Machining Damage Research Articles

FMEA tool to analysis of blow molding machine damage

Machine performance in industry has a vital role in the production floor. The machine operates smoothly will support the achievement of production targets. One sector produces packaging products made based on plastic experiencing a failure production process due to the frequent stopping of the Blow Molding Machine. Fishbone diagram and Failure Mode and Effect Analysis (FMEA) is used to find information about the factors cause the Blow Molding Machine to stop. Fishbone diagram is used to determine the factors cause the failure of the Blow Molding Machine in running the production process. FMEA is used to identify the factors causing loss and determine the priority level of risk based on the RPN value. The mold damage factor has the highest RPN value. Mold failure is most significant cause of Blow Molding Machine stops operating. The mold is damaged when stored in the spare part warehouse due to crushed by a material made of metal. Mold is stored in an unsuitable location. Analysis using a fishbone diagram to determine the root of the problem handled.

Effects of Voltage Interharmonics on Cage Induction Motors

In a power system, the voltage waveform usually contains harmonics and sometimes interharmonics, often defined as components of frequency greater than the fundamental voltage component but not of its integer multiple. Previous studies have reported a minor effect of voltage interharmonics on a cage induction machine. This paper reveals their extraordinary harmfulness for induction motors. Namely, voltage interharmonics may cause high vibration, which can result in machine damage. In addition, interharmonics can lead to torque pulsations corresponding to the natural frequency of the first elastic mode. Consequently, possible torsional resonance may cause destruction of a power train. In this study, the results of investigations on undesirable phenomena due to interharmonics are presented for seven motors with a rated power 3 kW–5.6 MW.

Failures and Reliability in Hawts Operating in Mountainous Areas, Open Sea and in Harsch Climate Sites

Recently, offshore wind plants, as Horn’s Riv one, have reached a remarkable interest and development. In these sites, HAWT’s blades experiment corrosion, erosion and fouling and, at higher latitudes, icing conditions too, as in mountainous areas and in harsch climate sites. The operative conditions may influence the machine damages and they may occur as consequence of erosion, corrosion, fouling, icing, exfoliation caused by the above mentioned environmental conditions. The paper reports about data collection about failures occurred to HAWTS operating in offshore, mountainous and harsch climate sites in last ten years. Particularly, the damage occurred to blades, gears and bearings have been examined and the consequences analysed. The occurred failures are examined and the reliability of WTGs is assessed by appropriate models and analysis. The results are com pared to literature data and they may be very useful in programmable maintenance and in predictable one. Reliability analysis may be also useful to increase energy production.

Virtual reality training platform for a computer numerically controlled grinding machine tool

In-depth training of machine tool (MT) operators is crucial to avoid machine damage due to faulty operation. However, machine-hours are costly and during the training, the MT is unavailable for regular production purposes. Here, virtual real-size models offer a solution by providing basic operation principles to future operators. In this context, it is yet unknown whether a virtual teaching enhanced by real walking is similar to a real teaching scenario regarding the learning efficiency and long-term memory retention. This paper describes a study comparing the learning efficiency of a virtual training session with traditional instructions on a real MT. The learning success of both training groups is objectively and subjectively assessed on a real MT a week later. In this assessment, the task completion time and the number of errors are recorded. We observed that the virtually taught group slightly outperformed trainees taught in reality regarding both objective measurements.

The Influence of Surface Condition on the Electrochemical Properties of ASTM F138 Steel for Biomedical Applications

The aim of this paper was to determine the influence of machining parameters on the surface layer, and consequently on the electrochemical properties, of ASTM F138 austenitic stainless steels. Eight different surface conditions were generated in cylindrical samples by turning and polishing. The surface was characterized by surface roughness Ra and Rt, Vickers microhardness and microstructural characteristics. Cyclic voltammetric tests were performed to evaluate the potential of repassivation and pitting. The surfaces were analyzed by Scanning Electron Microscopy after the electrochemical tests were performed. The cutting parameters were identified to have a significant influence, and the feed rate was as influential as the depth of cut. The use of polishing alone is not sufficient to ensure that a surface has good surface integrity. Even with the polishing application, usually used to produce prostheses, a significant reduction in corrosion resistance occurs if care is not taken to minimize surface machining damage. Corrosion resistance is lower and pitting nucleation is higher in the samples with no polishing and with more severe machining parameters. The tests indicated that softer machining parameters can contribute to an increase in the life of implantable components, reducing the probability of localized corrosion, as well as improving the mechanical properties of prostheses.

