contribution it is seen to make to effective organizational decision-making (Choo explored knowledge management concepts in the context of PSC. Significant factors identified for knowledge management include the consistency of production and of the PSC process, whether knowledge dissemination is broad or focused and the decision timescales and timings relative to the planning cycle. Directly influencing knowledge practices can be difficult, but the characteristics of the PSC environment can be changed to support effective knowledge integration through reorganization.
IN CONCLUSION
Higgins, P.G., 2001, Architectural and interface aspects of planning decision support, in Human Performance in Planning and Design (eds MacCarthy, B.L., Wilson, J.R.), Taylor and Francis, London. MacCarthy, B.L., and Wilson, J.R., 2001a, eds., Human Performance in Planning and Design, Chapter 1, Taylor and Francis, London. MacCarthy, B.L., and Wilson, J.R., 2001b, eds., Human Performance in Planning and Scheduling, Chapter 20, Taylor and Francis, London.
DECISION-MAKING SYSTEMS IN PRODUCTION SCHEDULING
- THE IMPORTANCE OF DECISION-MAKING
- PRODUCTION SCHEDULING AS A DECISION- MAKING SYSTEM
- IMPROVEMENT METHODOLOGY
- REPRESENTING PRODUCTION SCHEDULING SYSTEMS
- Organization charts, flow charts, and IDEF
- Swimlanes
- EXAMPLES
- CAD/PAD production scheduling
- Conservatory assembly
A decision-making system's view of production planning does not eliminate the need for better planning decisions. Viewing production planning as a decision system leads to a systems-level approach to improving production planning. When changes occur during the week (to . status of equipment, hardware, or work orders), the production engineers, production controller, and foreman respond appropriately without changing the weekly schedule.
SUMMARY AND CONCLUSIONS
It is hoped that this material will help engineers, analysts and managers to improve their production scheduling systems by considering the structure and behavior of the system. This will encourage researchers to develop new representations and to use innovative methodologies to study and improve production scheduling. At what point in the process of improving production scheduling are such representations most appropriate.
SCHEDULING AND SIMULATION
- INTRODUCTION AND DEFINITIONS
- OVERALL SETTING
- SIMULATION TECHNIQUES WITHIN SCHEDULING
- Simulation-based schedule generation, refinement, and optimization
- Simulation used for parameter setting and test instance generation for scheduling approaches
- Simulation for emulation and evaluation of scheduling approaches
- CASE STUDY IN SEMICONDUCTOR MANU- FACTURING
- Manufacturing environment
- Shifting b o t t l e n e c k heuristic for c o m p l e x j o b s h o p s .1 Statement of the problem
- Software implementation of the shifting bottleneck heuristic
- Performance evaluation of the scheduling approach
- Design of experiments
- Computational results
Build an interface between the production planning approach, i.e. the production control system and process, and the simulation model, i.e. the base system and process. After solving the scheduling problem for a batch tool group, batch artificial nodes are added to the scheduling chart G. The predecessors of the batch artificial nodes are those nodes that represent the parties that make up the batch. Due dates were tight, i.e. the target cycle time was typically less than twice the raw processing time.
LULIX nil
CONCLUSIONS
34;Grand Challenges in Modeling and Simulation of Complex Manufacturing Systems." Simulation - Transactions of the Society for Modeling and Simulation International. 34;Simulation Framework for Performance Assessment of Shop Floor Control Systems." Simulation - Transactions of the Society for Modeling and Simulation International. 34;Using simulation-based scheduling to maximize demand fulfillment in a semiconductor assembly facility." In: Proceedings of the 2002 Winter Simulation Conference, E.
RESCHEDULING STRATEGIES, POLICIES, AND METHODS
L INTRODUCTION
RESCHEDULING BASICS
The biggest deviations or changes in the sequence occur when unexpected events disrupt the original schedule. Even if managers and supervisors do not explicitly update the schedule, schedule repair occurs when operators react to disruptions, delaying tasks, or performing tasks out of order. Rescheduling is the process of updating an existing production plan in response to disruptions or other changes.
RESCHEDULING FRAMEWORK
- Rescheduling environments
- Rescheduling strategies
- Rescheduling methods
Dynamic rescheduling environments have an infinite set of jobs (that is, jobs keep arriving over an infinite time horizon). At a minimum, schedule execution requires some rule or policy to reconcile the error in the schedule. Rescheduling may occur frequently in a dynamic rescheduling environment, or it may simply be a single revision of the schedule for a stochastic, static rescheduling environment.
