The Essentials of Material Handeling / Part II - The Basic Product Knowledge Program

DISCLAIMER OF WARRANTY

The Essentials of Material Handling™, of which this document is but one part,
is an educational program created expressly as an information source and useful
aid to individual professional development. Information contained in this work
has been obtained by the Material Handling Industry of America from sources
believed to be reliable. However, it is to be viewed as a reference, and neither
the Material Handling Industry of America nor its authors guarantee the accuracy
or completeness of the information published herein and make no warranties
whatsoever (express, implied or statutory) in connection with the use of this
document. All implied warranties of merchantability or of fitness for particular
purposes are disclaimed. This work is published with the understanding that the
Material Handling Industry of America and its authors are providing a basic
educational service and are not attempting to render engineering or other
technical service. If such services are required, the assistance of appropriate
professionals should be sought.

Copyright ©2004
Material Handling Industry of America
Charlotte, North Carolina

The Essentials of Material Handling
Part II – The Basic Product Knowledge Program
Section 5
Dynamic Storage Systems

PREFACE

The Essentials of Material Handling™ is a two-volume education program
under development by the Material Handling Industry of America. Each
volume contains several major sections; and each section contains multiple
chapters or study modules. The material contained herein is one of the modules
in the Basic Product Knowledge Program. Other modules available for
purchase are shown on the loose leaf insert accompanying the package you
received. Inquiries about the entire two-volume education program and the
status of any one module can be made by contacting the Material Handling
Industry of America.

The Essentials of Material Handling™ program was written to facilitate its
being used either as a self-study course . . . employing end of module test
questions, or as require reading as part of a formal class or training program.
Overhead transparency masters are available for each module as an aid to the
presentation of the subject material in a classroom, lecture format. Qualifying
instructors should contact the Material Handling Industry of America regarding
the availability and cost of the transparency masters.

Section 5

Section 5
1

MODULE 5.5 – WRITTEN BY ED ROMAINE
SPONSORED BY THE AS/RS PRODUCT SECTION OF MHIA

VERTICAL LIFT MODULES

LEARNING OBJECTIVE
By the end of this module, the reader will be able to describe the operation of
Vertical Lift Modules, the applications to which they are suited and the benefits
resulting from their use. The reader will also have a basic knowledge of the
principle components of a Vertical Lift Module and the various configurations and
operating strategies that can increase the performance of order picking
applications. A historical path is followed through the module as the uses,
feature and benefits of VLMs have evolved.

INTRODUCTION

Vertical Lift Modules, or VLMs as they are often referred to, were introduced in
the early 1970’s for warehouse and industrial applications. The early versions
had very lightweight capacities and were fairly slow, limiting their applications.
As the application possibilities grew, so did the demand for a new generation of
VLMs that provide much greater weight capacities, intelligent user interfaces and
increased operational speeds.

A VLM operates by using three basic columns. The front and rear columns are
used for storage and are equipped with brackets which function like shelves to
support trays or totes. The center column, which is largely an open shaft, is used
for an insertion/extraction device that operates within the columns, much like an
elevator, moving up and down to store and retrieve trays or totes as directed.
Figure 1, on the next page, illustrates a Single Bay VLM. When the operator
requests a tray, it is delivered through an opening at an ergonomically designed
work height. The vertical arrow in Figure 1 illustrates the up and down travel
path of the insertion/extraction device, to and from storage locations. The
horizontal arrow illustrates the motion of the inserter/extractor device as it
deposits and picks up loads; in this case, the illustration highlights a deposit and
pick up at the operator pick point.

The major benefits of the VLM are scalability, high-density storage (space
savings), ergonomics, increased picking productivity and security of inventory.
Depending on available ceiling heights, the VLM can provide space savings
ranging from 50% to 80% over the use of conventional shelving or even drawer
storage products.

Section 5
2

Figure 1. Single Bay VLM

Today, VLMs are designed to be flexible and are capable of handling material
from lightweight, small parts to heavy, raw material, cases, tools and dies. They
are available as independent modules (one inserter/extractor per module – see
Figure 2a) or in multi-bay configurations (see Figure 2b). A multi-bay
arrangement provides additional product accessibility and is typically available up
to four bays wide.

