Journal of Manufacturing and Materials Processing

Research

12 pages, 5410 KiB

Open AccessArticle

Progressive Tool Wear in Cryogenic Machining: The Effect of Liquid Nitrogen and Carbon Dioxide

by Yusuf Kaynak and Armin Gharibi

J. Manuf. Mater. Process. 2018, 2(2), 31; https://doi.org/10.3390/jmmp2020031 - 21 May 2018

Cited by 37 | Viewed by 5414

This experimental study focuses on various cooling strategies and lubrication-assisted cooling strategies to improve machining performance in the turning process of AISI 4140 steel. Liquid nitrogen (LN₂) and carbon dioxide (CO₂) were used as cryogenic coolants, and their performances [...] Read more.

This experimental study focuses on various cooling strategies and lubrication-assisted cooling strategies to improve machining performance in the turning process of AISI 4140 steel. Liquid nitrogen (LN₂) and carbon dioxide (CO₂) were used as cryogenic coolants, and their performances were compared with respect to progression of tool wear. Minimum quantity lubrication (MQL) was also used with carbon dioxide. Progression of wear, including flank and nose, are the main outputs examined during experimental study. This study illustrates that carbon dioxide-assisted cryogenic machining alone and with minimum quantity lubrication does not contribute to decreasing the progression of wear within selected cutting conditions. This study also showed that carbon dioxide-assisted cryogenic machining helps to increase chip breakability. Liquid nitrogen-assisted cryogenic machining results in a reduction of tool wear, including flank and nose wear, in the machining process of AISI 4140 steel material. It was also observed that in the machining process of this material at a cutting speed of 80 m/min, built-up edges occurred in both cryogenic cooling conditions. Additionally, chip flow damage occurs in particularly dry machining. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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12 pages, 4027 KiB

Open AccessArticle

Experimental and Modeling Study of Liquid-Assisted—Laser Beam Micromachining of Smart Ceramic Materials

by Mayur Parmar and Sagil James

J. Manuf. Mater. Process. 2018, 2(2), 28; https://doi.org/10.3390/jmmp2020028 - 07 May 2018

Cited by 14 | Viewed by 4048

Abstract

Smart ceramic materials are next generation materials with the inherent intelligence to adapt to change in the external environment. These materials are destined to play an essential role in several critical engineering applications. Machining these materials using traditional machining processes is a challenge. [...] Read more.

Smart ceramic materials are next generation materials with the inherent intelligence to adapt to change in the external environment. These materials are destined to play an essential role in several critical engineering applications. Machining these materials using traditional machining processes is a challenge. The laser beam micromachining (LBMM) process has the potential to machine such smart materials. However, laser machining when performed in air induces high thermal stress on the surface, often leading to crack formation, recast and re-deposition of ablated material, and large heat-affected zones (HAZ). Performing laser beam machining in the presence of a liquid medium could potentially resolve these issues. This research investigates the possibility of using a Liquid Assisted—Laser Beam Micromachining (LA-LBMM) process for micromachining smart ceramic materials. Experimental studies are performed to compare the machining quality of laser beam machining process in air and in a liquid medium. The study reveals that the presence of liquid medium helps in controlling the heat-affected zone and the taper angle of the cavity drilled, thereby enhancing the machining quality. Analytical modeling is developed for the prediction of HAZ and cavity diameter both in air and underwater conditions, and the model is capable of predicting the experimental results to within 10% error. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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15 pages, 5530 KiB

Open AccessArticle

Application of Finite Element Method to Analyze the Influences of Process Parameters on the Cut Surface in Fine Blanking Processes by Using Clearance-Dependent Critical Fracture Criteria

by Phyo Wai Myint, Seiya Hagihara, Toru Tanaka, Shinya Taketomi and Yuichi Tadano

J. Manuf. Mater. Process. 2018, 2(2), 26; https://doi.org/10.3390/jmmp2020026 - 23 Apr 2018

Cited by 3 | Viewed by 3590

Abstract

The correct choice of process parameters is important in predicting the cut surface and obtaining a fully-fine sheared surface in the fine blanking process. The researchers used the value of the critical fracture criterion obtained by long duration experiments to predict the conditions [...] Read more.

