Aluminum Mold Research Articles

Education in plastics manufacturing: Aluminum mold making and injection molding

Plastics are ubiquitous in the modern world with both positive and negative consequences. Students will benefit from understanding how plastics are manufactured. They will be more aware of the material and have a better appreciation for the need to recycle. Injection molding is one of the primary plastics manufacturing methods and hobby scale injection molding machines can be used to educate students about plastics and polymers. Furthermore, it is possible to create custom injection molds from aluminum using similar hobby scale tools. In this article, experiences introducing injection molding in the classroom and experiences with mold making as a senior design project are presented. Suggestions and procedures for using the injection molding machine and for creating custom aluminum molds are covered.

The design of the electromagnetic aluminum mold of periodic action

This publication discusses a set of issues on computer modeling of electromagnetic and thermal processes in an induction crystallizer of an aluminum melt, in which forces are created between the melt and the inductor coil, compressing the column of liquid material and preventing direct contact of the melt with the crucible walls. In known induction systems using electromagnetic pressure on molten metal, for crystallization, the parameters of the inductor are selected so that, with sufficient force, the temperature does not rise due to internal sources of heat release with sufficient water cooling of the surface. In the proposed work, heat removal mainly occurs through contact with a water-cooled support surface. The aim of the work is to determine the process parameters at which the required electromagnetic force is formed on the melt wall, taking into account the change in the current density at the interface between the solid and liquid phases of aluminum. When determining the parameters of induction crystallizers, the temperature dependences of the thermophysical properties were used. Variants of the inductor realization are investigated, which makes it possible to cover the entire volume of the melt, inside which significant changes in the electrical conductivity of aluminum and the power of internal heat sources are observed. Obtaining a cylindrical shape of the ingot, in contrast to the known electromagnetic crystallizers, is achieved by determining the design of the inductor, which provides a decrease in the repulsive electromagnetic force acting on the side surface of the melt in height. The results of the study showed the possibility of using the crystallizer at various ratios of the height and diameter of the melt column, and the intensity of cooling. The efficiency of the process for aluminum increases with an increase in the radius of the melt column, which also leads to a decrease in shape distortion in the region of the upper end.

Renewable Superhydrophobic Surfaces Prepared by Nanoimprinting Using Anodic Porous Alumina Molds.

Renewable superhydrophobic surfaces based on laminated polymer films with nanopillar array structures were prepared. Polymer nanopillar arrays exhibiting superhydrophobic properties were prepared by nanoimprinting using anodic porous alumina as a mold. The hydrophobic properties of the obtained polymer nanopillar arrays could be controlled and optimized by changing the geometrical structures of anodic porous alumina molds used for nanoimprinting. The polymer films were laminated using a photocurable monomer. The ordered polymer nanopillar array structures could be maintained even after delamination of the films. Renewed polymer nanopillar arrays exposed by peeling off the upper films exhibited a water contact angle higher than 150°. Using this process, superhydrophobic surfaces could be obtained repeatedly by delamination of a film even when superhydrophobicity deteriorated with the collapse of surface patterns. The obtained renewable superhydrophobic surfaces can be used for various applications requiring high durability.

Design of Precision Hot Embossing Machine for Micropatterning on PMMA

Abstract A microfluidic chip requires microchannels to be created on a substrate. This paper focuses on the design and development of a precision hot embossing machine for replication of microstructures on a polymethyl methacrylate (PMMA) substrate. Kinematic coupling using three spherical balls in radial v-grooves is used to achieve precise positioning of the mold insert with the base. Flexure-based parallel guidance mechanism is used for one degree-of-freedom (DOF) motion required for the embossing process. The mechanism allows the motion of the mold normal to the substrate surface. Flexure-based kinematic coupling with the thermal center is designed to mitigate thermal stress build-up during heating and cooling of the mold insert. An Arduino-based microcontroller is developed to control the temperature profile during the process. A prototype is fabricated and experiments are performed with an aluminum mold insert on a PMMA substrate. The result shows the feasibility of the concept and the setup can be used to develop a cost-effective precision hot embossing machine for creating micropatterns for microfluidic applications.

