A Cost-Effective Approach to Creating Large Silicone Rubber Molds Using Advanced Rigid Polyurethane Foam.

In practical applications, polyurethane (PU) foam must be rigid to meet the demands of various industries and provide comfort and protection in everyday life. PU foam components are extensively used in structural foam, thermal insulation, decorative panels, packaging, imitation wood, and floral foam, as well as in models and prototypes. Conventional technology for producing PU foam parts often leads to defects such as deformation, short shots, entrapped air, warpage, flash, micro-bubbles, weld lines, and voids. Therefore, the development of rigid PU foam parts has become a crucial research focus in the industry. This study proposes an innovative manufacturing process for producing rigid PU foam parts using silicone rubber molds (SRMs). The deformation of the silicone rubber mold can be predicted based on its wall thickness, following a trend equation with a correlation coefficient of 0.9951. The volume of the PU foam part can also be predicted by the weight of the PU foaming agent, as indicated by a trend equation with a correlation coefficient of 0.9824. The optimal weight ratio of the foaming agent to water, yielding the highest surface hardness, was found to be 5:1. The surface hardness of the PU foam part can also be predicted based on the weight of the water used, according to a proposed prediction equation with a correlation coefficient of 0.7517. The average surface hardness of the fabricated PU foam part has a Shore O hardness value of approximately 75. Foam parts made with 1.5 g of water added to 15 g of a foaming agent have the fewest internal pores, resulting in the densest interior. PU foam parts exhibit excellent mechanical properties when 3 g of water is added to the PU foaming agent, as evidenced by their surface hardness and compressive strength. Using rigid PU foam parts as a backing material in the proposed method can reduce rapid tool production costs by about 62%. Finally, an innovative manufacturing process for creating large SRMs using rigid PU foam parts as backing material is demonstrated.

Enhancing the Cooling Efficiency of Aluminum-Filled Epoxy Resin Rapid Tool by Changing Inner Surface Roughness of Cooling Channels.

In low-pressure wax injection molding, cooling time refers to the period during which the molten plastic inside the mold solidifies and cools down to a temperature where it can be safely ejected without deformation. However, cooling efficiency for the mass production of injection-molded wax patterns is crucial. This work aims to investigate the impact of varying surface roughness on the inner walls of the cooling channel on the cooling efficiency of an aluminum-filled epoxy resin rapid tool. It was found that the cooling time for the injection-molded products can be determined by the surface roughness according to the proposed prediction equation. Employing fiber laser processing on high-speed steel rods allows for the creation of microstructures with different surface roughness levels. Results demonstrate a clear link between the surface roughness of cooling channel walls and cooling time for molded wax patterns. Employing an aluminum-filled epoxy resin rapid tool with a surface roughness of 4.9 µm for low-pressure wax injection molding can save time, with a cooling efficiency improvement of approximately 34%. Utilizing an aluminum-filled epoxy resin rapid tool with a surface roughness of 4.9 µm on the inner walls of the cooling channel can save the cooling time by up to approximately 60%. These findings underscore the significant role of cooling channel surface roughness in optimizing injection molding processes for enhanced efficiency.

Enhancing the Weld Quality of Polylactic Acid Biomedical Materials Using Rotary Friction Welding.

