Surface & Profile

MÄGERLE BLOHM JUNG

Cylindrical

STUDER SCHAUDT MIKROSA

Tools

WALTER EWAG
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EWAG LASER LINE PRECISION Machines Diamond Tools in a Single Clamping

EWAG | Laser Line Precision
Cutting materials, such as CBN, PCD and CVD-D

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View the Youtube Video here.

MIAMISBURG, Ohio, Nov. 20, 2015 – Deemed the most compact laser production center in diamond tool manufacturing, the new EWAG LASER LINE PRECISION serves as an alternative to conventional grinding and eroding methods that are unable to handle the level of precision required for processing complex cutting contours and narrow tool tolerances in CBN, PCD and CVD-D materials.

 

With five mechanical axes, two optical axes and short-pulse fiber-laser technology, the LASER LINE PRECISION can handle all aspects of diamond tool production in a single clamping. Automatic calibration of the axes and a 3D measuring probe with soldering error detection ensure the accurate production of rotationally symmetrical tools up to 7.87" in diameter and 9.84" long as well as indexable cutting insert diameters from 0.12" inscribed to 1.97" circumscribed.

 

An industrial 20W short-pulse fiber laser with a 532 nm green-wavelength and 1.5 ns pulse duration make the LASER LINE PRECISION ideal for processing superhard materials. Due to the short application time of the laser pulse, the machine’s laser energy feeds into the tool before plasma effects are produced in the machining area. 

 

When compared to the conventional 1,064 nm wavelength found in other designs, the LASER LINE PRECISION’s halved wavelength doubles the photon energy in the   machining area. As a result, the ablation rate can be increased with the same laser output. The shorter wavelength is also advantageous for machining diamond materials due to the increased absorption properties, especially in semi-transparent CVD-D materials.

 

EWAG ‘s patented tangential laser beam machining, or Laser Touch Machining® technology, enables the LASER LINE PRECISION to process high-quality cutting edges and cutting geometries in an efficient manner. During the process, the outer surface of the laser beams shape the surface of the tool, while the repetitive hatching pattern of the laser scanning unit and simultaneous travel movement of the mechanical axes produce the cutting joint.

 

The LASER LINE PRECISION comes equipped with a FANUC control, an intuitive human machine interface that contains all relevant data views and EWAG’s LaserSoft with plug-in LaserPro 3D. The proprietary software packages handles laser and machine control and enables quick, easy programming of complex applications.in

 

It is also possible to integrate peripheral automation equipment with the machine such as a FANUC six-axis folding arm robot with various gripper systems to achieve increased levels of productivity.

 

With a compact footprint of 53.8 square feet, the robust LASER LINE PRECISION expands EWAG’s laser solutions product line by providing a smaller, more afforable option to shops that seek all-in-one laser processing of diamond cutting tools.

 

EWAG is one of eight brands within the UNITED GRINDING portfolio of high-performance equipment for surface and profile, cylindrical and tool grinding applications. 


GAS TURBINE ENGINE COMPONENTS MACHINED UP TO TWO-THIRDS FASTER ON BLOHM 5-AXIS GRINDER

The new BLOHM PROFIMAT MC
with stainless steel enclosure

 - Click here to download the .pdf

A PROFIMAT MC 607 5-axis CNC grinder manufactured by Blohm Jung GmbH in Germany has contributed to boosting production of nickel alloy turbine components at the Lincoln factory of Siemens. Installation of the machine, a joint collaboration between Siemens Lincoln, Blohm Jung GmbH and BLOHM's UK agent JRA Bennett Ltd, was in response to a significant rise in new industrial gas turbines (IGTs) delivered in the past two years. An increase in engine rebuilds, following the opening of Siemens' new service facility nearby, has also contributed to the higher workload.

To raise grinding efficiency, the PROFIMAT MC is one of the first in the world to be fitted with BLOHM's new RazorTec® wheel cleaning technology, which reduces cutting forces and enables faster feed rates.

Whereas on other creep-feed grinding machines on site, table speed is restricted to between 600 and 800 mm/min to prevent burning of the sensitive nickel alloy compressor parts, the PROFIMAT MC achieves 1,000 mm/min to provide productivity improvements ranging from 25 to 67 per cent. Wheel speed at 21 m/s and 1 μ/rev infeed are the same on all of the machines, as these have been established over many years as optimal for grinding the nickel alloy and minimising wheel consumption.

The Lincoln factory specialises in producing smaller Siemens IGTs for power generation up to 15 MW. The components ground on the new BLOHM machine are for the hot part of the engine, notably low and high pressure nozzle guide vanes for the rotor and vane segments for the stator. Production is around-the-clock during weekdays and extends into the weekend.

Phil Howard, Senior Manufacturing Engineer at Siemens in Lincoln commented, "We needed investment in our blade shop and wanted a new machine that could grind both nozzles and segments. We investigated VIPER grinders on a machining centre platform and looked at other makes of 5-axis creep-feed grinders, but finally selected the BLOHM for a number of reasons. "First was the high productivity and accuracy achieved during trials. Despite the faster cycles, we immediately matched the tolerances that we were getting on other grinders of a different make that we knew well and on which we had been tweaking the process for the past 12 years. We were surprised by that. Vanes are flying through the machine and the tolerances achieved are now superior to those we were achieving before.

"The BLOHM grinder also had the smallest footprint at 3 metres by 5 metres, which was important as space is limited on the shop floor at our Pelham Street works. "Another reason for choosing the BLOHM was our successful use here of two 22-year-old PROFIMAT MTs, which are still holding tolerance grinding the teeth of Hirth couplings."