Figure 2a. Illustration of a two-bay system with an inserter/extractor
device dedicated to each bay.

Section 5
3

Figure 2b. Illustration of a four-bay system with a single
inserter/extractor device that can cross over between
bays, thus allowing one set of inventory to be distributed
or shared between units

VLMs can be integrated into an existing host inventory management system via
control systems and PC-based software.

In application, VLMs are found in warehousing to support order picking and order
fulfillment, as well as, in reverse logistics applications to support the processing
of returns. In manufacturing, the applications range from supporting the building
of kits for the shop floor, no unlike order fulfillment, to the buffering of work-in-
process between manufacturing stages. Moreover, there are many specialized
uses of VLMs in more controlled situations such as in clean rooms or refrigerated
environments.

BENEFITS

Although a VLM system provides numerous benefits and cost justifications, users
are initially attracted to its high density and small footprint. With space savings of
up to 80% (actually documented), it is easy to understand why; but the real
benefits and cost justification become clearer in the system’s ability to increase
productivity by minimizing human effort, as in the case of reducing the need to
walk great distances and helping to reduce inventory by first controlling access to
what is being stored, and second by way of the real-time, accurate updating of
inventory records via the controlling software.

FLOOR SPACE SAVINGS
Most facilities are constructed with high ceilings. The VLM is a fast and easy
way to make use of the otherwise wasted overhead space, thereby reducing the
amount of floor space dedicated to storage as illustrated in Figure 3.

Section 5
4

Figure 3. Illustration of floor space savings attributed
to one side-by-side VLM

facilities that don’t have exceptionally high ceilings can take advantage of the
VLM’s ability to connect or span floors. It is not uncommon to have a VLM start
on one floor and, with it height, span up to 60 feet, providing access to what is
being stored on nearly every, if not every, floor.

Likewise, a VLM’s ability to store trays of goods with as little as an inch of
clearance between the trays provides far greater density than standard shelving,
bins or racks. Pullout modular drawer systems are often touted as high-density
storage systems; and they certainly are in certain applications in comparison to
shelving, but practically speaking, they are limited to the height and reach of an
individual and certainly cannot easily take advantage of overhead space without
resorting to mezzanines, steps or ladders.

INCREASED PRODUCTIVITY LEVELS
Increased productivity of existing personnel, or reductions of the staff necessary
for the storage and retrieval functions and their redirection of other operations are
outcomes typically associated with the deployment of VLMs. This increased
productivity coupled with lower levels of required labor or man-hours is often
attributed to:

Faster transaction times because the correct item is always presented for
picking.
Walking and browsing through bays of shelving is eliminated.
The operators do less physical walking, bending, reaching and lifting
allowing them to perform at maximum capacity longer with less stress.

Section 5
5

Operators and workstations are visible to the managers eliminating
“unofficial breaks” while walking down rows of shelving.
Batch picking or pre-sorted and organized pick lists dramatically increase
picking efficiencies.
VLMs utilizing inventory management software or controls assure that the
correct SKU and quantities are available at all times.
Trained operators spend more time working. They are less likely to call
out due to sickness or injury because using a VLM system is
ergonomically friendly and less physically demanding than manual
systems.

AN ERGONOMIC & OSHA FRIENDLY SOLUTION
Because materials are presented waist high, organizations often utilize VLMs to
help ensure OSHA compliance and to reduce potential employee injury related
costs. VLMs virtually eliminate the need to reach, bend, and climb mezzanine
steps, ladders, or worse yet, to use stools. Most organizations find the benefits
of providing improved ergonomic conditions also increases short and long term
profitability by minimizing worker compensation claims, the training of
temporaries, the cost of so-called mis-picks, and more generally by contributing
to improved morale and a reduction in employee turnovers.

SECURITY & REDUCED SHRINKAGE
Every VLM can be viewed as an enclosed, six-sided safe, offering extremely
effective security for valuable SKUs, as well providing a clean and safe storage
location. Security can be increased via mechanical and electronic methods,
including passkeys or passwords that limit access by individuals to specific
storage locations within the VLM, if not the VLM in it entirety.

