Release Rules determine how Manufacturing Orders are released for scheduling during an Optimization and therefore supersede the Optimize Rules (which come into play when choosing between released MOs that are in queue).
Each Manufacturing Order is prevented from starting to schedule until it is “released”. APS can be configured to release Manufacturing Orders to be scheduled based on the following methodologies and scheduling techniques.
- Drum-Buffer-Rope: This is the Theory of Constraints method for scheduling and managing operations that have a consistent capacity-constrained resource. The DBR calculation determines each Manufacturing Order’s release date.
- JIT Release: JIT scheduling is a methodology that is central to many Lean manufacturers that aims to cut down on inventory drastically by having the exact quantity of materials released at precisely the right time to finish production as close to the need date as possible. The JIT release rule sets the Manufacturing Order Release Date to the lead Activity’s JIT Start Date minus the JIT Slack Days. The larger the JIT Slack Days the earlier the MO is allowed to start.
- JIT Release is sometimes compared to traditional “Backward Scheduling” since both approaches share the aim of scheduling work based on the Manufacturing Order’s Need Date to reduce the costs of producing early (such as inflated inventory or risk of order cancellation). JIT Release has two important advantages over backward scheduling: (1) It works better when setups are an issue and products with similar setup characteristics need to be run in series to reduce changeover time, and (2) it prevents a common problem with backward scheduling from occurring — the scheduling of less urgent work in front of more urgent work due to the mechanics of backward scheduling in a finite capacity model (more urgent work is scheduled and then the less urgent work can’t find the capacity at the right time and so it looks for early time slots such as in front of the more urgent work).
- JIT Release can also be used effectively in combination with JIT Compress. Greater Slack Days can be used during Optimize to pull in demand when there are large future capacity load peaks. Then JIT Compress will “slide” activities to later times, preserving sequencing, reducing early production, and still accommodating for the high future capacity loads.
- When using JIT scheduling to optimize, users have two options:
- JIT with Resource Headstart – The headstart span (the amount of time that a job is able to schedule before the JIT start date) is set on each individual resource. By default this is set to 4.29 weeks, and will need to be changed by accessing the resource options.
- JIT with Global Headstart – This enables a text box next to the drop down menu where users can set the number of headstart days that will apply to all resources.