6.10 Line returns, scrap & nonconforming material

The return flow of material from Production back to the Warehouse is often where inventory accuracy degrades. When unused parts, partial reels, and scrap are returned indiscriminately, it can create “mystery inventory”—items that appear available in the ERP but may be undocumented, chemically expired, or damaged.

To maintain inventory integrity, a clear identification policy for all returning materials must be enforced. The warehouse should only accept verified, traceable assets back into active stock.

Triage: good, suspect, and scrap

Returning materials must be separated into distinct categories. Each requires a different physical workflow and system transaction.

Return to stock (good material)

• Acceptance Criteria:
  • The component and packaging are undamaged and clean.
  • Traceability: The original Manufacturer or Internal WMS barcode label is present and readable.
  • MSD Integrity: Moisture Sensitive Devices have been handled correctly (e.g. baked if required, and sealed in a barrier bag with fresh desiccant).
  • Leader Tape: Sufficient leader tape remains (e.g. > 200mm) to allow the reel to be reloaded onto an SMT feeder.
• Workflow: The returning quantity is verified → A new system label is printed if necessary → A “WIP-to-Stock” transaction is executed in the system → Material is returned to the designated physical location.

Scrap (confirmed bad/excess)

• Criteria: Components with damaged leads, tape strips too short for a feeder to grasp, floor sweepings, or setup/attrition waste.
• Workflow:
  • These items must not be returned to the active warehouse shelves.
  • The loss must be recorded digitally in the MES/ERP against the specific Work Order to capture the Yield Variance.
  • The material must be discarded into the designated Scrap bins.

Nonconforming / suspect (MRB)

• Criteria: Components that exhibited issues during assembly (e.g. “failed on board,” “caused feeder jams,” or “exhibited poor solderability”).
• Workflow:
  • The material must be isolated visibly (e.g. in a red bin or clearly marked bag).
  • The material must be moved to the Quarantine/MRB area.
  • It must be held for Engineering review to determine if the issue is a supplier defect requiring an RMA, or an internal process issue.

The “minimum usable” guideline

Storing unusable material incurs carrying costs and clutters the workspace. Thresholds for what is practical to return must be defined.

• SMT Reels:
  • Setting a minimum return quantity based on feeder requirements should be considered. For example, if a reel returns with fewer than 50 pieces (and a long leader is required), it may be more practical to scrap the remainder than to restock a tiny segment of tape.
• Tubes/Trays:
  • If a component tube is bent or a matrix tray is cracked, the good parts must be transferred to an intact carrier or scrapped. Damaged packaging frequently causes jams in Pick & Place machines.

Labeling & identification discipline

A returning item lacking proper identification compromises the entire inventory system.

• The “Orphan” Strip:
  • The Scenario: An operator cuts a section of tape and returns the remainder without a label.
  • The Result: The material should generally be scrapped. Without the label, the Lot Code, Date Code, and specific MPN are unverifiable.
• Repackaging Guidelines:
  • If the original ESD packaging is compromised, the material must be placed in a new, intact ESD bag.
  • The Requirement: It must be ensured the new bag receives a properly printed label displaying the MPN, Quantity, Date Code, and Lot ID. Handwritten notes directly on the bag do not support systemic traceability.

System reconciliation

The physical return process must align with the digital accounting of the Work Order.

• The WIP Clearing Process:
  • At the conclusion of a work order, the WIP location for that specific assembly line should ideally clear to zero.
  • The Calculation: Issued Quantity - Consumed Quantity - Reported Scrap - Valid Returns = Calculated Variance.
  • The Resolution: If the variance is not zero, the discrepancy must be investigated to locate the missing material or correct the transaction errors before financially closing the Work Order.

Final Checkout: Line returns, scrap & nonconforming material

Control Point	Process Requirement	Operational Objective
Leader Tape	Verify sufficient leader length remains for reloading.	Prevents operator delays during the next setup.
Traceability	Material must carry a valid system label to stock.	Maintains Lot integrity and prevents commingling.
WIP Clearing	The line’s WIP location is cleared between jobs.	Minimizes the risk of cross-contamination.
Scrap Reporting	Record attrition/scrap accurately and digitally.	Prevents “ghost” inventory from accumulating.
MSD Management	Exposed MSDs are baked/sealed before restocking.	Protects the quality of future production runs.