SYSTEM COMPONENTS

Remembering what was said in the introduction, VLMs are comprised of an
external box-like structure containing trays on the front and back of the unit. An
inserter/extractor platform, much like an elevator or “dumb waiter”, operates in
the center shaft. The inserter/extractor takes trays from the stationary position
and delivers them to an operator at a pick window. One or more units can be
used independently or multiple units can be combined as an integrated system
using advanced software and controls.

BASIC OPERATION
The operator walks up to the VLM and enters a tray or part number via a keypad.
That information is then communicated to the unit’s control system. The
inserter/extractor platform is directed to the correct tray level and extracts it from
its stored position and delivers it to the operator at the pick window to complete
the transaction. When the operator is done, the operator presses the “task
complete” button and the tray is returned to its original or alternative storage

Section 5
6

location. This process can end after one cycle or it can be repeated as often as
needed.

ADDITIONAL FUNCTIONALITY
Additional means of inventory control are available from most manufacturers.
This includes a wide variety of onboard controls, multiple levels of inventory
management software that may be linked to a company’s commercially available
warehouse management system (WMS) and enterprise resource planning (ERP)
system, or some other proprietary system for total inventory and business
management. Other technologies that can be integrated include:

Barcode Scanning
Pick-to-Light Systems
Hoists and/or Vacuum Lifts
Carts
An Automatic Guided Vehicle System
A Conveyor Interface
A Robotic Interface
Voice activated instructions

TRAYS OR SHELF LEVELS
Trays provide an area for users to store their inventory. The standard tray sizes
range form 24 inches to 34 inches deep and 24 inches to 120 inches wide.
Standard load capacities range from 500 lbs. to 2,200 lbs. per tray. Some
manufacturers offer additional tray widths, depths and weight capacities as
options. Tray configurations available for VLMs are almost unlimited. Most
manufacturers can meet specific needs by providing simple partition and divider
systems (illustrated in Figure 4), reel holders, or special application-specific
custom inserts to virtually meet any need.

VLMs can have more than one access window or workstation. The VLM can be
accessed from both the front and rear of a unit installed in a wall, thus serving as
a “pass-through” storage device (see Figure 5). This allows different
departments or work zones to access one set of inventory in a VLM. Likewise, a
user can take advantage of a tall unit that spans one or more floors in a facility to
serve multiple departments.

Section 5
7

Figure 4. VLM Tray with Dividers for Multiple Stock-Keeping Units

Figure 5. Illustration of multiple pick windows or pass-through
functionality and the ability to span more than one floor

Section 5
8

There are four storage methodologies that VLMs can utilize to match an
application’s business requirements and work flow. Each method is valid and
requires pre-planning to determine which will provide the greatest benefit.
However, the user can easily change the methods at any time. The four
methods are fixed height, optimized, mixed height, and fixed height mixed:

Fixed height storage occurs when the unit is configured in that every tray’s
height is determined and programmed into the VLM controls. Its height
and location is fixed, thus allowing the user to calculate and maximize the
VLM’s density. This is ideal for facilities with static inventory profiles.

Optimized storage allows the VLM’s height detection system to scan the
tray while putting it away and to determine the best location in the VLM for
its storage. A VLM’s controls usually look for the least amount of wasted
space and the fewest amounts of blocked shelves to determine the best
location. This is ideal for rapidly changing inventory profiles.

Mixed height storage allows every tray to be discretely selected to utilize
the fixed or optimized methods. This allows the user to keep most often
used trays closer to the pick window and together for higher throughputs
without compromising storage density.

Fixed height, mixed storage is similar to the mixed height method except
every tray can have a maximum height determined. This is ideal for trays
that have similar sized items and management wants to reduce the risk of
placing the wrong SKU on the tray. This is also ideal when working with
boxes with loose flaps. Otherwise, if a flap opens during storage, the
scanner will sense the new increased height and resulting in poor cube
space within the VLM.

DRIVE SYSTEMS
Today’s VLMs can be offered with single drive, DC or AC motor systems with
either an open or closed loop. Either system is capable of delivering controlled,
gradual acceleration and deceleration to provide protection during the storage
and retrieval of sensitive goods. The closed loop control system provides
feedback-positioning allowing for weight transfer to be accounted for during the
storage process. A fully loaded, heavy-duty industrial VLM tray is capable of
maintaining a load in excess of 2,000 lbs., yet manufacturers offer the ability to
store and retrieve a tray that will not spill a full glass of water. This type of
precision assures that fragile and sensitive material is not damaged. It is a
function that can be set discretely for one or all trays.

