TECHVIEW ADVANCED PLATED CBN GRINDING TECHNOLOGY. abrasive technology

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1 abrasive technology TECHVIEW ADVANCED PLATED CBN GRINDING TECHNOLOGY The Industrial Diamond Association of America, Inc. Diamond & CBN Ultrahard Materials Conference Windsor, Ontario, Canada September 29-30, 1993

2 Advanced Plated CBN Grinding Technology Abstract The U. S. Air Force funds a number of programs for the advancement of technology each year. A three-year program was funded to develop and document machine and CBN electroplated wheel parameters that improve CBN wheel performance in the creep-feed form grinding of aerospace alloys in water-based coolants. The end user of CBN plated grinding wheels is being challenged to change coolant type due to (1) Safety & Hygiene, (2) Compliance with expanding state and federal regulations, and (3) Reduction of disposal expense while trying to reduce overall production costs. This paper focuses on the development of an electroplated CBN grinding wheel specification for creep feed grinding of aerospace alloys in water soluble coolants. This optimization study details the important CBN wheel specifications, machine conditions, coolant effects on wheel performance, and operating parameters for grinding in water-based coolants. Key Points CBN plated form wheels are a growing tooling technology and have been the topic of several published reports delineating the advantages and operating characteristics. There are many factors which can effect the performance of electroplated CBN form wheels. These factors are interdependent with other elements of the grinding process. Poor performance from any of these elements will result in poor performance from an optimally specified and manufactured grinding wheel. Five major areas that impact CBN wheel performance are: 1. Machine Tool Quality Rigidity Accuracy of Feed Systems Adequate Power Fluid Delivery / Containment 2. Initial Conditioning of the Grinding Wheel 3. Machine Feed Parameters 4. Grinding Wheel Speed (SFPM) 5. Grinding Fluids (Types) Synthetic (Chemical) Semi-Synthetic Soluble Oil (Emulsion) Straight Oil; Petroleum and Synthetic Of these five areas, the grinding fluid is probably the most misunderstood, most overlooked factor in optimizing a grinding wheel s performance. Abrasive Technology was contracted by Pratt & Whitney to perform development work on CBN plated form wheels. The program objective was to characterize the existence of any debit in wheel life associated converting from a straight oil coolant to a water soluble coolant, and to develop, through statistical experimentation, techniques to restore the lost productivity. This has been accomplished. Manufacturers currently using plated CBN grinding wheels in a straight oil coolant should not expect to be able to simply change coolants and retain performance. There is a debit. Through attention to a variety of factors, including specification of the grinding wheel, the lost productivity can be restored. Through the use of statistical methods, engineering disciplines and progressive improvement, we have learned: The developed bonding system provides a 77% increased life (Statistical Significance at 95% Confidence) in water based coolants from previous standard construction. Using 1A1 type wheels, initial water baseline testing showed a 41% reduction in life of AT s standard construction compared to the oil baseline results. Base line productivity, established with a straight oil coolant, can be restored (and exceeded) through combination of the developed bond and implementation of associated grinding process parameters. CBN plated form wheels for high speed creep feed grinding (<10,000 SFPM), using water based coolant, critically requires use of high pressure cleaning jets. Coolant concentration between 10% and 30% had no significant effect on wheel life. Titanium Nitride (TiN) coating was ineffective, statistically, for extending life of plated CBN wheel under high speed creep feed grinding conditions. Infeed rate is a very strong driver for wheel life. CBN 500 was statistically superior to CBN 570 and ABN 600. There is a set of conditions under which a CBN plated wheel can grind a deep form in cobalt with considerable wheel life and part quality. 3

