Tool Deflection Research Articles

Tool deflection investigation and deflection compensation of drill thread milling

Tool deflection investigation and deflection compensation of drill thread milling

Novel processing of micro-channels in micro-grinding with automated laser-assistance

AbstractMicro-structures are widely utilized in various fields such as optical, medical, defense, and aerospace. The accuracy and performance of micro-structures depend on fabrication methods, including conventional and non-conventional machining. High-quality micro-channel fabrication is challenging by conventional micro-grinding (CMG) which uses a micro-pencil grinding tool during micro-machining. However, in CMG, high-cutting forces act in the machining zone leading to tool deflection, tool failure, high temperature, and poor surface finish. The challenges of CMG can be overcome by using automated laser-assisted micro-grinding (LAMG), one of the modern micro-machining processes for fabricating high-quality, precise micro-channels. The novel processing of micro-channels in this work is through the in tandem use of LAMG and CMG. In this, the laser structuring is performed using LAMG followed by a micro-pencil grinding tool processing in a sequential manner on a same machine tool to achive high-quality parts and accuracy. This helps in fabrication of a micro-channel directly in one go without the need to remove the part to perform the two operations on two different machining setups, thereby reducing systematic fixturing errors which are significant when we are working at the micro-scale. This paper thus investigates the effect of various parameters viz. laser input energy densities and laser power on cutting forces and surface roughness on the tool as well as the work surface with two distinct scan patterns. In LAMG, at lower laser input energy density (pattern 1), the tangential and normal forces decreased by 10.3% and 20.5%, and surface roughness Sa and Sq reduced by 24% and 22% compared to CMG. Similarly, a normal force decreased by 20.5% in pattern 1 and 38% less in pattern 2. Still, the higher laser energy density (pattern 2) is unsuitable for structure due to an increase in Sa and Sq by 11% and 14.6%, respectively. Results have shown a maximum reduction in the normal and tangential force magnitude by 31 and 44% at 25 W compared to CMG. The work concludes that LAMG with novel laser assistance scan patterns has lower dynamic deflections resulting in better dimensional accuracy and surface finish compared to CMG with a lower tool.

Reforming toolpath effect on deformation mechanics in double-sided incremental forming

Incremental sheet metal forming is a die-less process known for its high flexibility, making it a suitable choice for fabricating low-batch, highly customized complex parts. In this paper, the deformation mechanism of double-sided incremental forming (DSIF) with single pass or reforming toolpaths and its effect on the deformation-induced martensite transformation kinetics are investigated by experiments and finite element (FE) simulations for a truncated pyramid part geometry for the first time. An FE model accounting for tool deflection is developed, considering the change in tools' position caused by the forces applied at the contact with the blank. This is done to enhance the simulation accuracy in comparison to experimental results. A comprehensive analysis is conducted with respect to the stress state change and strain accumulation during DSIF with the single pass and reforming toolpaths. The findings reveal that material points along the pyramid wall primarily deform by a combination of plane strain tension, plane strain compression, and shear, depending on the tools’ locations on the sheet surfaces in relation to the material point of interest. The reversal of the forming direction in the reforming toolpath causes material points to experience different stress states and more strain accumulation than the single pass case. Under the same forming temperature, this phenomenon results in a higher and closer martensite transformation on both forming and supporting surfaces of the final part when employing the reforming toolpath as opposed to the single pass case.

Active runout compensation using the guide elements on metal band saws for a longer tool life and reduced material loss

AbstractAt a time of rising energy and material costs, manufacturing process efficiency is becoming increasingly important. This is one reason why cutting and especially sawing processes, usually the first step in most manufacturing chains in discrete part production, have to be investigated more intensively. Due to problems with runout and poor surface finishes, raw material is conventionally cut to oversize by either circular sawing or band sawing. This oversize has to be removed by following processes, costing extra energy and wasting material. Since the problem of runout increases with increasing tool wear due to higher deflections of the thin and compliant tools, an even larger oversize is required. This paper describes an approach to reduce the need of oversize even with increasing tool wear in band sawing by tilting the saw band in order to compensate for tool deflections during cutting. To achieve this, it is necessary to measure and understand the saw band runout. The next step is to present a system design and controller for tilting the saw band. Finally, tests are carried out to analyse the effectiveness of the system. In addition, the approach allows the use of increased process parameters to the end of the tool life without losing more material. The tool can therefore be used productively for a longer time period.