Analisis Penyebab Kerusakan Mesin Produksi Kayu Lapis

PT. Sama Al-Tanmiah is a company engaged in the semi-finished plywood production industry. Semi-finished raw materials are further processed according to the needs of the buyer, the cause of damage is due to poor maintenance and deteriorating component quality. This research was conducted to determine the origin of the causes of damage to the production machine at PT. Same Al-Tanmiah. Retrieval of data obtained by means of interviews, observation and requesting secondary data for 6 months of production, for data processing using Fault Tree Analysis and Failure Mode and Effect Analysis. The data obtained from the company enters into data management. The next stage will be a fault tree image analysis using Microsoft Visio and weighting to the three production machines using Microsoft Excel. The results of the researchers obtained the root of the fault tree and the value of the RPN with weighted machine damage. Improvement of management and standard operating procedures (SOP).

Multi-scale analysis of the generated damage when machining pockets of 3D woven composite for repair applications using abrasive water jet process: Contamination analysis

Repair of damaged aircraft structural parts is a regular maintenance activity carried out to preserve airworthiness while being economically viable. Conventional repair techniques used have negative impact on the repair quality and environment due to dust emission. For eliminating aforementioned problem, this study investigates controlled depth abrasive water jet (AWJ) milling for repair procedure of 3D woven CFRP composite structures used in the new aircraft engine developed by Safran Aircraft Engines. The aim is to identify and quantify the damage and surface contamination induced by AWJ milling. For this, the influence of milling parameters on the damage and surface contamination is investigated through full factorial experimental study. Several characterisation techniques like 3D optical profilometry, Scanning Electron Microscopy and X-ray tomography combined with image processing were used for a multi-scale analysis of the machined surface damage and contamination. In fact, the machining quality was quantified using an innovative criterion called “crater volume” (Cv). The obtained results have shown surface contamination by embedded abrasive particles and presence of bare and broken fibres, cracks, craters. The results show that the rate of contamination is influenced by the jet pressure and the scan step and the Cv is influenced by the jet exposure time.

Kewenangan Pemerintah Daerah dalam Mengendalikan Pembangunan Kawasan Bandar Udara

Aviation safety and security is our shared responsibility. Accidents and incidents caused by kite games or other similar games can result in casualties, machine damage and weaken the level of compliance. I Gusti Ngurah Rai Airport Flight Operational Safety Area is air, land and water space with a radius of 15 km from the runway at I Gusti Ngurah Rai Airport. The plane that was flown by SYD - DPS was not allowed to land because of a kite near the end of Runway 27 so that my plane had to spin around. The research objective is to study and analyze regional arrangements and the authority of local governments in controlling the development of the airport area. This research uses a normative type of research, by examining library materials by studying and examining theories of concepts, as well as regulations relating to problems. The results showed that the Airport Flight Operations Safety Zone Arrangement was stipulated based on the Government Regulation on aviation security and safety, which stipulates that airport operators are obliged to protect the airport environment in order to avoid disturbances that slow down flights. The authority of a regional government in controlling the flight area is to organize spatial planning in its area while still understanding the rights that people have in accordance with applicable regulations.

Assessment of rotor blades stationarity condition based on differences in phase shifts

Important problem of turbomachinery maintenance is evaluation of blades condition. As the rotating speeds become higher and higher, the blades are exposed to more and more severe failures, such as ruptures, creep deflection, high-cycle fatigue, oxidation, erosion, rubbing, wear, foreign object damage. If appear, these negative factors will change the strength parameters of the blades, lead to machine damage, and finally result in a serious accident. Therefore, efficient methods of blades condition evaluation are needed, and even minimal improvements of known diagnostics techniques may give a chance to detect a failure, and warn the staff, before the advancement of this failure becomes serious.In the paper an extension of the previously developed method based on differences in phase shifts of measurement signals is proposed, and experimentally tested. An extended definition of diagnostic thresholds is introduced, and two different diagnostic states are specified. These are technical condition and stationarity condition of a machine. It is demonstrated that only simultaneous analysis of these two conditions assesses the actual blades condition properly, and gives rationale to take a decision about a potential overhaul of the machine.

