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CNC milling in the workshop
CNC control of milling machiens is now available to even the smallest of workshops. This allows designers to be more ambitious and machinists to be more confident of the production of parts, and thereby greatly increase the potential of milling at home. This guide takes a practical approach to software and techniques, and explains how you can make full use of your CNC mill to produce ambitious work of a high standard.
Book
The milling–milling machining method and its realization
We proposed a new processing method to reduce the cutting force of the machining process effectively, as well as to improve tool life and machining process efficiency. The proposed method, called the milling–milling machining method, is a new form of composite machining that is similar to the turn-milling method. It combines the advantages of face milling and helical end-milling cutters and uses the synthesis motion of these kinds of cutters to complete surface processing. This technique effectively reduces cutting force and, thus, improves tool life and machining efficiency. The milling–milling machining method has the advantages of a large diameter face mill with a large milling area, a low cutting force, a stable and highly efficient cutting process that is similar to that of a helical end-milling cutter, and trochoidal milling. The outstanding characteristics of face milling and helical end-milling cutters can be applied directly to the milling–milling machining method. In addition, the proposed method has unique features. The up–down milling–milling machining method can offset a portion of the cutting forces. Apart from proposing the theory for the milling–milling machining method, we also designed new equipment, namely the planetary cutter, milling–milling driving head, and a computer numerically controlled milling–milling machine. We compared the proposed method and the common face milling method from the perspective of cutting forces. Experimental results show that the milling–milling machining method considerably reduces cutting forces compared with conventional methods.
Journal Article
Modelling and prediction of surface topography on machined slot side wall with single-pass end milling
The previous research on machined surface topography in milling processes usually focuses on simple and single machining features such as free flat and form surfaces. However, the industrial components are composed of complex machining features such as slots and grooves finished by profile milling cutters. The formation mechanism and prediction method of machined surface topography for the complex milling features are required in industrial applications. Firstly, the machined side surface topography formation mechanism in profile milling straight slot machined by single-pass processing with a solid end mill is presented. Then, the numerical prediction models for machined side surface roughness in straight slot profile end milling are proposed. The proposed model can accurately predict the surface topography, and the relative prediction errors of the surface roughness (Sa) are within 6.34% for the whole cases in this research. Finally, the effect of cutting parameters on the residual heights of the machined side surface is analyzed. The formation mechanisms of machined two side surface topographies on the straight slot are distinct, for which one side surface is machined by up milling while another is by down milling. It is shown that the different tool trajectories cause the distinction for milling each slot side. The machined side surface topography can be controlled by selecting optimized tool motion parameters and cutting parameters. The influences of tool deflection and tool wear on the surface topography are ignored in the current research, which will be considered in the future.
Journal Article
Based on the instantaneous milling thickness of unequal pitch end milling cutter milling force solution and simulation research
The unequal pitch end milling cutter can change the feed per tooth and the cut-in and cut-out period of each cutter tooth by changing the distribution of the pitch of the end milling cutter so that the energy in the milling frequency domain is dispersed to achieve the purpose of reducing the milling vibration. Because the amplitude of vibration in the milling process is closely related to the milling force, this paper establishes the instantaneous static milling thickness model based on the real trajectory of the milling edge according to the milling process of the end milling cutter with unequal pitch and establishes the instantaneous dynamic milling thickness model based on the regeneration effect, on which the instantaneous milling force model is established. At the same time, the relationship model of milling force coefficient is established according to the average milling force method. From the relationship model of milling force coefficient, the linear relationship between average milling force and average feed per tooth is obtained. Then, the finite element simulation method is used to simulate the actual milling process of milling typical material Al7075-T6 with unequal pitch end mill, and the milling force coefficient is fitted by the simulation results. Finally, the accuracy of the milling force model and the finite element model has been validated through experiments, and the feasibility of calibrating the milling force coefficients through finite element simulation method has been demonstrated. The milling force model of unequal pitch end mill and the method of calibrating the milling force coefficient by finite element simulation proposed in this paper will provide a theoretical basis for the study of unequal pitch end mill in vibration reduction.
Journal Article
Quality enhancement of micro-milled channels with automated laser assistance
Microchannels are utilised on material surfaces of a body, allowing coolant to pass through them and enabling heat dissipation by increased contact area. Fabrication of metal surface microchannels is primarily achieved by employing a micro-milling process, which has drawbacks such as excessive cutting forces, top burrs, tool wear, and lower tool life. Alternatively, it is also realised by using Laser micro milling, which has problems associated with lower quality of surface finish, un-desired taper, heat-affected zone, and spatters. The existing literature, after due review of the current state of the art, has brought out gaps needing attention. These gaps are limited capability to reduce surface roughness, unaddressed burr width, and irregular bottom surface morphology, which affect microchannel quality. These gaps motivate this research work to improve and sustain the microchannel quality. To achieve the goals, this research work performs the fabrication of microchannels by micro-milling with automated laser assistance being achieved in two ways (a) sequentially, (b) non-sequentially, termed as LASMM and LPCMM, which are novel for the scientific community. The effects of micro milling parameters, spindle speed and feed on the quality were analysed while machining commercially pure titanium (cp-Ti). Results show that laser assistance to micro-milling provides a lower generation of undesired forces and lesser top burrs compared to micro-milling alone. In sequential laser assistance, the channels have a mean down burr width ~ 58% lower and a maximum down burr width ~ 38% lower than the channels done non-sequentially. In the case of up-burr width, a mean value ~ 60% lower and a maximum value ~ 73% lower is achieved in channels done non-sequentially as compared to those done sequentially. In the case of surface roughness, channels done sequentially have a maximum Sa value of 1.508 µm, a maximum Sq value of 1.912 µm whereas non-sequentially, they show a maximum Sa value of 3.495 µm, maximum Sq value of 4.59 µm. Steady tool wear is observed sequentially, whereas in non-sequential, rapid tool wear occurs after 500 mm of cutting length.