3 Introduction The United States Air Force (USAF) has a long established record of sponsoring manufacturing technology research and development. Frequently these programs were conducted by national laboratories, universities, or aerospace prime contractors and the results could not easily be transferred to industry. This paper discusses preliminary results of a technology development program led by Abrasive Technology (AT); a leading United States manufacturer of cubic boron nitride (CBN) and diamond grinding wheels. Abrasive Technology was selected by Pratt & Whitney (P&W) to lead two Advanced Grinding Technology programs, funded by the United States Air Force Industrial Modernization Incentive Program (IMIP), related to CBN plated grinding wheels. Under these programs, AT is developing and validating improvements to the creep feed grinding process associated with the use of electroplated CBN form wheels and with water based coolants. The principal AT team members are Pratt & Whitney, GE Superabrasives, Master Chemical, and Maegerle, Inc. Pratt & Whitney is an industry leader in the application and use of creep feed grinding and is a national leader for promoting this manufacturing technology through such organizations as (1) The University of Connecticut Center For Grinding Research and Development, (2) University of Massachusetts Research Program on Grinding Fundamentals and Applications, and (3) National Center for Manufacturing Sciences. Selected portions of the work discussed in this paper, are part of a larger United States Air Force (USAF) sponsored Advanced Grinding Technology contract competitively won by P&W in December, Dissemination of the detail information developed under the USAF contract is restricted. The final report can be obtained by all qualified U.S. based manufacturers. Early dissemination of the results generated from these U.S. Government funded programs can occur when qualifying conditions are met. For example, American firms with current manufacturing contracts with the defense industry and an interest in utilizing plated CBN grinding wheels would qualify. Background CBN plated form wheels is a growing tooling technology and has been the topic of several published reports (1, 2, 3) delineating the advantages and operating characteristics. Typical benefits of electroplated CBN form wheels are: 1. Free cutting resulting in: (a) Higher materials removal rates, (b) Grinding with less power, and (c) Reduced thermal damage to workpiece. 2. Manufacture and plate complex and intricate forms. 3. Ability to hold form or profile from the first to last cut. 4. Lower cost, when compared to vitrified, resin, and metal bond CBN wheels. 5. Safe, high speed operation through the use of steel cones. 6. Ability to strip and replate core. 7. Reduction or eliminating of time associated with dressing, set-ups, and wheel changes. There are many factors which can effect the performance of electroplated CBN form wheels. These factors are interdependent with other "elements" of the grinding process. Poor performance from any of these elements will result in poor performance from an "optimally specified" and manufactured grinding wheel. An excellent overview on the factors influencing CBN wheel performance was published by GE Superabrasive (1). This paper identified five major areas that impact CBN wheel performance: 1. Machine Tool Quality Rigidity Adequate Power Accuracy of Feed Systems Fluid Delivery/Containment 2. Initial Conditioning of the Grinding Wheel 3. Machine Feed Parameters 4. Grinding Wheel Speed (SFPM) 5. Grinding Fluids (Types) Synthetic (Chemical) Semi-Synthetic Soluble Oil (Emulsion) Straight Oil; Petroleum and Synthetic The GE Superabrasives paper further observes that The grinding fluid is probably the most misunderstood, most overlooked factor in optimizing a grinding wheel s performance. In 1993, manufacturers are being pressured to reduce their dependence on straight oil coolant due to (1) Safety & Hygiene, (2) Compliance with expanding state and federal regulations, and (3) Waste disposal costs. Specific shortfalls of straight oil grinding include: (1) Oil misting in the manufacturing area, (2) Fires (occasionally explosive in nature), and (3) Constantly changing regulations and cost associated with treatment and final disposal of the oil. Manufacturers are also being pressured to be more productive; lower costs. Straight oil coolant currently provides the best overall wheel life, as illustrated in Table 1, taken from the GE Superabrasives report. This table illustrates the dichotomy of contrasting properties provided through use of straight oil coolants. 4