Performance evaluation in die-sinking EDM of polygonal micro cavities over EN-24 alloy steel using cylindrical electrode and polygon cycle approach

The integration of advanced Electrical Discharge Machining (EDM) technology, incorporating short and electronically pulsed discharges with precise circular electrode movements, has enabled the production of intricate 3D microstructures and cavities. This paper aims to investigate the machining performance of polygonal cavities—triangular, square, pentagon, and hexagon—fabricated on steel samples using a 400 µm cylindrical copper electrode within the polygon cycle approach of EDM. Experimental investigations were conducted to assess shape error, tool wear rate, recast layer formation, and elemental characterization. Various discharge patterns and side discharges were examined to understand their effects on spark gap uniformity, tool deflection, and discharge stability. The results revealed non-uniform spark gaps, tool deflection, and corner rounding due to varying discharge patterns and side discharges. Tool wear rate was found to be directly related to polygon complexity, with higher-order polygons leading to increased wear due to extended machining durations and heat accumulation. The maximum tool wear of 7.69 × 104 µm3/s occurred in case of hexagonal cavities while in case of triangular cavities, the tool wear rate was minimum having value of 5.77 × 104 µm3/s. Scanning Electron Microscopy (SEM) examinations showed the presence of recast layers and micro-cracks, particularly in cavities with higher shape complexities. Energy Dispersive X-ray Spectroscopy (EDS) analysis identified copper deposition, local material evaporation, and foreign element accumulation on the cavity surfaces. This study provides insights into the machining performance of polygonal cavities in EDM processes. The findings underscore the influence of discharge patterns, polygon complexity, and material interactions on tool wear, surface quality, and microstructure integrity. Understanding these factors can inform optimization strategies for EDM processes, leading to enhanced precision and efficiency in microstructure fabrication.

Cylinder accuracy analysis of tangential turning of disk-like workpieces with increased cutting speed

Tangential turning, a precision high-speed finishing procedure, is crucial for achieving superior surface quality and dimensional accuracy in cylindrical workpieces. This advanced machining technique leverages tangentially applied cutting forces to minimize tool deflection and vibration, thereby enhancing the surface integrity of the final product. Despite its advantages, tangential turning poses challenges in maintaining cylindrical accuracy, necessitating a thorough investigation of cylindrical error. Cylindrical error, the deviation of the machined surface from a perfect cylinder, significantly impacts the functional performance of precision components. Factors such as tool wear, machine dynamics, and thermal effects can induce these errors, demanding comprehensive studies to optimize process parameters and tool paths. By thoroughly analyzing cylindrical error, manufacturers can refine tangential turning processes, ensuring high precision and consistency in high-speed finishing operations. This research underscores the importance of precision error analysis in advancing manufacturing capabilities and achieving stringent quality standards. Cylindrical accuracy is analyzed using the full factorial experimental design methodology to carry out practical cutting experiments, where the cutting speed, feed, and depth of cut were the altered variables. The cylindricity error, peak maximum departure, their ratio, and coaxiality are measured and analyzed. The main effect analysis and detailed study are elaborated using the determined equation. It is found that decreasing the studied parameters is advisable if increasing cylinder accuracy is needed.

