Prediction of cutting force, tool wear and surface roughness of Al6061/SiC composite for end milling operations using RSM

The results of mathematical modeling and the experimental investigation on the machinability of aluminium (Al6061) silicon carbide particulate (SiCp) metal matrix composite (MMC) during end milling process is analyzed. The machining was difficult to cut the material because of its hardness and wear resistance due to its abrasive nature of reinforcement element. The influence of machining parameters such as spindle speed, feed rate, depth of cut and nose radius on the cutting force has been investigated. The influence of the length of machining on the tool wear and the machining parameters on the surface finish criteria have been determined through the response surface methodology (RSM) prediction model. The prediction model is also used to determine the combined effect of machining parameters on the cutting force, tool wear and surface roughness. The results of the model were compared with the experimental results and found to be good agreement with them. The results of prediction model help in the selection of process parameters to reduce the cutting force, tool wear and surface roughness, which ensures quality of milling processes.     

THE SURFACE INTEGRITY IN MACHINING HARDENED STEEL SKD11 FOR DIE AND MOLD

Milling cutters were evaluated by tool wear, cutting force and vibration. Surface integrity of grinding and milling were investigated by comparing residual stress distributions, metallurgical structure, hardened layer depth and surface roughness. And influence of cutting tool wear on surface integrity was investigated. Experimentations revealed that the preferable surface integrity would be obtained if the proper milling cutter as well as a small wear criterion were adopted to avoid the advent of tempered martensite. The research results pointed out the feasibility of taking milling as the finish machining process instead of grinding in machining hardened steel with high efficiency.     

THE SURFACE INTEGRITY IN MACHINING HARDENED STEEL SKD11 FOR DIE AND MOLD

Milling cutters were evaluated by tool wear, cutting force and vibration. Surface integrity of grinding and milling were investigated by comparing residual stress distributions, metallurgical structure, hardened layer depth and surface roughness. And influence of cutting tool wear on surface integrity was investigated. Experimentations revealed that the preferable surface integrity would be obtained if the proper milling cutter as well as a small wear criterion were adopted to avoid the advent of tempered martensite. The research results pointed out the feasibility of taking milling as the finish machining process instead of grinding in machining hardened steel with high efficiency.     

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.     

Ultrasonic vibration-assisted milling of aluminum alloy

The objective of this paper is to investigate the effects of assisted ultrasonic vibration in the operation of micro end milling. Based upon numerical analysis for the trajectory of a tool tip of a two-flute end mill, it was found that the assisted feed direction ultrasonic vibration can achieve separate-type milling that is different from conventional operation by reasonable parameter matching. To validate theoretical analysis and investigate the influence of ultrasonic vibration on milling process, a slot-milling experiment was conducted on an aluminum alloy work piece. The desired ultrasonic vibration was applied in the feed direction by an ultrasonic vibrator. Through investigating and comparing some experimental results involving cutting force, chip formation, surface topography, surface roughness, and machining dimensional accuracy, the authors found that micro end milling with ultrasonic vibration in the feed direction leads to a pulse-like cutting force and produces uniform small chips. Assisted ultrasonic vibration in the feed direction has a negative effect on the surface roughness of the slot bottom, but a positive effect on the dimensional accuracy of the slot width.     

INDUCTION-HEATED TOOL MACHINING OF ELASTOMERS—PART 2: CHIP MORPHOLOGY,CUTTING FORCES,AND MACHINED SURFACES

ABSTRACT

The induction-heated tool and cryogenically cooled workpiece are investigated for end milling of elastomers to generate desirable shape and surface roughness. Elastomer end milling experiments are conducted to study effects of the cutting speed, tool heating, and workpiece cooling on the chip formation, cutting forces, groove width, and surface roughness. At high cutting speed, smoke is generated and becomes an environmental hazard. At low cutting speeds, induction heated tool, if properly utilized, has demonstrated to be beneficial for the precision machining of elastomer with better surface roughness and dimensional control. Frequency analysis of cutting forces shows that the soft elastomer workpiece has low frequency vibration, which can be correlated to the surface machining marks. The width of end-milled grooves is only 68 to 78% of the tool diameter. The correlation between the machined groove width and cutting force reveals the importance of the workpiece compliance to precision machining of elastomer. This study also explores the use of both contact profilometer and non-contact confocal microscope to measure the roughness of machined elastomer surfaces. The comparison of measurement results shows the advantages and limitations of both measurement methods.     

