Gear Quality Research Articles

Numerical simulation and optimisation of worm gear cutting

Manufacturing worm gears requires numerous adjustments and contact patterns are often used to validate worm–gear coupling quality. Here, a numerical tool has been developed to simulate worm and gear cutting and compute the kinematics error and unloaded contact pattern. The numerical tool is then used to study the influence of a set of cutting parameters and formulate a procedure for optimising manufacturing before any operation in the workshop.

Dressing of Vitreous Bonded Wheels for Continuous Generating Grinding of Gears

Grinding is a final step in the production chain of gears and therefore determines the quality of the product. In the industrial practice gears are cut - generally by means of a hobbing process - and their surface is hardened through a heat treatment, which has the target of increasing the wear resistance of the tooth flanks. Grinding is therefore necessary to remove the material distortions originating during the heat treatment and to fulfill dimensional and quality requirements. Usually only gears with high quality requirements are ground. Otherwise grinding is not carried out to reduce the production costs. In the recent years however the percentage of ground gears has been growing continuously due to the rising demands on load capacity, quiet running and life time as well as the increasing performance offered by the grinding processes. Generating grinding by means of cylindrical grinding worms shows the highest potential among the existing processes for gear grinding due to the high material removal performance that can be achieved. In order to use dressable worms efficiently the dressing technology has to be optimized. The present contribution describes the technology for dressing vitreous bonded grinding worms. This process is based on the use of form dressing rollers by means of which the grinding worm geometry and topography are generated. The investigations are aimed at analyzing the influence of the dressing parameters, in particular the speed ratio between dressing and grinding tool, and the attainable gear quality and surface properties. The results show significant dependencies between the dressing strategy and the grinding results.

Machining and Heat Treatment Effects on Distortion and Residual Stresses in an Industrial Application of ADI

The machining and heat treatment, employed in the fabrication of ADI parts, produce distortions and residual stresses that can increase the scrap rate. In the present study, dimensional changes, shape distortions and residual stresses due to machining and austempering were determined on internal gears of different chemical compositions, as-cast microstructures and machining-thermal cycle sequences. The influence of chemical composition and as-cast microstructure on dimensional change were found to be in accordance with the predictions obtained by Fuzzy modelling. Shape distortion resulted in an ovalization, whose magnitude depends upon the variation range of the residual stresses due to machining. Whereas residual stresses due to austempering were found to increase when the ovalization increases. The lack of information about the topics here studied, turn these results into a useful contribution to improve the fabrication quality of ADI internal gears. Besides, most of them can be applied to ADI parts in general.

A simulation model of gear skiving

The key components in demanding transmission chains are doubtlessly premium well designed and properly fabricated gears. The desired gear quality is performed, through three manufacturing stages, i.e. the rough cutting, the heat treatment and the finishing process. One of the most adopted methods in gear finishing is a variation of hobbing, the so-called gear skiving or hard hobbing. As every cutting process based on the rolling principle, gear skiving is an exceptional multiparametric and complicated method, which can and must be fully optimized. This paper illustrates an involved algorithm that simulates rigorously the skiving process and yields data, such as the dimensions of the non-deformed chips and consequently the cutting force components. This algorithm is supported by a computer code that offers the aforementioned parameters, with the aid of a user-friendly graphical interface, built modular and object oriented. Bearing in mind that gear skiving is a finishing gear cutting process, the developed software initially performs the simulation of the gear cutting, in order to determine the cutting boundary conditions. The aim of this research work is to interpret quantitatively cutting phenomena related to the course of the cutting force components and is extendable to predict the wear progress of complex and expensive cutting tools. In this way, the optimization of the cutting process is enabled.

Mechanical Design of Machine Elements and Machines: A Failure Prevention Perspective

Mechanical Design of Machine Elements and Machines: A Failure Prevention Perspective

Economics of science in fishery sector—the European case

Fisheries research organisations are described as large entities. In the European Union, Iceland, Israel and Norway, one or two main fisheries research institutes have been identified. In this detailed examination, research programmes in fisheries is presented in various technological fields. Theoretical knowledge of Evolutionary economics is used to understand the functioning of fisheries research in these 17 countries. Concepts of technological trajectories, path-dependancy, technological lock-in are valuable. Six main technological trajectories synthetize the foundations of research in fisheries amongst European Union, Iceland, Israel and Norway. It deals with fishery biology, fishing gear technology, aquaculture, ecology, quality (of habitat anf fish), and socioeconomics. For example, most of research institutes are concerned with the trajectory of fishery biology. In others cases, specificities exist in a few countries as socioeconomics.

