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Documentation Index

Fetch the complete documentation index at: https://docs.firstresonance.io/llms.txt

Use this file to discover all available pages before exploring further.

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Overview

A substitute (also called an alternate) is an interchangeable part configured against a build requirement. When a substitute is approved on the mBOM, operators can scan it during install in place of the primary — and ION accepts it without flagging a deviation. Substitutes are how supply variation, second-source procurement, and minor design tolerances stay operational instead of becoming per-build paperwork.

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When to configure a substitute

Configure a substitute when:
  • Two or more part numbers are functionally interchangeable for this build requirement (same fit, same form, same function).
  • You source the part from multiple vendors with different part numbers per supplier.
  • The primary part has supply risk, and you want operators to fall back to a known-good alternate without filing a deviation.
Don’t configure a substitute when:
  • The alternate is a different revision of the same part. That’s a revision-interchangeability question, not a substitute. Use revision rules on the part record instead.
  • The alternate is “good enough” but not truly equivalent. That should be a per-build deviation with engineering review, not a blanket approval.

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Configuring a substitute

From the mBOM editor:
  1. Open the build requirement on the mBOM.
  2. Expand the Substitutes section.
  3. Click Add substitute.
  4. Pick the substitute part. Optionally pin to a specific revision.
  5. Save.
Substitutes can be added or removed without revising the mBOM as a whole — they’re metadata on the line. But significant substitution changes (e.g. flipping the primary) typically warrant a new mBOM revision.

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How substitutes behave during install

When an operator installs against a build requirement at run time:
  1. The aBOM Part Manager modal shows the primary part prominently.
  2. Below it, the configured substitutes are listed.
  3. The operator can scan or pick any of the listed parts (primary or substitute).
  4. ION validates the scan against the union of (primary, substitutes) and accepts the install.
  5. The aBOM line records what was actually installed — primary or substitute.
If the operator scans a part that’s neither the primary nor an approved substitute, ION rejects the scan. From there the path is either: (a) configure the unexpected part as a substitute and retry, (b) file an issue and document a deviation, or (c) source the correct part.

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Substitutes vs revision interchangeability

Two related-but-different concepts:
ConceptWhen to use
SubstituteDifferent part numbers that are functionally equivalent (e.g. FAST-M3-A and FAST-M3-B from two suppliers)
Revision interchangeabilitySame part number, different revisions (e.g. BRKT-001 Rev A and BRKT-001 Rev B) — configured on the part itself
ION treats these separately because they have different controls: substitutes need explicit per-line approval; revision interchangeability is set at the catalog level.

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mBOM Substitutes and aBOM installations

A substitute is a plan — “this is acceptable to install.” The aBOM records what was actually installed. The two together let you ask:
  • “How often is the primary used vs each substitute?” — aggregate over installations.
  • “Does any unit contain the substitute we just recalled?” — filter installations on installedPartInventory.partId.
This is why you don’t lose traceability when substitutes are used — the aBOM is precise about which part went in, even if the build requirement allowed several choices.

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Substitutes and reference designators

When a build requirement has both substitutes and reference designators (positional callouts), the operator must:
  1. Pick the position to install (e.g. R7).
  2. Scan a part — primary or substitute.
ION records the (position, installed part) pair. If you have eight build requirements with reference designators R1–R8 and any of them can take primary OR substitute, that’s eight installations, each potentially using a different part.

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Tips

  • Approve substitutes proactively, not reactively. When a supply chain disruption hits, you want substitutes already approved on the mBOM — not scrambling to add them mid-build.
  • Document the equivalence rationale. When you add a substitute, capture why it’s equivalent (same datasheet specs? same finish? same plating?) in the build requirement notes. Future engineers asking “why is this substitute approved?” will thank you.
  • Track substitute usage in analytics. If the substitute is being used 80% of the time, that’s a sign the primary should change. ION’s analytics can surface that pattern.