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Shop Solutions: CAM Boosts Turbine Engineering

 
Turbine Technologies PT-50 turboshaft 50-hp (37-kW) engine packs plenty of power into a flight-ready weight of 30.6 lb (14 kg) for Unmanned Aerial Vehicles.In most companies, engineering departments support manufacturing operations. Turbine Technologies Ltd. (Chetek, WI) is different—the mission of its machine shop is to support the engineering function.

Instead of thinking in terms of shrinking the "time to market," Turbine Technologies focuses on compressing "time to test." This is particularly true for its newest product, the PT-50 turboshaft engine for UAVs (Unmanned Aerial Vehicles). With its minimal volume and a complete flight-ready weight of only 30.6 lb (14 kg), the engine offers a heavy-fuel solution for UAVs requiring a 50-hp (37-kW) class engine.   

The company is in a race to refine the product to fit specific real-world military and other applications. Many of these refinements start out using high-end engineering software programs, which optimize such things as compressible fluid flow dynamics. Ultimately, the prototype components must be manufactured for rig testing, data evaluation, and subsequent refinement.

To make sure that this practical problem of manufacturing physical components does not become a bottleneck for engineering throughput, the company recently invested in advanced simultaneous five-axis machining equipment and CAM software.

The PT-50 engine was a logical extension of the company's traditional business, explains Mike Kutrieb, vice president. The company designs and builds Turbine MiniLabs, which are used to teach undergraduate students engineering fundamentals in miniature environments that simulate real-world gas turbines, steam turbine power plants, and centrifugal pumping stations.

Several years ago, Honeywell International executives were impressed enough by the Gas Turbine MiniLab engine design to ask if Turbine Technologies would be interested in developing a version of the engine for the OAV-2 (Organic Aerial Vehicle) program as part of the primary contractor's involvement in the Army's Future Combat Systems program. Turbine Technologies agreed, and the result of this effort was the PT-50.

Turbine Technologies is now under contract with the US Army Aviation and Missile Command (AMCOM; Huntsville, AL) to support the engine's continuous development and testing. The goal of the project is to develop a long-lasting, ultra-lightweight turbine engine that will provide a power takeoff at 4000 rpm and run on economical and readily available JP8 heavy fuel.

At this writing, the engine is currently undergoing endurance testing on a test stand where the goal is to obtain 250 hr of operational data. "Once that has been achieved," says Kutrieb, "there are many different applications we can move into—anywhere from driving a generator or fire-fighting pump to being installed in fixed and rotary-wing UAV designs."

Having excellent design and engineering capabilities was essential to getting a foot in the door of this business. Just as important, however, was the fact that Turbine Technologies was able to manufacture and assemble its own components at a cost that was not only competitive with domestic competitors but also less than outsourcing from overseas.Optimal toolpaths pop out of the box in Turbine Technologies' prototyping environment using Mastercam CAD/CAM software to seamlessly recreate the design intent of SolidWorks files.

Because manufacturing capabilities afforded an obvious competitive advantage, Turbine Technologies launched an initiative to take them even further. Of particular interest was improving prototyping turnarounds by taking some of the complex components that were being manufactured in the company's vacuum investment casting foundry and manufacturing them on a VF-2 five-axis VMC from Haas Automation Inc. (Oxnard, CA).

Obtaining the right CAM software to enable CNC programmers to create toolpaths for complex geometries that faithfully reproduced the design intent was critical. Turbine Technologies chose Mastercam X2 CAD/CAM software from CNC Software (Tolland, CT). The moldmaker hired to work with the five-axis VMC was familiar with the strengths and weaknesses of many CAD brands, and was confident in the choice of Mastercam for this application.

Another plus was the close proximity of Chippewa Valley Technical College (less than 30 miles away), which provides training on CNC machines and CAM software identical to what is used at Turbine Technologies. The company has been sponsoring interns from this program, and this relationship should make it easier to acquire young workers with appropriate skill sets as the company grows.