INDUCTION-HEATED TOOL MACHINING OF ELASTOMERS—PART 2: CHIP MORPHOLOGY, CUTTING FORCES, AND MACHINED SURFACES

The induction-heated tool and cryogenically cooled workpiece are investigated for end milling of elastomers to generate desirable shape and surface roughness. Elastomer end milling experiments are conducted to study effects of the cutting speed, tool heating, and workpiece cooling on the chip formation, cutting forces, groove width, and surface roughness. At high cutting speed, smoke is generated and becomes an environmental hazard. At low cutting speeds, induction heated tool, if properly utilized, has demonstrated to be beneficial for the precision machining of elastomer with better surface roughness and dimensional control. Frequency analysis of cutting forces shows that the soft elastomer workpiece has low frequency vibration, which can be correlated to the surface machining marks. The width of end-milled grooves is only 68 to 78% of the tool diameter. The correlation between the machined groove width and cutting force reveals the importance of the workpiece compliance to precision machining of elastomer. This study also explores the use of both contact profilometer and non-contact confocal microscope to measure the roughness of machined elastomer surfaces. The comparison of measurement results shows the advantages and limitations of both measurement methods.     

An optimization method of the machining parameters in high-speed machining of stainless steel using coated carbide tool for best surface finish

High-speed machining (HSM) has emerged as a key technology in rapid tooling and manufacturing applications. Compared with traditional machining, the cutting speed, feed rate has been great progress, and the cutting mechanism is not the same. HSM with coated carbide cutting tools used in high-speed, high temperature situations and cutting more efficient and provided a lower surface roughness. However, the demand for high quality focuses extensive attention to the analysis and prediction of surface roughness and cutting force as the level of surface roughness and the cutting force partially determine the quality of the cutting process. This paper presents an optimization method of the machining parameters in high-speed machining of stainless steel using coated carbide tool to achieve minimum cutting forces and better surface roughness. Taguchi optimization method is the most effective method to optimize the machining parameters, in which a response variable can be identified. The standard orthogonal array of L₉ (3⁴) was employed in this research work and the results were analyzed for the optimization process using signal to noise (S/N) ratio response analysis and Pareto analysis of variance (ANOVA) to identify the most significant parameters affecting the cutting forces and surface roughness. For such application, several machining parameters are considered to be significantly affecting cutting forces and surface roughness. These parameters include the lubrication modes, feed rate, cutting speed, and depth of cut. Finally, conformation tests were carried out to investigate the improvement of the optimization. The result showed a reduction of 25.5% in the cutting forces and 41.3% improvement on the surface roughness performance.     

Milling Force Model for Aviation Aluminum Alloy:Academic Insight and Perspective Analysis

