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Due to their weight and size, it is recommendable to conduct the geometrical measurements of large gears within the manufacturing machine itself. Such measurements are done today with the aid of portable gear measuring apparatus. Another alternative for checking gears is to equip the gear-machine with suitable probe and measuring systems so that it will be possible to measure directly on the production machine. This presentation deals with the functional extensions of the gear machine from a pure cutting machine to one capable of conducting gear measurements as well.

A popular die steel, BS224 No5, has been heat treated to put it in the superplastic state and then hobbed at 700°C and at an indentation speed of 2.5 mm per minute to manufacture an ‘0’ ring die.

Ratchet wheels, used in miniature electromechanical mechanisms, such as switches, actuators, and timers, have traditionally been produced by milling individual teeth or by blanking then shaving them in dies. Decreasing part size and tolerances in conjunction with the need for nearly sharp corners and fillet radii necessitated an analysis of alternative production methods. A study of hobbing as a production technique indicated that for many configurations it is a more economical approach than traditional methods. A technique for determining ratchet shapes applicable to hobbing has also been defined.

The simplest method by which a gear can be cut is to use a tool shaped exactly like the tooth space of the gear. This method of cutting gears is known as form cutting. In practice, the cutting tool is generally a milling cutter, such as the one shown in Figure 5.1. The gear blank is held stationary while the cutter is fed slowly in the direction of the gear axis, until one tooth space is cut. Then the gear blank is indexed through exactly one angular pitch, and a second tooth space is cut. The process is repeated for each tooth space, until the entire gear is completed.

We showed in Chapter 14 that two helical gears mounted on parallel axes can mesh correctly together, provided their normal base pitches and transverse base pitches are equal. We can therefore use a helical pinion cutter to cut helical gears, and the normal base pitch and the transverse base pitch of the gear will then be equal to those of the cutter.

A new method for computing the torsional static and dynamic characteristics of complex rotational transmission mechanism is applied to analyze torsional vibrations in the rotational transmission mechanism of a mid-size gear hobbing machine ( maximum workpiece diameter: 1.5 m ) on which violent self-excited chattering occurred, and of a large size gear hobbing machine (7.0 m) on which chattering did not occur but for which vibration analysis was performed experimentally by means of a spectrum analyzer. Consideration of experimental results along with the results of computational analysis not only isolates the cause of the violent self-excited chattering but also suggests specific design improvements based on the distributions of potential, kinetic and damping energies, and the mode shape calculated for the natural frequency causing the trouble. The effect of such design improvements can be proven by computation or by testing performed on actual machines. Experimental and calculated results form the basis for proposing optimum gear cutting conditions for large size gear hobbing machines.

The technique most commonly used to produce cylindrical gears, both external and internal, is gear shaping with a pinion-type cutter which generates gear flanks with rotating motion and removes chips by reciprocating action. Though the gear shaping cutter of a specific module can be used to cut gears with a wide range of teeth of the same module, in practice the inherent errors limit the number of teeth that can be cut on the gear. This paper analyses such inherent errors for both external and internal gears, taking into account the effect of a tip-relief angle and considering both “corrected” and “uncorrected” gear forms.

"Planning A Transmission Gear Laser Weld System"Patrick DoolanAdvanced Manufacturing Engineering, Whirlpool CorporationResearch & Engineering Center, Monte Road, Benton Harbor, MI 49022AbstractThis paper describes the planning which was involved to successfully install the firsthigh power laser system at this particular operating division. The production system laserwelds automatic washing machine transmission gears. Included is a description of planningthrough product redesign, process design and development, installation, manufacturing andmaintenance. Whirlpool's Total Quality Assurance program was instrumental in ensuringproper planning and communication took place well in advance of the equipment arriving atthe plant.IntroductionThe gear used to drive an automatic washing machine basket in the spin mode wasoriginally designed to be made from solid bar stock on a six spindle screw machine.Several difficult secondary operations including I.D. boring and plunge grinding wererequired. The part design caused more than half the bar stock material to go out the plantdoor as chips. Because of the high part cost due to long cycle times, material loss, highcapital costs and large amounts of floor space required a part redesign was considered.Part redesignIf the part were to be made from two pieces instead of one, the following cost savingscould be realized:- Cutting the barrel in a screw machine from tubing instead of solid bar eliminates mostof the material wastage.- Precision drawn tubing eliminates the finish I.D. boring operation.- The separate barrel permits through feed grinding instead of plunge grinding.- Because of the high cost of thick wall tubing, the gear blank will be made from solidbar stock, but cutting the gear teeth before assembly allows simultaneous hobbing ofmultiple parts.- The resulting screw machine operations were simpler so only 2/3 as many machines wereneeded.- Laser welding was chosen to join the assembly because the low, controllable heat inputwould not damage the ground barrel nor the hobbed gear teeth.Design change originated jointly between product and process engineering. The basis forplanning the design change implementation was outlined in Whirlpool's Total QualityAssurance program. This included design reviews at the concept, intermediate and designrelease levels of both product and process. Also included were process and product FailureMode and Effect Analysis (FMEA) at the intermediate design level. The design reviewmeetings include representatives from product and process engineering, manufacturing, plantmaintenance, industrial engineering, quality engineering, quality control and materialcontrol. The FMEA method analyzes all aspects of the product or process which can fail.Recommendations are made for modification of the product or process where feasible.Controls are implemented where problems cannot be designed out.

