An automated small parts warehouse — German automatisches Kleinteilelager, AKL, and often called a miniload system in English usage — is an automated storage system for containers, cartons or trays in which put-away and retrieval take place without manual access, carried out by storage and retrieval machines or shuttle vehicles. It is typically used for articles of small volume and high access frequency, and it supplies goods-to-person picking stations.
Design
A small parts warehouse consists of racking rows with storage channels, handling machines (aisle-bound storage and retrieval machines, or shuttles on each level), a conveyor front zone feeding containers in and out, and the control layer formed by the material flow controller and the warehouse management system. Customary load carriers are plastic containers and trays of defined dimensions; single-deep and multi-deep storage are both possible.
What the guideline understands by it
VDI 3630 "Automatic miniload warehouses (AKL)" (edition 2006-08) is expressly written as a base document for operators, manufacturers and planners — with the purpose of establishing the term and the technical and logistical framework parameters clearly. Systems qualify as such when they store products, as a rule in standardised load carriers — containers, trays, cartons — and are typified by storage machines controlled, as a rule, in three axes for serving the racking.
The guideline describes the system through seven components: storage and retrieval machine, load carrier and load handling attachment, racking system, safety equipment, fire protection, conveyor system and control. It names two typical applications — picking systems and buffer systems. That distinction decides the sizing early, because a buffer is dimensioned by throughput peaks and a picking system by lines per hour.
Shuttle systems as the second design
The alternative has a guideline of its own. VDI 2692 Part 1 "Shuttle systems for small load carriers" (edition 2015-03) understands by these the storage systems for storing — and where applicable also transporting outside the storage area — light unit loads such as containers, boxes or trays.
The difference is not one of styling but one of system: in the small parts warehouse, horizontal and vertical movement are bound into the same machine; in the shuttle system, vehicles on each level take over horizontal transport and a lift takes over vertical transport. Throughput and storage height can therefore be scaled independently of one another — at the price of a larger number of vehicles and a more elaborate control, energy and maintenance concept, which VDI 2692 Part 1 treats in sections of its own.
For sizing, that guideline carries its own section on performance data, the basis of performance calculation, cycle time, the number of shuttle vehicles and an approximation method. Which of the two designs is economical is decided by the quantity structure: location requirement, put-away and retrieval performance, and how far both fluctuate over the day. The two designs are set against each other criterion by criterion in miniload or shuttle system.
Throughput and density
Classic small parts warehouses with one storage and retrieval machine per aisle reach a high storage density at an even performance that is bound to the single machine. Shuttle systems distribute the movements across many vehicles and scale performance through the number of vehicles — an advantage under high peak loads, set against higher investment and greater complexity.
Where the decision sits in planning
The decision for a small parts warehouse is taken in warehouse planning on the basis of article and movement data. It commits building height, fire protection concept and system landscape for a long time, and it is therefore usually secured through a comparison of variants against conventional alternatives. Sizing the equipment itself is part of storage technology planning; the wider field of automation options is compared in the warehouse automation comparison.
Sources
VDI 3630 "Automatic miniload warehouses (AKL)", edition 2006-08, VDI Handbook Material Flow and Materials Handling Volume 5 (replaces the withdrawn Parts 1 and 2). VDI 2692 Part 1 "Shuttle systems for small load carriers", edition 2015-03, VDI Handbook Technical Logistics Volume 5. Both editions confirmed against the VDI guideline list on 5 September 2026.
Automated small parts warehouse in practice: Our services overview brings together the relevant planning and consulting approaches.