The 11 Rules of Production Sequencing for Manufacturers

Production Sequencing for Manufacturers

Production sequencing is a detailed scheduling process that manufacturers use to order the production of purchase orders. By adhering to supply chain constraints, sequencing allows discrete manufacturers to meet deadlines and ensure that their shop floor operates with the maximum production efficiency.

The lean manufacturing system responsible for production sequencing is called production sequencing software and it is often bundled in an advanced planning and scheduling (APS) software package. This scheduling tool imports the data from enterprise resource planning (ERP), manufacturing execution systems (MES), and manufacturing resource planning systems (MRP systems). It then applies the 11 production sequencing rules, which we will discuss in detail, to generate the optimum production sequence.

A production sequence that adheres to all constraints is instrumental in helping manufacturing operations reduce downtime, control production costs, and boost overall profitability.

Why Is Production Sequencing So Important?

Production sequencing is crucial in manufacturing, as it is designed to eliminate much of the non-productive time associated with the process. Tasks such as preparation, configuration and clean-up are accelerated, optimizing productivity as well as overall yield.

Key Benefits of Production Sequencing

Manufacturers can realize the following benefits with the right approach to production sequencing:

Reliable Delivery Timeframes

Manufacturers are able to fully comply with due dates and can prioritize orders to meet tight timeframes.

Changeover Reductions

Unproductive changeovers between machines and workstations are significantly reduced.

Bottleneck Identification and Elimination

Bottlenecks in the manufacturing process can be swiftly identified using production data, and then these bottlenecks can be re-routed and eliminated during execution.

Better Throughput

With the right approach to production sequence, the rate of throughput is increased and products are completed more efficiently.

Sustainable Work in Progress (WIP) Inventory

Sequencing can prevent the inventory of WIP jobs from getting out of hand, giving teams the power to prioritize key jobs in order to push products through to completion.

Optimized Work Station and Machine Utilization

Multi-zone Sequencing gives manufacturers the power to ensure that workstations and equipment are utilized efficiently and effectively, reducing the levels ofunproductive time in the process.

11 Production Sequencing Rules

How does production sequencing make all of this possible? The action of sequencing makes sure that manufacturers engage with the complex rules that govern manufacturing scheduling. This in turn means the manufacturing business enjoys greater control over the entire process, prioritizing specific jobs as they optimize throughput, eliminating bottlenecks and realizing the other benefits listed above.

These eleven rules are:

11 production sequencing rules infographic

These eleven rules are:

1. FIFO - First In, First Out

Under FIFO, the first piece that is inputted into the process is also the first outputted from the process. Pieces are not held up at each individual phase of the manufacturing procedure and are instead moved through the phases in chronological order from first arrival onwards.

2. LIFO - Last In, First Out

LIFO is essentially the opposite of FIFO. Under this rule, the last piece to be inputted is the first to be outputted, which means all preceding pieces are held up in the production process to give priority to this last input. This method can be used to accelerate the manufacture of a specific product that has been delayed in the preparation phase, but it is rarely deployed.

3. SPT - Shortest Processing Time

Using the SPT rule means prioritizing pieces that can be produced and finished most quickly. Adopting this method allows products to progress through the manufacturing processin a more logical and streamlined manner, reducing queues and waiting times ahead of each phase.

4. LPT - Longest Processing Time

LPT is essentially the inverse of SPT, giving priority to products that will take the longest time to process. The aim of this rule is to reduce changeovers between different machines, increasing machine utilization in factories.

5. EDD - Earliest Due Date

This method gives the priority to products that are due to be completed soonest, in other words, the most urgent jobs. With this method, teams try to ensure that no jobs miss their individual deadlines.

6. LS - Least Slack

LS prioritizes items that have the least disparity between deadline date and expected processing time. When these items are completed, there will be very little time left over before the deadline, and so LS aims to complete these jobs first.

7. SIPT - Shortest Imminent Processing Time

SIPT is similar to SPT but prioritizes items with the shortest individual processing time.

8. LIPT - Longest Imminent Processing Time

LIPT is the inverse of SIPT and works in a similar way to LPT. Priority is afforded to items with the longest individual processing times.

9. LWQ - Least Work Next Queue

LWQ gives priority to machines, workstations or phases of production that have the smallest queue. The idea is that these queues can be eliminated soonest, minimizing delays on the next phases of manufacture.