Aluminum alloy is the main structural material of aircraft,launch vehicle,spaceship,and space station and is pro-cessed by milling.However,tool wear and vibration are the bottlenecks in the milling process of aviation aluminum alloy.The machining accuracy and surface quality of aluminum alloy milling depend on the cutting parameters,material mechanical properties,machine tools,and other parameters.In particular,milling force is the crucial factor to determine material removal and workpiece surface integrity.However,establishing the prediction model of milling force is important and difficult because milling force is the result of multiparameter coupling of process system.The research progress of cutting force model is reviewed from three modeling methods:empirical model,finite element simulation,and instantaneous milling force model.The problems of cutting force modeling are also determined.In view of these problems,the future work direction is proposed in the following four aspects:(1)high-speed milling is adopted for the thin-walled structure of large aviation with large cutting depth,which easily produces high residual stress.The residual stress should be analyzed under this particular condition.(2)Multiple factors(e.g.,eccentric swing milling parameters,lubrication conditions,tools,tool and workpiece deformation,and size effect)should be consid-ered comprehensively when modeling instantaneous milling forces,especially for micro milling and complex surface machining.(3)The database of milling force model,including the corresponding workpiece materials,working condi-tion,cutting tools(geometric figures and coatings),and other parameters,should be established.(4)The effect of chatter on the prediction accuracy of milling force cannot be ignored in thin-walled workpiece milling.(5)The cutting force of aviation aluminum alloy milling under the condition of minimum quantity lubrication(mql)and nanofluid mql should be predicted.     

电弧微铸锻增材制造AlMgSc合金纵扭复合超声振动干铣削加工特性研究

对电弧微铸锻增材制造AlMgSc合金进行纵扭超声复合干铣削加工特性试验研究,探讨超声铣削工艺参数对切削力、表面形貌、加工硬化及刀具磨损等AlMgSc合金干铣削成形特性的影响规律。结果表明: 与锻造和常规电弧增材成形铝合金相比,微铸锻增材制造AlMgSc合金由于具备更加致密的微观组织、更高的强度和硬度而在超声干铣削成形过程中会产生更大的铣削力,更容易发生加工硬化。与常规干铣削相比,采用纵扭复合超声干铣削可以获得更小的表面粗糙度,并有利于减轻刀具磨损。     

Deformation behaviour of sintered silicon–copper steel preforms of various aspect ratios during cold upsetting

This paper presents the optimization of the face milling process of 7075 aluminum alloy by using the gray relational analysis for both cooling techniques of conventional cooling and minimum quantity lubrication (MQL), considering the performance characteristics such as surface roughness and material removal rate. Experiments were performed under different cutting conditions, such as spindle speed, feed rate, cooling technique, and cutting tool material. The cutting fluid in MQL machining was supplied to the interface of work piece and cutting tool as pulverize. An orthogonal array was used for the experimental design. Optimum machining parameters were determined by the gray relational grade obtained from the gray relational analysis.     

颗粒增强铝基复合材料铣削加工实验研究

使用K10硬质合金铣刀,在不使用冷却液的条件下,对A12024/SiCp复合材料进行铣削加工实验,研究切削参数和颗粒尺寸对表面质量、切削力、刀具磨损的影响.研究表明,随着增强颗粒尺寸的增大,表面变粗糙、切削力增大和刀具磨损加重;在不同的切削条件下,法向力均大于切向力.随着切削用量的增大,铣削力呈增大趋势,其中,吃刀量对铣削力的影响最大,切削速度的影响最小;加工表面上存在凹坑、颗粒突起和基体材料涂敷等缺陷,表面粗糙度随着颗粒尺寸增大而增大,随着切削速度的提高而减小.     

Selection of optimum tool geometry and cutting conditions using a surface roughness prediction model for end milling

Influence of tool geometry on the quality of surface produced is well known and hence any attempt to assess the performance of end milling should include the tool geometry. In the present work, experimental studies have been conducted to see the effect of tool geometry (radial rake angle and nose radius) and cutting conditions (cutting speed and feed rate) on the machining performance during end milling of medium carbon steel. The first and second order mathematical models, in terms of machining parameters, were developed for surface roughness prediction using response surface methodology (RSM) on the basis of experimental results. The model selected for optimization has been validated with the Chi square test. The significance of these parameters on surface roughness has been established with analysis of variance. An attempt has also been made to optimize the surface roughness prediction model using genetic algorithms (GA). The GA program gives minimum values of surface roughness and their respective optimal conditions.     

