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Press system mixes automatic and manual operations.

Press system mixes automatic and manual operations Pressroom efficiency doesn't depend on presses alone. This report shows how the total system must integrate material-handling and die-changing equipment as well.

Market conditions can change quickly, and maintaining or expanding market position requires an efficient, adaptable manufacturing base. That's why, less than three years ago, a leading US manufacturer consulted various pressworking specialists about ways to increase both the productivity and flexibility of its stamping operations for powerlawn-mower decks. Among those consulted was Atlas Automation, 201 S Alloy Dr, Fenton, MI 48430.

Late in 1986, Atlas conducted a comprehensive engineering study to identify the most productive and cost-effective mix of manual and automated operations for the facility. Based on this study, Atlas engineers designed and installed a pressworking system tailored to the present and future needs of the plant.

The system employs five high-speed hydraulic presses. Two are unloaded by programmable part-transfer units, and the other three are unloaded manually. Careful attention to both equipment selection and layout help to ensure that additional part-handling automation can be phased in speedily if needed. The line produces decks for all of the firm's lawn mowers.

Installation

Before the pressworking system could be installed, the user had to modify his existing plant. Modifications included new foundations, raising the roof to accommodate new equipment, rerouting water and gas lines, laying new electrical lines, installing a power generator, and building an office facility.

Atlas engineered the modifications, supervised construction, and assumed sole responsibility for completing the site work. Then they installed the pressworking system itself in two phases.

The first phase included two hydraulic presses, two T-table die-change systems, material-handling conveyors, an automatic scrap-disposal system, and two cranes. They completed this phase by November 1, 1987, at which time the first two presses were producing parts.

The second phase, completed in July 1988, included installation of a 350-ton predraw press, an 850-ton draw press, and a 350-ton press for trimming and piercing. Each press has a T-table die-change system.

Material-handling equipment includes a Cranesaver, sheet destacker, and roll coater for applying drawing compound. Other components include two programmable part-transfer units, a turnover device, and two additional belt conveyors.

Operation

Steel sheet starts its journey through the automated press line after it's placed in the Cranesaver, a storage and material-handling device that improves press uptime. It lets an operator stage a new stack of steel on the load station during production without waiting for an available forklift or crane.

Next, a destacker with vacuum cups removes individual sheets from the stack. Several features prevent double sheets from being loaded into the press. First, a series of magnetic sheet fanners advance against the side of the stack. These help separate sheets as they are lifted by the vacuum cups. Special actuators help peel the top sheet off the stack cleanly. Also, the system employs a double-sheet detector that stops the line in the event of a double feed.

The destacker places the sheet against the underside of a magnetic roller conveyor. Each of these units employs stationary permanent magnets inside revolving nonmagnetic stainless steel tubular rollers. To prevent excess contaminant build-up, only the bottom of each roller is magnetized.

The conveyor transfers clean, correctly positioned sheet into the press through an Atlas Rollcoater. This device applies a preset amount of drawing compound to both sides of the sheet. After coating, the sheet moves into load-station tooling, where air-operated locators align it for press loading. Rolls and locators adjust for variable sheet sizes.

The load station has an integral horizontal power unit equipped with bars that push sheets into the line's first press. Once the first press completes its operation, an overhead programmable transfer unit removes the part and loads it onto a conveyor.

Next, an operator manually loads the part into the second press. After the press cycle, a second programmable transfer unit removes the part and places it on a conveyor, which transfers it to subsequent operations.

Faster die changes

Although the remaining three presses are currently loaded and unloaded manually, the system's conveyors and automated scrap handling reduce reliance on direct labor. Furthermore, reduction in die-change time for all five presses helps boost overall productivity and flexibility.

Use of T-table die-change systems is a key factor in time saving. In designing the line, Atlas specified large-window presses to allow for the use of these systems, which possess the combination of speed and economy that the lawn-mower manufacturer required.

Along with the T-tables themselves, the systems employ a number of other elements, including die-carrier subplates, die top-plates, hydraulic T-slot lifters in the press bolsters, and hydraulic die clamping.

In a typical die-change operation, as a part runs, the operator moves the dies for the next scheduled part to the T-tables via an overhead crane. He then mounts the dies on subplates, and attaches top-plates.

At completion of a press run, the operator pushes a button to deactivate hydraulic clamping of the die and raise the ram. Next, he activates the hydraulic T-slot lifters, and a push-pull module grips and extracts the old die. The powered T-table moves this die to one side while moving a new die to the loading position. Then, the module pushes the new die into the press.

Finally, the operator lowers the T-slot lifters, brings the ram down to contact the upper die shoe, clamps the die, and raises the ram to starting position. For safety and ease of operation, all die movements are controlled by pushbuttons and valves.

After completing the die change and resuming production, the operator detaches the top-plates and subplates from the dies he had removed, and returns the dies to storage, using a crane. The top-plates and subplates are uniform in size to facilitate handling.

"The technology employed in this pressworking line is highly effective," notes Atlas spokesman Dan Leighton, "Even more significant than any particular piece of equipment, however, is the way the system as a whole satisfies the customer's needs. It meets the required production rates of 350 to 450 pcs/hr, achieves the desired flexibility, and will accommodate additional automation when needed. This is the sort of system capability that pressworking operations need for the long run."

PHOTO : Atlas T-table die-changing system for exchanging prestaged dies.

PHOTO : Atlas Cranesaver is shown with staged blanks and destacker.

PHOTO : Line of presses connected by conveyor. Prestaged dies appear on table at right.
COPYRIGHT 1989 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1989 Gale, Cengage Learning. All rights reserved.

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Publication:Tooling & Production
Date:Aug 1, 1989
Words:1064
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