Innovative high degree of freedom single-multipoint incremental forming system for manufacturing curved thin-walled components

This study proposed a new design and control framework for a novel high degree of freedom single-multipoint incremental forming (HDoF-SMIF) system to manufacture curved thin-walled components. First, a novel HDoF-SMIF system was designed based on the principles of HDoF-SMIF technology (including the description of the mechanical structure and network topology). Following that, to realize the process control of the HDoF-SMIF process, this study introduced a novel control strategy for the tool deflection angle specific to robotic incremental forming. It also developed a synergistic motion control approach for the lifting platform and an accelerated computation method to determine the forming parameters for a multipoint reconfigurable die. Then, a novel HDoF-SMIF principle prototype and control program were built for the designed HDoF-SMIF system structure and control method. Finally, the feasibility of the HDoF-SMIF system was verified with the forming test on the domed component, and the geometrical accuracy and wall thickness distribution of the samples were measured using a 3D optical scanner system to evaluate the forming quality of the established HDoF-SMIF system. The results showed that compared to the conventional single-point incremental forming (SPIF) process, the developed HDoF-SMIF system can provide a more uniform thickness distribution of the formed part with a lower overall thickness thinning rate. Furthermore, by increasing the tool deflection angle with a 1 mm elastomeric interpolator, the overall part's forming accuracy and surface quality can be effectively improved.

Practical Method for Identifying Model Parameters for Machining Error Simulation in End Milling Through Sensor-Less Monitoring and On-Machine Measurement

Depending on cutting conditions, unacceptable machining errors are caused by tool deflection in end milling operations. Many studies have proposed methods for predicting the machining error owing to the tool deflection to achieve the theoretical optimization of the cutting conditions. However, the conventional machining error simulation is not practically utilized to determine the optimal cutting conditions. Tool system stiffness parameters and cutting coefficients must be identified in advance to simulate machining errors. However, dynamometers and displacement sensors are required for parameter identification. Therefore, it is impossible to identify the required parameters in typical factories, which do not possess such special equipment. In this study, a practical method was developed to identify the stiffness parameters that can be determined in factories. The proposed method employs on-machine measurement and sensor-less cutting force monitoring to achieve practical parameter identification. In the proposed method, the profile milling is first conducted. During the milling operation, the cutting force and cutting torque are monitored through a controller based on the sensor-less monitoring technique. After the operation, the machining error distribution on the machined surface is measured on machine using a touch probe. The required parameters are identified by minimizing the differences between the measured and theoretical forces, torques, and machining error distributions.

Optical tool deflection measurement approach using shadow imaging

In incremental sheet forming, geometrical deviations occur due to deflections of the forming stylus. To compensate the deviations, a non-contact in-process tool deflection measurement is required that is capable of measuring the tool tip position with a measurement uncertainty of 15 μm in a volume of 2.0 m × 1.0 m × 0.2 m. For this purpose, an optical multi-sensor system is designed. Each sensor evaluates lateral shift and magnification of the shadow cast from the LED attached close to the tool tip, to enable measuring the lateral and axial tool tip position component, respectively. The experimental validation shows that the sensing principle is sufficiently robust regarding ambient light. As a result, despite a remaining systematic error after calibration that dominates the uncertainty, the measurement requirements are fulfilled by a single sensor regarding the lateral position component. For the axial position component, a triangulation with two sensors is necessary.

Advancements and Challenges in Robot-Assisted Bone Processing in Neurosurgical Procedures.

Practical applications of nerve decompression using neurosurgical robots remain unexplored. Our ongoing research and development initiatives, utilizing industrial robots, aim to establish a secure and efficient neurosurgical robotic system. The principal objective of this study was to automate bone grinding, which is a pivotal component of neurosurgical procedures. To achieve this goal, we integrated an endoscope system into a manipulator and conducted precision bone machining using a neurosurgical drill, recording the grinding resistance values across 3 axes. Our study encompassed 2 core tasks: linear grinding, such as laminectomy, and cylindrical grinding, such as foraminotomy, with each task yielding unique measurement data. In linear grinding, we observed a proportional increase in grinding resistance values in the machining direction with acceleration. This observation suggests that 3-axis resistance measurements are a valuable tool for gauging and predicting deep cortical penetration. However, problems occurred in cylindrical grinding, and a significant error of 10% was detected. The analysis revealed that multiple factors, including the tool tip efficiency, machining speed, teaching methods, and deflection in the robot arm and jig joints, contributed to this error. We successfully measured the resistance exerted on the tool tip during bone machining with a robotic arm across 3 axes. The resistance ranged from 3 to 8 Nm, with the measurement conducted at a processing speed approximately twice that of manual surgery performed by a surgeon. During the simulation of foraminotomy under endoscopic grinding conditions, we encountered a -10% error margin.