Polylactic acid (PLA) stands out as a biomaterial with immense potential, primarily owing to its innate biodegradability. Conventional methods for manufacturing PLA encompass injection molding or additive manufacturing (AM). Yet, the fabrication of sizable medical devices often necessitates fragmenting them into multiple components for printing, subsequently requiring reassembly to accommodate the constraints posed by the dimensions of the AM platform. Typically, laboratories resort to employing nuts and bolts for the assembly of printed components into expansive medical devices. Nonetheless, this conventional approach of jointing is susceptible to the inherent risk of bolts and nuts loosening or dislodging amid the reciprocating movements inherent to sizable medical apparatus. Hence, investigation into the joining techniques for integrating printed components into expansive medical devices has emerged as a critical focal point within the realm of research. The main objective is to enhance the joint strength of PLA polymer rods using rotary friction welding (RFW). The mean bending strength of welded components, fabricated under seven distinct rotational speeds, surpasses that of the underlying PLA substrate material. The average bending strength improvement rate of welding parts fabricated by RFW with three-stage transformation to 4000 rpm is about 41.94% compared with the average bending strength of PLA base material. The average surface hardness of the weld interface is about 1.25 to 3.80% higher than the average surface hardness of the PLA base material. The average surface hardness of the weld interface performed by RFW with variable rotational speed is higher than the average surface hardness of the weld interface performed at a fixed rotating friction speed. The temperature rise rate and maximum temperature recorded during RFW in the X-axis of the CNC turning machine at the outer edge of the welding part surpassed those observed in the internal temperature of the welding part. Remarkably, the proposed method in this study complies with the Sustainable Development Goals due to its high energy efficiency and low environmental pollution.

Development of a Silicone Rubber Mold with an Innovative Waterfall Cooling Channel.

A conformal cooling channel (CCC) follows the mold core or cavity profile to carry out uniform cooling in the cooling stage. However, the significant pressure drop along the cooling channels is a distinct disadvantage of the CCC. In this study, an innovative waterfall cooling channel (WCC) was proposed and implemented. The WCC cools the injected products via surface contact, replacing the conventional line contact to cool the injected products. The WCC was optimized using numerical simulation software. Silicone rubber molds with two kinds of cooling channels were designed and implemented. The cooling time of the molded part was evaluated using a low-pressure wax injection molding machine. The experimental results of the cooling time of the molded part were compared with the simulation results from numerical simulation software. The results showed that the optimal mesh element count was about 1,550,000 with a mesh size of 1 mm. The simulation software predicted the filling time of the water cup injection-molded product to be approximately 2.008 s. The cooling efficiency for a silicone rubber mold with a WCC is better than that of the silicone rubber mold with a CCC since the core and cavity cooling efficiency is close to 50%. The pressure drop of the WCC is smaller than that of the CCC, which reduces the pressure drop by about 56%. Taking a water cup with a mouth diameter of 70 mm, a height of 60 mm, and a thickness of 2 mm as an example, the experimental results confirmed that the use of the WCC can save the cooling time of the product by about 265 s compared with the CCC. This shows how a WCC can increase cooling efficiency by approximately 17.47%.

Rotary Friction Welding of Dissimilar Polymer Rods Containing Metal Powder.

Three-dimensional printing is widely used for manufacturing a variety of functional components. However, the 3D printing machine substantially limits the size of the functional components. Rotary friction welding (RFW) is a possible solution to this problem. In addition, there is a notable scarcity of research directed toward the domain knowledge of RFW involving dissimilar polymer rods containing metal powder. In this study, two welding specimens fabricated by polylactic acid (PLA)-containing copper powder and PLA-containing aluminum powder were joined using a turning machine. After RFW, a bending test and a Shore A surface hardness test were performed to investigate the weld quality. It was found that the bending strength of the welded parts fabricated by RFW of PLA and PLA-containing Al powder rods can be enhanced by about 57.5% when the welded part is placed at 45 °C. Surface hardness test results showed that the surface hardness of the weld interface is better than that of the 3D printed parts, and the average surface hardness of the weld interface from RFW of PLA and PLA is the highest. The surface hardness of the weld joint is about 3% higher than that of the base material. The surface hardness of the heat-affected zone is about 3% lower than that of the base material. The average peak temperature of the welded joint is the highest in the RFW of PLA-containing Al powder and PLA-containing Al powder rods. The average peak temperature of the weld joint can be as high as 160 °C. The average peak temperature of the welded joint is the highest in the RFW of PLA-containing Cu powder and PLA-containing Cu powder rods. The average peak temperature of the welded joint can be as high as 144 °C. A technical database was built for the selection of ambient temperatures used for the RFW of dissimilar polymer rods containing metal powder and three base materials.

Rotary Friction Welding of Polyetheretherketone Biopolymer Rods Using Variable Rotational Speed.

