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1、01FTM3 Automated Spiral Bevel Gear Pattern Inspection by: S.T. Nguyen, A. Manesh, INFAC/IIT Research Institute, K. Duckworth and S. Wiener,Honeywell Engines and Systems TECHNICAL PAPER American Gear Manufacturers Association Automated Spiral Bevel Gear Pattern Inspection S.T. Nguyen, A. Manesh, INFA
2、C/IIT Research Institute, K. Duckworth and S. Wiener,Honeywell Engines and Systems Thestatementsandopinionscontainedhereinarethoseoftheauthorandshouldnotbeconstruedasanofficialactionor opinion of the American Gear Manufacturers Association. Abstract Spiralbevelgearsaretypicalcomponentsfoundinmostgas
3、turbineenginesthatareusedinawidevarietyofmilitaryand commercialapplications. Thesegearsareamongthemostdifficultandcostlycomponentstodevelopandmanufacture. Manufacturingprocessesrequiredtoproducespiralbevelgearsarehighlyoperatorintensive,makingthemparticularly costly in todays small lot production en
4、vironment. Compounding these problems are requirements to produce replacementpartsforoperationalsystemsthathavebeenoutofproductionformanyyears.Thisisparticularlytrueifthe original equipment manufacturer (OEM) no longer supports the system. To overcome these multiple issues, the gear production cente
5、r at Honeywell Engines 2) multiple loops of trial and error machining; and 3) inspection based on physical master gears, inconsistent test equipment and operator interpretation-based evaluations yielding Pass-Fail designations. In the existing gear design process, the design engineer selects initial
6、 gear set parameters, (i.e. gear ratio, pitch, pressure angle, etc.) based on the specified performance requirements for the gear train. Based on the information, a load bearing analysis is performed using a computer model. This computer model also generates an “undeveloped summary”, which is a set
7、of kinematic instructions for specific generators and grinding machines. This undeveloped summary is used as a starting point by manufacturing engineers to manually produce a bevel gear. However, the undeveloped summary typically does not produce satisfactory bearing patterns and requires extensive
8、iterative development to obtain a good gear set. All the gear teeth have to be cut in order to evaluate parts on the existing inspection equipment. This is a costly and a time consuming process. In aerospace gearing there are currently no fully automated methods to provide feed back of error conditi
9、ons and generate corrections when errors are found in the first trial cuts of spiral bevel gear teeth. Identification of proper machining changes is dependent upon the skill of the engineer or operator and their interpretation of the design intent. The process for pattern, run-out, and backlash insp
10、ection using industry-standard Gleason single flank roll-testers still involves the interpretation of colored marking compounds on mating gear teeth. The roll test requires that a working master gear be meshed with a production gear on a gear tester as shown in Figure 1. Prior to running, the gear-m
11、arking compound is applied lightly to the gear and pinion teeth. The machine can be hand cranked or motor-driven with a light load applied to the gear. The resulting contact pattern, Figure 2, on the gear and pinion flanks due to the surface contact between the mating teeth and the gear compound are
12、 examined. The horizontal and vertical (H and V) offsets to the pinion axis with respect to gear axis are also adjusted to span the maximum and minimum allowed per the specification. Contact patterns are then compared against the Bevel Gear specifications to ensure that they are within the acceptabl
13、e range. This type of subjective evaluation of pattern comparison makes it difficult to identify a consistent method for adjustments. Since the industry-wide production acceptance methodology requires a sample of each bevel gear production lot to be mounted and tested in a similar fashion described
14、previously, variation in gear quality are possible. Figure 1. Universal Gear Tester Figure 2. Zerol and Spiral Bevel Gear Mating Contact Patterns Are Difficult to Interpret Properly. A master spiral bevel gear is an inspection tool that has most of the features of a production gear. It is produced o
15、n the same type of equipment used to manufacture the production gear design. It is a control tool that defines the shape of the gear teeth. The specific elements -,-,- 3 being controlled are the tooth flanks and tooth thickness. All subsequent production members are to duplicate the master control g
16、ear in the area of contact pattern and size. The master gear and master pinion of a gear set are made to be identical to gears which had been developed, benched tested, and proven to provide the best possible meshing conditions in an actual gear box mounting and tested through an appropriate range o