It used to take 2 1/2 weeks or more to make turbine parts like this using a vacuum investment casting foundry. With Mastercam software and five-axis machining, it now requires just a few days."Not everything can be machined. Some of these super alloys are difficult to machine, and we can't even get a cutter into some of the passages we create," Kutrieb says. "There are high-temperature components where we have no other method but the casting process." With its five-axis machining capability and Mastercam CAD/CAM, the company has been able to pull a lot of work back into the machine shop.

To create prototype parts for a turbine engine, the engineer typically starts by using ANSYS software to generate geometry in combination with flow analysis. The part is then typically moved to SolidWorks for solid modeling, and then to Mastercam, where the part is opened seamlessly as a Parasolid or an IGES file.

The real trick to moving a prototype part along expeditiously is being able to select an optimal toolpath for creating the complex, modern-art-like geometries found in axial blades, centrifugal impellers, diffusers, and the like. Whereas manufacturers can spend a great deal of time shaving seconds from the manufacturing cycle, an engineering company needs to be able to pick a toolpath out of the box, refining specific areas only infrequently to ensure the preservation of critical characteristics.

Mastercam X2 software was instrumental in moving from design to investment casting to get a part for testing. Kutrieb cites the example of a diffuser that was recently programmed for five-axis machining. "On average, if things go smoothly, it might take two and a half week to move this part from design through the investment casting process to get a part for testing. With the Mastercam and five-axis CNC machining, this part and others like it are being turned around in several days, improving turnaround time and keeping pace with our aggressive production development and testing schedules."

Of course, there may come a time when the company becomes more production-oriented, and trimming seconds here and there from various CNC operations will become much more important. Test results indicate that the turboshaft engine design could have a life expectancy as much as ten times greater than gasoline-driven piston engines. Given the right application and the right numbers, this performance could make the product very cost competitive.

Turbine Technologies is betting on this promising possibility. It has augmented its initial 9000 ft2 (836 m2) by acquiring an additional 32,000 ft2 (2973 m2) of space for future expansion. If that's not enough, the company also owns a seven-acre (2.8-hectare) site. But for right now, the focus is on expeditious engineering.

"These machines do exactly what we ask of them. We've made the right investment and more important, the guys in the shop are very happy. The operators and setup guys find them very easy to work in and around. Lots of access and design simplicity make for very fast changeovers."   

Rural Job Shop Work Expands

Whitworth Tool Die & Stamping (Hardinsburg, KY) employs more than 200 skilled workers and an array of production equipment, including 16 Okuma CNC horizontal turning centers.

Founder Kenny Whitworth describes his Okuma machines as "top notch." That sentiment is shared by Whitworth's production manager, Tom Dyer.

Whitworth Tool began as a family business in Kenny Whitworth's garage in the spring of 1998. His goal was to build a tool and die company that provided the highest quality service at a speed that would meet his customers' needs.

Once Kenny and his son, Jared, began producing products for their customers, word got out and demand grew to become more than two people could handle. More equipment and more employees were added to cover the workload. It quickly became apparent that the garage was not big enough to accommodate the rapidly growing business.

         A Marposs Quickset modular bench gage at Whitworth Tool is used to measure finish-machined cross trunnion parts produced on two Okuma L370 turning centers. Measurement data from the gage are processed and stored via the Marposs Quick SPC statistical software on the Okuma THINC control.

In October 1999, Whitworth Tool moved into an 8800 ft2 (817-m2) facility, which would allow the business to flourish and expand. During this time, the company began providing more services such as die maintenance, reverse engineering, and small-scale production work. These new services, along with its core services, allowed Whitworth Tool continued growth at a steady rate. Within a few years, it was clear that the current facilities were too small to accommodate continued expansion.

In September 2002, Whitworth Tool moved to a 39,000 ft2 (3623 m2) where the company operates more than 100 machines, running 24/7. The company has also added more services to meet its customers' needs. New services include press spotting, CMM certification, and large-scale production work.

 

Operators are guided through the measurement sequence by visual prompts on the THINC control. A color-coded graphical display provides an instant visual check of part quality.