Improvement of polyurethane foam growth behavior of within an aluminum mold with a comparison between a specialized software and applied tests

The research carries out the simulation of the growth of the polyurethane foam inside a mold, in order to optimize the resources. The aim finds the accurate option within a production process both in the incorporation of a new product as in improving an existing one. Using the Moldex3D program, the project obtains a mathematical model to calculate parameters such as the viscosity of the material, pressure, volume, temperature, curing, foaming, heat capacity, thermal conductivity and mechanical properties of the material. The density obtained for the material analyzed experimentally is 59.09 kg·m−3 with a uniform watering at the base with a 10 degrees mold inclination with 1740 g of material and air outlets that help to obtain better conditions of mold, seeking to reduce the time used by 25% and reduce manufacturing costs.

Hybrid cooling based battery thermal management using composite phase change materials and forced convection

This paper investigates the thermal management performance of a novel system using phase change material (PCM) composite for Lithium-ion (Li-ion) battery in cell scale. An experimental platform was developed to study thermal phenomena in Li-ion cell. The system was designed on the basis of heat flux measurements. The cells are embedded in a PCM composite material. The assembly is lodged in an aluminum mold manufactured by 3D printing. The impact of the addition of metal foam and forced convection was evaluated. The results showed that the proposed system allows to keep the temperature of Li-ion cell around the optimal operating temperature, 25°C. It's also found that the addition of an aluminum foam allows a more efficient thermal management of the cell.

Cutting to the Point: Directly Machined Metal Molds for Directional Gecko-Inspired Adhesives

Abstract Fabrication techniques for gecko-inspired adhesives generally target mold durability, adhesive performance, and process efficiency and simplicity. With these goals in mind, we present a micromachining process for creating reusable aluminum molds used to fabricate directional dry adhesives. The molds require deep, narrow and overhanging grooves to create sharp and angled adhesive features. This geometry precludes most traditional machining and lithographic material removal processes. The presented process is a hybrid of indenting and orthogonal machining, using a diamond-coated microtome blade as the tool. An finite element analysis reveals the local extent of work hardening as each groove is created, and helps to define a trajectory that reduces the effects of tool deflection and chip build up. The results of a series of experiments agree with predictions from the analysis and reveal a range of blade approach angles and a lower bound on groove spacing to achieve the desired geometry. This range is narrower than for molds machined from wax in previous work. Nonetheless, adhesive samples cast from the new metal molds achieve comparable performance to those previously cast from wax.

Effects of wall compliance and light-curing protocol on wall deflection of simulated cavities in bulk-fill composite restoration

Background/purposeCuspal deflections in composite restoration have been investigated with considering wall compliance of human tooth cavity and light-curing protocol. The purpose of this study was to investigate effects of mold wall compliance and radiant emittance of LED light on the wall deflection of simulated aluminum mold cavities restored with a bulk-fill composite.Materials and methodsSixty aluminum molds simulating a class II mesio-occluso-distal (MOD) cavity (6 W × 8 L × 4 D mm; W, width; L, length; D, Depth) were prepared and allocated to three groups with varying mold wall thicknesses of 1, 2, and 3 mm. The molds were bulk-filled with a bulk-fill composite and photo-cured. Four light-curing protocols were used: three duty ratios/exposure times: 100%/20 s, 50%/40 s, or an increasing mode (0 → 100%)/40 s with a pulse width modulated (PWM) LED curing light and one 20 s exposure time with a commercial LED light.ResultsMean mold wall deflection at 2000 s decreased with increasing mold wall thickness (1, 2, and 3 mm) (p < 0.05). Wall deflections with 1- and 2-mm-thick molds exhibited no statistically significant differences among light-curing protocols (p > 0.05). However, in the 3-mm-thick mold, wall deflections with low radiant emittance were significantly lower than those with high radiant emittance (p < 0.05).ConclusionIn composite restoration of class II MOD cavities, lowering the radiant emittance of LED light can reduce the mold wall deflection only in low compliance cavities.

