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More Automation, Less Manpower

    

 

Smarter Cells and Centers


By Robert B. Aronson
Senior Editor

 

With an economic recovery underway, more and more companies and shop managers are dusting off their checkbooks and looking for new equipment. Some have been limping along on older machines on a make-do basis, have run out of make-do options, and need new machines. The more aggressive are reaching for new markets.

Customers want higher productivity and more automation, so pallet systems are more popular. Demands for lights-out and lean production are seeing more HMCs in demand, and overall there is high pressure for machines that reduce labor costs and out-of-cut time. Also, floor space and power cost, long an issue overseas, is now a growing consideration for US manufacturers.

Here's a sampling of what some machine tool manufacturers are doing to meet these needs.

In looking at the entire production picture, George Yamane, Mazak Corp. (Florence, KY) notes that it is important to understand why a US manufacturing company would locate a production facility in a foreign country or purchase parts from foreign suppliers. "There are two different issues," he says. "Wherever there is significant demand, it is natural to locate production there to manufacture and keep service and spare parts close to your end users. But it is a different story if it's strictly lower price, and production or purchase decisions are moved offshore to take advantage of low labor costs. Manufacturers can easily lose low labor advantages due to 'hidden' costs, like lead time, inventory, quality, and transportation costs. By constantly examining how advanced technologies can increase production efficiency at their plant, the manufacturer can find that they can meet their expectations.

"Manufacturers, though, must constantly be evaluating process changes to take full advantage of every opportunity technologies provide to improve productivity," he adds. "Given the productivity advancements of the last 10 years, if manufacturers aren't improving their processes with advanced-technology equipment, they're at a greater risk of going out of business."

Every product is unique, along with every market's conditions, and there are a growing number of productivity-enhancing machine options manufacturers can embrace, such as pallet changers, material-handling automation, single-setup done-in-one part processing, and even bigger tool magazines. "We have found that many mid-size companies are asking for larger tool magazines. Not long ago, a 20-tool magazine was typical for a small vertical machining center. More recently, we have been offering 120-tool magazines for a five-axis vertical machining center. The customer wants to minimize the changeover time between jobs, and to be sure there are enough backup tools immediately available.

"When manufacturers carefully look at the many ways of improving their process, significant cost reductions result," Yamane concludes. "This must be continuous. You need to innovate the process to gain productivity."

Reaction to globalization, particularly to developments in China has forced US manufacturers to search for ways to reduce costs. That in turn has seen a move to more automation to reduce setup time and labor cost, and increase quality. "The most basic way to achieve this is to shift from several manned VMCs to palletized HMCs," explains Tim Jones, product line manager, Makino (Mason, OH) to achieve more production without adding labor.

"The simplest level of automation is to add automation, such as a pallet system. The next higher level of automation would be an integrated system such as an HMC in a cell configuration with automated loading and unloading.

"The next approach is to add automated fixturing. This will cut the number of setups, plus improve quality. Equipment speed is still important. Most machines have high spindle speeds, but it's more critical to reduce out-of-cut time. For example, during a tool change you save time if the machine does several things simultaneously rather than in sequence, such as coolant off, stop spindle, get out of cut, orient spindle, etc. Many of these operations can be done in parallel, which reduces cycle time and adds valuable production capacity.

"Our newest control offering is a highly integrated, network-based control, so automation is more easily achieved.

"Smart tools are now available that give the machining center multiple capabilities such as honing and grinding. This can eliminate expensive and less-flexible special-purpose machines, reducing our customer's cost of operation."

In the future, we may see more fixture automation. "Already we have supplied the customer with 'live hydraulics' inside the machine that achieves huge improvements in workholding resulting in improved quality control. Fixtures can be programmable, so it will be possible to add and relieve clamping pressure during a cut," Jones concludes.

"We are moving in several different directions as we develop new machines to fill out our product line. We're constantly moving into new categories with machines at various price points, capabilities, and sizes," says Scott Rathburn, Haas Automation (Oxnard, CA). "For example, at the last major show we introduced 11 new machines that were preproduction or prototypes. We are particularly looking to expand our HMC and lathe markets, where we see a lot of potential for growth.

