Search Results (43)

Controlling macro-geometrical errors in the dry drilling of ductile cast iron remains a critical challenge for sustainable and cost-efficient automotive component manufacturing. This paper investigates the influence of cutting speed (v_c) and feed per revolution (f_n) on the dimensional and shape accuracy of holes drilled in EN-GJS-500-7 ductile cast iron using an HSS DIN 338 helical drill (Ø 11.8 mm, Ceratizit) on an AVIA VMC800 CNC milling centre. A one-factor-at-a-time (OFAT) experimental design was applied: the feed effect was evaluated at v_c = 10 m/min with f_n ∈ {0.10, 0.15, 0.20} mm/rev, while the speed effect was evaluated at f_n = 0.20 mm/rev with v_c ∈ {10, 25, 30} m/min. Cutting forces, torques, and vibration accelerations were recorded using an HBM MSC 10 transducer and a PCB 356A01 tri-axial accelerometer. Hole geometry was assessed on a Zeiss Contura G2 coordinate-measuring machine (CMM), and surface texture was evaluated with a TOPO 01P contact profilometer. The expanded measurement uncertainty (k = 2) was estimated based on duplicate test specimens. All drilled holes fell within the IT12 dimensional tolerance (PN-EN 22768-1:1999 grade c), with diameter oversizes ranging from +0.26 mm to +0.46 mm relative to the nominal bore. Cutting speed was identified as the dominant factor affecting both diameter oversize and cylindricity, which increased by 60% (from 0.10 to 0.16 mm) as v_c rose from 10 to 30 m/min. Vibration accelerations increased nonlinearly between v_c = 25 and 30 m/min (by a factor of 2.5×), indicating an approach to a structural resonance condition. The lowest surface roughness (R_a = 6.6 µm) was obtained at v_c = 25 m/min. These findings establish clear physical baselines for tool deflection limits, demonstrating that managing dynamic process stability is vital for optimising macro-geometrical accuracy in the dry machining of cast iron alloys. Full article

The invention concerns a screw-driven shredder for solid photopolymer resin, designed for both terrestrial use and prospective deployment in microgravity environments. The system addresses the need for efficient recycling of cured photopolymer waste generated by stereolithography (SLA) 3D printing—a process not yet implemented in orbit, but envisioned as part of future closed-loop additive manufacturing systems aboard space stations or lunar habitats. The proposed device is a compact, hermetically sealed mechanical unit composed of ten subassemblies, featuring two counter-rotating screw shafts equipped with carbide milling inserts arranged helically to achieve uniform and controlled fragmentation of solid SLA residues. The shredding process is supported by a pressurized inert fluid circuit, utilizing carbon dioxide (CO₂) as a cryogenic working medium to enhance cutting efficiency, reduce heat accumulation, and ensure particle evacuation under microgravity conditions. Studies indicate that CO₂-assisted cooling can reduce tool-tip temperature by 10–30 °C, cutting forces by 5–15%, and electrical power consumption by 5–12% while extending tool life by up to 50%. This invention thus provides a key component for a future in situ photopolymer recycling loop in space while also offering a high-efficiency shredding solution for Earth-based photopolymer waste management in additive manufacturing. Full article

Industry 4.0, in its search for improvements to processes and efficient products, has increasingly invested in the use and development of high-performance materials for its production lines. This is exemplified by the introduction of CFRP in the aeronautical industry, since this composite material has reduced the weight of aircraft and improved their performance. For the construction of large structures, drilling processes are also necessary to fix parts. However, this machining process can cause failures in the structure as a whole. These structural failures occur due to fragmentation, tearing, or detachment of the matrix fiber, significantly reducing the quality and reliability of the final equipment. In this scenario, it is important to preventively detect these intrinsic production failures that lead to the condemnation of the final parts. One indirect detection method is acoustic emission. This work presents a feasibility study focused on the application of data-driven methods for delamination detection and tool wear monitoring in composite machining. A setup for a helical interpolation end-milling drilling process was performed under varying machining conditions, from mild to severe, on CFRP composite plates. Acoustic emission (AE) signals were acquired at each machining pass. The methodology involved selecting an optimal frequency band to obtain information about the wear of the drilling tool through RMS and power spectral density (PSD) analysis, followed by using correlation indices to characterize tool wear progression. The results demonstrate the potential of spectral and statistical techniques to support real-time monitoring and decision-making in advanced composite manufacturing. Full article

