When International Truck and Engine Corp. decided to produce a new high-performance truck - the International 4300/4400 models - the manufacturing processes used for the existing models were improved to create operator-friendly jobs. Some of the worst positions in the Springfield, Ohio plant for force and posture had been near the beginning of the assembly process, where axles are attached to frames, prop shafts are installed, spring u-bolts are tightened and large bolt fasteners are used. These jobs resulted in many lost-time injuries, high job rotation and excessive cost.

In developing the new vehicle manufacturing processes, International took into account employee considerations for ergonomics and safety. Employees in United Auto Workers Locals 402 and 658 and their safety and ergonomics representatives participated in the process to ensure that diverse ideas from many perspectives were considered. A multi-functional team was assembled that included representatives from management and union, production, materials, plant engineering, industrial engineering, quality, health and safety, plant layout, materials handling and planning.

Targeting problem jobs

For more than 30 years, trucks were built right-side-up at the Springfield assembly plant. Employees had to bend over and reach under the chassis to install many parts as the truck moved down a pedestal assembly line. Because the parts being installed were under the truck chassis, traditional hoists could not be used to deliver many heavy parts to the line.

International representatives worked with UAW ergonomics reps to determine where improvements could be made in the frame-building process. This effort resulted in the development of a "legacy list" of problem jobs that were targeted for improvement. The list included many jobs that led to back injuries, shoulder strains and carpal tunnel syndrome resulting from awkward postures, repeated heavy lifting and the frequent use of large, hand-held air impact tools to tighten bolts.

Process changes to the way parts were placed on the frame rails and to the assembly methods started in the frame alignment fixtures with a new lift assist for the 41-pound rear cab crossmember and with raising the frame fixtures to a better height. Huck fasteners and hydraulic Huck guns, coupled with pulse guns and DC nutrunners, replaced the standard hand-held, air impact tools. This reduced stress levels to the operators' hands and arms.

Most of the new tooling was suspended, whereas the previous heavy tools were primarily hand-held. These new tools also reduced the noise levels in an area that has exposures greater than 90 decibels.

Active roles

Before the completion of the final design of both the alignment fixtures and the assembly pedestal line, many employees took an active role in developing the final processes and layouts. They were involved in a "slow build" of prototype vehicles at the Process Evaluation Center. This employee involvement and feedback took place about six months before the actual changes were scheduled to occur. The ergonomic benefits of building the cab right-side-up include better postures and the potential to add more lifting devices. The decision to invert the frame ladder on the pedestal line was ultimately driven by these benefits as well as the potential economic returns from smoother processes.

At the Springfield assembly plant, the "frame ladder" is now inverted using "C-shaped" turnover devices. The devices are held with hoists on an overhead crane controlled with buttons on a pendant that, when pushed by the operator, rotate the frame chassis and place it on a conveyor. The turnover devices make the rotation of a 900-pound, 40-foot frame ladder effortless and smooth. The inverted frame ladders are placed on a moving pedestal line and transported to the front and rear axle pinning station. The axles are delivered via an overhead delivery conveyor and automatically presented three inches above the spring hangers. The axles are pinned to the frame with a screw-style pin. This replaces a manual system where axles and frame were pinned together using brute force.

More line improvements

Other ergonomically improved processes include:

  • The front and rear u-bolt tightening operation - Four new spindle nutrunners lock onto the u-bolt nuts and release automatically when the proper torque specification is met. This replaces a manual operation.
  • The attachment of fuel tank brackets and battery box brackets - They replace bulky metal hangers and are attached with hydraulic Huck fastener tools instead of noisier, heavier air impact guns.
  • The prop shaft (drive line) mounting - The prop shafts are now mounted with a hoist coming into position above the frame. This replaces the previous method of bending over while positioning the prop shaft into place under the chassis with a lift assist.

Before the frame is delivered to the next department, the chassis is rotated back to a right-side-up position for further processing down the main line. This is once again done with the C-shaped inverting fixtures.

Multi-disciplinary teams

The process improvements in the Frame Assembly department were mostly the result of involving workers on multi-disciplinary teams throughout the engineering design and testing process. The UAW safety and ergonomics reps were involved in conceptual phases, design reviews and tooling buy-offs. Also, there was a significant budget commitment to improve the safety and ergonomics of the processes.