"We introduced the EC-500 HMC, which is a larger version of our EC-400 with a larger work envelope and swing that can accommodate larger parts. We are also getting more requests for machines with pallet pools for lights-out and lean operations. For HMCs we are developing a six-pallet-pool system that will be a bolt-on addition to our EC-400. We plan to make it retrofittable in the field.

"Because many of our customers now have to produce a wider variety of products, they are asking for larger toolchangers. Our HMCs come standard with a 24-tool magazine, but both a 40-pocket and 70-pocket toolchanger are available as options. The extra tools are needed for backup tooling and to run multiple jobs.

"We are also stressing rapid delivery. We are currently producing more than 825 machines each month, and most products can be delivered in two to three weeks."

"Our driven at the center of gravity (DCG) drive design for both HMCs and VMCs is a big factor in improving productivity and reducing tool cost," says David Austin, team leader, Mori Seiki USA Inc. (Irving, TX). "Although a DCG machine may require a higher initial investment, depending upon the technology it is compared to, there is a greater savings on tooling and the customer is able to make more parts per unit of time. Because of reduced vibration, we see tool life increases of about 30%. In the DCG concept, the ballscrew drives the table or head at the center of its mass, not from an offset position. As a result, there is no twisting action during acceleration and deceleration. In addition to extended tool life, the result is better part finish and accuracy.

"As manufacturers gain experience and become educated about the advantages of HMCs, they gain in popularity. Because you can mount parts on a tombstone that has rotational positioning, you can do a job in one setup instead of two or three. For even greater production speed, adding a pallet system eliminates setup time.

"Some don't realize the importance of an automatic pallet changer," explains Austin. "A VMC has flexibility and is easily set up, but the machine is not running during setup. You can commonly find VMCs with only about 10% spindle utilization. With the HMC you have one pallet in process while the other pallet is being set up. This typically means an increase of 30 - 50% spindle utilization. If you double spindle utilization, you have essentially added a machine to your operation.

"Then, if you have a pallet system, such as one with 8 to 24 pallets, you also take the repeatability problem caused by fixture mounting out of consideration, because the fixtures remain on the pallets between jobs. And with pallet systems we see users with 85% spindle utilization and zero setup time.

"There is less deflection in the upper end of the cutting range, so we can cut reliably over the entire machining envelope. Tooling savings can be 30% or more, and in some cases are even doubled due to minimized vibration."

Mal Sudhakar, vice president, Mikron (Monroe, CT) sees these trends driving changes in machining center/cell technology. High-speed machining is characterized by cutting speeds that are five to ten times higher than conventional machining, which requires higher spindle speeds, feed rates, and acceleration on machining centers. A few years ago, machining centers had top spindle speeds of 8000 rpm, feed rates of 400 ipm (10 m/min) and acceleration of 0.1 or 0.2 g. Today, many high-performance machining centers are available in the market with spindle speeds up to 20,000 rpm, feed rates of 1600 ipm (41 m/min) and acceleration of 0.5 g. A further step above this are high-speed machining centers with spindle speeds to 60,000 rpm, feed rates of 300 ipm (7.6 m/min) and acceleration of 1 g and higher.

Multiprocessing combines more operations on one machine. While turn/mill centers are offering more capabilities and becoming more prevalent, the use of five-axis machining centers is also increasing. Five-axis machining centers provide the capability of multisided machining in one setup.

"Automation is a way to cut labor costs and achieve the maximum possible output of a machine to generate the highest revenue per employee," says Sudhakar. "Machining centers today are therefore being designed for automation, offering integrated multistation pallet changers or the capability of being easily interfaced with a robot."

Smart machining is a new technology developed to bring intelligence to the machining process to improve reliability, optimize machining performance, and allow dependable unmanned operation. Examples of smart machining technology are real-time monitoring of spindle vibration in a high-speed machining process, intelligent thermal control to automatically compensate for thermal drift in a machine, and communication of the operating status of a machine from the CNC to a PC or cell phone.