Experimental investigations while hard machining of DIEVAR tool steel (50 HRC)

This paper describes hard machining which offers many potential benefits over traditional manufacturing techniques. In this work, investigations were carried out on end milling of hardened tool steel DIEVAR (hardness 50 HRC), a newly developed tool steel material used by tool- and die-making industries. The objective of the present investigation was to study the performance characteristics of machining parameters such as cutting speed, feed, depth of cut and width of cut with due consideration to multiple responses, i.e. volume of material removed, tool wear, tool life and surface finish. Performance evaluation of physical vapour deposition-coated carbide inserts, ball end mill cutter and polycrystalline cubic boron nitride inserts (PCBN) was done for rough and finish machining on the basis of flank wear, tool life, volume of material removed, surface roughness and chip formation. It has been observed from investigations that chipping, diffusion and adhesion were active tool wear mechanisms and saw-toothed chips were formed whilst machining DIEVAR hard steel. PCBN inserts give an excellent performance in terms of tool life and surface finish in comparison with carbide-coated inserts. End milling technique using PCBN inserts could be a viable alternative to grinding in comparison to ball end mill cutter in terms of surface finish and tool life.     

Milling force vibration analysis in high-speed-milling titanium alloy using variable pitch angle mill

Chatter may cause fast wear of tools and poor surface quality of the workpieces at high cutting speed and it will happen on different process parameters; how do we select the suitable cutting speed to suppress the chatter? In this paper, a signal analysis method for milling force and acceleration is adopted to identify chatter, which can obtain the results not only in frequency of chatter but also in the contribution for milling force at different frequencies. Through the milling experiment, the machining vibration behaviors of milling Ti–6Al–4V with variable pitch end mill were investigated. Milling force and acceleration signals obtained from experiment were analyzed and compared at stable and unstable milling processes. The experimental results show that when the chatter occurs, milling forces were found to increase dramatically by 61.9–66.8% compared with that of at stable cutting; machining surface quality became poor and machined surface roughness increases by 34.2–40.5% compared with that of at stable cutting.     

Surface Integrity of Ultrasonically-Assisted Milled Ti6Al4V Alloy Manufactured by Selective Laser Melting

The Ti6Al4V parts produced by the existing selective laser melting (SLM) are mainly confronted with poor surface finish and inevitable interior defects,which substantially deteriorates the mechanical properties and performances of the parts.In this regard,ultrasonically-assisted machining (UAM) technique is commonly introduced to improve the machining quality due to its merits in increasing tool life and reducing cutting force.However,most of the previous studies focus on the performance of UAM with ultrasonic vibrations applied in the tangential and feed directions,whereas few of them on the impact of ultrasonic vibration along the vertical direction.In this study,the effects of feed rate on surface integrity in ultrasonically-assisted vertical milling (UAVM) of the Ti6Al4V alloy manufactured by SLM were systemically investigated compared with the conventional machining (CM) method.The results revealed that the milling forces in UAVM showed a lower amplitude than that in CM due to the intermittent cutting style.The surface roughness values of the parts produced by UAVM were generally greater than that by CM owing to the extra sinusoidal vibration textures induced by the milling cutter.Moreover,the extra vertical ultrasonic vibration in UAVM was beneficial to suppressing machining chatter.As feed rate increased,surface microhardness and thickness of the plastic deformation zone in CM raised due to more intensive plastic deformation,while these two material properties in UAVM were reduced owing to the mitigated impact effect by the high-frequency vibration of the milling cutter.Therefore,the improved surface microhardness and reduced thickness of the subsurface deformation layer in UAVM were ascribed to the vertical high-frequency impact of the milling cutter in UAVM In general,the results of this study provided an in-depth understanding in UAVM of Ti6Al4V parts manufactured by SLM.     

