Materials Handling: The basics of automation

by Dave Luton

Warehouse automation has been around for a long time, but a number of logistics and market trends have increased demand for it in recent years.

Probably the most notable trend is the continuing decline in shippable order size, combined with decreases in quantity per order line. This results in increasing pressure to ship less-than-case sized orders.

While this has been most notable in order fulfillment, increasing pressure to automate is found in all warehouse functions.

In this environment, it is worthwhile to go right back to basic first principles and consider what your options are in each warehouse department.

We will cover it in a couple of columns because it is too large a topic for a single column. Initially we will focus on the inbound side from receiving to putaway into storage.
A simple process can be used to categorize types of warehouse or department options by classifying the different types of basic material flows.

One simple way of summarizing these is:
a)    Unit load (usually pallet) in/unit load out;
b)    Unit load (usually pallet) in/piece or broken case (less-than-full-case) out;
c)    Piece or full-case in/piece out;
d)    Piece or full-case in/broken case out;
e)    Less-than-full-case in/less-than-full-case out.

Starting at the beginning, all goods enter the warehouse via a receiving process. The receiving process for full cases handles large or small quantities.
1    For Unit Load Sized Quantities Received per SKU – Automation candidates include specialized non-pallet attachments, along with driverless unloading vehicle technology like AGVs. In this case additional automation equipment includes; pallet inverters; load transfer stations and palletizing equipment (most commonly from manufacturing).

2    For Smaller Full Case Quantities per received SKU – Automation equipment includes extensible conveyors.

For receiving less-than-full-case quantities, often a two-stage receiving process is used and the second stage maybe combined with putaway for some types of automation.
Note, as well, that automation also involves the WMS/WCS control system.

A good example at this phase is the handling of back-ordered items, for which the WMS should control special routing. This bypasses conventional putaway into storage, and transfers the items directly to packing and shipping.

From receiving, the next stage in a traditional warehouse is putaway into storage. This is often integrated with material flow technologies, through the use of pick-up and dispatch or drop-off locations to integrate two automated systems. In some automated technologies (eg AS/RS) the same equipment is also used for order picking.

In these instances, the warehouse equipment can be divided into two basic classes:
a) Take the picker to the stock, or b) take the stock to the picker. An example of a) is a lift truck. An example of b) is a carousel.

Basic material flow (for horizontal and vertical transportation) automation technologies includes: AGVs and SGVs; conveyors; lifts; and, specialized overhead equipment, like monorails.

For putaway (into storage) automation technologies include:
1    For Unit Loads – AS/RS; orbital shuttle systems; specialized AGVs like vision guided vehicle (VGV), which are also called vision-guided automated lift trucks (ALT); and, dynamic storage systems like pallet flow and pushback racking systems.

There are some hybrid combinations of storage and handling systems that use modifications to traditional equipment to increase productivity, but do not fit the traditional definition of automation. Properly designed, these may permit an interim stage to increase productivity before full automation. An example is a system that permits two pallets to be put away and stored at the same time. This uses conventional lift truck equipment with a specialized double pallet-handling attachment.

The next stage in the automation process is to use a full ‘vision guided vehicle’ for both putaway and order selection.

2    For Cases, Pieces or Less-than-Full cases – Miniload AS/RS; horizontal carousel; vertical carousel; and, VLM (vertical lift module). Specialized automation applications include systems like hanging garment systems, AutoStore from Swisslog and the Amazon Kiva Robots.

3     For automated storage systems like dynamic storage systems, we will cover these more fully in the next column.

Traditionally automation in the warehouse has concentrated more on the order selection side of the business because the greater use of labour creates more opportunities for payback. There are also opportunities in other warehouse departments.