17、f loads and temperatures. The terminology for master gears varies among companies, but commonly there are three tiers of physical Master Gears. They are Grand Master, Surveillance Master and Working Master. Working Masters are generally used for production roll testing while Surveillance Masters are
18、 used for periodic calibration of the Working Masters. A Grand Master is used exclusively to calibrate Surveillance Masters. Objective: The objective of this project was to significantly advance the state of the art in US Aerospace spiral bevel gear production development, manufacturing and inspecti
19、on. Specifically, the project developed a closed-loop manufacturing process that would reduce development times for new designs, implemented quantitative inspection system, reduced variation and reduced development and production cost. Additionally, the use of digital electronic master data for acce
20、ptance of production bevel gears in lieu of physical gear master was developed and topography-based tolerancing limits for new zerol and spiral design was established. Approach: To accomplish the objective, tight integration of hardware and software capable of closing the loop from designing, manufa
21、cturing, inspecting to correcting spiral bevel gear was deemed necessary. Once completed, a process that uses a digital gear master for production part acceptance instead of the physical gear master could be developed. In contrast to the existing gear manufacturing process described in the Backgroun
22、d Section, it was desirable, through the use of gear designing software, to be able to generate spiral bevel gear data model and automatically convert it into machine instructions after gear loads and contact pattern are successfully simulated. The machine instructions would then be downloaded direc
23、tly to a gear generator or a grinder for tooth generation. All inspections would be completed on an automated gear inspection system (AGIS) against an electronic master database thereby providing quantitative measurements. Through a separate software module, corrections for discrepancies due to mach
24、ining inaccuracies would be linked back to the first part cutting instructions to permit closed-loop corrections. The closed-loop correction will ensure that all parts produced after the first article acceptance will meet the design intent. The desired end state system and the automatically informat
25、ion flow are depicted in Figure 3. In order to develop a process that uses digital gear master for production part acceptance instead of the physical gear master, the following issues need to be addressed: 1) How does the bearing pattern simulated by the software compare with the bearing pattern gen
26、erated from the actual rolling test for a given design? 2) What inspection outputs from the AGIS inspection system need to be controlled to ensure the desired bearing pattern? 3) Based on an existing Bevel Gear Specifications, how do the tolerances allowed on the bearing pattern tapings translate ba
27、ck as tolerance limits on the identified output controlled parameters? Figure 3. Information Flow Through Closed-Loop System. A multi-phase approach, which involves system evaluation and selection, system set-up, -,-,- 4 production readiness evaluation, and electronic inspection qualification, was u
28、sed to select the appropriate equipment and to develop the closed-loop process for manufacturing of spiral bevel gears described above. For part acceptance using digital gear master process development, computer simulation was used. The approach of actually machining various bearing pattern deviatio
29、ns was deemed too time-consuming and costly to be performed. The simulation was structured in a Design of Experiments (DOE) format. Since the computer model describing the gear tooth surface was based on actual machine settings, a wide array of those machine settings was selected as the initial inpu
30、t factors for the DOE. Computer- generated bearing patterns were selected as output factors. Highly skilled inspectors were used to evaluate these bearing patterns to rate and rank them in several groups of acceptable or unacceptable conditions. A second set of simulations was also performed, in whi
31、ch the modified computer model for the DOE was compared to the nominal baseline- model to simulate an AGIS inspection. Using the same data for creating simulated bearing patterns and simulated topography inspections it was possible to establish a correlation between current visual inspections and pr
32、oposed AGIS inspections. The DOE was executed in several steps, summarized as follows: ?Step 1: Reverse Engineer Grand Masters To Produce Perfect Electronic Master ?Step 2: Create Modified Summaries for DOE execution ?Step 3: Perform Tooth Contact Analysis (TCA) Based On Modified Summaries ?Step 4:
33、Rate Simulated Bearing Patterns using ordinal ranking system ?Step 5: Simulation of AGIS Inspection of the Modified Summaries ?Step 6: DOE Analysis The results of the visual evaluation and the topography simulation were arranged in a matrix format for analysis, along with other crucial DOE informati
