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Which machining center?

The universal machining center may be a machine whose time has come. A machine tool that can attack a part both vertically and horizontally and do full-horsepower cuts on all five sides in a single setup seems like an ideal tool with today's emphasis on minimal setups and quick turnaround times. Yet, its reception in this country has been underwhelming-so much so that no US-based manufacturer has chosen to produce universals here as yet, nor seems likely to do so soon.

Why is this? There are several reasons, but the key ones are a basic difference in our machining philosophy and how we rationalize costs. European genealogy Universals were invented by Deckel in Germany in 1903, and have enjoyed great popularity there and throughout Europe ever since. These were knee mills, manual machines attuned to the needs of the skilled machinist who wanted to do heavy milling cuts by manipulating the spindle head rather than the part. They found a home in tool-and-die shops, mold making, toolrooms, and light-to-medium production where they could be combined by an inventive machinist with secondary operations right on the machine table or close by. As those machinists trained apprentices or became shop supervisors, their appreciation for the flexibility of universals was passed along to succeeding generations.

Today, the universal market worldwide is a very significant 8000 machines sold per year, 6000 of these in Europe, says Deckel export manager, Norbert Otto, in Munich, Germany. Yet, here in the US, the annual universal market is 400 machines at best. He also notes relatively little demand for universals in Great Britain or Japan, although a lot of Japanese tool-and-die shops use manual universals for one-of-a-kind jobs and small-lot production. A few Japanese machine-tool builders offer manual universal machines, but none have chosen to automate universals and challenge the German universal builders in the world market.

The principal players promoting the universal approach in this country are Deckel Products, Indianapolis, IN, and Maho Machine Tool Corp, Naugatuck, CT, in the small-to-medium sized machines, and Ferrostaal Machine Tool Corp, Placentia, CA, in the larger bed and moving-column universals. Last year, Maho was the first to begin building universals here.

Too many choices

Part of the problem is too many machining-center choices today. There are something like 140 builders of vertical machining centers and nearly half that many making horizontal machining centers. Each offers a variety of controls, palleting, toolchanging, machine-monitoring, and automation options. A lot are newcomers with remarkably low prices, and in today's slow market, there's a lot of price-cutting and sales gimmicks to wade through.

The other problem for universals is the price premium for their versatility. It's hard to evaluate on a spreadsheet. Although universal proponents maintain that the price for their machine is not that different from a good horizontal machine, the cost for a fully equipped universal can be as much as the cost of the two conventional machines they replace. The question can become one machine, one setup, one operator versus two machines, multiple setups, and maybe two operators. Or, if my universal goes down, all my production stops versus if one of my two CNC machines goes down, I can still cut parts. A tough choice.

Basic comparisons

In this three-way contest, the vertical machine offers lower initial investment and easier setups and part handling. Its disadvantages: singleside access, poor chip removal, and greater operator involvement.

The horizontal machine offers excellent chip flow, faster metal removal, less operator involvement, and four-sided machining with a rotary table. Its disadvantages: higher machine cost, higher fixture cost, and less accessibility to the workpiece.

Universal machining centers offer to settle this debate by offering five-sided machining in one setup, with no compromise in accuracy or horsepower in either attitude. They can also now match the others with a full range of automation options from manual machines to fully palleted automatic machines that can change tools in either vertical or horizontal mode. Swiveling heads or NC tables provide cutting at oblique attitudes or up to five-axis machining capability.

Large universals Helmut Pongs, vice president, Ferrostaal Tool Corp, Placentia, CA, is trying to bring the universal message to users of high-end machine tools who can benefit from milling, boring, and even turning of heavy parts in one setup with his SHW machines. "Our best chances here are in bed-type and traveling-column milling machines, starting with the smallest size at 1500 mm bed size and 2-m column, beginning at $500,000 and going up to $1.2 million with all the options." Although he sees no competition from domestic builders, Pongs sees possible competition here from Spain (Zayer), Italy (Mandelli), and Great Britain (Buttler), mostly in traveling-column machines.

