All manufacturing planning and scheduling systems can be broadly grouped into two kinds: static and dynamic. While static systems cannot deal with changing conditions prevalent on shop floors, dynamic systems are able to deal with them to varying degrees, depending on the system's inherent capabilities. Static scheduling systems can be deployed at manufacturing sites where orders are repetitive and there are minimal variations among the products and different quantities ordered from one planning period to another. Generally the manufacturing site is either small or the number of products being manufactured is limited. The list of customers is almost fixed and new product introductions are few.
Now compare this description of static systems with conditions prevalent at any manufacturing site. These days, manufacturing is really all about continuous and haphazard change, the ability to adapt and grow at a tremendous pace, having big and numerous manufacturing sites, introducing new quicker, and discontinuing many old products. Order quantities range from very big to very small, and there is a big list of customers, a big list of products, and the scope of operations is global etc. It is very clear that static scheduling systems no longer serve the purpose for today's manufacturing sector. Thus, in comes the need for dynamic manufacturing scheduling systems, which can take care of these dynamic and turbulent conditions.
Components of dynamic manufacturing scheduling systems
If you are buying a manufacturing scheduling system, make sure that you understand what kind of functionality it will provide. You should also make sure that it fulfills your needs. Knowing about the features of the system along with information about how it will help you, can lead you to make a correct decision. The following is a list of components and concepts of dynamic manufacturing scheduling systems.
Dynamic Order Handling
When orders arrive, they are put in a queue for processing. Depending on capacity, machine speeds, raw and finished material, and work in process (WIP) material inventories, the grouping and breaking of orders, the sequencing of order requirements, and their processing and dispatch dates can be calculated. Since all of these factors create changing conditions for order processing, the system will fail if the order processing capability is not dynamic. Add to this, the varying quantities of orders with different products ordered and you will have a good picture of what I mean.
Dynamic and Multilevel Bill of Materials
New products are introduced constantly and some old products are discontinued. For this reason, the bill of material (BOM) component should be dynamic and should be able to incorporate new products. BOM should also be multilevel so that WIP materials at different process stages can be represented conveniently and accurately.
Dynamic Process Definitions
Suppose a system is defined for only a fixed number of process steps and the manufacturing site incorporates a new process step. How will the system deal with it? Imagine that the manufacturing site does away with a process step and the installed system gets confused about how to deal with such a situation. A dynamic manufacturing scheduling system with dynamic process definition can deal with such situations. Such a system will be able to add or delete any process step and modify the relationship which exists among all process steps (hierarchical, parallel, upstream or downstream process steps).
Dynamic Material Routing
In some situations, material routings are fixed but in most cases, routings are very dynamic. Different machines inside a work center may be set to accept certain kinds of material at a given time. Then again, a work center in a process step may accept only a certain kind of material. Additionally, in some other cases, there could be different priorities for materials to go through different machines or work centers. To be able to schedule your machines to maximum capacity, your scheduling system should be flexible enough to take care of these factors. A dynamic material routing component can easily deal with all of these situations.
Dynamic Machine Speeds
In most cases, the speed of the machine depends, on material which is being processed. So a machine will have different speeds for different materials; therefore, whenever a new material or a new machine is introduced, new machine speeds have to be incorporated. In such conditions, a dynamic manufacturing scheduling system with the facility to incorporate new machine speeds is required..
Dynamic Product Attribute Definitions
In process industries, product attributes are one of the most difficult aspects to deal with. New products come with new attributes which will be incorporated in the system. A dynamic system with a dynamic product attribute definition capability will be able to handle new product attributes with ease. Basically products are grouped based on their attributes, like chemical composition, color, physical dimension, shape, surface finish etc. Order grouping, order sequencing, machine setup time are directly dependent on these product groups. Since product groups are based on product attributes, these product attributes influence order grouping, order sequencing, machine setup time etc. So product attribute definition and the way they are incorporated in the system plays a vital role in determining usefulness of the scheduling system.
