Abstract: In present paper, a semi-empirical grinding force model is developed combined with the achievements of previous researchers by composing effects of normal and tangential grinding forces in two main parts respectively: cutting force and sliding force. Final equations for the total normal and tangential force components is established. This model is used to predict the total normal and tangential force in the surface grinding. These force components were expressed in terms of the grinding process parameters. There are four unknown coefficients in each equation which can be determined by experiment results at specific conditions with the variations of grinding process parameters. An equation for sliding force is established with the effect of specific sliding energy in terms of the experimental parameters. The average contact pressure and friction coefficient are taken into account. Four different water-based grinding fluids were tested for different specific grinding conditions. Low viscosity grinding fluid can have better performance than the high viscosity one due to the higher useful flow in the grinding contact area. The calculated normal and tangential grinding results are compared with the experimental ones. The verifications show that deviations can be affected by the performance of the fluid at heavy grinding conditions due to the sliding friction inside of rolling friction. To have a better agreement with experiment data. Shallow grinding condition is chosen to obtain the modified model.
Abstract: Modelling of the lapping process proves a complex undertaking because of the different forms of the abrasive particles in the working area, the wide dispersion of their dimensions, the modifications of their shape and dimensions during processing. The paper proposes the spherical model of the abrasive grain, based on the known fact that a good quality of the processed surfaces requires compact grains, with a dimensional ratio as close as possible to 1:1:1. Based on the adopted model the distribution of tensions at the grain-workpiece contact is determined, as well as the penetration depths of the abrasive grains into the workpiece and the transfer object, respectively. For this certain initial conditions are necessary, like Hertzian contact between the abrasive grain and the processed surface and the neglecting of strain hardening. Taking into consideration the known fact that only the large abrasive grains participate in the actual cutting process while the rest remain suspended in the gap between workpiece and tool, as well as their dimensional distribution and concentration in the lapping slurry, the volume of abrasive material required for processing was determined by statistical methods.
Abstract: One of the problems of metal alloys machining in view of the environment protection is the use of cooling lubricants. From this viewpoint, it is preferred to limit the use or completely eliminate them from the cutting process. The solution may be the method of Minimum Quantity Cooling Lubrication (MQCL). The results of the machined surface roughness measurements of carbon steel C45 after turning when: machining for dry cutting, using cooling method MQCL and using MQCL with additives EP/AW have been presented. One used two anti-wear and antiseizure additives based on phosphate ester. Experimental studies have been planned according to the Parameter Space Investigation method. The application of EP/AW additives entered in the emulsion determined the ranges of cutting parameters at which lower values of selected roughness parameters were obtained in comparison with dry cutting. The lowest values of Ra and Rz parameter for variables of cutting parameters and creating emulsion mist within their whole range were obtained for cooling with pure emulsion mist based on boric acid and amine compound.
Abstract: Ultraviolet-cured resin bond, abrasive tools have been studied and have proven to have substantial advantages over conventional abrasive tools, not only in low energy cost and high efficiency when manufacturing the tool itself, but also in better performance when machining some materials [1,2]. However, very little research has been done to study the mechanism of UV cured abrasive tools. Nevertheless, many researchers have investigated the performances of such tools compared with some conventional tools. A mechanism of UV cured, resin bond, diamond wheel was proposed as the hybrid of grinding and lapping, which is called as grind/lap (G/L) process . In the paper, the proposed mechanism was verified by comparing the experimental results of three processes. Three wheels were used to simulate grinding, lapping and grind/lapping operation separately under the same experimental setting. The results showed that the RA obtained by G/L wheel decreased to a value between those gained by grinding and lapping operations after 10 minutes and it became the lowest of the three as time increases. The RA and MRR of three processes indicated that at the beginning of operation, the abrasives in G/L wheel are fixed by the cured resin, and as machining time increases, the small grains get released from the wheel and act as loose abrasives. Therefore, the mechanism of the UV cured resin bond diamond wheel is verified as the dominant grinding at the beginning and lapping at the end, which was also illustrated by the surface profile of machined part.
