MxAPS can use secondary constraints to prevent operations from being scheduled when a required resource, such as tooling or labor, is not available.

For example, suppose you have four CNC mills, but only two tools are available for machining 2-inch diameter bar stock. Although all four machines may otherwise be available, MxAPS can use a secondary constraint so that no more than two operations requiring that tooling are scheduled at the same time.

The same concept can be used for labor. For example, if four machines are available but only three qualified operators are available during a shift, a labor secondary constraint can prevent all four machines from being scheduled simultaneously.

How secondary constraints work

A secondary constraint is represented by a Business Central item.

The item represents the resource being constrained, such as:

• a tool, fixture, die, or mold;
• a pool of machine operators; or
• another limited resource required while an operation is running.

On the Item Card, the MxAPS Scheduling FastTab controls how MxAPS treats the item when generating a schedule.

For a resource that must limit scheduling, set Constraint Type to Constrain.

An item with Constraint Type = Constrain cannot have its available quantity fall below the permitted level while MxAPS is scheduling. Items set to Track are tracked but can go negative, while items set to Ignore are not considered as secondary constraints.

Before configuring the constraint

The routing operation must also be configured to participate in MxAPS scheduling.

On the Routing Lines page, verify:

• Schedule Behavior is set to Include.
• Secondary Constraints is set to Schedule.

These are the default values for these fields, but they should be checked when troubleshooting a secondary constraint that does not appear to affect the schedule.

The Secondary Constraints setting determines whether MxAPS schedules secondary constraints for that operation.

Example: Limit four CNC mills to two available tools

Assume you have four CNC mills that can process an operation, but only two copies of a particular tool are available.

Create an item to represent that tooling, for example:

TOOL-2IN-BAR

The objective is for each operation requiring the tool to reserve one unit while it is using the tool. With two units available, a third operation requiring the tool cannot be scheduled concurrently.

1. Configure the tooling item

Open the Item Card for the item that represents the tool.

On the MxAPS Scheduling FastTab:

• Set Constraint Type to Constrain.
• Set the appropriate Fence Type.

The available Fence Type options are Global and Item.

With Global, the constraint uses the global fence used when generating the schedule. With Item, the item’s lead time is used for its fence.

Within the applicable fence, MxAPS restricts scheduling according to the available and incoming quantity of the constrained item. This prevents MxAPS from assuming that a shortage can simply be replenished immediately.

For a reusable tool whose physical quantity is fixed, make sure the fence configuration reflects the period over which that quantity must remain constrained. If necessary, use a fence that extends beyond the scheduling period so that MxAPS does not treat future replenishment as resolving the tooling shortage during the schedule.

A Shop Calendar Code normally does not need to be assigned to a tooling item. The field is intended primarily for secondary constraints such as labor where availability varies by time or shift.

2. Decide where the tooling requirement belongs

MxAPS supports secondary constraints at several levels. Choose the level that represents when the resource is actually required.

Routing Constraints

Use a Routing Constraint when the tool is required only for a particular routing operation.

From the Routing Lines page, select the operation and choose Routing Constraints.

This is normally the appropriate setup when, for example, the special tool is required only when an operation is machining 2-inch bar stock rather than every job that runs on the CNC mill.

The constraint defined on the routing operation is carried forward when the production order and its routing are created or calculated.

Machine Constraints

Use a Machine Constraint when the resource is required whenever a particular Work Center or Machine Center is scheduled.

From a Machine Center Card, choose Constraints to open the MxAPS Machine Constraints page.

For example, this is appropriate if a particular machine always requires one operator whenever it runs.

Do not use a Machine Constraint for a tool that is required only for selected products or operations, because a Machine Constraint applies whenever that machine or work center is scheduled.

Machine Alternate Constraints

Use a Machine Alternate Constraint when the secondary resource requirement depends on which alternate machine is selected for an operation.

For example, a particular machine may require a specific mold, fixture, or supporting resource that another machine capable of performing the same operation does not require.

