1、02FTM1The Effect of Chemically AcceleratedVibratory Finishing on Gear Metrologyby: J. Arvin, Arrow Gear Company, A. Manesh, Power TransferSystems Manufacturing, M. Michaud, G. Sroka, andL. Winkelmann, REM Chemicals, Inc.TECHNICAL PAPERAmerican Gear Manufacturers AssociationThe Effect of Chemically A
2、ccelerated VibratoryFinishing on Gear MetrologyJoseph Arvin, Arrow Gear Company, Ali Manesh, Power Transfer SystemsManufacturing, Mark Michaud, Gary Sroka, Lane Winkelmann, REMChemicals, Inc.Thestatementsandopinionscontainedhereinarethoseoftheauthorandshouldnotbeconstruedasanofficialactionoropinion
3、of the American Gear Manufacturers Association.AbstractChemically accelerated vibratory finishing is a commercially proven process that is capable of isotropicallysuperfinishingmetalstoanRa1.0in.Surprisingbenefitswerefoundwhenthistechnologywasappliedtogears.Suchgearshavereducedfriction,wearandnoise.
4、 Contactfatigue(pitting)andbendingfatiguearealsoreducedoreliminatedboth in laboratory testing and field trials.Since the metal removal rate using this process is dependent on the amount of surface rubbing by the media, gearengineers are often concerned with its impact on gear geometry.Inthispaper,ae
5、rospaceAGMAQ13spiralbevelgearswerestudied.ItwasshownthattheamountofmetalremovedtoIsotropicsuperfinish(ISF)thesurfaceisbothnegligibleandcontrollable.Allofthegearsweresuperfinisheduniformlyand were determined to be within tolerance.Inadditiontoprofilometryandmetrologydata,mediaselectionandmetalremoval
6、monitoringproceduresaredescribedthat ensure uniform surface finishing, controllability, and preservation of gear metrology.Copyright 2002American Gear Manufacturers Association1500 King Street, Suite 201Alexandria, Virginia, 22314October, 2002ISBN: 1-55589-801-71 The Effect of Chemically Accelerated
7、 Vibratory Finishing on Gear Metrology Joseph Arvin*, Ali Manesh+, Mark Michaud#, Gary Sroka#, Lane Winkelmann# *Arrow Gear Company, Downers Grove, IL + Power Transfer Systems Manufacturing, Chicago, IL # REM Chemicals, Inc., Brenham, TX Introduction Chemically accelerated vibratory finishing enhanc
8、es the performance of components that are subjected to metal-to-metal contact or bending fatigue. When the resultant surface has an Raof approximately 3.0 in. or less and a non-directional surface pattern, it will be referred to here as an Isotropic Superfinish (ISF). Such surfaces are unique in the
9、ir remarkable ability to reduce friction1, 2, 3, 4, wear1, 2, 3, 4, noise5, as well as contact3, 6, 7, and dynamic fatigue8when compared to similar surface finishes produced by other techniques. There has been increasing interest in applying this process to gears since industry is being driven to pr
10、oduce higher cycle life gears at increased power densities. ISF is produced in vibratory finishing bowls or tubs. A proprietary active chemistry is used in the vibratory machine in conjunction with high-density, non-abrasive ceramic media9. When introduced into the machine, this active chemistry pro
11、duces a stable, soft conversion coating on the surface of the metal part(s) being processed. The rubbing motion across the part(s) developed by the machine and media effectively wipes the conversion coating off the peaks of the parts surfaces, but leaves the valleys untouched. (No finishing occurs w
12、here media is unable to contact or rub.) The conversion coating is continually re-formed and rubbed off during this stage producing a surface smoothing mechanism. This process is continued in the vibratory machine until the surfaces of the part(s) are free of asperities. At this point, the active ch
13、emistry is rinsed from the machine with a neutral soap. The conversion coating is rubbed off the part(s) one final time to produce the ISF surface. In this final step, commonly referred to as burnishing, no metal is removed. The ISF process removes more metal from the region of a part where higher m
14、edia contact occurs. Therefore, more stock will be removed from the addendum than from the root fillet of a gear. Naturally, gear engineers and designers question whether the ISF process will negatively affect gear geometry especially for AGMA Q11 and higher. This paper presents before and after (IS
15、F processed) metrology data that is representative of the 11 AGMA Q13 spiral bevel gears and pinions examined during this study. It was concluded that the ISF processed gears and pinions maintained their Q13 rating. Description of Gears Figure 1 shows a schematic of the gearset used in this study, w
16、hich were manufactured by Arrow Gear Company. The alloy was SAE 9310 case hardened to 57-62 HRC. The initial surface roughnesses were: Pinions (in.) Gears (in.) Ra7 to 11 5 to 13 Rz42 to 81 33 to 87 Ra: Arithmetical Mean Roughness (DIN 4768) Rz: Mean Peak-to-Valley Height (DIN 4768/1) Figure 2 shows
17、 photographs of a gearset and the masking that protected the threaded holes and bearing areas during ISF processing. 2 Figure 1. Schematic of gearset used in this study. Figure 2. Photographs of a gearset showing protective masking of threaded holes and bearing areas. The ISF Process Smoothing Princ
