5-axis Milling Research Articles

Tool axis adjustment for 5-axis roughing operations

The increased accessibility of the tool achieved by using 5-axis roughing reduces the overall machining time of complex parts by reducing or eliminating the re-roughing and semi-finishing operations thereby decreasing the volume of remaining material before finishing operations. However, 5-axis milling generates significant variations in tool orientation which, combined with the high tool engagement in the material required by the roughing conditions, can be penalizing. Controlling these variations is therefore mandatory to guarantee the tool life, the productivity and the quality of the roughing operation. Thus, a multi-objective optimization is proposed to define the successive orientations of the tool axis along the path that minimize the feedrate slowdowns and thus the machining time, balance the pushing or pulling machining configurations and respect the programmed scallops heights of the machined surface. In this work, the tool path is defined by two curves, one constraining the position of the tool and the other its orientation allowing for a parametric synchronization to conduct the optimization. From the definition of the weights of each of the minimization objective functions, it is possible to find a tool axis orientation solution that satisfies the given constraints all along the path. The application on a test part by simulation and machining highlights the effectiveness of the proposed approach and the advantages of controlling the evolution of the tool axis orientation in 5-axis roughing.

Minimisation of Pose-Dependent Regenerative Vibrations for 5-Axis Milling Operations

The machining of free-formed surfaces, e.g., dies or moulds, is often affected by tool vibrations, which can affect the quality of the workpiece surface. Furthermore, in 5-axis milling, the dynamic properties of the system consisting of the tool, spindle and machine tool can vary depending on the tool pose. In this paper, a simulation-based methodology for optimising the tool orientation, i.e., tilt and lead angle of simultaneous 5-axis milling processes, is presented. For this purpose, a path finding algorithm was used to identify process configurations, that minimise tool vibrations based on pre-calculated simulation results, which were organised using graph theory. In addition, the acceleration behaviour of the feed drives, which limits the ability of adjusting the tool orientation with a high adaption frequency, as well as potential collisions of the tool, tool chuck and spindle with the workpiece were considered during the optimisation procedure.

Digital twin-based analysis of volumetric error mapping procedures

The evaluation of the volumetric accuracy of a machine tool is an open challenge in the industry, and a wide variety of technical solutions are available in the market and at research level. All solutions have advantages and disadvantages concerning which errors can be measured, the achievable uncertainty, the ease of implementation, possibility of machine integration and automation, the equipment cost and the machine occupation time, and it is not always straightforward which option to choose for each application. The need to ensure accuracy during the whole lifetime of the machine and the availability of monitoring systems developed following the Industry 4.0 trend are pushing the development of measurement systems that can be integrated in the machine to perform semi-automatic verification procedures that can be performed frequently by the machine user to monitor the condition of the machine. Calibrated artefact based calibration and verification solutions have an advantage in this field over laser based solutions in terms of cost and feasibility of machine integration, but they need to be optimized for each machine and customer requirements to achieve the required calibration uncertainty and minimize machine occupation time.This paper introduces a digital twin-based methodology to simulate all relevant effects in an artefact-based machine tool calibration procedure, from the machine itself with its expected error ranges, to the artefact geometry and uncertainty, artefact positions in the workspace, probe uncertainty, compensation model, etc. By parameterizing all relevant variables in the design of the calibration procedure, this simulation methodology can be used to analyse the effect of each design variable on the error mapping uncertainty, which is of great help in adapting the procedure to each specific machine and user requirements. The simulation methodology and the analysis possibilities are illustrated by applying it on a 3-axis milling machine tool.

Prediction of cutting force based on machining parameters on AL7075‐T6 aluminum alloy by response surface methodology in end milling

AbstractCutting forces modeling is the basic to understand the cutting process, which should be kept in minimum to reduce tool deflection, vibration, tool wear and optimize the process parameters in order to obtain a high quality product within minimum machining time. In this paper a statistical model has been developed to predict cutting force in terms of geometrical parameters such as rake angle, nose radius of cutting tool and machining parameters such as cutting speed, cutting feed and axial depth of cut. Response surface methodology experimental design was employed for conducting experiments. The work piece material is Aluminum (Al 7075‐T6) and the tool used is high speed steel end mill cutter with different tool geometry. The cutting forces are measured using three axis milling tool dynamometer. The second order mathematical model in terms of machining parameters is developed for predicting cutting forces. The adequacy of the model is checked by employing ANOVA. The direct effect of the process parameter with cutting forces are analyzed, which helps to select process parameter in order to keep cutting forces minimum, which ensures the stability of end milling process. The study observed that feed rate has the highest statistical and physical influence on cutting force.