Polyetheretherketone (PEEK) is a promising biomaterial due to its excellent mechanical properties. Most PPEK manufacturing methods include additive manufacturing, injection molding, grinding, pulse laser drilling, or incremental sheet forming. Rotary friction welding (RFW) is a promising bonding technique in many industries. However, very few studies have focused on the RFW of PEEK. Conventionally, the number of revolutions is fixed during the welding process. Remarkably, the rotary friction welding of PEEK polymer rods using an innovative variable rotational speed is investigated in this study. The average bending strength of the welded part using a three-stage transformation rotational speed was enhanced by about 140% compared with a rotational speed of 1000 rpm. The advantage of computer numerical controlled RFW of PEEK using variable rotational speed is a reduced cycle time of RFW. A reduction in cycle time of about 6% can be obtained using the proposed RFW with a three-stage transformation rotational speed. The innovative approach provides low environmental pollution and high energy efficiency and complies with sustainable development goals.

Enhancing Surface Temperature Uniformity in a Liquid Silicone Rubber Injection Mold with Conformal Heating Channels.

To enhance the productivity and quality of optical-grade liquid silicone rubber (LSR) and an optical convex lens simultaneously, uniform vulcanization of the molding material is required. However, little has been reported on the uniform vulcanization of LSR in the heated cavity. This paper presents a conformal heating channel to enhance the temperature uniformity of the mold surface in the LSR injection molding. The curing rate of an optical convex lens was numerically investigated using Moldex3D molding simulation software. Two different sets of soft tooling inserts, injection mold inserts with conventional and conformal heating channels, were fabricated to validate the simulation results. The mold surface temperature uniformity was investigated by both numerical simulation and experiment. In particular, both a thermal camera and thermocouples were employed to measure the mold surface temperature after LSR injecting molding. It was found that the uniformity of the mold surface for LSR injection mold with the conformal heating channel was better. The average temperature of the mold surface could be predicted by the heating oil temperature according to the proposed prediction equation. The experimental results showed that the trend of the average temperature of five sensor modes was consistent with the simulation results. The error rate of the simulation results was about 8.31% based on the experimental result for the LSR injection mold with the conformal heating channel.

Development of a Rapid Tool for Metal Injection Molding Using Aluminum-Filled Epoxy Resins.

Metal injection molding (MIM) is a near net-shape manufacturing process combining conventional plastic injection molding and powder metallurgy. Two kinds of injections molds for MIM were developed using conventional mold steel and aluminum (Al)-filled epoxy resins in this study. The characteristics of the mold made by rapid tooling technology (RTT) were evaluated and compared with that of the fabricated conventional machining method through the MIM process. It was found that the service life of the injection mold fabricated by Al-filled epoxy resin is about 1300 molding cycles with the average surface roughness of 158 nm. The mold service life of the injection mold fabricated by Al-filled epoxy resin is about 1.3% that of the conventional mold steel. The reduction in manufacturing cost of an injection mold made by Al-filled epoxy resin is about 30.4% compared with that of the fabricated conventional mold steel. The saving in manufacturing time of an injection mold made by RTT is about 30.3% compared with that of the fabricated conventional machining method.

Effects of Ambient Temperature on the Mechanical Properties of Frictionally Welded Components of Polycarbonate and Acrylonitrile Butadiene Styrene Dissimilar Polymer Rods.

Rotary friction welding (RFW) has no electric arc and the energy consumption during welding can be reduced as compared with conventional arc welding since it is a solid-phase welding process. The RFW is a sustainable manufacturing process because it provides low environmental pollution and energy consumption. However, few works focus on the reliability of dissimilar polymer rods fabricated via RFW. The reliability of the frictionally welded components is also related to the ambient temperatures. This work aims to investigate the effects of ambient temperature on the mechanical properties of frictionally welded components of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS) dissimilar polymer rods. It was found that the heat-affected zone width increases with increasing rotational speeds due to peak welding temperature. The Shore A surface hardness of ABS/PC weld joint does not change with the increased rotational speeds. The Shore A surface hardness in the weld joint of RFW of the ABS/PC is about Shore A 70. The bending strength was increased by about 53% when the welded parts were placed at 60-70 °C compared with bending strength at room temperature. The remarkable finding is that the bending fracture position of the weldment occurs on the ABS side. It should be pointed out that the bending strength can be determined by the placed ambient temperature according to the proposed prediction equation. The impact energy was decreased by about 33% when the welded parts were placed at 65-70 °C compared with the impact energy at room temperature. The impact energy (y) can be determined by the placed ambient temperature according to the proposed prediction equation. The peak temperature in the weld interface can be predicted by the rotational speed based on the proposed equation.