Section 5
9

The motor drive system can be located on the inserter/extractor platform or in the
base of the unit. The actual location of the motor has no bearing on the day-to-
day performance of a VLM. It’s unit capacity and the facility’s ability to service it
easily is more the issue.

The heart of the VLM is the inserter/extractor platform. The vertical motion of the
platform is driven by the motor system via a chain, a cable, or a rack and pinion
or toothbelt system (see Figure 6). Each system has its own advantages and
disadvantages depending upon the application. This issues a user needs to
inquire about, regarding the drive system, are its reliability, the service and
maintenance requirements, safety-related issues and requirements, and noise
levels likely to be generated during operation.

Cable or Wire Rope Tooth Belt Rack & Pinion Chain

Figure 6. Types of Vertical Drive Systems

CONTROL SYSTEMS
VLMs are available with a variety of control systems and PC-based inventory
management packages. In its most basic form, a VLM can retrieve a specific
item by requesting the tray number via a control keypad.

VLMs today are available with fully capable, stand-alone microprocessors or with
PLC/PC-based controls complete with touch screen or alphanumeric keypads
(see Figure 7). These systems have various levels of inventory management
capabilities that can range from simple part location, often used in tool and die
storage, to manage space, batch picking, and to offering advanced reporting
capabilities. This flexibility provides users with the ability to request inventory by
part numbers and descriptions, as well as by known locations. Even kits, bills-of-
material, and assigned work orders can be processed directly by these intelligent
control packages.

Section 5
10

From keypad, to integrated controls, to PC controls, to touch screen PC controls,
a VLM unit can be used independently as a discrete, isolated workstation or as
an integrated part of a total warehouse management system.

Figure 7. Illustration of a Typical Operation Control Interface

One of the most significant enhancements to VLMs has resulted from the
integration of PC-based, inventory management and communication software.
Until the personal computer became widely accepted in manufacturing and
inventory management environments, VLMs remained a simplistic storage
device, where inventory retrieval involved manual tracking of items and their
locations. While European suppliers were successful in marketing upgraded,
stand-alone controls to foreign markets in the early 1980’s, American customers
quickly adopted the use of personal computes located at their workstations. This
accelerated the opportunity for material handling suppliers to develop software to
meet these needs. By the end of the 1980’s, inventory management software
and order processing modules were gaining wide acceptance in the field.

Today, VLMs can e tied together via software that maintains inventory in a
central database. This is typically done using an RS-232 network communication
card or an RS-485 Ethernet or similar system. Picking and restocking functions
can now be initiated at the PC or at an individual VLM location. The result is that
multiple operations can be performed simultaneously, eliminating “bottlenecks”
previously created by single direction communication. The multi-tasking
capability of today’s software platforms has opened the door to significantly
increased application development possibilities for “intelligent” vertical lift module
systems.

Section 5
11

Following the introduction of Microsoft Windows-based software, it became
possible to easily make the final connection, or interface, directly to the
customer’s host system. Whether an application is installed directly at it point-of-
use, or off-site, customers increasingly require that local parts inventory must be
visible to an in-house or host operating management system. This final interface
is now available. Vertical storage devices can now reside as another “address”
on the customer’s internal network or on the Internet. Inventory levels can be
reconciled, order requests can be processed, and final results can be
communicated from VLMs back to the host (ERP, WMS or legacy) system.

In basic terms, two forms of interfacing with a host exist: an integrated interface
or a so-called hostile interface. An integrated interface exists when the host
software is designed to download to the VLM software the required data and then
upload the new data to its database. This two-way communication often requires
co-operation, licenses and user agreements.

The so-called “hostile” interface is basically one-way communication, taking
information from the host and using it at the VLM software level. The host’s
database and systems are not updated which requires another step to reflect
current conditions. Often the data is acquired from the host as printed data and
requires some form of “middleware” software or a proprietary “black box”
software system. A hostile interface is usually without the host’s knowledge and
is subject to having to be revised or recreated when the host software is updated,
reconfigured or changed.

