Metal Mold Research Articles

State-monitoring and product quality measurement of additively manufactured injection mould inserts

Additive technologies represent a state-of-the-art and innovative way in today’s mould making. They allow production of both metallic and polymeric moulds with relative simplicity and flexibility compared to conventional machining. Despite its possible benefits, this area is scarcely researched. In our work, we analysed in-mould applicability of epoxy-acrylate inserts manufactured by PolyJet technology. We created a comprehensive state monitoring method to quantify important process parameters like cavity pressure, strain and temperature of the inserts. We analysed the effect of holding pressure on the resulting cavity pressure and strain of the insert. We showed that strain of the insert gradually increased after the cycles and we identified characteristic segments of the injection moulding cycle on the strain-time curves. We also applied surface temperature measurements using a thermal imaging camera. The purpose of this measurement was to determine necessary delay time between cycles allowing inserts to cool below heat deflection temperature, so early failure could be prevented. By using thermal imaging camera, we measured cavity surface temperature distribution and demonstrated the effect of low thermal conductivity of the insert material. We also measured thickness and weight variation of injection moulded products to show the effect of holding pressure and mould deformation on final product quality. As we applied higher holding pressures, product mass and average product thickness grew.

Comparison of Three Additive Manufacturing (AM) Techniques for Manufacturing Complex Hollow Composite Parts

AbstractAdditive manufacturing (AM) is well known for supporting the manufacturing of composites through the 3D printing of lay‐up tools, sacrificial mandrels, trim molds, etc. The fused deposition modeling (FDM) is a pioneer in composite tooling. This technique is advantageous in many scenarios in which it is convenient to obtain hollow composite parts by dissolving sacrificial mandrels, removing the use of expensive and heavy metal molds. However, the effects that the removal process has on the thermomechanical properties of the composite must be considered. The convenience of another AM technique, liquid crystal display (LCD) printing, has also recently been demonstrated. The present work aims to compare three different techniques, FDM, fused filament fabrication (FFF), and LCD, each using different materials and, therefore, different mandrel removal processes. DMA analyses have highlighted the impact of some dissolution processes on thermomechanical properties. Further mechanical analysis is conducted to support what is found in the thermomechanical characterization tests. Finally, an economic analyses highlight the time and cost savings of some AM technologies compared to the conventional method for manufacturing composite parts.

Effect of Mold Material on Shrinkage of Investment Casting Wax Pattern

Various attempts have been made to substitute metal as the wax pattern mold material due to manufacturing costs and time-consumption. This research investigates the linear and volume shrinkage on the wax pattern of gypsum, silicone rubber, and epoxy resin as alternative materials to metal molds. A nylon master pattern was made by machining. The master pattern size was set as a reference for dimensional comparison with the cast wax pattern. Wax pattern molds were created using the master pattern, namely gypsum, silicone rubber, and epoxy resin. Paraffin wax was heated up to 55˚C in metal, then poured into each wax pattern mold. The length, radius, inlet, and outlet diameter were measured using a profile projector, then the linear shrinkage was calculated. The volume shrinkage was obtained through the sample weighing. The results show that silicone rubber has the lowest linear shrinkage of any sample in contrast to its volume shrinkage.

Hierarchical macro to nano press molding of optical glasses by using metallic glasses

The fabrication of ideal optical components is a world-wide grand challenge facing us. Benefiting from the unique thermoplastic nature, precision glass molding (PGM) is considered as a promising method for rapid and precise fabrication of optical components. The success and proliferation of such methods critically rely on the manufacturing of robust and durable master molds. Although silicon-based molds relying on photolithographic forming are facile to manufacture, they are brittle and have limited longevity when used as the molds. To address this challenge, here, we propose a hierarchical macro to nano mold preparation method based on the thermoplastic forming ability of metallic glasses (MGs), which excels in micro and nano scale fabrication. After subsequently crystallizing the as-formed MG, we demonstrate that the crystalline MG is suitable as an excellent mold for molding optical glasses with service temperature up to 600 °C. Using this ‘spawning’ process, several metallic molds including macroscopic lens arrays, microscale gratings, and nano-lens arrays were successfully prepared, respectively. The minimum feature size of the mold is 300 nm and the optimum surface roughness is 7.43 nm. Correspondingly, we prepared hierarchical optical glass components with excellent optical properties using MG as molds.

Biocomponents Based on Hydroxiapatite: Influence of Sterilization on the Mechanical Resistance.