10. CR - Critical Ratio

The Critical Ratio is defined by dividing the total remaining time until the deadline by the total remaining production time. Priority is given to items in the production cycle with the smallest critical ratio. CR brings together data from theEDD and SPT sequencing rules, combining these to provide a set of production priorities. Like DLS below, this is a dynamic method, and the Critical Ratio will change over time.

11. DLS - Dynamic Least Slack

DLS is another dynamic rule, like CR listed above. Under DLS, production is prioritized based on the difference between the deadline date and expected processing time - in the same way as LS. However, DLS adds dynamism to the calculation and will change over time as deadlines draw nearer. This makes it more difficult to implement than LS but also provides more accuracy during scheduling. The idea is to prevent delays and to ensure that no production job misses its deadlines.

Often many of these sequencing rules will be used at the same time. In this situation, it is important not just to assign a static hierarchy to these production sequencing constraints, but to consider all possible sequence combination and pick the best on through true optimization.

What Is the Difference Between Production Sequencing and Production Scheduling?

While it may not be intuitive, the two processes are closely aligned, and in fact, production sequencing is a subset of the production scheduling discipline.

Sequencing focuses on one particular area - the order and prioritization of production processes. In this sense, it fits neatly within the wider scope of production scheduling, which deals with the specifics of deadlines, timeframes and timestamps. This is why production scheduling is considered to be more complex than sequencing.

Production Sequencing Powered by Advanced Planning and Scheduling Software

AdvancedPlanning and Scheduling (APS) software is an important asset for manufacturers looking to leverage the benefits of production sequencing. In many ways, APS solutions are crucial for business owners, as they eliminate much of the uncertainty or potential for error, enabling manufacturing teams to fully engage with the eleven sequencing rules listed above.

These rules require reliable data. The APS system will gather, process and interpret this data, allowing teams to prioritize production deliverables with confidence.The system will also accelerate data processing, deploying advanced algorithms to quickly reach actionable insights.

However, not all APS systems are created equal. Many utilize heuristic sequencing algorithms that are relics of the past and too simplistic to consider all the constraints in modern, enterprise manufacturing environments.

Manufacturers can also utilize features such as ATP (available to promise) and CTP (capable to promise), delivering accurate due dates to stakeholders. This ensures that customers have a reliable idea of when the product will be delivered, and salespeople have accurate data to hand when they discuss deliverables with potential clients.

APS Data Sources

We've established that APS systems work with high-level data, but where does this data come from?

Enterprise Resource Planning (ERP) Solutions

The ERP solution integrates with the APS software, providing orders, bills of materials and routing data. A widely used ERP system in discrete manufacturing is SAP.

Material Requirements Planning (MRP) Solutions

MRP software delivers inventory data in real-time so that the APS system has an up-to-date snapshot of available materials and resources. This integration works both ways, and MRP software can re-order materials for replenishment when a need is identified within the APS system, ensuring that inventories remain stocked.

Manufacturing Execution System (MES)

The MES is the next link in the chain after the APS system. Drawing upon prioritization and sequencing outputs from the APS solution, the MES will monitor the execution of the manufacturing job in real-time. All aspects of production are tracked via the MES, including machinery and equipment performance, worker productivity, and work in progress (WIP) statuses.

What Type of Manufacturers Utilize Production Sequencing?

Production sequencing is best suited to discrete manufacturers - i.e. manufacturers that deliver specific products and items to their customers and clients. Other types of production - such as process manufacturing in which saleable commodities are not differentiated from one another - will not benefit from sequencing in the same way.

The following types of manufacturers commonly utilize production sequencing:

  • Automotive manufacturers
  • Industrial equipment manufacturers
  • High tech product manufacturers
  • Consumer electronics manufacturers
  • Aerospace manufacturers
  • Defense equipment manufacturers
  • Agricultural machinery manufacturers

Basically, any form of manufacture in which a discrete item is being produced - whether this is a complete product or simply a replacement part - will benefit from sequencing. If manufacturers are producing undifferentiated commodities such as processed grain or refined oil, sequencing rules are not so readilyapplicable.

Reach Out to the Team at Optessa and Leverage the Benefits of Production Sequencing in Manufacturing

Here at Optessa, we provide software solutions for manufacturers, such as the production planning and scheduling system that is so important in production sequencing. Reach out to our team to learn more about how these solutions will benefit your business.

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