18、iple Before proceeding with the rest of the discussion, it is important to discuss the basic principles of the ISF process in greater detail. The process utilizes conventional vibratory finishing equipment and high density, non-abrasive finishing media9to produce isotropic surface finishes which can
19、 have an Raas low as 1.0 in. Refer to Figure 3. At the start of the ISF process (Step 1), the original metal surface reacts a first time with the active chemistry, forming the first conversion coating (Step 2). The vibratory machine and non-abrasive media produce an effective rubbing motion on the s
20、urface of the metal part(s) (Step 3). This exposes the peaks of the metal surfaces to a second reaction (Step 4), re-forming the complete conversion coating. The process of conversion coating re-formation and removal (Step 5) is continued through many successive cycles. This process is continued unt
21、il the metal parts are smoothed to the required surface finish quality. Once the required surface finish quality is achieved, the active chemistry from the smoothing stage of the ISF process is drained away, and a neutral, burnishing soap is introduced into the vibratory machine. The burnish removes
22、 all remaining conversion coating (Step 6) from the surface of the part(s), producing a mirror-like appearance, while imparting a mild rust preventive to the surface. The part(s) are ready for unloading and the ISF process is complete. Importance of Media Selection Part of the art to successfully fi
23、nishing gears is the initial selection of the proper media shape, size, and mixture. Once the media is chosen, the ISF process will repeatedly finish gears identically because the media is non-abrasive and therefore has a very low attrition rate. Thus its size and shape remains stable over time. Fig
24、ure 4 shows the media selected to finish the spiral bevel gears examined in this study. 3 Figure 3. Description of the ISF process. Mass Finishing and Process Robustness The ISF process is a mass finishing operation whereby hundreds of gears can be simultaneously processed in the same machine. If al
25、l of the raw gears placed in the vibratory machine are identical at the start, then they are all identically finished at the end of the process. Every gear tooth will have the same surface finish and geometry since the parts continually and randomly move through the vibratory machine and statistical
26、ly experience the same chemical and media exposure. If one tooth on a gear has its tooth thickness reduced by 0.0003 inches, then every tooth on that gear and every gear in the finishing machine will have its tooth thickness reduced by the same amount. Therefore, there is no need for costly final in
27、spection of each and every gear as must be done after grinding or honing. In addition, the simplicity of the process yields a very robust manufacturing method. Vibratory machines are run for years without any maintenance except for minor lubrication. The media is non-abrasive so it retains its shape
28、 and size for long periods of time. The active chemistry is also stable for well over a year. The important parameters that control the surface finishing operation are the number of gears in the finishing machine, the concentration of the active chemistry, the flow rate of active chemistry, and the
29、processing time. All of these parameters are easily controlled. The process lends itself to automation, and has been commercially used over the past 19 years. Description w/w% Image Non-Abrasive, Polyester Resin (plastic) 3/4 in. cone 68 High Density, Non-Abrasive9 (ceramic) 3 x 6 mm Angle cut cylin
30、der 16 High Density, Non-Abrasive9(ceramic) 3 x 6 mm Straight cut triangle 16 Figure 4. Media mixture used to ISF process gearsets. (Patent Pending) Correlation Between Rzand Metal Removed One concern expressed by engineers in their initial appraisal of the ISF process is whether or not the process
31、has a detrimental effect on gear geometry. At the outset then, it is comforting to know that there is a simple method of estimating the amount of stock removal to attain the desired low surface roughness. The maximum Rz, for the 11 gearsets is 87 in. Therefore, 0.000087 in. of stock must be removed
32、to completely eliminate the grind lines (asperities). Previous measurements of ISF processed gears using the same media mixture have shown the stock removal at the dedendum to be approximately 80% that of the 4 addendum. To a good approximation, a maximum of 0.00011 in. of stock needs to be removed
33、to obtain an optimally smoothed dedendum. Estimation of Processing Time From the above estimation, it is now possible to predict the processing time. The ISF process for aerospace components typically removes 0.00007 to 0.00010 in. of stock per hour. This is dependent on the alloy and the specific h