The correct choice of process parameters is important in predicting the cut surface and obtaining a fully-fine sheared surface in the fine blanking process. The researchers used the value of the critical fracture criterion obtained by long duration experiments to predict the conditions of cut surfaces in the fine blanking process. In this study, the clearance-dependent critical ductile fracture criteria obtained by the Cockcroft-Latham and Oyane criteria were used to reduce the time and cost of experiments to obtain the value of the critical fracture criterion. The Finite Element Method (FEM) was applied to fine blanking processes to study the influences of process parameters such as the initial compression, the punch and die corner radii and the shape and size of the V-ring indenter on the length of the sheared surface. The effects of stress triaxiality and punch diameters on the cut surface produced by the fine blanking process are also discussed. The verified process parameters and tool geometry for obtaining a fully-fine sheared SPCC surface are described. The results showed that the accurate and stable prediction of ductile fracture initiation can be achieved using the Oyane criterion. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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11 pages, 19101 KiB

Open AccessArticle

Coating of Ultra-Small Micro End Mills: Analysis of Performance and Suitability of Eight Different Hard-Coatings

by Martin Bohley, Ingo G. Reichenbach, Sonja Kieren-Ehses, Lukas Heberger, Peter A. Arrabiyeh, Rolf Merz, Luisa Böhme, Julian Hering, Benjamin Kirsch, Michael Kopnarski, Eberhard Kerscher, Georg Von Freymann and Jan C. Aurich

J. Manuf. Mater. Process. 2018, 2(2), 22; https://doi.org/10.3390/jmmp2020022 - 29 Mar 2018

Cited by 8 | Viewed by 5112

Abstract

Due to the constant need for better functionalized surfaces or smaller, function integrated components, precise and efficient manufacturing processes have to be established. Micro milling with micro end mills is one of the most promising processes for this task as it combines a [...] Read more.

Due to the constant need for better functionalized surfaces or smaller, function integrated components, precise and efficient manufacturing processes have to be established. Micro milling with micro end mills is one of the most promising processes for this task as it combines a high geometric flexibility in a wide range of machinable materials with low set-up costs. A downside of this process is the wear of the micro end mills. Due to size effects and the relatively low cutting speed, the cutting edge is especially subjected to massive abrasive wear. One possibility to minimize this wear is coating of micro end mills. This research paper describes the performance of eight different hard coatings for micro end mills with a diameter <40 µm and discusses some properties for the best performing coating type. With this research, it is therefore possible to boost the possibilities of micro milling for the manufacture of next generation products. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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10 pages, 4012 KiB

Open AccessArticle

Influence of NC Program Quality and Geometric Errors of Rotary Axes on S-Shaped Machining Test Accuracy

by Ryuta Sato, Keiichi Shirase and Yukitoshi Ihara

J. Manuf. Mater. Process. 2018, 2(2), 21; https://doi.org/10.3390/jmmp2020021 - 21 Mar 2018

Cited by 13 | Viewed by 4841

Abstract

An S-shaped machining test is proposed for the ISO 10791-7 standard to verify the performance of five-axis machining centers. However, investigation of the factor that has the most influence on the geometrical accuracy of finished S-shaped workpieces has not been undertaken. Determination of [...] Read more.

An S-shaped machining test is proposed for the ISO 10791-7 standard to verify the performance of five-axis machining centers. However, investigation of the factor that has the most influence on the geometrical accuracy of finished S-shaped workpieces has not been undertaken. Determination of the influence of NC program tolerance and geometric errors concerning the rotary axes on the accuracy of the finished S-shaped workpiece forms the main objective of the study. Actual cutting experiments as well as simulations were performed during the proposed investigation. Our results clarify that NC-program tolerance has a significant influence on the end quality of the machined surface. Although geometric errors pertaining to rotary axes also have a significant influence on machined-surface quality, it is difficult to evaluate the influence of each individual error, because all geometric errors make glitches at the same point on the machined surface. The proposed S-shaped machining test can be used to provide a complete demonstration of available machining techniques. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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11 pages, 3201 KiB

Open AccessArticle

Correlations between Thermal Loads during Grind-Hardening and Material Modifications Using the Concept of Process Signatures

by Benjamin Kolkwitz, Ewald Kohls, Carsten Heinzel and Ekkard Brinksmeier

J. Manuf. Mater. Process. 2018, 2(1), 20; https://doi.org/10.3390/jmmp2010020 - 16 Mar 2018

Cited by 6 | Viewed by 3716

Abstract

During the process of grind-hardening, the dissipated heat from the process is utilized for a surface layer hardening of machined components made of steel. A martensitic phase transformation occurs within the affected subsurface regions and compressive residual stresses are induced. However, the layout [...] Read more.

