Green Manufacturer - September/October 2011

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 employ.

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.

GREEN MATERIAL
HANDLING LOGISTICS

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
most efficiently?

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.