Spiral Tool Path Research Articles

Spiral tool path generation method for complex pocket machining based on electrostatic field theory

Spiral tool path generation method for complex pocket machining based on electrostatic field theory

Hermite Quartic Splines for Smoothing and Sampling a Roughing Curvilinear Spiral Toolpath

From an industrial point of view, the milling of 2.5D cavities is a frequent operation, consuming time and presenting optimization potential, especially through a judicious choice of the tool trajectory. Among the different types of trajectories, some have a general spiral-like aspect and can potentially offer a reduced machining time. They are called curvilinear trajectories and are obtained by interpolation between structure curves, which are the numerical solutions of a partial differential equation. In this case, the machine tool will connect points, and the trajectory will be made up of small segments. While these trajectories exhibit all the necessary qualities on a macroscopic level for rapid tool movement, the tangential discontinuities at a microscopic scale, inherent in the discretization, significantly increase the machining time. This article proposes a method to reparameterize the structure curves of the curvilinear spiral with a set of C2 connected Hermit quartic spline patches. This creates a smooth toolpath that can be machined at an average feedrate closer to the programmed one and will, de facto, reduce the machining time. This article shows that the proposed method increases on two representative geometries of cavities and toolpath quality indicators, and reduces the milling time from 10% to 18% as compared to the PDE curvilinear spiral generation method proposed by Bieterman and Sandström. In addition, the proposed method is suitable for any non-convex pocket, with or without island(s).

Tool path generation with a uniform residual error distribution considering tool contour error for ultra-precision diamond turning

Tool path generation strategy plays a crucial role in improving the efficiency and surface quality of ultra-precision diamond turning mainly by influencing residual errors. However, current approaches in tool path generation have not achieved a uniform distribution of residual error due to the unexplored and significant impact of tool contour error on residual error. Therefore, this study introduces a novel tool path generation algorithm for ultra-precision diamond turning, aiming for a uniform residual error distribution with consideration of tool contour error. The tool contour is measured off-machine, fitted, and modeled to achieve its actual cutting-edge contour at a submicron scale. An estimation model is established to calculate residual error on the machined surface considering the tool contour error. A tool path generation approach is then proposed to achieve uniform residual error distribution by adaptively controlling stepovers. Then the proposed stepover is smoothed by cubic Hermite polynomial interpolation to avoid undesired tool path fluctuations. To further improve the machining accuracy, a spiral tool path is generated with proper discretization parameters to control chord error. Finally, a prototype software system is developed to optimize the tool path as well as predict the residual and machining error across the entire machined surface. Experiment results demonstrate a significant reduction of approximately 40 % in both residual error and machining error compared to unoptimized results.

Formability investigation of perforated austenitic SS 304L sheets using SPIF

Incremental sheet forming (ISF) is a progressive and highly flexible method of producing sheet metallic components in batches of limited quantities. It is also used for making prototypes at a low cost. Advantages of ISF are: higher sheet formability; elimination of molds and dies or use of simple molds and dies; formed parts with a good surface finish; use of commonly available vertical CNC milling machine and the possibility of quick changes in design. The low accuracy of formed parts and slow speed of the process are the disadvantages of ISF. Perforated metallic sheets have many applications in different industries because of their attractive display exposable to the atmospheric air and lighter weight than nonperforated metallic sheets. Its formability varies with the hole dimensions, ligament width, material chemistry, and forming parameters. In this paper, the effects of hole size, and other input parameters on the formability of the sheet are investigated. One millimeter thick SS 304L perforated sheets with 2 mm and 3 mm diameter holes are used for the present work. FLD and FLSD were drawn after performing the straight groove and wall angle tests. The highest formability was observed in the sheet with 2 mm diameter holes. XRD line profile analysis was done and correlated the formability with the crystallite size and dislocation density. SEM micrographs of fracture surfaces were taken and the fractographic parameters were correlated with formability. FE simulation was done using the optimized process parameters and the simulation results were compared with the experimental results. Contour and spiral tool path comparison was done numerically and experimentally.

Effect of Wall Angle on Thickness Distribution in Single Point Incremental Forming: Finite Element Analysis and Theoretical Approach

The incremental sheet forming process (ISF) is the emerging forming process in the small size product manufacturing industries where as embossing, stamping, coining operations can be used to produce a product in large quantity. Therefore, ISF is one of the best solution to decrease the cost of production when a small quantity of product is demanded. In present study Efforts are devoted to study the effect of wall angle on sheet thinning, reaction forces, reaction moments, etc. for truncated cone of aluminium alloy (AA1050) using Finite Element simulation. Initially, A MATLAB code was written for spiral tool path. Modeling and simulation was done in ABAQUS software. Thereafter, a theoretical sheet thickness was computed using sine law and it was found out to be in close agreement with simulated sheet thickness.