Towards Zero-Defect Manufacturing Based on Artificial Intelligence through the Correlation of Forces in 5-Axis Milling Process

Zero-Defect Manufacturing (ZDM) is a promising strategy for reducing errors in industrial processes, aligned with Industry 4.0 and digitalization, aiming to carry out processes correctly the first time. ZDM relies on digital tools, notably Artificial Intelligence (AI), to predict and prevent issues at both product and process levels. This study’s goal is to significantly reduce errors in machining large parts. It utilizes data from process models and in situ monitoring for AI-driven predictions. AI algorithms anticipate part deformation based on manufacturing data. Mechanistic models simulate milling processes, calculating tool deflection from cutting forces and assessing geometric and dimensional errors. Process monitoring provides real-time data to the models during execution. The research focuses on a high-value component from the oil and gas industry, serving as a test piece to predict geometric errors in machining based on the deviation of cutting forces using AI techniques. Specifically, an AISI 1095 steel forged flange, intentionally misaligned to introduce error, undergoes multiple milling operations, including 3-axis roughing and 5-axis finishing, with 3D scans after each stage to monitor progress and deviations. The work concludes that Support Vector Machine algorithms provide accurate results for the estimation of geometric errors from the machining forces.

A systematic approach for data acquisition for tool modelling and analysis of wear-dependent tool deflections during milling Inconel 718

Nickel-based superalloys are commonly used for components in the aerospace industry. Due to their favorable mechanical properties, such as high strength and corrosion resistance, these materials are suitable for use under extreme temperature conditions. However, the poor machinability results in high process forces and high tool wear, and, therefore, large tool displacements, so that high manufacturing tolerances are often difficult to achieve. Simulation systems can be used to optimize the process. The data acquisition for the development of the models required is challenging. In the following, a method for in-situ digitization of the tool is presented. Furthermore, the occurring tool deflections during the machining of Inconel718 are analyzed for different wear conditions to serve as basis for the parameterization of simulation models.

Modeling of high-feed milling and surface quality applied to Inconel 718

In modern manufacturing, machining remains a vital process for complex mechanical components. In particular, the aerospace industry extensively employs high-feed milling techniques to machine complex geometries from nickel-based superalloys. This study focuses on the analysis and modeling of high-feed milling for Inconel 718 in 2.5-axis machining. Its objective is to develop a generalized model of high-feed milling that enables the prediction of surface topography. The proposed model integrates crucial geometric parameters of the tool and its exact kinematic within the machine, along with tool and machine deflections caused by cutting forces. A key novelty of this research lies in its capability to determine surface topography and its quality based on a generalized model, representing significant progress in the field of high-feed milling. To validate the model, experimental efforts are measured to characterize the cutting forces and system deflections during machining. The developed approach demonstrates its ability to model surface topography and to predict surface roughness. It also highlights the influence of tool and machine deflection on surface quality. This research contributes to the advancement of the application of high-feed milling in aerospace manufacturing by enhancing machining capabilities and improving part quality.

FUNDAMENTAL ANALYSIS ON THE DYNAMIC BEHAVIOR OF TOOLS WITH STRUCTURED FUNCTIONAL SURFACES IN CUTTING OPERATIONS

The productivity of machining processes is often limited by the occurrence of dynamic effects. The investigated approach intends to counteract tool deflections, and thus to damp and disrupt chatter vibrations by using milling tools with defined functional structures on the flank faces at the frontal cutting edges. For the fundamental investigation of the interactions between structural geometric properties and the tool-workpiece interaction, the engagement situation was geometrically evaluated on a highly abstracted level. Subsequently, hypotheses derived from this were validated experimentally in analogy tests with linear cutting motion. In these cutting experiments, dynamic deflections were induced by an external excitation of the specifically compliant modular tool system. Finally, the technologically most relevant structure variants were applied to milling tools and evaluated with regard to their dynamic behavior. This investigation was preceded by a simulation-based analysis of the material removal on the frontal flank face as a function of the process configuration, which is characterized by multiple intersecting cuts in milling processes. By specifically optimizing and coordinating the structure design and the process configuration, an increase in process stability and thus productivity of at least 100% could be achieved.

