Intelligent Scheduling For A Tough Class of High-Mix, Low-Volume Production Systems
If an industry is making a variety of products in small quantities, we consider its manufacturing system as high-mix, low-volume (HMLV) production. A large variety of industries fall into the category of HMLV production. There is one subcategory of HMLV systems which I describe as order-driven HMLV production. It can also be termed as order-specific HMLV production. Usually, such systems are more complex than a single production line and found in job shops. There are different types of material flow in HMLV production as shown in the diagram below.
Features of High-Mix, Low-Volume Production
The features include:
- The quantities, process requirements and receiving times of orders are highly unpredictable
- Future demand for any type of product cannot be smoothened over time for production planning purpose
- Final goods inventory is not viable for a majority of products
- Unlike Toyota dealers, customers may not maintain inventories for ordered products so that the inventories provide more flexibility in manufacturer’s production plan
- Customers are more authoritative than Toyota dealers and very particular with specified due dates of individual orders
- A product is made only after an order for the product is received (make-to-order production)
- Every order comes with a specific lead time and the corresponding product must be made and delivered within that lead time
- The high known variation in process requirements of orders and stipulated order due dates jointly cause major fluctuations in workloads at work centers and consequently shifting bottlenecks
- It is not easy to increase capacity of any work center as much as required and whenever required for preventing bottleneck formations
- Production system may or may not be a production line of a set of parallel production lines
- Many orders may simultaneously progress through the system along the respective routings while competing for shared resources for meeting their due dates
- Production sequencing is mostly determined by order due dates.
Major fluctuations in workloads at work centers and the inability to increase capacity of any work center whenever required and as much as required make it difficult to predict progress of orders on shop floor and quote minimal achievable lead times for new orders. It is also difficult to predict shifting bottlenecks in production and perform capacity planning proactively. The high variation in process requirements of orders and the stipulated due dates of individual, diverse orders jointly make production planning more difficult. The shifting bottlenecks make pull system ineffective. It is not always easy and economical to transform such production into a single-constraint system with adequate subordination.
Intelligent Scheduling for Controlling and Managing HMLV production
Job shops engaged in such production know the practical value of scheduling in production control and management. Almost all of them use schedules for production control and management. They adopt various methods for generating production schedules. Although ERP software usually includes modules for production scheduling, most job shops still use Excel applications for scheduling purpose. This is despite the fact that Excel applications do not generate good schedules in general.
Scientific, intelligent scheduling is quite helpful to manage complex, order-driven, high-mix, low-volume production. Most job shops are small in size and revenue. With the help of software, scientific scheduling enables job shops to do their best in the existing situation without demanding system simplification or elusive capacity enhancements and it helps identify the most effective improvement opportunities by facilitating fast, reliable and extensive what-if analysis.
Powerful, scientific scheduling software are available to high-mix, low-volume production units at affordable price nowadays. One of them is our software, Schedlyzer.