Tool Radius Research Articles

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.

Modeling the strain localization of shell elements subjected to combined stretch–bend loads: Application on automotive sheet metal stamping simulations

This study presents a modeling approach for predicting strain localization during sheet metal stamping processes focused on automotive engineering applications. The so-called stretching-to-bending ratio, ρ, is proposed to characterize the loading conditions acting on an element during stamping processes. Then, localized strain or necking strain is suggested to be a function of ρ. Different stretch–bending tests with different tool radii, i.e., R3, R6, R10, and R50 are conducted for two automotive sheet metals, DP800 and AA6010, to identify their forming limits under combined stretch–bend loads. The calibrated necking limit curve of the AA6016 sheet is then employed in AutoForm R10 software to predict the necking and failure of a stamped panel. Agreement with the experimental observation of failure positions of the panel validates the usefulness of the proposed modeling approach in practice.

On the Springback and Load in Three-Point Air Bending of the AW-2024 Aluminium Alloy Sheet with AW-1050A Aluminium Cladding.

This article presents the results of an analysis of the bending load characteristics and the springback phenomenon occurring during three-point bending of 1.0 and 2.0 mm thick AW-2024 aluminium alloy sheets with rolled AW-1050A cladding. A new proprietary equation was proposed for determining the bending angle as a function of deflection, which takes into account the influence of the tool radius and the sheet thickness. The experimentally determined springback and bending load characteristics were compared with the results of numerical modelling using different models: Model I, a 2D model for a plane deformation state, disregarding the material properties of the clad layers; Model II, a 2D model for a plane deformation state, taking into account the material properties of the cladding layers; Model III, a 3D shell model with the Huber-von Mises isotropic plasticity condition; Model IV, a 3D shell model with the Hill anisotropic plasticity condition; and Model V, a 3D shell model with the Barlat anisotropic plasticity condition. The effectiveness of these five tested FEM models in predicting the bending load and springback characteristics was demonstrated. Model II was the most effective in predicting bending load, while Model III was the most effective in predicting the amount of springback after bending.

On the Utility of the Thermal-Pseudo Mechanical Model’s Residual Stress Prediction Capability for the Development of Friction Stir Processing

This paper investigates the thermal-pseudo mechanical (TPM) model’s residual stress prediction capability for its utility in developing friction stir processing (FSP). Specifically, two FSP tests under different processing conditions were conducted, and the corresponding simulations were carried out to verify if the TPM model can predict residual stresses for various tool radii and workpiece materials. The model successfully predicted residual stresses with an error less than 4% for one of the tests but failed to work for the other test. Further simulations under different FSP conditions proved that the TPM model works for cast aluminum alloys and wrought aluminum alloys. In addition, the large FSP tool used was found to be the reason for the model’s failure on one of the tests. This indicates that there is a range of tool radii for which the TPM model is applicable. As a solution, this paper suggests modifications to the TPM model based on calibration to the FSP test temperatures. The resulting residual stress prediction is accurate and differs from the experimentally characterized stress values by only 6.5 MPa. The calibrated TPM model requires FSP to be carried out when using a tool with a different radius. Following that, the effect on residual stresses due to changes in the other process parameters, such as the tool traverse & rotation speeds and the clamping conditions, can be predicted.

Effect of edge radius on forces, tool wear and surface integrity under edge radius dominated tool-chip contact conditions

Cutting-edge micro-geometry is a crucial factor influencing chip formation and tool performance. This paper investigates the effects of varying cutting edge radius (36–70 µm) on machinability and chip morphology during finish turning Ti6Al4V. An increase in edge radius decreases the cutting to thrust force ratio and produces lower chip thickness due to the increase in plowing zone depth. The machining temperature for the 48 and 52 µm edge radius tools is lower compared to all other tools. At the initial stage, the edge prepared tools exhibit larger flank wear, whereas subsequent flank wears progression is slower for the prepared tools as compared to the sharp tool. BUE and premature chipping is reduced for larger edge radius tool due to better edge stability provided by cutting edge preparation. Beyond the 59 µm edge radius, the process force, machining temperature, tool wear, and surface roughness increased steeply due to the increase in the size of the plowing zone. In addition to cutting force and machining temperature data, surface roughness, tool wear measurements and XRD analysis show that a radius range of 50–55 µm results in optimum performance for finish turning Ti6Al4V.