3. Define the tooling requirement

For a reusable tool where one tool is needed for each operation, a typical constraint uses:

• Item No.: the item representing the tool.
• Logic: Fixed.
• Quantity Required: 1.
• From Segment and To Segment: the portions of the operation during which the resource is required.
• Release Segment: the point where the resource becomes available for use by another operation.

With Logic = Fixed, Quantity Required defines how many units of the constrained item are needed regardless of the production order quantity.

For example, if one physical tool is needed regardless of whether the operation produces 10 pieces or 1,000 pieces, use Fixed with Quantity Required = 1.

For reusable tooling, the Release Segment is important. It defines when MxAPS returns the tool to availability so another operation can use it. If the resource is to become available when its requirement ends, use the same segment as To Segment.

Do not leave the resource permanently consumed if the physical tool is reusable.

Expected result

If:

• four CNC mills are available;
• the constrained tooling item has two units available;
• each applicable operation requires one unit; and
• those operations have secondary constraints enabled;

then MxAPS can schedule at most two of those tool-requiring operations concurrently.

The other machines can still be scheduled for work that does not require that tooling.

Configuring labor as a secondary constraint

Labor uses the same secondary-constraint concept, but its availability can vary by shift.

For example:

• four CNC mills are available;
• each running mill requires one CNC operator;
• only three CNC operators are available on the first shift.

MxAPS can use a labor constraint so that at most three of those machines are scheduled concurrently during that shift.

1. Create an item to represent the labor pool

Create a Business Central item representing the group of employees, for example:

CNC-OPERATORS

This item represents scheduling capacity rather than physical inventory.

On the Item Card, under MxAPS Scheduling:

• Set Constraint Type to Constrain.
• Assign a Shop Calendar Code representing the availability of that labor pool.

The Shop Calendar Code field specifies the availability calendar for an item when it is used as a secondary constraint. This field is typically used for labor rather than tooling or material.

2. Define the number of available employees

Open the Shop Calendar Working Days for the labor calendar.

For each working period, populate Available Resources with the number of employees available during that period.

For example:

Starting Time	Ending Time	Available Resources
7:00 AM	3:00 PM	3
3:00 PM	11:00 PM	2

In this example, MxAPS has three units of the labor resource available during the first shift and two during the second.

The Available Resources field represents the quantity of resources available for that calendar during the defined time period.

3. Account for exceptions

If labor availability differs on a particular date, use MxAPS Shop Calendar Exceptions.

A calendar exception overrides the normal working-day entries for that date. The exception includes its own Starting Time, Ending Time, and Available Resources.

For example, if the normal Monday shift has four operators but only two will be available on a particular Monday, create an exception for that date with Available Resources = 2 for the applicable time period.

4. Add the labor requirement

If every time a particular machine runs it requires an operator, open the Machine Center Card and choose Constraints.

On MxAPS Machine Constraints, add the labor item.

For the common case where one employee is required whenever the machine is operating:

• Item No.: CNC-OPERATORS
• Logic: Fixed
• Quantity Required: 1

Configure From Segment, To Segment, and Release Segment according to the portion of the operation for which the employee is required.

With four machines each requiring one operator, and three units of CNC-OPERATORS available during a shift, MxAPS can schedule no more than three of those machines concurrently during that period.

If a machine requires two operators, set Quantity Required to 2.

Understanding the constraint fields

Item No.

Specifies the Business Central item representing the tool, operator, or other resource required for scheduling.

For Machine Constraints and Routing Constraints, this is typically an item that is not part of the production BOM because the resource is reusable rather than permanently consumed by production.

Resource Group Code

Items having the same Resource Group Code are required together.

Different Resource Group Codes represent alternate combinations of resources. When alternate groups exist, MxAPS chooses one group when scheduling the machine or operation.

For straightforward tooling and labor constraints, the default resource-group setup is normally sufficient unless alternate combinations of resources are required.

Logic

Controls how the required quantity is calculated.

Fixed means the same number of resource units is required regardless of production order quantity.

For example, a machine requiring one operator normally uses Fixed with Quantity Required = 1.

