THE EFFECT OF TEMPERATURE ON THE GRINDING SURFACE QUALITY RING ROLLER

A series of experimental researches was carried out in the work, which confirmed the results of modeling of temperature processes in the zone of centerless intermittent grinding of billet rings. The constructed response surfaces of the dependence of the roughness parameter Ra on the grinding modes and the number of grooves of the grinding wheel form the basis of the developed technique for designing grinding operations and tool adjustments of grinding machines. The contact area of ​​the abrasive circle with the workpiece is a narrow strip of rectangular shape that moves along the workpiece surface. In this case, the temperature field can be calculated according to the scheme of a moving infinitely long surface-band source. The plan, the program and the hardware of experimental researches of the connection of design and technological factors and indicators of grinding operations with parameters of quality of grinding surfaces, temperature of grinding, power parameters of the process of grinding by discontinuous grinding circles and constructive circles have been developed.

Grinding of Chromium Carbide Coatings Using Electroplated Diamond Wheels

This paper reports an experimental study on grinding of chromium carbide coatings using electroplated diamond wheels. The work was motivated by machining carbide coatings in gas turbine engine applications. The objective is to explore the process conditions and parameters satisfying the ground surface quality requirements. Surface grinding experiments were conducted with water-based grinding fluid on chromium carbide coated on flat surfaces of aluminum blocks for rough grinding at a fixed wheel speed vs = 30 m/s, and finish grinding at vs = 30, 60 m/s. The effects of depth of cut and workspeed on grinding power, forces, and surface roughness were investigated for each of the wheel speeds. Material removal rate Q = 20 mm3/s for rough grinding at a grinding width b = 101.6 mm was achieved. It was found that the maximum material removal rate achievable in rough grinding was restricted by chatters, which was mainly due to the large grinding width. The specific energy ranged from 27 to 59 J/mm3 under the tested conditions. Surface roughness Ra = 3.5–3.8 μm were obtained for rough grinding, while Ra = 0.6–1.5 μm were achieved for finish grinding. Surface roughness was not sensitive to grinding parameters under the tested conditions, but was strongly dependent on the diamond grain sizes. Imposing axial wheel oscillations to the grinding motions reduced surface roughness by about 60% under the tested condition. It was proved that it is feasible to grind the chromium carbide coating with electroplated diamond wheels.

Performance Evaluation of the Minimum Quantity of Lubricant Technique With Auxiliary Cleaning of the Grinding Wheel in Cylindrical Grinding of N2711 Steel

Grinding is an abrasive process mostly used in finishing operations to provide low roughness and narrow limits of form and dimensioning to the workpiece. Due to the large amount of heat generated by friction between the abrasive and the workpiece in this process, the use of large volumes of coolant is encouraged to avoid thermal damage, such as burning and hardness variation caused by subsurface damage. On the other hand, environmental impacts and human health problems caused by coolants have been a key issue toward sustainable manufacturing, mainly because of the chemistry behind them. Thus, is important to seek for strategies to reduce the volume of fluids and their risks as well as guarantee grinding efficiency. One machining strategy is the minimum quantity of lubricant (MQL) technique, which is well consolidated over the past 25 years and one that uses low volumes of fluid mixed with compressed air flow, as well as provides less waste. However, it has generally been reported that sludge formed during grinding is forced into the wheel pores, consequently clogging its pores, thereby reducing the wheel cutting potential and its performance. A possible solution for this problem is to use an auxiliary compressed air system to clean the grinding wheel surface during machining, since the MQL conventional system is not able to clean it. In this context, this work evaluated the performance of the MQL technique with an auxiliary cleaning of the grinding wheel cutting surface in relation to the conventional cooling techniques (flood cooling) during a cylindrical plunge grinding of N2711 steel. N2711 steel is widely employed in manufacturing of molds for plastic injection processes and is one of steels more susceptible to grinding burn. The following output parameters were used to assess the performance: surface roughness, roundness, microhardness, grinding power, and grinding wheel wear. The results showed that the MQL technique, in addition to the environmental and economic advantages achieved, provided superior workpiece quality, and lower power consumed compared to the flood technique. The MQL technique proved to be an alternative method compared to the conventional technique under the conditions investigated. Also, the Malkin’s model was used to predict the grinding ratio (G-ratio) based on the experimental data obtained in this work. After regression analysis, the model predicted the G-ratio from the specific material removal rate and the cutting speed with a satisfactory accuracy of approximately 92%.

