Experimental Investigation on the Milling Performance of a 50 μm D-Shaped Micromilling Cutter with Different Materials

In micromilling, the performance and diameter of the milling cutter directly determine the service life of the milling cutter and the surface quality of the microgroove. Therefore, it is vital for high-precision milling to explore the milling performance of different materials and expand the application scope of micromilling cutter sizes. In this study, the milling performance of three kinds of material cutters—carbide, diamond coating and polycrystalline diamond (PCD)—was evaluated. A series of micromilling tests were carried out to determine the effects of cutter material type on cutter wear, surface quality and burr formation, particularly when a 50 µm micromilling cutter was used in the milling process. A D-shaped milling cutter with a diameter of 50 µm was manufactured on a self-developed high-precision modular machine tool by wire electrode electric discharge grinding (WEDG) technology. From theoretical and experimental perspectives, it is easy to master microgroove quality milled by different material cutters. The results show that the microgrooves processed with PCD cutters have fewer burrs, lower surface roughness values, and a smoother groove bottom morphology.

Bagging-gradient boosting decision tree based milling cutter wear status prediction modelling

Aiming to monitor wear condition of milling cutters in time and provide tool change decisions to ensure manufacturing safety and product quality, a tool wear monitoring model based on Bagging-Gradient Boosting Decision Tree (Bagging-GBDT) is proposed. In order to avoid incomplete tool state information contained in a single domain feature parameter, a multi-domain combination method is used to extract candidate characteristic parameter sets from time domain, frequency domain, and time–frequency domain. Then top 21 significant features are screened by eXtreme Gradient Boosting selection method. Synthetic Minority Oversampling Technique technology is integrated during feature selection to overly sample feature vectors, so that wear condition categories can be well balanced. Bagging idea is then introduced for parallel calculation of the gradient boosting decision tree and to improve its generalization ability. A Bagging-GBDT milling cutter wear condition prediction model is constructed and verified by public ball-end milling data set. Experiments show that random features and training samples selection can effectively improve prediction performance and generalization ability of prediction model. Our Bagging-GBDT model gains F1 score of 0.99350, which is 0.2% and 13.2% higher than the random forest algorithm and basic GBDT model, respectively.

Innovative Multifunctional Unit for Alternative Tillage

An alternative project of a tillage device is presented, the main working process of which is implemented through a destructive effect on the soil by directed impulse shocks of compressed air. It is shown that the main cultivation of the soil occurs by means of the main working body consisting of the spokes of the hubs and tips connected with a source of compressed air via a central main system. It is noted that behind the main working body there are auxiliary elements of the milling cutter and rollers using which the finishing of the soil takes place.

Research on Centroid Distribution and Dynamic Characteristics of Irregular Tooth End Milling Cutters

For irregular end milling cutters, the incomplete equality of the pitch angle and helix angle will lead to an uneven mass distribution. The problems of centroid distribution caused by this, and whether it would affect the dynamic characteristics of milling cutters, have not been systematically studied. In this paper, through the proposed mathematical model, the centroid positions of each radial section of four types of end milling cutters, with equal overall eccentricities and different structures, are calculated, respectively. The centroid distribution of end milling cutters is studied and analyzed. Combined with finite element analysis, the vibration mode, frequency, and resonance frequency band of each type of end milling cutter, under the same dynamic excitation, is obtained. Based on a study of the dynamic characteristics of various types of end milling cutters, it is found that the response displacement of the variable pitch variable helix end milling cutter is the smallest, which is 0.043800 mm. With the same level of accuracy, its dynamic performance is the best. On the premise of not changing the overall eccentricity of the end milling cutter, a new idea for the structural design to improve the dynamic characteristics of the end milling cutter is provided.

Study the Surface and Chip Formation of Wood Materials by Milling Method

This paper discusses the experimental study and the mechanism of chip formation, sliding and cutting in processing wood milling surface. The main objective is to determine chip thickness upon the coefficient k and tool tip radius ρ. Technically, when analysing we use FCCCD's second-order response surfaces method and analysis of variance (ANOVA) for determining the coefficient k upon the factors of milling cutter diameter D, the feeding per tooth Sz and tool tip radius ρ. According to the obtained experimental results, we determined the value domain of the machine's working factors so that the cutter tool tip can slide or cut the chip on the milled surface of tropical wood materials. From the coefficient k, we can determine the slide length Lsl which gives reason for the abrasion phenomenon of the front or rear sides of the cutter. The results allow us to choose the geometrical parameters ​​for milling cutter, apart from the working parameters for processing the surface of wood materials with the highest quality as possible.

Optimal design of helical flute of irregular tooth end milling cutter based on particle swarm optimization algorithm

Due to the variable pitch angle and helix angle of the irregular tooth end milling cutter, the mass of the integral end milling cutter is eccentric, and the high stability and precision design of the irregular tooth end milling cutter is still a challenge. Aiming at the influence of dynamic balance of irregular tooth end milling cutter which can not be ignored in high-speed milling, the parameterized design of radial section of irregular tooth end milling cutter was carried out. Based on the space transformation law of the centroid of helical flute, a new method for calculating the centroid coordinate of end milling cutter was put forward, and a general mathematical model of eccentricity of integral end milling cutter was given. It was proved that this model could accurately calculate the centroid position and eccentricity of the end milling cutter. The influence of pitch difference angle and helix difference angle on eccentricity of end milling cutter was studied and analyzed. The particle swarm optimization (PSO) algorithm was creatively applied to optimize the helical flute shape of the end milling cutter, the curvature radius of helical flute curve is optimized, so that the centroid coordinate is infinitely close to the origin of coordinate. The number of iterations was set to 200. In the 32nd iteration, the result approached to infinitesimal, the final function converged, and obtained the groove curvature radius of the milling cuter with the smallest eccentricity. The optimized eccentricity of the end milling cutter is infinitesimal, which can make the vibration damping performance of the end milling cutter be fully developed. On the basis of ensuring the same cutting performance, the cutting tool unbalance was effectively reduced and the dynamic performance of milling cutter was further improved.