Mikron is addressing these trends by offering a wide range of high-speed and high-performance machining in a variety of three to five-axis configurations. Spindle speeds up to 60,000 rpm and axis acceleration of over 1 g are available. All machines offer an integrated pallet changer for easy interface with a robot. For example, the UCP 600 Vario machining center has a 21.5-hp (16-kW), 20,000-rpm spindle, a versatile rotary/tilt table for five-axis/five-sided machining, a laser tool-measuring system, a part probe, an integrated table chuck for palletization, an integrated seven-position pallet changer, and smart machining modules for vibration monitoring and intelligent thermal control.

Automation is a way for manufacturers to take advantage of multishift operations. Today, this is true even with complex parts that are typically produced in short-to-medium runs. Hermle Machine Co. (Franklin, WI) has responded to the demand for greater production capability with developments such as the C-series, which has a selection of fixturing devices to facilitate multiple-part production. The pallet changer permits automatic operation or allows for operator intervention. The company is also partnering with Erowa (Arlington Hts., IL) in creating production systems that wed one or more Hermle machining centers to an Erowa unit that delivers extended pallet or workpiece-handling capability.

"A flexible clamping system has been integrated into the X axis of our machines," explains Doug Gale, Handtmann CNC Technologies (Buffalo Grove, IL). "This eliminates the need for hard tooling and speeds setup, which means big gains in changeover time. With big gantries we can changeover in only 10 min. All we have to do is change our vise blocks to adapt to a different part. For example, we can easily go from a T-shaped extrusion to a J-shaped one."

Handtmann is a company that specializes in handling large material sections. Their machine can make either one large part such as a wing spar or a number of small parts from a single workpiece. "We have five-axis capability and flexible clamping, we can get to everything, then cut-to-fit in one setup. You just need a program change to change parts," says Gale. "We can cut the same part, mirror parts, or several different parts from one workpiece."

With machining cells and centers, customers are demanding a more complete single-source supplier, to help control their project costs. "They have found that by requiring their suppliers to have partnerships with various other suppliers, customers can reduce lead-times and avoid logistics/communication complications that occur when working with multiple suppliers on one program," says Bill Beck, general manager, Chiron America Inc. (Charlotte, NC).

"What is most important is the ability of the manufacturing process to put completed parts or products in the box of sufficient quality that they can be shipped to the customer. There is nothing to sell unless the products are produced. Unfortunately, companies locked into the capital equipment dilemma have a difficult time achieving this in that they are working with older, inefficient technology.

"To meet the needs of our customers, Chiron America Inc. formed Chiron Global Systems Group. Its approach includes the Cost per Part program that allows customers to upgrade their manufacturing process. The Global Systems Group designs systems to help transition customers from high-volume, single-mode manufacturing to solutions. This transition minimizes single-mode failures and generates greater productivity."

For complex, high-tolerance parts customers of Okuma & Howa (Buffalo Grove, IL) are calling for increased production of five-axis machines. Parts of this type have become more common and, because of their critical nature, they are not generally outsourced to overseas manufacturers.

The Okuma & Howa product line offers a dual-spindle configuration, equipped with gantry or other automatic parts loaders, providing production that can×t be matched by single-spindle machines. Their larger vertical turning machines have multiaxis capability for generating difficult profiles on parts ranging from aircraft wing components to specialized valves. The rapid traverse speeds are among the fastest in the industry, and most machines are available with optional high-speed spindles. O&H has flame-hardened box ways that contribute to both high precision and long life.

"One of our most versatile machines is the MultiDECO 32/6c, says Thomas Dierks, president, Tornos Technologies (Brookfield, CT) "It's a CNC multispindle machine for higher volume parts, chiefly automotive. A typical run is 100,000 pieces or more. Since it is a CNC machine and it uses standard insert-type tooling, setup and changeover are much faster than on a cam multispindle. It can handle parts in the range 1/2 to 1.25" [13 to 32-mm] diam and 4 to 5" [102 to 127-mm] long. In general, there is a trend toward smaller and several parts being combined into one part. That often means fewer, but more complex parts, with tighter tolerances."

