Modelling and simulation of surface topography machined by peripheral milling considering tool radial runout and axial drift

Based on the Z-map model of a workpiece and the dynamic cutting forces model of peripheral milling in which the regenerative effect of tool radial runout and axial drift are considered, a model for the prediction of surface topography in peripheral milling operations is presented. According to the stability lobe diagram obtained by the zero-order analytical method, the relationship between spindle speed and surface topography, the tool radial runout, and the axial drift following the chatter are studied. The results show that a stable cutting status but a poor surface finish is obtained at the spindle speeds at which the dominant frequency of the milling system is integral multiples of the selected machining frequency, and a stable cutting status with a good surface finish can be obtained near and on the left side of the resonant spindle speeds determined by the predicted stability lobe diagram. The motion equations of any tooth end mill for peripheral milling are established, and these equations are based on the transformation matrix and the vector operation principle of motion-homogeneous coordinates. In addition, the simulation algorithm and the system of surface topography generated in peripheral milling are given based on the Z-map model. Cutting tests are carried out, and good agreement between the measured surface topographies and the topographies predicted by the model in this study is found in terms of their shape, magnitude, feed mark, profile height of cross-section, and surface roughness. The simulation results show that the milling surface roughness increases with the increase in feed per tooth, which further shows that this simulation system has high credibility. Thus, the simulation and experimental results can provide some practical instructions for the actual peripheral milling in determining the optimal machining conditions.

Karakteristik permukaan dan struktur mikro Pada bahan aluiminium 6061menggunakan Pahat Karbida dengan metode pemesinan laju tinggi dan pemesinan kering

Penelitian pemesinan laju tinggi dan kering dengan tujuan untuk kemasan permukaan yang meliputi corak permukaan cacat (defect) yang diakibatkan oleh kondisi pemesinan pada bahan aluminium 6061 menggunakan pahat karbida. Pengumpulan data pengujian pemesinan ini dilakukan menggunakan metode faktorial data sebanyak 8 kali percobaan dengan 3 variabel utama yaitu laju pemotongan(V), laju pemakanan (f) dan kedalaman potong (a) pada tiga tiga tingkat besaran. Dari percobaan yang telah direkomendasikan dengan kondisi pemesinan terbaik maka didapati beberapa Nilai kekasaran permukaan sangat ditentukan oleh aus pahat yang tinggi. Aus pahat yang tinggi (0.129-0.247)sangat berpotensi terjadi cacat berupa koyak permukaan (tearing surface) permukaan benda kerja termesin, pada laju pemakanan yang tinggi terjadi feed mark goresan karena laju pemakanan yang tinggi .Lebar butiran pada mikrostruktur sangat ditentukan oleh kecepatan potong, dimana pada kecepatan potong V= 1000 m/min besarnya butiran terlihat lebih melebar sedangkan pada V=1250 m/min besar butiran terlihat lebih rapat

Difference of Feed Marks in Cutting Fluids when Turning Stainless Steel

In this study, the difference of finished surface roughness and feed mark shape in lubricity of the cutting fluids were investigated in turning SUS440C. In the cutting speed of 20m/min, the oil having excellent oiliness caused the smallest finished surface roughness among the tested cutting fluids at the feed rate of 0.1mm/rev, while, the oil having high extreme pressure property was best at the feed rate of 0.2mm/rev. The feed marks were hardly recognized at any conditions. In the cutting speed more than 20m/min, the finished surface roughness in any lubricant conditions showed almost the same or slightly larger compared with that in dry conditions. The feed marks were recognized, and the transcription of cutting edges shape under wet conditions trended to be the same or worse than dry conditions.

A Study of Surface Integrity when Machining Refractory Titanium Alloys

In this paper, the surface integrity is studied when machining the aeronautical titanium alloys. Surface roughness, lay, defects, microhardness and microstructure alterations are studied. The result of surface roughness judges that the CVD-coated carbide fails to produce better Ra value than the uncoated. Lay is characterized by cutting speed and feed speed directions. Feed mark, tearing surface, chip layer formation as built up layer (BUL), and deposited microchip are the defects. Microhardness is altered down to 350 microns beneath the machined surface. The first 50 microns is the soft sub-surface caused by thermal softening in ageing process. Microstructure alteration is observed in this sub-surface. Down to 200 microns is the hard sub-surface caused by the cyclic internal work hardening and then it is gradually decreasing to the bulk material hardness. It is concluded that dry machining titanium alloy is possible using uncoated carbide with cutting condition limited to finish or semi-finish for minimizing surface integrity alteration.

Applications of Numerical Analysis of Hobbing to Hob Wear, Cutting Force and Gear Tooth Surface Topography

A new analytical technique is developed to calculate the volume cut with every hob tooth, cutting forces and feed mark patterns. The results of calculation are compared with experimental data, resulting in their good agreements. The estimation of wear of each hob tooth, hobbing forces and errors in hobbing can be obtained by calculation using this analytical method.

Geometric Simulation of Ball-End Milling Operations

In this paper, B-rep solid modeling techniques are used to deal with geometric modeling issues encountered in ball-end milling simulation. The precise B-rep model of the cutter swept volume is developed using advanced sweeping/skinning techniques. Semi-finishing operations are simulated by performing consecutive Boolean operations between the updated part and swept volume. The instantaneous chip geometry is accurately and reliably extracted from the B-rep model of the updated part. Also, the material removal in ball-end milling is precisely simulated for finishing operations, in order to construct the feed-mark and scallop geometries. The validity of the final model is confirmed by comparing the predicted feed-mark profile with experimental measurements. The system developed can be used to verify and optimize NC codes, thus contributing to improving reliability, accuracy, and productivity in CNC machining.