EFA-Optimal Production Planning and Scheduling Software

Makespan - Production Planning & Scheduling Solutions Ltd.

“EFA” a Production Scheduling Algorithm and Manufacturing Software

EFA, Evenly Feeding Algorithm is an Advanced Planning and Scheduling Software (APS) which allows manufacturers to effectively manage an important phase of the Supply Chain. EFA is designed for factories producing a variety of products, mainly Job shops, Flow shops and assembly lines. It is based on a unique algorithm designed to optimize production, reduce the total lead-time (makespan) and maximize throughput and profit. This is done by efficient utilization of the plant’s resources.

The Advantages of APS Systems

APS – Advanced Planning and Scheduling Systems, have two main advantages. The first, is their ability to generate feasible plans. Together with an effective Production Control System and reliable data, the APS system enables the manufacturer to commit and respect, agreed delivery dates. It also enables the planner to improve control on raw materials and work in process inventory (WIP). This feature is common to most APS systems. The second, is their ability to utilize the plant’s resources efficiently and to optimize production. This feature is what makes the difference between one APS system and another one.

Note: any new system which includes a production control element may improve the plant's efficiency, mainly in factories which have a low production level control. This is because the system forces the factory to work in an organized way based on reliable data. The efficiency received by optimizing production comes in addition to the one received by well organized work.

The difficulties of optimizing production and its influence on plant's profit are described below.

The Scheduling Challenge

Optimizing production involving sequencing jobs is highly problematic. The problem is known as "NP HARD", meaning - "Non Polynomial Hard" problem, or in other words a problem which has no mathematical solution. The number of sequences that could be created out of M jobs, M=M1+M2 (see the shop floor schematic diagram) is the factorial of M or M! (For example the number of sequences that could be created out of 20 different jobs is approx. 2*10¹⁸ and out of 25 jobs is approx. 1.5*10²⁵). Each sequence could result in another total lead time. The sequencing effect on the total lead time can be seen in a simple example.. The difference between the shortest total lead time and the longest, could be very high. In our Casting Plant example the total lead time of three sequences are 152, 195 and 218 hours respectively. The only theoretical way to find the optimal sequence is to calculate the total lead time in every sequence and select the shortest one, but the huge number of sequences (for let us say M greater than 15 jobs) is beyond the scope of capability of computers or even super computers to calculate in a reasonable time. However for practical purposes, a near optimal solution can be generated by an effective heuristic algorithm.

Finding the optimal sequence is the first and major step to optimize production, the next step is to decide and allocate the process machines for each job in every work center.

The Correlation of the Plant’s Profit to Optimal Schedule

Shortening lead times decreases manufacturing and WIP expenses, in addition it enables the planner to increase the throughput, and accept more customer orders in a given period. Sophisticated scheduling could increase the throughput up to 40% as compared to poor scheduling and up to 20% as compared to reasonable scheduling. The extra throughput, with almost no additional cost (except raw materials); and the reduction of work in process inventory (WIP) will considerably affect the plant’s profit.

In order to see the correlation between optimal schedule and plant’s profit let's assume an increasing throughput of 15% in a factory with the following

#	Sales (K$)	*Raw Materials (k$)*	*Other Expenses (k$)*	*Profit (k$)*	*Increasing Profit (%)*
1	*1000*	400	400	200	-
2	*1150*	460	400	290	45

monthly profit/loss data: Sales= $1,000,000, Raw materials expenses= $400,000, other expenses= $400,000, Profit= $200,000. The table at the right shows that the increase of profit is 45%. The increasing profit is unique to each factory and depends mainly on the raw materials part of the sales.

Although the correlation between optimal schedule and plant’s profit varies from one plant to another. the benefit/cost of software based on sophisticated algorithm that could eliminate waste, reduce the total lead time and increase profit could be much higher than any other improvement process. Some managers are not aware of it. This is because the logic behind it is not straightforward and the influence of optimal sequence, on the total lead time and profit is not self-explanatory.

About EFA Software

The EFA software is based on the EFA algorithm; its advantage on the Bottleneck approach (TOC) and JIT is described in a separate article, please link to "EFA Algorithm". In addition our system enables the planner to run two other planning procedures:

- EDD, Earliest Due Date. (Actually this well known procedure was written in order to have a reference enabling the evaluation of the performance of EFA.)

- SLP, Self Planning Procedure, scheduling via an interactive mode, using a “what if” approach, beginning with schedules either obtained from EFA or EDD or generated through SLP.

Implementing our system doesn't require any special arrangements or changes on the shop floor. Operating it is very simple, especially the EFA and EDD procedures, both run automatically; in addition the planner can intervene almost at every stage of the scheduling process.

It is recommended the EFA be operated together with systems you might already have like ERP, MRP etc. EFA will obtain the relevant input data from your system data base and operate as the planning brain. If such a system does not exist, the relevant data could be created manually using spreadsheet (EXCEL) or any text editor.
EFA runs on a PC under any version of Windows.

For more details on our scheduling algorithm and software please link to "Sequencing Effect", "why EFA" and "EFA Algorithm". To obtain an impression on the implementation of our software please link to the examples of planning production in a "Casting Plant" and "PCB Plant".