Roughness Test of Aluminum A5052 before and after Forming by SPIF Process

Single point incremental forming process, which is also known as SPIF, that forms from one direction. SPIF process was used for milling an aluminum metallic sheet. In this paper, an aluminum (A5052) sheet was formed in a conical shape by the SPIF process. The A5052 sheet was deformed by the computer numerical control (CNC) technology in the T60 series milling machine. The conical shape was deformed by the spiral toolpath in the T60 series milling machine. At the surface of the A5052, lubricant grease was continuously applied manually for reducing the friction generated due to milling. Also, for decreasing the tool rotational force friction on the A5052 sheet there was the use of lubricant. Moreover, 0.1mm step-down is used for the tool path because it takes more time for forming a metallic sheet, however, it deformed the sheet smoothly. The 0.5mm step-down g-code was extracted from fusion 360. Then the metallic sheet A5052 surface was compared before and after deformation. For testing a metallic sheet A5052 the formability parameter was analyzed in the experiment part. The experiment was performed to find the optimal smooth surface from the CNC milling machine. The initial roughness value and the microscopic image were presented in the investigational part. Likewise, the comparison of points for the highest and lowest rough point was further discussed and compared throughout the experiment.

Modified tool radius compensation in the Archimedes' spiral tool path for high speed machining of circular geometry

A key role in HSM (High Speed Machining) is played by the NC program code, which guides the tool along a programmed path without jumps in velocity and acceleration. The commonly used CAM (Computer Aided Manufacturing) software offers many operations for dynamic machining, but the generated code is difficult to edit. An alternative is to use parameterized technology cycles. Unfortunately, the circular pocket cycle available on the Siemens Sinumerik 840D controller was not designed for HSM machining. The purpose of the article is to program an Archimedes' spiral using modified tool radius compensation. The parametric NC code was implemented on the Siemens Sinumerik 840D controller as a technology cycle. The obtained trajectory of the tool meets the curvature continuity condition (C2 continuity). The algorithm uses 3 NC program blocks to define the spiral, regardless of its length. Tool positions are calculated directly by the interpolator during the tool's circular motion (G2/G3). Spiral step is achieved by an additional contour offset (OFFN function), and also by multiple repetitions of circles (TURN function). The change in the effective tool radius value during active tool radius compensation (G41/G42) moves the tool away from the contour along the length of the entire NC block. Several spiral programming variants that are used in cycles were analyzed to identify the feed rate drops at joining points between program blocks. During the process, the trajectory and feed rate were recorded using the Sinumerik Trace function. A problem with the Siemens Sinumerik controller was identified when machine axes exceed the acceleration limit. Synchronized actions were implemented to reduce the feed rate, with the acceleration and jerk limit that are specified in the part program being taken into account. The presented cycle, with the graphical user interface, highlights the potential for HSM milling. The conducted experiment shows the need to supplement the Siemens Sinumerik controller with Archimedes' spiral interpolation. New technology cycles will increase productivity and open up new possibilities, such as tapered threads milling.

Surface profile prediction modeling of spiral toolpath for axial ultrasonic vibration-assisted polishing

Hard and brittle materials are widely used in many frontier fields because of their better properties, and their efficient precision polishing methods are attracting much attention. The research on surface quality of optical lenses with surface finishing requirement not only involves surface roughness, but also surface form accuracy. The generated surface profile is a key factor affecting the surface form accuracy and overall smoothness. From experience, both processing mechanism of adopted method and toolpath have effects on the generated surface profile. For this, the paper presents a theoretical and experimental study of the generated surface profile of spiral toolpath in axial ultrasonic vibration-assisted polishing (UVAP). Based on classical Preston equation, Hertzian contact theory and the axial vibration-assisted processing principle, a prediction calculation model for generated surface profile of spiral toolpath is proposed. The model can specifically analyze the dwell-time distribution characteristics of periodically varying contact pressure and sliding velocity in the areas near/far-from the curvature center of curve toolpath, accurately predict the surface profile shape and material removal rate (MRR), and scientifically reveal the assisted processing principle. Accordingly, a series of experiments are conducted to verify the rationality of the proposed model and the polishing performance of axial UVAP. Compared to conventional methods, the predictions can more reasonably and accurately present the real surface profile characteristics, both high MRR and superior surface quality are obtained. This study would aid in achieving a deterministic processing technology of higher efficiency and better surface quality, laying a crucial theoretical basis for the global polishing of optical lens.

