6.2 Put-away & location control

Physical put-away translates “financial possession” into “operational availability.” If a component sits on a warehouse shelf but remains unassigned in the WMS, it acts as a Phantom Shortage. This can cause the MRP system to trigger urgent re-orders while the required stock is already in the building. The primary objective is synchronization: ensuring the physical reality of the inventory matches the digital map in the ERP at all times.

The “scan-to-location” protocol

Relying on human memory for stock transactions must be avoided. Digital updates should occur simultaneously with physical handling, rather than as batch updates later in the shift.

• The Standard WMS Transaction:
  1. Material must be transported to the target zone.
  2. The Bin Location Barcode (The Destination) must be scanned.
  3. The Part ID / License Plate Barcode (The Item) must be scanned.
  4. The Quantity must be confirmed.
  5. The item must be placed securely into the bin.
• Handling Guidelines:
  • The Protocol: If a scanner is unavailable, moving the physical box must be delayed until real-time tracking can be maintained.
  • The Protocol: If the system suggests a bin that is already full, the material must be scanned into a designated “Overflow” location immediately. Leaving material unassigned on the floor must be avoided.
  • The Protocol: If an item is found in a bin that the WMS indicates is empty, a Cycle Count must be triggered to reconcile the discrepancy.

Managing broken packs & partial units

In high-mix assembly, identifying and tracking “Cut Tape” and partial component reels is a common challenge. Once a manufacturer’s sealed bag or reel is opened, the component’s digital identity can quickly be lost.

• The Guideline: Raw components must be kept linked with their physical identity labels.
  • The Protocol: When cutting a strip of tape for a sample or a small kit, it must be ensured the original manufacturer label remains with the bulk stock.
  • The Protocol: For cut strips too small to hold the original label, an Internal UID Barcode Label (containing MPN, Lot, and Quantity) must be generated and affixed to a bag containing the strip.
• Unidentified Loose Parts:
  • The Protocol: If loose, unlabelled passive components are found on the floor, it is generally safer to scrap them than to guess their value. The risk of mixing similar-looking components (like a 10kΩ and a 10.1kΩ resistor) is too high for reliable production.

Pro-Tip: ESD-safe bags must be used for cut SMT tape. The UID barcode label must be placed on the bag rather than directly on the physical tape. Adhesive residue on the tape can cause issues with high-speed SMT pneumatic feeders.

Location strategy & segregation

Warehouse locations must be structured based on component velocity and physical ESD characteristics.

• Velocity Slotting:
  • For High-Frequency (Class A) Parts: These must be slotted in the “Golden Zone” (e.g. waist height, near the kitting area) to minimize travel time.
  • For Low-Frequency (Class C) Parts: These must be stored in higher/lower racking or in Automated Vertical Lift Modules (VLMs).
• Mixed Bin Guidelines:
  • The Ideal State: One SKU per physical Bin ID must be maintained.
  • High-Density Storage: If mixed bins are necessary (e.g. partitioned drawers):
    • It must be ensured parts that look identical are not stored in adjacent compartments to help prevent picking errors. Clear dividers and distinct labeling must be used.
  • ESD Compliance: Active components (ICs, FPGAs) must be stored in Conductive or Static-Dissipative bins/totes. Standard “Pink Poly” is typically insufficient for long-term storage of sensitive devices.

Final Checkout: Put-away & location control

Control Point	Process Requirement	Recommended Target
Transaction Timing	Real-time digital scans are required.	Dock-to-Stock Time: < 24 hours.
Location Accuracy	Material should always have an assigned WMS location.	High WMS Location Accuracy (> 99%).
Partial Units	Cut tape and partial bags maintain a readable label.	Minimizes unidentified material scrap.
Bin Organization	Mixed SKUs in a single bin use clear physical dividers.	Reduces piece-part picking error rate.
Overflow Protocol	Secondary overflow locations are tracked in the system.	Maintains accurate inventory visibility.