By Larry Tyler
Sustainability challenges indus- trial companies to design and produce products and offer services that improve energy efficiency,
reduce pollution, and otherwise make
operations more ecofriendly.
Green manufacturing is not new.
The greening of manufacturing is a direct response to growing environmental awareness over the last 50 years,
and specifically in the last 20 years, of
increasing water, air, and land pollution
all over the world. Most manufacturers
believe that green practices can reduce
operational costs if implemented correctly and are good for business.
One area manufacturers are scrutinizing for improvement opportunities is
in-plant material handling. Forklifts have
a long history of being the workhorses
of factory floors and warehouses. But
manufacturers are re-evaluating their
use of forklifts and looking at alternative material handling systems in their
plants as they strive to pare energy
consumption and increase efficiency.
In fact, the push to embrace methods with green results is prompting
some manufacturers to initiate policies
to reduce the number of forklifts they
But is it necessary to eliminate all
forklifts in the quest to be greener?
How can a factory floor be reconfigured
to increase productivity and eliminate
waste using both forklifts and alternative plant vehicles?
10 THINGS TO KNOW ABOUT
TUGGERS AND CARTS
Manufacturers should review the following questions and their answers if
they are considering converting some
of their plant material handling to a tugger and cart operation:
1. Can I save energy by using few-
er forklifts and more tugs with carts
to move products and materials?
Tugs consume less energy than forklifts because forklifts require two electric motors—one to lift and another to
operate the drive—while tugs need only
one motor. Most of the energy forklifts
consume is while lifting loads.
In addition, because tugs and carts
handle more load volume per move,
less energy is consumed than by the
multiple trips a forklift must make to
deliver the same amount of materials
(see Figure 1).
2. Does using a tugger and cart
system save time?
One tug can pull a train of several carts
across the production floor. The tug
stops at each station to deliver materials and collects empty carts or containers for a total of one complete run.
This reduces wait times in produc-
A tugger turns a corner while pulling a three-roller cart train. Tugs and carts can deliver
multiple loads per trip, improving energy efficiency.
green overlap quite a bit and are hard
to separate. Lean concepts focus on
elimination of waste in a process. A
lean production initiative may implement a green approach that reduces
or removes waste and thereby lessens
the negative impact on the environment.
Tugs and carts can contribute to
both green and lean agendas by reducing energy use and waste. A balanced
approach to material flow incorporates
tugs, carts, cart lifts, forklifts, and conveyors.
Along with the push to go green is a
push to go lean. The terms lean and
Because tuggers need only one electric motor rather than two, as does a forklift, and a
tugger and cart system can transport more loads in one trip, they can save a substantial
amount of energy moving material, parts, and components in some plant applications.
Photo of Freightliner Custom Chassis Corp., Gaffney, S.C.
tion. Assembly operators do not have
to wait until a forklift is available to
move products into a workcell or to
the parts area. Carts can be moved by
hand as well.
3. What type of training is required to operate tuggers and carts?
Tugger controls are simple, and tugger
operation requires only basic, non-cer-tified operator training.
4. How can I use factory space
An approach that combines tuggers
with carts and forklifts can eliminate
congestion and bottlenecks on the factory floor. Redesigning routes to create dedicated paths for carts and tugs,
forklifts, and people can reduce traffic
in heavily traveled areas to improve material flow (see Figure 2).
Improved material flow can reduce
inventory at workstations and increase
worker productivity. If a workcell has
more than four hours’ worth of parts
or assemblies inventory, that usually
means the forklift driver has “buffered”
his route with material that should be
in the parts area.
5. We have been using forklifts
since our plant opened. Can I elimi-
nate all forklifts?