Research

8 pages, 3152 KiB

Open AccessArticle

Experimental Investigation of Stainless Steel SAE304 Laser Engraving Cutting Conditions

by Evangelos Nikolidakis, Ioannis Choreftakis and Aristomenis Antoniadis

Machines 2018, 6(3), 40; https://doi.org/10.3390/machines6030040 - 03 Sep 2018

Cited by 7 | Viewed by 5029

Laser machining processes are a new entrant and a rapidly evolving type of non-conventional machining process which allows the machining of complex geometries with high precision, surface quality and productivity in a wide range of materials. Thus, the need for creating a method [...] Read more.

Laser machining processes are a new entrant and a rapidly evolving type of non-conventional machining process which allows the machining of complex geometries with high precision, surface quality and productivity in a wide range of materials. Thus, the need for creating a method has emerged that will help the laser machine operator to select the optimal process parameters. In this study an experimental investigation of the effect of the process parameters on the effectiveness of the laser engraving process was held. The examined process parameters were namely the average output power, the repetition rate, and the scanning speed. For this purpose 126 experimental samples, with various combinations of process parameters using a nanosecond Nd:YAG DMG MORI Lasertec 40 laser machine on a SAE 304 stainless steel plate were made. The measured criteria which evaluated the effectiveness of the process were the removed material layer thickness and the material removal rate. Full article

(This article belongs to the Special Issue Precision Machining)

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11 pages, 11010 KiB

Open AccessArticle

Experimental Analysis of the Effect of Vibration Phenomena on Workpiece Topomorphy Due to Cutter Runout in End-Milling Process ^†

by Constantine David, Dimitrios Sagris, Evlampia Stergianni, Christos Tsiafis and Ioannis Tsiafis

Machines 2018, 6(3), 27; https://doi.org/10.3390/machines6030027 - 01 Jul 2018

Cited by 13 | Viewed by 4205

Abstract

Profile end-milling processes are very susceptible to vibrations caused by cutter runout especially when it comes to operations where the cutter diameter is ranging in few millimeters scale. At the same time, the cutting conditions that are chosen for the milling process have [...] Read more.

Profile end-milling processes are very susceptible to vibrations caused by cutter runout especially when it comes to operations where the cutter diameter is ranging in few millimeters scale. At the same time, the cutting conditions that are chosen for the milling process have a complementary role on the excitation mechanisms that take place in the cutting area between the cutting tool and the workpiece. Consequently, the study of milling processes in the case that a cutter runout exists is of special interest. The subject of this paper is the experimental analysis of the effect of cutter runout on cutter vibration and, by extension, how this affects the chip removal and, thereby, the workpiece topomorphy. Based on cutting force measurements correlated with the workpiece topomorphy under various cutting process parameters, such as the cutting speed, feed rate, and the axial cutting depth, some useful results are extracted. Hence, the effect of vibration phenomena, caused by cutter runout, on the workpiece topomorphy in end milling can be evaluated. Full article

(This article belongs to the Special Issue Precision Machining)

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12 pages, 2168 KiB

Open AccessArticle

Prediction of Thrust Force and Cutting Torque in Drilling Based on the Response Surface Methodology

by Panagiotis Kyratsis, Angelos P. Markopoulos, Nikolaos Efkolidis, Vasileios Maliagkas and Konstantinos Kakoulis

Machines 2018, 6(2), 24; https://doi.org/10.3390/machines6020024 - 04 Jun 2018

Cited by 26 | Viewed by 6213

Abstract

In this research, experimental studies were based on drilling with solid carbide tools and the material used was Al7075. The study primarily focused on investigating the effects of machining parameters (cutting speed, feed rate, diameter of the tool) on the thrust force ( [...] Read more.

