Machined Surface Finish Research Articles

FEASIBILITY STUDY OF ULTRASONIC FREQUENCY APPLICATION ON FDM TO IMPROVE PARTS SURFACE FINISH

Fuse Deposition Modeling (FDM) offer several advantages such as less expensive material, lack of expensive lasers and allows complex geometry to be built. However, FDM have limitations such as seam lines appear between layers and excess material residue, leading to surface roughness and poor finish. Ultrasound has been applied in various conventional machining process and shows good machined surface finish. However, from the literature review, it was found there is no investigation made on the application of ultrasound for Additive Manufacturing (AM) especially for FDM. This paper presents an adaptive approach to improve surface finish of FDM sample by applying ultrasonic vibration. The papers discuss the result of the surface finish of test piece printed via a desktop FDM system whereby an ultrasound device that was securely mounted onto the platform during printing process. Frequency that was used in the experiment is 11, 16 and 21 kHz with acrylonitrile butadiene styrene (ABS) material. Optical microscope with the aid of pro VIS software version 2.90 was used to measure the surface roughness of the four samples printed with a vibration in the above specified frequency. It was found that a 21 kHz frequency applied to the FDM process achieved the best surface finish due to less surface defects found and thickness had finer layers being produced. The results from this study could potentially be applied to other AM system such as the selective laser sintering, electron beam machining and stereolithography. The new data on effects of ultrasonic FDM technique and machining parameter for achieving improved surface finish has potential benefit to be used in various industries such as automotive, consumer, medical, sports, etc to produce prototypes or customized end used product or part. The data will benefit in term of product design and development elimination of manual post processing. Further study that could be done is to use different types of material such as polyactic acid (PLA) or composite material.

Optimization of Tool Wear Rate during Electro Discharge Machining of NiTi Alloys Using Taguchi Method

NiTi alloys are advance materials which possess superior properties such as pseudoelasticity, shape memory effect, high wear resistance, high corrosion resistance and high strength. NiTi alloys causes serious tool wear, hardening of the machined surface and poor surface finish. Electro discharge machining (EDM) is an unconventional machining process which demonstrates high capability to machine NiTi alloys. Present work emphasis on investigating the effect of EDM process parameters on the tool wear rate. Gap current, pulse on time and pulse off time were considered at three levels as input process parameters along with electrical conductivity of workpiece and tool electrode at two levels. Taguchi L36(22x 33) mixed orthogonal array was utilized to design the experimental plan. Based on the statistical analysis at 95% confidence level it was found that tool electrical conductivity, gap current and pulse on time are the most significant factors that influence the tool wear rate. At optimal setting of parameters the predicted value of tool wear rate obtained was 0.00811 mm3/min.

Study of influence of traverse speed and abrasive mass flowrate in abrasive water jet machining of gemstones

Abrasive water jet (AWJ) machining is characterized by its versatility, i.e., it can be applied to a wide variety of materials. Currently, one important application is for manufacturing gem artifacts, especially agate, which is the largest gemological material produced in the state of Rio Grande do Sul. However, one of the main obstacles to its popularization is the cost associated with the process, due to the high abrasive consumption required for a good quality surface finish. In this sense, this research paper presents a study of the influence of the main process parameters (traverse speed and abrasive mass flow rate) on the surface finish of agates machined by AWJ. The experimental procedure used three different traverse speeds, four abrasive mass flow rate in two different thicknesses of agate’s plates. Surface roughness and angle of striation marks were observed for different depths from the jet entrance surface. Results were analyzed using analysis of variance (ANOVA). Through the study, it was found that the machined surface finish varies according to the depth from the entrance surface of the abrasive jet. Also, it was concluded that the surface finish of the machined surface by AWJ (surface roughness and striation marks) of the agate’s plates machined by AWJ exhibits similar results for both thicknesses tested. ANOVA showed that the traverse speed is more significant than abrasive mass flow rate for the material studied with respect to the surface finish. Thus, for a small material thickness, it is possible to use high traverse speed and low abrasive mass flow rate which makes the process more economical.