 The engineer from BLOHM was at Siemens for three weeks to ensure everything went smoothly, from further development of the applications to machine installation, commissioning, acceptance and training. Mr Howard wrote the programs at an offline station running BLOHM software, which provides the user interface to the machine's Siemens 840D control.

The PROFIMAT MC 607 is configured for large production runs of up to 70-off, rather than one-offs and small batches. Between two and five aluminium oxide wheels of 400 mm diameter are exchanged automatically from the tool changer to complete a grinding cycle. To maximise production output, the wheels are continuously dressed during grinding using a rigid, twin-station, overhead dressing unit. It swivels under program control and normally accommodates two diamond dressing rolls.

RazorTec® wheel cleaning technology

To maximise productivity, the PROFIMAT MC 607 has a wheel cleaning system, called RazorTec®, that continuously projects filtered coolant at 40 bar towards the grinding wheel. Consistency is achieved by automatically maintaining the same angle and distance between nozzle and wheel as it wears.

It forces metallic debris out of the porous structure of the aluminium oxide wheel, keeping it sharp and consequently raising stock removal rates while lowering heat transmission to the workpiece. The risk of burning and microcracking of the nickel alloy in a heat-affected zone near the surface of the material is consequently much diminished.

Further advantages are reduced wear on the grinding wheel and dresser and hence better profile integrity, lower grinding forces and a decrease in power consumption.

The wheel cleaning technology was developed in collaboration with IWT Bremen, a research institute located on the University of Bremen campus. The nozzle positioning unit is servomotor driven and programmable so that it maintains the same distance from and orientation to the grinding wheel. The cleaning jets are mounted just above the coolant nozzle, which is angled directly at the point of grinding. The carriage carrying the two nozzles is also adjustable automatically or manually in the Z-axis.

It is this level of precision that allows such efficient wheel cleaning and coolant delivery. The Z-axis movement has helped considerably on vertical and steeply angled faces, as it can be offset to one side if required by the process. This feature also allows clearance when machining some components. 

About the PROFIMAT MC 607 grinder at Siemens

 The 8.5 tons, travelling-column machine is robust and highly capable, with 45 kW of spindle power, a cartridge-type HSK-A 80 grinding spindle, and a magazine for up to 24 tools that can include milling and drilling cutters in addition to grinding wheels. Axis travels are 700, 650, and 520 mm in X, Y and Z respectively. The machine is equipped with linear guideways for high acceleration.

Preloaded, widely-spaced, anti-friction guideways in all axes guarantee rigidity and minimise maintenance. Glass linear scales are provided for high precision feedback of axis positions, commensurate with a machine tool capable of achieving tolerances measured in microns. The machine at Siemens is equipped with an indexing table which provides the two rotary NC axes and a System 3R pallet system to clamp the IGT components for grinding.

Mr Howard concluded, "We are very impressed with the reliability of the latest BLOHM PROFIMAT MC. There were no teething problems in the first 90 days, which is unusual for a new machine, and there have been very few issues since. Our operators really like the grinder and the control system, which they find easy to use. The accuracy and finish of the ground components were exemplary from day one, and the stiffness of the machine means that there is no need to spark out at the end of a cycle, saving further production time." 


Garage Shop Evolves into CNC Tool Grinding Specialist

Making the move to CNC tool grinding with Walter Helitronic technology has enabled AcuTwist to expand its business into specialty cutting tool production.
Much of the shop’s current business is producing special tools from carbide blanks ranging in diameter from 0.157 to 0.875 inch and lengths to 6 inches.
The Helitronic Power tool grinder’s large C axis under the work heads enables complete grinding of complex tool geometries in single setups.
Marcus Young uses Tool Studio programming software to produce unique tool geometries that he couldn’t previously produce.

This tool grinding shop was able to transform itself into a specialty cutting tool producer with the adoption of a few advanced CNC tool grinding machines.

                    Much of the shop’s current business is producing special tools from carbide blanks ranging in diameter from 0.157 to 0.875 inch and lengths to 6 inches.

When the idea came to Marcus Young in 1989 to start his tool grinding company AcuTwist, he was managing an internal machine shop for a specialty subcontractor that did a lot of production drilling in powder metal parts for automotive and outdoor equipment applications. Since then, AcuTwist has blossomed from a garage with a single manual grinder into a thriving shop running three advanced CNC tool grinders to produce rotary tools with complex geometries for powder metal components.

At the shop where Mr. Young previously worked, the holes drilled in the powder metal parts were usually less than 0.438 inch in diameter, with depths ranging from five to 10 times the diameter. Every day, the shop would burn through some 100 carbide and high speed steel drills, mostly due to poor tool performance. According to Mr. Young, finding drills that cut to size and held required tolerances was difficult with the challenging material, so the shop preferred to resharpen its own drills to size. However, the process lacked repeatability, which prompted Mr. Young to propose buying a better resharpening system. The owners of the company were unwilling to make the investment.

So Mr. Young took a leap of faith on his own time. He secured a loan, acquired the equipment, which included one manual tool grinder, and opened AcuTwist for business in his Kersey, Pennsylvania, garage.

The tiny shop was an almost immediate success, quickly picking up several customers when it became apparent that Mr. Young’s regrinding expertise produced drills with much longer life than standard tools. “I realized that, by tweaking the geometry just a bit, we could get longer tool life, cut rounder and straighter holes, and reduce the size of burrs on the exits of through holes,” he explains.