Braiding Thermoplastic and Glass Fibers in Composite Dental Post Improves Their Mechanical Compatibility, In Vitro Experiment.

Mechanical compatibility with the human dentin is a considerable issue when fabricating dental fiber posts. To this purpose, this study introduces a new method of fabricating compatible dental posts using braiding techniques of thermoplastic fibers (matrix) with glass fibers (reinforcement). Fifty fiber-reinforced composite (FRC) posts of thermoplastic yarns polypropylene (PP) braided with continuous filaments glass fibers (GFs) for reinforcement, varying in fiber volume fraction (FVF), and core types are fabricated and tested. Posts are performed using a braiding machine, and braids are placed in an aluminum mold. The filled mold is playced inside an oven at the melting temperature of the polypropylene to produce the final post’s shape. An ultrasonic test is conducted to measure the shear modulus and Young’s modulus of FRC post specimens by measuring the velocities of both the P-wave and S-wave. In order to ensure the accuracy of the measurements, each sample is measured three times, and then the means and standard deviations of each sample are calculated before analyzing the test results using the means of two steps, namely, clustering and comparing the P and R² values of each cluster, which revealed that FVF, fiber mass, and core type of the specimen had a significant effect on the resulted Young’s and shear modulus. The results indicate that the proposed method can fabricate competitive dental posts with regard to different fabricating variables. The samples show Young’s modulus ranges of from 10.08 GPa to 31.83 GPa. The following tested hypothesis is supported: the braiding technique of thermoplastic fibers with glass fibers will improve the mechanical compatibility of the resulting posts (ex vivo).

Engineering Graphene‐Ceramic 3D Composite Foams by Freeze Drying

A 3D graphene foam produced by the chemical vapor deposition (CVD) technique is recognized as an effective nanofiller material, as it does not agglomerate in the matrix. Though CVD facilitates pristine graphene foam production, the method poses limitations in developing large‐scale 3D graphene composite foams as advanced engineering materials. Herein, a freeze‐drying (FD) process is used to produce a composite 3D foam, which is a mixture of graphene nanoplatelet (GNP) and a low‐temperature co‐fired ceramic (LTCC). The freeze‐dried GNP‐LTCC reticulated 3D composite foam has an average pore size ranging from 70 to 100 μm. Pore size is varied by regulating the heat transfer rate during the freezing process using a thermally conductive aluminum (Al) mold and a thermally insulating acrylonitrile butadiene styrene (ABS) mold. Computational thermal modeling is used to visualize the heat transfer and its effect on foam pore size. Subsequently, a freeze‐dried GNP‐LTCC composite foam is embedded into the LTCC matrix to form a hierarchical assembly by a spark plasma technique without compromising the 3D structure of the FD foam. This study established that a simple, eco‐friendly, and scalable processing methodology can produce advanced graphene‐based 3D composite foams as the future tailorable nanofillers for designing multimatrix materials.

Study of the phase transition of a medium using reverberated signals

Non-destructive testing (NDT) methods nowadays are essential in materials and structures control due to their capability to not affect the integrity of material. These methods are particularly efficient for the monitoring of resin or composites formation. In particular, ultrasonic technics can be used to evaluate mechanical properties of materials by measuring acoustic waves characteristics. In general classical characterization techniques, based on linear measurements, give local information’s of medium. Reverberation methods, classically used in room acoustics, allow global characterization. This approach is not so common in NDT or structure monitoring. The reverberation signals which contain global information about propagation media properties, are highly dependent on the boundary conditions. Sabine’s formula gives the relationship between reverberation time RT and wall attenuation coefficient can be adapted in many acoustic applications. Previous studies established a relation between RT and solid interfaces absorption. In the case of a sol-gel material, the reverberation time measured in a metallic block can be linked to the material properties such as density or viscosity. The RT will vary during the phase transition of our material from liquid to solid state. Hence, our motivation is to derive the equation of the acoustic intensity for solid interface absorption considering the shear and the longitudinal waves. Furthermore, to estimate the reverberation time from the determined acoustic intensity (simulation part) and to compare the results with the experimental part. For this reason, experiments were performed to validate the simulation part. Measurements are preformed in an aluminium mold using five piezoelectric (PZT) patches, one being used as emitter and the others as receivers has been studied and it’s evolution is shown to lead to a good estimation of the phase transition time.