This machine is specifically designed to provide more backwork capability. There are six spindles working on the front side of the part. Initially there may be rough turning, finish turning, threading, boring, cross holes, and flats. When the front end of the part is finished, it is picked up by a subspindle and presented to five additional tools for working on the back side of the part. Work on the back side of the part can be nearly as complex as the work performed on the front of the part with operations like drilling, boring, threading, cross holes, milled flats and slots. Ideally, you want to perform all operations in a single machine with a single setup. This machine has five tools for back work and all are live, which allows the operator the possibility of eliminating secondary operations.

After the part is machined, a pick-and-place device pulls the part from the machine and places it in a tray. Because of the small part size and high precision involved, handling is critical to maintaining part integrity.

"Fadal Machining Centers [Chatsworth, CA] offers the VMC 4020 with a moldmaking package that includes a GE Fanuc Series 18i MB5 controller, box way construction, Cool Power refrigerated cooling system to control thermal growth, and standard 10,000-pm spindle that allows hogging and finishing of large molds on the same machine," explains Dan Gustafson. "This eliminates the need for dedicated hogging and finishing machine tools. The Z-axis box way column minimizes side thrust deflection inherent in low-cost large machines using linear guides."

The Series18i MB5 controller includes such features specifically intended for moldmaking as Artificial Intelligence Contour Control (AICC) and Machine Condition Selector, which provides an R1-10 value selection for controlling both velocity and accuracy, allowing them to be balanced based on the toolpath. Options include Mold 3 and Mold 5 packages based on processing-power requirements.

This controller eliminates bottlenecks, and reduces machine-tool cycle time with a fast processor and PCMCIA memory card. With support for NURBS curve interpolation, the Series 18i MB5 controller delivers high-speed, high-precision machining for parts, molds and dies.

The CoolPower refrigerated cooling system minimizes thermal growth along the ballscrew to maintain positioning accuracy during extended machining of large and complex molds. Thermal drift is a major problem during machining operations, which can require 30 or more hours. Heat buildup in the ballscrew causes positioning drift from the beginning to the end of machining. By maintaining a constant temperature, positioning drift is minimized and positioning accuracy ensured.

The temperature of the heat-transfer agent is monitored and chilled as required, maintaining the temperature of positioning components within ±1.0ºF of the VMC's ambient temperature to control thermal expansion. The system is closed-loop, isolating the heat transfer agent from chips and other contaminants.

According to William Vejnovic, VP of engineering , Toyoda Machinery USA (Arlington Hts., IL). "In general, Toyoda has several features that separate Toyoda from other machine builders: Our spindles are extremely rigid due to larger-than-typical housing/bearing diameters as well as designs that locate the spindle bearing sets closer to the spindle gage line. Our 15,000-rpm direct-drive spindle uses an automatically adjustable spindle-bearing preload system that applies maximum preload at low RPM and automatically reduces preload at high rpm. This system allows our machines to run at full rpm 24/7 with no spindle-speed duty rating. Our box-way machines have rapid/max. feed rates up to 1890 ipm (48 m/min ) our linear-roller-way machines have feed rates up to 2363 ipm (60 m/min). A proprietary part-contact sensing system integrated into the spindle detects broken tools, and provides part probing in one package. Broken-tool detection and gap elimination occur while in cycle, requiring no wasted cycle time to use a typical tool-check device. On our Fanuc 30i-controlled machines we have incorporated X,Y and Z-axis gap sensors that measure and compensate for ballscrew growth due to thermal expansion.