This study investigates the machining challenges of fiber-reinforced composite materials (FRCMs), focusing on carbon fiber-reinforced polymer (CFRP) plates, which exhibit high abrasiveness, delamination tendency, and accelerated tool wear. Two solid carbide helical end mills, designed for composite machining, were evaluated through helical interpolation drilling. Acoustic emission signals were continuously acquired via a piezoelectric sensor during standardized cycles, and tool wear was assessed using confocal microscopy and a digital altimeter. Signal processing played a central role, combining energy-based metrics and damage indices to identify the onset of wear and early delamination, enhancing the understanding of tool degradation and improving machining reliability. Full article

Plastic gears are used in a variety of industrial fields and are primarily produced by injection molding with a gear cavity. At present, EDM is usually used for machining gear cavities with metal materials, and the tool electrode used in the process is usually machined through a milling process. For helical gear cavities and helical bevel gear cavities, certain problems are encountered when the tool electrodes of EDM are obtained from milling procedures, including waste of raw materials and the complex technical process. Focusing on the above problems, this paper used copper powder to fabricate gear electrodes through a selective laser sintering process. The obtained gear electrodes underwent heat treatment and the effects of the main process parameters on the electrical conductance of tool electrodes were analyzed in this study. Finally, the heat-treated gear electrodes were applied to EDM to fabricate a helical gear cavity and a helical bevel gear cavity. During EDM, the TWR and MRR of the gear electrodes were 0.0029 mm³/min and 0.3872 mm³/min, respectively. Compared with that of gear electrodes made by the milling process, the MRR of the gear electrodes fabricated by SLS improved by 31.53%. Full article

Formed milling is one of the most commonly used methods for machining the helical surfaces of various screw rotors. The profile of a formed cutter is designed according to the profile of the helical surface, which is usually represented by discrete points. The most widely used analytical method is rather complex, and it is easy to obtain singular points. To obtain a reliable cutter profile and simplify the solution procedure, a general numerical method suited for rotors with an arbitrary tooth profile is proposed. The proposed method does not need to establish and solve the complex nonlinear contact equation and can determine the contact point accurately. Firstly, a series of intersection planes that are perpendicular to the revolving axis of the cutter is constructed. The searching of the contact points of the selected tooth curves with each intersection plane is achieved using the subdivision method. By this means, the plane–curve intersection is simplified to a straight line–curve intersection that can easily be solved via Newton iteration. Meanwhile, the machinability related to the profile of the formed cutter can also be analyzed. Two cutter profiles are used to validate the proposed method. The cutter profiles generated by the proposed method are compared with the profiles generated by the analytical method. The results indicate that the accuracy and computational efficiency increase significantly. Furthermore, the proposed method can also be applied to the design of formed grinding wheels. Full article

Helical milling presents a promising alternative to conventional drilling for hole production, offering superior surface quality and improved production efficiency. While this technique has been extensively applied in the aerospace industry, its potential for machining common engineering materials, such as AISI 1045 steel, remains underexplored in the literature. This study addresses this gap by systematically evaluating the influence of key process parameters—cutting speed (V_c), axial depth of cut (a_p), and tool diameter (D_t)—on hole quality attributes, including surface roughness, burr formation, and nominal diameter accuracy. A full factorial experimental design (2³) was employed, coupled with analysis of variance (ANOVA), to quantify the effects and interactions of these parameters. The results reveal that, with a higher V_c, it is possible to reduce surface roughness (R_a) by 30% to 40%, while an increased a_p leads to a 50% increase in R_a. Additionally, D_t emerged as the most critical factor for nominal diameter accuracy, reducing geometrical errors by 1% with a larger D_t. Burr formation was predominantly observed at the lower end of the hole, highlighting challenges specific to this technique. These findings provide valuable insights into optimizing helical milling for low-carbon steels, offering a foundation for broader industrial adoption and further research. Full article