4 Contracted Work Scope: Eliminate Basis For Straight Oil Coolant The Statement of Work (SOW), defining the work contracted to AT, requested engineering services to provide improved electroplated CBN wheel specifications and grinding cycles for creep feed grinding. The goals of this project were to eliminate the use of straight oil coolant and to improve grinding cycles and wheel life (more parts per wheel). Improvements were to be developed and documented through use of statistical methods. Rephrased, the objective of the AT work was to identify the (1) revised wheel specifications, and (2) revised process specifications needed to restore any lost wheel life associated with converting to a non-straight oil coolant. The understanding of the AT - P&W Development Team was that converting to a non-straight oil coolant would result in (1) reduced wheel life, (2) longer cycle time, and (3) potentially reduced part quality. The mission of this work was to identify specific engineering practices that would restore the lost productivity. The principal focus of this work was wheel life and identification, through valid statistical experimentation, of the factors that govern this creep feed grinding process variable. Oil To Water Debit Reference 1 observes that It has long been accepted that CBN grinding wheels provide the most outstanding performance when used with lubricating-type fluids with an absence of water. These fluids not only provide less heat generation but also reduce or eliminate the chemical decomposition associated with CBN and high-temperature steam. The formation of an oxide (B 2 O 3 ) on the surface of a CBN particle creates a protective layer to deter further oxidation. However, this oxide is soluble in high temperature water and can allow further oxidation of the CBN particle. These reactions, although very slow, can cause accelerated breakdown of the CBN abrasive particles and, thus, shorten wheel life. The use of straight oil grinding fluids minimize this effect. The performance debit on CBN plated form wheels associated with use of water-based coolants was not known. The GE Superabrasives report cites that resin bond CBN wheels, used with straight oil, outperformed all types of waterbased fluids by factors of 1.5 to 9 times. No comparable data for electroplated CBN wheels was found. Candidate Process Improvement Domain The objective of the AT - P&W work was to identify improvements that could be implemented into the current P&W manufacturing operation. This is a common need of American manufacturers. Major implications from this restraint were that AT s improved wheels must operate within the performance envelope of existing (1) equipment, (2) major tooling, and (3) applicable processing procedures. A practical implementation budgeted per machine was set at $5,000 to $10,000. Hence new high speed spindles and rigid tooling systems were not viable improvements. Technical Approach The Abrasive Technology/Pratt & Whitney support team for the first contract included Master Chemical Corporation, GE Superabrasives, Maegerle, Inc. BIRL Industrial Research Laboratory of Northwestern University, and Advanced Manufacturing Sciences and Technology (Dr. Stuart Salmon). The AT program began October, 1991 and concluded in November, Technical Plan The program content was planned to focus on identifying and validating improvements through testing, i.e. grinding. The overall road map for the AT work is presented in Figure 1. Principal elements of the contracted work were: Engineering Design Data Collection Brainstorm Variables Establish Baselines Arrange for Test Machine Testing Feasibility Screening Baseline Validation Process Optimization Process Verification GRINDING FLUID CHARACTERISTICS 1 = Poor 4 = Best SYNTHETICS SEMI-SYNTHETICS SOLUBLE OIL STRAIGHT OIL HEAT REMOVAL LUBRICITY MAINTENANCE FILTER ABILITY ENVIRONMENTAL COST WHEEL LIFE TABLE 1 5