Effect of CAD/CAM Bur Deterioration on the Surface Roughness of Ceramic Crowns.

To evaluate the effect of repetitive milling on the surface roughness of ceramic crowns. Twenty feldspathic ceramic crowns (VITABLOCS Mark II; Vita Zahnfabrik, Bad Säckingen, Germany) milled with hard milling protocol, and 20 zirconia crowns (5Y-TZP, inCoris TZI; Dentsply Sirona, York, PA) milled with soft milling protocol, using a 5-axis milling machine (inLab MC X5; Dentsply Sirona) were investigated. Atomic force microscopy (SPM SmartSPM™-1000) was used for surface roughness measurements (Ra, RMS). Pearson correlation between bur deterioration percentage as provided by the software of the milling machine and surface roughness was performed with an (r) range between 1 and -1. Trend analysis between the 2-half and among the 4-quarter bur lifetime was performed with linear contrast analysis and partial eta squared (η) for estimate of effect size. Analysis of mean variance between the zirconia and feldspathic ceramic groups was performed with a t-test, with α = 0.05. Correlation analysis showed small correlation for Ra, RMS (r = -0.02, -0.16 for the feldspathic ceramic crowns and r = 0.044, 0.034 for the zirconia crowns), and no significant differences for the 2-half and 4-quarter groups (p > 0.05) for both crown types. Estimate of effect size was rated as medium for the 2-half groups (Ra = 0.420, RMS = 0.395) and large for the 4-quarter groups (RA = 0.22, F = 1.48, RMS = 0.19, F = 1.26) for the feldspathic ceramic crowns, and small effect size for the 2-half groups (Ra = 0.18, RMS = 0.20) and the 4-quarter groups (Ra = 0.035, RMS = 0.037) for the zirconia crowns. There was no significant difference (p = 0.178, F = 0.016. p = 0.088, F = 0.002) between the feldspathic ceramic and zirconia crowns with medium and large effect size (0.45, 0.57) for RA and RMS. Milling zirconia and feldspathic ceramic crowns had small correlation between bur deterioration and surface roughness when the burs were used within their recommended lifetime. However, hard milled feldspathic ceramic crowns had higher surface roughness than the soft milled zirconia crowns. Bur deterioration had a larger effect on the surface roughness of the feldspathic ceramic crowns than the zirconia crowns.

Development and clinical application of custom-made temporomandibular joint-skull base combined prosthesis

Objective: To introduce the design, manufacture and clinical application of the custom-made temporomandibular joint (TMJ)-skull base combined prosthesis and evaluate its safety, effectiveness and accuracy. Methods: The patients diagnosed with the TMJ-skull base lesion in Department of Oral Surgery, Shanghai Ninth People's Hospital from October 2016 to November 2020 were recruited in this study. The maxillofacial CT data for all the patients were obtained and transformed into the Mimics 18.0 software preoperatively. The custom-made TMJ-skull base combined prosthesis, included four components, was designed based on the anatomy, stress distribution and movement of the TMJ and skull base, and fabricated by three-dimensional printing and 5-axis milling technologies. The TMJ-skull base lesion was excised completely with the help of digital templates from modified preauricular and/or post and submandibular incisions. The combined prosthesis were implanted and fixed after the lesion resection. The examinations including general situation, cranio-maxillofacial structure and function were taken during and after surgery to assess its using effect. Results: Ten patients [6 females and 4 males, (43.2±13.6) years old] were included and all prostheses were positioned accurately and fixed excellently. After (29.4±17.3) months follow-up, the occlusion relationship was stable and no adverse symptoms such as dizziness, headache, meningeal irritation and permanent facial nerve injury occurred. The pain, diet, mandibular movement function, lateral movement to diseased side and mouth opening had significant improvements. The forward movement and lateral movement to normal side were not improved significantly. There were no prosthesis displacement, loosening and fracture in X-ray and CT postoperatively. With the pre and postoperative craniomaxillofacial model merging, the maximal implanted error was (0.52±0.17) mm for fossa and condyle and (1.62±0.26) mm for skull base and mandibular handle in surface deviation analysis. Conclusions: The custom-made TMJ-skull base combined prosthesis with customized design and 3D printing fabrication is safe, effective and precise in clinical application.