As business increased, AcuTwist hired a couple more employees and purchased another manual grinder. Mr. Young began looking into CNC tool grinding technology and how it could potentially benefit and expand his company’s grinding capabilities. In 1998, he made another significant leap and purchased his first CNC tool grinder through United Grinding North America Inc.: a Walter Helitronic Mini Power. To keep pace with still-rising demand, an additional Walter Helitronic Power grinder was soon followed by another. It was around this time that AcuTwist moved out of Mr. Young’s garage into its current (and larger) location in Ridgway, Pennsylvania.

These Walter tool grinders feature 3D gantries for rigidity and precision. The grinding spindles ride on large cross-slides within enclosed back walls, while large C axes under the work heads enable complete grinding of complex tool geometries in single setups. This C-axis design also eliminates the need for rotary spindle axes.

AcuTwist kept growing as Mr. Young learned how to capitalize on the capabilities of his CNC grinders. The shop expanded its offerings beyond just drill resharpening to include generating a variety of tool geometries such as step drills, drill/reamer combination tools, form tools and other specialty tools.

Because he had never produced a tool on a CNC grinder, Mr. Young relied heavily on Walter’s tool grinding software when it came to generating tool geometries and developing machine programs. He progressed from the standard software to CyberGrind, and most recently, to the more advanced Tool Studio.

This software uses a step-by-step wizard format to guide the operator through the process of programming complex projects like Acu­Twist’s. The wizard function fills in the blanks from its database to speed up programming of drills, cutters, step tools, form tools and other rotary tools.

In an effort to go paperless, the company has started to purchase tablets for operators to use on the shop floor, easing data upload and monitoring with such systems. AcuTwist is making strides in this regard, primarily as a result of a May 2014 flood that left its facility and equipment sitting in three feet of water. Thanks to help from United Grinding and its suppliers and customers, the company was operational just three weeks after the flood.

As he got used to the new software, Mr. Young found he was able to produce unique geometries that he couldn’t make previously with PC-based programs. “With Tool Studio, I can put two drill points together on the same tool and use as many as six wheels to generate it,” he says. “Between our Helitronics, we run programs for more than 80 specialty tools and over 100 standard tool programs.”

That flexibility enables AcuTwist to develop multiple tool geometries tailored for machining of powder metal components—a tough job given the material’s abrasive quality and part tolerances often in the micron range. “In one application, we developed a drill/reamer for a tier-1 automotive supplier that produces powder metal parts,” Mr. Young says. “Now we manufacture that tool in six different sizes for processing timing gears, transmission gears, bearing caps and other powder metal drivetrain components.”

In fact, a significant portion of the shop’s current business is producing special tools, mainly from carbide blanks ranging in diameter from 0.157 to 0.875 inch and lengths to 6 inches. For instance, an order for a tapered end mill with an angular tolerance of ±0.05 degree over a 1.5-inch length is now nothing out of the ordinary for the small shop.

It has come a long way from just resharpening drills.

To increase output and support unattended operations, AcuTwist’s CNC grinders use Walter’s ECO Loader Plus and thermal compensation software that together enable the shop to run overnight in addition to the 10 to 12 hours the machines run during the day. The compensation software measures and adjusts for machine growth to ensure consistent grinding precision, while the ECO Loader Plus supports loading as many as 80 tools on the work heads.

According to Mr. Young, the company’s business model is a bit different from many larger tool grinding companies, and he aims to keep it that way. “Our niche is rapid turnarounds on relatively small quantities of special tools: anywhere from one to 200 pieces,” he says, adding that some projects require turnaround times as fast as a couple of hours. “Our Helitronics enable us to keep pace and continue to meet and exceed those customer needs.”