34、on, such as the corresponding input factors and part numbers. A typical output is shown on Figure 4. Figure 4. DOE Outputs Used In Analysis. In order to maintain consistency with current inspection methods, it was decided to use existing Honeywell Engines 60% for gear generator and 80% for bevel gea
35、r grinders ? 80% reduction in inspection time ? Elimination of visual inspection and Working Masters ? Elimination of hard tooling cost and maintenance Additionally, the fundamental difference between the previous inspection processes and the new closed loop inspection is the requirement that all of
36、 the gear teeth are cut prior to inspection. The new process requires only one tooth to be formed for in-process set-up inspection. For final inspection, a finished part will be inspected on three evenly spaced teeth. Scrap costs are reduced for two reasons: ? The requirement that all teeth be cut p
37、rior to any checks leaves minimal room for adjustment. Any significant change in cutter path will cause the gear under test to fail, as there is minimal stock available for recutting or reforming. ?A first article setup test gear can be used in the new process. Since only one gear tooth is cut, thes
38、e gears can be used for numerous setups before being scrapped. Also, if only one tooth is cut, there is ample material to permit larger cutter path changes. Conclusions: This project successfully identified equipment and developed a process that would allow for the closed-loop manufacturing and in-p
39、rocess inspection of spiral bevel gears for aerospace gear applications. Additionally, the process of using digital master for gear acceptance was established. Based on this study, the following conclusions were reached: ?By having the capability to generate bevel gear data model and automatically c
40、onvert it into machine instructions after gear loads and contact pattern are successfully simulated, precise gear- machining set-up is now possible. ?Because of the precise gear-machining set-up, the closed-loop gear manufacturing process is capable of making production hardware equivalent to Master
41、 Gear quality. ?Only one tooth is needed to generate machine instructions to match the theoretical gear data as opposed to a full gear required in the existing gear manufacturing process. ?Using theoretical data as a baseline, the coordinate measuring machine (CMM) can be used to determine the devia
42、tions between the theoretical geometry and the actual gear resulted from the gear machine settings. By using this approach, the in process inspection is based on computer-controlled measurements instead of human interpretation by the red lead pattern inspection system. ?Closed-loop manufacturing of
43、spiral bevel gear is feasible with significant saving in cost while providing a more precise gear. ?It was shown that the simulated bevel gear-bearings match actual production parts. ?Based on this study, bevel Master Gears should be mapped using a minimum of 15 x 15-grid resolution. The inspection
44、area should cover the entire active flank of the gear tooth. The inspection area was established by reducing the theoretically possible flank in two ways: oLengthwise reduction of face width by the maximum allowable amount for profile edge breaks. oTooth height reduction by the maximum allowable edg
45、e break for the tooth top land and maximum producible and/or allowable root fillet radius. ?The results for the Grand Master inspection against the respective 13 Electronic Master should produce a Sum of Squared below 25 tenths for a 15 x 15 grid. This ensures only about 10 percent of the total avai
46、lable manufacturing tolerance would be used by the inspection system. ?The ratio between limit values for Pressure Angle Deviation (d) and Spiral Angle (d) Deviation was consistent throughout at: d / d = 4 / 1. ?By using digital gear master in lieu of physical gear master for parts acceptance, the s
47、upporting infrastructure of physical gear masters, calibration tracking system and the universal gear tester could be eliminated. Recommendations: It is recommended that the newly developed close-loop system be implemented for spiral bevel gear manufacturing to eliminate the manual, iterative, trial
48、 and error approach now used. Companies that are not in a position to upgrade their current grinder or generator will still benefit from the qualitative inspection and design improvements by implementing the open loop process described in the Experimental Results Section. The tolerancing limits esta
49、blished based on this study should be a good starting point for digital gear inspection. However for parties that are interested in establishing their own limits, the DOE and computer simulation approach could be used as a template to conduct the study. Companies interested in the designing and manufacturing of spiral bevel gears should review the information contained in this report to determine what portion of the closed-loop manufacturing technology that could
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