5 Interface to AT Operations Manufacturing Lab Analysis Program Management Program Overview The Data Collection phase did not identify the existence of any previous published Plated CBN Form Wheel research or development outside of Pratt & Whitney. Significant process data was collected from the P&W manufacturing engineers and Abrasive Technology and Process Engineering staff. Further, a joint AT/P&W assessment was conducted of applicable work done at (1) University of Massachusetts, (2) University of Connecticut, (3) GE Superabrasives, and (4) Advanced Manufacturing Sciences and Technology. This background work identified a large number of candidate process variables and the limitations of current non-plated grinding research methods to plated wheels. Straight 1A1 Type Wheel vs. Form Wheel Development While considerable grinding is accomplished with simple, 1A1 Type, grinding wheels, a principal benefit of plated wheels is form grinding. The AT/P&W technical team elected to conduct the development activity on zero form 1A1 wheels. This approach is (1) more economical, and (2) does not restrict the results to a specific form. A specific profile, detailed in Figure 2, was selected for demonstrating the applicability of the derived improvements to a form wheel application. The selected form wheel demonstration included two noteworthy challenges: (1) Use of a cobalt alloy based material, and (2) A severe profile incorporating a Depth to Width ratio significantly greater than 1. Note that this wheel profile incorporates three grinding zones referred to as (1) Shoulder, (2) Large Chamfer, and (3) Throat. Each grinding zone represents a distinct grinding condition with Collect Data Brainstorm Variables Estimated Performance Variables Manufacturing (Internal) Engineering Design Arrange Machine Test Baseline Validation Feasibility Screening (F/S) Process Optimization (1A1) ATI Verification (Form Wheel) F/S "B" vs. "C" DOE 1st scale 2nd scale Final scale Lab Analysis Conduct Test Program Stop P&W Verification (Form Wheels) Program Management FIGURE 1 6

6 respect to such engineering parameters as (1) Grinding forces, (2) Material removal rates, and (3) Effectiveness of coolant placement. "SHOULDER" D= "THROAT" FIGURE 2 W=.456 "LARGE CHAMFER" D W >1.4 Life Testing A unique feature contrasting a plated CBN grinding wheel from other types of grinding wheels is the existing of a single layer of abrasive. Traditional grinding wheel Life development incorporates use of one or more accelerated measures for extrapolating or predicting wheel life. Dr. Steve Malkin s text, Grinding Technology (4), defines a performance index commonly used to characterize wheel life, or wheel-wear resistance, as the grinding ratio; also referred to as the G-ratio or G. The G-ratio is the volume of material removed per unit volume of wheel wear. No precedence was located for using G-Ratio type measures to compute plated wheel life. A second accelerated wear parameter investigated was existence of a predictable characteristic response, or signature, of the Percent Motor Load output from the spindle motor, as a function of CBN plated wheel life (as measured by number of parts produced). Each specific wheel/machine/ workpiece combination does exhibit a characteristic trace. However, numerous 1A1 full life tests in a water-based coolant failed to exhibit any signature that could be reliably used to develop Estimate of Life for a CBN plated wheel. Hence, the AT/P&W team concluded that there was no acceptable substitute for Full Life Testing. End of life of a CBN plated wheel was defined as either (1) Existence of excessive burning or (2) Loss of wheel form. Test Wheel Configuration To reduce cost and complexity, two simplifying decisions developed: (1) Use Type 1A1, straight form wheels and (2) Use six inch diameter (scaled) wheels. The technical approach was to develop the abrasive coating, i.e. wheel, and machine application specification improvements, using wheels with essentially no form; i.e. a form factor of 0. P&W development engineers additionally reported previous success with performing development work on scaled wheels. Smaller, straight wheels offer three benefits; (1) they are less expensive to produce, (2) less expensive to test, and (3) the results can be more universally applied to form wheel applications. Full form wheel testing was performed to at the conclusion of the first program to verify applicability of identified improvements. Plated CBN Creep Feed Grinding Process Variables During the Engineering Design phase of the program, the AT team completed identification of process variables believed to effect CBN plated wheel performance. The impact selected variables had on improved plated CBN wheel performance was evaluated via test grinding in one of three test phases: (1) Feasibility Screening, (2) Process