Objective This study aimed to evaluate the influence of sterilization on the compressive and flexural mechanical strength of hydroxyapatite-based biocomponents obtained through freeze-dried bovine bone, and its association with chitosan. Methods Freeze-dried bovine bone was processed into 100 μm particles and mixed with 50% of its weight in chitosan. The mixture was packed in metallic molds for preparing the specimens, and sterilized at 127°C using an autoclave for subsequent experimentation. The specimens were subjected to compression and flexion tests following norm 5833 of the International Organization for Standardization (ISO), with 6 × 12 mm cylindrical blocks (for compression tests) and 75 × 10 × 3.3 mm plates (for flexion tests) as samples. The samples were divided into four groups of 20 specimens each, with 10 for compression and 10 for flexion tests. Three groups were sterilized (autoclave, gamma rays, and ethylene oxide), whereas the fourth group (control) was not. The mechanical tests obtained from the different sterilization processes were compared using analysis of variance (ANOVA, p < 0.05), followed by the Tukey multiple comparison test of means, with a 95% confidence interval. Results The specimens presented mean compressive strengths of 10.25 MPa for the control group and 3.67 MPa, 9.65 MPa, and 9.16 MPa after ethylene oxide, gamma ray, and autoclave sterilization, respectively. Flexion test results showed an average resistance of 0.40 MPa in the control group, and 0.15 MPa, 0.17 MPa, and 0.30 MPa after ethylene oxide, gamma ray, and autoclave sterilization, respectively. There were statistically significant differences observed in the maximum compression of the ethylene oxide-sterilized group compared with that of the control group ( p = 0 . 0002), gamma ray-sterilized ( p = 0.0003), and the autoclaved ( p = 0.0006) groups. There was a statistically significant difference in maximum flexion of the specimens sterilized by gamma rays when compared with the control group ( p = 0.0245). However, low flexural strengths were observed in all specimens. Conclusion The autoclave sterilization group did not result in statistically significant differences in either compression or flexion strength tests. Thus, the autoclave proved to be the best sterilization option for the hydroxyapatite-based biocomponents in this study.

Effect Of Nano-Bioactive Glass On Flexural Strength And Antimicrobial Activity Of Resin-Modified Glass Ionomer Cement Containing 58S Nano-Bioactive Glass

Introduction: Bioactive glass (BAG) is increasingly used in dentistry, aiming to provide superior mechanical properties, optimal chemical stability, and favorable antimicrobial activity in the oral environment. This study aimed to measure the flexural strength (FS) and antimicrobial activity of resin-modified glass ionomer (RMGI) cement containing 58S nano-BAG. Materials and Methods: In this in vitro study, 0wt (Weight) %, 10wt%, 20wt%, and 30wt% 58S nano-BAG particles were added to RMGI powder in groups 1 to 4, respectively (n=10). Forty specimens were fabricated in metal molds (2 x 25 x 2 mm), and their FS was measured by using a three-point bending test at a crosshead speed of 0.5 mm/min. The antibacterial activity of the materials against Streptococcus mutants was assessed by the disc diffusion test. In addition to the abovementioned experimental groups, one control group (n=10) containing 100% BAG was also considered. Data were analyzed by one-way ANOVA and Tukey’s test. Results: The mean (± standard deviation) FS was 38.71±8.84, 43.61±17.34, 45.62±15.89, and 54.71±14.25 MPa in groups 1 to 4, respectively. No significant difference was noted in FS among the groups (P=0.06). A significant difference was found in the diameter of the growth inhibition zone among the groups (P&lt;0.05), and group 4 containing 30wt% BAG showed minimal bacterial growth. Conclusion: The addition of 10wt%, 20wt% and 30wt% nano-BAG to RMGI powder did not significantly change the FS but the addition of 30wt% nano-BAG to RMGI significantly inhibited the bacterial growth.

Effect of the Type of Inorganic Binder on the Microstructure and Properties of AlSi7Mg Alloy Castings Made by Ablation Casting Technology.

