The Effect of Tool Path Strategy on Surface and Dimension in High Speed Milling

Many orthopedic implants like proximal humerus cases require lower surface roughness and almost immediate/short lead time surgery. Thus, rapid response from the manufacturer is very crucial. Tool path strategy of milling process has a direct influence on the surface roughness and lead time of medical implant. High-speed milling as promised process would improve the machined surface quality, but conventional or super-abrasive grinding still required which imposes some drawbacks such as additional costs and time. Currently, many CAD/CAM software offers some different tool path strategies to milling free form surfaces. Nevertheless, the users must identify how to choose the strategies according to cutting tool geometry, geometry complexity, and their effects on the machined surface. This study investigates the effect of different tool path strategies for milling a proximal humerus head during finishing operation on stainless steel 316L. Experiments have been performed using MAHO MH700 S vertical milling machine and four machining strategies, namely, spiral outward, spiral inward, and radial as well as zig-zag. In all cases, the obtained surfaces were analyzed in terms of roughness and dimension accuracy compared with those obtained by simulation. The findings provide evidence that surface roughness, dimensional accuracy, and machining time have been affected by the considered tool path strategy

Effect of modifier elements on machinability of Al-20Mg2Si metal matrix composite during dry turning

The principle aim of this study was to observe the effect of machining parameters as well as the separate additions of 0.4 wt% bismuth, 0.01 wt% strontium, and 0.8 wt% antimony on the machinability of Al-20%Mg2Si in situ metal matrix composite. Microstructure alteration, surface roughness, main cutting force, and chip morphology were taken into account as indices to examine the effect of modifiers and machinability during dry turning. It was found that the additives modify the Mg2SiP particles by changing the particle shape from coarse primary to polygonal shape and decrease the particle size and aspect ratio as well as increase the particle density. Results show that the modified work-pieces present adequate machinability with respect to cutting force and surface roughness. The smaller reinforcements enable lower surface roughness values to be obtained even if they are pulled out, fractured, or elongated. In addition, the modified work-pieces encourage lower surface roughness values in comparison with unmodified work-piece due to less built-up-edge formation. A scenario for surface roughness of Al-Mg2Si composite with respect to the size and aspect ratio of reinforcement particles is proposed in this study

Functionality Analysis of Thermoplastic Composite Material to Design Engine Components

Developing of innovative technologies and materials to meet the requirements of environmental legislation on vehicle emissions has paramount importance for researchers and industries. Therefore, improvement of engine efficiency and fuel saving of modern internal combustion engines (ICEs) is one of the key factors, together with the weight reduction. Thermoplastic composite materials might be one of the alternative materials to be employed to produce engine components to achieve these goals as their properties can be engineered to meet application requirements. Unidirectional carbon fiber reinforced PolyEtherImide (CF/PEI) thermoplastic composite is used to design engine connecting rod and wrist pin, applying commercial engine data and geometries. The current study is focused on some elements of the crank mechanism as the weight reduction of these elements affects not only the curb weight of the engine but the overall structure. As a matter of fact, by reducing the reciprocating mass, alternate forces will be reduced and hence the size of the structural elements. Also, other elements of the engine can be designed for lightweighting, but the crank mechanism elements maximize the effects, by reducing both loads and weight. Finite element analysis (FEM) has been conducted for proper stress analysis and accordingly examine the design and parts functionalities. FEM analysis is performed using Altair HyperMesh for mesh optimization to conduct stress analysis of standard engine components made of steel and to redesign the parts using thermoplastic material to sustain the loads and stresses. Then the design modification has been considered to reduce loads and weight without parts performance interruption under service

Process variable effect on the strength of autoclave-bonded film adhesive joints

This study investigates the effect of five independently-controlled process variables and variable combinations on the shear strength of autoclave-bonded film adhesive joints. Studied variables include the cure temperature, cure pressure and their respective ramp rates, as well as the duration of cure time. A full factorial design of experiment (DoE) at two levels for each variable is conducted with 3 replicas of each test. Test coupons are made of two layers of polycarbonate lexan that are autoclave-bonded using aliphatic polyether film adhesive (Huntsman PE399). Two set of test joints are used for generating test data on shear strength and failure mode. Bonded joints in the first set are tested prior to any environmental cycling, in order to generate baseline data on joint shear strength and failure mode. However, samples from the second set of autoclave-bonded joints were heat-cycled, in an environmental chamber at high relative humidity, prior to testing for shear strength. Test data on shear strength and failure mode is statistically analyzed using ANOVA

Multi-objective optimization of converting process of auxetic foam using three different statistical methods

This paper studies the optimization of converting process parameters of conventional foam into the auxetic. The control factors of converting process are heat temperature, pressure and time. The aim of this study is to achieve an optimum combination of these control factors for obtaining maximum stiffness and minimum negative Poisson’s ratio as the desired responses. A series of experiments were implemented based on the Taguchi orthogonal array design. In order to determine the optimum control factors level, three different multi-objective optimization methods i.e. grey relational analysis, fitness function and desirability function were employed. The optimum combinations achieved form all methods were verified through the confirmation tests. Although outcomes of all these methods, in the case of both Poisson's ratio and stiffness, were in a good agreement with the confirmation tests, however the result of grey relational analysis had the minimum mean error percentage. Also, all these methods reported the pressure, heat temperature and time as the first, second and third level of significance, respectively. This study allows manufacturer to select the optimization procedure appropriately and produce the auxetic foam with minimum waste material

Effect of barium on the structure and characteristics of Mg2Si reinforced particles Al–Mg2Si–Cu in situ composite

Addition of barium (Ba) in various concentrations is susceptible to cause changes on Mg2Si reinforced particles in Al–Mg2Si–Cu in situ composite. In this study, six samples of the composite with different concentrations of Ba (0.1–0.8 wt%) were prepared. The alteration of Mg2Si structure, phase reaction characteristics and cooling curves behaviour of the composite were investigated via optical microscope, scanning electron microscope (SEM), and computer aided cooling curve thermal analysis (CACCTA). The results depicted that 0.2 wt% exhibit the appropriate concentration of Ba added in order to modify and refine the Mg2Si particles. The skeleton and dendrite shape of Mg2Si particles have been transformed into fine polygonal shape accompanied with decreased in average size from 1178.5 µm of the unmodified particles to 289.1 µm. In fact, the refinement of Mg2Si particles is associated with the increased of nucleation temperature, TN of the respective phase together with the least undercooling, ΔU correspond to the easiness of the particles to be formed prior to its growth. Meanwhile, the decrement of TN respective to other concentrations of Ba indicates the opposite refinement effect of the particles as it became coarser. Besides, the refinement of Mg2Si has induced more nucleation of the particles resulting the increment of the density of particles and better distribution over the composite area. Therefore, the corresponding mechanical and tribological properties of the composite are believed to be improved accordingly