Development, and (3) Process Verification. Identified process variables were either assigned to (1) Constant parameters; outside of the AT development program, (2) Feasibility Screening, or (3) Process Development. Constant Parameters These are process variables that either do not significantly effect performance or are outside of the scope of the AT program. Variables assigned to Constant Parameters were: Wheel blank material Machine HP Fixture Rigidity Machine Temperature Coolant Temperature Down Grinding Wheel Concentricity Process Development Variables assigned to the Process Development category were those that were either: (1) Recognized as a primary variable impacting wheel life, or (2) A process variable that could not be adequately screened within the Feasibility Screening module. Process Development variables were evaluated on the Maegerle Test System, located in Schaumburg, Illinois and include: Abrasive Concentration Coolant Formulation Coolant Dynamics (Velocity, Pressure, and Flow) Nozzle Designs Nozzle Position Wheel Balance Feasibility Screening The remaining process variables were assigned to the Feasibility Screening module for further evaluation. The goal of feasibility screening testing was to economically obtain information pertinent to evaluation of plated CBN wheels. Analysis of the generated data led to assignment of the process variable to either the Constant Parameters or Process Development category. Feasibility screening was performed at the GE Superabrasive Americas Application 7

7 Development Center in Worthington, Ohio. Feasibility screening variables included: CBN Abrasive Type CBN Abrasive Size Bonding System Protective Coatings Coolant Concentration Feed Rate SFPM Depth of Cut (DOC) Standardized Tests Three test setups were employed corresponding to (1) Feasibility Screening using 1A1 wheels at GE Superabrasives development lab, (2) Process Development using 1A1 wheels at Maegerle, and (3) Process Verification using form wheels at Maegerle. Feasibility Screening at GE Superabrasives The majority of the feasibility screening work was performed in cooperation with the technical staff at GE Superabrasive Development Laboratory, Worthington, Ohio. The test machine was a Cincinnati Milacron I.D. Plunge Grinder. The test employed was a standard pre-existing procedure. Straight, (1A1) Type, wheels, manufactured to various specifications, were tested under tightly controlled conditions. Each test required approximately four (4) to six (6) hours of total time and hence was reasonably economical compared to the full life testing at Maegerle. The test material was cobalt. The coolant was Master Chemical VHPE200 at 10% concentration. Wheel speed was 9,000 SFM. The typical metal removal ratio per pass was about in 3. Figure 3 is a schematic diagram of the plunge grinding feasibility experimental testing. Plunge grinding, as shown in Figure 3, is recognized to not be an exact re-creation of the creep grinding process. A comparative analysis of the plunge grinding test with the test conditions developed for Maegerle was completed and found to be favorable. Hence, the screening plunge test was an economical means of discriminating process variables from the Process Development portion of the program. COBALT F n NORMAL FORCE COOLANT FEED RATE Comparison of the Plunge Grinding Feasibility Test and Tangential Creep- Feed Grinding at Maegerle MAEGERLE STRAIGHT GRINDING Maximum normal infeed rate (MNIR) is defined as the Feed Rate of the wheel into the Work Piece at the top of the Arc of Cut as measured in the direction normal to the wheel surface as shown in Figure 4. In creep feed grinding, the MNIR value represents the specific performance parameters of each wheel and can be calculated from the depth of cut (a) and the feed rate (V W ) as follows: FIGURE 4 FEED RATE (Vw) MAXIMUM NORMAL INFEED RATE = FEED RATE X SIN 0 SIN 0 = A B WHERE A B = r r s2 - (r-a) s s MNIR = r s A B r s A 0 F h X V w = x = INCH / MIN. MNIR a =.060 A typical MNIR for 1A1 6" diameter wheels tested at Maegerle employing straight grinding was calculated as follows: MNR = x 4.7 = inch/min. 3 By comparison, the calculated MNIR for the GE plunge feed test was calculated to be 0.480"/min. Using this approach, it can be shown that the grinding conditions, generated by the GE plunge test, simulates MNIR conditions equivalent to the mid-point between the top and the bottom of the arc length employed by the Maegerle creep feed grinding conditions as shown in Figure 5. F y B 2 F h HORIZONTAL FORCE FIGURE 3 8

