Scheduling Overview

The Scheduler calculates the dates and times to work on a subset of existing orders--those manufacturing orders that you need to complete in the near future. You can run the schedule over any horizon: a shift, day, week, month, etc. However, you will usually run it for a one-day horizon, and you will usually run it each day. The Scheduler adjusts operation start and end times, suggests operation sequences, and reports changes in inventory levels. It also generates summary information (such as job performance) you can view in reports and graphs.

Data Flow

A job authorizes manufacturing of a quantity of an item for one level of a bill of material. The Scheduler constrains the schedule on end items only. It assumes that any component materials have already been allocated to the job and does not treat them as requirements. The item specifies a routing, which identifies the sequence of job operations that must be completed to manufacture the item.

Each operation specifies one or more resource groups. A resource group is a list of similar resources. A resource is an entity, such as crewperson, machine, or fixture, that can perform the operation. An operation is required to specify at least one resource group. During scheduling, the system selects one or more resources from the group, depending on each resource's availability and on rules you define, to perform the operation.

Work Centers capture all costing information from the scheduling activities and do not directly affect the schedule.

Forward Scheduling vs. Backward Scheduling

To achieve the best utilization of your resources, the Scheduler schedules jobs forward in time, starting at the current date/time and scheduling out until finishing the last operation of the last job. You cannot use the Scheduler to backward schedule. That is, the Scheduler cannot be configured to start from the last operation and work backward in time until reaching the first operation.

If you must backward schedule, you can use APS to schedule, populating the scheduling output forms and reports with the data generated from the planning run.

Event-based Scheduling

The Scheduler works by running a simulation of all "events" that happen during the process of a demand moving through its production steps. For example, the resource starting an operation is an event, followed by another event for completing the operation.

What Happens During Scheduling

For each demand being scheduled, the Scheduler places the quantity into a unit called a load. The load follows the item's routing. When a load arrives at an operation, it goes through these processing steps, depending on the resources, rules, and operation time you defined:

Process move time: The load moves from its previous operation (if any) to this operation.
Allocate resources to process the load: You define allocation rules to control how the Scheduler assigns resources. If the allocation rule can be satisfied, operation processing continues. If not, the Scheduler stops operation processing and the operation waits for the necessary resource to become available. It then attempts allocation each time a required/requested resource becomes available.
Process setup and run time: The Scheduler applies any setup and run hours to the load. If the operation uses Fixed Schedule Hours, the Scheduler uses the fixed value and ignores setup and run hours.
Free resources allocated to the load at this operation.
Process finish time: The Scheduler applies any post-operation finish hours to the load.
After operation processing is complete, the load moves to the next operation in the routing. The process continues until the last operation in the last job is reached.

Simultaneous Requests for the Same Resource

Loads of items compete for the use of resources. Each resource has its own request queue to hold outstanding requests from loads. During operation processing, if the Scheduler cannot allocate a member of a required resource group to a load, it enters a request in a queue for each resource group member. A Sequencing Rule, which you specify on the resource record, determines the sequence in which requests are sorted in the queue.

When a resource in that group is free, the Scheduler allocates it to the waiting load and removes that load's requests from the other member resources. If there are multiple requests in the resource's queue, the Scheduler uses the resource's Selection Rule to determine which request to allocate first. If the load requires multiple resources from the group, the Scheduler does not allocate any resources to the load until the required number of resources from that group is available.

Job Dates

The Scheduler uses a job's start date as an input value to its calculations. The Scheduler may update the job's start and end dates, but will only populate a blank start or end date if you are using the MRP planning mode. When you create jobs for subassemblies through copying a routing/BOM, the dates on those sub-jobs may be blank. If you are using APS, you must run APS Planning to populate the blank job dates. If you are using MRP, running the Scheduler populates the blank job dates.

Multiple jobs may have the same start date and time. The Job Release Rule, which you specify on the Shop Floor Control Parameters form before you run the Scheduler, controls the sequence in which the Scheduler releases these simultaneous jobs. The default job release rule releases jobs with the highest job priority values first.

Operation Setup Time

See the Operation Setup Time Overview for information on how the Scheduler considers setup time and how you can minimize setup time by sequencing similar items (for example, blue part to blue part, red part to red part, etc.).