WMM., WMMMM
RESCHEDULING STRATEGIES
4,1 Dynamic scheduling
Predictive-reactive scheduling
It is common for factories to use schedules that specify only in which week an order or operation must be completed. At the other extreme, some scheduling systems can generate very precise production schedules that specify the day, hour, and minute each operation should begin (and the time it should finish). 34; wrong" (wrong because there can be many small discrepancies), while schedules that are less precise make it easy to meet the schedule.
RESCHEDULING METHODS
- Generating robust schedules
- Repairing schedules
Otherwise, someone must make arrangements to fill the order and inform the person in charge of the change. On the other hand, a computer-based planning system that is closely integrated with the shop floor and production execution system is likely to have up-to-date information on the status of machines, operators, and jobs. Informal rescheduling is a good thing if it reflects the ability of shop floor personnel to meet production goals even when disruptions occur.
A PRACTICAL VIEW OF THE COMPLEXITY IN DEVELOPING MASTER PRODUCTION
SCHEDULES: FUNDAMENTALS, EXAMPLES, AND IMPLEMENTATION
FUNDAMENTALS OF MASTER PRODUCTION SCHEDULING
The MPS function is an essential part of the manufacturing management architecture and, as such, should be given high priority when developing an integrated manufacturing system (Higgins & Browne, 1992). The production master schedule also provides information to the sales function about what can be promised to customers and when delivery can be made. The MSHP is one of the modules part of the production planning and control structure.
A SYSTEM FOR MPS CREATION
- Main input parameters
- Main output parameters
- Item and resource tables
- The multi-objective function
- A generic MPS process
Standard lot size: The quantity to be produced must be a multiple of the standard lot size. Requirements met: Shows in absolute terms how much of the gross needs are met by the master plan. Service level: A percentage that indicates how much of the gross requirement (demand and orders) is fulfilled by the MPS.
ILLUSTRATING THE MPS PROCESS COMPLEXITY
One of the following sections mentions some techniques that can be used in a master production scheduling system - with the focus and examples of the use of two artificial intelligence techniques: genetic algorithms (GA) and simulated annealing (SA). Product D has more limitations as it can only be made at L2 and L3; while the other products can be made from any resource. Part of B's gross requirements can be deferred to the next time bucket, but in this illustration, however, backlog is not allowed.
ARTIFICIAL INTELLIGENCE TECHNIQUES FOR MPS PROCESS IMPLEMENTATION
- Linear programming
- Hill-climbing search
- Tabu search
- Genetic algorithms
- Simulated annealing
One of the main disadvantages of this method is the computer time during the search for the solution due to the combinatorial explosion that can occur (Tsang, 1995). After crossing over (shown in Figure 7-7), a mutation operation can occur on the chromosomes according to several probabilities. Cooling ends only when the material reaches the solidification point, which will correspond to the minimum energy state.
FINAL THOUGHTS
The right number of employees to be assigned to each work center (production cell or line) should also be decided wisely. Herrmann for his contribution to the author's PhD in production planning and for his invitation to be a part of this book. 34;Comparative study of simulated annealing, genetic algorithms, and tabu search for solving binary and extensive machine clustering problems.".
COORDINATION ISSUES IN SUPPLY CHAIN PLANNING AND SCHEDULING
THE MEDIUM TERM PLANNING PROCESS IN A SUPPLY CHAIN (SUPPLY NETWORK
PLANNING) 2.1 Overview
Dimensions of supply network planning
Due to the complexity of a global supply chain, the dimensions of a supply network planning process are typically very different from the dimensions of a production planning and planning process. Another dimension in which supply network planning differs from production planning is master data. Supply network planning can also use aggregated master data, such as product groups or resource groups.
Unconstrained and constrained networl^: planning
In the case of optimization algorithms, the supply network problem is modeled as a linear or a mixed integer program (see Miller, 2002; Kreipl and Pinedo, 2004). Ignoring lot sizes in supply network planning can of course have consequences for production planning and scheduling, where lot sizes are more important (see Section 4). A production planning and scheduling module takes the proposed solution from the supply network planning module and creates an executable production plan for the short term.
SHORT TERM PRODUCTION PLANNING AND SCHEDULING IN SUPPLY CHAINS
- Overview
- Production planning
Another important element of production planning implementation consists of flow time calculations using available resource hours and information related to the routing and duration of operations. Lot Size Calculation: The second step takes the net demand and calculates the planned order quantities based on the specified lot size rules for each product. BOM explosion: Assuming the procurement type of the actual product is in-house production, the BOM explosion occurs and the dependent material requirements are determined.