Stability analysis of pocket machining with the spiral tool path using the discontinuous Galerkin method

Pocket machining is widely used in the aerospace and automotive industries. The spiral tool path ensures smooth and consistent pocket machining. However, high-efficiency pocket machining places great demand for the stability of the milling processes. In this paper, the mechanics and dynamics of pocket machining along the spiral tool path are modeled, and a time-domain method is proposed to predict the stability of pocket machining in the framework of the discontinuous Galerkin method (DGM). The mechanics of pocket machining is modeled on the basis of computing the varying cutter-workpiece engagement. The cutting forces are predicted and experimentally verified. Further, the dynamic model of pocket machining is established and the stability of the pocket machining process is predicted with the stability lobes of representative feed directions along the spiral tool path. The DGM based time-domain method is proposed to improve the computational accuracy and efficiency of the stability analysis. The predicted stability of pocket machining along the spiral tool path is validated by the experimental results.

Research on deposition toolpath planning and laser head Z-axis rising height setting for directed energy deposition

In this study, the biggest goal was using laser directed energy deposition (L-DED) process to fabricate a solid blade part. In the process of CAD modeling, a blade model was built by sweeping a blade cross-section and twisting 10° simultaneously, which made it to have overhanging and tilting features. So, to select an appropriate deposition toolpath was the most important thing. The deposition toolpath in this study was decomposed into contour and field toolpaths. First of all, a cuboid part model of which the geometry was simpler was created to test toolpath planning approaches. The results recommended to use “Fixed rising height per layer with proper laser head rising height (Z-offset setting)” or “Spiral” approaches to plan contour toolpaths. For field toolpaths, “Reciprocating zigzag” planning approach was suggested and it needed to adjust the cladding angle to fit the cross-section of the parts. According to the test results of cuboid part fabrications, the contour of the target blade part was successfully manufactured with a 50% Z-offset setting and the spiral toolpath. The solid blade fabrication was also finished with a fixed rising height per layer with a 50% Z-offset setting and 45° reciprocating zigzag toolpath. In addition, the relationship between the Z-offset setting and the dilution was investigated through experiments. A conjecture that a height shrinkage of an old layer caused by thermal deformation is equal to the single-layer deposition dilution was proposed. Based on this conjecture, users can improve L-DED deposition results by setting the Z-offset as “the product of single-track height and the degree of shrinkage of an old layer height.” By combining the predictive value of dilution surface fitting model with the conjecture, it can be easier to get better LDED deposition quality.

Spiral tool path optimization method for fast/slow tool servo-assisted diamond turning of freeform surfaces with highly form accuracy

Spiral tool path generation methods for ultra-precision diamond turning of freeform surfaces can significantly affect form accuracy and machining efficiency. However, there is no previous research treating the tool path generation as a multi-objective optimization problem. In this study, a multi-objective optimization method for tool path generation based on a novel surface analysis model was proposed for the first time. In this method, spiral tool path generation methods were uniformly described on the basis of the newly established surface analysis model. The relation between cutting point sampling details and the resulting form error of freeform surfaces was analyzed and simulated. Then, corresponding fitness function and constraint function models were established, and the non-dominated sorting genetic algorithm (NSGA-II) was used to solve the path optimization problem to obtain the pareto optimal solution of the cutting point sampling parameters. Next, based on the optimization results of tool path, machining simulations with experimental parameters were performed to evaluate the quality of optimized tool path. To demonstrate the effectiveness of the proposed method, turning tests of near-rotational freeform surfaces were attempted on single-crystal germanium using the optimization method and the measurement results demonstrated that the optimized tool path can achieve sub-micron form accuracy, which further verified the effectiveness of the proposed optimization method. The proposed optimization method has been further applied in the machining of larger diameter freeform optics.