"More than 90% of the production in our turning department is done on Okuma lathes," Dyer points out. "So, when one of our customers cut the tolerance on a part we'd been producing to ±0.002" [0.05 mm] from ±0.010" [0.25 mm], one of the things I did was visit the Okuma Partners in THINC Center in Charlotte, NC.

"There I saw the integration of Marposs' Quick SPC software into the Okuma THINC control. That, and the Marposs Quick Set modular gage, were exactly what we needed. Being able to see them work in a real-world environment at the center made the decision to bring the technology into our plant very simple," Dyer adds.

The part is a cross trunnion used in the rear axle of heavy-duty trucks. It has four cylindrical legs attached to a center section, very much like the center cross of an automotive universal joint. The trunnions are machined from forgings on a pair of Okuma L370 CNC horizontal turning centers at the rate of 700 per day.

Whitworth installed the Marposs Quick Set gage between the two machines, and installed the Quick SPC software in one of the THINC controls. Marposs Quick SPC software is a statistical process control and quality management package that runs on a PC or PC-based control using the Windows operating system. It includes the Q-DAS statistical package and fully-compliant qs-STAT data storage.

The modular Quick Set gage measures the length of the legs and two diameters. The part is then turned 90° to measure the other pair of legs. This entire operation is completed in a few seconds, enabling one operator to tend both machines.

Gage readings are automatically fed to the Quick SPC software. Results are displayed as a green, yellow, or red bar indicating a part meeting specifications, a part nearing the tolerance limits, or a part out-of-tolerance. Marposs also supplied a Visual Work Instruction including a graphic representation of the part.

"We tried it on one machine," Dyer says, "and it worked so well we quickly started collecting data from both of them. We're inspecting every part and capturing all of the data. The customer has not asked for it, but if they ever do we can provide complete traceability for all of the parts.

"The only way it could work better is if the whole process was automated, and that's already being planned, along with the implementation of the Quick SPC software's ability to automatically update the machine control with realtime feedback," Dyer says.

"We've seen that work in Charlotte, too," Dyer says. "So we know it will work here in Hardinsburg."

Nanometer Measuring Gets Stable Platform

When OptiPro Systems (Ontario, NY), a leading manufacturer of CNC optical manufacturing technology, needed ultra-accurate and stable positioning for a new system for measurement of conformal optics, it turned to ABTech Manufacturing Inc. (Swanzey, NH), specialists in custom-made ultraprecision air bearings and motion systems.

ABTech designs and manufactures rotary and linear ultraprecision motion products for aircraft and aerospace; optical; semi-conductor and other high-tech research, metrology and production applications. It specializes in friction-free, low-maintenance hydrostatic air bearings with sub-micron accuracy and extreme load and stiffness capabilities. In addition to air bearings, it has developed numerous oil hydrostatic and high-precision mechanical bearing options.

 

Five-axis system using Renishaw air bearings and encoders was jointly developed by ABTech with its customer for high-level automated measurement process feedback in production of lens optics.

Using OptiPro's concept as the framework, ABTech applied its expertise in ultraprecision, multiaxis motion and its understanding of complex geometric measurement principles to design and manufacture a five-axis air-bearing optical metrology platform.

To meet tighter specifications for positioning resolution, ABTech selected high-resolution linear and rotary optical encoders from Renishaw Inc. (Hoffman Estates, IL). The company created a five-axis optical measurement platform featuring three ABTech linear air bearings, two ABTech rotary air bearings, and Renishaw's ultra-high accuracy Signum series linear and rotary encoders.

"This was a joint development project with our customer," says Ken Abbott, ABTech's president. "They developed the concept, controller, and software, while ABTech designed and built the mechanical system—the multiaxis air-bearing platform."

In operation, a lens is placed on a high-precision B-axis rotary table for measurement by a non-contact confocal imaging probe mounted horizontally on a rotary C-axis air bearing. Confocal imaging performs micro-topographic mapping of the lens geometry and surface.

The system requires that the confocal probe be positioned normal (perpendicular) to each surface point to be measured. The platform created by ABTech accomplishes the exacting repositioning by coordinated motion in up to five axes. The next-generation CNC optics inspection system requires position resolution of 5 nm for the three linear axes. Resolution for rotary motion is 0.009 arc-second/count for the C-axis and 0.018 arc-second/count for the B-axis. Fully programmable 32-bit Windows-based measuring software drives the noncontact probe to automatically collect micro-topographic data.