Early fault detection of single-point rub in gas turbines with accelerometers on the casing based on continuous wavelet transform

The diagnosis of rotor-casing rub, one of the most common malfunctions in rotating machinery, is usually straightforward in machines equipped with proximitors measuring relative rotor-casing displacement. However, constructive reasons, aeroderivative gas turbines are frequently equipped with accelerometers instead of proximitors. Since these turbines are increasingly used in many industrial applications, this poses substantial maintenance and safety problems. In this work, we apply a properly designed method based on Continuous Wavelet Transform (CWT) to the detection of early single–point rub in gas turbines by means of accelerometers on the machine casing. This procedure is validated on an experimental rotor rig with a flexible cylindrical casing. With this method we expect to prevent machine damage or failure by supplying a very clear picture of rotor-casing rub from the very onset. This is monitored under diverse conditions with accelerometers on casing points and with proximitors assembled between rotor shaft and casing. The acceleration signals collected are then post-processed and analyzed using the Discrete Fourier Transform (DFT) and the proposed CWT-based method. The signal post-processing parameters of the signal post-processing were adjusted with the help of a computational model of the experimental rig. We prove that an adequately designed CWT-based algorithm outlines the signal features that better characterize single-point rub, and unlike the DFT it is sensitive to an outbreak of rub within a time series.

A novel reverse helical milling process for reducing push-out delamination of CFRP

When drilling Carbon fiber reinforced plastic (CFRP), delamination can be found at hole-exit frequently, which is known as typical machining damage and would weaken the mechanical strength of finished components. The occurrence of delamination is regarded as the consequence of the deformation of uncut material that caused by thrust force. This study aims to propose a new reverse helical milling (RHM) method to restrain the delamination, in which, the principle of reducing the deformation extent of uncut material is via material rigidity enhancement. Firstly, two-dimensional analysis was used to contribute the avoidance of push-out delamination during CFRP drilling. Then, considering both CFRP and metal-CFRP stacks, an idea of reversing feed direction of cutting tool is processed, which enhances the rigidity of uncut material by means of either increasing the uncut thickness or providing an equivalent back-up without employing any extra facility. In order to realize reverse cutting without changing the original position of both workpiece and machine equipment, special cutting tools and detailed operation steps are designed. Finally, confirmatory experiments were carried out and the results demonstrated that RHM will neither deteriorate the existing delamination nor generate new ones and as a result, the push-out delamination was effectively reduced.

Ultra-short pulse simulation for characterising oxide layer formation on stainless steel during μECM

Electrochemical machining is a controlled metal shaping process based on anodic dissolution performed by the electrode reactions. When pulse signals, in the micro-second or less range, are combined with a small inter-electrode gap, the process is referred to as Micro-Electro-Chemical machining or μECM. The application of using nano-second/micro second pulses for μECM for certain passivation metals can be very limited by the formation of an oxide layer that prohibits the penetration of ultra-short pulse durations due to the capacitive effect of the oxide layer. This paper will present findings from the development of a μECM numerical model that incorporates an advanced hybrid time stepping approach for representing nano-second pulse interactions with the physical phenomena of the electrolytic environment associated with μECM, thereby enabling the characterisation of the capacitive model of the formed oxide barrier layer. Experimental work was conducted using nano and micro-second pulses on the machining of 18CrNi8 and copper using NaNO3 electrolyte. The μECM simulation model contributed to quantifying the lack of faradic machining of 18CrNi8 that was experimentally observed. A particular solution, believed to be effective in breaking through the oxide film, is to directly pre-polarize the layer by super imposing a DC signal prior to the ultra-short pulses, such that its capacity has been already loaded when the short pulse signal is applied. However, too long of a DC signal application time can lead to machining damage. Through the development of an ultra-short pulse simulation model, this work has established, that we can numerically determine an optimal DC signal duration necessary to load the oxide layer just enough for facilitating anodic dissolution during physical μECM process, thus minimising machining damage.

Penentuan Interval Waktu Perawatan Mesin Blowing dan Mesin Filling Menggunakan Teori Reliability dan Model Age Replacement (Studi Kasus pada PT. XYZ)

Engine performance will decrease when it is operated continuously so that maintenance is needed. Improper maintenance time intervals can reduce engine reliability and still causes machine damage suddenly. Therefore, maintenance time intervals must be determined precisely. This study aims to determine the engine maintenance time intervals using Reliability Theory and Age Replacement Model, then calculate the total maintenance cost. The result shows that the application of new maintenance time interval increases machine reliability.

