Chatter Suppression in Boring Process Using Passive Damper
During machining process, chatter is an unavoidable phenomenon. Boring bars possess the cantilever shape and due to this, it is subjected to chatter. The adverse effect of chatter includes the increase in temperature which will leads to excess tool wear. To overcome these problems, in this investigation, Cartridge brass (Cu – 70% and Zn – 30%) is passively fixed on the boring bar and also clearance is provided in order to reduce the displacement, tool wear and cutting temperature. A conventional all geared lathe is attached with vibrometer and pyrometer is used to measure the displacement and temperature. The influence of input parameters such as cutting speed, depth of cut and clearance on temperature, tool wear and displacement are investigated for various cutting conditions. From the result, the optimum conditions to obtain better damping in boring process for chatter reduction is identified. Keywords—Boring, chatter, mass damping, passive damping.
OPTIMIZATION OF PARAMETERS AFFECTING SURFACE ROUGHNESS AND HOLE DIAMETER IN BORING PROCESS
Boring operation is performed on bucket Oriels of earth moving equipment. As in other machining operations, boring process is also influenced by multiple parameters like feed rate, depth of cut, type tool & coolant, speed of cutter, etc. The objective of the present work is to improve the quality of the surface finish (Ra) and the accuracy of bore diameter. The parameters considered for optimization of the boring process are speed and feed rate of the cutting tool, while the depth of cut maintained at a constant value of 1 mm. After the completion of the boring process, each individual Oriel is checked for surface roughness (Ra) and dimensional conformance. Experiments are carried out on 18 different samples (using full factorial). The response data in the form surface finish and diameter of the bore are obtained for each sample. The Analysis of Variance (ANOVA) is carried out to find the significant factors and their individual contribution on the response functions. The most optimal values for the given boring conditions of speed (1000 rpm), feed rate (100 mm/min) and depth of cut 1 mm expected to give a hole Dia 70.005 mm and surface roughness Ra 1.843 μm. The optimal values are further confirmed by carrying out nine confirmatory tests by three different operators. The results for all the three cases are closely following the optimal solution obtained by DOE process, indicating that the solution adopted is good for the given environment of boring operation.
Traceability strategy for gear-pitch-measuring instruments: development and calibration of a multiball artifact
There is a strong demand to ensure the traceability of gear-measuring instruments (GMIs). We propose a multiball artifact (MBA) for the evaluation of pitch-measuring accuracy. The aim of the MBA is to transfer the minimum uncertainty from a calibrated value at the National Metrology Institute of Japan (NMIJ) to a measured value of GMIs at a shop floor. The MBA is composed of equally spaced high-accuracy balls around an axis. The pitch-measuring accuracy of GMIs is evaluated by measuring the angular pitch deviation of the balls instead of the angular pitch deviation of a gear. We calibrated the angular pitch deviation using a coordinate measuring instrument (CMM) at the NMIJ and adapting a multiple-orientation technique. We proposed a calibration strategy of the angular pitch deviation. The calibration value of the pitch deviation for the MBA at the NMIJ was obtained with a measurement uncertainty (U95) of 0.2 µm. We evaluated the pitch-measuring accuracy of a GMI using the calibrated MBA. Each value of U95 for the cumulative and single pitch deviations for the left and right flanks was less than or equal to 0.5 µm. The small uncertainty was transferred from the NMIJ to the GMI.