A systems modelling and simulation approach to gear shift effort analysis

Synchronized gear shift quality is a major contributor to vehicle refinement. A number of papers have recently presented analytical methods for studying shift quality. However, in these papers consideration is given to the transmission in isolation from the dynamics of the powertrain and the external environment. In order to obtain a more holistic understanding of the phenomena, the use of a systems modelling and simulation strategy is adopted. A mathematical model of a conventional transmission is formulated. The model is employed in conjunction with the shift quality measures to provide numerical information relating to how the gear shift performance of a vehicle is affected by external factors acting on the transmission and also to variations of pertinent transmission parameters. Particular consideration is given to operation of the vehicle in an off-road environment and variations in input pinion inertia.

Analysis of tooth contact and load distribution of helical gears with crossed axes

This paper presents an approach for the analysis of tooth contact and load distribution of helical gears with crossed axis. The approach is based on a tooth contact model that accommodates the influence of tooth profile modifications, gear manufacturing errors and tooth surface deformation on gear mesh quality. In the approach the tooth contact load is assumed to be distributed along the tooth surface line that coincides with the relative principal direction of the contacting tooth surfaces. As compared with existing tooth contact (TCA) analysis model that assumes rigidity for the contacting surfaces, the model in this paper provides a more realistic analysis on gear transmission errors, contact patterns and the distribution of contact load. As a numerical example, the contact of a pair of helical gears with a small crossing angle is analyzed by the computer program that implements the approach. It is found from the analysis that helical gears with small crossing angles have meshing characteristics and load distribution similar to those of parallel-axis gears. The approach may be extended to other types of gearing.

Bending fatigue and contact fatigue characteristics of carburized gears

In order to assure reliability, the manufacture of gears for power transmission in high load bearing applications requires precise control of a wide range of processing parameters during manufacture, aimed at achieving specific material properties. Process selection and control in forming and heat treatment operations plays a crucial role in gear production, and must start at the design stage. Material selection, choice of forming processes, thermochemical and heat treatment operations, surface finish and condition will ultimately determine the integrity and performance limits of the gears. An ongoing research programme by Birrana Engineering, Adelaide, and the University of South Australia involves the evaluation of materials, process route and process control used in the manufacture of a range of gears and relates these factors to fatigue resistance, with the aim to reduce production costs and improve gear quality and reliability. The results of single tooth bending fatigue, and contact fatigue tests on production gears manufactured from EN39B steel (steel A), and experimental steels B, C and D (heat treatment details restricted for commercial reasons) are presented and discussed.

Task-Specific Gauge for the Inspection of Coordinate Measuring Machines

Coordinate measuring machines (CMMs) frequently are used for measuring tasks at bevel gears even though probing at inclined tooth profiles causes enormous length measuring uncertainties. In order to analyse these faults on principle a master bevel gear can be used, which however is very difficult to manufacture and to calibrate in a sufficient accuracy. Therefore a task specific gauge consisting of basic geometric elements has been developed, which can be calibrated with smallest uncertainties. After the tested CMM has probed a grid of defined measuring points, the maximum quality of bevel gears to be measured can be assessed.

Intelligent Control of the Gear-Shaving Process

The objective of this paper is to describe how AI (artificial intelligence) and fuzzy logic techniques can be combined to implement an on-line computer control of an axial gear-shaving process in order to improve the quality of workpiece gears. The basic principle of correcting the geometric errors of workpiece gears is introduced. The final knowledge base is obtained by the iterative procedure of trying the expert controller, observing the results and then modifying the control rules accordingly. Inference is provided by a fuzzy logic engine. Experimental results showed that accuracy of the shaved gears was greatly enhanced. The total cumulative pitch error arid the individual pitch error were reduced by approximately two times. In particular, the flank grooves, which commonly occur in the middle of tooth profiles, were removed.

Hot Finish Rolling of Injection-Molded Plastic Helical Gears. Properties of Finished Tooth Form.

Hot finish rolling has been developed as a simple finishing method for injection-molded plastic gears. In the present paper, properties of the hot-finish-rolled tooth form are discussed so as to obtain general information for improving the quality of the injection-molded plastic helical gears. The plastic helical gear generally has a positive pressure angle error on the tooth profile and a helix angle error on the tooth trace. After the hot finish rolling process, the finished gear has a negative pressure angle error on the driven tooth flank and a positive pressure angle error on the followed tooth flank. Sliding of tooth flanks along the profile contributes to inducing these errors. Hence, hot finish rolling including the process of reversing the rotation of gears is very useful for improving the quality of the tooth profiles of plastic gears. However, the hot finish rolling process exhibits no sliding along the face width, and thus it cannot improve the quality of a tooth trace which has a helix angle error. It can be expected that sliding along the face width will be useful for improving this error. For example, the axial feed of the work gear might induce such sliding.