Abstract: In the context of the increasingly frequent use of curved surfaces in the design of products surrounding us, ball end mills are at present the only usable tools in the cutting of complex surfaces, either concave or convex. This aspect, once correlated with the need to reduce the surface roughness, which means an increase in the cost of processing, directs our research to those on the milling with ball end mill. In this way we can identify the optimum cutting data in terms of costs to ensure the prescribed surface roughness. The paper is based on a set of experiments on the correlation of roughness with the parameters of the cutting process, for the C45 material treated with heat at 54HRC. The paper presents a part of a complex industrial research in this area and is complementary to the published works [1, 2]
Abstract: In this paper we present a technological problem encountered in the machining accuracy of the parts for aerospace made of aluminum alloy extruded profile with length up to 10 meters. Those parts have very tight tolerances and on milling process appear several factors that influence the repeatability of machining processes, the main one being the thermal expansion effect.
Abstract: In this paper, we present, comparatively, two analytical methods for profiling the tools delimited by revolution surfaces, used to generate helical surfaces with constant pitch. The first method lays on a complementary theorem used for tools profiling, namely the Minimum distance theorem. A specific algorithm for applying it has been developed, in order to profile the tools delimited by revolution surfaces, which generates helical surfaces with constant pitch by enwrapping. The methodic is referring, here, to a tool whose symmetry axis is incident and, at the same time, normal to the helical surface axis – the end mill cutter. The other analytical method here applied grounds on Nikolaev classical theorem. We also present an example of application for both methods, in the case of profiling the end mill cutter used to generate a helicoid with circular frontal generatrix. The tool axial sections are determined and compared in a numerical representation.
Abstract: The work described in this paper pertains to the identification of some features of micro- and macroprofile formation of surfaces to be machined with flat face grinding, with inclination of the spindle axis. The question of the formation of machined surface profile at through-feed grinding and multiple-pass scheme are considered by using computer-aided simulations in COMPASS environment. More specifically, for flat face through-feed grinding, a generalized empirical equation exhibiting the dependency of concavity from the outer diameter of the face grinding wheel, the spindle axis inclination angle and the width of the surface of the workpiece is acquired. Furthermore, based on the maximum allowable value of flatness deviation and with pre-determined grinding wheel diameter and workpiece width, it is possible to identify the maximum inclination angle at which concavity falls within acceptable limits. For the case of multiple pass flat face grinding, the role of factors such as inclination angle of spindle axis, cross-feed and diameter of the grinding wheel on the height of residual ridges on the surface of the parts is determined through the proposal of an empirical equation. With the aforementioned equations the machinist may reasonably prescribe machining conditions in practice. The conducted research contributes to the expansion of ideas regarding technological possibilities of improvement of flat face grinding.
Abstract: As it is well known the grain mixture entered for processing, is a mechanical mixture of different components, which can be up to 20% of different impurities. Modern cleaning machines of various modifications do not always provide high quality separation of grain mixture. Imperfection of these machines does not allow get the maximum effect of purification. In order to improve the quality and achieve a more stable and independent processes grain cleaning, it is proposed a new device for cleaning grain. The device comprises a chamber with air aspiration inclined perforated shelves and a boot device. In the study of moving grain particles doped with an inclined perforated shelf is advisable to use the general law of dynamics for the bodies of variable mass. Movement of the selected grains center of mass mixed with particles in the direction of the shelves as described in the fundamental equation of dynamics. While moving mass of particles with a mixture of grains, will be reduced by removing light impurities retracting force of the air flow. This mass is a function of time. Taking into account the reduction of total mass of grain particles, because of impurities reduction the motion equation used in the form of variable mass. There will be the same equations of motion along the other shelves, respectively, the equations are written for the first leg, but with different masses, as well as with other forces retraction.