"With our cell systems, our concept is modularity. A stand-alone machine can in the future easily be converted to a remotely guided vehicle (RGV) machine, tool magazines can be changed out and expanded in the field and if the customer's work statement changes we can field-retrofit higher or lower-RPM spindle assemblies. Single-level or multilevel RGVs, which can be fully expanded in the future, allow the addition of machines, pallet buffer racks, and loading stations. However many pallets the system is configured for, we can manage an additional 300 pallets offline, and single or multilevel pallet pools offer a wide array of cellular concepts. Toyoda's own PC-based cell controller software, operating under Windows XP, provides flexible work management and scheduling, and also offers as an option true dynamic scheduling that is capable of tying into MRP systems for true lean manufacturing. We find that our software package is usually the driving force in securing business when potential customers are looking at cells and FMSs."

"We are definitely getting more inquiries about HMCs" explains Cari Vanik, Kitamura Machinery USA Inc. (Wheeling, IL). "Customers are being better educated on the advantages of this type of machine. That means improved spindle cutting time and therefore improved productivity. In addition, the HMC generally has reduced setup time and the ability to machine multiple parts.

"Complex high-precision parts can be profitably run on short notice and in low volume. There has also been a dramatic increase in inquiries for multisystem cells that either incorporate a few different stand-alone multipallet machines or more of a flexible machining system. With these machine configurations, the customer uses a stacker type of pallet system where they can add machines or pallet configurations down the road. This saves setup time, offers unmanned machining possibilities, and cuts delivery time. These systems work not only for large, but also for midsized and smaller job shops.

"The demands of the medical industry have created the need for greater accuracies in machining. If customers want to take advantage of this market and keep it in this country, they will have to update their equipment to reflect today's technology.

"To meet customer needs, we have offered a wide range of HMCs for some time, and within the past two years we have been putting more focus on the multipallet systems and cells. We currently offer both and have installed these systems at a variety of customers. We introduced our new "F"-Series machining center line (both verticals and horizontals). Key features include accuracies of ±0.00008" (0.002 mm) full stroke and repeatability of ±0.00004" (0.001 mm). With our machines, they are able to do a wide range of work from general machining to mold work on one machine. Spindle speeds of up to 20,000 rpm with a four-step gear-driven, dual-contact spindle system gives the ability to handle tough cuts with fine-finish capabilities. They have solid box-way construction and feed rates to 1969 ipm (50 m/min).

"We have also introduced our Mytrunnion five-axis machining center with standard glass scales and accuracies of ±0.00004" for complex parts requiring high accuracies and precision mold jobs."

"We are going after one of the two surviving markets in the US," says Scott Walker, Mitsui Seiki (Franklin Lakes, NJ). "The first is the lowest-cost parts producer incorporating engineered automation for not-too-precise parts. The other, the one we are after, is the high end, with the highest-tolerance requirements.

"So each day we are seeing another round of 'Oh my God' specifications. We are being pushed to build machines with tighter accuracies, not only three-axis machines, but four, five or more.

"With three axis you worry about straightness and perpendicularity for tight volumetric accuracy. But when you incorporate rotational axes of motion you have a different set of problems. There are inherent inaccuracies that are more difficult to take out. We have to provide digital resolutions of 0.001 µm while the control is operating five axes simultaneously.

"For example, we provided optical housings for a one-setup process. You could not touch the part or it would kill the accuracy.

"Another challenge is the new-generation jet engines. They are producing higher thrust and are made of new, hard-to-machine materials that require machine approaches never used before. Also, it's necessary to have tighter tolerances to provide better fuel efficiencies.

"Another trend is the 'green issues' such as floor space and energy costs. To achieve smaller floor space, we have to go to a stiffer machine. There is also a drive for lubrication for life to simplify maintenance problems."

Delivery is critical. "Technology, although always important, is not the only issue right now, it's providing the machine the customer wants, when they want it," explains Kevin Bevan, president, GBI Cincinnati Inc. (Cincinnati, OH). "There is a lot of pent-up demand out there, and those machine tool builders who ramped down too drastically can't meet customer demands.

"There is also a strong push to eliminate, or more effectively use, labor. Manufacturers want employees who are providing eight hours of 'value added,' not reading newspapers half the time. As a result, companies that before would have bought two or three single-purpose machines, each requiring an operator, are going for more complex cells that can be run by one person."