This study has been undertaken for the purpose of providing a computer program system for computing the torsional rigidity of complex rotational transmission mechanism, in which the total rotational transmission mechanism is represented by a mathematical model. The program system is based on the principle of the synthesis of dynamic rigidity and computes the torsional static and dynamic characteristics of the mathematical model, mode shapes, and distributions of the potential, kinetic and damping energies in the entire system for each natural frequency identified. The computed results are used to guide the designer in proposing design improvement toward the optimum design. The effectiveness of the program system is demonstrated by simulating a specific rotational transmission mechanism of a small size gear hobbing machine ( maximum workpiece diameter: 360 mm ) widely used in gear production shops. The computed and measured results of the compliance frequency response of the hob-worktable relative torsional angle are compared showing a fair correlation.

Production Engineering Measures were applied to the 70 Gc magnetron developed on a previous R and D contract. The four major changes in the tube and process design were (1) a change from a glass output window to a ceramic output window, (2) an improved integral cathode centering device, (3) additional finish treatment of assembly to prevent corrosion in storage and (4) increased vacuum and other cleaning processing of internal parts to improve life. Studies were made on frequency tunability, and integral ion pump appendage modifications. These were not incorporated. A specification in the MIL Format was proposed and approved and the tube was registered under the number 8558. A hobbed anode manufacturing facility and capability was established at Bomac as a second source to other such facilities. Bomac's facility is established to perform hot hobbing and is at present being used to make anodes from 16 to 70 Gc. Preproduction Approval Testing was performed on five tubes with no failures and the procedures and data are included.

Experimental investigations of the thermal deformations under no load conditions can, in certain machines, give results considerably different than those which occur during machining. This report deals with the measurement of the influence of thermal deformation on workpiece accuracy in the case of gear grinding. For measurement of thermal deformation it is, in certain cases, advantageous to simulate the cutting process by applying hydraulic braking to the spindle. As an example, measurements performed on a hobbing machine are described herein.

Although grinding inherently produces a better involute form and finer surface finish than other basic gear-fabrication methods, equipment, and experience in grinding 120-pitch gears with 0.100inch pitch diameter were not available when Bendix Kansas City placed a process development contract with the Fellows Company. Bendix had been producing a functional miniature gear by hobbing, but the required surface finish was borderline and burrs on the part were difficult to remove. As a result of this project, a repeatable process was developed for grinding the tooth form and maintaining a l6AA surface finish with minimum burrs. An experimental machine was used in this process development; production equipment is not yet available in U. S. industry for this process but could be developed. (auth)

A description is given of the design and development of an extremely stiff auxiliary feed system for a hobbing machine. In recent years there has been a growing demand for hob-finished gears having a crowned or barrelled profile. The amount of crowning required can vary from 4 μ/cm of face width for fine crowned gears to 4 mm/cm for barrelled gears. The requirement for fine crowned gears could not be met with the existing radial feed system but, as it was intended to apply this crowning facility to existing designs for fitting to machines already in service, a major re-design of the feed system could not be entertained. A system has been designed using an electronic sensing head and electronic servo drive to give a stroke only slightly in excess of that needed for a 12 mm barrel profile, and this has been successfully applied to 24 and 36 in. universal hobbing machines. Barrel and crowned gears have been cut successfully and significant savings in production times have been accomplished.

In this paper, a duplex spread blade method for cutting hypoid gears with modified tooth surface is proposed. The duplex spread blade method provides a rapid and economical manufacturing method because both the ring gear and pinion are cut by a spread blade method. In the proposed method, the nongenerated ring gear is manufactured with cutting edge that is altered from the usual straight line to a circular arc with a large radius of curvature and the circular arc cutting edge produces a modified tooth surface. The pinion is generated by a cutter with straight cutting edges as usual. The main procedure of this method is the determination of the cutter specifications and machine settings. The proposed method was validated by gear manufacture.