Fatigue Behavior of Rotary Friction Welding of Acrylonitrile Butadiene Styrene and Polycarbonate Dissimilar Materials.

Understanding the fatigue behaviors of weld joints is significant in engineering practice. Rotary friction welding (RFW) can join the additively manufactured polymer components. Until now, no research has focused on the fatigue behavior of polymer components jointed via RFW. This study investigates the fatigue life of ABS/PC dissimilar components fabricated via RFW and proposes the fatigue mechanism based on the failure structure. This work uses five different cyclic loads and rotational speeds to investigate the fatigue life. The fatigue life of the RFW of ABS/PC dissimilar rods is better compared with the pure ABS and pure PC specimens due to weld and integrity microstructural changes resulting from the combination of ABS and PC materials. The number of cycles until the rupture of RFW of ABS/PC dissimilar components (y) can be determined by the cyclic load (x) according to the prediction equation of y = -838.25x2 - 2035.8x + 67,262. The fatigue life of the RFW of ABS/PC dissimilar components increase with the increased rotational speed. The number of cycles until rupture (y) can be determined by the different rotational speeds (x) according to the prediction equation of y = 315.21x2 + 2710.4x + 32,124.

Development of an Injection Mold with High Energy Efficiency of Vulcanization for Liquid Silicone Rubber Injection Molding of the Fisheye Optical Lens.

Liquid silicone rubber (LSR) techniques are experiencing exponential growth, particularly in the field of high technology due to the low-temperature flexibility, superior heat stability, chemical resistance, and aging resistance of LSR components. Enhancing the curing rate of LSR parts in liquid silicone rubber injection molding is an important research topic. In this study, an injection mold with high energy efficiency of vulcanization for the liquid silicone rubber injection molding of a fisheye lens was developed and implemented. The LSR injection mold has a conformal heating channel (CHC) and conformal cooling channel (CCC) simultaneously. The function of CHC is to enhance the curing rate of a fisheye lens in the LSR injection molding to meet the requirements of sustainable manufacturing. The curing rates of a fisheye lens were numerically examined using the Moldex3D molding simulation software. It was found that the curing rate of the fisheye optical lens cured by injection mold with CHC was better than that of the injection mold with a conventional heating channel. The curing efficiency could be increased by about 19.12% when the heating oil temperature of 180 °C was used to cure the fisheye optical lens. The simulation results showed that the equation y = -0.0026x3 + 1.3483x2 - 232.11x + 13,770 was the most suitable equation for predicting the curing time (y) through the heating oil temperature (x). It was found that the trend of the experimental results was consistent with the simulation results. In addition, the equation y = -0.0656x2 + 1.5827x - 0.894 with the correlation coefficient of 0.9974 was the most suitable equation for predicting the volumetric shrinkage of the fisheye optical lens (y) through the heating oil temperature (x). The volume shrinkage of the fisheye optical lens cured by injection mold with CHC was very similar to that of the injection mold with a conventional heating channel. The maximum volume shrinkage of the fisheye optical lens cured at 180 °C was about 8.5%.

Mechanical Performance and Microstructural Evolution of Rotary Friction Welding of Acrylonitrile Butadiene Styrene and Polycarbonate Rods.

