Kai Ming Yu

Variable Radius Conformal Cooling Channel for Rapid Tool

The cooling system of a plastic injection mould is important as it affects the quality and productivity of the polymeric components or assemblies. Contemporary cooling channel design is confined to simple configurations of straight-drilled coolant passageway around the mould insert. Undesirable defects resulted during injection moulding, such as warpage, are inevitable. The application of rapid tool (RT) based on solid freeform fabrication (SFF) technologies with conformal cooling channel (CCC) design has provided a profound opportunity in quality improvement of polymeric components. In this study, a novel design of variable radius conformal cooling channel (VRCCC) is proposed to achieve better uniform cooling performance. Thermal-FEA and melt flow analysis are used to validate the method.

Taguchi Methods to Optimize TiN Coating Surface Roughness

Cathodic Arc Physical Vapor deposition (CAPVD) uses a high current, low and negative voltage arc to vaporize a cathodic electrode (cathodic arc) and deposit the vaporized material on a substrate. The vaporized material is ionized in a vacuum chamber and the substrates are usually biased so as to accelerate the ions to the substrate surface. CAPVD provides a very dense film with excellent adhesion to the substrates. Therefore, this technique is mainly used to deposit on cutting tools such as end mills, drills, inserts, plastics and metal molds and high wear resistance tribology components. However, this coating technique will produce unwanted micro particles (droplets) [1] which usually are the target materials that cannot be reacted in coating process. These particles will affect the coating roughness and the surface morphology. To optimize this condition, Taguchi method is introduced to obtain the best experimental parameter settings. In this study, Atomic Force Microscope (AFM) is used to analyze the roughness of the coating for the following factors: bias voltage, arc current, nitrogen pressure and coating thickness.

Warm-Forming of Light-Weight Alloys under Multi-Stage Forming Process

This paper aims at presenting an experimental investigation to obtain the optimum formability of light-weight alloys under the multi-stage forming process. Titanium alloy sheets (Ti-6Al-4V) and aluminium alloy sheets (AA5052) are selected as forming specimens. The special fixture with heating device is applied in order to carry out the prestraining process. The swift forming test at warm-forming condition is performed for measuring the limit dome heights after the multi-stage formign process. The outcomes of this investigation are valuable for engineers to design and fabricate high-quality light-weight components efficiently.

Thermal forming of light-weight alloys under a multi-stage forming process

Abstract This article presents an experimental investigation aimed to obtain the optimum formability of light-weight alloys under the multi-stage forming process. Titanium alloy sheets (Ti-6Al-4V) and aluminium alloy sheets (AA5052) of thickness 1 mm with different widths (i.e. 20, 90, and 110 mm) are selected as forming specimens. In order to carry out the multi-stage forming process, a special fixture with a heating system for the pre-straining process is designed and manufactured. The limit dome heights of both titanium alloys and aluminium alloys are measured and recorded. The experimental results reveal that both of the light-weight alloys yielded enhanced ductility at higher working temperatures, because of a decrease in the yield strength. The formability of selected materials is found to be sensitive to the forming temperatures and multi-stage forming processes.

Balanced Octree for Tetrahedral Mesh Generation

Nowadays, with the advances of Finite Element Analysis (FEA) packages, some of the engineering and design problems such as stress or thermal deformation can be successfully solved. These are convenient for better incorporating the design constraints of various tasks such as injection molded parts, or rapid prototyping and tooling. Mesh generation is the major step of finite element method for numerical computation. Common types of mesh include triangulation or tetrahedralization. During the mesh generation process, we always find difficulty in the formation of a uniform, non-conformal mesh. The undesirable mesh will adversely influence the accuracy and meshing time of the model. This paper will, thus, propose an effective approach to extend to threedimensional (3D) mesh generation by octree balancing method so as to adjust the mesh pattern. In this paper, the implementation of octree balancing will be explained and illustrated with real life example. The proposed method includes three main steps. Problematic unbalanced octants will be detected and Steiner points will be added as appropriate before the tetrahedral mesh generation. The balanced octree will form good tetrahedral meshes for further analysis. Then the balanced and unbalanced meshes will be compared for efficiency and accuracy for mesh generation.

