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, enforce a clear identification policy for all returning materials. The warehouse should only accept verified, traceable assets back into active stock.

Triage: good, suspect, and scrap

Separate returning materials 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: Verify the returning quantity → Print a new system label if necessary → Execute a “WIP-to-Stock” transaction in the system → Return 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:
  • Do not return these items to the active warehouse shelves.
  • Record the loss digitally in the MES/ERP against the specific Work Order to capture the Yield Variance.
  • Discard the material 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:
  • Isolate the material visibly (e.g. in a red bin or clearly marked bag).
  • Move the material to the Quarantine/MRB area.
  • Hold 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. Define thresholds for what is practical to return.

• SMT Reels:
  • Consider setting a minimum return quantity based on feeder requirements. 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, transfer the good parts to an intact carrier or scrap them. Damaged packaging frequently causes jams in pick-and-place equipment.

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, place the material in a new, intact ESD bag.
  • The Requirement: Ensure 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, investigate the discrepancy 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.