Overall volumetric system accuracy is mapped and corrected by the customer, so position repeatability and thermal stability were the most important demands on us for this application," says Abbott. ABTech's requirements for individual axis position accuracy were:

  • Linear: ±1 µm over full travel of 8" (203 mm)
  • Rotary: ±1 arcsec total error over a 360° move

Renishaw recommended an advanced Signum rotary and linear system, a high-performance dual-readhead DSi rotary encoder, and the RELM high-accuracy linear encoder. These Signum encoders provide accuracy better than ±1 µm, ±30 nm cyclic error, and resolution down to 5 nm/0.005 arc-second. Dynamic signal control enables the 20 µm scale position encoders to offer fine-pitch performance without the fragility and optical cleanliness constraints of glass encoders. The encoders provide dependability in manufacturing environments with high tolerance of shock, vibration, and temperature to 85° C.

Especially important to ABTech, the RELM linear encoder system features a scale of stabilized Invar. This nickel/iron alloy offers exceptionally low coefficient of expansion. "This being a metrology system, we were most concerned about thermal stability," says Abbott. "Most of the machine is fabricated from stainless, granite, and ceramic to minimize thermal growth. The Invar scales were a perfect fit for this application."

Physical size was key factor in selecting position encoders. "The encoder needs to be small," Abbott emphasizes. The 20 µm Invar scale met those needs with a smaller cross section than glass scales of just 1.5 x 15 mm, along with easier handling and installation without risk of breakage.

The scale incorporates Renishaw's In-Trac optical reference mark, providing a bidirectionally repeatable datum point across the entire speed and temperature range without increasing overall system width. Dual optical limits are also available as position markers to indicate end of travel.

For rotary position accuracy, ABTech selected the DSi (Dual SiGNUM interface) and REXM rotary encoder system, Renishaw's highest accuracy Signum rotary encoders. Capable of total installed accuracy of better than ±1 arc second, the DSi configuration combines two error-correcting Signum SR readheads with an ultra-high-accuracy REXM ring/scale and provides a customer-selectable propoZ reference (index) position, which is completely unaffected by bearing wander or power cycling.

Located in 180° opposition, the two readheads cancel out odd error harmonics, including eccentricity, and compensate for the effect of bearing wander. By combining the incremental signals from the two Signum readheads and using Renishaw's reference mark processing, the DSi appears to the controller as a single high-accuracy encoder.

The other element in the accuracy equation, the REXM ring, features a thick cross-section to minimize all installation errors except eccentricity, which is corrected by the DSi. Once the interface has eliminated the effects of eccentricity, the only significant errors remaining are minor, even-harmonic distortions in installation, graduation, and cyclic error (sub-divisional error—SDE).

These are exceedingly small, as low as ±0.5 arc second and ±0.03 arc second respectively. When the REXM ring is used with the DSi, it is possible to realize a total installed accuracy of better than ±1 arc second.

The linear and rotary encoders share Signum encoder design features, including IP64 sealed readheads, dynamic signal processing for reliability, and ultra-low cyclic error (±30 nm). Renishaw optics scan and average the contributions from many scale periods, and effectively filter out nonperiodic features such as dust, dirt and other contamination. The noncontact readheads ride above the scale, thus eliminating friction, hysteresis, and wear.

         Rotary ring encoder from Renishaw enables resolution to 0.018 arc-second/count for B-axis rotary table. Dual readheads cancel out eccentricities, while direct mounting of the ring on the table rotor eliminates reversal errors, coupling losses, and other hysteresis errors.

Renishaw's compact readhead design met ABTech's tight size constraints. While the five-axis platform is substantial at 53" wide, 38" deep and 66" tall (1349 x 965 x 1676 mm), the individual axes are packed full of motors, encoders and air bearing surfaces. Abbott says, "The small size of the Renishaw package allows us to maximize the size of our air bearing pads, which is critical to achieving high stiffness and accuracy."