HIGH PERFORMANCE VLM SYSTEMS

While horizontal carousel systems are often associated with high volume, batch
order picking applications, VLMs provide a new twist to this high throughput
arena. By implementing proper slotting, velocity and stocking logic, VLMs are
capable of providing a much-needed blend of higher throughput with high
density. Instead of having operators walking by hundreds of SKUs of slow
moving items stored in pick-to-light flow rack, VLMs are able to store these lower
velocity SKUs in a space efficient system and provide them to the operator when
needed. The general reduction in walking, searching, bending, and reaching, all
combine to increase throughput.

By integrating VLMs into existing workstations with other automated and manual
picking equipment, software is able to direct what is sometimes termed a
“Universal Workstation”. In this environment, one operator can batch pick from a
pod or cluster of horizontal carousels, a VLM, and even a pick-to-light, carton
flow rack in round robin fashion. The addition of the VLM (or vertical carousel) to
the mix allows the storage density of the slower moving SKUs to be maximized
while maintaining high throughput order picking results.

Section 5
12

INSTALLATION
A typical industrial material handling VLM installation will require 3-4 days to
complete. In most instances, this function is performed by factory-trained and
certified technicians and is easily accomplished with heights that can range from
as low as 10 feet to over 40 feet in vertical height. Most units will require the use
of lifting equipment, such as a forklift, and in very unique applications, other
specialized equipment may be needed for installation. The requirements should
be specified early in the procurement process to eliminate surprises later on.

MAINTENANCE
Again, depending on manufacturer and operating conditions, maintenance of
VLMs is performed on a pre-determined schedule and completed by factory
certified technicians. The disruption to perform scheduled maintenance is
minimal and can typically be completed in a few hours on a semi-annual basis. It
should be noted that various local conditions and manufacturer requirements
might alter this timeline.

APPLICATIONS

STAND-ALONE APPLICATIONS
Initially, VLMs for use in material handling applications were designed for the
storage of lightweight items such as electronic components, small inventory
generally found in maintenance departments, stock rooms, and tool cribs, as well
as the storage of documents. Even today, VLMs are routinely specified for work
cell or point-of-use stock needed near manufacturing or assembly areas. Other
stand-alone applications include:

Buffer storage, where the VLM temporarily accepts items while they dry,
cool, or just stay out of the way until they are needed for final assembly or
at a later time in the manufacturing, distribution or shipping process.
Storage of fasteners, connectors, small hand tools and other maintenance
items.
Local storage of heavy dies, jigs, customer tooling and test fixtures.
Work cell storage of machine tools and carbide inserts near machining
centers.
Temporary return parts inventory storage.
Retail distribution systems.
Temperature and/or climate controlled mini-environments.
Multiple floor or work zone buffer and pass-through systems.

VLM applications are as broad and varied as there are industries to be served.
These applications include storing fasteners and parts in work cells for “Lean
Manufacturing”, “Six Sigma”, or “just-in-time” (JIT) initiatives, to being used in
storing postage stamps in a retail store operation, to storing wine for e-commerce
sales and restaurants, to storing fragrance compounds and human tissue.

Section 5
13

VLMs can also be equipped to meet clean room standards ranging from class
100,000 to 1000 environments, which makes it perfect for meeting the FDA’s
GMP (Good Manufacturing Procedures) requirements. Likewise, units can be
designed to operate in freezer, refrigerated, heated, and other more restrictive
environmental conditions.

The foregoing list is long and the application opportunities appear to be endless.
In the next section, we will review how VLMs are currently being applied in
comprehensive systems applications.

VLM SYSTEM ARCHITECTURE
VLMs that are not communicating to external databases (stand-alone) have
always been used by organizations. However, demands for increased supply
chain visibility require that VLMs be interfaced with an organization’s host
software system. Host systems, such as ERP, WMS, proprietary and legacy
systems, are rarely designed to manage VLMs and never to optimize their
performance. This is where VLM or workstation software is required. A common
term for software used to interface with the host is “middleware”, and, in some
cases simply inventory management software.