Experimental Setup for Ultrasonic-Assisted Desktop Fused Deposition Modeling System

Fused deposition modeling (FDM) is an additive manufacturing (AM) process that has been used in various manufacturing fields. However, the drawback of FDM is poor surface finish of parts produced, leading to surface roughness and requires hand finishing. In this study, ultrasonic technology will be integrated into a desktop FDM system.Ultrasound has been applied in various conventional machining processes and shows good machined surface finish. However, very little research regarding the application of ultrasound to AM has been carried out. Our previous research found that the extrusion nozzle of the FDM system could withstand the high vibration transmitted at 40 kHz of frequency from an ultrasonic transducer. The aim of this paper is to discuss three novel setups of using ultrasound devices attached to a desktop FDM system to study its feasibility to improve the surface finish of parts produced. A comparative study was made and it was found that the second setup (Concept 2) was most suitable due to its safety and reliability aspects.

Effect of cutting tool lead angle on machining forces and surface finish of CFRP laminates

Abstract Machining is one of the most practical processes for finishing operations of composite components, allowing high-quality surface and controlled tolerances. The high-precision surface milling of carbon fiber-reinforced plastics (CFRP) is particularly applicable in the assembly of complex components requiring accurate mating surfaces as well as for surface repair or mold finishing. CFRP surface milling is a challenging operation because of the heterogeneity and anisotropy of these materials, which are the source of several types of damage, such as delamination, fiber pullout, and fiber fragmentation. To minimize the machining problems of CFRP milling and improve the surface quality, this research focuses on the effect of multiaxis machining parameters, such as the feed rate, cutting speed, and lead angle, on cutting forces and surface roughness. The results show that the surface roughness and cutting forces increase with the feed rate, whereas their variations are not uniform when changing the cutting speed. Generally, a lower surface roughness was achieved by using a lower cutting feed rate (0.063 mm/rev) and higher cutting speeds (250–500 m/min). It was also found that the cutting forces and surface roughness vary significantly and nonlinearly with the lead angle of the cutting tool with respect to the surface.

Machining mechanism research of glass by discrete element method

The discrete element method (DEM) is applied to glass micromachining in this study. The indentating, cutting, micro milling process are simulated by the established DEM matching the main mechanical properties of glass in three sets of standard tests. Results show that the vertical damage depth is prevented from reaching the final machined surface in cutting process. Tool rake angle is the most remarkable factor influencing the chip deformation and cutting force. The final machined surface is determined by the minimum cutting thickness per edge. Different cutting thickness, cutter shape and spindle speed largely affect the mechanism of glass.

Indirect Model Based Estimation of Cutting Force and Tool Tip Vibrational Behavior in Milling Machines by Sensor Fusion

Real time prediction of cutting tool condition and machined surface finish have been attractive research objectives over the last decades. However, providing practical and reliable solutions is still a demanding task for milling machine tools. One of the most challenging literature goals is to obtain a robust estimation of the cutting forces through indirect sensor measurements since many process and tool related quantities are indirectly linked to cutting forces. Another challenging issue in machining process monitoring and control is prediction of surface finish and quality. As the vibration plays a major role in the surface generation, this can be done by accurate prediction of the vibrational displacements at the tool tip during machining operation. In this paper, a novel model based estimation of cutting force and tool tip acceleration is designed and tested based on data fusion of different sensors measurements. In this context, two sensors (piezoelectric accelerometer and eddy-current displacement both mounted inside the spindle structure) have been utilized to acquire the experimental signals over a wide range of frequencies.In order to predict the above mentioned quantities, an optimal state estimator based on Kalman Filter (KF) is used. The models have been obtained by system identification method based on experimental measurements performed on a machine tool. The model based estimator is fed by real data. The results show that the estimation of the impulse force and tool tip acceleration can be achieved accurately in low and high frequency ranges by assigning different weights to the measurement sensors.