During the process of grind-hardening, the dissipated heat from the process is utilized for a surface layer hardening of machined components made of steel. A martensitic phase transformation occurs within the affected subsurface regions and compressive residual stresses are induced. However, the layout of a grind-hardening process for given hardness results (material modification) is very difficult. Thus, a series of extensive experimental tests is required. To reduce this experimental effort, the newly developed concept of Process Signatures is used to describe the material modifications based on the thermal load appearing during the grind-hardening process. Based on an analytical calculation of the temperature fields during the grind-hardening process (surface- and external-cylindrical-grind-hardening), the internal thermal load was characterized by the maximum contact zone temperature and the maximum temperature gradient at the surface and was correlated with the process quantities (heat flux to the workpiece and the contact time). Metallographic investigations were used to analyze the surface hardening depth and the hardness change at the surface, which were correlated with the quantities describing the internal material loads. The results show that the surface hardening depth was mainly governed by the maximum contact zone temperature and the maximum temperature gradient at the surface, whereas the hardness change at the surface was influenced additionally by the quenching time. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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14 pages, 36424 KiB

Open AccessArticle

Prediction of Feed-Rate Slowdowns in Precise Micromilling Processes

by Alexander Meijer, Eugen Krebs, Petra Wiederkehr and Dirk Biermann

J. Manuf. Mater. Process. 2018, 2(1), 19; https://doi.org/10.3390/jmmp2010019 - 14 Mar 2018

Cited by 3 | Viewed by 4155

Abstract

In a production of filigree and complex geometries, different NC-controlled processes such as laser cutting, EDM milling, and micromachining require a constant feed rate to ensure high-quality manufacturing results. Due to the technically limited acceleration ability of the machine tool axes, the nominal [...] Read more.

In a production of filigree and complex geometries, different NC-controlled processes such as laser cutting, EDM milling, and micromachining require a constant feed rate to ensure high-quality manufacturing results. Due to the technically limited acceleration ability of the machine tool axes, the nominal feed cannot always be achieved. This in particular is the case when the machine tool has to perform a significant change of direction in corners. In this paper, the impact of too low feed rates on the process of precise micromilling of a hardened high-speed steel AISI (M3:2) 63 ± 1 HRC) is discussed. An unattained feed rate leads to a ploughing dominated process with a high burr formation resulting in a huge potential loss of micromilling processes. Furthermore, a simulation approach is presented which allows the prediction of the actually achieved feed rate. The developed machine model provides a reliable method to identify critical areas in the entire NC program. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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8 pages, 2086 KiB

Open AccessArticle

Random and Systematic Errors Share in Total Error of Probes for CNC Machine Tools

by Adam Wozniak and Michal Jankowski

J. Manuf. Mater. Process. 2018, 2(1), 17; https://doi.org/10.3390/jmmp2010017 - 08 Mar 2018

Cited by 6 | Viewed by 4565

Abstract

Probes for CNC machine tools, as every measurement device, have accuracy limited by random errors and by systematic errors. Random errors of these probes are described by a parameter called unidirectional repeatability. Manufacturers of probes for CNC machine tools usually specify only this [...] Read more.

Probes for CNC machine tools, as every measurement device, have accuracy limited by random errors and by systematic errors. Random errors of these probes are described by a parameter called unidirectional repeatability. Manufacturers of probes for CNC machine tools usually specify only this parameter, while parameters describing systematic errors of the probes, such as pre-travel variation or triggering radius variation, are used rarely. Systematic errors of the probes, linked to the differences in pre-travel values for different measurement directions, can be corrected or compensated, but it is not a widely used procedure. In this paper, the share of systematic errors and random errors in total error of exemplary probes are determined. In the case of simple, kinematic probes, systematic errors are much greater than random errors, so compensation would significantly reduce the probing error. Moreover, it shows that in the case of kinematic probes commonly specified unidirectional repeatability is significantly better than 2D performance. However, in the case of more precise strain-gauge probe systematic errors are of the same order as random errors, which means that errors correction or compensation, in this case, would not yield any significant benefits. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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10 pages, 7340 KiB

Open AccessArticle

Material Impact on Diamond Machining of Diffractive Optical Structures for UV-Application

by Ann-Katrin Holthusen, Oltmann Riemer and Ekkard Brinksmeier

J. Manuf. Mater. Process. 2018, 2(1), 15; https://doi.org/10.3390/jmmp2010015 - 01 Mar 2018

Cited by 8 | Viewed by 3967

Abstract

This paper discusses the impact of different machining parameters on structuring quality in a diamond turning process for the machining of diffractive optical elements (DOEs). Special attention is paid to the impact of the material on the geometric structuring quality. First, the machining [...] Read more.

