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Sheet-metal FMS: too big a jump?

Sheet-metal FMS: Too big a jump?

The advantages of FMS are well known, and the number of metalcutting cells has been growing. But what about a sheet-metal FMS? Those FMS cells have been proposed for over a decade with much less success. The advantages are similar, but the cost of the technology and the necessary management commitment to completely reorganize a shop around an automated storage and retrieval system (AS/RS) have been too much for most sheet-metal shops, large or small.

It comes down to answering these questions: Can an automated system really feed my presses better than my army of operators and forklifts? Would an AS/RS system cycle often enough during a shift to justify its cost? Can I afford a five- or six-year payback period instead of the more normal one and two?

The argument for FMS

Here is a quick summary of the key advantages full AS/RS FMS automation can bring to a sheet-metal processing operation:

Improved machine productivity. The biggest single factor is machine utilization, with potential increases ranging from 15% to 40%. The AS/RS keeps your machines fed, with no delays waiting for material to be located and moved into machine-loading position.

Control of inventory. Data on the inventory at each storage point and workstation is monitored in real time and reported on demand. Materials are easily located and never misplaced. Buffer requirements can be analyzed and maintained. Job scheduling is simplified.

Reduced space. Stacked materials use floor space more efficiently and reduce total space requirements.

Improved safety. The reduced forklift requirement means fewer related accidents or injuries.

Reduced damage. Similarly, with less manual handling or moving of stacks, there is much less chance that materials will be damaged.

Extended untended operation. Although a machine loader can feed a single stack to a press and get you through a shift without attention, a full-fledged FMS can get through the night or even a weekend untended.

Lost productivity

In Germany and Western Europe, AS/RS type sheet-metal solutions are being installed at the rate of roughly ten systems per country per year, compared to one or two per year in the US. In both Europe and Japan, there are many examples of relatively small job shops using high levels of material-handling automation. There appears to be a bigger gap here between the capability of our metalforming machines and the equipment feeding them. Handling automation has not kept pace, and productivity is being lost.

Although an operator could probably load sheets faster than a machine loader, the bigger problem is getting the next stack ready in time to achieve JIT-type flexibility. What usually happens is the operator runs the first job, and then goes looking for the materials for the second part of that run, and finds it buried under a stack of five other lots and needs a forklift to retrieve it. Meanwhile, the machine sits idle.

Says Joachim Sahm, VP Marketing and Sales, C Behrens Machinery Co Inc, Danvers, MA, "We've found that the average 'get-material' time for a typical American company is amazingly high: over 10 min. In contrast, with an AS/RS FMS, the average time to return a pallet of finished material to stock and bring out the next one is 1.5 to 2 min.

"With computer control, you always know how much material is available and can create messages automatically on when to restock inventory, usually once or twice a week. With a storage system delivering stacks to the machine

automatically, you can then add a machine-loader or stick with manual loading.

"Another option we offer, the Dispo-Store, can retrieve single sheets from the storage rack for companies running very small jobs, where it doesn't make sense to bring down the whole stack. Reducing the system's weight-lifting requirements also reduces its cost. The picker crane can be much lighter, and its reaction time quicker, quick enough to keep up with each cycle of the press."

European job shop

Behrens has a lot of job-shop FMS installations in Europe, and is so enthused about this business that the company dedicated a single factory in Germany to building material-handling components and storage/retrieval systems. One installation is in a sophisticated job shop that has 100-bay storage system (eight stacks of 12 or 13 bays each) serving three punch presses, a shear, and two press brakes. Thirty bays are used for raw materials, the rest for punched or pre-sheared stock storage. "The small company doesn't have to have a small system," says Sahm.

Some challenges

Installing an AS/RS is a major move. Machine relocation is usually required, and, because of its density, the AS/RS usually requires pouring a new foundation. Machines served can be on either side of a single AS/RS system, but not necessarily in line. Rail-guided carts can move materials in and out, or even turn corners to reach some machines.

Beyond that, you have to be prepared to adapt to it organizationally, in both planning and operations. Storage-and-retrieval systems in the past have not had a very good reputation for living up to expectations. A lot of major AS/RS investments wound up underutilized, or the initial commitment to them was reduced when the learning curve seemed insurmountable and operators short circuited the system.

Clearly, you cannot justify an investment that typically costs $350,000 to $400,000 if its sole function is to deliver a bin of material maybe only once or twice a shift, or even a day. The bigger systems with 200 bays, four or five output stations, plus software, can run $650,000 to $750,000.