In this research, experimental studies were based on drilling with solid carbide tools and the material used was Al7075. The study primarily focused on investigating the effects of machining parameters (cutting speed, feed rate, diameter of the tool) on the thrust force (F_z) and the cutting torque (M_z) when drilling an Al7075 workpiece. The experimental data were analyzed using the response surface methodology (RSM) with an aim to identify the significant factors on the development of both the F_z and M_z. The application of the mathematical models provided favorable results with an accuracy of 3.4% and 4.7%, for the F_z and the M_z, respectively. Analysis of variance (ANOVA) was applied in order to examine the effectiveness of the model, and both mathematical models were established and validated. The equations derived proved to be very precise when a set of validation tests were executed. The importance of the factors’ influence over the responses was also presented. Both the diameter of the cutting and the feed rate were found to be the factors of high significance, while cutting speed did not affect considerably the F_z and M_z in the experiments performed. Full article

(This article belongs to the Special Issue Precision Machining)

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11 pages, 9927 KiB

Open AccessArticle

Influence of Hub Parameters on Joining Forces and Torque Transmission Output of Plastically-Joined Shaft-Hub-Connections with a Knurled Contact Surface

by Lukáš Suchý, Erhard Leidich, Thoralf Gerstmann and Birgit Awiszus

Machines 2018, 6(2), 16; https://doi.org/10.3390/machines6020016 - 09 Apr 2018

Cited by 4 | Viewed by 9537

Abstract

A knurled interference fit is a machine part connection made by a plastic joining, which includes the advantages of commonly-used shaft-hub-connections. The combination of the friction and form fit, which are responsible for torque transmission, results in a higher power density than conventional [...] Read more.

A knurled interference fit is a machine part connection made by a plastic joining, which includes the advantages of commonly-used shaft-hub-connections. The combination of the friction and form fit, which are responsible for torque transmission, results in a higher power density than conventional connections. In this paper, parameter gaps are bridged with the aim of enhance the design calculation of the knurled interference fit. Experimental investigations on the shaft chamfer angle (100Cr6) and hub-diameter-ratio (AlSi1MgMn) were performed. The analytical approaches are developed for calculating the joining force and maximal torque capacity by accounting for experimentally investigated loss of load transmission at high hub-diameter-ratios and high shaft chamfer angles. The presented calculation approach is an accurate tool for the assessment of early machine designs of the knurled interference fit and helps to save from having to perform time-extensive tests. Full article

(This article belongs to the Special Issue Precision Machining)

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9 pages, 11053 KiB

Open AccessArticle

Theoretical and Experimental Studies of Over-Polishing of Silicon Carbide in Annular Polishing

by Junjie Zhang, La Han, Haiying Liu, Yikai Shi, Yongda Yan and Tao Sun

Machines 2018, 6(2), 15; https://doi.org/10.3390/machines6020015 - 04 Apr 2018

Cited by 6 | Viewed by 3925

Abstract

Annular polishing technology is an important optical machining method for achieving a high-precision mirror surface on silicon carbide. However, the inevitable over-polishing of the specimen edge in annular polishing deteriorates achieved surface quality. In the present work, we first analytically investigate the kinematic [...] Read more.

Annular polishing technology is an important optical machining method for achieving a high-precision mirror surface on silicon carbide. However, the inevitable over-polishing of the specimen edge in annular polishing deteriorates achieved surface quality. In the present work, we first analytically investigate the kinematic coupling of multiple relative motions in the annular polishing process and subsequently derive an analytical model that addresses the principle of material removal at specimen edge based on the Preston equation and the rigid body contact model. We then perform finite element simulations and experiments involving annular polishing of silicon carbide (SiC), which jointly exhibit agreement with the derived analytical model of material removal. Full article

(This article belongs to the Special Issue Precision Machining)

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12 pages, 16869 KiB

Open AccessArticle

Effects of Setting Errors (Insert Run-Outs) on Surface Roughness in Face Milling When Using Circular Inserts

by Csaba Felhő and János Kundrák

Machines 2018, 6(2), 14; https://doi.org/10.3390/machines6020014 - 02 Apr 2018

Cited by 7 | Viewed by 5065

Abstract

In face milling, the roughness of the machined surface varies due to the movement of the cutting edge. Changes in roughness parameter values in the axis of rotation (symmetry plane) have been examined at a constant depth of cut for symmetrical milling. In [...] Read more.