Quantity Pro-Rated is used when the amount of the constrained resource depends on the production order quantity.

Quantity Required

Used with Logic = Fixed.

It specifies the number of units of the constrained item required.

For example:

• one operator required: 1;
• two operators required: 2;
• one fixture required: 1.

Quantity Per

Used with Logic = Quantity Pro-Rated.

It defines the resource requirement relative to the production order quantity. It is not used when Logic = Fixed.

From Segment and To Segment

Define which portion of the scheduled operation requires the secondary resource.

The resource becomes unavailable to other operations when its requirement begins and remains unavailable through the configured ending segment.

Release Segment

Defines when the constrained item becomes available for another operation.

This is particularly important for reusable resources such as operators, tools, fixtures, molds, and dies.

If the resource should become available as soon as its requirement ends, set Release Segment to the same segment as To Segment.

If the constrained item is actually consumed by production rather than reused, leave the Release Segment blank.

Troubleshooting secondary constraints

If MxAPS continues scheduling more operations simultaneously than the available tooling or labor should permit, check the following:

1. Verify Schedule Behavior on the routing operation.
   It should be Include for an operation that MxAPS is expected to schedule.
2. Verify Secondary Constraints on the routing operation.
   It must be Schedule for MxAPS to schedule secondary-resource requirements for the operation.
3. Verify the item Constraint Type.
   The secondary-constraint item must be set to Constrain if availability is expected to prevent scheduling. Track allows the resource to go negative and therefore does not impose the same restriction.
4. Verify that the constraint is defined at the correct level.
   Use Routing Constraints for operation-specific requirements, Machine Constraints for resources required whenever the machine runs, and Machine Alternate Constraints for requirements associated with a particular machine alternative.
5. Verify Logic and Quantity Required.
   For one reusable tool or one operator per operation, Logic = Fixed and Quantity Required = 1 is the typical setup.
6. Verify the available resource quantity.
   For labor using a Shop Calendar, check Available Resources for the applicable working period or calendar exception.
7. Verify the resource is released.
   For reusable resources, make sure Release Segment returns the resource to availability at the appropriate point in the operation.
8. Verify the constraint fence.
   For inventory-based constraints, check whether the Fence Type and applicable Global or Item fence allow MxAPS to consider replenishment earlier than intended.
9. Regenerate the schedule after changing the configuration.

Reviewing secondary constraints in schedule results

After generating the schedule, use Resource Requirements in the schedule result to review the secondary-resource requirements created by MxAPS.

This can help confirm that the expected tooling or labor item was included as a requirement and determine when and how much of the resource MxAPS scheduled.

Related MxAPS documentation

For more information about configuring and troubleshooting secondary constraints, see:

• Machine Constraints
  Field-level reference for secondary constraints that apply whenever a Work Center or Machine Center is scheduled, including Item No., Logic, Quantity Required, From Segment, To Segment, and Release Segment.
• Machine Alternate Constraints
  Use when a secondary resource requirement applies only when an operation is scheduled on a particular alternate Work Center or Machine Center.
• Mx Item Card extends Item Card
  Reference for the MxAPS Scheduling fields on the Item Card, including Constraint Type, Fence Type, and Shop Calendar Code.
• Shop Calendar Exceptions
  Explains how to override normal Shop Calendar availability for specific dates. This is especially useful when an item represents labor and the number of available employees changes by date or shift.
• Resource Requirements
  Reference for reviewing the secondary-resource requirements generated in an MxAPS schedule. This can help verify that tooling or labor constraints are being included as expected.
• Production BOM Component Constraint Setup
  Covers setup for constrained production BOM components, including the routing and Item Card settings required for MxAPS to consider the component during scheduling.
• Understanding Scheduling Constraints in MxAPS
  Provides an overview of the different types of scheduling constraints available in MxAPS and when each type is appropriate.
• Understanding MxAPS Lead Time, Fence Type, and Material Availability
  Explains how Fence Type, lead time, and resource availability affect when MxAPS will allow constrained items to be replenished during scheduling.