Dynamic Machine Setup Time Definitions
Each kind of machine has different setup and changing times. For a particular material, there could also be many kinds of setup times for a machine, depending on what kind of material the machine previously processed. New material, a new machine, or a new process can introduce a new setup time which should be incorporated in the system. Apart from the ability to incorporate new setup times, the system should also be able to calculate cumulative and individual setup times.
Dynamic Optimization of Resources and Time
Optimization of resources and processing time at the shop floor is of the utmost importance for today's manufacturing sector, especially in the face of fierce competition, the global scale of operations, shrinking profit margins, and the high demand for very high service levels. Balancing optimization of resources and time against service levels, can be controlled if the manufacturing scheduling system is dynamic. It is also perfectly possible to increase both optimization of resources and service levels.
Dynamic Service Level Setting
Whereas the optimization of resources helps in cutting costs, service levels primarily determine customer satisfaction. A balance between the two can be achieved by setting their appropriate levels. Again different service levels can be set for individual orders, orders for specific customers, delivery dates, products etc. It is also possible to have high optimization as well as a high service level if orders are segregated and prioritized based on their profitability and business value. In this case, high priority orders are processed before or in place of low priority orders and their service levels are higher compared to low priority orders. At the same time, the optimization level of resources can be kept high.
Dynamic Stock Out Cost Setting
Stock out costs are the result of either insufficient raw or WIP materials, high service levels, or more order quantities than capacity. While shortages of raw and WIP materials can be avoided through better materials management, service levels can be adjusted to keep a low stock outs. Again a dynamic manufacturing scheduling system can keep a desired balance between service levels, and optimizes the level for resources and level of stock outs.
Fast Processing to Generate Plan on Fresh Data
Today, most of the manufacturing planning and scheduling systems take two hours or sometimes more than a day to generate a plan or schedule. By the time the plan is generated, it becomes outdated as the input data may have changed. Essentially this means your schedule is based on stale data and not on fresh and current data. Moreover, the user cannot generate plans on the same input data to create scenarios to choose the best plan for current needs. If the scheduling system is fast enough (say, within 5 to 10 minutes it can generate schedules) then these problems can be avoided.
Synchronized Planning and Execution
Planning and scheduling systems are generally separate from the execution system. In such a scenario, if execution deviates from planned activities, then the user has to reschedule manually. What if planning and execution are linked? In the execution part, an event system is defined and whenever there are deviations in timelines or if there are inventory violations, an event is generated. This event is read by the planning and scheduling part of the system and rescheduling is done automatically by the system. Of course, the user has already set the rules for rescheduling (how much deviation from timelines, inventory violations, business objectives like service levels, stock out costs, prioritizing orders from preferred customers etc.). Given this, such facilities can indeed be very useful.
Dynamic material requirement planning and master production scheduling is the result of all these components which work together to generate dynamic plans. Accurate calculations of finished, raw, and WIP material is possible only when all these components are defined properly and accurately. The same is true for processing, setup, idle, and outsourced material lead time calculations.
A dynamic manufacturing scheduling system not only incorporates these components, it also gives the user a system which can deal with a changing and dynamic situation at the shop floor efficiently and effortlessly. Because of the capability of these systems to incorporate changes easily and dynamically, their plans and schedules tend to be accurate. These systems also last long. Since they are flexible and can incorporate varied kinds of orders, new processes, machines, materials, attributes etc., they are adaptable to changing business needs.
Copyright @ 2004-2005 Ashfaque Ahmed
About the author
Ashfaque Ahmed is a seasoned consultant and business analyst in the areas of advance planning and scheduling in SCM. He has worked with many big to medium sized clients in retail, distribution and manufacturing industries. Some of these industries include automotive, CPG, pharmaceutical, food, textile, steel, packaging materials etc. He holds a bachelor's degree in engineering and an MBA in Information Systems.
Web page: http://www.geocities.com/ahmedashfaque2002