Rotary friction welding (RFW) is a green manufacturing technology with environmental pollution in the field of joining methods. In practice, the welding quality of the friction-welded parts was affected by the peak temperature in the weld joint during the RFW of dissimilar plastic rods. In industry, polycarbonate (PC) and acrylonitrile butadiene styrene (ABS) are two commonly used plastics in consumer products. In this study, the COMSOL multiphysics software was employed to estimate the peak temperature in the weld joint during the RFW of PC and ABS rods. After RFW, the mechanical performance and microstructural evolution of friction-welded parts were investigated experimentally. The average Shore A surface hardness, flexural strength, and impact energy are directly proportional to the rotation speed of the RFW. The quality of RFW is excellent, since the welding strength in the weld joint is better than that of the ABS base materials. The fracture occurs in the ABS rods since their brittleness is higher than that of the PC rods. The average percentage error of predicting the peak temperature using COMSOL software using a mesh element count of 875,688 for five different rotation speeds is about 16.6%. The differential scanning calorimetry curve for the friction-welded parts welded at a rotation speed of 1350 rpm shows an endothermic peak between 400 to 440 °C and an exothermic peak between 600 to 700 °C, showing that the friction-welded parts have better mechanical properties.

Experimentation and Numerical Modeling of Peak Temperature in the Weld Joint during Rotary Friction Welding of Dissimilar Plastic Rods.

Rotary friction welding (RFW) could result in lower welding temperature, energy consumption, or environmental effects as compared with fusion welding processes. RFW is a green manufacturing technology with little environmental pollution in the field of joining methods. Thus, RFW is widely employed to manufacture green products. In general, the welding quality of welded parts, such as tensile strength, bending strength, and surface hardness is affected by the peak temperature in the weld joint during the RFW of dissimilar plastic rods. However, hitherto little is known about the domain knowledge of RFW of acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) polymer rods. To prevent random efforts and energy consumption, a green method to predict the peak temperature in the weld joint of dissimilar RFW of ABS and PC rods was proposed. The main objective of this work is to investigate the peak temperature in the weld joint during the RFW using COMSOL multiphysics software for establishing an empirical technical database of RFW of dissimilar polymer rods under different rotational speeds. The main findings include that the peak temperature affecting the mechanical properties of RFW of PC and ABS can be determined by the simulation model proposed in this work. The average error of predicting the peak temperature using COMSOL software for five different rotational speeds is about 15 °C. The mesh element count of 875,688 is the optimal number of meshes for predicting peak temperature in the weld joint. The bending strength of the welded part (y) using peak welding temperature (x) can be predicted by the equation of y = -0.019 x2 + 5.081x - 200.75 with a correlation coefficient of 0.8857. The average shore A surface hardness, impact energy, and bending strength of the welded parts were found to be increased with increasing the rotational speed of RFW.

Characterization of the Polyetheretherketone Weldment Fabricated via Rotary Friction Welding.

Polyether ether ketone (PEEK) is frequently employed in biomedical engineering due to its biocompatibility. Traditionally, PEEK manufacturing methods involve injection molding, compression molding, additive manufacturing, or incremental sheet forming. Few studies have focused on rotational friction welding (RFW) with PEEK plastics. Based on years of RFW practical experience, the mechanical properties of the weldment are related to the burn-off length. However, few studies have focused on this issue. Therefore, the main objective of this study is to assess the effects of burn-off length on the mechanical properties of the welded parts using PEEK polymer rods. The welding pressure can be determined by the rotational speed according to the proposed prediction equation. The burn-off length of 1.6 mm seems to be an optimal burn-off length for RFW. For the rotational speed of 1000 rpm, the average bending strength of the welded parts was increased from 108 MPa to 160 Mpa, when the burn-off length was increased from 1 mm to 1.6 mm and the cycle time of RFW was reduced from 80 s to 76 s. A saving in the cycle time of RFW of about 5% can be obtained. The bending strength of the welded part using laser welding is lower than that using RFW, because only the peripheral material of the PEEK cylinder was melted by the laser.

Effects of Rotational Speed on Joint Characteristics of Green Joining Technique of Dissimilar Polymeric Rods Fabricated by Additive Manufacturing Technology.

