Research On Roundness Error Consistency Model For Crank Journal Cylindrical grinding

Cylindrical grinding is an important way to form the external shape error of the crank journal, and the accuracy consistency directly affects the interchangeability of products. To study the accuracy consistency of crank journal，a dynamic model of the grinding wheel-crankshaft grinding system based on Timoshenko beam is established, and the grinding transition process simulation algorithm with iterative convergence of grinding force-transient grinding amount cycle adapted to the model is proposed, which realizes the simulation of the roundness of the crank journal coupled with the process parameters of the grinding system. Aiming at the grinding position of each crank journal, the grinding roundness of five crank journals is simulated respectively. On this basis, the crank journal roundness consistency prediction model is established, and the effectiveness of the prediction model is verified by field experiments. Finally, the influence of grinding parameters on the consistency of the roundness of crank journal is studied. The research conclusion can provide a reference for the grinding accuracy consistency design of this type of crank journal.

OPTIMUM WORKHOLDING CONDITIONS FOR PRECISION CYLINDRICAL GRINDING OPERATIONS

Grinding process is a very important process in machining industry being one of the most popular processes when high quality parts must be manufacture. Likewise, workholding is a critical issue on cylindrical grinding. The use of the driving dog is common when the workpiece is held between centers. However, one of the handicaps of this workholding is that the cylindrical workpiece cannot be ground along the complete length. In order to tackle this issue, in the present work the workpiece is held between centers avoiding the use of the driving dog. To this end, a methodology to obtain the grinding limit parameters that ensure that the transmitted torque is higher that the resistance torque is presented, being the aim of these tests is to avoid the sliding between the point and the workpiece. Finally, non-destructive tests are designed, which, using a safety coefficient of about 0.77, the tests allow the correct design of each specific grinding process. Keywords: cylindrical grinding, workholding, driving dog, sliding

SURFACE ROUGHNESS ANALYSIS OF CRYO-TREATED AND TEMPERED STEELS IN CYLINDRICAL GRINDING OPERATION

Cylindrical grinding operation is an important metal cutting process used as a finish process to achieve the surface quality and dimensional stability of the products. In this context, experimental work and statistical analysis in researches contribute to improve product quality of manufactured parts. Tempered steels are widely used for automotive components and manufacturing applications. The objective of this study is to analyze the surface roughness (Ra) values of cryogenically (cryo) treated and tempered steels in cylindrical grinding operation. According to the grinding experiments created by the Taguchi method, grinding wheels (Al2O3 and SiC), heat treated steel samples (HT, CT24, and CT36) and depth of cut (50, 100, and 150[Formula: see text][Formula: see text]m) were selected to determine the optimum surface roughness values of these steels. The results showed that significant improvements in Ra values of cryo-treated and tempered steels were observed. The lowest Ra values were obtained in cryo-treated sample (CT36) with SiC grinding wheel and depth of cut (50[Formula: see text][Formula: see text]m).

Experience of High-Density Polyethylene as a Binding Substance in Grinding Wheels

The possibility and efficiency of the use of high-density polyethylene as a binding substance in grinding wheels for cutting-off, as well as for finish cylindrical grinding, is researched. It is determined that: - breaking mechanical strength of such circles ensures their safe operation at maximum operating speeds of 30–35 m/sec; - the use of high-density polyethylene as a binding substance in cutting wheels is not advisable, due to intensive wear and low cutting power of these tools; - wheels for finish cylindrical grinding on the basis of high-density polyethylene and hollow spherocorundum as abrasive grains in a number of key indicators (cutting power, roughness of machined surfaces) are highly competitive with grinding wheels on a bakelite bond or are comparable to them, and significantly exceed the latter in terms of wear resistance.

Análise dos parâmetros de corte sobre a rugosidade ra na retificação cilíndrica externa de passagem axial / Analysis of cutting parameters on roughness Ra in external transverse cylindrical grinding

A rugosidade superficial das peças produzidas é o meio de avaliação mais utilizado em qualquer processo de usinagem, principalmente em retificação. Neste estudo, foram aplicados sobre uma peça de aço ABNT 1020 diferentes configurações de usinagem, a fim de investigar a influência do avanço, da relação de velocidade e do sentido de corte, concordante e discordante sobre um dos aspectos da integridade superficial da peça usinada. Por fim, foi verificado que a razão entre a velocidade periférica do rebolo () em relação à velocidade da peça (), teve maior influência na rugosidade superficial média (Ra) do que o avanço de corte (f).