Experimental comparison of different automatically tuned control strategies for active vibration control

Chatter is the main limiting factor affecting the material removal rates of machine tools and is caused by the machine's most flexible structural mode shapes. The use of active vibration control systems can damp the structural mode shapes and, in turn, significantly increase the chatter-free depth of cut. In order to reduce the commissioning effort, previous publications have introduced methodologies to automatically tune various control strategies for active damping. This paper presents a new automatic tuning approach for a robust model-based controller, which uses particle swarm optimization to find the best-performing control parameters. The proposed method was tested on both a 5-axis milling machine and a vertical lathe, together with an automatically tuned direct velocity feedback controller and an adaptive controller. The performance was evaluated by conducting extensive cutting tests under industrial operating conditions. All controllers and automatic tuning methodologies led to notable increase in chatter-free material removal rates, reduced vibration amplitudes, and improved surface roughness.

Marginal and Internal Adaptation of Lithium Disilicate Endocrowns Fabricated By Heat-Pressable and Subtractive Techniques.

To evaluate and to compare the marginal and the internal fit of milled (MLE) and heat-pressed lithium disilicate endocrowns (PLE). Thirty mandibular molars were prepared following the circumferential butt margin endocrown preparations; the cervical margin is parallel to the occlusal surface without ferrule design. A digital scan of molars was made using an intraoral digital scanner. The samples were separated into two groups (n = 15 per group); MLE: endocrowns were milled using LDS blocks and a 5-axis milling machine, PLE: endocrowns were heat-pressed using lost wax technique and LDS ingots. Marginal and internal adaptation were assessed using a replica technique and a stereomicroscope, selecting 32 measurements on each endocrown. Data were analyzed with one-way repeated measures ANOVA, two-way repeated measures ANOVA, student's t-test and paired student t-test (α = 0.05). Statistically significant interactions were recorded between fabrication technique and region (p < 0.05), F (1.97, 27.69) = 5.462. Group MLE displayed significantly smaller gaps than PLE in all regions (p < 0.001). The largest gap was observed at the pulpal floor in both groups. The internal gap was significantly larger than the marginal gap in MLE group (p < 0.001), while no statistically significant difference was observed in PLE group (p = 0.082). Heat-pressed and milled lithium disilicate endocrowns are clinically suitable, but the milled technique displayed a better fit than heat-pressed technique when marginal and internal adaptation were examined.

An analytical prediction model of surface topography generated in 4-axis milling process

An analytical prediction model of surface topography generated in 4-axis milling process

Light-weighting of single-sided motorcycle swing-arm through generative design

This work explores the prospects of Generative Design to generate the single-sided swing-arm of a homologated motorcycle to perform the process of light-weighting by selecting two aluminum alloys, namely Al 6061 (primary) and Al 7075 (reference), as materials and 5-axis milling as the manufacturing method. This work also cites and summarizes a couple of previous studies to establish the findings that Al 7075 is a superior material for the manufacturing of the single-sided swing-arm when compared to steel and further proceeds to expatiate as to why Al 6061 should be considered as opposed to Al 7075 for increased gains from the process of light-weighting with substantiations from the analysis of the single-sided swing-arm under the simulated loads.

Construction of Milling Force Model of Cycloid Gear

The change of the milling force during the milling process will directly affect the machining accuracy of the cycloid gear. In this article, the milling force prediction model of the cycloidal gear is used to predict the milling force of the cycloid gear. The results show that when the spindle speed increases, the milling force gradually decreases; the milling force is also closely related to the feed speed, axis milling depth and radial milling width. With the increase of axial milling depth and radial milling width, the milling force gradually increases, but the magnitude of the increase is different.

