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Automating panel fabrication.

Automating panel fabrication

In early 1986, Armstrong Air Conditioning Co, Bellevue, OH, installed a flexible steel-coil fabricating line to manufacture panel enclosures for a new line of high-end air-conditioning units. The new product and fabricating line were designed simultaneously.

The system combines coil feeding, stamping, and roll forming with automated conveyor handling. The line produces 25 different panels using four different sized steel coils. Current production requirements for 50,000 air-conditioner panels and 8000 air-handler panels require and line run on a single-shift basis.

Air conditioner production includes seven different front, side, and access panels, for five models of the CJK units. For the two models of USA air handlers, two separate side and rear panels are produced.

A clean sheet of paper

"The CJK was designed with a clean sheet of paper," says Douglas Dreten, superintendent of plant operations. "We asked two questions: what do people in the market-place want, and how can we produce it? On the production side, we made a conscious decision to forget about how we traditionally manufactured products."

All functional disciplines of the company were brought together in the design phase, in an attempt to design for manufacturability. "We identified the product design in a general way, and then began talking to equipment suppliers." Mr Drenten explains. After much discussion, the company selected The Bradbury Co Inc, Moundridge, KS, as a turnkey supplier.

"When we first started the excercise, we came up with some outlandish manufacturing ideas," says Mr Drenten. One such idea was to produce louvers through a rolling punch. "But as we came back down to earth, we identified indirect costs associated with moving material around the shop, and the direct costs associated with press braking, as areas we could realize savings."

One month installation

The $2.5 million, 162-ft long system was installed and ready for production in only one month. At the front end of the system is a 20,000-lb-capacity uncoiler. Four widths of 0.052" steel coils are stored in an adjacent warehouse and picked up by a coil cart that travels on rails. The cart hydraulically lifts the coils so they can be placed on a mandrel on the uncoiler.

A peeler table and coil straightener maintain tension strength as the coils are guided to an edge trimmer. Two edges of all coils are trimmed for positive locating surfaces. Adjacent to the edge trimmer is a scrap chopper that reduces all trimmed scrap to 1/2" pieces.

The coil steel then enters the heart of the system, a digital roll feeder. The roll feeder passes the steel between two rollers to feed it into the press. This device allows the single action press to stamp the wide variety of panels required.

"The digital roll feeder allows us to continuously feed into the press with an accuracy of [+ or -]0.005"," says Douglas Drenten. "All of our dies are in permanent locations in the press, and the roll feeder gives us the flexibility to manufacture panels of varying lengths."

Mr Drenten explains that about 80% of the IBM PC operation that controls the system is dedicated to the Indramat CCS-03 roll feed controller. This system uses an optical encoder to measure actual feed lengths against programmed lengths to stop the steel in the correct position for the stamping to take place.

A host PC computer downloads part parameters into the IBM PC, which then generates the machine-based language that runs the line. The program is then fed to the Indramat unit. Roll feed can also be programmed manually at a station next to the roll feeder.

Gag dies

The 400-ton, single-action mechanical press uses progressive tooling to notch, louver, and shear the panels. The dies are mounted on subplates to minimize changeover time between air-conditioner panels and air-handler panels. Each subplate has locators to ensure correct positioning of the dies during set up.

"The press travels at a constant rate," Mr Drenten explains, "so we use gags to manipulate which dies are engaged by the ram. With this setup, we can produce bands of six or eight louvers in any multiples up to 48, and up to five rows across. The louver dies take about 60% of the tonnage we are using." The gags are wedge-shaped devices that allow selective engagement of dies during the ram's stroke. They are engaged by air-actuated solenoid valves that are controlled by the IBM PC.

Because the tooling is mounted on subplates and pinned into the press for positive location, dies cannot be quick changed like hydraulically clamped dies. Typical changeover time between air-conditioner and air-handler setups takes about 3.5 to 4 hours. To further speed changeover time and increase efficiencies, Mr Drenten is taking a more fundamental approach.

"Traditionally, when we needed to change tooling, we would have one die setter assigned to one machine," he explains. "The die setter would go to the machine, walk around and unbolt the die, put the new die in, and then clamp all the bolts down." Through standardization of bolts, straps, and hand tooling Mr Drenten hopes to achieve much better efficiencies in tool changing.