Evaluation of the flexural strength and surface roughness of dental material after immersion in coffee

This study was done in order to evaluate the changes in flexural strength and surface roughness in dental material restorations after immersion in coffee. Bars specimens (2mm x 2mm x 25 mm) of Z100 3M/ESPE were made according to ISO 4049 using aluminum molds. After curing, the specimens were then randomly divided into five groups and conditioned at 37°C in physiological serum. In all groups, except control, samples were immersed in coffee for ten minutes daily. In group A, the samples were immersed in coffee. For group B, after to be immersed in coffee, samples were immersed in distilled water for one minute. For group C, samples were immersed in mouthwash for one minute. For group D, samples were brushing for ten minutes, with load of 250g and 4250 cycles after all treatments the samples were stored in physiological serum again. In control group, samples were only stored in physiological serum. The five groups were then divided into 2 subgroups according storage time, six and nine weeks, respectively. Flexural strength was determined using three point bending test in a universal testing machine. All the tests were carried out at a room temperature and samples were maintained in physiological serum during the test. Surface roughness measurements were made using a surface roughness tester. All data were analyzed using one-way analysis of variance (ANOVA) followed by Dunnet tests. The ANOVA indicated no difference in the means of surface roughness and significant was observed for flexural strength between control group and one group (coffee).

Influence Of Different Led Curing-Units On Depth Of Cure and Micro-Hardness Of Nano-Hybrid Resin Composite

Purpose: To evaluate the effect of two second generation LED Light curing units and a third-generation polywave LED Ligth curing unit at three different irradiation durations on surface microhardness and detpth of cure of nanofilled composite resin material. Materials and Methods: EliparTM S10, EliparTM Deep Cure-S, VALO Cordless, was evaluated at 10s, 20s, 40s curing periods in this study. A nanofilled composite FiltekTM Z550 that contains camphorquinone as photoinitiator is used as test material. For microhardness test ninety 6 mm diameter, 4 mm deep cylindrical composite blocks in teflon molds were prepared. For each light source at each application times 10 specimen were prepared (n=10) and tested. Also ninety, 4 mm diameter, 6 mm deep cylindrical composite specimens in a split aluminum mold polymerized with three different light sources at three different durations (n=10) were tested for depth of cure measurement. Data were analyzed statistically by SPSS (Ver: 22.0) and significance test of the difference between the two means (Kolmogorov-Simirnov), the variance analysis, and the Tukey Test used. Results: The values of cure depth were found significantly higher at 40 seconds of irradiation time for all light sources used (p&amp;lt;0.05). Elipar Deep Cure-S showed the higher top surface microhardness at 40s polymerization (p&amp;lt;0.05) Conclusion: All light devices used in the study provided adequate polymerization of the nanofill composite at all application durations in this study. The highest polymerization depth and microhardness values were achieved at 40 sec. polymerization time for all LCUs.s

Comparison of Tensile Bond Strength of Addition Silicone with Different Custom Tray Materials Using Different Retentive Methods

To compare the bond strength of addition silicone with different commonly used custom tray materials by means of different retentive methods (mechanical, chemical, and a combination of chemical and mechanical methods). Fabrications of 90 samples of different tray resin materials were done using an aluminum mold. They were divided into three main groups. Perforations, adhesive application, and a combination of both were done according to the grouping of samples. Polyvinyl siloxane material (medium body) was loaded over the samples. A universal testing machine with a crosshead speed of 5 mm/minute was used to determine the tensile bond strength of tray resin samples to medium body impression material. Based on these values, Student's-test, group statistics, and ANOVA test were used for statistical analysis. Visible light cure (VLC) resin showed the highest bond strength in chemicomechanical methods. This was followed by repair resin material. Tray resin material showed poor bond strength in all three retentive methods. The mechanical method was the least retentive in all three resin materials. VLC tray resin material can be used with chemical and mechanical retention in clinical situations to make predictably accurate elastomeric impressions. It was concluded that VLC tray resin shows good bond strength with polyvinyl siloxane impression material when both mechanical perforations and adhesive applications were done.