The linear and rotary encoders share the same miniaturized readheads, just 14.8 x 36 x 16.5 mm, while the RELM scale is just 15 mm wide and the REXM scale only 10 mm.

PC-based Signum software provides calibration and setup optimization with real-time diagnostics. Analysis of the Signum Si interface is available to users at all times, providing information on system configuration such as resolution, clock frequency, error, and warning outputs.

The software simplifies installation of the encoder, and provides an indicator that enables fine adjustment of the readhead pitch angle, which is useful for readhead setup on small-diameter rings. Integral LEDs on the readhead and interface provide quick, visual feedback to help optimize setup and real-time system diagnosis.

The new optics measuring system is ABTech's first project with this customer and is expected to become a production item in the customer's catalog, providing a welcome on-going business relationship for the New Hampshire company.

 

Invest to Grow with Your Customers

The operating strategy of Jerry Broughman, president and CEO of Controlled Turning Inc. (CTI; Jackson, MI) and his wife Carol hasn't changed since the company opened more than 30 years ago.

Invest wisely to meet demand. Update equipment (controls) regularly. Don't lock your focus on a single industry. Grow with your customers; grow as they grow. Keep up with technology, and respect your workforce.

Today, the company has 26 employees and occupies 8000 ft2 (743 m2) and operates a variety of CNC turning and milling equipment, mostly for short run jobs. Last year, for example, some 40,000 different types of parts went through the shop, representing a lot of variety, diversity, and changeover.

"Our growth is slow on purpose," Broughman says. "We like to grow in step with our customers' needs. We're not the kind of operation that throws money at things and hopes something works. We take our lead from our customers."

The company manufactures tooling for the auto industry, as well as hydraulic and pneumatic components and medical and dental components. Materials machined include just about all forms of ferrous and nonferrous material, mild steel, medium alloys, stainless, tool steels, brass, aluminium, and plastic.

"When we pick up a new customer, we grow to fill his needs at that moment," says Broughman. "Our plans for this coming year are to expand by 3000 ft2 (278 m2), provided that the growth is still there. We were going to do this last year, but we ran out of time, and then the weather got to us."

 

At Controlled Turning the Feeler FV-760 VMC is machining parts up to a 18" (457-mm) cube for a variety of short-run applications.

When it comes to upgrading technology, that's a different issue entirely. Broughman says they're constantly looking at new equipment, both as additions and replacements. And they replace controls on a regular basis. "We use nothing but Fanuc controls and drives," he says, "and Fanuc offers an update every year. We update about every four or five years."

It has been two to three years since Broughman bought three machines, a Feeler FV-760 CNC VMC and two Feeler FTC-20 CNC turning centers from GBI Cincinnati Inc. (Cincinnati).

"We had a relationship with Methods and Equipment [Livonia, MI] going back to 1985, and we always called them in when we needed something new," says Broughman. "When they began representing GBI Cincinnati, we were introduced to the Feeler line of machines. We needed some additional capacity in turning and milling, and the company suggested we try the Feelers, and we did, and they've been performing perfectly since."

What Broughman bought from GBI was a Feeler FV-760, a 40-taper, 10-hp (7.5-kW), 8000-rpm VMC with 30 x 16.5 x 20" (762 x 419 x 508 mm) in X-Y-Z axes and linear guideways. Table size is 35 x 16.5" (889 x 419 mm) with a 660 lb (299-kg) load capacity. Rapids are 944 ipm (X, Y, and Z); positioning accuracy, ±0.0004" (0.010 mm), and repeatability ±0.0002" (0.005 mm). The 18-tool carousel has a tool-to-tool change of 7 sec.

The two FTC-20 CNC turning centers have an 8" (203-mm) diam chuck, and are rated at 20 hp (15-kW) and 4500 rpm with a spindle bore of 2.44" (62 mm) and a bar capacity of 2.04" (52 mm). Travels are 7.9" (201 mm) in X and 14.96" (380 mm) in Z with rapids of 944 ipm (24 m/min) in X, Z and repeatability of ±0.00012" (0.0030 mm) in X and ±0.0002" (0.005 mm) in Z. The FTC-20s feature linear guideways and a max swing over bed of 22" (559 mm). Max turning diameter is 13.8" (350 mm), and turning length is 13.5" (343 mm).