Shifts and Holidays

By default, a resource is available for work 24 hours per day, seven days per week. Use these forms to refine the availability of your resources according to your facility's shifts and work schedules:

Shifts: Assigned to resources to make the resource available for specified time intervals.
Shift Exceptions: Assigned to resources to define periods of down time or overtime within a defined shift.
Holidays: Downtime for all resources that are assigned to any shift.

See the topic on Handling Shift Overrun for information about preventing an operation from being scheduled within a shift interval where it cannot finish.

Overlapping Operations

You can offset a series of operations to allow concurrent production.

See the topic on Defining Overlapping Operations for more information.

Partially Complete Operations

Sometimes, an operation is partially complete when you start a Scheduler run (that is, the operation was not complete at the end of the last Scheduler run). When you start the Scheduler run, the system should allocate the same resource to the operation when the operation processing resumes. If a job was already started and operations are incomplete, the Scheduler starts processing that in-process job before other jobs that haven't already started.

Output Analysis Methods

The Scheduler provides a set of output forms and reports that allow you to analyze the schedule output and determine the causes of bottlenecks, lateness, inconsistent utilization, etc.

See the topic on Analyzing Scheduler Output for more information.

Differences from the PROGRESS Version

The table below summarizes the differences between SyteLine SQL scheduling PROGRESS scheduling .


Objective	Tasks	SyteLine (SQL) Tasks
1. Create operations.	Set up shop calendar, holidays, work center, department, and machine master files. Identify work centers and link them to departments and cells. Also establish if there are multiple machines within a work center.	Set up scheduling shifts, holidays, resources, resource groups, departments, and work centers. Link scheduling shifts to resources and resources to resource groups. Link resource groups to work centers (optional).
1. Create operations.	In the operations for every manufactured item, identify either the work center or work center/machine needed for run times.	In the operations for every manufactured item, identify the resource groups and the number of resources from that group the operation needs. Specify run times and setup times (optional) and split size (optional).
2. Identify critical job dates for scheduling.	For each job, identify the starting or ending date for the job and then select the scheduling method to use. You can use forward or backward scheduling. You can consider move and queue time. You can also add additional time to the start or end of the job.	For each job, accept the starting and ending date from MRP or APS (the dates default when you firm the planned order) or enter a starting date of your own. If you manually create a job, and you are using APS, use Get ATP/CTP to plan the job and calculate dates (this only plans the job; you will still have to run the Scheduler). Backward scheduling is NOT possible. APS planning, however, plans backward from the due date. The system uses finite scheduling unless you mark the resource group as infinite. The Scheduler ignores Queue time. You can add additional start and finish times to the Move and Finish fields of the first and last operation.
3. Prioritize jobs	To establish job priorities, you can manually give each job a priority number or you can allow the system to auto-calculate the priority using the due date or using critical ratio. The priority determines the sequence in which the job will be scheduled. Highest priorities are negative numbers (the lower the number, the higher the priority).	You can establish job priorities in the same way as in PROGRESS. However, the new system does not calculate negative priority numbers--everything past due is set to priority 0. Additional methods for setting priorities are also available: At the job level, you can use job release rule options. At the operation level, you can use the sequence or selection rule options.
4. Schedule jobs.	You can schedule a specific job or you can perform global scheduling.	You schedule all jobs on the whole floor for a specified period of time. To plan a single job, use Get ATP/CTP (if you are using APS).
5. Troubleshoot scheduling problems.	Use the load displays to identify work centers that are over capacity.	Use the Scheduler output analysis forms to identify late jobs and causes.
6. Sequence and dispatch work.	Establish different sort criteria for all work centers. Assign the sort criteria to each work center. After scheduling, you can use the Resource Group Sequencing form to refine the schedule. Sequencing has three zones that you define by work center: A frozen zone (no changes allowed), a sequenceable zone (you can arrange jobs for economical reasons), and a viewable zone (you can see all jobs in the future and can move them in). You can then allow the system to sequence the operations within the work center based on your sort criteria or you can manually sequence them yourself.	The Scheduler automatically sequences your work based on your sequence and selection rules. You can also create custom sequence and selection rules. You can manually change the sequence of work for a resource group. The end result is a prioritized and sequenced schedule.