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Making Cat tracks.

There's a better way to make track shoes--not the lightweight, flexible kind athletes use, but the heavy steel kind attached to the tracks of offroad equipment.

Caterpillar Construction and Mining Div, E Peoria, IL, developed a system to speed fabrication of track shoes of varying lengths by automating press die changes and part length setup operations. The goal of the project was to reduce costs by decreasing setup times and in-process inventory.

The shoe production process, including piercing, notching, and counterboring operations, starts with shearing of the appropriate length from custom cross-section bar stock. Part stops determine the shoe width to be sheared, as well as the positioning of the machined features. Caterpillar undercarriage product planning supervisor Terry Pickel explains the old system: "We were using a screw-type part stop that took too long to set up. It was taking us 20 to 30 minutes per machine to change the stop mechanism on a piece-part changeover." When die replacement was involved, changeovers could take hours.

Caterpillar worked with Atlas Technologies, Fenton, MI, to develop a new system that would allow faster changeovers. Atlas performed an engineering study, then designed and built the necessary equipment.

The solution to part length setup limitations at the shear was a programmable part-stop system using an electro-hydraulic cylinder, linear transducer, and digital controller for automatic positioning. The operator enters into the control a process length for the shoe size to be sheared, and the control calculates the proper actuation to ensure the part stop is accurately positioned.

The system is designed to maintain positioning accuracy of |+ or -~0.010" and repeatability of |+ or -~0.005". It can find the exact die placement in the press after a die change, and automatically adjusts for proper part placement. Part stop changes now take about one minute, and the system's positioning accuracy eliminates trial-and-error adjustment and wasted parts.

For rapid changeover of shearing dies, Atlas also installed T-tables that allow Caterpillar to prestage the upcoming tooling while the shear is running. Dies are rolled out of and into the press on the two-station table, and a blade removal mechanism speeds changing of worn shear blades.

T-tables also are helping to increase productivity on the piercing, notching, and counterboring operations. Positioning of dies up to 36" x 54" is controlled by a powered table, and hydraulic clamping eliminates the need for operators to enter the press window to locate or clamp dies.

The quick changeover equipment has allowed Caterpillar to reduce economic order quantities on the track shoe fabrication operation to 200 to 400 pieces, as opposed to the 800 to 1200 parts that would be run using the old system. In addition to this reduction in in-process inventory, quality is easier to maintain because dies can be pulled for inspection or service without long process interruptions.

For more information on press automation from Atlas Technologies, Fenton, MI, circle 333.
COPYRIGHT 1992 Nelson Publishing
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Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Manufacturing Solutions; manufacturing heavy equipment tracks
Publication:Tooling & Production
Date:Dec 1, 1992
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