Complicating the cost hurdle is the fact that cost justification involves many intangibles. "There's no hourly rate to tag it with, and you can't simply justify it by putting its cost on single products," says Behrens' Sahm. "You must go into overhead costs to see where the benefits actually lie. It's tough to define: it does a lot for your competitiveness, and provides flexibility that you can't easily translate into numbers; but you can't expect a return on investment of less than two years on equipment like this."

A major difference between US and German users is their relationships with suppliers, he notes. Job shops there get a lot of support from their major customers to install systems like this. In one case, a small shop buying an AS/RS system with a 3.2-yr ROI got a commitment from a major customer, Siemens, to honor this investment with a promise to maintain their present level of orders for the next three years. Why? Replies Sahm, "Because Siemens saw a JIT benefit to themselves."

The need for speed

"Over 90% of the time, materials in a shop still sit waiting," admits Bill Hartwick, Factory Automation Systems, Amada Engineering & Service Co Inc, La Mirada, CA. "Press makers have been addressing punching speed, accuracy, bending speed, etc - the value-added processes. We've never really addressed the material-handling or organizational aspects of the processes."

The Amada MARS system attempts to do that, he says, by bringing a rack system right into the manufacturing process. "It's not over against a wall somewhere - those systems have been around for years. Secondary processes fed from the system can be special surface sanding or buffing, bending, spot welding, or other finishing processes. Operators for these processes can get material immediately, and no forklifts need operate within the cell."

A four-rack MARS system costs about $330,000, says Hartwick. "A MARS system can reduce manufacturing floor-space requirements by about 40% and achieve heating savings. Even though the system adds no value to a part, it organizes the shop so that machine uptime and machine efficiency are tremendously increased. All material is produced on demand."

Hartwick feels users can quantify all this in terms of payback. "Even though this technology is still new in the US, we have 400 units in Japan and the UK demonstrating its feasibility. In Japan, where it has been out for about three years, our customers had expected a seven- to eight-year payback, and were willing to invest on that basis. Now, they are seeing actual two- and three-year paybacks."

"This system lends itself to more than sheet material," Hartwick adds. "In Japan, I've seen a press-brake operator use it for tooling, and I can envision doing the same thing with turret tooling. Why send the operator after tooling when you can bring it to the operator JIT?"

Some alternatives

Fred Grohs of Trumpf's Systems Technology group, Farmington, CT, makes a case for the Sheetmaster automatic machine loader as an alternative to a full-blown AS/RS. "It's a low-cost loading/unloading device designed to sell for less than $100,000. It's targeted for a standalone punch press, without all the flexibility and modularity of the more elaborate systems, and can load sheets and remove skeletons or parts.

"It assumes that you can pay attention to the machine for 10-min loading periods. You bring material to it and set tools, and run automatically until that material is gone. You can even run different programs, as long as they use that same material. So you get a lights-out portion of a shift or even a full shift."

Unlike a job shop, a product shop may only work a half-dozen gages of material and not need AS/RS flexibility, he points out. "Here, a five-position horizontal storage system might work," he says. "We have provided a simple conveyor that oscillates back and forth with five 12" stacks of material. Any one of those stacks can be positioned under a picker to load the machine."

Another compromise from Trumpf is a standard storage cell with a single stack with eight-bin storage, called the Compact Store. "With just one vertical column," Grohs explains, "we only need to deal with two motions: vertical to retrieve the bin, and horizontal to position it for machine loading. This has been far more popular than a full-blown AS/RS."

A final suggestion from Grohs: redesign. Instead of using, say, three different gages, redesign the product to use only one. "This may seem like wasting material, but you get better material utilization, and reduce handling costs. So the few pennies a pound increase in material cost is recovered in operational efficiencies."

PHOTO : The Behrens Dispo-Store feeds single sheets to a turret press.

PHOTO : Major AS/RS system from Trumpf is central to flexible manufacturing. It serves two turret presses on one side and a series of press brakes on the other.

PHOTO : The Amada MARS system has been very successful in small job shops in Japan.
COPYRIGHT 1991 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991 Gale, Cengage Learning. All rights reserved.

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Title Annotation:flexible manufacturing systems
Author:Sprow, Eugene
Publication:Tooling & Production
Article Type:Cover Story
Date:Oct 1, 1991
Words:1768
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