SHW started marketing in the US three years ago, and has two major installations: a plastics-mold maker and a butterfly-valve manufacturer. These UFDZ 1200 machines (ranging in price from $800,000 up to $1.2 million with pallet shuttling) combine vertical and horizontal milling with vertical turning. "The valve manufacturer," says Pongs, "has a floor-to-floor time of 3 hr for work that took four machining centers (two turning and two horizontal milling) 3.5 days. In addition to that time savings, there were cost savings in jigs and fixtures."

One inhibiting factor in the acceptance for his newer-concept machines, says Pongs, is that people want to see the equipment in operation-the actual savings and operating advantages first hand. "The key questions for a potential customer should be how much time can be saved, what part quality is needed, and what are the real cost savings. When you compare all these features, no one can beat us."

Medium-sized universals

Although Maho has installed over 1400 universals in the US over the past decade, that total has not made a major impression on their nonuniversal competitors here, particularly those selling low-end vertical machines. Yet, Maho US President, Harold Welge, feels good about the progress the firm has made here. "We've seen a steady increase, and the acceptability is a lot better today than ten years ago. The concept is much better understood."

And timely, with the move toward smaller lot sizes? "Yes, that and with the need today to do as much as you possibly can in a single setup. This is just as true in milling as it is in turning. We are becoming a manufacturing society where you almost have to produce one part as cost-effectively as 20, and to do that, you need versatile equipment."

New levels of universal automation have contributed to Maho's growth, particularly the dual toolchanger introduced four years ago, says Welge. He acknowledges that the alternative to a universal machine is a cell with vertical and horizontal machines linked by a pallet changer. "Yet, with the universal approach, you have all that in one machine. You do not necessarily need dedicated products running across it to justify such a system. You can be ready for whatever job comes along, and machine effectively in less setups than a conventional machine would require."

He admits the initial outlay for his universal is more, but at the end of the year, he says, ask yourself how much more that universal produced. "If you buy a machine for $100,000 and make a 1000 pieces a year, and you buy one for $200,000 and it makes 5000 pieces, which is the cheaper machine?"

Any compromises? Is the vertical portion of a universal a compromise over what that machine can do horizontally? "If you have a heavy-duty bed-type horizontal machine," Welge replies, "of course you would have a bigger. load capacity. Our machines are designed from the ground up to be a universal machine. You do not sacrifice in either the vertical or horizontal mode, if you stay within its load capacity. A 20-hp universal gives you 20-hp cuts in either position. However, if you take a standard vertical or horizontal machine and add dividing heads or rotary tables, you lose travel, rigidity, and accuracy with those add-ons."

Doesn't adding an NC cutting head detract from a universal's capability? Yes," he admits, "if you add a C-axis head for angular cuts, you lose horsepower when using that C axis for machining. Most of the time, however, the C-axis head is used for NC angular positioning and then locked. For standard motion, you don't lose anything."

Moving into automotive

Welge says Maho is finding new applications in dedicated-production situations where lot sizes are low and there's a mix of complex product shapes and sizes and a need for tight tolerances. "We're doing very well in aircraft work and the mold industry, and even automotive model and prototype shops and small-lot production of spare parts. As automotive moves further into JIT, it's not feasible to run lots of 100 spare parts on a transfer line, and our machines come in very handy."

Isn't workpiece indexing an alternative to the universal? "It depends on the complexity of the part," he replies. "If you're just drilling and tapping holes on three or more surfaces, yes, you may be better off with a vertical machine and part indexing. But with heavier milling cuts, you need rigid part support.

"A great benefit that a lot of people overlook is the simplicity of fixturing parts on the universal machine. Most of the time, you only need to clamp them down. A conventional machine may be lower priced, but you may need three or four fixtures per part, and butting up against a machined surface to get your next setup will require accurate and costly fixturing. Whereas universals, time and time again, eliminate a lot of these situations."