34、eat treatment. Therefore, the parts will have a processing time between 1.1 to 1.6 hours. Process Control It is possible to ensure the repeatability of stock removal from run to run with a simple quality control tool. A smooth ISF witness coupon similar to that shown in Figure 5 is processed along w
35、ith the gears. The coupon is case hardened SAE 8620 to approximately 58 HRC with a circle milled so that its thickness can be measured at exactly the same location. Periodically during the processing, the witness coupon can be retrieved from the vibratory machine and its thickness quickly measured w
36、ith a micrometer. During the initial process setup, the gearset is processed until the dedendum is essentially line-free (asperity-free). The stock removal of the witness coupon is determined. In all future runs, the witness coupon can be used as a quality control tool to ensure all of the gears are
37、 identically processed. ISF Processing Parameters 1) The samples were randomized and divided into four groups. Each group was processed separately to demonstrate repeatability of the ISF process. Group I.D. # I 39 33 - II 20 26 24 III 35 28 23 IV 32 22 25 2) Vibratory Machine Parameters: Used for al
38、l four tests. Vibratory Machine Type: Bowl Volume: 3-ft3Amplitude: 4.5 mm Lead Angle: 60oFigure 5. Photograph of witness coupon used to monitor stock removal. 3) Cleaning Step: The rust preventive on the ground gears was removed to ensure uniform reaction for all four groups as follows: Burnish Chem
39、istry (cleaner) Concentration: 1.0 v/v% Flow Rate: 10.0 gph Time: 1.0 hours 4) Smoothing Step: Used for all four groups. Active Chemistry Concentration: 10.0 v/v% Flow Rate: 1.0 gph Group Processing Time Dimensional Reduction of Witness Coupon (hours) (in./side) I 1.25 0.00010 II 1.25 0.00010 III 1.
40、25 0.00010 IV 1.25 0.00010 5) Burnishing Step: Used for all four groups. Burnish Chemistry Concentration: 1.0 v/v% Flow Rate: 15.0 gph Time: 1.5 hours 5 A photograph of an ISF processed pinion is shown in Figure 6.Typical before and after surface roughness measurements of the gearsets are shown in F
41、igure 7. Figure 6. Photograph of pinion after ISF. Metrology Data Figures 8 to 17 are before and after Hofler gear metrology charts for set # 25 pinion and set # 35 gear. The information is typical of the 11 gearsets that were subjected to the ISF process. Pinion Member The charts show that an avera
42、ge of 0.00015 in. stock has been removed from each flank of the pinion gear tooth surface (average change in tooth thickness of 0.0003 in.). Also there was a change of tooth geometry by an average of 0.0001 in., which should not present a problem with the performance of the pinions. There were two p
43、inion members, which had more stock removal than the others. The pinion member of set #22 and set #32 both had a tooth geometry change of 0.0002 in. In both cases, the deviation was located at the convex heel near the top land, which should not present any major problem. At the present time, there i
44、s no explanation for the anomaly in the pinion of set # 22 and set #32. Set # 25 was processed along with these, but its measurements showed normal stock removal. The ISF process has excellent repeatability as demonstrated by the identical stock removals and processing times of all four groups of ge
45、arsets. In addition, the initial Rz estimation (0.0001 in.) is useful in approximating the stock removal required (0.00015 in.) to completely eliminate the grind lines (asperities) from the flanks. Gear Member On the gear members, there was a change of tooth geometry by an average of 0.0001 in. Also
46、, the gear members had the same stock removal from the surface as the pinions. The gears had an average tooth thickness change of 0.00015 in. per tooth surface, or 0.0003 in. total. The ISF process has excellent repeatability as demonstrated by the identical stock removals and processing times of al
47、l four groups of gearsets. In addition, the initial Rz estimation (0.0001 in.) is useful in approximating the stock removal required (0.00015 in.) to completely eliminate the grind lines (asperities) from the flanks. Figure 7. Typical before and after surface roughness profiles of the gearsets. 6 Fi
48、gure 8. Before and after Flankform Measurement of set # 25 pinion. 7 Figure 9. Before and after Tooth Thickness Measurement of set # 25 pinion. 8 Figure 10. Before and after Precision Index Measurement of set # 25 pinion. 9 Figure 11. Before and after Tooth Depth Measurement of set # 25 pinion. 10 F
49、igure 12. Before and after Tip Angle Measurement of set # 25 pinion. 11 Figure 13. Before and After Flankform Measurement of Set # 35 Gear 12 Figure 14. Before and after Tooth Thickness Measurement of set # 35 gear. 13 Figure 15. Before and after Precision Index Measurement of set # 35 gear. 14 Figure 16. Before and after Tooth Depth Measurement of set # 35 15 Figure 17. Before and after Tip Angle Measurement of set # 35 gear. 16 Conclusions 1. The ISF process can isotropically superfinish the flanks of spiral bevel gears and pinions while maintaining AGMA Q13 specification