Research on Stability Prediction of the Crankshaft CNC Tangential Point Tracing Grinding

As the key part of internal combustion engines, crankshaft with high efficiency and accuracy processing has always been the target of the engine manufacturer’s pursuit. Grinding is used to obtain the ultimate dimensional accuracy and surface finish in the crankshaft machining. Grinding of the main journals and the pin journals can be accomplished in a single clamping operation by CNC Tangential Point Tracing grinding technology. However, the chatter in the grinding process is harmful to the precision and surface quality. In this paper, stability lobe diagram is developed to predict the grinding chatter. First the dynamic model of Tangential Point Tracing grinding system is established. Then the limit formula of the critical grinding depth is calculated and the stability lobe diagram of the grinding system is presented. Finally, the validation experiments are carried out on the crankshaft grinding machine and the results are consistent with the calculation.

Additive manufacturing in prosthesis development – a case study

Purpose – The purpose of this paper was development of patient-specific femoral prosthesis using rapid prototyping (RP), a part of additive manufacturing (AM) technology, and comparison of its merits or demerits over CNC machining route. Design/methodology/approach – The customized femoral prosthesis was developed through computed tomography (CT)-3D CAD-RP-rapid tooling (RT)-investment casting (IC) route using a stereolithography apparatus (SLA-250) RP machine. A similar prosthesis was also developed through conventional CT-CAD-CAM-CNC, using RP models to check the fit before machining. The dimensional accuracy, surface finish, cost and time involvement were compared between these two routes. Findings – In both the routes, RP had an important role in checking the fit. Through the conventional machining route, higher-dimensional accuracies and surface finish were achieved. On the contrary, RP route involved lesser time and cost, with rougher surface finish on the prosthesis surface and less internal shrinkage porosity. The rougher surface finish of the prosthesis is favourable for bone ingrowths after implantation and porosity reduce the effective stiffness of the prosthesis, leading to reduced stress shielding effect after implantation. Research limitations/implications – As there is no AM machine for direct fabrication of metallic component like laser engineered net shaping and electron beam melting in our Institute, the metallic prosthesis was developed through RP-RT-IC route using the SLA-250 machine. Practical implications – The patient-specific prosthesis always provides better fit and favourable stress distribution, leading to longer life of the prosthesis. The described RP route can be followed to develop the customized prosthesis at lower price within the shortest time. Originality/value – The described methodology of customized prosthesis development through the AM route and its advantages are applicable for development of any metallic prostheses.

Modelling of surface finish, electrode wear and material removal rate in electrical discharge machining of hard-to-machine alloys

Hard-to-machine alloys are commonly used for industrial applications in the aeronautical, nuclear and automotive sectors, where the materials must have excellent resistance to corrosion and oxidation, high temperature resistance and high mechanical strength. In this present study the influence of different parameters of the electrical discharge machining process on surface roughness, electrode wear and material removal rate have been studied. Regression techniques are employed to model arithmetic mean deviation Ra (μm), peak count Pc (1/cm), material removal rate MRR (mm3/min) and electrode wear EW (%). All these parameters have been studied in terms of current intensity supplied by the generator of the electrical discharge machine I (A), pulse time ti (μs), duty cycle η and open-circuit voltage U (V). This modelling allows us to obtain mathematical data and models to predict that the most influential factor in MRR and Ra is the current intensity and in the case of EW and Pc is the pulse time.

A novel multi-phosphonate surface treatment of titanium dental implants: a study in sheep.

The aim of the present study was to evaluate a new multi-phosphonate surface treatment (SurfLink®) in an unloaded sheep model. Treated implants were compared to control implants in terms of bone to implant contact (BIC), bone formation, and biomechanical stability. The study used two types of implants (rough or machined surface finish) each with either the multi-phosphonate Wet or Dry treatment or no treatment (control) for a total of six groups. Animals were sacrificed after 2, 8, and 52 weeks. No adverse events were observed at any time point. At two weeks, removal torque showed significantly higher values for the multi-phosphonate treated rough surface (+32% and +29%, Dry and Wet, respectively) compared to rough control. At 52 weeks, a significantly higher removal torque was observed for the multi-phosphonate treated machined surfaces (+37% and 23%, Dry and Wet, respectively). The multi-phosphonate treated groups showed a positive tendency for higher BIC with time and increased new-old bone ratio at eight weeks. SEM images revealed greater amounts of organic materials on the multi-phosphonate treated compared to control implants, with the bone fracture (from the torque test) appearing within the bone rather than at the bone to implant interface as it occurred for control implants.

