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A reference designator pins a build requirement to a specific location in the assembly, such as R7 or U3. See Bills of materials overview for how designators sit on the line. When a build requirement has reference designators, operators install per designator rather than satisfying a count, and ION treats a requirement with no designators as quantity-only.

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Configuring reference designators

On the build requirement’s row in the mBOM card, with the version in Draft:
  1. Open the Reference Designators dropdown in the row.
  2. Type a designator and press Enter (or click Add). The input keeps focus so you can add them in sequence, for example R1, R2, through R12.
  3. To remove one, click the trash icon next to it in the dropdown.
Keep the number of designators aligned with the quantity, one per position. Each designator is unique within the build requirement. Two build requirements on the same assembly can both have an R7, but within one build requirement R7 appears once.

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How operators install with reference designators

At run time:
  1. The build requirement renders with one row per designator instead of a single quantity counter.
  2. For each designator, the operator selects (or scans) the part inventory to install at that position.
  3. ION records the (designator, installed part inventory) pair on the aBOM.
  4. The build requirement is satisfied when every designator has an installation.
Operators can install in any order, because designators don’t impose sequencing. If the assembly’s procedure has a specific order, that’s enforced at the procedure-step level.

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Reading the designators on a run step

On a run step, the Part installs panel in the right rail lists a build requirement’s designators under a Ref Designators heading, with a progress figure on the right:
  • n/m assigned shows how many of the m designators assigned to this run step have an installation.
  • n installed replaces that count when no designator is assigned to the run step, because there is nothing to measure against.
  • n/m assigned · k installed appears when the requirement holds both kinds. k counts the designators that reached the run step through an installation rather than an assignment.
A designator that reaches the run step through an installation rather than an assignment is marked not assigned to this step. Assign it to the run step to have it count toward the assigned progress.

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Assign a designator to a run step

Assigning a designator to a run step claims it for that step, so the operator working the step knows which positions belong to them. Assign designators in the Part Installs (aBOM) dialog:
  1. In the run, open the Part Installs (aBOM) dialog: on a run step, click View all in the Part installs panel of the right rail.
  2. Turn on Edit Mode.
  3. On the build requirement’s row, open the designator control. It reads Reference Designators until the requirement has one, then shows the first designator with a badge counting the rest.
  4. On the designator’s row, click Assign step and choose a run step. Search the list by typing.
Each run step in the list carries a marker for its current state: A designator marks one physical position, so it is held by one run step at a time. Assigning a designator that another run step already holds is rejected, and the message names the step holding it. The same rule applies when a redline is canceled: if the designator has since moved to another run step, ION refuses the cancel rather than restoring the designator onto two steps.
Moving a designator to a different run step isn’t available yet. Deleting the designator removes its run-step assignment along with it, and the delete confirmation names the step that loses the assignment.

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Substitutes and reference designators

Substitutes are configured at the build-requirement level, not per designator, so an approved substitute applies to every position the requirement covers. At install time, for each designator the operator can install the primary or any approved substitute, independently per position. So R1 can take the primary while R3 takes a substitute, and the aBOM records which part went into which position. Because substitutes can’t be scoped to individual designators, if R3 and R7 need different alternates, make them different build requirements.

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Designator naming conventions

ION doesn’t enforce a designator format, so it’s free text. Your downstream traceability is more useful if designators are consistent. Common patterns: If you use schematic or PCB designations from your design package, mirror them in ION. The alignment makes engineering and manufacturing handoffs easier.
Include reference designators when there’s a chance you’ll need positional traceability. Adding them later requires reinstalling every affected unit.
Match the engineering source of truth. If your PCB layout calls a position U3, the build requirement should call it U3. Renaming for clarity introduces drift.
Don’t use reference designators for sequential count tracking. A torque pattern that needs fastener 1, then fastener 2, then fastener 3 is a procedure-step concern, not a designator.