Comparative evaluations of machining performance during turning of 17-4 PH stainless steel under cryogenic and wet machining conditions

Productivity in machining of 17-4 PH stainless steel is adversely affected by the premature failure of tool and poor surface finish as a consequence of high cutting temperatures. Conventional cutting fluids not only create environmental and health problems but also fail to overcome the high cutting temperatures during machining. Cryogenic cooling is an environmentally clean cooling technology for attractive management of machining zone temperatures. The present study investigates the effect of cryogenic liquid nitrogen (LN₂ at ?196°C) on cutting temperatures, cutting forces (main cutting force, feed force), surface roughness, tool flank wear and chip morphology in turning of 17-4 PH stainless steel with AlTiN PVD-coated tungsten-coated carbide inserts and results were compared to wet machining. In overall, cryogenic machining reduces the cutting temperature, cutting forces, surface roughness and tool flank wear to a maximum of 73.4, 17.62, 44.29 and 55.55%, respectively. Improved chip breakability was found in cryogenic machining.     

Investigation of the performance of carbide cutting tools with hard coatings in hard milling based on the response surface methodology

Machining of hard materials has become a great challenge for several decades. One of the problems in this machining process is early tool wear, and this affects the machinability of hard materials. In order to increase machinability, cutting tools are widely coated with nanostructured physical vapor deposition hard coatings. The main characteristics of such advanced hard coatings are high microhardness and toughness as well as good adhesion to the substrate. In this paper, the influence of hard coatings (nanolayer AlTiN/TiN, multilayer nanocomposite TiAlSiN/TiSiN/TiAlN, and commercially available TiN/TiAlN) and cutting parameters (cutting speed, feed rate, and depth of cut) on cutting forces and surface roughness were investigated during face milling of AISI O2 cold work tool steel (～61 HRC). The experiments were conducted based on 3¹³ factorial design by response surface methodology, and response surface equations of cutting forces and surface roughness were obtained. In addition, the cutting forces obtained with the coated and uncoated tools were compared. The results showed that the interaction of coating type and depth of cut affects surface roughness. The hard coating type has no significant effect on cutting forces, while the cutting force F _z is approximately two times higher in the case of uncoated tool.     

An experimental investigation on the process parameters influencing machining forces during milling of carbon and glass fiber laminates

Milling is the most feasible machining operation for producing slots and keyways with a well defined and high quality surface. Milling of composite materials is a complex task owing to its heterogeneity and the associated problems such as surface delamination, fiber pullout, burning, fuzzing and surface roughness. The machining process is dependent on the material characteristics and the cutting parameters. An attempt is made in this work to investigate the influencing cutting parameters affecting milling of composite laminates. Carbon and glass fibers were used to fabricate laminates for experimentations. The milling operation was performed with different feed rates, cutting velocity and speed. Numerically controlled vertical machining canter was used to mill slots on the laminates with different cutting speed and feed combinations. A milling tool dynamo meter was used to record the three orthogonal components of the machining force. From the experimental investigations, it was noticed that the machining force increases with increase in speed. For the same feed rate the machining force of GFRP laminates was observed to be very minimal, when compared to machining force of CFRP laminates. It is proposed to perform milling operation with lower feed rate at higher speeds for optimal milling operation.     

EFFECT OF PROCESS PARAMETERS AND TOOL SHAPE ON THE MACHINABILITY OF A PARTICULATE FILLED-POLYMER COMPOSITE MATERIAL FOR RAPID TOOLING

This paper presents the results of an experimental study on the effects of machining parameters (cutting speed, feed, depth of cut) and tool shape on chip formation, surface topography, resultant cutting force and surface roughness produced in flat and ball end milling of the Ren Shape-Express 2000™ aluminum particulate filled-polymer composite material. This material is shown to exhibit a brittle-to-ductile transition in chip formation with decreasing cutting speed. The transition is explained by the strain-rate sensitivity of the polymer matrix and is found to correlate well with a corresponding change in the surface roughness. The absence of clear feed marks on the milled surface explains why molds made from the composite material require less hand polishing than machined metal molds. The influence of cutting conditions and tool shape (flat end vs. ball-nose) on the cutting force, surface roughness, and workpiece breakout are discussed and relevant comparisons with conventional metal and polymer machining are made.