Towards modeling and restraining surface ripples during bonnet polishing based on frequency domain characteristic control

Extensive research has been conducted on Bonnet polishing for its ability to manufacture freeform surfaces with nano-scale precision. However, surface ripples are easy to introduce under regular motion, and the underlying principle to address this problem remains unclear. In this study, a novel methodology based on frequency domain characterization is proposed, connecting the spatial process parameters and frequency domain evaluation index directly. Bessel function and single pulse convolution are introduced for model establishment. Tool radius, tool tilt angle, and contact radius are correlated with surface ripple mitigation. Polishing parameters optimization case study was conducted and verified using self-designed polishing robot.

New Concept of External and Independent Next-to-the-Scope Intraluminal Grasping Device (EINTS).

Background: Interventional endoscopic procedures require complex manipulations and precise maneuvering of end-effectors. One focus in research on improved endoscopic instrument function was based on surgical experience to gain additional traction. The idea has emerged using assisting instruments by applying external tools next-to-the endoscope to follow surgical concepts. The aim of this study is the assessment of flexible endoscopic grasping instruments regarding their function and working-radius introducing the concept of an intraluminal "next-to the-scope" endoscopic grasper. Methods: In this study endoscopic graspers are evaluated (1:through-the-scope-grasper, TTSG; 2:additional-working-channel-system AWC-S;3:external-independent-next-to-the-scope-grasper EINTS-G) regarding their working-radius, grasping abilities, maneuverability and the ability to expose tissue with varying angulation. Results: The working radius of the tools attached or within the endoscope (TTS-G and AWC-S) benefit from the steering abilities of the scope reaching 180-210 degrees in retroflexion; EINTS-G is limited to 110-degrees. The robust EINTS-grasper has the advantage of stronger grip for grasping and pulling force, which enables manipulation of larger objects. The independent maneuverability during ESD-dissection provides better tissue-exposure by changing the traction-angulation. Conclusion: The working radius of tools attached to the endoscope benefit from scope- steering. The EINTS-grasper has the advantage of stronger grasping force and pulling within the GI-tract and independent maneuverability enables improved tissue-exposure. WC200.

Numerical modeling considering initial gradient mechanical properties and experiment verification of residual stress distribution evolution of 12Cr2Ni4A steel generated by ultrasonic surface rolling

Ultrasonic surface rolling process is a promising surface strengthening technique which can improve the fatigue performance of metallic components by introducing reasonably compressive residual stress field. It is of great significance to accurately predict the residual stress distribution of parts in the simulation of ultrasonic surface rolling process. In this paper, a numerical model considering initial gradient mechanical properties (residual stress and micro-hardness) is proposed to predict the residual stress distribution of 12Cr2Ni4A carburized and quenched steel. Moreover, a method is proposed to calculate the ultrasonic surface rolling coverage based on Hertz contact theory, which can guide the optimization of process parameters. The effects of static load, rolling tool radius, amplitude and feed rate on residual stress distribution are investigated. The simulated results and measured results are compared and proved to be in good agreement, which validates the accuracy of the model proposed in this paper.

Micro-embossing of micro-structures in RSA-501 as mold inserts for the replication of micro-lens arrays

The production of mold inserts for the replication of micro-lens arrays through micro-embossing could be an alternative process route compared to diamond turning or milling in order to reduce time and costs. The rapidly solidified aluminum alloy RSA-501 is expected to form micro-structures with low surface roughness because of its ultra-fine grain structure. In micro-embossing challenges like elastic spring back effect, pile-ups, and forming accuracy depend on the material behavior. Therefore, RSA-501 was further characterized and the influence of polishing or flycutting on the material behavior was investigated. To further understand the grain and microstructure samples were sectioned along their cross and longitudinal directions. The grain structure of RSA-501 was oriented along the extrusion direction and the mean grain sizes were <1.00 μm. Furthermore, RSA-501 was micro-embossed to investigate the influence of the material behavior and surface preparation on the forming of micro-structures. The induced surface integrity through flycutting was not deep enough to influence the forming of micro-structures. Therefore, the workpiece surface can be prepared either by polishing or flycutting. When micro-embossing RSA-501, cross and longitudinal sections can be used. However, it is recommended to process the cross section because of its isotropic grain structure. It was shown that the curvature radius of micro-embossed concave structures differs from the tool radius. This is due to the elastic spring back effect. Since the embossed structure remains spherical, the spring back effect can be compensated by adjusting the tool radius.

