PROCESSING OF HARDENED CYLINDRICAL GEAR WHEELS OF THE CUTTING GEARBOX OF THE COMBINE UKD 200-500

The article discusses the latest developments of unique technological methods of gear milling of cylindrical gears for preliminary blade gear processing of hardened cylindrical gears of the cutting reducer of the UKD200-500 coal mining harvester for the final gear grinding of gear teeth with modulus m = 16 mm, with hardness HRC 56 ... 62. The peculiarity of the design of special hob cutters is that a circle passing through the lower boundary points of the involute is used as the palloid of the machine gearing of the tool and part. Pre-cutting the teeth of hardened wheels with carbide milling cutters allows you to remove the main allowance for the final gear grinding.

IMPROVING GRINDING OF GEAR WHEELS APPLIED IN GEARBOXES OF POWER ENGINEERING

Development of modem power engineering follows the line of continuous increase in speed, coefficient of corrosive action and capacity of units. Gears and reducers are responsible parts of modem machinery and occupy an important place in the domestic power engineering construction. Durability and wear resistance of gears, apart from the design factors, also depends on the technological methods of treatment. The final stage of production of such wheels is the operation of gear grinding. In the process of gear grinding in a thin surface ball there are complex thermomechanical processes. As a result of short-time heating to high temperatures, structural transformations, burns, and in some cases even micro- and macro-thicknesses occur in such a surface bail. In addition, there are cases of making tooth wheels with adjacent defects grinding (for example, the appearance of the surface of the ball teeth of large tensioning forces), which reduces the life of the work, and in some cases causes a breakdown of the teeth in operating conditions. Development of effective measures to ensure the quality of the surface of the ball on the operation of grinding baggage in part depends on the possibility of predicting (or calculation) of temperatures and residual loads on the depth of the cemented teeth ball. The method of calculation of internal surplus Toads occurring during grinding of wheels with cemented steels is suggested. On the basis of the performed calculations and experiments the ways to improve the quality of production of working surfaces of gears, which are used in the wits of thermal and nuclear power plants are suggested and grounded.

Optimization of the precision gear grinding operation based on integrated information system

In accordance with the principles of hierarchical management, a comprehensive two-level management system is presented for the development and manufacturing of products for the stages of pre-production (the upper level of the management hierarchy) and for the actual production stage (the lower level of the management hierarchy). At the stage of pre-production, the gear grinding operation design on the “MAAG” type machines was carried out. For this purpose, a technique for optimizing the gear grinding parameters for a two dish-wheel rolling scheme has been developed, a mathematical optimization model containing an objective function with restrictions imposed on it has been created. The objective function is the gear grinding machine time, which depends on the operation parameters (gear grinding stock allowance, cutting modes, grinding wheel specification, part material) and the design features of the gears being ground (module, diameter, number of teeth, radius of curvature of the involutes). The article shows that at the stage of pre-production, the gear grinding optimization is a method of operation design. At the stage of actual production, a closed-loop automatic control system with feedback on the deviation of the adjustable value (gear grinding power) automatically supports the numerical power values that were found at the operation design stage, taking into account ensuring defect-free high-performance gear grinding (minimum number of working strokes and maximum longitudinal feeds). At this stage, i.e. when a robust longitudinal feed automatic control system is operating, the optimization carried out at the previous stage (pre-production) sets the functioning algorithm for the adaptive system with corresponding control algorithm. Thus, at the production stage (when the gear grinding machine is running), the operation optimization is a control method. Therefore, it is shown that with two-level control, the gear grinding operation optimization performs a dual function. On the one hand, it is a design method (at the pre-production stage), and on the other – a management method (at the actual production stage). With this approach, i.e. with the integration of production and its preparation based on a single two-level management, the efficiency of a single integrated design and production automation system is significantly higher due to general (unified) optimization, rather than partial one.

MODERN METHODS OF GEAR MILLING OF HARDENED LARGE-MODULE GEARS

The latest developments of modern methods of high-speed gear milling of large-module cylindrical gears, both for preliminary grinding of teeth and for final blade processing of gears, are considered. For high-speed blade gear processing, promising designs of worm carbide cutters have been developed, manufactured and implemented. The technological regulations of blade gear processing for the operation of each of the design solutions of worm carbide cutters have been developed. The design of a special double-body worm cutter for double-sided cutting has been developed. It is shown that the carbide cutting elements of the milling cutters, which are placed only along the lines of the machine engagement of the tool and the workpiece, make it more economical compared to the known designs of similar tools. The application of the developed technological methods of pre-blade processing of the teeth of hardened wheels with carbide cutters reduces the labor intensity of low-performance gear grinding operations, depending on the wheel module, by 3-4 times by reducing the allowance from 1.5–2.5 mm on the tooth side to 0.3–0.5 mm, and also allows you to ensure the gear processing process is economical by reducing the consumption of carbide plates. The developed technological studies of ensuring the quality of gear processing of large-module cylindrical wheels allow us to solve the scientific and technical problem associated with the production of large-module gears with high-hardness teeth while improving the quality of their manufacture, reducing labor costs and reducing material consumption.

Influence of the Tool Wear on the Quality and Service Life of Gears for the Geared Turbofan Technology Machined by Five-Axis Milling

The geared turbofan technology is one essential way to reduce the fuel consumption, the environmental footprint and the noise pollution of civil aircrafts. An added gearbox between the fan and the low-pressure compressor that reduces the fan speed, which allows higher bypass ratios, achieves the mentioned benefits of geared turbofans. To withstand the high mechanical loads, large double helical gears are used. Gear hobbing and gear grinding require large tool maneuvering spaces. This leads to a larger required space between the single gears of the double helical gear. As a result, the gears are larger and heavier, which leads to a reduced economy of the aircraft. The tool maneuvering space of five-axis milling with solid carbide end mills is much smaller. This enables the design of smaller, lighter and more efficient aircraft engines. However, manufacturing these gears in tolerances better than IT5 is very challenging on five-axis milling machine tools. This paper presents investigations about finish machining of hardened gears on five-axis machine tools. In the investigations performed, varying tool substrates and tool coatings have been investigated together with tool travel paths in order to reduce the tool wear, which is key to achieve the demanded tolerances. Finally, the five-axis milled gears were compared to conventionally manufactured gears on test benches to enable statements regarding the expectable service lives of the manufactured gears.

TECHNOLOGICAL CAPACITY UPDATING OF CONTINUOUS RUN-IN GEAR GRINDING METHOD

The work purpose consists in the technological capacity updating of the method for cog-wheel continuous run-in gear grinding based on the purpose of efficient modes and characteristics of the worm disk. The investigation methods are based on mathematical modeling and planning experiments. Machining aircraft cylindrical cog-wheels and special samples was carried out on modern NC machines, benches and plants with the use of up-to-date test equipment: coordinate inspection machine KIM R-100 “Klingelnberg”, profile meter MarSurf M300S “Mahr”, optical microscope Axiovert 400MAT “Zeiss”, electronic scanning microscope Tescan Mira3 “Tescan”, micro-hardness gage Micro Met 5104 “Buehler”, X-ray diffractometer Xstress Robot “Stresstech OY”, Barkhausen digital nose analyzer Rollscan 350 “StresstechOY”, plant APOON on the well-known and developed techniques. The research results and novelty. Special strategy and cutting modes at the required characteristics of the combined polish-grinding worm allow ensuring gear profile roughness Ra=0.089 mkm keeping high accuracy of a ring gear (gear profile error Fa=1.6mkm) without gear honing thereby increasing productivity. The quality researches of gear surface layer give grounds for the application of the method for aircraft cog wheels.