Deburring Method of Aluminum Mould Produced by Milling Process for Microfluidic Device Fabrication

The existence of top burrs in micro-scale features produced by milling process can deteriorate the surface quality of a product. Ductile metals, such as aluminum alloys, are prone to suffer from top burrs formation after a slot-milling process. A brief review on the state-of-the-art of burr removal process in micro-scale milling is provided in this paper. Various deburring methods were reportedly able to remove the burrs in micro-scale features, however a much simpler method is still needed. In the present work, a deburring process by stainless steel end brushing is introduced for aluminum mould used in microfluidic device fabrication. The micro-scale features are produced by slot-milling process followed by the deburring process. The deburred moulds are then visually observed using optical microscope and Scanning Electron Microscope (SEM) and the average surface roughness and its features profile are measured using 3D Laser Scanning Confocal Microscope. As a result, the proposed deburring method can successfully remove the top burrs, as indicated by a height reduction of about 21% due to the removal action by the brush. Hence, a burr-free embossing mould with complex shape channel features can be produced by milling and by applying a simple deburring process using stainless steel end brush.

Mechanical and antimicrobial property of different surface treated glass ionomer cements under desiccated condition

The purpose of this in vitro study was to evaluate the effect of five different surface treatments on the mechanical property and antimicrobial effect of three desiccated glass ionomer cements. In this in vitro experimental study, 300 rectangular blocks of three different restorative materials were fabricated using an aluminum mold, Group I (n = 100) Micron bioactive, Group II (n = 100) GC Fuji IX GP Extra, and Group III (n = 100) bioglass R. These blocks were stored in 100% humidity for 24 h and then placed in air to desiccate for another 24 h. These groups were further divided into two major groups (n = 50) for both mechanical (Flexural) and antimicrobial testing. The blocks of mechanical and antimicrobial groups were further divided into five subgroups (n = 10) based on the medias used for surface treatment (senquelNaF, MI varnish, chlorhex plus, kedodent mouthwash, and 100% humidity [control]). Flexural strength (FS) was measured using the universal testing machine. Fracture strength of groups was compared using the one-way analysis of variance and Tukey's post hoc test with P ≤ 0.05 considered statistically significant. Antimicrobial effect was carried out by covering the specimens in a suspension of Streptococcus mutans followed by incubation for 24 h. The blocks were later washed, vortex mixed, serially diluted, and plated. Ccolony-forming unit/ml was calculated after 3 days of incubation. Data were then analyzed using the Kruskal-Wallis and Mann-Whitney U nonparametric test, with P ≤ 0.05 considered statistically significant. Micron bioactive with the surface treatment of MI varnish significantly exhibited highest FS. Surface treatment of desiccated restorative materials with chlorhex plus exhibited no growth of S. mutans. GC Fuji IX GP Extra with surface treatment of MI varnish exhibited highest reduction in S. mutans growth compared to other experimental group. Surface treatment of restorative material with MI varnish improved their mechanical and antimicrobial property while among three restorative materials Micron bioactive showed better mechanical property, whereas GC Fuji IX GP Extra exhibited better antimicrobial property.

