Tower Automotive's new parts delivery system keeps materials moving and eliminates line slowdowns in vehicle frame production.

Speed, flexibility and safety. Those were goals that Tower Automotive had in mind when designing the materials handling systems for its new automobile frame production facility in Madison, Miss. And that's just what the manufacturer got for its efforts.

The facility builds four types of frames for pickup trucks and two for sport utility vehicles. After being painted at an adjoining facility, the frames eventually head to the nearby Nissan assembly plant that produces Titans, Pathfinders and the Infiniti QX56 models.

A major initiative in the Madison design was to streamline the movement of materials to assembly lines. This was done through the use of ergonomic wheeled carts that hold materials and can be positioned easily line-side.

'In addition, we now have 50–60% less lift truck traffic during our production hours,' says Mike Bolen, operations leader.

Previously, a lift truck brought an initial container to the line and materials were pulled from it for the assembly. Once the materials were consumed, another container was brought line-side and exchanged for the empty container.

This procedure, however, required precise timing. The lift truck had to be at the line with the new container at the exact moment when the exchange was to take place. Otherwise, the line would stop to wait for more materials.

Another solution would be to have lift trucks arrive early and wait until the moment for the exchange. However, that was not good use of the driver's time and greatly reduced lift truck productivity.

In the new Madison plant, the delivery of the parts is much smoother since the introduction of a cart system. As with the other facilities, parts in Madison are consumed a container at a time line-side. This keeps the lines from being cluttered and fits Tower's philosophy of lean inventories.

'Our goal is to have only four hours of parts on hand,' explains Bolen. 'We receive four shuttles a day from a nearby vendor-managed warehouse. This allows us close access to the inventory without having to own it. It is brought to the facility only when needed. Besides these parts, other suppliers also deliver their products to us three or four times each day.'

All receipts of parts arrive in returnable containers, which are scanned as they reach the receiving docks. This triggers management software to assign the containers to their line destinations. Nothing goes into storage, as all is consumed at the line.

The containers are then loaded onto a variety of wheeled carts, which are designed to properly accept the dimensions of individual returnable containers. Some of the carts allow the parts to gravity feed to workers from their containers. Other carts adjust the containers to make them easier to access at the line. Another style of cart is actually a small flow rack on wheels that feeds small totes of parts to the front for picking.

Once parts are on their assigned carts, lift trucks then pick up the carts with their embedded containers and carry them to the line.

Two carts of each type of material are placed in each line position. Parts are pulled from the one cart, while the other cart is queued in a waiting position until needed. Once materials are depleted from the initial cart, it is simply pushed by workers away from the line and the new cart is wheeled into place. The carts weigh about 1,100 pounds when full, which is a weight that is easy for one worker to maneuver.

The worker collapses the empty container when the cart is pushed away from the line. This signals lift truck operators patrolling the area that the empty cart is ready to be collected and another cart is needed to replace it in the queue.

The savings in time and effort by using this system can be significant, as there are some 450 container exchanges every day at the lines. Bolen also says that the move to the cart system has been very smooth.

'We have not had to deviate from our original vision,' he says. 'Our materials flow as they are supposed to and we have had no down time because of loss of flow.'

The carts (Topper Industrial) and their containers are also made to protect the line workers from potential injury.

'We have designed the materials handling equipment to reduce the ergonomic risk,' notes Bolen. 'We have reduced the physical demands just by how the parts are presented to the line.'

Many of the parts used to produce the frames weigh 20–30 pounds. To make working with these parts much easier, they are provided to the worker in the correct orientation to reduce lifting and turning and also at the proper height for ideal lifting.

'Many of the carts are designed to tilt containers forward to prevent workers from reaching into them,' adds Chris Wiser, production leader. 'Some also have platform lifters. As the basket depletes with parts, it raises to keep work at the right height.'

Besides the cart system, the facility also uses 78 robots to precisely handle and weld many of the parts. Additionally, an overhead power-and-free conveyor and electrified monorails are used to transport the frames through the various assembly points along the line.

The flow of materials through the facility has been smoother and much safer, thanks to the combination of the wheeled carts, assembly robots and conveyors.

'We have improved our materials handling methods to where we have fewer lift trucks in here and fewer safety concerns,' adds Bolen. 'As a result, we have had no lost time incidents during this first year of operation.'