Property estimate for inkjet based direct digital manufacturing

Nowadays, additive manufacturing (AM) is an emerging manufacturing technology growing rapidly. Superior to the traditional manufacturing, AM can produce unique objects quickly and at a low cost. However, most of the AM technology can only product object with single or a few color and material. Inkjet based direct digital manufacturing (DDM) can fabricate objects with different colors and materials. However, characterization of objects materials fabricated by DDM still has great complexity. Therefore, we propose to estimate the property of the inkjet material fabricated by the DDM in a reasonable range by interpolating the materials with the arithmetic and harmonic limit. By comparing the material property of the digital material obtained from a literature with our proposed models, the material property of the digital material fits into the range of our calculated arithmetic sum and harmonic sum.

Optimizing TiN Coating Surface Roughness with RSM

This paper presents using Response Surface Method (RSM) to optimize average surface roughness (Ra) of titanium nitride (TiN) coating. The Cathodic Arc Physical Vapor Deposition (CAPVD) technique was used to produce the coating which is mainly used to deposit on cutting tools and molds. To optimize the Ra value, RSM was aimed to obtain the best parameter settings. Surface profilometer was used to analyze the coating roughness for the following factors: bias voltage (Vb), , nitrogen (N2) pressure (P). To conclude, when Vb = -115V and N2 pressure = 9.54 x 10 E-03, the Ra value could be optimized at 0.23μm. Introduction CAPVD is a technique mainly used to deposit on cutting tools, molds and high wear resistance tribology components[1-2]. Some previous work[3-4] investigated the influence of the bias voltage, arc current and N2 pressure to coating structure, hardness and surface morphology of coating. Researchers[5] optimized cathodic arc plasma deposition system with titanium aluminum nitride (TiAlN) coating. Vb, N2 pressure, and target composition were found to be the most influential variables to wear resistance of TiAlN coating in eight factors. Another research[4] studied the influences of changing Vb when coating aluminum titanium nitride. They found that carbide drills deposited with lower bias voltage showed better cutting performance in machining carbon steel. However, studies carried out to optimize the mean roughness values (Ra) on mold steel with titanium nitride (TiN) coating have not been discussed before. Therefore, this study uses RSM to optimize the Ra value of TiN coated forming and drawing mold materials with 2 critical factors: bias voltage (Vb) and nitrogen pressure (P). Experimental In this study, TiN coating was deposited by PLATIT PL50 cathodic arc deposition system. A prehardened mold steel ASSAB 88, usually used for metal forming and drawing process, dimension in φ13x5mm, was polished to Ra value around 0.2μm. The Ra values were measured by a Mitutoyo surface profilometer. By the screening experiments in previous research[6] (using Taguchi Methods), it was found that 2 factors have significant influence on coating roughness. One is bias voltage and another is nitrogen N2 pressure. RSM experiment was then used to find the best setting of the four corners in the optimal window. Results and Discussions The first order model of experiments had 4 runs, 2 replications and with 2 samples in each run. Coded variable is used to represent the natural variable, x1 for Vb and x2 for N. Table 1 shows the relationship between natural and coded variables and the result of TiN coating Ra measurements. Table 2 shows the Analysis of Variance (ANOVA) table of the first order model. Materials Science Forum Online: 2006-12-15 ISSN: 1662-9752, Vols. 532-533, pp 424-427 doi:10.4028/www.scientific.net/MSF.532-533.424

Evolution Trends of Material Usage and Processing in Spectacle Frame

Nowadays’ optical frames are the result of a collaboration between designers and engineers; it is a combination of high technology and art. Around 250 technical operations are performed in order to make a high-quality metal frame, and there are 120 to 180 operations to make a plastic frame. Although the Asian manufacturers of optical frames are prevailing in the world market, a relatively rudimentary trial-and-error method is being used. A more systematic and analytic approach is thus needed for them to grasp the evolution trends in the competitive market. This paper discusses how Gabriel Tarde’s diffusion S-curve and the TRIZ theory can be employed to analyze the evolution trends in optical frame design and manufacturing.