밀링가공에서 효과적인 채터진동 판별을 위한 신호 획득

This paper proposes a method to predict chatter vibration generated in milling processes and to enhance m achining quality and surface finish. Chatter vibration is a common problem in the milling of thin walls and floors. It causes a poor surface finish, or even marks, to appear on the final machined surface. Therefore, an effective method is necessary to predict chatter vibration in machine tools. In this investigation, chatter vibration is measured by an accelerometer, microphone, and Acoustic Emission (AE) sensor in a machining operation. Based on the results of the experiment, a microphone can be applied for the prediction of chatter vibration in milling processes.Received 8 May 2014Revised 20 June 2014Accepted 24 June 2014

English

The objective of this study is to develop a better understanding of the effects of spindle speed, cutting feed rate and depth of cut on the surface roughness and to build a suitable mathematical model. Such an understanding can provide insight into the problems of controlling the finish of machined surfaces when the process parameters are adjusted to obtain a certain responses like surface finish and power consumption. Also, the demand for high quality and fully automated production focuses attention on the surface condition of the product, especially the roughness of the machined surface, because of its effect on product appearance, function, and reliability. For these reasons it is important to maintain consistent tolerances and surface finish. Also, the quality of the machined surface is useful in diagnosing the stability of the machining process, power consumption, MRR, progressive tool wear, cutting tool chatter, etc.

Study on Machining Mechanism of Glass Using Discrete Element Method

The discrete element method (DEM) is applied to glass micromachining in this study. By three standard tests the discrete element model is established to match the main mechanical properties of glass. Then, indentating, cutting, micro milling process are simulated. Results show that the vertical damage depth is prevented from reaching the final machined surface in cutting process. Tool rake angle is the most remarkable factor influencing on the chip deformation and cutting force. The final machined surface is determined by the minimum cutting thickness per edge. Different cutting thickness, cutter shape and spindle speed largely effect on the mechanism of glass.

Envelope Surface Modeling and Tool Path Optimization for Five-Axis Flank Milling Considering Cutter Runout

Cutter runout is a common and inevitable phenomenon impacting the geometry accuracy in the milling process. However, most of the works on tool path planning neglect the cutter runout effect. In this paper, a new approach is presented to integrate the cutter runout effect into envelope surface modeling and tool path optimization for five-axis flank milling with a conical cutter. Based on the geometry model of cutter runout which consists of cutter axis and cutter tilt, an analytic expression of cutter edge combined with four runout parameters is derived. Then the envelope surface formed by each cutter edge is constructed using the envelope theory of sphere congruence. Due to the cutter runout effect, the envelope surfaces formed by the cutter edges are different from each other, and the valid envelope surface is the combination of these envelope surfaces which contribute to the final machined surface. To measure the machining errors, the geometry deviations between the valid envelope surface and the design surface are calculated with the distance function. On the basis of the differential property of the distance function, tool path optimization considering cutter runout is modeled as a mixed-integer linear programming (MILP) problem, which can be solved by the branch-and-bound method. Finally, numerical examples are given to confirm the validity and efficiency of the proposed approach. The results show that the geometry errors induced by runout can be reduced significantly using the proposed method.