Credits: Jim Anderton, Editor

Canadian Metalworking

Pages 10-13 of the Grind Magazine


ID Grinding Machine | CT750
Adam Thomas | Vice President at Thomas Wire Die

A shop can grow its business in many ways. One proven path involves steady expansion based on a foundation of expertise. The consistent growth of Thomas Wire Die Ltd., Burlington, Ontario, is a good example. Founded in 1966 to produce and service small tungsten carbide wire dies, the company built on its experience in making precision parts from hard materials and used it to expand its range of products and customers. And through its nearly 50 years in operation, the shop has continually updated its manufacturing technology to enable it to take full advantage of its special skills.
Wire drawing dies are the shop's original product and continue to be an important part of the business. A typical die is composed of a steel casing that holds a carbide component with a hole through which wire material is drawn. "We buy carbide and steel as raw materials and we machine the steel casing, grind or EDM the carbide, then assemble them into a tool and finish it," said Adam Thomas, vice president of Thomas Wire Die as well as grandson of the company's founder.
If the die aperture is round the shop grinds it; if it is square or another shape it is machined via EDM. Part sizes include casings as large as 16" OD that hold a carbide insert with a 12" diameter; among the smallest part features produced are 0.005"-diameter holes in natural diamond wire drawing dies.
As time passed, Thomas Wire Die began to produce larger carbide wire and cable dies, then added dies used to cold finish round bar and to draw square, hex and other shapes of bar and tube. Expansion continued with the manufacture of carbide punches and shape dies for forming, stamping and deep drawing, as well as tube drawing plugs and mandrels.
Taking further advantage of its longtime familiarity with the challenges of processing hard carbide parts, Thomas Wire Die moved into engineering and producing carbide wear components. The custom parts combat corrosive and abrasive wear in industrial applications ranging from agriculture to aerospace. "In wear components, we look for opportunities where we can get people to switch from using tool steel to carbide," Thomas said. "Carbide can provide five times the life of the tool steel. Our customers used to replace a tool steel part every month, now they replace it every six months."
As the shop expanded its offering of services, it continually augmented its skills with the addition of new manufacturing technology including EDM, turning and milling machines, and advanced CNC grinders that enabled it to serve its traditional markets better and move into new ones.
A notable addition was the company's 2006 acquisition of Stoney Creek Precision Parts, a machine shop and manufacturer of cold-heading dies used to form bolts and similar products. Thomas Wire Die made the acquisition to help it grow its business in the cold-heading die market and strengthen its machining capabilities.
About three years ago, Thomas Wire Die looked for ways to reinforce its capabilities in the ID grinding that is still the basis of the company's business. "We grind ID every day, all day, and we asked ourselves what piece of equipment would help us be better in that product," Thomas said. "We weren't trying to get into a totally new area; it was work that we already had and we wanted to move it on to a machine that was more efficient and produced higher quality, higher precision and better parts."
Subsequently, the company acquired a STUDER CT750 radius ID grinding machine for hard materials in 2011. The machine has a CNC-controlled B-axis with an automatic swiveling range from +60 degrees to -91degrees. An oscillating grinding wheel enables it to produce an unlimited number of different radii up to 90 degrees. A modular turret with two grinding spindles provides great flexibility in the machining of individual parts as well as large-scale production. The machine handles small- to medium-size workpieces, with X- and Z-axis travels of 14" and 10" respectively, a grinding length of 4", and a maximum ID grinding diameter of 3".
"Part of what prompted us to look at the STUDER machine was to reduce cycle times and be more competitive on the pricing side," Thomas said.
The machine's CNC technology and structural rigidity ensure the production of a good grinding surface finish. Surface finish is critical in diemaking because it is the basis for final polishing. "The STUDER machine allows us to get a better surface finish faster than we could before, and reduces polishing by hand," Thomas said, noting that excessive polishing can distort a part's geometry.
The STUDER grinder also has in-process gaging capability that helps reduce cycle times. The probe measures the part during the rough grinding process and adjusts the operation to leave a minimum amount of material for finish grinding. Because finish grinding is slower than rough grinding, minimizing finishing passes reduces cycle times overall.
The machine's CNC capabilities also boost part consistency. Previously, for example, reworking a wire die involved changing its contours via manual grinding. Now the shop can program an exact radius. "The STUDER machine allows us to produce a more consistent, uniform product,"
Thomas said. "In the past when we ground the parts by hand, we might get a few tenths difference on the size. Now, we can sell a die today, and sell that same die a month from now, and it is exactly the same geometry. The customer knows the dies are identical." Thomas said the programming software has proven easy to use, both for employees who are familiar with computers and those who are not. However, he pointed out that the best results require a combination of computer savvy meshed with familiarity with the grinding process.
Thomas Wire Die soon found that the shop had enough work to keep the STUDER grinder going nonstop. As a result, the company recently added a second CT750 machine. "The machine's increased efficiency has freed personnel to move to other areas," Thomas said. "Where we might have had three people doing work, now we have one and a half. The other one and a half are working in other areas because of growth we are seeing in other products."
In addition to increasing revenue, expanding and diversifying a company's customer base can help moderate the effect of economic slowdowns. "Part of our thought process in how we grew our business was to try to expand into different markets," Thomas said. "Working with customers in wire and cable, oil and gas, metal forming, metal stamping and wear parts helped us historically in that when there was a downturn in one area it didn't affect everything."
The depth of the most recent "Great Recession," however, certainly had more impact than past slowdowns. Thomas Wire Die reluctantly performed the first layoffs in the company's history. "That was a culture change," Thomas said. "We realized we had to look more closely at cost control. New CNC grinders and wire EDM equipment have allowed us to increase our output. We are also looking at ways to increase the utilization of the equipment we have. We run a single shift now and we have a lot of capital equipment that sits idle two out of three shifts every day. We are looking at changing that, which will mean adding additional people."
Today, Thomas Wire Die has 20 employees at its 17,000 sq ft. facility and handles between 150 and 200 accounts a year. The shop's diverse skills enable it to participate in a variety of industry segments. For example, its cold-heading dies are used by suppliers to make fasteners for the aerospace industry. Similarly, the shop makes tooling that tier 1 and 2 suppliers use to deep draw and stamp automotive components.
The fastest growing market for wear resistant parts is the oil and gas industry. "There is more and more fracking activity in North America and worldwide, and it is driving a lot of that growth," Thomas said. The shop makes carbide valve components up to 4" and 5" in diameter and 10" long as well as other parts such as nozzles and small wear rings. Some of the customers for the parts are international OEMs that use the components in assemblies that are shipped worldwide.
In the present era of struggling digital startups with alleged vast potential but questionable experience, Thomas Wire Die bases its growth on its prior successes and strengths, and applies that expertise to realize the potential of new and growing markets for its singular products and services.  


Credits: Jim Anderton, Editor

Canadian Metalworking

Pages 10-13 of the Grind Magazine


Cylindrical Grinding Technology in Motion

“The Cylindrical Grinding Universe” was the theme for United Grinding’s 2015 Motion Meeting in Switzerland. This theme was particularly appropriate because a key point was the expansion of ID grinding capability to provide universal coverage of the full range of workpiece sizes.
 

