Unit Load ASRS

A unit load ASRS stores and retrieves full pallets and other large unit loads with automated machines, with no people handling individual products in the storage system. The baseline configuration runs one aisle-captive crane per aisle, carrying one load at a time into stationary single-deep rack, so every location is directly accessible. HOJ integrates unit load AS/RS with the pallet conveyor, controls, and software connections that feed it as part of its automated storage and retrieval systems work.

Unit Load AS/RS Configurations

Most systems start from the baseline and change one or more variables.

Aisle-changing cranes. Cranes transfer between aisles, so a system can run fewer cranes than aisles when request volume does not justify one crane per aisle.

Multi-shuttle cranes. A dual-shuttle crane carries two loads. It can retrieve a load and store another in the same location without returning to the I/O point.

Double-deep rack. Each location holds two loads, and the rear position is accessible only when the front is empty. It fits low load variety with high turnover, and the crane may need modification to reach both positions.

End-of-aisle picking. The AS/RS delivers a pallet to a workstation, a picker removes the required quantity, and the remainder returns to storage.

Cycle Time and Rack Geometry

A single command cycle performs one storage or one retrieval per trip. A dual command cycle performs a storage and a retrieval in one trip, with empty interleaving travel between the two locations, which reduces total time to handle all requests.

Cranes travel horizontally and vertically at the same time, so travel time equals the longer of the two moves. A square-in-time rack, where reaching the top row takes as long as reaching the farthest column, is common but not necessarily optimal.

For a fixed capacity, aisle count, rack height, and rack length trade against each other. More aisles shorten the racks and response times, but in a one-crane-per-aisle system every added aisle is another crane, a trade-off detailed in peer-reviewed AS/RS design research.

Storage Assignment Logic

The storage assignment policy decides where each pallet goes, and it drives crane travel as much as the hardware does.

Dedicated. Each product has fixed locations sized to its maximum inventory, which leaves space reserved even when the product is out of stock.

Random and closest open location. Any open slot is used. Closest open location fills racks near the I/O points first.

Full-turnover. Fast movers go nearest the I/O point. Heskett's cube-per-order index (COI) rule is the classic form.

Class-based. Products are grouped by demand into zones, which cuts the repositioning a pure turnover policy requires as demand shifts.

Because demand frequencies change constantly, turnover-based allocations are typically recalculated once per period rather than continuously. These rules run in the warehouse management software, and HOJ integrates AS/RS with WMS, SAP, ERP, Oracle, and NetSuite platforms.

Four-Way Shuttle Unit Load Systems

A four-way shuttle unit load ASRS replaces the aisle crane with robots that travel both axes of the rack on tracks, using lifts to change levels. Geek+ X-series robots run fully automated high-density pallet storage in this configuration. The main running aisle is 1,250 mm (49 in) for 1,200 × 1,000 mm pallets, about 40 percent of a traditional forklift aisle.

This differs from a semi-automated pallet shuttle system. There, an operator directs a shuttle from a Wi-Fi tablet while a forklift loads the lane face, and throughput runs about 25 pallets per hour per shuttle.

Infeed, Outfeed, and Pallet Conveyor Interfaces

Unit loads reach the AS/RS I/O point by AGV, conveyor, or forklift. Retrieved pallets either ship, replenish a separate picking area, or go to an end-of-aisle workstation.

HOJ engineers the pallet conveyor side of that handoff, using chain-driven live roller, drag chain, and right-angle transfers, and builds clean handoffs to fork trucks and AMRs. Where palletizing feeds storage, pallet conveyor delivers empty pallets to the robotic palletizer and carries full loads out to wrapping, staging, or the dock.

Removing Forklifts From Storage Aisles

BLS data cited by OSHA counts 614 workers killed in forklift-related incidents from 2011 to 2017. A unit load ASRS takes forklift travel out of the storage aisles and confines lift truck handling to the I/O point.

The automated equipment still has to be designed for safe maintenance. New or modified machines must have energy isolating devices designed to accept a lockout device (29 CFR 1910.147).

Controls, Integration, and Service Through HOJ

HOJ compares and combines pallet AS/RS, shuttle systems, miniload, cube-based storage, and VLMs instead of recommending a single manufacturer's platform.

Controls are engineered in-house through HOJ's PLC and controls integration team. HOJ builds UL 508A panels, builds new systems on Beckhoff industrial PCs, and delivers Ignition HMIs that run across Allen-Bradley and Siemens. Every system is handed off with commented code, I/O lists, and as-built drawings.

A 70+ vehicle service fleet supports the system after commissioning.