> ## Documentation Index
> Fetch the complete documentation index at: https://docs.arcuserp.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Bills of Materials
> Create, revise, compare, activate, and use Bills of Materials for assemblies, disassemblies, conversions, phantom BOMs, cost rollups, availability, and work order creation.
A Bill of Materials, or BOM, is the recipe Arcus uses for manufacturing. It decides
which product is produced, which source item is converted or disassembled, which
components are consumed, returned, scrapped, or retained, and which active recipe
MRP and work orders should use.
## Start From The BOM List
Open **Manufacturing**, then **Bills of Materials**. Use the list to search recipes,
filter by BOM type or status, review how many lines the BOM has, see active work
order counts, set the default recipe, and open a BOM detail page.
Use the active work order count before archiving or revising. A BOM with open work
still affects shop-floor activity, component demand, and manufacturing reporting.
## Choose The BOM Type
* **Assembly**: consumes component inventory and produces a finished product.
* **Disassembly**: consumes a source product and returns or scraps the recovered parts.
* **Conversion**: starts from a source product, removes or retains parts, adds other parts, and creates a different output product.
Do not treat the BOM type as a label. It changes how the work order behaves at
completion, including whether Arcus receives finished goods, consumes a source
product, recovers components, or changes source serial status.
## Create A Draft BOM
1. Open **Manufacturing**.
2. Open **Bills of Materials**.
3. Click **New BOM**.
4. Choose **Assembly**, **Disassembly**, or **Conversion**.
5. Enter a name and revision that operators can recognize.
6. Select the output product.
7. For a conversion, select the source product.
8. Enter the output quantity per run.
9. Create the draft BOM.
Draft status is the safe place to build and review the recipe. Active status should
mean the recipe is approved for work orders and planning.
## Build The BOM Detail Page
Open the BOM to finish setup. The detail page combines the header actions, summary
cards, component table, cost breakdown, tree view, and material explosion preview.
1. Review the output product, source product, output quantity, revision, and status.
2. Add component lines from the product catalog.
3. Choose the correct disposition for each line.
4. Add instructions on lines when the floor team needs repeatable build guidance.
5. Review **Total Cost / Run**, **Unit Cost**, and **Can Build Now**.
6. Switch between **Flat** and **Tree** when the recipe includes subassemblies.
7. Use **Full Material Explosion** to simulate a larger build quantity and find leaf-level shortages.
8. Activate the BOM only after the output, components, dispositions, cost, availability, and instructions are correct.
### Component Dispositions
* **Consume**: removes component stock during material issue or completion backflush.
* **Add**: treats the part as a new item installed during conversion.
* **Return to stock**: returns a removed component to inventory during disassembly or conversion.
* **Scrap**: records the removed component as scrap instead of available stock.
* **Retain**: leaves the part with the source item and does not create a new stock quantity.
### Conversion Layout
Conversion BOMs split the detail page into **Parts to Remove from Source** and
**Parts to Add**. Use that split as an operating checklist. Removed parts should
have return, scrap, or retain dispositions. Added parts should have consume or add
dispositions.
Put build instructions on the BOM, not only in team memory. Line instructions and
BOM notes are visible when the work order is created from the recipe.
## Review Cost And Availability
Arcus calculates cost from the component lines, returned value, labor assumptions,
overhead, output quantity, and scrap factor. Availability shows how many runs can
be built from current component stock and which part limits the build.
* **Total Cost / Run**: estimated cost for one BOM run.
* **Unit Cost**: estimated cost per output unit after output quantity is applied.
* **Can Build Now**: the maximum number of runs supported by current component availability.
* **Constrained by**: the component that limits the build quantity.
* **Full Material Explosion**: a simulated requirement list for the number of units you enter.
Cost rollups are planning values. Actual work order cost can change when materials
are issued at FIFO cost, labor is recorded, overhead is applied, substitutions are
used, or components are short.
## Manage Defaults, Revisions, Compare, And Clones
A product can have multiple BOMs. The default active BOM is the one planning tools
and quick-build flows should use first.
1. Use **Set default** on the approved active BOM for a product.
2. Use **Revise** when an active or superseded recipe needs a new draft revision.
3. Decide whether the old revision should become superseded when the new draft is created.
4. Use **Compare to** when another revision exists and you need to review header, component, and cost differences.
5. Use **Clone** when a similar product needs its own draft BOM.
6. Use **Build This** only after the BOM is active and the work order should use this exact recipe.
Compare is most useful before activating a new revision. It highlights added,
removed, changed, and unchanged component lines, plus header and cost differences.
If the compare menu is not visible, the product does not have another BOM revision
available to compare.
## Use Phantom BOMs Carefully
Turn on **Phantom BOM** only when the parent should not be stocked separately and
planning should pass demand through to the child components. Phantom BOMs can be
useful for reusable subassemblies that should not create separate stock, but they
also change how MRP explodes material requirements.
Do not activate an incomplete or experimental phantom BOM. Active phantom BOMs can
change MRP suggestions by planning components instead of the parent item.
## Archive Or Replace A BOM
Archive old recipes instead of deleting operating history. Arcus blocks archiving
when active work orders still reference the BOM. Complete or cancel those work
orders first, then archive the BOM. Archiving also clears the default flag so the
product does not keep pointing at an archived recipe.
Use a new revision when the same product is still being built with a changed recipe.
Use a clone when a different product needs a similar starting point. Use a new BOM
from scratch when the physical process is meaningfully different.
## Common Blocks
* **Product search finds nothing**: confirm the product exists in the current entity and the search term has at least two characters.
* **Activate is disabled**: add at least one component line before activating the draft.
* **Build This is disabled**: activate the BOM before creating a work order from it.
* **Compare is missing**: create or revise another BOM for the same product first.
* **Archive is blocked**: complete or cancel active work orders that still reference the BOM.
* **Can Build Now is zero**: review component availability, tracked inventory, and the constraining component.
* **MRP ignores the product**: confirm there is an active default BOM, the product supply method allows manufacturing, and the BOM is not archived.
* **Wrong cost rollup**: review component cost, returned value, labor rate, overhead rate, output quantity, and scrap factor.
* **Phantom planning looks unexpected**: confirm whether the parent should be stocked separately or whether MRP should plan through to child components.
## Related Articles
Create, release, start, complete, close, or cancel manufacturing work from active BOMs.
Run MRP, review build and purchase suggestions, include safety stock, and create draft WOs or POs.
Create products and finish the tabs that drive inventory, purchasing, shipping, listings, and manufacturing.
Understand product type conversion rules, FIFO layers, product value, and Recost repair behavior.
Create kits, add components, understand kit cost, and sell bundles safely.
Review WIP aging, cost variance, build history, and component usage from work order activity.