Every year, United Grinding hosts a gathering of its sales partners and trade press editors from around the world. The purpose of this annual ‘Motion Meeting” in Thun, Switzerland earlier this month, was to highlight the group's latest developments in grinding technology, especially in the area of cylindrical grinding, which includes the Studer, Schaudt and Mikrosa brands. United Grinding also used this occasion to deliver its prestigious Fritz Studer Award for innovative research in machine tool or grinding technology.

Topping the list of new products introduced at the event are the Studer S131 and S151 cylindrical grinding machines, which are built on the innovative S141 cylindrical grinding platform. The S141 platform is distinguished by ID and OD grinding capability enabled by a grinding spindle turret that accommodates as many as four grinding spindles. Both internal and external grinding operations can be completed in one setup to enhance accuracy and reduce non-cut times.

The S131 is smaller than the S141. It has a swing diameter over the table of 250 mm (9.8 inches) and a maximum grinding length of 175 mm (6.9 inches) for ID grinding and 125 mm (4.9 inches) for OD grinding. It accommodates workpieces as long as 300 mm (11.8 inches).

For reference, the S141 is available in models for machining workpieces with maximum lengths of 300, 700 or 1,300 mm (11.81, 27.56 or 51.18 inches) and IDs ranging to 250 mm (9.84 inches).

To complete the series, the S151 is larger than the S141. The new S151 features a swing diameter over the table of 550 mm (21.6 inches) and a maximum grinding of length of 400 mm (15.7 inches) for ID work and 150 mm (5.9 inches) for OD work. It accommodates workpieces with a maximum length of 700 mm (27.5 inches).

Studer’s line of ID/OD grinders now covers the range of shaft diameters and lengths with no gaps for both ID and OD capability for complete grinding in one clamping. In addition, all of the machines share the same ergonomics and clean, streamlined styling of the enclosure and pendant-mounted control unit.

Another recent product worthy of mention is the CrankGrind, a crankshaft grinding machine from Schaudt. Cosmetically, this grinder sports that “new look” that represents the unified corporate identity within the Cylindrical Grinding Group as well as the company-wide emphasis on functionality and ergonomics. More important is its capability. The CrankGrind is designed to do rough- and finish-grinding of both main and pin bearings on automotive crankshafts, all in one setup on one machine.

The Motion Meeting also affirmed Studer’s leadership in energy efficiency, which is a concern among all machine tool builders and end users. Studer’s multi-prong approach may be a model for comprehensive energy management in industrial equipment. For detailed commentary, click here.

A further highlight of the meeting was the presentation of the 2014 Fritz Studer Award to Dr. Eduardo Weingärtner from the Swiss Federal Institute of Technology Zürich. Dr. Weingärtner’s work pioneered the application of the wire EDM process for on-machine dressing of metal bonded grinding wheels. This research was instrumental in the introduction of the Studer WireDress system detailed here.

Finally, as a bonus for visiting trade press editors, a tour of United Grinding's Mägerle brand was arranged in Fehraltdorf prior to the conclave in Thun. Mägerle, part of the company’s surface and profile grinding group, specializes in large, multi-axis grinding machines. These highly engineered systems are custom-built from flexible modules to combine unique applications with proven design concepts. Although Mägerle grinders represent some of the most demanding and advanced applications in grinding, the company continues to rely on a solid foundation of traditional skills such as hand scraping of ways for mechanical accuracy. In fact, the company's apprenticeship program aggressively courts young talent to replenish its highly skilled workforce, and is a model for sustaining the thoroughly Swiss tradition of precision and meticulous craftsmanship.

Although Magerle does not produce “standard” models of grinders, it does offer distinct product ranges, including the MFP line of multi-axis surface and profile grinders. The MFP 50 shown here is part of a grinding cell for a jet engine manufacturer. The new styling of the MFP grinders reflects the corporate redesign.



Tough Materials Continue to Drive Creep-Feed Grinding

Creep Feed Grinder
Creep Feed Grinder
Overhead Dresser for Creep Feed Grinder
Overhead Dresser for Creep Feed Grinder