Optimal design of rail grinding patterns based on a rail grinding target profile

Based on the grinding target profile of the rail and the grinding capacity of a single grinding stone, a numerical calculation method for rail grinding patterns that includes grinding angle and grinding power of each grinding stone of the GMC96 rail grinding train was designed and established. By means of this numerical method, the grinding pattern of each grinding pass was optimized and the rail head profile after grinding was calculated. Furthermore, a method for the evaluation of the grinding quality is provided. The results indicate that in multipass rail grinding, a sequence of grinding passes – where the greatest grinding effort is applied on the earlier passes, with the last pass applying reducing levels of grinding effort – produces the highest conformance to the target grinding profile. For example, when rail grinding is planned for two passes, applying 60% of the total grinding effort on the first pass and 40% on the second pass decreases the final grinding error by 7.3%.

Investigation on the Grinding Force, Power and Heat Flux Distributions Along the Tooth Profile in Form Grinding of Gears

This paper investigates the distributions of grinding force, power consumption and heat flux along the tooth profile in precision form grinding of gears. A semi-analytical grinding force model has been established considering the static and dynamic chip formation forces and also the sliding force. Variation of the local contact conditions between the wheel and gear flank along the gear tooth profile, including the local depth of cut, local wheel diameter, local wheel speed and also the equivalent wheel diameter has been analyzed. Combining the variation of local contact conditions with the semi-analytical grinding force model, the grinding force and power distributions along the gear tooth profile have been derived. The predicted values of grinding power under different wheel speeds, worktable speeds, radial grinding depths and different contact widths are compared with those experimentally obtained and the results show a reasonable agreement. The predicted grinding forces at different rolling angle positions under different grinding parameters show a good agreement when compared with those experimentally obtained. The heat flux distribution along the interface between the form grinding wheel and the gear flank in form gear grinding has been further calculated.

In-process monitoring and analysis of bearing outer race way grinding based on the power signal

In production engineering, monitoring of the grinding process is critical for acquiring information on material removal, wheel performance and workpiece quality. Here, a general model of the power signal and material removal rate is proposed to monitor the internal plunge grinding of a bearing outer race way product. Three continuous grinding cycles after dressing were used to analyse the roughing, semi-finishing, finishing and spark-out process under the same parameters. Based on the actual grinding process, a practical analysis method is applied to improve the general model to more accurately predict the power curve. Finally, estimations of grinding wheel performance and grind quality using the grinding power signal model coefficients are also presented. The experimental results showed that the improved power signal model is capable of solving the industrial problem of multi-stage infeed grinding cycles and improving grind quality.

Deep Profiled Slot Grinding on a Nickel-Based Alloy with Electroplated CBN Wheels

A process for grinding deep profiled slots in a nickel-based alloy with electroplated cubic boron nitride (CBN) wheels and straight oil is presented. These slots were prepared by this process for further grinding with electroplated CBN quills to generate the final fir-tree slots in gas turbine disks. Fir-tree slots are usually machined using broaching. The application of broaching, however, is limited in the case of nickel-based powder metal alloys due to short life of broaching tools and the effect on machined surface integrity. Grinding tests were first conducted on rectangular blocks to grind slots without inclinations at a fixed wheel speed vs = 60 m/s to identify the combinations of depths of cut, workspeed, and up/down grinding satisfying the requirements of ground surface quality and material removal rate. Inclined slots were then ground with the identified condition on a block representing a segment of an actual turbine disk to validate the condition. The wheel life was finally tested by grinding all the slots on the actual disk. Grinding power was measured, and the ground surfaces were inspected for any sign of burning. Preset target material removal rate and wheel life were obtained. It was found that electroplated CBN wheels are capable of grinding deep profiled slots on the difficult-to-cut nickel-based alloy.