Spreadsheet shortcomings

Welge complains that users seldom go beyond the purchase price in their justification calculations. "In modern manufacturing today, the purchase of a machine tool is just one item in the entire process. It's no longer floor-to-floor time, but door-to-door time. When you put all the cost factors together, the cost of a machine tool to manufacture a given product may be your smallest cost.

"A spreadsheet doesn't show productivity. We had a case where using a form of spreadsheet analysis, a competitor's conventional horizontal machining center looked good on paper, with twice our rapid traverse rates and three times our toolchange times. But when they made a part, and we made that same part, they took 14 min and three setups, and we took 9 min and one setup-we were almost 50% better! The specs of a machine tool do not relate directly to the speed of making a part. That's where a lot of people get confused."

So what are the primary reasons people buy universals today? "Versatility," he replies, "and accuracy. We can achieve very close tolerances, even under production conditions."

Do you concede anything to a vertical machine without a universal option? "Maybe speed, depending on the application, and simplicity, but not accuracy. In a job shop where you don't really know what's coming through the door next week, you want to be as versatile as you can be."

A domestic response

For the other side of the universal story, we asked Steve Peterson, vp-worldwide, Giddings & Lewis, what his company's response is to those considering universal machine tools. "We address that two ways. We can provide machines in either the universal configuration via some kind of two-axis attachment (head or table) or create a cell with pallets shuttling between two dissimilar machine tools. For example, we can provide a horizontal machining center with a two-axis tilting attachment that can reorient the cutting head to the vertical attitude."

Does this represent a compromise in changeover speed from what a universal could provide? "Not really," he replies. "Our NC attachment reorients the cutter right now-bang-with a servomotor tilting action."

Doesn't that load up the cantilevered weight of the head and compromise accuracy or rigidity? "Yes, anytime you add a joint, there is some compromise in rigidity and accuracy. Whether it's an integral head or add-on head, it reduces the horsepower cuts you could normally take through that structure."

When a customer needs volume production and the versatility of heavy cuts both vertically and horizontally (maximum rigidity in both machine tools), G&L provides a cellular solution: two machines linked by a palleting arrangement. There are two schools of thought on this, Peterson explains. "One says to take a universal machine, and try to do as many operations on it that you can, recognizing that that has some very severe rigidity problems. The other approach is to use machines dedicated to vertical turning, horizontal milling, or whatever, and shuttle the part between them."

Considering that the smaller the part, the easier it is to manipulate it, doesn't that make the universal argument harder to sell on the low end of part size? "Yes, it's simpler to move around a smaller part with a pallet system than a larger part, and there are many more ideas for manipulating parts today than there were a short time ago. We have been fortunate to have our long association with Gilman Engineering to draw on its experience with automatic assembly. We drew on that to build pallet systems for cells. Yet, we've also made the transition for people who want to leave a part on the machine tool by putting two-axis tilting heads on a machine tool or two-axis tilting tables to tilt and rotate the part.

"Granted, you can do a lot of work in one setup on a universal machine, but you will lack the rigidity of doing that same part on dedicated machine tools. There is no difference in the accuracy between our horizontal or vertical machines; we build both to the same very stringent accuracy and repeatability tolerances."

The add-on philosophy

Peterson cites a basic add-on philosophy here versus Europe. "Builtin facing heads, for example, were very popular in Europe for a long time and not popular here. The philosophy here was that if you needed a facing head, you put one on, not make it an integral part of the machine tool. That's like the philosophy here that people buy machines for either vertical or horizontal work, and if they have an odd job that needs reorienting, they are more than happy to pick up an attachment to do that, recognizing that if that were an integral part of the machine it would be more rigid. So they take lighter cuts with it. Then, when they need maximum rigidity, they can take that joint off and run the machine at maximum power."

With more emphasis in this country on dedication and less on flexibility, isn't this a mass-production philosophy that is becoming outdated by the move to just-in-time? "It's not a mass-production philosophy," he counters, "just a higher-production philosophy. People buy a vertical or horizontal machine and take 75-hp cuts, whereas, if they put some kind of universal head on it, they would get a lot more versatility, but be limited to maybe only 50-hp cuts.