Today's difficult-to-process workpiece materials and complex, high-value parts have sparked resurgence in the use of continuous-dress creep-feed grinding. At the same time, the capabilities of advanced grinding machines, CNC technology, and grinding wheel materials have boosted the cost-effectiveness of the process. As compared with traditional reciprocating grinding, creep-feed grinding provides the means to remove significant volumes of metal in a short time and still generate top accuracy and finish. While reciprocating grinding removes smaller amounts of material in multiple faster lighter passes, creep-feed grinding applies the wheel in single passes that are 0.300" or more deep and at slower feedrates. When first put to use in the 1950s, creep-feed grinding utilized relatively soft, porous grinding wheels and flood coolant to minimize generation of heat. Although creep-feed grinding could cut cycle time by half in some cases, the process was limited in application because wheels wore quickly, restricting the length of cut possible before wheels required dressing. The advent of continuous-dress creep-feed grinding in the 1970s addressed the issue of rapid wheel wear. As the name indicates, in continuous-dress creep-feed grinding machines dress wheels without interruption throughout the grinding process. A diamond dressing roll with a mirror-image form of the desired part profile maintains constant contact with the grinding wheel to keep it sharp. Because the wheel is always sharp, long lengths of cut are possible. Plus, this consistent wheel performance results in lower average grinding forces and leads to more efficient abrasive use, shorter cycle times and increased production rates. Creep-feed grinding can be considered abrasive or small-chip machining, capable of replacing milling or broaching in the machining of slots and complex forms in difficult-to-grind materials including prehardened tool steels and advanced alloys. Because the process completes a part in a single fixturing and in one pass, it reduces overall cycle time. The process's single pass generates much lower levels of heat, so thermal affects on the workpieces are minimized. The full wheel contact and slower feedrates of creep-feed grinding also dampen vibration, and surface finishes of 16 rms and better are possible. As manufacturers seek ever-higher levels of performance, durability, and quality, they employ new manufacturing materials such as nickel-base alloys and tough cermet materials like titanium aluminide for parts such as automotive valves and turbocharger wheels. These parts are often complex in shape with thin walls, deep contours and other features that will easily distort or work harden under heat generated by traditional grinding or machining processes Additionally, some whisker-reinforced materials contain fibers, and the large cutting edges of milling cutters can pull them out, but the thousands of tiny cutting teeth of a grinding wheel cut them cleanly. Creep-feed grinding fills a need for an unwaveringly sharp, cool and free-cutting material-removal process. According to grinding machine builders, gaining the maximum benefits of creep-feed grinding requires the use of machines and grinding wheels engineered specifically for the process. Admittedly, some shops perform a variant of creep-feed grinding involving deep passes on workpieces with narrow cross sections. Such operations are possible on standard grinding machines at somewhat reduced table speeds using conventional grinding wheels. But doing so depends on factors that include workpiece material, depth and width of the grinding pass, rigidity of the machine and nature of the grinding wheel. True creep-feed grinding, on the other hand, maximizes the arc of contact between the wheel and part and requires use of a rigid, high-horsepower multi-axis CNC machine designed to handle the high stresses and kinetic complication of the creep-feed process. A major source of complication is the continuous-dress process. For continuous-dress applications, a grinding machine's basic three CNC axes are supplemented by a fourth axis controlling the infeed of the diamond dressing roll. The roll turns in the same direction of the grinding wheel and feeds into the wheel in increments of millionths of an inch per revolution, ranging from typical rates of 0.00001" to 0.00002" per revolution to steps as large as 0.00005" or 0.00006". As the grinding wheel's diameter shrinks during continuous dressing, the grinding machine's programmed wheel spindle increases rpm to maintain the surface speed required to grind the part. Likewise, a variable-speed servomotor constantly changes the dresser roll's rpm to maintain the correct pace of dressing. Depending on the specific application, the contact pressure on a creep-feed grinding wheel may exceed 2,000 lbs total force. The structure of a machine engineered for creep-feed operations must handle such forces and stresses, and part fixturing as well must be designed to resist these high forces too. Horsepower well beyond that of a standard grinding machine is required for creep-feed grinding to generate and maintain the high-productivity forces needed to remove large amounts of material quickly. While a typical reciprocating grinder generates 20 hp to 50 hp, a common creep-feed grinding machine ranges from 60 hp to 150 hp and more. One benchmark dictates 20 hp for every cubic inch of material removed per minute, per inch of wheel width. Ideal creep-feed grinding machines also sport direct drive spindles that eliminate variables such as slipping belts. The drive system for their diamond roll dressers must also possess the capability to generate and withstand high levels of torque. A servomotor drives the dressing roll into the grinding wheel to reform it, but the dressing wheel needs to hold its speed and not impart accelerative forces to the grinding wheel itself. Creep-feed grinding requires that the workpiece be fed slowly and precisely under the wheel - in general, the greater the depth of cut, the slower the table speed. Feed control is crucial to maintain part precision and also because any sudden change in table feed can break a grinding wheel that is under heavy grinding forces, which is often the case in the creep-feed process. Variable-speed ballscrews, racks and pinions or electromechanical table drives will maintain tight control over table speed and position. They provide this control minus any surging that might occur with table speeds as slow as 0.5 ipm, although more common speeds are in the range of 8 ipm - 30 ipm. Hydrostatic or linear-bearing ways then provide preload to eliminate slack and absorb vibration for maximized grinding precision. A variation on the continuous-dress creep-feed process, called in-process continuous-dress, can help control manufacturing costs where possible. With the in-process strategy, the continuous-dressing operation is, in fact, not continuous, but switched on and off according to need. Based on the workpiece material, amount of stock being removed, wheel configuration, and other factors, continuous-dressing on a long cut may result in grinding wheel overdressing. And while part dimensions remain unaffected, valuable wheel material is wasted. During the in-process dressing mode, the machine monitors its power consumption and detects any increases or surges, which would indicate a dull grinding wheel. When a rise in power usage occurs with in-process continuous-dressing, the machine initiates wheel dressing, and when consumption returns to normal, the dressing cycle stops. In the long run, such a strategy can optimize use of abrasives and save time by reducing the frequency of shutdowns for wheel changes. In light of renewed interest in creep-feed grinding, wheel vendors have developed wheels that minimize wheel consumption in the continuous-dress creep-feed process. Grinding wheels engineered for creep-feed grinding applications feature open bond, "induced pore" structures. When the wheel is buried deep in the cut, the pores provide a path for coolant, swarf and excess wheel material to escape the grinding zone. Aluminum oxide, for instance, is the most common abrasive material used in grinding wheels. New wheels designated as ceramics (actually premium-level aluminum oxide) can grind up to three times faster than conventional abrasives, according to wheel makers, while the ceramic wheels' durability enables them to process as many as three times as many parts per wheel. The new wheels' durability and productivity offset their required higher initial investment, wheelmakers say. Wheel durability as well as grinding results themselves are dependent on the proper application of coolant in creep-feed grinding. Coolant prevents buildup of heat in the part and grinding wheel, and also removes swarf from the wheel contact zone to prevent marring of the workpiece. Sufficient coolant flow also prevents the pores of the grinding wheel from becoming filled with swarf, a condition that reduces the wheel's cutting effectiveness and further reduces the coolant's temperature-control benefit. When temperatures rise too high, the wheel may burn the workpiece and swarf may weld to the wheel, negatively affecting workpiece dimensions and finishes. Creep-feed grinding, and in many cases its continuous-dress version, provide a variety of benefits when processing the growing selection of high-performance workpiece materials. Accuracy and repeatability are a given. The speed of creep-feed grinding boosts productivity, and the elimination of many pre-grinding and post-process operations as well as part handling can significantly reduce overall part production times. Successful application of creep-feed grinding requires investment in appropriate equipment including specialized grinding machines and grinding wheels, but for the right situations and materials, return on the investment will far exceed a creeping pace.