8 In conclusion, the results obtained from the GE plunge testing provides realistic discrimination for evaluating different bonding systems in a short time and a comparatively economic way. Note, that some of the test results were later reconfirmed during creep feed grinding tests at Maegerle. Maximum normal infeed rate on Maegerle "/min. Incremental Normal infeed Around the Arc of Cut Maegerle, Inc., located in Schaumburg, Illinois, was chosen for providing the base facility to conduct both the Process Development and Process Verification testing. Preparation and certification of the Maegerle Test System was jointly accomplished by AT, P&W and Maegerle technical staff. It is important to recognize that the Maegerle Test System is considerably more than a grinder. The major components of the system are identified in Table 2. Maegerle Test System (MTS) Certification Prior to testing, a certification process was engineered to define the capabilities of the overall system. An overview of the principal activities is shown in Table 3. Maximum normal infeed rate on GE rig 0.480"/min. TOP " Arc Length (inches) FIGURE 5 Process Development and Verification at Maegerle BOTTOM AT was responsible for establishing a facility to test both six (6) inch diameter 1A1 wheels and ten (10) inch diameter form wheels under controlled conditions within the performance envelope of selected P&W grinding systems. MTS CERTIFICATION PROCESS APPLICABLE SENSORS Spindle Power X,Y,Z Forces (Kistler Load Cell) Coolant Pressure Coolant Temperature Coolant Flow Rate PC Clock MACHINE FUNCTION VERIFICATION Lateral Index Feed Rate at two RPM Settings: 4,560 and 5,700 Infeed Rate (At two RPM Settings: 4,560 and 5,700) METHODOLOGY Discrimination using "Isoplots" Percent Error <5 at Both High and Low Ranges Regression Analysis: Isoplots, Slope/Intercept, R2 Sampling Plans: Sensors: 20 Points Evenly Spread across operating range (using certifies/calibrated inputs) Machine Functions: 3 readings at 7 levels randomly sequenced at 2 RPMs MAEGERLE TEST SYSTEM MACHINE DESCRIPTION Model Maegerle MFP CNC Controller GE Fanuc 15-MA Spindle Motor 50 KW (67 > 1,500 RPM Maximum RPM 6,000 COOLANT SYSTEM Filter Type Flat Bed Paper Band Reservoir Capacity 1,070 Gallons Maximum Flow Rate (Water) 110 Gallons/Minute (GPM) Chiller 5 HP 57,600 BTU/ Hour High Pressure Cleaning 6 1,200 PSI SENSORS Dynamometer Kistler (X, Y, and Z) Spindle Power Consumption Coolant Flowrate Coolant Pressure Coolant Temperature Spindle Vibration Accelerometer Spindle RPM Spindle Location (X, Y and Z) INSTRUMENTATION Data Acquisition P & W Supplied System 10 Readings Per Second Data Storage 486 Microprocessor 120 HD Labtech Notebook Software Data Processing Statgraphics 5.0 Plus Software TABLE 3 At the completion of the certification work, all sensors and machine functions met or greatly exceeded pre-planned acceptance criteria. It is noted that certification of the sensors was not straight forward. The following sensors required significant calibration and/or adjustment. Motor Load Coolant Flow One of the Kistler Forces (Dynamometer Was New ) The difficulty with the Motor Load sensor is noteworthy in that most grinding research programs rely on this process variable. Grinding Strategies Two grinding procedures were developed for use during the testing at Maegerle; one procedure for 1A1 wheels, and a second procedure for the selected form wheel. Figures 6 and 7 depict the configuration of the test material and the grinding sequences; also referred to as the grinding test strategy. TABLE 2 9

9 EXPERIMENTAL METHODS PHILOSOPHY UTILIZE A VARIETY OF TOOLS & 3 Level Full factorial DOE's "B" vs. "C" Six Pack Testing Using a Turkey End-Count Technique Looking for "Big" Differences - Single Test Runs Process Test, Evaluate & Decide Upon Next Step Institutionalize Important Variables as "Better" Level Accept Some Risk to Keep Sample Sizes Down 18 FIGURE 6 Grinding Strategy: 1A1 6.0 Inch O.D. wheel x inch wide. Five roughing passes across with nominal overlap to negate wheel edge effects at specified infeed rates. STATISTICALLY SIGNIFICANT CONCLUSIONS ARE POSSIBLE LOOK FOR HIDDEN INTERACTIONS ADOPT SMALL SAMPLE SIZES EMPLOY PROGRESSIVE EVALUATION & IMPLEMENTATION TABLE 4 PARALLEL TO PART AXIS CASTING PERPENDICULAR