This paper presents an analysis of the impact of modification of thermomechanical properties of polymer materials on the process of gear wheel machining on a CNC machine tool. Polymer materials Tecaflon (PVDA) and polyethylene (PE) were used for processing. The materials underwent thermal modification i.e., annealing. Prepared samples (gear wheel dimensions Ø76.5 × 20 mm) were machined under the same conditions, only changing the feed rate parameter. A CNC milling machine of its own construction was used for machining with a horizontal numerical dividing attachment. The obtained gear wheels were tested using ZEISS GEAR PRO gear analyzes software. Deviations of the involute outline and the tooth line allowed classification of wheels in the 9th grade of accuracy. Machined teeth surfaces were examined for changes in the properties of surface layer, taking into account the influence of polymer material thermal modification on the surface condition. The samples were tested for mechanical properties (tensile strength) and thermomechanical properties (DSC and DMTA). The tests showed positive changes in material strength and significant improvements in PVDA Tecaflon after heat treatment.

Measuring errors caused by deformation (flattening) of a measured object appear under the influence of pressure force and weight of the measured object. Plastic strain, arising at the contact of a measured object and an undeformable contact tip of a measuring device, can be calculated by applying the Hertz plastic solution and the hypothesis of plastic strain. In a small area of contact between two bodies pressing against one another with force F, there appears the so-called contact stress. It can sometime reach very high values, exceeding the yield point, even when the contact pressure is relatively small. In the present work, the authors describe a theoretical solution to the problem of plastic strain between two bodies. The derived relationships enable to calculate force F during measurements of a deformable object by means of an instrument with an undeformable, spherical measuring tip. By applying the τmax hypothesis, a solution was obtained for the force F in an inexplicit form. The theoretical solution was verified with the digital simulation and experimental measurement. With the FEM method, the limit length gage was modeled in interaction with the measured shaft of a diameter d larger than the nominal one of Δl value.

Machine tools are built based on cast-iron bodies. Cast iron well dumps down vibrations and is dimensionally stable. Therefore, many conventional machine tools are modernized and modified into CNC machine tools based on the seasoned old bodies of those machine tools. Nevertheless, CNC machine tools are also manufactured based on polymer concrete, which vibration damping ability is even better. On the other hand, attempts made in the past by leading machine tool manufacturers to use welded frames in CNC machine tools failed. The revival of interest in welded frames was spurred by economic considerations, as steel systems are much thinner compared to cast-iron ones. They are able to carry the same loads. The construction of CNC machine tools with a welded steel frame undertaken at the Institute of Mechanical Technologies (ITM) of the Czestochowa University of Technology is an attempt to solve this constructional problem. The machine tool frame was designed with use of CAD solid works system. The ultimate success of using the welded frame is determined not only by the frame itself, but also generally the design of the machine tool and its operation parameters. The welded frame was used for a high-accuracy three-axis milling machine. In this respect, it is equal of professional machine tools manufactured by reputed companies. It can be either a production machine tool or a test stand.

The article has presented a numerical method for determining the gear ratio function and the gearing line of the toothed gear. The described algorithm, explained on the example of planar gearing, can be used also for the analysis of spatial gearings. Assembly errors have been allowed for in the gear model.

Abstract:The article presents an analysis of the modification of the toothing of spur gears. The aim of the modification of the profile on the tooth tip is to compensate for the tooth deflection under loading and to improve the conditions of gear operation. Cases of longitudinal toothing modification of a convex-convex (Cv-Cv type) tooth are described, where the tooth is biconvex and the gear teeth are convex-concave (Cv-Cc type). The conditions of mating of modified gears have been analyzed. A method of machining gears by the step-by-step method has been proposed, which can be used in unit machining of large-module gears with an arbitrary profile modification system.

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Original scientific paper The article presents a mathematical model for the determination of the tooth surface of the wormwheel machined by either the tangential or the radial method. Wormwheel machining with a special hob and a modular hob is considered. Different methods of solving the task are presented. This includes also a numerical method that requires the envelope condition to be solved. The described discussion is general in nature. The tool action surface, built based on the worm mating with the wormwheel in the worm gear, may have an arbitrary profile. In the technological gear, made up by the tool and the wormwheel, the rotary motion of the wormwheel was exchanged for its rectilinear motion. The tool positioning errors in the machining process were taken into account. Keywords: envelope method; worm gear; wormwheel Analiza točnosti ozubljenja pužnog kolaIzvorni znanstveni članak U radu se predstavlja matematički model za određivanje površine zubi pužnog kola obrađenog bilo tangencijalnom bilo radijalnom metodom. Razmotrena je obrada pužnog kola specijalnim pužnim glodalom i modularnim pužnim glodalom. Predstavljene su različite metode rješavanja zadatka uključujući i numeričku metodu koja zahtijeva rješenje stanja ovojnice. Opisana rasprava je općenite prirode. Radna površina alata, izrađena na osnovu puža spojenog s pužnim kolom u pužni zupčanik, može biti proizvoljnog profila. U tehnološkom zupčaniku, sastavljenog od alata i pužnog kola, rotacijsko gibanje pužnog kola je zamijenjeno pravocrtnim gibanjem. U obzir su uzete greške pozicioniranja alata u postupku obrade.