Nano-to-microscale ductile-to-brittle transitions for edge cracking suppression in single-diamond grinding of lithium metasilicate/disilicate glass-ceramics

To suppress grinding-induced edge cracks in dental lithium metasilicate/disilicate glass-ceramics (LMGC/LDGC), this paper established a contact stress model for single-diamond grinding (SDG) to relate their crack generation and ductile-to-brittle transition (DBT) thresholds with the mechanical properties, diamond tool profiles and process variables. Nanoindentation, friction test and SDG were conducted to unravel material responses and dynamic diamond grit-workpiece interactions to determine the DBT thresholds. The nanoindentation revealed significant indentation size effects (ISEs) on the hardness and elastic moduli of the ceramics. SDG clearly elucidated their DBT behaviors, wherein edge cracks initiated at diamond peripheries when the concurrent contact stresses reached the DBT thresholds. Accordingly, the indicated critical cutting depths for DBT may be changed from the nanoscale to the microscale by increasing the tool radius and reducing the machining speed. This research contributes to edge crack suppression for ductile machining of brittle materials at large removal rates.

Accurate measurement of cutting-edge radius on a single-crystal diamond tool

Single-crystal diamond (SCD) tools are hard and can maintain a uniform sharp cutting edge and hence used in ultraprecision machining of optics. The tools typically have edge radii in the range of 10-100 nm. Direct measurement of the cutting-edge radius on the SCD tool accurately in the order of tens of nanometers using a scanning electron microscope (SEM) is not possible and arduous using an atomic force microscope (AFM). In this study, we have demonstrated a more accurate edge reversal technique to measure the SCD tool’s cutting-edge radius. A nano indent is made using the SCD tool on two polished pure copper blocks held together in a precise vise. After the nanoindentation, the copper blocks are separated, and the cross-section profile of the indentation mark, a replica of cutting-edge geometry, is observed in an SEM. A fitted circle on the indentation profile is used to obtain the edge radius. Due to the elastic recovery in the material, the indentation profile geometry changes slightly, and the radius measured from the SEM image is not the same as the actual tool radius of the SCD tool. We performed finite element method (FEM) simulations to quantify the amount of elastic recovery and calculate the elastic recovery factor for a given SCD tool geometry as a function of indentation depth and edge radius. From the simulation results, we found the error due to elastic recovery effect in edge radius measurement is only 10%. Due to the stick-slip condition and high stress concentration factor at the cutting edge of the tool, material pull-out is observed at the middle of the cutting mark on the substrate but at the ends of cutting mark on the substrate material was negligible. In this method, compared to the previous literature work the three primary sources of errors, elastic recovery effect, convolution effect of AFM tip, and material pull-out are eliminated. Hence, this method provides a more accurate measurement of the edge radius and can be adopted by research labs, universities, and industries having ultra-precision machining facilities without needing a special purpose SCD tool edge radius characterization facility.

Investigation of anode shaping process during co-rotating electrochemical machining of convex structure on inner surface

A novel co-rotating electrochemical machining method is proposed for fabricating convex structures on the inner surface of a revolving part. The electrodes motion and material removal method of co-rotating electrochemical machining are different from traditional electrochemical machining. An equivalent kinematic model is established to analyze the novel electrodes motion, since the anode and cathode rotate in the same direction while the cathode simultaneously feeds along the line of centres. According to the kinematic equations of the electrodes and Faraday’s law, a material removal model is established to simulate the evolution of the anode profile in co-rotating electrochemical machining. The simulation results indicate that the machining accuracy of the convex structure is strongly affected by the angular velocity ratio and the radius of the cathode tool. An increase of the angular velocity ratio can improve the machining accuracy of a convex structure. A small difference in the radius of the cathode tool will cause changes in the shape of the sidewalls of the convex structure. The width of the cathode window affects only the width of the convex structure and the inclination α of the sidewall. A relation between the width of the cathode window and the width of the convex structure was obtained. The formation process for a convex structure under electrochemical dissolution was revealed. Based on the simulation results, the optimal angular velocity ratio and cathode radius were selected for an experimental verification, and 12 convex structures were simultaneously fabricated on the inner surface of a thin-walled revolving part. The experimental results are in good agreement with the simulation results, which verifies the correctness of the theoretical analysis. Therefore, inner surface co-rotating electrochemical machining is an effective method for fabricating convex structures on the inner surface of a revolving part.