Journal Article
Cutting force and nonlinear chatter stability of ball-end milling cutter
Ball-end milling cutters are one of the most widely used cutters in the automotive, aerospace, die, and machine parts industries. Milling chatter reduced the surface quality and production efficiency, resulting in noise. It is particularly important to model the cutting force and analyze the flutter stability of ball-end milling cutters. In this study, a simplified milling force model of ball-end milling cutter with three degrees of freedom was established based on Merchant bevel cutting theory. The model simplified the milling force coefficient. The expressions of instantaneous milling area considering the vibration displacements in
X
,
Y
, and
Z
directions were derived. The nonlinear dynamic cutting force model of ball-end milling cutter with three degrees of freedom was proposed. The nonlinear chatter vibration mechanical model of ball-end milling cutter with three degrees of freedom was developed by introducing the time delay term, and the stability analysis is carried out by the stability lobe diagram. The proposed models were experimentally verified.
Journal Article
Study on design, manufacture, and cutting performance of circular-arc milling cutters for machining titanium alloy
Titanium alloy is widely used for manufacturing structural parts of high-end equipment due to its excellent mechanical properties, despite difficulty in being machined. Nowadays, titanium alloy parts are mostly machined by ball-end milling cutters (BEMC), but the cutting edge structure of the BEMC limits the improvement in machining efficiency and surface quality of the parts. In this paper, a circular-arc milling cutter (CAMC) with large-curvature cutting edge was proposed; the differential geometry method was used for establishing the geometric model for the contour surface of the CAMC and the mathematical model for the spiral cutting edge line; the conversion matrix between grinding wheel and workpiece coordinates was introduced to derive the equation of grinding wheel trajectory when the rake face of the CAMC was ground; the self-designed CAMC was ground and tested in accuracy. The comparative research was conducted experimentally on the side milling of titanium alloy TC4 with the CAMC and BEMC, and consequently the variation laws of milling forces, wear morphology, and machined surface quality were obtained about the two types of milling cutters. The results indicated that the CAMC can effectively reduce the main milling force and keep the milling process stable. Moreover, the CAMC was worn slower and produced better surface quality than the BEMC.
Journal Article
A review on micro-milling: recent advances and future trends
Recently, mechanical micro-milling is one of the most promising micro-manufacturing processes for productive and accurate complex-feature generation in various materials including metals, ceramics, polymers and composites. The micro-milling technology is widely adapted already in many high-tech industrial sectors; however, its reliability and predictability require further developments. In this paper, micro-milling related recent results and developments are reviewed and discussed including micro-chip removal and micro-burr formation mechanisms, cutting forces, cutting temperature, vibrations, surface roughness, cutting fluids, workpiece materials, process monitoring, micro-tools and coatings, and process-modelling. Finally, possible future trends and research directions are highlighted in the micro-milling and micro-machining areas.
Journal Article
Study on design of conical arc side-edge milling cutter and cutting performance under ultrasonic-assisted condition
Ball-end milling cutters are commonly used in the finishing processes of curved-side milling for titanium alloys; however, several issues arise during machining, such as poor cutting conditions at the bottom of the end teeth, low cutting speeds, and limited chip space. Given the above issues, the research on the design and manufacture of conical arc side-edge milling cutter for titanium alloy processing was carried out in this paper; the mathematical model of the vital structure of conical arc side-edge milling cutter was established; the grinding trajectory equations of tool front and flank were deduced; the tool-workpiece kinematics of ultrasonic vibration applied to conical arc side edge was studied; and the comparative experimental study of the conical arc side-edge milling cutter cutting titanium alloy with and without ultrasonic vibration was carried out. The experiment results indicate that in comparison to conventional milling techniques, ultrasonic vibration cutting significantly decreases cutting force, plastic deformation of the chip, and wear rate of the flank face. The tool wear band is both longer and more uniform, bonding phenomena in titanium alloys are distinctly reduced, and tool performance is improved.
Journal Article
Energy field-assisted high-speed dry milling green machining technology for difficult-to-machine metal materials
Energy field-assisted machining technology has the potential to overcome the limitations of machining difficult-to-machine metal materials, such as poor machinability, low cutting efficiency, and high energy consumption. High-speed dry milling has emerged as a typical green processing technology due to its high processing efficiency and avoidance of cutting fluids. However, the lack of necessary cooling and lubrication in high-speed dry milling makes it difficult to meet the continuous milling requirements for difficult-to-machine metal materials. The introduction of advanced energy-field-assisted green processing technology can improve the machinability of such metallic materials and achieve efficient precision manufacturing, making it a focus of academic and industrial research. In this review, the characteristics and limitations of high-speed dry milling of difficult-to-machine metal materials, including titanium alloys, nickel-based alloys, and high-strength steel, are systematically explored. The laser energy field, ultrasonic energy field, and cryogenic minimum quantity lubrication energy fields are introduced. By analyzing the effects of changing the energy field and cutting parameters on tool wear, chip morphology, cutting force, temperature, and surface quality of the workpiece during milling, the superiority of energy-field-assisted milling of difficult-to-machine metal materials is demonstrated. Finally, the shortcomings and technical challenges of energy-field-assisted milling are summarized in detail, providing feasible ideas for realizing multi-energy field collaborative green machining of difficult-to-machine metal materials in the future.
Journal Article