This paper discusses the impact of different machining parameters on structuring quality in a diamond turning process for the machining of diffractive optical elements (DOEs). Special attention is paid to the impact of the material on the geometric structuring quality. First, the machining process for DOEs is described. The structuring process is based on a face turning process combined with a nano Fast Tool Servo (nFTS), which varies the depth of cuts within a range of up to 1 μm at a maximum frequency of 5 kHz. The diamond tools being used exhibit customized rectangular tool geometry with a tool width of 10–20 μm. To determine the material impact and the influence of several machining parameters, different structures have been machined, and their geometric and topographic quality has been analyzed. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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14 pages, 13736 KiB

Open AccessArticle

Modelling Machine Tools using Structure Integrated Sensors for Fast Calibration

by Benjamin Montavon, Philipp Dahlem, Martin Peterek, Markus Ohlenforst and Robert H. Schmitt

J. Manuf. Mater. Process. 2018, 2(1), 14; https://doi.org/10.3390/jmmp2010014 - 23 Feb 2018

Cited by 13 | Viewed by 5793

Abstract

Monitoring of the relative deviation between commanded and actual tool tip position, which limits the volumetric performance of the machine tool, enables the use of contemporary methods of compensation to reduce tolerance mismatch and the uncertainties of on-machine measurements. The development of a [...] Read more.

Monitoring of the relative deviation between commanded and actual tool tip position, which limits the volumetric performance of the machine tool, enables the use of contemporary methods of compensation to reduce tolerance mismatch and the uncertainties of on-machine measurements. The development of a primarily optical sensor setup capable of being integrated into the machine structure without limiting its operating range is presented. The use of a frequency-modulating interferometer and photosensitive arrays in combination with a Gaussian laser beam allows for fast and automated online measurements of the axes’ motion errors and thermal conditions with comparable accuracy, lower cost, and smaller dimensions as compared to state-of-the-art optical measuring instruments for offline machine tool calibration. The development is tested through simulation of the sensor setup based on raytracing and Monte-Carlo techniques. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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11 pages, 1782 KiB

Open AccessArticle

The Prediction of Surface Error Characteristics in the Peripheral Milling of Thin-Walled Structures

by Sepp Wimmer and Michael F. Zaeh

J. Manuf. Mater. Process. 2018, 2(1), 13; https://doi.org/10.3390/jmmp2010013 - 22 Feb 2018

Cited by 12 | Viewed by 3761

Abstract

Lightweight design is gaining in importance throughout the engineering sector, and with it, workpieces are becoming increasingly complex. Particularly, thin-walled parts require highly accurate and efficient machining strategies. Such low-rigidity structures usually undergo significant deformations during peripheral milling operations, thus suffering surface errors [...] Read more.

Lightweight design is gaining in importance throughout the engineering sector, and with it, workpieces are becoming increasingly complex. Particularly, thin-walled parts require highly accurate and efficient machining strategies. Such low-rigidity structures usually undergo significant deformations during peripheral milling operations, thus suffering surface errors and a violation of tolerance specifications. This article introduces a general approach to mitigating surface errors during the peripheral milling of thin-walled aluminum workpieces. It incorporates an analytical approach to predicting surface-error characteristics based on geometrical quantities and process parameters, which is presented in detail. Milling experiments, including geometrical measurements of the samples, have been performed to verify the approach. The approach allows for a pre-selection of parameter sets that result in surface errors that can be compensated with minimal effort. Additionally, the introduced model offers a simple criterion to assess potential error mitigation by applying the respective tool-path adjustments. In doing so, the amount of costly numerical simulations or experiments is significantly reduced. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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11 pages, 2148 KiB

Open AccessFeature PaperArticle

Precise In-Process Strain Measurements for the Investigation of Surface Modification Mechanisms

by Andreas Tausendfreund, Dirk Stöbener and Andreas Fischer

J. Manuf. Mater. Process. 2018, 2(1), 9; https://doi.org/10.3390/jmmp2010009 - 30 Jan 2018

Cited by 18 | Viewed by 3503

Abstract

The question, how certain surface layer properties (for example, hardness or roughness) can be specifically influenced in different manufacturing processes, is of great economic interest. A prerequisite for the investigation of the formation of surface layer properties is the metrological assessment of the [...] Read more.