Effect Of Different Milling Devices On Marginal Fit Of CAD-CAM Zirconia Copings On Implant Stock Abutments.

To compare the marginal fit and internal surface roughness of CAD/CAM zirconia copings milled with 3- and 5-axis milling devices. Forty titanium implant stock abutments (4.8 mm in diameter, 4 mm in height) screwed to dental implants (4.1 mm in diameter) embedded in resin were considered phantoms and included in this in vitro study. All 40 phantoms were scanned with the same intraoral scanner, from which images of the virtual wax-up of zirconia copings were obtained and exported as standard tessellation language (STL) files. From each resulting STL file, two copings were milled: one using a 3-axis milling device, and the other using a 5-axis milling device. After milling, zirconia copings underwent high-speed sintering before being analyzed for marginal fit (ie, marginal gap measurement), and internal surface roughness was assessed with a scanning electron microscope (SEM). Statistical comparisons between groups were assessed with Mann-Whitney test. Median marginal gap values were 34.80 μm (95% CI: 0.00 to 173.98) for the 5-axis milling device group and 141.97 μm (95% CI: 82.13 to 163.46) for the 3-axis milling device group. A statistically significant difference in marginal gap was found between both milling device groups (P = .039). In addition, qualitative SEM analysis indicated higher internal surface roughness for the 3-axis milling device group. Within the limitations of this study, the present findings suggest that 5-axis milling devices outperform 3-axis milling devices for milling CAD/CAM zirconia copings from intraoral scans of implant stock abutments.

In Vitro Comparison of Marginal and Internal Fit of Zirconia Copings Fabricated by One CAD/CAM System with Two Different Scanners.

Objectives: Marginal and internal fit of restorations are two important clinical factors for assessing the quality and durability of computer-aided design/computer-aided manufacturing (CAD/CAM)-fabricated monolithic zirconia restorations. The purpose of this study was to evaluate the marginal and internal fit of CAD/CAM zirconia crowns with two different scanners (i3D scanner and 3Shape D700). Materials and Methods: Twelve extracted sound human posterior teeth were prepared for full zirconia crowns. Two different extraoral scanners namely i3D scanner and 3Shape D700 were used to digitize type IV gypsum casts poured from impressions. The crowns were milled from presintered monolithic zirconia blocks by a 5-axis milling machine. The replica technique and MIP4 microscopic image analysis software were utilized to measure the marginal and internal fit by a stereomicroscope at ×40 magnification. The collected data were analyzed by paired t-test. Results: The mean marginal gap was 203.62 μm with 3Shape D700 scanner and 241.07 μm with i3D scanner. The mean internal gap was 192.30 μm with 3Shape D700 scanner and 196.06 μm with i3D scanner. The results of paired t-test indicated that there was a statistically significant difference between the two scanners in marginal fit (P=0.04); while, there was no statistically significant difference in internal fit (P=0.761). Conclusion: Within the limitations of this study, the results showed that type of extraoral scanner affected the marginal fit of CAD/CAM fabricated crowns; however, it did not have a significant effect on their internal fit.

Design and modelling of a universal CNC machine

This paper proposes a method of designing an affordable, universal Computer Numerically Controlled (CNC) machine for the use by hobbyists and university laboratories. The machine combines the functions of a 3 to 4-axis milling machine and of a 3D printer. We discuss the major factors contributing to manufacturability and dimensional accuracy of the produced parts, and make several suggestions that aim to maximize the cost effectiveness of the machine’s design. A methodology is developed for optimizing the machine’s rigidity and dimensional accuracy by selecting the proper off-the-shelf components. A calculation that follows the proposed method starts when the required level of accuracy and the machining speed is specified; the result of such a calculation is the overall design of the CNC machine, a bill of materials, and the cost estimate. The design can be optimized for cost, weight, or other parameters. The model presently accounts for the forces generated by the cutting action, the acceleration of machine components, and the associated simple bending moments. The future work in this area relates to the improvement of the proposed method and mathematical model to account for the twisting moments, friction, and vibration.