The Feelers have been running 20 hr a day since they were installed. The company runs two, 10-hr shifts five days a week and two six-hr shifts on Saturday. "The Feelers are very compact. They have a very small footprint, which is one of the things we need in a machine," says Broughman. We pack our machines in wall-to-wall and waste very little space. So, the compact size, plus the rigidity and the stability—they have a very good cast iron base, good rigidity, and overall the CNC Feelers have worked out fine. They're real performers."

Two Feeler FTC-20 CNC turning centers consistently hold close tolerances and produce fine surface finishes.CTI runs parts from 1 to 15" (25–381 mm) in diam on the CNC FTC-20s and anything up to 18" (457-mm) cube on the CNC FV-760. "We're holding 0.0004" [0.010 mm] on turned parts," he says, "and our hole patterns on the mill have been within a 0.0001" [0.003 mm], point-to-point, at all times. Surface finishes are also very good. When we consistently hold close tolerances, we know our surface finishes are going to be fine as well.

He also adds they run anywhere from a single part to as high as 5500-piece runs. "Right now," he says, "we have a 14,000 piece-part run, which is a simple screw, but we run parts that will require three turning operations followed by four milling operations. Some of the jobs are very complicated; some are really very simple.

Sample parts machined on the Feeler FV-760 VMC and the two FTC-20 CNC turning centers at Controlled Turning exhibit diversity in shape, tolerances, and materials while achieving fine finishes."Our business expanded last year by about 40%," Broughman says. "It was one of our biggest years for growth, but the growth was all one customer. We had to decide whether to invest in technology to meet the demand. What if the surge was shortlived, a one-time shot that would ebb away after a few months? In the end, we decided to commit to the customer. We just couldn't turn the work down, even though we were hard-pressed to put in any more hours. When we went to 20 hr a day, we added the one FTC-20 as a replacement and the two other Feelers to address our new capacity needs. These moves enabled us to maintain production—at a higher level than we were accustomed to."

CTI has weathered its share of the automotive-related ups and downs, the downsizing, the outsourcing, the ever-tighter squeeze on industry suppliers for lower costs and quicker deliveries in Jackson, Broughman says. "We rode up and down through those years, but you can't stop working and satisfying your current customer base."

Switch to Oil in Centerless Pays Off   

Mastercut Tool Corp. (Safety Harbor, FL) is a manufacturer of carbide burs and dental burs, end mills, and wood routers. When it was founded in 1985 as a oneman operation, it occupied a 600 ft2 (56 m2) garage. By 1998, five employees were crowded into the garage until an 1100 ft2 (102 m2) rental space was found. Today, the company has 70 employees working in a 37,000 ft2 (3437 m2) facility.

Manufacturing processes include CNC brazing (for attaching bur tips to tool shanks) and centerless grinding. A little more than eight years ago, Michael Shaluly, president of Mastercut Tool, was introduced to the One Micron Filtration (OMF) process of Transor Filter USA (Elk Grove, IL).

A number of Transor Systems were installed to service three of an increasing number of cutter tool grinders. "It wasn't long before we discovered many benefits the Transor's one-micron filtration offered," says Shaluly. "Almost immediately, we noted better surface finishes, closer tolerances being held, and significantly reduced equipment maintenance. A real side benefit was the attitude of the machine operators to their much cleaner working environment."

Grinding has become more sophisticated over the years at Mastercut. This has resulted in selling some of the older machines, which were state of the art at that time, and replacing them with newer grinding technology. "My management team at Mastercut is always looking at ways to use new technology to give us a competitive advantage," Shaluly says. "So it only made sense a couple years ago to look at our equipment and processes to see if there were additional benefits which could result from using Transor."