The implementation of preventive maintenance using machine damage analysis: a case study of power plant machine

Maintenance has an important role in supporting the manufacturing process. The irregular maintenance in the industry can cause downtime and discontinue the production process. The importance of maintenance can be seen in PT PLN Sektor Tello, one of the industries which supply the electricity in Makassar. Since the electricity contributes to the huge impact on the life’s sector, there should be preventive maintenance to all of the machine components in order to ensure that the components can run well and reduce the impact. To analyze the PT PLN Sektor Tello machine’s performance, the researchers use the Failure Mode and Effect Analysis (FMEA) to identify the type of failures and recommend the maintenance plan. The FMEA’s result will be used to calculate the RPN (Risk Priority Number) for each failure and provide the recommendations that will be conducted at maintenance when the RPN’s value is equal or more than 125. By using the FMEA, we found three types of machine failures, such as the component’s leakage, the machine’s knock, and the broken component.

THE EFFECT OF EXCESSIVE SETTING TIME, LONG DAMAGE OF THE MACHINE, TIME OF PACKAGING PACKAGES STOPPED TO PRODUCTION OPERATIONAL COSTS: STUDY IN LINE 8A PT XYZ FARMA Tbk

This study aims to determine the effect of excess machine setting time, machine breakdown time, time for packaging lines to stop, on production operating costs and which factors are most dominant in influencing production operating costs. This research uses a quantitative descriptive method approach. The place of research is at PT. XYZ Farma on line 8A. The research sample consisted of 22 data records from a population of 450 data records. Data collection techniques are observation techniques, event recording and documentation. The results showed the influence of excessive setting time, machine damage time, packaging line time stalled against operational costs of production. This is demonstrated by using AMOS, the value of C.R (Critical Ratio) exceeds the critical value ± 1,717. The value of C.R for each variable is the excessive machine setting time, the length of time the machine is damaged, and the time of the packaging line has stalled towards the operational cost of production is 2,850; 10, 913; 5,330.
 Based on AMOS Standardized Regression Weight Output statistical calculations show that the duration of damage to the machine provides the greatest contribution in increasing the operational costs of production. This is indicated by the estimated coefficient value of the largest engine damage time which is 82.1%. So it can be concluded that the influence of excess engine setting time, machine breakdown time and time of the packaging line has stalled to the operational costs of production with the variable length of engine damage giving the greatest contribution.

Modeling and experimental validation on temperature diffusion mechanism in high-speed bone milling

• High-speed bone milling heat is mainly caused by the friction effect between the bone chip and the cutter tooth. • Cutting edge temperature is determined by the equivalent static plane heat source. • The bone material temperature distribution is obtained according to the constant temperature moving heat source. • The thermal damage factors could be calculated based on the temperature diffusion mechanism model in bone milling. In orthopedic surgery, thermal damage of bone affects the accuracy of the prosthesis fixation and delays the postoperative recovery time. In order to avoid thermal damage in high-speed bone machining, it is necessary to establish an effective relationship among machining parameters, tool parameters, and temperature distribution of bone materials. Based on the characteristics of bone material and high-speed processing, this study proposes a novel temperature diffusion mechanism model (TDMM) in high-speed bone milling. According to the model, heat during high-speed bone milling is mainly generated by the friction effect between the bone chip and the cutter tooth. Then the cutting edge temperature of the milling cutter is determined by the equivalent static heat source, and cutting edge is regarded as a moving heat source with constant temperature. Under the action of the moving heat source, the bone material temperature distribution was determined. Moreover, the degree of thermal damage of bone materials under different machining and tool parameters was evaluated. Next, a high-speed bone milling experiment platform was established, in order to obtain accurate cutting edge temperature and bone material temperature. According to a large number of experimental measurements, the theoretical prediction temperature values of the cutting edge and bone materials were found to be within the reasonable error range of experimental measurements. The proposed model was proved to reasonably predict the temperature of the cutting edge and bone materials in high-speed bone milling. Experimental results indicate that the processing methods, tool diameter, cooling method, and cutting layer have a noteworthy impact on bone material distribution in bone milling. Spray cooling method can reduce the bone material temperature significantly. And the bone material temperature outside the cutting layer can be greatly lower than that in the cutting layer. This study also indicates that according to the TDMM, it is convenient for surgeons to select the appropriate machining parameters, and for engineers to optimize tool design.