Increased speeds have allowed grinding to move beyond its status as a finishing operation to become a primary metal-removal method in some applications. High-speed grinding (HSG) combines high metal-removal rates with minimal wheel wear. But are those higher removal rates and faster production speeds worth the higher grinding machine costs and pricier CBN wheels needed for HSG compared to the ma-chines and aluminum-oxide and silicon-carbide wheels used for conventional grinding? In most cases, the answer appears to be "yes."HSG is commonly used to grind ODs. It is a well-established method for making camshafts and crankshafts, as well as transmission shafts, drive shafts, power steering components, turbine components, gears and aerospace fasteners. Workpiece materials ground with CBN wheels for HSG include nodular iron, hardened carbon and alloy steels, soft steels and nickel-base superalloys.How Fast is Fast?The main benefit of HSG is its higher mrr compared to conventional OD grinding while imparting the same surface finish. This is accomplished by maintaining comparable chip thickness and reduced grinding forces at a comparable power (spindle power = tangential force × wheel velocity) when performing HSG."When you get into high speeds, you can definitely achieve some very high removal rates in certain materials and applications," said Mike Hitchiner, OEM technology manager, Norton/Saint-Gobain Abrasives, Worchester, Mass. "I have applications pushing Q prime values, or mrr [mm3 per mm per second], as high as 600, although numbers around 100 to 300 are more typical. These are typically achieved by grinding burn-insensitive parts made from gray or nodular iron or soft steel, such as crankshafts or balance shafts. I'm also achieving comparable numbers on more burn-sensitive parts, even Inconel, but under specific grind conditions such as peel grinding, which is conducive to low heat generation."Hitchiner noted HSG does not have to generate a massive mrr to be successful. In many cases, the gains are modest improvements in Q prime values, but also enhanced surface finish and consistency, as well as long wheel life.Most agree that the borderline be-tween conventional grinding and HSG of precision parts are wheel speeds of 80 to 120 m/sec. Conventional OD grinding starts at about 30 m/sec., with 60 m/sec. being the usual limit in terms of the need for special guarding and additional safety factors. OD camshaft and crankshaft grinding typically runs be-tween 60 and 120 m/sec., while trans-mission parts tend to be ground at 80 to 120 m/sec. Machine Needs An HSG machine needs to be stable, with high dynamic stiffness and a higher-power spindle than one used for conventional grinding."Also, the headstock on the machine, whether a chuck or some other kind of workholding, has to be able to go faster as well to be able to get the correct ratio between wheel speed and part speed," said Rob Titus, senior applications engineer for machine tool builder Okuma America Corp., Charlotte, N.C.He added that a chiller unit is added to the spindles because of the increased heat. "On the grinders we build, we try to control that high-speed spindle's oil. We keep the temperature constant so there are no tolerance control issues." HSG also requires a specialized cool-ant system, adding to machine cost. A rule of thumb in any grinding operation is the coolant velocity or pressure must match the wheel speed. Therefore, with a higher speed wheel, coolant pressure has to be higher as well. "For example, 60 m/sec. would need about 250 psi, 80 m/sec. around 400 psi and 120 m/sec.would be upwards of 900 to 1,000 psi," Titus said. A coolant system with a high-pres-sure and -volume capability is required to produce the required coolant velocity, according to Tom Namola, product development and application engineer for Abrasive Technology Inc., Lewis Center, Ohio. "There is a relationship between the coolant velocity and the peripheral wheel speed," he said. "When you fall below a certain number, you start to starve the cut. If it is an oil run with plated CBN wheels, the coolant velocity really needs to be, at minimum, 60 per-cent of the wheel speed."And typically with CBN wheels run at high speeds, oil needs to be applied. "Be-cause water-based coolant doesn't have the lubricity and clinginess of oil, it has to match the wheel speed closer or it re-ally won't get carried through the cut," Namola said. "Oil is more forgiving and easier to apply. With water-based cool-ant, that 60 percent number goes up to 85 or 90 percent."Namola also emphasized carefully checking grinding calculations. With the higher coolant pressure and volume needed for HSG, it is a challenge to keep the coolant stream from spreading and slowing down."What matters is the coolant speed at the workpiece/wheel intersection," he said. "If you calculate coolant speed based on nozzle opening area, then you must factor this back by the increase in coolant stream area at the workpiece/wheel intersection."An additional machine need in the U.S. is special guarding when grinding above 60 m/sec., per ANSI standards.Wheel Needs Most HSG of metal is done with vitrified-bond or plated CBN wheels.High speeds place special challenges on wheel design with regard to preventing bursting or distorting under higher centrifugal loads. Wheel mounting methods must be able to hold the wheels without slippage or imbalance. Vitrified CBN wheels for 80 m/sec. and above are segmented, with segments cemented to a steel or carbon fiber core (to reduce weight). Vitrified CBN wheels are dressable, but it is required much less often than with conventional wheels.Single-layer plated CBN wheels, how-ever, are not dressed. With plated wheels, a single layer of CBN grain is bonded with nickel plating to a steel wheel core.When the wheel wears out, the coating is stripped and the wheel is replated. Replating, in general, costs about 40 percent less than a new wheel, according to Namola. Plated CBN wheels are typically replated up to 5 times.The main advantage of using plated CBN wheels when form grinding is that the form can be complicated because the wheel is not dressed, he added. When grinding with bonded wheels, complex forms are challenging because the wheels must be dressed.The grinding wheel itself is challenging to rotate at high speeds, requiring a machine with substantial spindle power to run wide wheels at high speeds. "For example, let's say a shop has been grinding bearing journals instead of turn broaching them using a plated CBN form wheel at 160 m/sec. using a 20mm-wide (0.787") wheel," Hitchiner said. "The wheel is only 20mm wide yet consumes 80kW motor power. Of that 80kW, 40 of it is used just to spin the wheel and overcome the resistance of the coolant. When running at 160 m/sec., a lot of what you gain in the grind energy, making it more efficient to the grind, can be lost in the wheel energy and the drag of the coolant."Therefore, he continued, applications for HSG frequently use narrow wheels, such as for circlip groove grinding, rotor slots and peel grinding. "You don't have to worry about the wheel mass and the coolant drag is a lot less. Having 3kW to 4kW per mm of wheel width is good rule of thumb."Peel Grinding Peel grinding, performed with vitrified CBN wheels, is an alternative to formed-wheel plunge grinding. CBN wheels are well-suited for peel grinding because they offer extra strength at the edge of the wheel With peel grinding, a narrow wheel-6.4mm (0.25") or less in width-is moved along the contour, completing the full grind in a single pass.The last 2mm to 3mm of the wheel face generates the required surface finish.Peel grinding concentrates all the grinding force in one small area, grinding relatively small-diameter parts at high work speeds to minimize heat generation; the wheel is similar to a single-point tool on a lathe. "Peel grinding works by having a very small contact area and very high wheel and work speeds, taking typical DOCs of 0.005" to 0.015"," Hitchiner said.This small contact area between the workpiece and the grinding wheel reduces the cutting forces. Reduced cutting forces generate less heat, which means peel grinding can be performed at higher speeds. "The impact of the grain on the workpiece is not as much as with slower speeds, so it doesn't induce heat into the part," said Hans Ueltschi, vice president of sales, cylindrical division, for United Grinding North America Inc., Miamisburg, Ohio. "The part stays cool, there is less pressure, and the part doesn't bend as much."One of the biggest advantages of peel grinding is flexibility. "The process is really flexible, so it is good for parts that require quick changeover," Ueltschi said. "To go from one part to an-other, all you have to change is the program on the machine. You don't have to tear down the grinding wheel and dressing system and put in new ones. You just put in the dimensions and you are good to go." This allows for low-volume runs.For high-volume jobs where no flexibility is required, such as when making crankshafts, the plunge method is used be-cause it reduces cycle times.In addition to replacing conventional grinding, HSG can match or exceed many conventional machining processes, ac-cording to Hitchiner. One example is gear hobbing. "Right now, customers buy a grinding machine to get final gear shape after heat treatment, but they still broach the rough form be-forehand," he said. "If you are repairing big gears for the oil or mining industry, you could wait 10 weeks for a hob. If you have a grinder already available that can generate the form, and a grinding process that can cut as fast as a broach in the soft state, you can turn around a part in a fraction of the time. There are huge savings for just-in-time work instead of waiting around for expensive cutters."