Multistage Deep-Drawing with Alternating Blank Draw-in for Springback Reduction in Transfer and Progressive Dies

Cold formed sheet metal parts made of advanced high-strength steels (AHSS) offer a high potential for a lightweight, durable and economic design. However, manufacturing dedicated, high-strength parts with cold forming technologies such as conventional deep-drawing often results in unacceptable shape deviations due to elastic springback after unloading the part from the forming tools. Therefore, various springback compensation methods have been established to ensure dimensional quality of such sheet metal parts. At the Institute for Metal Forming Technology (IFU Stuttgart), deep-drawing with alternating blank draw-in was developed in this context as a new approach to reduce springback and enhance cold forming of AHSS sheet metal parts. Presented work provides numerical sensitivity analysis as well as experimental studies about this new forming method. The asymmetric and alternating blank draw-in, which is changed within a multistage forming process sequence, results in an alternated bending over tool radii and leads to a beneficial stress superposition in the part wall area with reduced springback phenomena. Compared to conventional deep-drawn sheet metal components, springback of a benchmark part geometry could thus be reduced over 75 % by a three-stage forming process with an optimized blank draw-in kinematic.

The propagation of fibre–matrix interface debonding during CFRP edge milling process with the multi-teeth tool: A model analysis

The fibre–matrix interface debonding has been considered as one of unsatisfied defects during milling carbon fibre reinforced plastic (CFRP) by multi-teeth tool, which has a special character of propagation in subsurface that still needs to be clearly known. The present paper offered a new model based on beam bending theorem and data from correlated multiple-pass cutting process to precisely describe the mechanism behind such debonding propagation. The validity and accuracy of this model were certified by proposed evaluation methods in the way of experimental results analysis. It can be inferred from results discussion that feed rate and tool radius presented the linear and non-linear proportional relations to debonding degree respectively, but tool radius had a greater impact on variation in debonding degree than feed rate, which can be well described and predicted by such model. This work put a novelty view to further recognize the debonding behaviours during CFRP milling.

Failure analysis of AISI 430 stainless steel sheet under stretching and bending conditions

Ferritic stainless steels have been widely used to substitute austenitic steels because of their lower cost and higher deep drawing capacity. However, failures, such as shear fracture, have been observed in parts with small radii during the drawing process in applications where both bending and stretching occurs. Conventional techniques, such as failure criterion consideration, finite element method, and forming limit diagram, are unable to predict this type of fracture, which has hampered the development of new processes and products. To overcome this limitation, herein, we investigated the effects of tool radius, direction, and test speed on the formability to fracture of an AISI 430 stainless steel sheet under bending and stretching conditions. An equipment was used to perform the draw-bend fracture (DBF) test based on the bending under tension test. The DBF test efficiently reproduced the tensile, mixed, and shear fractures. Furthermore, we determined the fracture limit strain on the outer surface, thickness, and sidewall of the sample, as well as the coefficient of friction. The data showed that the radius to thickness ratio related to the process parameters had a direct impact on the experimental results. In addition, the results can be utilized for setting design guidelines and failure prevention.

Molecular Dynamics Simulation of Chip Morphology in Nanogrinding of Monocrystalline Nickel

In this study, the nanogrinding process for single-crystal nickel was investigated using a molecular dynamics simulation. A series of simulations were conducted with different tool radii and grinding methods to explore the effects of chip morphology, friction forces, subsurface damage, and defect evolution on the nanogrinding process. The results demonstrate that the workpiece atoms at the back of the tool were affected by the forward stretching and upward elastic recovery when no chips were produced. Although the machining depth was the smallest, the normal force was the largest, and dislocation entanglement was formed. The small number of defect atoms indicates that the extent of subsurface damage was minimal. Moreover, when spherical chips were produced, a typical columnar defect was generated. The displacement vector of the chip atoms aligned with the machining direction and as the chips were removed by extrusion, the crystal structure of the chip atoms disintegrated, resulting in severe subsurface damage. By contrast, when strip chips were produced, the displacement vector of the chip atoms deviated from the substrate, dislocation blocks were formed at the initial stage of machining, and the rebound-to-depth ratio of the machined surface was the smallest.

