Tardiness Of Orders Research Articles

An operation scheme for make-to-order job-shop production systems

The purpose of this paper is to solve multi-job order release problem whose objective is to minimize the sum of mean shop floor flow times (SFFTs) of orders subject to due-date constraint. A heuristic algorithm is proposed for the problem by decomposing the load profile of the shop. The load profile is divided into two parts. One is for the planning orders (new orders and unreleased orders) and the other is for the current orders being processed. The advantage of decomposing the load profile is to reduce computational complexity in the estimation step of order completion time. A job dispatching rule is also suggested to synchronize part flows in the shop floor. The experimental results show that work-in-process (WIP) in both bottleneck stations and assembly station, the SFFT of orders, and the percentage of tardy orders are significantly reduced.

A Mixed-Integer Linear Programming Model for Short-Term Scheduling of Single-Stage Multiproduct Batch Plants with Parallel Lines

An important industrial problem is the short-term scheduling of batch multiproduct facilities where a wide range of products are manufactured in small amounts that must be satisfied at certain due dates during the given time horizon. This paper presents a new MILP mathematical formulation for the batch scheduling problem involving a single processing stage for every product to be delivered. Based on a continuous representation of the time domain and the concept of job predecessor and successor to effectively handle changeovers, the proposed model is able to determine the optimal allocation of jobs to lines/units, the sequence of jobs on every line/unit, and their starting and completion times so as to minimize one of the following problem objectives: the overall tardiness, the schedule makespan, or the number of tardy orders. Facilities having nonidentical parallel units/lines, sequence-dependent changeovers, finite release times for units and orders, and restrictions on the types of orders that can be manufactured in each equipment can easily be handled. To deal with real world single-stage scheduling problems, a successful strategy for expediting the problem solution that relies on the use of heuristics is also reported. These heuristics allow one to partially prune the set of feasible predecessors for each customer order, reducing the size of the MILP problem representation. Examples involving up to 20 orders and 4 units were successfully solved with an advanced branch-and-bound code requiring reasonable CPU time.

Setting thresholds for periodic order release

In job shop manufacturing environments, controlling the release of work orders can significantly improve system performance, especially when a few bottleneck resources limit shop throughput. A periodic order release policy measures the remaining workload of the bottlenecks and releases just enough work orders to bring the workload to specified threshold values. The thresholds should limit the work-in-process inventory but not delay order completion by starving the bottlenecks. In this paper we consider the problem of setting thresholds that minimize the expected cost of work-in-process inventory and order tardiness. For the single-bottleneck system, we propose a stochastic optimization approach that uses smoothed perturbation analysis to estimate the objective function gradient. Our computational experiments compare different methods that set good threshold values and show that periodic order release improves system performance.

Sequencing with setup time and order tardiness trade-offs

We consider the problem of scheduling customer orders on a single facility where each order consists of several jobs that can be clustered into several groups. When a facility is changed over to another group, a setup time associated with the new group is required. Two particular problems are considered in this context. One is to consider the total setup time and the number of tardy orders jointly. The other is to consider the total setup time and the maximum tardiness jointly. The total setup time in both problems represents a measure of internal efficiency, whereas the number of tardy orders and the maximum tardiness represent a measure of external efficiency. In any shop, the decision maker must consider the trade-offs between large setup costs associated with a more frequent changeover schedule versus the cost of tardy orders that might be induced by a less-frequent changeover schedule. In this article branch-and-bound algorithms are proposed to identify the set of nondominated schedules for the two bicriteria problems.

On-line scheduling in a multi-cell flexible manufacturing system

This paper deals with on-line scheduling in a multi-cell flexible manufacturing system, operating in a produce-to-order environment. A two level distributed production control system (DPCS) is developed and tested through a simulation study. The DPCS allows autonomous and simultaneous operation of each cell-controller, utilizing only local and short term information as well as simple heuristic rules. Simulation experiments show that the proposed DPCS achieves good results in throughput, tardiness of orders and WIP inventory level and that it is robust to machine and handling device failures.

Real-time production control of an FMS in a produce-to-order environment

Abstract This paper deals with real-time control of an FMS, operating in a produce-to-order environment, with machines subject to failure. A two-level production control system (PCS) is developed and examined. The proposed PCS incorporates three principles: no need for pre-planning procedures; separation between due-date and operational considerations; and full exploitation of process flexibility. In an extensive series of simulation experiments it was demonstrated that the proposed PCS leads to good results in both criteria: maximum throughput and minimum tardiness of orders. A comparison study between this PCS and one which is not based on separation between due-date and operational considerations, indicated the advantage of the former.