Friction welding (FW) FW of dissimilar polymer rods is capable of manufacturing green products swiftly and economically. In this study, a green manufacturing technique of joining dissimilar polymer rods was proposed, and the effects of rotational speed on the joint characteristics of friction-welded dissimilar polymer rods fabricated by the fused deposition modeling process were investigated experimentally. The shore surface hardness test, impact test, three-point bending test, and differential scanning calorimetry analysis were carried out on the weld joints. The impact energy for FW of polylactic acid (PLA) and PLA, PLA and acrylonitrile butadiene styrene (ABS), PLA and PLA filled with glass fiber (GF), PLA and PLA filled with carbon fiber (CF), PLA and polycarbonate (PC), and PLA and polyamide (PA) rods can be increased by approximately 1.5, 1.5, 1.3, 1.3, 2.1, and 1.5 times by increasing the rotational speed from 330 rpm to 1350 rpm. The bending strength for FW of PLA and PLA, PLA and ABS, PLA and PLA filled with GF, PLA and PLA filled with CF, PLA and PC, and PLA and PA rods can be increased by approximately 1.3, 1.7, 1.3, 1.2, 1.2, and 1.2 times by increasing the rotational speed from 330 rpm to 1350 rpm. However, the surface hardness of the weld bead is not proportional to the rotational speed. The average surface hardness of the weld bead was increased by approximately 5% compared to the surface hardness of the welding base materials.

Development of an Epoxy-Based Rapid Tool with Low Vulcanization Energy Consumption Channels for Liquid Silicone Rubber Injection Molding.

Liquid silicone rubber (LSR) parts have some distinct characteristics such as superior heat stability, low-temperature flexibility, aging resistance, and chemical resistance. From an industrial standpoint, the uniform vulcanization temperature of LSR is an important research point. However, the uniformity of the vulcanization temperature of LSR has been limited since the layout of the cartridge heater incorporated in the conventional steel mold does not follow the profile of the mold cavity. Metal additive manufacturing can be used to make LSR injection molds with conformal heating channels and conformal cooling channels simultaneously. However, this method is not suitable for a mold required to develop a new LSR product. In this study, a cost-effective approach was proposed to manufacture an LSR injection mold for the pilot run of a new optical lens. A rapid tool with low vulcanization energy consumption channels was proposed, which was incorporated with both a conformal heating channel (CHC) and conformal cooling channel (CCC) simultaneously. The function of the CHC was to vulcanize the LSR in the cavity uniformly, resulting in a shorter cycle time. The function of the CCC was to keep the LSR in a liquid state for reducing runner waste. It was found that the equation of y = -0.006x3 + 1.2114x2 - 83.221x + 1998.2 with the correlation coefficient of 0.9883 seemed to be an optimum trend equation for predicting the solidification time of a convex lens (y) using the vulcanizing hot water temperature (x). Additionally, the equation of y = -0.002x3 + 0.1329x2 - 1.0857x + 25.4 with the correlation coefficient of 0.9997 seemed to be an optimum prediction equation for the solidification time of a convex lens (y) using the LSR weight (x) since it had the highest correlation coefficient. The solidification time of a convex lens could be reduced by about 28% when a vulcanizing hot water temperature of 70 °C was used in the LSR injection mold with CHC.

Development of a Three-Dimensional Optical Verification Technology without Environmental Pollution for Metal Components with Different Surface Properties.

Nowadays, the optical measuring approach is widely used in the precision machining industry due to high measurement efficiency. In the industry, measuring devices play a crucial role in the field of quality assurance. In practical engineering, the green measurement approach indeed plays an important role in the industry currently. In this study, a state-of-the-art green technique for three-dimensional (3D) optical measurements without environmental pollution is demonstrated, which is an environmentally friendly optical measurement method. This method can perform precise optical measurement without matte coatings. This work dealt with the possibility of measuring four metal components that were not sprayed with anything. The differences in the optical measurement results between with and without matte coatings were investigated and analyzed. It was found that the research result has practical value in the precision machining industry because average size errors of the four measurement objects with different surface properties can be controlled at about 3 µm, 0.1 µm, 0.5 µm, and 9 µm. A technical database with industrial value was established for optical measurements of metal components with different surface properties without matte coatings, which can serve as an alternative to the conventional 3D optical measurement.

