What are he factors that affect machine loading techniques during scheduling?
Machine loading is the job of deciding sequence of jobs to be processed on a production equipment or machine. In a typical machine shop there are multiple machine tools such as lathe, drill, milling machine and so on. This shop would typically process or manufacture many different components. Each of these components may be required to be processed on one or more of the machine tools. Also, at a time a number of pieces of a component, called lot quantity, may be manufactured. When a component is taken up for processing on a machine, all the pieces in the lot are processed one after another till the whole lot is processed and after this the complete lot is transferred to another machine for further processing, or moved out of shop-floor as finished components.
The way machine loading is done affects the performance of production work in terms of many key areas such as:
- The total time production lots remain on the shop floor.
- The total work-in-progress (wip) on the shop-floor.
- Lost machine capacity due to waiting for job lots to be processed. This may be measured separately for bottleneck machines and others.
- Meeting of committed delivery commitments.
Loading of the machine in a way that balances all such objectives is is a very complex decision. Many different machine scheduling techniques including sophisticated computer software are available and used in industry.
The choice of appropriate machine techniques will depend on many factors including the following.
- The number of machines to be loaded.
- The number of job lots to be processed during a given period such as a week.
- Number of machine used for each job lot
- Existence of machines with no or limited spare capacity that makes them bottleneck in the production process
- Relative weightages or priorities of the management among different machine loading objectives. These have been discussed above.
- Availability of people skilled in machine loading functions and techniques. For computerized machine loading, more important than individual skill is the availability of computer software.
Frequently, it becomes very difficult to choose an appropriate machine loading technique based on just logical analysis. Therefore, the best method of selecting a technique may be to do some simulation exercise with alternative techniques and decision rules and select a method that gives best results.