Bills of materials

A bill of materials (BOM) lists what goes into one revision of an assembly. Each line names a child part and how many of it you need. You edit it on the BOM tab in Parts & BOMs.

Lines

A line has three things:

• The child part.
• A quantity. Quantities are decimal strings, such as "2" or "0.25", so metres and grams work without rounding errors. A quantity must be greater than zero.
• A way to choose the child revision.

A BOM holds at most one line per child part. To use more of a part, change the quantity of its line.

You list a revision’s own lines with listBOMLines. You add, change and remove lines with addBOMLine, updateBOMLine and deleteBOMLine. You can only edit the lines of a DRAFT revision. See Parts and revisions.

Which child revision a line uses

Each line has a reference mode. The UI calls this Revision:

• PINNED (Pinned to revision): the line always uses the revision you choose. A pinned child must be a revision of the line’s part.
• LATEST_RELEASED (Latest released): the line uses whichever released revision of the child is newest when you look.

Pinning gives you a fixed design. Following the latest release keeps a sub-assembly current without editing the parent.

Multi-level BOMs

A child can be an assembly with its own BOM. This nests as deep as you need, and the result is a multi-level BOM. The BOM tab has three views:

• Lines: only this revision’s own lines.
• Multi-level: the full tree. You can collapse and expand each sub-assembly.
• Flattened: every line at every level in one list, with no nesting. The BOM is flattened so you can scan or count it. Each quantity is the line’s own quantity, per one of its parent.

Cycles are rejected

A BOM can’t contain itself. A line can’t point at its own revision, and a pinned line that would make a loop is refused. Lines that follow LATEST_RELEASED can still form a cycle through other parts, such as A uses B and B uses A. BuildTrace can’t see that when you add the line. It reports the cycle when it builds the BOM, and getEffectiveBOM answers with a conflict. Remove one of the lines to fix it.

The effective BOM

The base BOM is the lines you edited. The effective BOM is the base BOM plus the change orders that are effective at a date you choose. It shows what production will use.

Use the Effective as of date on the BOM tab to look at any date. Leave it empty to see today. Lines that a change order added or replaced show the change order’s number, title and date.

getEffectiveBOM returns this tree. Its effectiveAsOf parameter is the date. See Change orders.

Compare two revisions

On the Revisions tab, choose revision A and revision B and select Compare. The result compares the direct lines of the two effective BOMs, part by part. It marks each part as added, removed or changed, and shows the quantity in A and in B. Parts that are the same in both are listed without a mark. It does not compare sub-assemblies level by level.

Where a part is used

The Where-Used tab shows every BOM that uses the selected part, and whether each line is pinned or follows the latest release. The operation is getPartWhereUsed.