TO WHEEL AXIS CBN PLATED WHEEL CBN PLATED WHEEL CASTING GRINDING FIXTURE TABLE RIGHT SIDE VIEW FIGURE 7 SPACER BLOCK KISTLER PLATE Grinding Strategy: Demonstration Form Wheel Alternate one (1) roughing pass and one (1) finishing pass. Each pair of roughing and finishing passes constitutes one (1) equivalent part. Experimental Methods Throughout the program, continuous effort was expended to employ appropriate Design Methodologies for the time and budget available. Considering that the single most significant engineering measure of this program was wheel life, and the significant cost associated with testing a single wheel to full life, joint collaboration between AT and P&W technical staffs was continuously required. The overall philosophy for using experimental methods is summarized in Table 4. Using all aspects of the philosophy summarized in Table 5, over 100 wheels were tested: Five Inch 1A1 Wheels at GE Superabrasives: Six Inch 1A1 Wheels at Maegerle: Ten Inch Form Wheels at Maegerle: Results Manufacturers currently using plated CBN grinding wheels in a straight oil coolant for creep feed grinding applications should not expect to be able to simply change coolants and retain performance. There is a debit. Through attention to a variety of factors, including specification of the grinding wheel, the lost productivity can be restored. A comprehensive and published engineering characterization of electroplated superabrasive tooling does not yet exist. However, many of the parameters required for such a characterization have been investigated during the course of this program. Though the detailed test results cannot be released, the following comments can be made. Generally speaking, the published conclusions reached by other investigators, for other forms of CBN grinding wheels, hold true for plated CBN creep feed grinding. Government Sponsored Development Through the cooperation of Pratt & Whitney and the United States Air Force, Abrasive Technology has been granted permission to present the preliminary results of our work prior to issuance of the final report. This program might well stand as a blueprint for how American manufacturing firms can cooperatively work with our government to enhance our competitiveness in the decade ahead. 10

10 The developed bonding system provides a 25% increased life (Statistical Significance at 95% Confidence) in water based coolants from previous standard construction. Using 1A1 type wheels, initial water baseline testing showed a 41% reduction in life of AT s standard construction compared to the oil baseline results. Base line productivity, established with straight oil coolant, can be restored (and exceeded) through combination of the developed bond and associated grinding process parameters. CBN plated wheels for high speed grinding (<10,000 SFPM), using water based coolant, critically requires high pressure cleaning jets. Coolant concentration between 10% and 30% had no significant effect on wheel life. TiN coating was ineffective statistically, for extending life of plated CBN wheels under high speed creep feed grinding conditions. Infeed rate is a very strong driver for wheel life. CBN 500 was statistically superior to CBN 570 and ABN 600. There is a set of conditions under which a CBN plated wheel can grind a deep form in cobalt with considerable wheel life and part quality. TABLE 5 References 1. Alan C. Carius, Effect of Grinding Fluid Type and Delivery on CBN Wheel Performance. Presented at Society of Manufacturing Engineers, Modern Grinding Technology, Novi, Michigan, October, Fritz. G. Frafft and Paul Grieb, Grinding with plated CBN Wheels. American Machinist, April, K.V. Kumar, R.R. Matarrese, E. Ratterman, Control of Residual Stress in Production Grinding with CBN. 40th Annual Earthmoving Industry Conference, Peoria, Illinois, April 11, Steve Malkin, Grinding Technology; Theory and Applications of Machining with Abrasive. Ellis Horwood Limited Publishers, England,

11 World headquarters - Lewis Center, Ohio USA abrasive technology WORLD HEADQUARTERS EUROPEAN HEADQUARTERS ASIAN HEADQUARTERS Abrasive Technology, Inc. Abrasive Technology Ltd. Abrasive Technology Asia Pacific Pte Ltd 8400 Green Meadows Dr. Roxby Place, Fulham Blk 1093 Lower Delta Rd /13 P.O. Box 545 London Tiong Bahru Industrial Estate Lewis Center, Ohio USA SW6 1RT United Kingdom Singapore Ph: Ph: Ph: Fax: Fax: Fax: Abrasive Technology 2/06