Surface topography in single-point diamond turning of image slicers

We proposed a model to estimate surface topography and transition edge width in diamond-turned non-circular compound freeform optics featuring right angle transitions. The method serves as comparison basis between both full and split radius tools and takes into consideration basic cutting and tooling parameters relevant to a raster tool path, along with multiple variables, such as material response and defects, tool wear, and spindle vibrations. Principles are applied to a set of adjacent rectangular surfaces of different tilts. Fabrication tests validating the model show good agreement between the proposed calculations and the experimental results and offer insight on how and when both tip geometries should be used. We represent a useful asset for optical engineers who want to determine which diamond tips choose for their freeform applications. It can also be employed to assess the attainable surface quality and width of edge transitions in compound freeform designs before manufacturing them.

Effect of cutting edge radius on end milling Ti–6Al–4V under minimum quantity cooling lubrication – Chip morphology and surface integrity study

The effect of cutting edge radius (30–55 μm) during milling Ti–6Al–4V under minimum quantity cooling lubrication (MQCL) conditions is studied. A trial study is conducted to compare the performance of dry, wet, and MQCL using unprepared tools with edge radius of 30 μm alone. Subsequently, inserts having initial radius of 30 μm are prepared to 40–55 μm radius using drag finishing and milling of Ti–6Al–4V under MQCL is studied for different edge radii. Rounded edge tools are found to produce thinner and more curvilinear chips resulting in easier chip removal from the machining zone. The chip thickness and curl radius were up to 54% and 47% lower for the larger edge radius tools as compared to the 30 μm edge radius tool. This improves the penetration of the MQCL aerosol jet into the cutting zone thus producing better tribological results. The better penetration of MQCL aerosol into the cutting zone for larger edge radius tools results in lowering the resultant process forces (up to 16%), tool-chip interface temperature (15%), tool wear (40%) and surface roughness (30%) for the 48 μm radius tool as compared to the unprepared (30 μm) tool. There is deterioration in process forces, tool wear and surface integrity for the 55 μm tool possibly suggesting the existence of an optimum edge radius closer to 48 μm.

Atomistic understanding of the subsurface damage mechanism of silicon (100) during the secondary nano-scratching processing

Ultra-precision grinding is a fundamental machining method as for silicon. In grinding, abrasive particles repetitively scratch on the workpiece surface, and the subsurface damage caused by the initial scratching exerts a remarkable effect on the subsequent processing. Nonetheless, the previous researches regarding the subsurface damage mechanism of silicon ignore the influence caused by the initial scratching. Herein, a damage model was constructed via the initial scratching method, and the influence mechanism of the secondary nano-scratching on the subsurface damage of silicon substrate under different scratching parameters was explored utilizing molecular dynamics simulation. The simulation results show that the dominating removal part under secondary scratching is the amorphous layer induced by the initial scratching, and the secondary scratching without feed can effectively remove prefabrication subsurface damage. The larger scratching depth and tool radius could lead to the increasement of scratching force and scratching temperature so as to increase the thickness of subsurface damage layer. Moreover, the high pressure generated by the collision between the abrasive particles and the substrate will induce the amorphous phase transformation. This study provides a new insight into the mechanism and evolution of subsurface damage during grinding process of silicon from an atomic perspective.

A comparative study of NaOH and KOH electrolytes in micro-ECM

ABSTRACT Tungsten microtool electrode is one of the preferred tool electrodes in micro electrochemical machining (µECM) of hard to machine materials. During the pilot experiments with different types of electrolytes materials (such as NaOH, HNO3, NaBr, KOH, H2SO4, NaCl, NaNO3 and HCl), it has been found that KOH(Aq.) and NaOH(Aq.) electrolytes are suitable for the fabrication of tungsten microtools through µECM process. Therefore in this research, a comparative study between NaOH(Aq.) and KOH(Aq.) electrolytes have been carried out in the fabrication of tungsten microtools through µECM. DC voltage (V), electrolyte concentration (Mol/L) and machining time (Minutes) are chosen as machining parameters in order to investigate their role on response outputs i.e. tool radius reduction (Δ) and material removal rate (MRR). Roles of machining parameters on the response output are analysed through Taguchi design technique and ANOVA is employed to determine the dominant machining parameters on the response outputs. Experimental results indicate ‘Δ’ and ‘MRR’ obtained with NaOH(Aq.) is greater than ‘Δ’ and ‘MRR’ obtained with KOH(Aq.) respectively at most of the experimental run. But microscopic view of the fabricated microtools indicate that the surface uniformity throughout the length of the microtools obtained with KOH(Aq.) electrolyte is favourable than NaOH(Aq.).