That thinking led Shaluly to a conversation with Transor president Irv Kaage. One of the areas they discussed at length was Mastercut's tool prep area. Here, several centerless grinders were being utilized to prepare thousands of blanks for the many standards and specials that Mastercut ships each month. "We started looking outside our tool-grinding operations to examine our preparatory cells. We had an idea that this could be a prime area for a technology update," says Shaluly. "It is like the next stage of improvement for us."

The prep center at Mastercut consists primarily of several centerless grinders. Like most centerless operations, the Mastercut production team had utilized water as the coolant. According to Shaluly, "We stayed with water because you have a lot of surface contact area. You've got two grinding wheels and a carbide rod. This is all through-fed so the carbide rod goes right between two wheels, a regulating wheel and a diamond wheel. Depending on the size of that rod, you have a lot of surface contact area hitting the diamond wheel, and, thus, you have a lot of heat buildup."

When first trying oil, Mastercut basically took their entire centerless grinding department and did a total conversion from water to oil coolant. While they did utilize a Transor System, it wasn't outfitted with a chiller to address the heat issues, nor was there a change in wheels. While they were able to run clean oil through the machines, the lack of the chiller produced less than desirable results. In addition, Mastercut didn't start with the synthetic oil. "We thought let's go with the less expensive since it's a test," states Shaluly. "Due to all these factors, immediately we were met with the heating problem and had to go back to the drawing board."

In spite of it all, Shaluly was convinced they could get better results with the oil and focused on combating the heat issue. As they reviewed the entire production area and continued productivity reviews, Shaluly decided they would give oil another try with their centerless grinders.

"What we did differently this time," notes Shaluly, "is we decided to isolate one machine initially. Our team decided to avoid all the pitfalls we had already experienced—we would use synthetic oil, add a chiller, determine the optimum wheel for the application and use a very rigid machine."

They decided to put every resource available into play and look into all factors in the process. After an initial meeting with Transor, Shaluly's team also met with the machine OEMs, the diamond wheel manufacturers, and the oil suppliers and then began serious testing.

Mastercut purchased an additional Transor unit specifically for the one centerless grinder. It was determined that the new Transor would be equipped with a chiller to address the heat issues. "Temperature-controlled oil," says Transor President, Irv Kaage, "along with OMF is absolutely necessary to achieve accuracy and repeatability."

Initial testing was primarily conducted on an 1/8" (3.175-mm) bar because it was easiest to control. With less surface area, there was a greater chance for success in eliminating the heat/expansion issues. After adjusting feed/speed rates and coolant flow, they found the right combination to produce consistent parts.

The addition of the chiller on the Transor System with the temperature- controlled oil enables operators to hold tolerances, which initially gave them some expansion problems due to the heat buildup even with water. They are consistently holding 0.0002" (0.005 mm) on the OD. Also, regarding the chilled oil, Shaluly quickly adds, "the rods come off as cool as they were when being loaded."

Mastercut has been able to expand production from 1/8" (3.175-mm) diam rod up to 1" (25-mm) stock. Additionally, Mastercut is changing over to oil in the preparation of their special tools as well, where necking and step-downs are part of the operation. "We have ordered another machine from Transor just for that," says Shaluly. "We are very confident that it's going to work. We're going to eliminate testing; we've learned enough from the centerless grinding."

"I think just putting all of those aspects—the oil, chiller, proper wheel, and machine rigidity into play—made all the difference," says Shaluly. "Immediately it all just clicked." Mastercut has been running now for a number of months, and it has been a total success with greater heat dissipation than they were experiencing even with the water. In addition, Shaluly pointed to several other benefits that the Transor system has brought to the operation, including extended grinding wheel life, surface finishes virtually free of burn marks, consistent thermal stability resulting in a better end product, and easier reclamation of the carbide.

Shaluly is also committed to eliminating water from the entire Mastercut operation. Plans are in the works for converting the remainder of their centerless grinders and several surface grinders to oil. "It's not just about the production benefits," says Shaluly, "removing water also has its own environmental issues. The nice thing about the oil is it just seems to last a very long time. And you're not having the cost of recycling it. So far we haven't had to replace any oil," Shaluly concludes.

 

This article was first published in the January 2009 edition of Manufacturing Engineering magazine. 


Published Date : 1/1/2009

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