In face milling, the roughness of the machined surface varies due to the movement of the cutting edge. Changes in roughness parameter values in the axis of rotation (symmetry plane) have been examined at a constant depth of cut for symmetrical milling. In this paper, the effect of increasing feed per tooth on the topography of the surface is studied in fly-cutting and in multi-point face milling. The study takes into account the axial run-out of the inserts. Theoretical roughness values were modelled, the real values were tested in experiments and in both cases the impact of the run-out of the cutting edges and the change of the chip cross-section were also taken into account. Based on the performed experiments it can be stated that the accuracy of the introduced roughness prediction method increases with the increase in feed and therefore the application of the method in the case of high-feed milling is particularly effective. The results have also shown that the run-out of the insert significantly effects the roughness of the milled surfaces and therefore the measurement and minimization of these setting errors is essential. Full article

(This article belongs to the Special Issue Precision Machining)

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10 pages, 5880 KiB

Open AccessArticle

Comparative Analysis of Machining Procedures

by Janos Kundrak, Viktor Molnar and Istvan Deszpoth

Machines 2018, 6(2), 13; https://doi.org/10.3390/machines6020013 - 28 Mar 2018

Cited by 5 | Viewed by 3590

Abstract

The in-depth analysis of cutting procedure is a topic of particular interest in manufacturing efficiency because in large-scale production the effective use of production capacities and the revenue-increasing capacity of production are key conditions of competitiveness. That is why the analysis of time [...] Read more.

The in-depth analysis of cutting procedure is a topic of particular interest in manufacturing efficiency because in large-scale production the effective use of production capacities and the revenue-increasing capacity of production are key conditions of competitiveness. That is why the analysis of time and material removal rate, which are in close relation to production, are important in planning a machining procedure. In the paper three procedures applied in hard cutting are compared on the basis of these parameters and a new parameter, the practical parameter of material removal rate, is introduced. It measures not only the efficiency of cutting but also that of the whole machining process because it includes the values measured by time analysis as well. In the investigations the material removal rate was analyzed, first on the basis of geometrical data of the component. After that different machining procedures (hard machining) were compared for some typical surfaces. The results can give some useful indications about machining procedure selection. Full article

(This article belongs to the Special Issue Precision Machining)

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14 pages, 4212 KiB

Open AccessArticle

Precision CNC Machining of Femoral Component of Knee Implant: A Case Study

by Angelos P. Markopoulos, Nikolaos I. Galanis, Nikolaos E. Karkalos and Dimitrios E. Manolakos

Machines 2018, 6(1), 10; https://doi.org/10.3390/machines6010010 - 02 Mar 2018

Cited by 14 | Viewed by 8774

Abstract

The design and manufacturing of medical implants constitutes an active and highly important field of research, both from a medical and an engineering point of view. From an engineering aspect, the machining of implants is undoubtedly challenging due to the complex shape of [...] Read more.

The design and manufacturing of medical implants constitutes an active and highly important field of research, both from a medical and an engineering point of view. From an engineering aspect, the machining of implants is undoubtedly challenging due to the complex shape of the implants and the associated restrictive geometrical and dimensional requirements. Furthermore, it is crucial to ensure that the surface integrity of the implant is not severely affected, in order for the implant to be durable and wear resistant. In the present work, the methodology of designing and machining the femoral component of total knee replacement using a 3-axis Computer Numerical Control (CNC) machine is presented, and then, the results of the machining process, as well as the evaluation of implant surface quality are discussed in detail. At first, a preliminary design of the components of the knee implant is performed and the planning for the production of the femoral component is implemented in Computed Aided Manufacturing (CAM) software. Then, three femoral components are machined under different process conditions and the surface quality is evaluated in terms of surface roughness. Analysis of the results indicated the appropriate process conditions for each part of the implant surface and led to the determination of optimum machining strategy for the finishing stage. Full article

(This article belongs to the Special Issue Precision Machining)

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10 pages, 4652 KiB

Open AccessArticle

The Dimensional Precision of Forming Windows in Bearing Cages

by Marius Rîpanu, Gheorghe Nagîţ, Laurenţiu Slătineanu and Oana Dodun

Machines 2018, 6(1), 9; https://doi.org/10.3390/machines6010009 - 01 Mar 2018

Cited by 1 | Viewed by 5781

Abstract

In the case of double row tapered roller bearings, the windows found in bearing cages could be obtained using various machining methods. Some such machining methods are based on the cold forming process. There are many factors that are able to affect the [...] Read more.

