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Time Constraints for Materials in Line Flows#

Available from SMT Template version 3.1.0 onwards

Overview#

The Time Constraints feature enables the definition and enforcement of timing rules between process steps in Line Flows.

It ensures that materials are processed within allowed time windows, protecting product quality and preventing the use of materials that may degrade due to delays between critical operations.

Electronics use case: limiting time between reflows

The most obvious use case for this feature for the context of SMT lines is the enforcement of the maximum time spent between the reflow of the top side of the panel and the reflow of the bottom side of the PCB panel. Minimizing the time spent between these two steps is critical to ensure that not too much moisture is absorbed by the PCB before the second reflow process, which could lead to PCB delamination and/or component faults.

Concept#

In SMT manufacturing, certain processes must occur within strict time limits to maintain material integrity and product quality.

For example:

  • Limiting time between solder paste application and reflow
  • Ensuring controlled delays between thermal processes
  • Preventing excessive exposure to environmental conditions

This feature enables manufacturers to define and enforce these constraints by:

  • Tracking when a material completes a specific operation
  • Monitoring elapsed time until a subsequent operation occurs
  • Enforcing limits (minimum or maximum) between these events

This ensures that:

  • Sensitive materials are processed within safe time windows
  • Quality risks (e.g., moisture absorption, oxidation) are minimized
  • Process discipline is maintained across production

Functional Behavior#

How It Works#

  • A time constraint is created when a material performs a defined operation at a source step
  • The constraint is validated when the material reaches a target step
  • The system checks whether the elapsed time is within the defined limits

Constraint Types#

  • Maximum Time

    • Limits how long a material can take between steps

  • Minimum Time

    • Enforces required waiting time between steps

Scope#

  • Applies to Line Flows
  • Applies to Topmost Materials (e.g., panels)
  • Supported operations:
    • TrackIn
    • TrackOut
    • Rework

System Configuration#

  • Defined via:

    • TimeConstraintsContext (Smart Table)

  • Requires:

    • Steps with Enable Time Constraints enabled

  • Optional:

    • Rules to trigger warnings or actions

Validation Outcome#

  • Within limits

    • Material proceeds normally

  • Limit exceeded

    • Operation is blocked
    • Optional rule (e.g., notification) can be triggered

Result#

  • Materials are prevented from exceeding critical time windows
  • Process discipline is enforced automatically
  • Risk of quality defects due to delays is reduced

Notes#

  • Common use case:

    • Controlling time between top-side and bottom-side reflow

  • Warning and limit rules can be used to:

    • Alert operators before violations
    • Enforce strict blocking when limits are exceeded

You can find more detailed information in the Time Constraints in Line Flows tutorial.