The effects of lot sizing and dispatching on customer service in an MRP environment

AbstractResults are presented of a simulation analysis of a hypothetical fabrication and assembly shop controlled by material requirements planning. The purpose of the study is to investigate the impact of lot sizing on the customer service performance of dispatching techniques in an MRP‐controlled assembly job shop operating near capacity. Six dispatching techniques are compared based on the tardiness of customer orders under four lot‐sizing techniques, two levels of demand, and two levels of nervousness. The study is conducted with a stable product mix, limited production capacity, and fixed routings. Random shifts in short‐term product mix cause short‐term bottlenecks, but one of the 15 work stations has less than 10% idle time and is the most commonly encountered bottleneck.The interaction of lot‐sizing and dispatching techniques was found to be a function of capacity utilization, a factor influenced by demand and nervousness level. Under low demand, earliest job due date yielded the best performance with regard to the percentage of tardy orders, average order tardiness, and maximum order tardiness. Under high demand, earliest job due date performed best with respect to average order tardiness and maximum order tardiness, but the best dispatching technique with respect to percentage of tardy orders depended on the lot‐sizing technique and the nervous‐ness level. Under high demand and high nervousness, effective capacity decreased and queues increased with economic order quantity, period order quantity, or least total cost. Economic order quantity generated the smallest batches. Period order quantity and least total cost generated extra set‐ups under high nervousness. Use of either of the three lot‐sizing techniques at high demand and high nervousness forced a choice between a dispatching technique that yields a low percentage of orders tardy (earliest modified operation due date) and one that generates low maximum order tardiness (earliest job due date). The Silver‐Meal heuristic consumed less effective capacity than the other lot‐sizing techniques. Using Silver‐Meal at high demand and nervousness, earliest job due date performed best with respect to each tardiness measure.The bottleneck causes the plant to behave like a single machine shop. Since large queues are maintained at the bottleneck, that is where the choice of dispatching technique is critical. Earliest due date minimizes the percentage of tardy orders. Earliest modified operation due date, operating like the shortest processing time rule, minimizes the percentage of tardy orders, but maximum tardiness is high. These results may stimulate new interest in single‐machine scheduling.The combination of least total cost and earliest job due produced the best overall performance at low demand. At high demand, Silver‐Meal and earliest job due date achieved the best performance.

Optimal Delivery Time Quotation and Order Sequencing

ABSTRACTThis paper examines the problem of quoting a common delivery time for several orders. The decision maker responsible for the quote must trade off the cost associated with a long delivery time against the cost of tardy orders that might be induced by a short delivery time. First, an aggregate cost model is investigated where it is assumed that some cost is incurred if the quoted delivery time exceeds a given threshold and the cost of order tardiness is dependent on the order. Both exact and heuristic solution procedures are proposed for this model. Finally, for the situation where the costs cannot be quantified, a bicriteria formulation of the problem is pursued and the set of nondominated solutions is identified.

An approximate method for the production scheduling of industrial batch processes with parallel units

In the first part of this paper, we present the results of a survey of production scheduling problems occurring in a broad range of industries, including the manufacture of polymers and aromas, and the processing of minerals. The surprising result of interviews with plant managers and production schedulers is the remarkable similarity in the process structures, product sequencing constraints, and scheduling objectives important to these diverse industries. Scheduling to reduce tardiness of customer orders was found to be the most important objective. A key requirement was the ability to handle realistic constraints on product sequencing and restrictions on the number of units which can make a given product. Thus, a class of industrial scheduling problems important to a broad range of process industries is defined. This is significant, since a great deal of research effort has, in the past, been devoted to problems with other scheduling objectives, without sequencing constraints and with identical units. In the second part, a solution method is presented which is shown to obtain optimal or near-optimal solutions for processes involvin stage of nonidentical parallel units. Sequence-dependent cleanouts, unit- and product-dependent processing times and product-to-unit assignment constraints are modeled. Test problems with up to 12 process units and up to 100 customer orders were solved, which is the typical size of industrial-scale problems. An evolutionary strategy was developed which generates an initial solution using heuristics, then systematically improves the solution until certain necessary conditions for optimality are satisfied. The method found optimal or near-optimal schedules for highly-constrained and difficult test problems with modest computational requirements. These results are significant since an effective solution method for single-stage industrial problems of this complexity has not heretofore been demonstrated.

Load-limited order release in job shop scheduling systems

This report examines the practice of using work load limits to control the release of orders to a job shop. Load limits function in the following general way. Whenever the inventory of work at a work center exceeds some critical value (its “load limit”), further release of orders which are routed to that work center are blocked from entering the shop. After the inventory is “worked off,” release of work to the shop gateways is again permitted. Load-limited order release is intuitively appealing because it appears to be a method for reducing system inventory and flow times. The practice of load limiting order release is becoming popularized by some of the recent production planning software products now on the market. A notable example is OPT. In this report, analytical results for an M/M/1 queueing model, along with existing simulation studies of multi-machine job shops are interpreted to form a theory about the effects of using load limits. The major finding here is the proposition that system flow time, inventory, and order tardiness all deteriorate to the extent that load limits introduce idle time into the schedule. Based on the arguments presented here, a very cautious approach toward the use of input control schemes for anywhere but gateway work centers would be advised. The conclusions drawn here are to a great extent arrived at by interpreting the research results of others, so there is a clear need for further research which tests these assertions in a more direct and controlled way.

Toward a better understanding of lead times in MRP systems

AbstractLead times in MRP systems represent the planned amount of time allowed for orders to flow through the manufacturing system. Setting lead times is a major issue in the operation of MRP systems. There exists, however, very little documentation on just how lead times should be set.This study examines the effects lead times have on MRP‐based manufacturing logistics systems. In particular, it examines the effects that lead times have on backlogs, order tardiness, and finished component inventories.A major finding is that changes to the level of planned lead times have both transient and steady state effects that may not necessarily operate in the same direction. A simple methodology is presented for setting the level of planned lead times when the criterion is finished component inventory.