Face milling with end-mill tools represents a solution for woodworking applications on small-scale or complex surfaces, but information regarding the surface quality per specific tool type, wood material, and processing parameters is still limited. Therefore, this study examined the surface quality of tangential oak and maple CNC face-milled with two end-mill tools—straight-edged and helical—for three values of stepover (5, 7, 9 mm) and two cutting depths (1 and 3 mm). The surface quality was analyzed with roughness parameters, roughness profiles, and stereomicroscopic images and was referenced to that of very smooth surfaces obtained by super finishing. The helical end mill caused significant fiber tearing in maple and disrupted vessel outlines, while prominent tool marks such as regular ridges across the grain were noticed in oak. The best surface roughness was obtained in the case of the straight-edged tool and minimum stepover and depth of cut, which came closest to the quality of the shaved surfaces. An increase in the cutting depth generally increased the core surface roughness and fuzziness, for both tools, and this trend increased with an increase in the stepover value. The species-dependent machining quality implies that the selection of tool geometry and process parameters must be tailored per species. Full article

The cutting length of milling tools must be longer than the axial distance of the material to be processed. In fact, in most cases, the cutting length far exceeds the thickness of the material to be removed. Therefore, along the entire length of the milling-tool flutes, only the area farthest from the shank wears out, leaving the rest of the tool practically without any wear, especially in the area closest to the shank. This research analyses a toolpath model to use the complete length of the milling tool flutes, in those machining operations in which it is possible, with the objective of reducing the costs associated with tool wearing and resharpening. This improves the tool performance, which clearly increases the sustainability of the milling process. For this purpose, it is necessary to transform the numerical control programme that performs a flat (2D) toolpath into a helical (3D) one by decomposing the arcs and rectilinear segments into a succession of points within a precision range. A negative aspect of this method is that it can only be applied to bottomless contours in processes of air-contour milling. Full article

This study focuses on a detailed analysis of the cutting forces in rotational turning, a novel machining process designed to achieve high surface quality and productivity. Unlike traditional longitudinal turning, rotational turning employs a helical cutting-edged tool that performs a circular feeding movement, introducing complex kinematics that complicates the accurate measurement of the cutting forces. To address this, the theoretical background was described for modeling the cutting force removal. The process was experimentally simulated on a CNC milling machine using a custom-designed measurement system. The major cutting force, passive force, and feed force were successfully measured and analyzed under varying feed conditions for both rotational and longitudinal turning. The results demonstrate a significant reduction in the passive force during rotational turning compared to longitudinal turning, which directly contributes to lower elastic deformation in the radial direction of the workpiece. This reduction improves the dimensional accuracy and stability during machining. Additionally, the feed force was observed to be slightly higher in rotational turning, reflecting the influence of the rotational movement of the tool. These findings highlight the advantages of rotational turning for applications requiring precision and surface quality, particularly where radial deformation is a critical concern. This study establishes a reliable methodology for force measurement in rotational turning and provides valuable comparative insights into its performance relative to conventional turning processes. Full article

The rake angles on both sides of the cutting edges of the hourglass worm gear hob significantly influence its cutting performance, which, in turn, plays a decisive role in the surface quality of the machined worm wheel. To balance the rake angles along the tooth height direction of each hob tooth and enhance the overall cutting performance of the hob, this paper proposes a method that utilizes a rotating paraboloid surface to generate the helical rake face of the hourglass worm gear hob. First, the conjugate condition equations for the rake face generated by the rotating paraboloid surface are derived. A mathematical model for the helical rake face of planar double-enveloping hourglass worm gear hob is established. This study explores the influence of two machining parameters on the rake angle, specifically the milling drive ratio coefficient k and the geometric parameter of a parabolic milling cutter p. Through a systematic analysis of the variations in rake angle at the dividing toroidal surface and along the tooth height direction, the optimal parameter values were identified as k = 0.9115 and p = 0.6834. The results show that, after optimization, the hob rake angle range is around ±4.7°, with a maximum rake angle difference of 6.3072° along the tooth height direction, and the rake angles on both sides of the teeth are more balanced. The structure of the rake face is more reasonable, reflecting the feasibility of rotating paraboloid tools for forming tools in the machining of complex surfaces. Full article

The fabrication of micro-holes in hard-to-machine materials presents considerable challenges in precision machining. This study proposes a novel approach that employs high-strength micro-grinding tools with a central abrasive grain absence to create micro-holes through helical grinding. Due to the random distribution of abrasive grains, the absence of grains at the tool’s center becomes an inevitable technical challenge. This research examines the correlation between the diameter of the absence zone and the bottom morphology of the machined hole, highlighting the potential formation of disc-shaped or cylindrical residues. A model for predicting the height of the disc-shaped residues is developed, and the mechanisms governing their removal during grinding are further explored. The findings indicate that when a central grain absence exists, the first abrasive grain surrounding the absence zone, referred to as the inner-edge grain, is responsible for removing the disc-shaped residues. Based on these results, a novel 0.8 mm diameter micro-PCD milling–grinding tool with a central edge absence is designed, and experimental validation is performed using 65% SiCp/Al composite materials. The experimental results confirm that the central grain absence leads to the formation of disc-shaped residues at the bottom of the machined hole during helical grinding, and the morphology of the experimentally obtained residues aligns with the theoretical predictions and simulations. This study significantly advances micro-grinding wheel technology and provides a solid foundation for the precision machining of micro-holes in hard-to-machine materials. Full article