The question, how certain surface layer properties (for example, hardness or roughness) can be specifically influenced in different manufacturing processes, is of great economic interest. A prerequisite for the investigation of the formation of surface layer properties is the metrological assessment of the material stresses during processing. Up to now, no commercial in-process measuring system exists, which is able to determine material stresses in the form of mechanical strains in high-dynamic manufacturing processes with sufficient accuracy. A detailed analysis of the resolution limits shows that speckle photography enables deformation measurements with a resolution in the single-digit nanometer range. Thus, speckle photography basically offers the potential to measure material stresses during processing. Using the example of single-tooth milling, the applicability of speckle photography for in-process stress measurements is demonstrated. Even in such highly dynamic manufacturing processes with cutting speeds up to 10 m/s, the absolute measurement uncertainty of the strain is less than 0.05%. This is more than one order of magnitude lower than the occurring maximal strain. Therefore, speckle photography is suitable for characterizing the dynamic stresses and the material deformations in manufacturing processes. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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27 pages, 9295 KiB

Open AccessFeature PaperArticle

Modal Analysis, Metrology, and Error Budgeting of a Precision Motion Stage

by Ahmet Okyay, Kaan Erkorkmaz and Mir Behrad Khamesee

J. Manuf. Mater. Process. 2018, 2(1), 8; https://doi.org/10.3390/jmmp2010008 - 24 Jan 2018

Cited by 1 | Viewed by 6308

Abstract

In this study, a precision motion stage, whose design utilizes a single shaft supported from the bottom by an air bearing and voice coil actuators in complementary double configuration, is evaluated for its dynamic properties, motion accuracy, and potential machining force response, through [...] Read more.

In this study, a precision motion stage, whose design utilizes a single shaft supported from the bottom by an air bearing and voice coil actuators in complementary double configuration, is evaluated for its dynamic properties, motion accuracy, and potential machining force response, through modal testing, laser interferometric metrology, and spectral analysis, respectively. Modal testing is carried out using two independent methods, which are both based on impact hammer testing. Results are compared with each other and with the predicted natural frequencies based on design calculations. Laser interferometry has been used with varying optics to measure the geometric errors of motion. Laser interferometry results are merged with measured servo errors, estimated thermal errors, and the predicted dynamic response to machining forces, to compile the error budget. Overall accuracy of the stage is calculated as peak-to-valley 5.7 μm with a 2.3 μm non-repeatable part. The accuracy measured is in line with design calculations which incorporated the accuracy grade of the encoder scale and the dimensional tolerances of structural components. The source of the non-repeatable errors remains mostly equivocal, as they fall in the range of random errors of measurement in laser interferometry like alterations of the laser wavelength due to air turbulence. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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12 pages, 5050 KiB

Open AccessArticle

Error Separation Method for Precision Measurement of the Run-Out of a Microdrill Bit by Using a Laser Scan Micrometer Measurement System

by Zengyuan Niu, Yuan-Liu Chen, Yuki Shimizu, Hiraku Matsukuma and Wei Gao

J. Manuf. Mater. Process. 2018, 2(1), 4; https://doi.org/10.3390/jmmp2010004 - 12 Jan 2018

Cited by 4 | Viewed by 5229

Abstract

This paper describes an error separation method for a precision measurement of the run-out of a microdrill bit by using a measurement system consisting of a concentricity gauge and a laser scan micrometer (LSM). The proposed error separation method can achieve a sub-micrometric [...] Read more.

This paper describes an error separation method for a precision measurement of the run-out of a microdrill bit by using a measurement system consisting of a concentricity gauge and a laser scan micrometer (LSM). The proposed error separation method can achieve a sub-micrometric measurement accuracy of the run-out of the microdrill bit without the requirement of ultra-precision rotary drive devices. In the measurement, the spindle error motion of the concentricity gauge is firstly measured by using the LSM and a small-diameter artifact, instead of the conventionally used displacement probes and large-diameter artifact, in order to determine the fine position of the concentricity gauge when the spindle error motion is at its minimum. The microdrill bit is rotated at the fine position for the measurement of the run-out, so that the influence of the spindle error motion can thus be reduced, which could not be previously realized by commercial measurement systems. Experiments were carried out to verify the feasibility of the proposed error separation method for the measurement of the run-out of the microdrill bit. The measurement results and the measurement uncertainty confirmed that the proposed method is reliable for the run-out measurement with sub-micrometric accuracy. Full article

(This article belongs to the Special Issue Precision Manufacturing)

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