Summarization: Bevel gears are employed in the transmission of motion and torque via non-parallel shafts. When higher strength and lower noise is the objective, spiral bevel gears are used because of their higher tooth contact ratio. Face milling and face hobbing are among the most significant operations for the machining of hypoid and spiral bevel gears due to their high productivity. Although the optimization of these processes is crucial for the production of high-quality gears and the minimization of the total manufacturing cost, there are not many studies reported in this research area, owing to the high complexity of process kinematics. Furthermore, several kinematic variations of the two methods are applied in industry and their results depend highly on the cutting tool geometry. A novel simulation model integrated into a commercial CAD platform has been developed. The model achieves the 3D kinematic simulation of both face milling and face hobbing processes, generating the undeformed solid chip geometry as well as the simulated tooth solid geometry of a spiral bevel gear pinion and a spiral bevel gear wheel as an output. The simulation approach has two main purposes. First, is the optimization of the process through the investigation of the effect of cutting parameters on the quality of the obtained solid tooth flank geometry and second, is the calculation of cutting forces with the use of the obtained solid chip geometries. Aiming towards the validation of the model, the resulted tooth flank geometry is compared with the theoretical tooth exported from a well-established commercial gear calculation and design software and it is verified by means of a novel validation algorithm, also developed as part of this study. This paper focuses on the presentation of the kinematic simulation methodology and the simulation results for the face milling process. An insight into the validation model is provided and validation results are also presented. Finally, a sample investigation of the effect of generating feed rate on the produced gear geometry is conducted with the use of both algorithms. Presented on: CIRP Journal of Manufacturing Science and Technology

The majority of gear tribological studies are made on spur gears. However, helical gears are generally used in industry, and their contact behavior deserves more attention to establish a realistic base for detailed friction, wear and life studies. This study focuses on the modeling of helical gear contact with tooth deflection. A calculation model for helical gear contact analysis is introduced. Helical gear surface profiles are constructed from gear tool geometry by simulating the hobbing process. The model uses three-dimensional finite elements for the calculation of tooth deflection including tooth bending, shearing and tooth foundation flexibility. The model combines contact analysis with structural analysis to avoid large meshes. Tooth foundation flexibility was found to have an essential role in contact load sharing between the meshing teeth, whereas contact flexibility plays only a minor role. The capability of different local contact calculation methods was also studied.

Summarization: Gear hobbing is a common method of manufacturing high precision involute gears. The thorough knowledge of the developed cutting forces and the wear of the cutting tool are of great importance in order to produce helical and spur gears as they influence the cost of the manufacturing process and the quality of the produced gear. A novel simulation code called HOB3D was created in accordance with the above. This code can simulate the complex movements involved in gear hobbing with the best available accuracy, which is achieved by embedding the developed algorithm in a commercial computer aided design (CAD) environment. The simulation code calculates and exports the total cutting forces as well as the cutting forces in every cutting edge involved in the cutting process. Presented on: Journal of Manufacturing Science and Engineering

1. The use of steels R9K10, R9M4K8, and R3M3F4K5 made it possible to increase the life of sectional hobbing cutters. 2. During the heat treatment of the new complexly alloyed high-speed W-Mo-V-Co steels it is indispensable systematically to check the operation of the salt baths in which the steel is heated before hardening, and thoroughly to check the quality of the heat treatment of the tool. 3. If in the molten salts a magnesium fluoride rectifier with an addition of 0.2% black amorphous boron is used, the decarburizing activity of the baths can be greatly reduced and the quality of the tools improved. 4. The good results obtained in tests of tools made of experimental melts of steel R3M3F4K5 indicate that it is an advantage to make tools from this steel.

In order to easily determine the power required for cutting and cutting force from the cut amount in hobbing, the technique using the space between teeth of gears as the criterion was proposed. In this study, simple equations for calculating the area of the space between teeth and the cut amount were derived. The results may be summarised as follows. (1) The simple equations for calculating the cut amount in Hobbing were derived. (2) The term of the number of teeth was eliminated from the simple equation for cut amount in hobbing, therefore, theoretically, the number of teeth is irrelevant. (3) However, the effect of the number of teeth appears in the area of the space between teeth of gears.

An instrument has been designed using radial diffraction gratings to measure the transmission errors in gear hobbing machine table drives. Potential errors of measurement, due to eccentricity of the grating unit with respect to the table axis, and axis wander effects are avoided by the use of the linkage described.

A gear cutting machine is provided with gearing providing additional inaccuracies to superimpose the additional inaccuracies over the normal or residual gear cutting inaccuracies of the machine. The resultant errors cut into the gears provide gears having desired noise characteristics. The additional inaccuracies are of a higher frequency than the residual errors so that noise above the audible frequency range is provided by the gears so cut. The gear cutting machine has gearing for driving the hobbing spindle and for indexing a rotary table through worm gearing. The spindle drive gear and the worm drive gear are provided with eccentric sockets for introducing the additional inaccuracies. The drive gears also are provided with deformable portions providing the drive gear teeth so that the drive gears may be deformed into polygons. The eccentric sockets and polygonal drive gears are retained in position on the shafts that they drive by a nut and intermediary element.