GBI'S product line takes advantage of both these trends. Currently, their best-selling machine is a FTV (fixed table, vertical) from Cincinnati-Lamb. It's available in both three and five-axis versions. One of the key benefits this machine offers is its flexibility and versatility. There are many ways to configure a setup.

"We are also offering a complete line of commodity-type machines from Feeler," explains Bevan. "They range from simple two-axis lathes to double-column milling machines. Although they are, for some, entry-level products, they have a lot of automation capabilities that can keep down labor costs. This includes features such as a built-in pallet system, pick-and-place loading, and conveyor systems. We offer a kind of a 'cell out of the box', " Bevan concludes.

Stand-alone equipment provides a lot of versatility. The Ultra ZV500 CNC VMC from NTC America (Farmington Hills, MI) is a stand-alone machine designed for heavy-duty, high-productivity operation. A 25-hp (18.5-kW) motor gives the spindle a top speed of 12,000 rpm. The spindle is a double-cartridge design for easy maintenance or a change in capability to a CAT 40, BT40, or HSK A63 taper. The magazine carries 25 tools.

Coolant can be sent through the spindle center at 1000 psi (7 MPa). Maximum tool diameter is 80 mm with an optional 180-mm unit. The work envelope can accommodate large parts. The XYZ work envelope is 44 X 22 X 22" (1120 X 560 X 560 mm).

The ZV 5000 has a positioning accuracy of ±0.01 mm over 300 mm, a repeatability of ±0.003 mm, and a roundness accuracy of 2.6 µm.

"Our business is primarily providing medium to high-volume automotive part manufacturing systems using modular transfer machines or agile manufacturing systems such as those used to make major engine and transmission components," explains Ron Quaile, vice president, Cross Huller North America (Sterling Heights, MI). "To provide a cost effective balance of flexibility and low-cost manufacturing, customers are going to hybrid systems using transfer lines for the initial heavy milling and boring operations, and for finish-machining operations. CNCs are then used to handle part variations. Our agile systems are built around Cross Huller's four-axis SPECHT CNC module arranged in small automated cells or larger modules of 30 - 45 machines with automated gantry loading.

"We are moving away from rigid customer specifications and going to more standardized designs, including everything from controls to fluids. The use of Cross Huller standards eliminates specialty engineering, increases the use of proven standard components and, overall, that means lower cost, shorter delivery times and improved machine reliability and maintainability. Typical of these designs are the direct-loaded Star 500 CNC machine. This machine is in the same product family as the new Bluestar 5 series of machines from, but is modified for use in an automated agile system.

"Because of production volatility, many production-part suppliers are staying away from the large hard-tooled systems. For these smaller companies, the trend is toward lines made up of cells of three or four machines, usually with a pallet-swapping system, or for larger production volumes, agile systems with CNCs and overhead automated gantry-loading systems. We have 'batch of one' capability.

"Some of the larger, more sophisticated customers want minimum quantity lubrication to eliminate mist and individual cooling systems on machines. There is a cost advantage to eliminating large central systems, and there's also less chance of environmental problems. To further reduce cost and improve line efficiency, we group chip-handling with several machines on one system.

"Linear motors are still not cost-effective enough. They have both a high initial and high life-cycle cost. However, every job is process dependent and we will offer them when practical. In the more complex machine operations requiring high-accuracy circular interpolation, Cross Huller will offer its new Genius 500 machine, which combines a parallel kinematic linkage mechanism with a linear motor and provides a lot of stiffness--even enough for nodular-iron machining.

"Our products are best suited for low-to-medium production volumes," says Ken Campshure, Giddings & Lewis (Fond du Lac, WI). "We find that the smaller shops are becoming more interested in material handling and HMCs for their added flexibility. To be able to work on four part faces is clearly a benefit. There is also a growing interest in twin-spindle machines, although the acceptance is not as great in the US as it is in Europe."

 

This article was first published in the June 2005 edition of Manufacturing Engineering magazine. 


Published Date : 6/1/2005

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