In the case of double row tapered roller bearings, the windows found in bearing cages could be obtained using various machining methods. Some such machining methods are based on the cold forming process. There are many factors that are able to affect the machining accuracy of the windows that exist in bearing cages. On the dimensional precision of windows, the clearance between punches and die, the work stroke length, and the workpiece thickness could exert influence. To evaluate this influence, experimental research was developed taking into consideration the height and the length of the cage window and the distance between the contact elements of the cage. By mathematical processing of the experimental results, empirical mathematical models were determined and analyzed. The empirical models highlighted the intensity of the influence exerted by the considered forming process input factors on the dimensional precision of the windows obtained in bearing cages. Full article

(This article belongs to the Special Issue Precision Machining)

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9 pages, 4195 KiB

Open AccessArticle

Numerical and Experimental Characterization of a Railroad Switch Machine

by Dario Croccolo, Massimiliano De Agostinis, Stefano Fini, Giorgio Olmi and Francesco Robusto

Machines 2018, 6(1), 6; https://doi.org/10.3390/machines6010006 - 17 Feb 2018

Cited by 1 | Viewed by 4344

Abstract

This contribution deals with the numerical and experimental characterization of the structural behavior of a railroad switch machine. Railroad switch machines must meet a number of safety-related conditions such as, for instance, exhibiting the appropriate resistance against any undesired movements of the points [...] Read more.

This contribution deals with the numerical and experimental characterization of the structural behavior of a railroad switch machine. Railroad switch machines must meet a number of safety-related conditions such as, for instance, exhibiting the appropriate resistance against any undesired movements of the points due to the extreme forces exerted by a passing train. This occurrence can produce very high stress on the components, which has to be predicted by designers. In order to assist them in the development of new machines and in defining what the critical components are, FEA models have been built and stresses have been calculated on the internal components of the switch machine. The results have been validated by means of an ad-hoc designed experimental apparatus, now installed at the facilities of the Department of Industrial Engineering of the University of Bologna. This apparatus is particularly novel and original, as no Standards are available that provide recommendations for its design, and no previous studies have dealt with the development of similar rigs. Moreover, it has wide potential applications for lab tests aimed at assessing the safety of railroad switch machines and the fulfilment of the specifications by many railway companies. Full article

(This article belongs to the Special Issue Precision Machining)

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21 pages, 12022 KiB

Open AccessArticle

A Methodology for the Lightweight Design of Modern Transfer Machine Tools

by Dario Croccolo, Omar Cavalli, Massimiliano De Agostinis, Stefano Fini, Giorgio Olmi, Francesco Robusto and Nicolò Vincenzi

Machines 2018, 6(1), 2; https://doi.org/10.3390/machines6010002 - 14 Jan 2018

Cited by 14 | Viewed by 4870

Abstract

This paper deals with a modern design approach via finite elements in the definition of the main structural elements (rotary table and working unit) of an innovative family of transfer machine tools. Using the concepts of green design and manufacture, as well as [...] Read more.

This paper deals with a modern design approach via finite elements in the definition of the main structural elements (rotary table and working unit) of an innovative family of transfer machine tools. Using the concepts of green design and manufacture, as well as sustainable development thinking, the paper highlights the advantages derived from their application in this specific field (i.e., the clever use of lightweight materials to allow ruling out high-consumption hydraulic pump systems). The design is conceived in a modular way, so that the final solution can cover transfers from four to 15 working stations. Two versions of the machines are examined. The first one has a rotary table with nine divisions, which can be considered as a prototype: this machine has been studied in order to set up the numerical predictive model, then validated by experimental tests. The second one, equipped with a rotary table with 15 divisions, is the biggest of the range: this machine has been entirely designed with the aid of the previously developed numerical model. The loading input forces for the analyses have been evaluated experimentally via drilling operations carried out on a three-axis CNC unit. The definition of the design force made it possible to accurately assess both the rotary table and the working units installed in the machine. Full article

(This article belongs to the Special Issue Precision Machining)

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