"I'm not saying that versatility is not good-we produce machine tools that are versatile. I'm just saying that we tend, as a manufacturer, to look at the application, and if it's low-production oriented, we'll go for the more versatile machine tool. If it's more production oriented, we'll go for two dedicated machines with an automatic pallet transfer between the two. There's still a tremendous opportunity out there for the versatility a small cell can provide-and it's expandability.

"When you buy a universal and your production requirements increase, you buy another. With a cell, you can add a machine of dissimilar configuration-add other operations-and greatly expand production."

It depends on design

Cincinnati Milacron acknowledges the trend to use five-sided machining to finish a part in one setup, but they are not trying to compete head-to-head with the universal either, feeling there's plenty of business in sticking with primarily vertical or horizontal machines.

"There are many parts designed today that don't lend themselves to a single grabbing of the workpiece and finishing it," says Milacron's Cecil Breeden, machining-center product manager. "A lot depends on how products are designed. You may have to go back and reorient a product into another plane for a second operation, and then the tradeoffs between a universal machine and conventional vertical or horizontal are not as great."

"The trend to universals is in small-batch operations where you need to reduce setup time," says Milacron sales project engineer, Don Ward, who feels heavier parts in steel and cast iron need a bed-type machine and much heavier cuts. "Although a lot of people are going to low-batch operations to create JIT schemes, a lot of our customers are in a high-production environment such as automotive and are simply trying to get more production."

Ward agrees that as production lots get smaller, the universal approach tends to make more sense. But it also helps to make an effort to coordinate your product design efforts with your machining capabilities. Milacron cites some parts they manufacture that have recently been redesigned to be machined in a single handling-a four-sided machining on a horizontal machining center and rotary table.

Universal credibility?

Yet, Milacron's Breeden admits universal improvements like those cited by SHW's valve manufacturer are believable. "Combining other operations into a single handling of the workpiece can result in those type of direct savings. I don't think they are being overstated. With the trend to JIT and trying to get down to economic lot sizes of one, having to batch parts and move them from one operation to another certainly creates longer lead times. With the drive to get more cost competitive, to reduce lead time, and produce higher-quality parts, multiple operations on a product are certainly desirable."

Would you recommend a two-machine cell as an alternative to a universal? "If you need to hold a relationship between four surfaces and a fifth surface and can do that in one handling, for us to recommend two machines and two settings would add complexity. Holding the tolerances by introducing another handling and repositioning of the workpiece would be more difficult. Yet, there are cases where six sides need to be machined, and a five-sided machine gives no advantage."

Adds Ward, "We don't lose any performance in our product by adapting dedicated machines. We can still take 20-hp cuts, but it's not our purpose to make these machines as easily adaptable as a universal might be. Our purpose is simply to to fill a customer's needs the best way we can."

But no threat yet

Milacron doesn't see any narrowing of the gap between the European and US universal philosophy, as we head toward smaller lot sizes. If they did, they would be doing something to address that demand. With the volume of universals sold here in a year not much more than what one major builder does in a single month, they are not worried, at the moment at least, about missing the universal boat. Still, they respect the pioneers, such as Maho, for carving a niche to the point of building machines here, but they do not feel threatened by them.

"It sounds good-something that everybody should want," says Breeden, but they seem to be making slow progress. When you look at what you can buy in a small vertical for $60,000 to $80,000, and sell at $35/hr, a shop can put a lot of work across it and make a lot of money. The biggest obstacle for a universal may be its price-the cost for a machine to do small parts. I see a trend in larger parts to five-sided machining, very definitely. Bridge-type products with horizontal/vertical spindles have been on the market for years, although not many were sold."
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:horizontal, vertical or both
Author:Sprow, Eugene E.
Publication:Tooling & Production
Date:Jun 1, 1991
Words:3282
Previous Article:Quality tools simpler as automation takes over.
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