Karst geology and mitigation measures for hazards during metro system construction in Wuhan, China

Karst geology is widely distributed in China; the great differences in natural conditions bring it an array of characteristics in different regions. There is a huge area of the buried karst in Wuhan, exhibiting a unique, but complicated engineering geological environment. This paper summarizes the geological conditions in Wuhan, with special focus on its karst geology. At present, a total of six karst belts have been detected, and they were divided into five structure types. For shield tunnelling in karst region, some problems such as water ingress or mud inrush, partial ground collapse, damage or failure of shield machine, and metro operation and management issues may be raised as a result of the activity of the karst geology. To prevent occurrence of possible hazards, a series of countermeasures suggested for hazard and risk mitigation were discussed in this paper. A case history, where the study section belongs to the Wuhan metro line 6, is referred to evaluate effectiveness of the adopted treatment measures. The feedbacks demonstrated that water ingress was successfully avoided, and ground deformation was effectively controlled in the study section throughout the construction phase. This study can provide significant reference information and experience for metro tunnel constructed in karst region.

Effect of bur selection on machining damage mechanisms of polymer-infiltrated ceramic network material for CAD/CAM dental restorations

The surface and edge quality of polymer-infiltrated ceramic network material (PICN) in CAD/CAM milling and clinical adjusting is crucial to restorative successes. The paper reports on PICN responses to diamond and tungsten carbide machining with respect to machining forces and frictions, material removal mechanisms, surface quality and edge integrity. A force sensor together with a high-speed data acquisition system was used to measure machining forces. Scanning electron microscopy was applied to reveal bur wear and debris adhesion, and machining-induced surface and edge chipping damage. The results show two distinct removal mechanisms of PICN in which tungsten carbide machining was dominated by friction-induced ductile deformation and normal pressing of the material while diamond machining was controlled by the penetration-induced fracture. These mechanisms were reflected by significantly higher tangential (or frictional) forces and coefficients of friction in tungsten carbide machining than in diamond machining (p < 0.05). The ductile removal in tungsten carbide machining yielded more smoother areas and much less edge chipping damage in PICN. The fracture mode in diamond machining broke the ceramic and polymer networks in PICN, resulting in more fractured and pulverized areas with 6–7 times higher roughness and much more severe edge chipping damage in PICN. Thus, for better surface and edge quality, tungsten carbide burs are superior than diamond burs and recommended for surface finishing and adjusting while diamond burs are the good choice for rapid material removal in both CAD/CAM milling and clinical adjusting. However, high material removal rate-induced high tangential (or frictional) forces in tungsten carbide machining limited the bur usage for rapid oral adjusting. This paper also compared the influence of PICN microstructure on the machinability with CAD/CAM glass ceramics.

Study on the design and cutting performance of stepped bi-directional milling cutters for hole making of CFRP

During hole making of carbon fiber reinforced plastic (CFRP) by helical milling, the tool wear is a main factor in machined surface damage, being unable to guarantee machining quality and accuracy, and restricting the improvement of hole making efficiency. In order to prolong the service life of cutters, this paper has carried out the research into the design, manufacture, and cutting performance of stepped bi-directional milling cutters, combining with hole making of CFRP by bi-directional helical milling. By the method of differential geometry, the geometric model of the profile shape and the mathematical model of the helical edge are established of the stepped bi-directional milling cutter. Additionally, based on the transformation matrix between grinding wheel and workpiece coordinates of any point, the track equation of grinding wheel is derived from grinding the side edge helical groove of the stepped bi-directional milling cutter. What is more, the grinding process and accuracy are measured about the designed stepped bi-directional milling cutter. The experiment of CFRP holes made by bi-directional helical milling is designed, and the experimental results show that the axial cutting force of stepped bi-directional milling cutters is smaller and fluctuates more gently than that of symmetrical bi-directional milling cutters in the backward milling. Especially, the former has better distributed and slower flank wear on the backward cutting edge, and better machining quality than the latter.

Development of key components of wheel tractor driving simulator based on desktop virtual reality

The wheel tractor driving simulator was developed by using desktop virtual reality technology to solve the problems of short training times and complex operation for drivers, which led to machine damage and low efficiency when the wheel tractor was used. Firstly, the composition of the tractor driving simulator and its working principle were presented. Secondly, combined with the obtained parameters and operation requirements, the key components of the wheeled tractor driving simulator were designed. Finally, the high-degree simulation of the wheeled tractor driving simulator was verified by comparing the parameters of the key components of the real tractor with those of the wheeled tractor driving simulator. The test results showed the stroke angle and feedback force of the simulator were basically the same as that of the real tractor and they had the same trends. Therefore, the key components of the wheeled tractor driving simulator designed in this paper can simulate the driving body sense and operational functions of real tractors. The development of a driving simulator is of great significance to train unqualified drivers, improve training efficiency and reduce training cost.