Lingual retainer materials: Comparative evaluation of wear resistance of flowable nanocomposites and universal composite: An in vitro study

A bonded fixed retainer is used to stabilize the alignment of the teeth. Different composites have been introduced for this purpose. This study aimed to investigate the wear resistance of flowable nanocomposite in comparison with microhybrid composite in an in vitro situation. In this in vitro study, 46 disk-shaped specimens were divided into two groups: Filtek Ultimate flowable composite and Z250 microhybrid composite. The samples were prepared in 8 mm diameter and 3 mm thickness in an aluminum mold and light cured. They were polished with 600 grit sandpaper to achieve a smooth surface. Two-body wear test was accomplished by the pin-on-disk device (under 15 N, 20 rpm for 1 h). Analyzing the weight and thickness of specimens before and after the assay demonstrates the wear resistance. Data were analyzed using the t-test. P ≤ 0.05 was considered statistically significant. The Filtek Ultimate flowable composite shows no significant difference compared to Z250 microhybrid composite in thickness (P = 0.701) and weight (P = 0.939) of specimens. Due to wear resistance of both materials, flowable composite can be recommended as an alternative material for bonded fixed retainers.

Effect of Acidic Beverages on Color Stability and Microhardness of Various Esthetic Restorative Materials: A Comparative Study.

Aim:The aim of this study was to assess the effect of acidic beverages on color stability and microhardness of various esthetic restorative materials.Materials and Methods:A total of 60 samples were included in the present study. Group I: Microhybrid composite resin, Group II: Nanoceramic, Group III: ORMOCER (Organically Modified Ceramics). 10 mm internal diameter and 5 mm depth of cylindrical aluminum mold of were utilized to prepare the samples. All the esthetic restorative samples were submerged for 10 min in 25 ml of acidic drink (Coca-Cola) each day up to 15 days. Vickers diamond intender was used to measure the microhardness of each sample. These values were calculated with baseline, 7th, and 15th days for final microhardness values.Results:The mean surface microhardness of 63.20 ± 0.46 was shown by Group III which was slightly more than that in Group II (60.08 ± 0.34) and Group I (58.10 ± 1.76). Analysis of covariance did not show any statistically significant difference between the groups. The samples in Group I showed the highest reduction in surface microhardness value after immersion into acidic drink, followed by Group II and Group III on 7th day and 15th day. A statistically significant difference (P < 0.001) was found on the 7th day.Conclusion:The present study concludes that the Organically Modified Ceramics esthetic restorative material showed the finest behavior after being dipped in the acidic drink followed next by Nanoceramic and Microhybrid composite resin.

Application of Magnetic Concentrator for Improvement in Rapid Temperature Cycling Technology.

The main method to improve the filling of the cavity by the polymer melt is to increase the mold temperature. Rapid temperature cycling (RTC) technologies have been used around the world for several years, improving the quality of injection molded parts with a slight extension of production time. The present work focuses on the application of induction heating technology in the injection molding process since it is the most effective and most intensively developing method of heating in modern RTC technologies. In this research, the application of the induction heating process for selected surfaces was investigated with particular emphasis on the dynamics of the process. The numerical simulations were used to study the influence of the number of coils, the distance between coils and cavity surface and the mold material was examined with and without the presence of a magnetic concentrator. According to the obtained results, several crucial conclusions were made: the efficiency of heating is directly correlated with the distance between the inductor and the mold surface, the presence of magnetic flux concentrator significantly improves the homogeneity of temperature distribution and heating efficiency, application of aluminum mold lowers the obtained surface temperature.

Ultra-Wideband Trident Inset-Fed Monopole Antenna With a 3-D Conical Ground

An ultra-wideband antenna with a conical ground and trident inset feeding structure is presented. The antenna consists of a U-shaped monopole designed on a printed circuit board and a three-dimensional conical aluminium mold, serving as the ground. Low frequency ( $ GHz) matching is achieved with the trident feed branches by inserting them into the monopole. Simulation studies show that the proposed 3-D conical ground outperforms horizontal or flat-lying ground models in terms of impedance matching bandwidth and radiation pattern omni-directivity. The 3-D ground also helps to stably mount the antenna in a measurement facility. Simulation and measured results presented in this paper demonstrate that the proposed antenna is suitable as a testing antenna with omnidirectional radiation patterns over a broad bandwidth. A 14.6:1 bandwidth ratio (0.56 - 8.2 GHz) has been realized at a voltage standing wave ratio below 2:1 with antenna gain above 2 dBi.