Kinematical Optimization of Spiral Bevel Gears

Kinematical optimization and sensitivity analysis of circular-cut spiral bevel gears are investigated in this paper. Based on the Gleason spiral bevel gear generator and EPG test machine, a mathematical model is proposed to simulate the tooth contact conditions of the spiral bevel gear set. All the machine settings and assembly data are simulated by simplified parameters. The tooth contact patterns and kinematic errors are obtained by the proposed mathematical model and the tooth contact analysis techniques. Loaded tooth contact patterns are obtained by the differential geometry and the Hertz contact formulas. Tooth surface sensitivity due to the variation of machine settings is studied. The corrective machine settings can be calculated by the sensitive matrix and the linear regression method. An optimization algorithm is also developed to minimize the kinematic errors and the discontinuity of tooth meshing. According to the proposed studies, an improved procedure for development of spiral bevel gears is suggested. The results of this paper can be applied to determine the sensitivity and precision requirements in manufacturing, and improve the running quality of the spiral bevel gears. Two examples are presented to demonstrate the applications of the optimization model.

Minimum achievable quality of involute gears in generation processes

In gear generation processes, the involute profile of the gear is obtained as an envelope of the successive cuts made by the flank of the generating tool. The irregularities of the profile thus generated limit the quality of the gear. This paper reports the minimum achievable quality based on the maximum theoretical height of the irregularity for the involute spur gears.

Acceptance Condition for Toothform- and Toothtrace Accuracy of Cylindrical Involute Gears and its Effect On Power Transmitting Characteristics : 1st Report, Acceptance of Gears with Bad Tooth Flank Form

To express the quality of the form of a gear tooth flank, the error surface defined as the difference between an ideal involute helicoid and an actual tooth flank of cylindricai involute gears expressed on the plane of action, is useful. Here, a method to illustrate the error surface for the form of a gear tooth flank from some tooth form- and tooth trace checking curves measured along some definite positions on a tooth flank is introduced. This method vas used in a simulation of power transmitting characteristics of cylindrical involute gears, and the problem of gear acceptance was discussed. It was found to be a problem to receive gears whose quality was actually out of tolerance and showed poor performances. The results of the state of tooth flank loading in the simulation suggested that this mistake occured due to the insufficiency of the test method of gear quality at acceptance.

On Tooth Form Accuracy of Roll-Finished Involute Helical Gears

In order to improve the quality of roll-finished involute helical gears, a calculation program for roll-finished tooth form has been developed, which can deal with tooth form correction of die-wheel and tooth form error of work-gear before roll-finishing. In this calculation, gradual changing of tooth form of work-gear with progress of plastic deformation is taken in consideration. Some comparisons between calculated and measured tooth forms of helical and spur gears roll-finished by die-wheels with and without die-profile correction under some roll-finishing conditions showed fairly good coincidence. This program can therefore help to decide the optimum tooth form of die-wheel and the optimum working condition.

Quality and performance of discharge lamp control gear

The criteria by which control gear is judged are discussed. The reasons why there are differences between units, and the methods of measuring these differences, are described. It is shown how this quality assurance effort is directed towards factory production control.

SOUND GEAR QUALITY W. A. Bradley Mech. Engr. 94 (10), 31-36 (Oct. 1972) Refer to Abstract No. 72-1999

SOUND GEAR QUALITY W. A. Bradley Mech. Engr. 94 (10), 31-36 (Oct. 1972) Refer to Abstract No. 72-1999

円弧歯筋歯車の転造法について

This report deals with the method of cold rolling of the circular-arc gears with the preliminarymethod of the tooth-profile-checking. The generating machine of the gears with circular-arc tooth curve has more complicated mechanism than hobbing machine, and it is not easy to understand their tooth properties.The analytical consideration is done for obtaining the method of tooth-profile-checking of the gears and following results are obtained:(1) Under the condition of actual design, the profile inspection of the gear teeth can be done by an involute checking machine.(2) To simplify the production process the generating motion is omitted while the teeth are being cut by face-mill type cutters. After that the rough shaped blank is finished by rolling with three gear-shaped dies.(3) The experimental results are as follows: Accuracy of the rolling gears is influenced mainly by blank accuracy. If the single pitch error is kept within JIS gear quality class 4 to 5, its class after rolling becomes within the class 2 to 3. The other kinds of accuracy such as runout, total composite error show the similar tendency to the single pitch error.

SOME NOTES ON THE APPLICATION OF ELASTO‐HYDRODYNAMIC THEORY TO GEAR LUBRICATION

The effectiveness of the oil film between the gear teeth will, of course, depend on the magnitude of the asperities. In this respect distinction must be made between the initial state of the gears and that after running‐in. Individual measurements of surface roughness show considerable variation between nominally similar gears, but there is a fairly well defined relationship between typical values and gear quality, as indicated below. Roughness is here expressed in micro‐inches CLA (centre line average), i.e., arithmetical average of the departure of the profile both above and below a centre line of appropriate curvature.