"The analogy of Indy car racing is a good example of how we plan to accomplish die changes," Mr Drenten says. "We'll have a team of guys converge on the press, each one responsible for specific actions. Operations will be broken down into smaller-sized pieces so they can be performed simultaneously. That's one way we can gain further efficiencies in this system."

After panels are sheared in the press, they are conveyed to the roll-former stations. In the case of the air-conditioner parts, the panels are first automatically flipped over to orient the louvers for the roll-forming operation. The system includes part manipulators before each roll former to position and orient panels.

"Before the panels enter the roll former, they first go through a launch table," explains Mr Drenten. The launch table has an edge gage that ensures panels are perpendicular and centered. Once aligned, the panels are fed into the roll former.

The roll former fabricates two edges at a time, using a progressive series of 20 rollers on each side to make incremental bends in the steel panels. "When we first looked at manufacturing these panels, we knew roll forming could greatly speed the fabrication process," says Mr Drenten. "You can't compare the time it would take to make all of these bends on a hand-fed press with roll forming." After the first two edges are formed, the panels are rotated 90 deg before entering the second launch table and roll former.

Similar to the press tooling concept, the roll formers are mounted on plates, with rafts of 10 rollers on each plate. This again helps to minimize changeover time between parts. The plates include the rolls, arbors, and gear drives and are stored adjacent to this portion of the line. An overhead crane is used to change rafts and dies.

Indirect savings

The entire fabricating line is run by three operators. One works in the control booth and oversees the operation of the system. Two floor operators do all setup work, and unload and inspect panels as they come off of the line. With only three operators and no material movement between trimming, stamping, and forming operations, there are both direct and indirect savings.

"What you have with this system," says Mr Drenten, "is straight direct labor costs from when the coil is loaded onto the cart until a finished panel is sent to paint. All the associated indirect costs of moving parts from a slitter, to a shear, to a press are eliminated."

Mr Drenten also points out that there are substantial direct labor savings because there are only three operators. "From a total processing cost, this method is without a doubt more efficient," Mr Drenten says, comparing it to traditional shop routings.

As part of the system installation, the company created new job classifications for the operators. The positions are still hourly rated, but are not piece work operations. "There was some hesitancy at first, but nothing more than usual with something new."

Giant step

Before the systems' installation, the firm had been strictly a hand-fed press operation. The move to a fully automated stamping line was a giant step. In addition to changing roles in the factory, it created many, and sometimes unreasonable, expectations throughout the organization. "Anytime you introduce automation into that kind of environment, it is perceived that it will allow you to do anything you want, because now you have computers," Mr Drenten explains.

Although it is sometimes referred to as a FMS, the system is more realistically a dedicated fabrication line, with inherent flexibility within a family of parts. "The system is set up to produce a lot of different parts, with very few changes required within a product family," Mr Drenten says. "It does get us closer to a flow-type inventory approach because we go from raw material to finished part with no intervention."

The stamping line has helped the firm to run much smaller lot sizes on CJK and USA panels. This allows them to react better to customer and marketplace needs. "We often run the same parts and product three or four times a month now, instead of running 15,000 pieces at one time and putting them in inventory," Mr Drenten says. "We have reduced our inventory-in-process significantly."

Future plans

"Right now our biggest bottleneck is assembly," says Mr Drenten. "We are supporting two shifts of assembly with a one-shift operation of the system."

Mr Drenten says the company wants to alter the system slightly to increase its utilization. He wants to be able to use portions of the line independently, so a different product can be run through the roll former while the press is stamping another product.

Another increase in utilization will come from new products. "We are going to higher efficiency furnaces and air conditioners," Mr Drenten says. As the company moves forward to meet federally mandated energy regulations, products will be designed for more flexible fabrication. "We made the investment in the system," Mr Drenten concludes. "It is inherently more quality responsive and fits our future plans to further achieve a flow-type inventory approach to manufacturing."

PHOTO : The $2.5 million automated fabricating line was installed and running production in one month.

PHOTO : Digital roll feeder continuously feeds steel coils with accuracies of [+ or -]0.005".

PHOTO : Permanent tooling arrangement has all dies mounted on subplates to help speed changeover. Air-actuated gags determine which dies are engaged in the stamping operation.
COPYRIGHT 1990 Nelson Publishing
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Copyright 1990 Gale, Cengage Learning. All rights reserved.

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Author:Arter, Richard
Publication:Tooling & Production
Date:Sep 1, 1990
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