Real-Time Production Scheduling in Job-Shops

Small and medium machining shops are often arranged as job-shops. In a job-shop the production is usually done in small batches, and the machines are arranged in functional units, or cells (milling cell, drilling cell, etc). Each part or product to manufacture needs to follow a sequence of operations (a route) to be performed in different machines.

A production schedule defines, for each part, (i) the assignment of operations to specific machines, (ii) the sequence of operations in each job, and (iii) the sequence in which each machine needs to process all the operations assigned to it.

Traditionally the production schedule is created manually for one week or even longer. This is because it takes a long time to check all the necessary information: sales orders, due dates, priorities, inventory, worker holidays etc. As with every manual job, there is ample chance for human error.

These schedules are static, meaning that they take no advantage from real time data available on the shop-floor, and therefore cannot react to disruption events like new priority orders or machines breakdowns, or simply adapt to the natural variance in run and setup times. They also are unable to offer any insight around the impact that those events will have in the future production.