Determination of the actual deflection of the cutting tool ın turning by the Castigliano theorem

The turning method is a widely utilized technique in machining. The effect of machining parameters on the machining quality in turning is quite high. A longer tool overhang reduces tool rigidity, leading to increased tool deflection and subsequently, a decrease in machining quality. The tool overhang should be as short as possible in order to reduce tool deflection and eliminate the negative effects of vibration. Another critical factor affecting machining quality, as much as the tool overhang length is the distance between the main cutting edge and the tool holder axis. In the turning process, the alteration of the main cutting-edge position significantly influences the amount of tool deflection. When the main cutting edge is positioned farther from the tool holder axis, it generates a greater torsional moment effect, which negatively impacts machining quality. However, although the main cutting edge position of the turning tool has a great effect on the machining quality, it has not been adequately explored in the existing literature.This study examines how deflection values vary concerning the deviation of the main cutting edge from the tool holder axis using various methods and compares the results. In contrast to the commonly used deviation equation, this research applies the Castigliano theorem, which provides results much closer to actual tool deflection values. The outcomes derived from the Castigliano theorem are then compared with finite element analysis (FEM) and experimental studies. The proposed theoretical approach aligns well with the experimental results, highlighting the significance of considering torsional moments alongside bending moments as they both play a substantial role in tool deflection.

An FEM-ANN Based Analysis of Cutting Force and Cutting Tool Deflection to Predict Tool Wear in Double Tool Turning Process

In the conventional turning process, cutting forces and cutting tool deflection plays an important role in tool wear mechanism. The cutting tool is subjected to uneven wear due to heavy cutting forces. This further leads to shear deformation of the tool which ultimately affects the surface texture of the workpiece. In this paper, an experimental setup is designed and fabricated which can hold rigidly the two cutting tools namely, the front and rear tool in opposite direction. Moreover, to check its robustness and feasibility, the numerical modelling of the experimental setup is performed using the experimental data. A total of nine simulation runs were performed according to the machining parameters used in the experimental study to check the accuracy of the Finite element model. Additionally, these experimental values of resultant cutting force were used to obtain the resultant deflection of both the cutting tools through simulation tests. Finally, the values of resultant cutting force and the resultant deflection of both the tools were predicted using Artificial Neural Networks (ANN) and compared to estimate the tool wear. It was found that the experimental results were in good agreement with the ANN predicted results.

Experimental investigation of novel internal thread fabrication: A drill thread milling

In this study, a novel method for fabricating internal threads called drill thread milling (DTM) was experimentally investigated. DTM is a fabrication process that combines drilling and thread milling into a single process, thereby eliminating the need for a pilot hole and making it a viable alternative to existing methods. To optimize the DTM process, the characteristics of DTM must first be understood. In this study, the machining characteristics of DTM were examined using a variety of materials and machining parameters. The results were then compared with those obtained using the tapping method. During the experiments, the machining force and vibration were recorded, and the results indicated that DTM required less machining time than did the tapping method. However, DTM exhibited an additional periodic components in the machining force, which could resulted in chatter. In certain materials, a tool offset was required to pass the thread gauge, indicating substantial tool deflection occurred during the machining process. The examination of the resulting threads revealed that, for the same thread depth, DTM required a shallower hole than that required in the tapping method.