Effects of tool overhang on selection of machining parameters and surface finish during diamond turning

In precision machining leading to nano-metric surface finish, selection of the suitable machining parameters is a critical task. To ensure the desired surface quality, one needs to optimally select the machining parametric matrix. Towards this effort, this paper adds another critical parameter in terms of tool overhang. A well-defined set of machining exercises is carried out with different tool overhangs and machining parameters. In this investigation, an attempt has been made to locate the optimum range of tool overhang with minimum tool vibrations. The interaction between tool overhang with other parameters is also thoroughly investigated. Another important focus of this study is to find out the optimum machining parameters for the situations where it is not possible to select an optimum tool overhang. One such situation occurs when a steep concave parabolic surface needs to be fabricated. In this case a large tool overhang has to be selected. Power spectral density distribution analysis of surface roughness for different tool overhangs is performed to find out significant parameters and their degree of contribution to surface roughness. Analysis of variance is also applied to ascertain statistically significant factors contributing to surface roughness. To model the surface roughness, response surface methodology is being used. The model has been verified by conducting a series of experiments and a steep concave parabolic surface is developed by following the predictions of the developed model.

Experimental Study of Traveling Wire Electrochemical Spark Machining of Borosilicate Glass

Machining performance study of newly developed machining processes has always been a challenge to make them industrially viable. Traveling wire electrochemical spark machining (TW-ECSM) is a newly developed hybrid process in the area of nontraditional machining process which can be effectively utilized for difficult-to-cut electrically nonconductive very hard and brittle materials. Present paper discusses the investigations showing the effect of input process variables on material removal rate (MRR) and kerf width (K w) during the cutting of borosilicate glass using self-developed tabletop TW-ECSM setup. The experimental studies are conducted under varying applied voltage, pulse-on time, pulse-off time, electrolyte concentration, and wire feed velocity. The experimental results shows that MRR and K w increase with increase in applied voltage as well as pulse-on time, but these performance characteristics decrease with increase in pulse-off time. MRR and K w increase with increase in electrolyte concentration at certain value (25% wt.) and beyond that value they start to decrease. Moreover the machined kerf width and surface finish were also analyzed by scanning electron microscope (SEM).

Performance Evaluation of Liquid Nitrogen as Coolant in Turning of Al/SiC Metal Matrix Composites (AMMC)

This paper presents the results of an experimental investigation on the turning of Al/SiC (LM-13) composite using Cryogenic Liquid Nitrogen (LN2) as coolant. The influence of machining performance parameters such as cutting force, cutting temperature and surface finish were investigated under wet and cryogenic machining. The results proved that the application of cryogenic LN2 coolant reduced the cutting temperature and the cutting force for about 19 to 30% and 24 to 35% respectively. The surface finish of the machined part is about 10 to 23% better than in the conventional coolant. Thus it was proved that the application of cryogenic coolants reduced the cutting force and temperature which resulted in an appreciable improvement in surface finish in machining of Al/SiC MMC.

Experimental analysis on cutting fluid dispersed with silver nano particles

Cutting fluids play a significant role in machining operations, impact shop productivity, tool life and quality of work. The reduction in the consumption rate of the cutting fluid leads to the minimization of production cost and environmental hazards. This could be achieved by the enhancement of its thermal and tribological properties with the inclusion of suitable additives in the cutting fluid. In recent years various nanoparticles were used as additives in the conventional cutting fluid to enhance its properties. In the present work, silver nanoparticles was synthesized, characterized, dispersed in cutting fluid and experimented in a turning operation. Heat carrying capacities of the cutting fluid, cutting forces during machining process and surface finish of the work piece were assessed by suitable instruments for cutting fluids with and without silver nanoparticles under different machining conditions. From the experimental results, it was observed that inclusion of silver nanoparticles in cutting fluid showed a significant reduction in tool tip temperature, cutting force and surface roughness of the work piece.

Multi-axis tool path generation for surface finish machining of a rapid manufacturing process

This paper proposes a completely automated, integrated tool path planning for the finish machining of freeform surfaces as a part of the hybrid metal additive manufacturing and CNC machining. This planning capability spans from a generation of b-spline freeform surfaces, to surface finish optimisation, to collision detection, to tool path generation. Two scallop height methods have been used to compare the optimal tool path strategy. Both collision detection of a tool with neighbouring surfaces and collision correction for a tool are solved using a novel extension of the bounding box, which uses body diagonal points for computation. This paper proposes a multiple screening technique to improve the computational efficiency of tool path generation calculations.