Sub-Assemblies

A sub-assemblySub-AssemblyA reusable assembly block that composes into bigger BOMs. Define it once, include it in any BOM. At execution time, Assemblified expands the sub-assembly into its own components recursively. Read more → is a reusable bundle of components. Define it once, drop it into any number of BOMs. When a BOM that contains the sub-assembly executes, the sub-assembly is recursively expanded into its own components.

Sub-assemblies sit between raw materials (the leaves) and BOMs (the finished goods you sell). They have no Shopify variant of their own, so they don’t appear in your storefront — they’re pure recipe.

On this page

• When to use a sub-assembly vs a flat BOM
• How sub-assemblies relate to BOMs and raw materials
• Pre-assembled stock at the sub-assembly level
• Capability snapshot — every page in this section

When to use a sub-assembly

Reach for a sub-assembly when:

• Multiple BOMs share the same component group. If 20 of your candle BOMs all use the same wick + wax + jar, define a “Candle base” sub-assembly once and reference it in every BOM.
• You build the bundle ahead of orders. A sub-assembly can carry its own pre-assembled stockPre-Assembled InventoryStock of finished sub-assemblies and BOM items that have already been built and are sitting on the shelf. When a work order needs a sub-assembly, it draws from pre-assembled inventory first and only builds fresh ones if the shelf comes up short. Read more → . Builds you finish ahead of time go on the shelf; the next BOM that needs the sub-assembly draws from the shelf first.
• You want to model a step in your assembly process. Sub-assemblies don’t have to map to a sellable product. They can represent any stage that you complete and stock separately.
• The recipe is shared but the finished product varies. 20 different candle scents share the same physical assembly recipe but have different scent-oil components. A “candle base” sub-assembly + per-scent oil component reduces duplication dramatically.

You don’t need a sub-assembly when each BOM has unique components — flat BOMs are fine.

How sub-assemblies fit in

BOM (sells one finished good)
  ├── Raw material X (qty 2)
  ├── Sub-assembly Y (qty 1)
  │   ├── Raw material A (qty 3)
  │   ├── Raw material B (qty 5)
  │   └── Sub-assembly Z (qty 1)  ← nesting
  │       └── Raw material C (qty 1)
  └── Raw material V (qty 1)  ← virtual material possible too

When the BOM executes, this whole tree is walked, multiplying the parent quantity through each layer.

Pre-assembled at the sub-assembly level

Sub-assemblies have their own pre-assembled shelves with the same dual-storage as BOMs (an aggregate count + per-location entries). When a parent BOM expands the sub-assembly during execution:

1. The sub-assembly’s pre-assembled stock is consumed first.
2. Only the remainder pulls the sub-assembly’s own components.

This drawdown is per-layer, recursively. A BOM with two layers of nested sub-assemblies has two opportunities for pre-assembled stock to absorb the requirement before raw materials are touched.

See Sub-Assemblies → Pre-assembled stock.

What you can do with one

Create a sub-assembly Form walkthrough — adding raw materials, nesting other sub-assemblies, setting waste %.

Nesting & execution How recursive expansion works at order time, with worked examples and quantity multiplication.

Keep-assembled cascade The SA-level Keep Assembled flag, the halt rule, and how it interacts with the parent BOM's flag on cancel/refund.

Pre-assembled stock The sub-assembly's own shelf — how it's consumed during parent BOM execution and how to adjust it.

Where to next

• New to sub-assemblies? Read creating a sub-assembly to walk through your first one.
• Already have BOMs and want to factor out shared components? Build the sub-assembly first, then update the BOMs to reference it.
• Curious about cancel/refund behavior? Jump to keep-assembled cascade for the table.