Process of Production planning and Control (PPC) Routing, Scheduling, Loading, Just-in-time (JIT)
Procedures for Production Planning
(v) Follow-up or checking the progress
For planning of productive operations in detail, the planning department will receive full information from management about the quantity to be produced and the dates when delivery has been promised to customers. The planning department will also get the necessary engineering and drawing specifications from the engineering department.
Routing involves the determination of the path that work shall follow and the order in which various operations will be carried out. The objective of routing is to
find out the best and the cheapest sequence of operations. While preparing the route card, it must be kept in mind that machines in the plant are operated at their full capacity; and manpower and other facilities are best utilized.
Scheduling is the determination of the time that should be required to perform each operation and also the time necessary to perform the entire series, as routed, making allowance for factors concerned. It involves the preparation of a time-table, indicating the total time needed for the manufacture of a product as also the time expected to be spent at each machine and process.
In preparing schedules, the persons concerned will have to take into consideration the various types of orders on hand and the dates by which their completion has been promised. Some orders may be such as will require over-time work; because completion is not possible according to the delivery dates set for them, in the regular course of production.
Loading involves assigning jobs to work centers and to various machines in the work centers. If a job can be processed on only one machine, no difficulty is presented. However, if a job can be loaded on multiple work centers or machines, and there are multiple jobs to process, the assignment process becomes more complicated. The scheduler needs some way to assign jobs to the centers in such a way that processing and setups are minimized along with idle time and throughput time.
Two approaches are used for loading work centers: infinite loading and finite loading. With infinite loading jobs are assigned to work centers without regard for capacity of the work center. Priority rules are appropriate for use under the infinite loading approach. Jobs are loaded at work centers according to the chosen priority rule. This is known as vertical loading.
Finite loading projects the actual start and stop times of each job at each work center. Finite loading considers the capacity of each work center and compares the processing time so that process time does not exceed capacity. With finite loading the scheduler loads the job that has the highest priority on all work centers it will require. Then the job with the next highest priority is loaded on all required work centers, and so on. This process is referred to as horizontal loading. The scheduler using finite loading can then project the number of hours each work center will operate. A drawback of horizontal loading is that jobs may be kept waiting at a work center, even though the work center is idle. This happens when a higher priority job is expected to arrive shortly. The work center is kept idle so that it will be ready to process the higher priority job as soon as it arrives. With vertical loading the work center would be fully loaded. Of course, this would mean that a higher priority job would then have to wait to be processed since the work center was already busy. The scheduler will have to weigh the relative costs of keeping higher priority jobs waiting, the cost of idle work centers, the number of jobs and work centers, and the potential for disruptions, new jobs and cancellations.
Dispatching literally means sending something towards a particular destination. Here, it means taking all such steps, as are necessary to implement the programme of production chalked out as per routing and scheduling steps.
In particular, dispatching refers to:
(i) Procurement of necessary tools, jigs and fixtures etc.; before they are actually required by the workmen.
(ii) Giving workers the necessary work orders, instructions, drawings etc. for initiating the work.
- Follow-Up (or Checking the Progress)
Follow-up is the control aspect of production planning and control. It involves taking steps to check up whether work proceeds according to plans and how far there are variances from standards; and also taking necessary corrective steps to set things in order.
Inspection is the quality control aspect of production planning and control. It ensures that goods produced are of the right quality. The inspectors may inspect materials, semi-finished and finished products either at the work bench or in special laboratories or testing rooms.
To ensure maintenance of high standards of quality, a programme of SQC (Statistical Quality Control) may be fused with a system of production planning and control.
- Just-In-Time (JIT)
Just-In-Time (JIT) Manufacturing is a philosophy rather than a technique. By eliminating all waste and seeking continuous improvement, it aims at creating manufacturing system that is response to the market needs.
The phase just in time is used to because this system operates with low WIP (Work-In-Process) inventory and often with very low finished goods inventory. Products are assembled just before they are sold, subassemblies are made just before they are assembled and components are made and fabricated just before subassemblies are made. This leads to lower WIP and reduced lead times. To achieve this organizations have to be excellent in other areas e.g. quality.
According to Voss, JIT is viewed as a “Production methodology which aims to improve overall productivity through elimination of waste and which leads to improved quality”.
JIT in Production and Operation Management
JIT provides an efficient production in an organization and delivery of only the necessary parts in the right quantity, at the right time and place while using the minimum facilities”.
Benefits of JIT
The most significant benefit is to improve the responsiveness of the firm to the changes in the market place thus providing an advantage in competition. Following are the benefits of JIT:
(i) Product cost: is greatly reduced due to reduction of manufacturing cycle time, reduction of waste and inventories and elimination of non-value added operation.
(ii) Quality: is improved because of continuous quality improvement programs.
(iii) Design: Due to fast response to engineering change, alternative designs can be quickly brought on the shop floor.
(iv) Productivity improvement.
(v) Higher production system flexibility.
(vi) Administrative and ease and simplicity.