Toolpath generation for ultraprecision machining: Freeform surface generation and extrapolation

The rise in complexity of freeform optics drives the development of equally complex manufacturing processes needed to produce them. Complex optical designs, however, require equally complex machining toolpaths and techniques that can generate them. This paper and subsequent research develops and investigates toolpath generation techniques for explicitly defined surfaces of the form Z(X,Y). A generalized approach is developed for the toolpath generation of optical surfaces themselves as well as techniques for transitioning between surfaces in an array. All surfaces herein are continuous, well-behaved, and differentiable – constraints satisfied by most optical prescriptions today. The current paper describes the toolpath generation and extrapolation process for a tilted freeform surface defined inside a non-circular boundary. Boundaries are defined so that some non-convexity is acceptable, and it is simple to determine whether a toolpath coordinate lies inside or outside them. Using the proposed coordinate frame transformation and boundary definition, it is shown that by tilting a surface and boundary together, the tilted surface retains its original form and boundary in a rotated coordinate frame. With the proposed extrapolating surface, it is possible to modify a freeform surface outside its defined boundary so it is smooth and well-behaved inside its overall region of interest – an important consideration for both toolpath generation and opto-mechanical design. By combining freeform and extrapolating surfaces together, a smooth piecewise surface is generated whose overall continuity increases as the order of the extrapolating surface increases. As a result, it is possible to increase the overall continuity of a toolpath along its cutting direction. To verify the utility of the proposed extrapolating surface, experimental data are presented for several spiral toolpaths generated for a 6th order polynomial surface prescription defined inside a rectangular boundary. Subsequent research, using the techniques herein as a starting point, develop and investigate blending multiple freeform surfaces together.

Fabrication of high aspect-ratio aspheric microlens array based on local spiral diamond milling

Ultraprecision mold machining combined with precision glass molding is the most promising technology for the mass production of glass microlens arrays (MLAs). However, fabricating an MLA with a high aspect-ratio (AR) (ratio of height to aperture), submicron scale profile accuracy, nanoscale surface finish, and good consistency remains a considerable challenge. A local spiral diamond milling (LSDM) method is proposed to generate a high AR MLA on a nickel-phosphorous (Ni-P) plated mold. A spiral toolpath generation algorithm that considers the tool edge radius and performs profile error (PV) compensation is developed. Each lenslet at any local position can be precisely machined by controlling the servo motions of the three translational axes. Then, the entire MLA can be generated by shifting the toolpath to go through the centers of all lenslets according to the MLA layout. The tool parameters are optimized to avoid local and global tool interference during machining. The generated toolpath provides steady slide axis movements to avoid dramatic changes in cutting speed and acceleration. An MLA with an AR of 0.166 is fabricated. The results show that the fabricated mold and the molded lenses have a profile accuracy (PV) of less than 1 μm and a surface roughness (Ra) of less than 14 nm. The cross-sectional profiles indicate that the fabricated MLA has high machining consistency.

Numerical investigation of the influence of process parameters and tool path on the temperature in the laser glass deposition (LGD) process

Additive manufacturing has gained interest in the industry due to its flexibility in design and the possibility to integrate functionalities. Thereby, glass has a high potential to be developed also in this field due to its thermal stability, chemical resistance, and optical transmission. Laser glass deposition is a method for fabricating glass components on a glass substrate. The energy input and the resulting temperature are crucial factors in this process, which can influence the material properties and the resulting geometry. Also, depending on the temperature in the substrate, difficulties such as high residual stresses or thermal shock can occur. The temperature on the glass substrate and in the melt zone can be changed either directly by the laser power or laser spot size, or indirectly by other process variables such as travel speed or path planning strategy. In this study, the energy input and the resulting temperature in the melt zone are numerically investigated under selected process parameters. Based on this, a regression function was created so that the generated temperature can be calculated by corresponding laser power, laser spot diameter, and axis velocity. Moreover, different tool path strategies for the production of horizontally multilayered surfaces were thermally investigated. The results showed a more uniform temperature profile with zigzag movement than the spiral tool path. The influence of the turning point angle in path planning on the temperature change was also investigated. It was observed that the 90° corner in contrast to the smaller angle has no significant influence on the temperature change.

Numerical study on the effect of oscillation on the deformation behavior of single point incremental formed part

The paper reports the deformation behavior of single point incremental formed part with sheet oscillation. Single point incremental forming is an emerging manufacturing technology. This technology provides the competition to the other innovative technologies such as electric-assisted manufacturing, hydroforming, high-speed forming, etc., to produce the lightweight and highly deformed components. Single point incremental forming is the die-less sheet metal forming process in which the single point tool incrementally forces any single point of sheet metal at any processing time to undergo plastic deformation. In single point incremental forming, the part stays fixed and the tool pin makes the planar and downward motion to shape the part. It has several advantages over the conventional process such as high process flexibility, elimination of die, complex shape, and better formability. Previous literature provides enormous research on the formability of metal during this process, process with various metals and hybrid metals, the influence of various process parameters, but research on the deformation behavior of the part through the oscillation of the tool was limited. In this paper, the single point incremental forming was simulated on ABAQUS finite-element software. The spiral tool path was studied. First, the part was formed without oscillation. Then the oscillation of the sheet with the help of a die and blank holder was set with a frequency to deform the part. The variation of frequency and amplitude was also studied. The formability of the part was analyzed and compared. The deformation, profile shape, strain path, thickness, and force requirement were analyzed and presented. It was found that with lower cycles the maximum stress increases with an increase in amplitude. Also, with an increase in the number of cycles the achieved strain values were lower as compared to the no oscillation case for the same cup height and thus higher deformation is possible with oscillation.