An Environmentally-Friendly Three-Dimensional Computer-Aided Verification Technique for Plastic Parts.

Plastic components play a significant role in conserving and saving energy. Plastic products provide some advantages over metal, including reducing part weight, manufacturing costs, and waste, and increasing corrosion resistance. Environmental sustainability is one of the sustainable development goals (SDGs). Currently, the non-contact computer-aided verification method is frequently employed in the plastic industry due to its high measurement efficiency compared with the conventional contact measuring method. In this study, we proposed an innovative, green three-dimensional (3D) optical inspection technology, which can perform precise 3D optical inspection without spraying anything on the component surface. We carried out the feasibility experiments using two plastic parts with complex geometric shapes under eight different proposed measurement strategies that can be adjusted according to the software interface. We studied and analyzed the differences in 3D optical inspection for building an empirical technical database. Our aim in this study is to propose a technical database for 3D optical measurements of an object without spraying anything to the component's surface. We found that the research results fulfilled the requirements of the SDGs. Our research results have industrial applicability and practical value because the dimensional average error of the two plastic parts has been controlled at approximately 3 µm and 4.7 µm.

Characterization of Epoxy-Based Rapid Mold with Profiled Conformal Cooling Channel.

Based on the experience of the foundry industry, reducing the demolding time is the key for mass production of wax patterns with sophisticated geometries. Integration of numerical simulation and rapid tooling technology for decreasing the time to market is essential in advanced manufacturing technology. However, characterization of epoxy-based rapid molds with a profiled conformal cooling channel (PCCC) using computer-aided engineering simulation of the epoxy-based rapid mold with PCCC was not found in the literature. In this study, epoxy-based rapid molds with PCCC were characterized numerically and experimentally. The cooling performance of wax injection molds with two different kinds of cross-sections of the cooling channel was investigated. Four pairs of injection molds with PCCC were implemented using four different kinds of material formulations. It was found that the cooling performance of the PCCC was better than a circular conformal cooling channel (CCCC) since the PCCC maintained a more uniform and steady cooling performance of injection-molded product than CCCC. Epoxy resin added with 41 vol.% Cu powder seems to be a cost-effective empirical material formulation in terms of cooling time and material costs. This empirical material formulation provided an injection mold with low material cost and good cooling performance simultaneously compared to an injection mold fabricated with commercial material. The cooling performance could reach 88% of that of the injection mold fabricated with commercial material. The material cost of making the injection mold was only about 60% of that of the injection mold fabricated with commercial material. The coolant flow rate had no significant effect on the cooling time, whereas the cooling time of the wax pattern was affected by coolant temperature significantly.

Weld Strength of Friction Welding of Dissimilar Polymer Rods Fabricated by Fused Deposition Modeling.

Friction welding (FRW) is a promising method for joining cylindrical components of dissimilar and similar polymers or metals. In particular, FRW is capable of generating defect-free welds. Fused deposition modeling (FDM) has been widely employed in the automotive industry, ranging from lightweight tools, testing models, and functional parts. Conventionally, dissimilar parts fabricated by FDM are joined by glue. However, distinct disadvantages of this approach include both low joining strength and low joining efficiency. Hitherto, little has been reported on the characterizations of weld strength of FRW of dissimilar parts fabricated by FDM. In addition, FRW of dissimilar polymeric materials is a difficult task because different polymers have different physical, rheological, and mechanical properties. In this study, the effects of welding revolution on the weld strength of friction welding dissimilar parts fabricated by FDM are investigated experimentally. It was found that the average flexural strength of dissimilar polymer rods fabricated by FRW is about 1.52 times that of dissimilar polymer rods fabricated by gluing. The highest flexure strength can be obtained by FRW using polylactic acid (PLA) and PC (polycarbonate) rods. The average impact strength of dissimilar polymer rods fabricated by FRW is about 1.04 times that of dissimilar polymer rods joined by gluing. The highest impact strength can be obtained by FRW using PLA to PLA rods.