Research of design an educational modular 5 axis milling machine

Industrial CNC machine tools are supplied as closed architecture systems. Their structure, kinematics and CNC controllers are designed to be used exclusively for their basic purpose, without any possibility of being changed. Reconfiguration is seen as the ability to add or remove modules from the machine, to be equipped with additional degrees of freedom (axes). For the concept to become a reality, it is necessary that the machine tool can be easily assembled and disassembled by an end-user and can adapt to changing projects or machining requirements. The approached of this research was to develop a 5-axis modular machine tool, with technological capabilities similar to industrial ones, at an affordable level of development costs and suitable to be used for teaching CAM techniques for future engineers.

New mechanistic model to predict machining time for milling free form geometries using 4-axis milling

Predicting the required time to machine a component is very important for planning the production of a factory. However, in milling of free form parts, commercial CAM software are not able to estimate the time precisely. This is because the CAM does not consider individual machine limitations. This work presents a mechanistic method developed to estimate more accurate the time to mill a free form geometry using any 4-axis milling machine. The maximum error observed on experimental validation of the method was less than 6%, 200 times more accurate than commercial CAM.

A digital twin study for immediate design / redesign of impellers and blades: Part 1: CAD modelling and tool path simulation

This paper presents a digital twining study conducted for an immediate design / redesign and manufacturing of on impellers & blades. It is by accomplished by developing (i) CAD automation methods, based on the standard modelling procedures and (ii) Manufacturing automation based on the 3/3 + 1/3 + 2/5 axis milling process. Initially, the CAD model of impeller / blade is created by utilizing the dimensional parameters obtained through standard design calculations / data. It is then parametrized and converted to an automated model through simple dimensional rules and geometric algorithms developed for the purpose. After this stage, the CAD model is analyzed for manufacturing automation where the process planning data comprising cutting tools, process parameters and setups are selected. Here, the tool paths are generated for 3/3 + 1/3 + 2/5 axis milling considering a CNC Vertical Machining Center (VMC) to digitally twin milling process. Both the CAD modelling and manufacturing process plans including tool path generation are captured through journaling and customized / improved using the Application Programmable Interface’s (API’s) to suit the present scope. In this paper, the first part on CAD modelling and manufacturing simulation methodologies are discussed through validating the digital twining concept in a virtual environment. The work is developed with the focus to help industries moving towards Industry 4.0 and requiring a constant design improvement in their products. It is by emphasizing the importance of digital twinning concept where a concurrent verification of design and manufacturing process can be achieved.

Effect of inclination and rotation of the sheet on sheet thinning and formability in robot assisted incremental sheet metal forming

Single point incremental forming (SPIF) has higher formability than other sheet metal forming processes. In SPIF, the existing computer numeric control (CNC) incremental forming which adopts 3-axis CNC milling machine to form the part incrementally by using a hemispherical tool has the limitation of forming steeper wall angle parts. An additional 2-degree of freedom (DOF) manipulator has been proposed to integrate with the existing 3-axis CNC milling machine to improve the formability of the sheet. In this method, to control the material flow and deformation state, the posture of the sheet has been changed by tilting the sheet along the needed direction and rotating at specific speed with respect to the vertical forming tool. Formability of the sheet has been investigated in terms of sheet thinning and strain distribution after deformation. Numerical simulation has been implemented initially and has been validated by conducting the experiments. The result of the research shows that formability can be improved by adding the 2-DOF manipulator to the existing system.

Surface error shape identification for 3-axis milling operations

In 3-axis milling operations the surface error caused by the tool/workpiece static deflection assumes a certain shape along the axial depth of cut. The error shape changes considerably according to the cutting strategy, tool geometry and cutting parameters. This paper presents a comprehensive method to identify all the types of surface error profile in down-milling, proposing dedicated analytical equations. This approach has been experimentally validated to assess its accuracy and limits. The results of this approach are meant to ease the surface error prediction and measurement by reducing the number of points to consider along the axial depth of cut.

Feature-based modelling and artificial intelligence-based computer assisted process planning systems for three axis milling components

Feature-based modelling and artificial intelligence-based computer assisted process planning systems for three axis milling components