SiC particle-reinforced Al metal matrix (SiCp/Al) composites are more and more widely used in the aerospace field due to their excellent properties, and the realization of high-quality drilling of SiCp/Al composites has an important impact on improving the performance of parts. In this paper, ultrasonic elliptical vibration-assisted helical milling (UEVHM) is applied to the machining of SiCp/Al composites. Firstly, the kinematic analysis of UEVHM is carried out, and then the cutting force model is established, which takes into account the interaction between particles and the cutting edge, and calculates the crushing force, pressing force, and debonding force of the particles. Finally, the UEVHM tests are conducted to verify the accuracy of the model and to analyze the influence of process parameters on the cutting force. It was found that the radial and axial forces decreased by 34% and 39%, respectively, when the spindle speed was increased from 2000 r/min to 10,000 r/min; the radial and axial forces increased by 200% and 172%, respectively, when the pitch increased from 0.1 mm to 0.4 mm; and the radial and axial forces increased by 29% and 69%, respectively, when the rotational speed increased from 30 r/min to 70 r/min. The maximum error between the cutting force model and the experimental values is 19.06%, which has a good accuracy. The research content of this paper can provide some guidance for the high-quality hole-making of SiCp/Al composites. Full article

In the industrial machining of wood–plastic composites, optimization of cutting parameters is key to improving workpiece machinability. To explore the influence of different milling methods of straight-tooth milling, helical milling, and tapered milling on the machinability of wood–plastic composite, a milling experiment was performed. Cutting force, cutting temperature, and surface roughness were selected as evaluative factors. Based on experimental results, principal component analysis was used to analyze the significance of each factor’s contribution and to assess different milling methods of wood–plastic composite for different needs. By calculating the total score from principal component analysis, the optimized cutting mode was determined to be straight-tooth milling, with feed per tooth of 0.2 mm and cutting depth of 0.5 mm. Milling methods in order of decreasing cutting force were helical milling > straight-tooth milling > tapered milling. Milling methods in order of decreasing cutting temperature were helical milling > tapered milling > straight-tooth milling. In terms of the tradeoff between surface quality and processing efficiency, tapered milling is suitable for finishing, considering the machining quality, while helical milling is suitable for roughing, considering the machining efficiency. One of the contributions of this study is to link three separate milling study systems (straight-tooth milling, helical milling, and tapered milling) into one system. Full article

Being a difficult-to-cut material, Fiber Metal Laminates (FML) often pose challenges during conventional drilling and require judicious selection of machining parameters to ensure defect-free laminates that can serve reliably during their service lifetime. Helical milling is a promising technique for producing good-quality holes and is preferred over conventional drilling. The paper compares conventional drilling with the helical milling technique for producing holes in carbon fiber-reinforced aluminum laminates. The effect of machining parameters, such as cutting speed and axial feed, on the magnitude of cutting force and the machining temperature during conventional drilling as well as helical milling is studied. It was observed that the thrust force produced during machining reduces considerably during helical milling in comparison to conventional drilling at a constant axial feed rate. The highest machining temperature recorded for helical milling was much lower in comparison to the highest machining temperature measured during conventional drilling. The machining temperatures recorded during helical milling were well below the glass transition temperature of the epoxy used in carbon fiber prepreg, hence protecting the prepreg from thermal degradation during the hole-making process. The surface roughness of the holes produced by both techniques is measured, and the surface morphology of the drilled holes is analyzed using a scanning electron microscope. The surface roughness of the helical-milled holes was lower than that for holes produced by conventional drilling. Scanning electron microscope images provided insights into the interaction of the hole surface with the chips during the chip evacuation stage under different speeds and feed rates. The microhardness of the aluminum layers increased after processing holes using drilling and helical milling operations. The axial feed/axial pitch had minimal influence on the microhardness increase in comparison to the cutting speed. Full article