“Middleware” software is used when the host’s databases are being used to
dynamically track and manage inventory in “real-time”. The middleware is simply
a set of drivers inserted within the host’s software to simply move and position
the VLMs. Often the middleware is a “dll” (Dynamic Link Library) file and is used
by the host as easily as installing a print driver (also a .dll file). Manufacturers
handle this differently ranging from publishing the code, to providing the drivers,
to providing a finished middleware software product.

If the host system is not designed to track and manage a VLM’s operation,
inventory management software is used at the workstation level and
communicates back to the host. There are two types of VLM inventory
management software, TXP (Transaction Processor) software or database-
driven software.

TXP software uses the host’s database of SKUs, locations and quantities, but it
is designed to optimize the VLMs movement, thus increasing productivity and
maximizing storage density. Features of TXP software usually include batch
picking, management reports, tray storage positions, density maximization
algorithms and more.

Database, inventory management software uses a workstation level database to
store SKU quantities, descriptions, and more. The inventory management
software then updates and reconciles with the host at scheduled intervals. The
software’s databases are usually robust SQL, .Net, Oracle, and similar products.

Section 5
14

OPERATOR AND SAFETY

All the manufacturers of VLMs provide significant safety devices to protect both
equipment operators and stored items. Many have also provided internal
systems to monitor a system’s operation and to provide protection of the critical
electro-mechanical components.

Figure 8. Illustration of Various Safety Systems

SUMMARY

STAND-ALONE
VLMs represent one of the newest technologies to fall under the general
umbrella of automated storage/retrieval system (AS/RS), although they were first
put into use in the early 1970s. Their ongoing development and use has been
driven by ever-increasing requirements for improved throughput, flexibility, and
storage density. VLM applications to this day range from low throughput,
secured and ergonomically accessible storage, to lean manufacturing work cells,
to order picking within distribution center operations.

The availability of sophisticated, yet user-friendly controls and software has been
a prime reason for the acceptance and increased application of VLMs. The VLM
has enjoyed a growing market share for storage and order picking applications
that really began in the early 1990’s. the selection of a competent business
partner is increasingly important to insure successful project implementation.

Section 5
15

As with any material handling device, proper application and integration of the
product and system is critical to the success of a project. Satisfied VLM users
routinely find additional needs within their operation where VLMs have proved to
be valid, cost saving, storage and retrieval solutions. This flexible system
provides some of the highest ROIs (Returns on Investment) and IRRs (Internal
Rates of Returns) available for both general storage and order picking
applications. Using the basic justification points of floor space recovery,
increased productivity, improved ergonomics, increased security and better
inventory control, the return on investment for vertical carousels can easily be
proven.

Section 5
16

PRACTICE TEST QUESTIONS

1. VLMs store material within the unit to protect the inventory and reduce
shrinkage.

a. True
b. False

2. VLMs can have the heights adjusted after installation by adding or
subtracting height modules to meet future storage and retrieval
requirements.

a. True
b. False

3. Light Curtains within VLMs scan the height of every tray and stores the
tray in the least amount of space available in the unit to maximize storage
capacity.

a. True
b. False

4. When inventory items are placed on a tray and stored back in the unit, the
tray is automatically weighed to assure that its capacities are not
exceeded.

a. True
b. False

5. When placing inventory in a VLM, the user must be concerned about
loading the trays and unit to avoid an imbalance load.

a. True
b. False

6. The pick window in a VLM is placed at the “Golden Zone” or best
ergonomic position to virtually eliminate bending, reaching and lifting.

a. True
b. False

Section 5
17

7. Space savings of 75% and more are routinely found by utilizing all vertical
space available including the floor below, floor above and up to the
structural ceiling.

a. True
b. False

8. Trays within a VLM can be stored in as little as one inch increments to
virtually eliminate wasted space above items, which is often found in
shelving.

a. True
b. False

9. VLMs can ONLY be used as independent storage systems and cannot be
integrated together or to host ERP, WMS and other legacy software
systems.

a. True
b. False

10. VLMs can have trays delivered outside of the unit and incorporate carts,
vacuum lifts, hoists and cranes to eliminate heavy operator.

a. True
b. False
Provided by:

info@isddd.com | call: 855‐ISD‐TODAY | www.ISDDD.com

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