Automatic generation of 3d spiral tool path for incremental sheet metal forming of mechanical parts with complex geometry

Incremental sheet metal forming is a flexible manufacturing technology that allows to form of various components on the same milling machine, without expensive tools. A hemispherical tool moves along a CNC-controlled tool path and deforms the sheet into the desired shape. The tool path has a significant role in the geometric accuracy of the final part. There has been very little research on the problem of the forming of sophisticated parts with asymmetric wall angles. This paper presents a new approach to generating optimized tool paths for single-point incremental sheet forming (SPIF). At first, a strategy is proposed for the automatic generation of a 3D tool path during forming in a single-step operation. Then, a systematic technique of creating intermediate shapes is investigated by defining tool paths interpolated from the final part shape. The proposed methodology is applied to form a hip cup prosthesis. This part has a complex asymmetric geometry with important angles, a multi-step approach is used. The proposed methodology to define the different tool paths was implemented in Matlab. A numerical simulation of the incremental forming process is performed to predict the final geometry of the aluminum sheet. A comparison of desired and predicted geometries shows the reliability of the proposed method.

Research on the Influence of the Pitch of the Spiral Toolpath on the Forming Quality of Single Point Increment Forming

In order to study the influence of the pitch of the spiral toolpath on the forming quality in the single-point incremental forming, three kinds of spiral toolpath with pitch of 0.2 mm, 0.5 mm and 1 mm were generated by using the UG software, and the thickness distribution, contour dimensional accuracy and equivalent stress of the formed parts based on the spiral toolpath with the three kinds of pitch were compared and analyzed through numerical simulation by using the ANSYS/LS-DYNA software. The research result show that the smaller the pitch of the spiral toolpath, the better the forming quality of the formed part.

Dynamic rotating-tool turning of micro lens arrays

Diamond micro milling of high-quality micro lens arrays suffers from low machining efficiency, due to the inevitable milling marks along tangential feed direction and the slow spiral tool path interpolated by multiple linear axes. In this article, an advanced cutting process is proposed, namely dynamic rotating-tool (DRT) turning, in which a U-axis attachment on a rotary stage is developed to enable synchronous cutter rotation and radial feed motions of a diamond turning tool. This method is experimentally verified and compared with milling, with significantly enhanced surface quality and machining efficiency, thus bringing a new perspective into ultra-precision machining.

A smooth tool path generation method for ultraprecision turning discontinuous multi-freeform-surfaces with high machining efficiency

The typical tool path of turning freeform surfaces is spiral. Usually, this kind of tool path only can deal with continuous surfaces within a circular area. If the designed surfaces are not continuous, the spiral tool path will break, which will lead to a significant increase in servo following error of ultraprecision lathe during machining. In order to reduce the servo following error, the processing speed needs to be significantly reduced, which will greatly decrease the machining efficiency. To solve this problem, a smooth tool path interpolation algorithm in the non-cutting area for ultraprecision turning discontinuous multi-freeform-surfaces is proposed. In addition, more than circular area, this method can generate smooth tool paths for discontinuous generic surfaces of quasi-revolution based on the optimized space Archimedean spiral. Finally, the effectiveness and adaptability of the method are proved through two examples.

Adaptive spiral tool path generation for computer numerical control machining using point cloud

This paper reports a novel method to generate adaptive spiral tool path for the CNC machining of complex sculptured surface represented in the form of cloud of points without the need for surface fitting. The algorithm initially uses uniform 2 D circular mesh-grid to compute the cutter location (CL) points by applying the tool inverse offset method (IOM). These CL points are refined adaptively till the surface form errors converge below the prescribed tolerance limits in both circumferential and radial directions. They are further refined to eliminate the redundancy in machining and generate optimum region wise tool path to minimize the tool lifts. The NC part programs generated by our algorithm were widely tested for different case studies using the commercial CNC simulator as well as by the actual machining trial. Finally, a comparative study was done between our developed system and the commercial CAM software. The results showed that our system is more efficient and robust in terms of the obtained surface quality, productivity, and memory requirement.