Influence of microphone tilt angle on instability identification in micromilling of thin-walled Ti6Al4V

High speed micromilling is the most preferred manufacturing process to fabricate complex 3D featured thin-walled structures like stents, turbine blades, micro-fins, cabin parts etc., that are extensively used in bio-medical, energy, automobile and aerospace sectors. Fabricating thin-walled structures with high dimensional and geometrical accuracy requires chatter free machining parameters. Different sensors like accelerometer, current sensors, laser based sensors, vibration pick-ups etc. are available for capturing the vibration while machining thin-walled structures. Each sensor has its own advantages and disadvantages, like laser based sensors adds noise to response as chips fly past in the laser path and accelerometer captures deflection of both micro-cutting tool and thin-walled workpiece. Hence, In-process chatter identification is a challenging task in thin-wall micromilling. Also, the Filtering of signals to remove the noise from signals captured via contact type and laser based sensors results in loss of low-amplitude chatter data in high-speed micromilling. Consequently, there is a need of sensor, which functions similar to contact type with less or no loss in low-amplitude chatter data. The proposed work compares vibration signal captured using accelerometer and microphone at different tilt angles for radial milling of thin-walled Ti6Al4V at different radial immersion to analyse the effect of tilt-angle on chatter identification. The recorded signals from both accelerometer and microphone are analysed in time domain by estimation and comparison of statistical parameters, in frequency domain by analysing the distributed frequency and in time–frequency domain by analysing the energy of the signals. Complete characterization of the signals in time, frequency and time–frequency domain/methods indicated that microphone at 60° tilt angle can be used as an alternative sensor for chatter onset identification without loss in chatter data irrespective of cutting condition. Machined surface analysis of thin-walled structures complements the microphone as an effective chatter identification sensor.

Study on helical milling of SS 304 with small diameter tools under the influence of minimum quantity lubrication (MQL)

The objective of the present work is to study the effect of minimum quantity lubrication (MQL) on the performance of helical milling for machining high-quality holes with a small-diameter tool. Helical milling with small tools (diameter < 5 mm) has been a challenging domain due to the problem of tool deflection, which deteriorates the hole quality and adversely affects the process efficiency. In this study, helical milling of stainless steel (SS 304) is carried to machine holes using a 3 mm diameter coated carbide tool in minimum quantity lubrication (MQL), and the performance is compared with dry and conventional flood cooling based on the hole quality and tool wear. The findings of this study reveal that MQL results in high-quality holes with the least circularity and cylindricity errors compared to dry and flood lubrication. Surface morphology study of the machined holes shows that the holes generated in MQL have smoother surfaces with no evidence of severe surface defects. MQL can also significantly mitigate the problem of tool deflection encountered in small-diameter tools and reduce tool wear by 33.3% and 21.7% compared to dry and flood lubrication, respectively. As per ISO 286-2 standard, hole quality up to grade H8 is achieved with MQL, while dry condition and flood lubrication yield hole quality corresponding to H9 grade. This study concludes that MQL-assisted helical milling is one of the sustainable alternatives for the production of high-quality small-diameter holes in stainless steel.

Calculation method of the build-up rate of the internal push point-the-bit rotary steering tool

The internal push point-the-bit rotary steering tool is a new type of dynamic point-the-bit rotary steerable system. This paper comprehensively uses the mechanical and trajectory method to calculate the build-up rate of the tool to evaluate its build-up ability and realize accurate control of the wellbore trajectory during the directional drilling process. The influence of tool structure, wellbore geometric parameters, drilling process parameters, bit-cutting anisotropy, and formation characteristics on the build-up ability are considered. The tool deflection force, the structural lateral force on the bit, and the formation deflection force were calculated respectively, and the calculation model for the build-up rate of the internal push point-the-bit rotary steering tool is established according to the relationship between force and cutting displacement. In order to study the variation of the build-up rate of the tool in different well slope sections under the conditions of fixed bottom hole assembly and formation parameters, the build-up rate simulation calculation was carried out. The calculation results show that the maximum build-up rate of the tool under stable and controlled conditions increases with the increase of the well inclination, which means the internal push point-the-bit rotary steering tool is suitable for extended reach wells and horizontal wells. The research results provide a theoretical basis for the design of bottom hole assembly and the optimization of drilling process parameters when using the internal push point-the-bit rotary steering tool for directional drilling.