Susan Woods is a

contributing editor for CTE. Contact her at (224)

225-6120 or susanw@jwr.com



UNITED GRINDING Schedules North American Tour for STUDER S11
February 1, 2014

Beginning February, UNITED GRINDING will make it possible for manufacturers to get in front of the latest precision cylindrical grinding technology without having to travel far. The company has plans to take its new compact, highly productive STUDER S11 for small workpiece production on a six-city tour across the United States.

"By showcasing the S11 at key channel partner locations across North America, we can effectively demonstrate and/or discuss the machine in close proximity to our customers," said Ted Neckel, Director of Corporate Marketing for UNITED GRINDING North America, Inc. "In today's competitive marketplace, manufacturers do not want to spend a lot of time away from their operations, and product showcase initiatives such as this quickly and easily get them in front of new technology and then back to work."

UNITED GRINDING will conduct live grinding demonstrations on the S11 at the following STUDER distributor locations:

  • February 19-20: Greer, SC
  • February 26-27: Rochester, NY
  • March 5-6: Brecksville, OH
  • March 12-13: Livonia, MI
  • March 26-27: Itasca, IL
  • April 22-23: Los Alamitos, CA.

First introduced at EMO 2013, the S11 is the smallest machine in the STUDER portfolio and tailor-made for small workpieces up to 7.9" (200 mm) in length and 2" (50 mm) in diameter. According to Neckel, the extremely compact cylindrical grinding machine delivers a level of productivity and Swiss precision that will amaze even the most experienced grinding specialists. Furthermore, the company reported that the S11 is one of the first machines to feature the new UNITED GRINDING Group design protocol that brings added value to customers in terms of ergonomics and operability.

STUDER is one of eight brands in the UNITED GRINDING portfolio of grinding and ultra-precision finishing solutions for the manufacturing industry.

Additional S11 North American Tour details as well as registration information is available at S11tour.com.