The results of studies on the effect that the type of binder and casting technology exert on the microstructure and properties of AlSi7Mg alloy castings are discussed in this paper. Comparative tests were carried out on three casting manufacturing technologies, i.e., conventional sand mould casting and cooling process, metal mould (die) casting, and sand mould casting with ablation breakdown of mould and cooling of castings. Moulds were made from four different sand mixtures with inorganic binders hardened by various technologies. The microstructure of test castings was examined at three different levels, i.e., in the upper part, central part, and lower part of each casting. The tensile test at room temperature was carried out in accordance with standards. The experimental results showed differences in the microstructure of castings. The differences resulted from changes in the crystallisation path due to the use of three different casting technologies, ensuring different rates of heat dissipation from castings; they were also due to the shape of castings. It has been shown that castings made by ablation technology are characterised by a high degree of the microstructure refinement (SDAS reduced by 18–30%), which gives higher strength properties than the properties of castings made in conventional sand moulds. Samples taken from castings made by the ablation technology in moulds with phosphate binder and microwave-hardened geopolymer binder were characterised by the mechanical properties comparable to gravity die castings.

The Effect of Scandium on the Microstructure of the Aluminium Alloy AA 6086

The investigation studied the effects of 0.2 wt.% and 1 wt.% scandium (Sc) additions on the microstructure of the aluminium alloy AA 6086 in different conditions. The alloys were produced by casting into a metallic mould, followed by various heat treatments. The alloys were examined using light microscopy, scanning and transmission electron microscopy, microchemical analysis, differential scanning calorimetry and X-ray diffraction. The phase compositions and solidification sequences were modelled using the CALPHAD approach, which reasonably agreed with the experimental results. The addition of Sc to AA 6086 strongly reduced the grain size of the Al-rich solid solution and induced the appearance of Sc-rich phases AlSc2Si2 and L12-Al3X. Other phases identified in the Sc-free alloy were also found in the Sc-modified alloys. Homogenisation caused the dissolution of most phases and the formation of different types of dispersoids. In the alloy with 0.2% Sc, the distribution of dispersoids was not uniform. The plate-like AlMnCrSi dispersoids formed mainly at the dendrite centres, together with spherical L12 precipitates, while smaller α-AlMnSi and tetragonal t-Al3Zr dispersoids were created elsewhere. The addition of 0.2% Sc did not considerably affect the strengthening of AA 6086. The precipitation during isothermal ageing was slightly delayed and shifted to higher temperatures during continuous heating.

Investigation on characteristic and formation mechanism of porosity defects of Al–Li alloys prepared by sand casting

Porosity defects and interfacial reaction are very serious problems in sand casting Al–Li alloy, which greatly affect the quality of castings. In this work, the characteristic and formation mechanism of the porosity defects in the sand casting Al–Li alloys were systematically investigated by scanning electron microscopy, transmission electron microscopy, energy spectrometry, and inductively coupled plasma mass spectrometry, in order to provide a theoretical basis for the prevention and control of the pore defects in the sand casting Al–Li alloys. The results found that the Al–Li alloys prepared by metal mold and graphite mold as casting molds had almost no pore defects and interfacial reaction layers, with the porosities of 5.81% and 5.05%, respectively, while the sand casting Al–Li alloys with furan resin, phenolic resin, and sodium silicate binder as binders all had serious pore defects and interfacial reaction layers, with the porosity of 15.67%, sharply weakening the mechanical properties of the Al–Li alloy casting. The types of the pore defects were mainly reactive pores and intrusive pores, and the interface reaction layer was mainly composed of LiAlO2 and C–H–O organics. The formation mechanism of the pore defects in the sand casting Al–Li alloys was caused by the reaction between Li and the hydroxyl groups in the binder of the sand mold to generate a large amount of hydrogen, which intruded into the melt or was sucked into the melt.

CNT 면상발열체 적용을 위한 다층 구조 사출 금형의 급속가열 성능에 관한 연구

As a heating method for RHCM (Rapid Heating Cycle Molding) various heating technologies such as high frequency induction heating, IR heating, gas heating, and high temperature steamare applied, but these methods are not satisfying high productivity due to low energy efficiency. Research has been actively conducted on RHCM based on planar heating elements with high heating efficiency, such as carbon nanotubes, which are applied. To apply the CNT web film to the RHCM, a heating element must be applied inside the injection mold and power must be applied. As electricity is directly applied to the CNT web film to generate heat, all mold parts in contact with the CNT web film must be insulated, and high heat transfer is required for rapid heating performance. Thus, in this study, a multi-layer structure mold module for insulation and high heat transfer was designed to enable rapid heating by applying a CNT web film as a heat source. To this end, we intend to present a research direction for the commercialization of rapid heating molds, by identifying the main variables of rapid heating through heating experiments by the mold metal and insulator materials, and reflecting them in the mold design.

Study on solution and aging heat treatment of a super high strength cast Mg-7.8Gd-2.7Y-2.0Ag-0.4Zr alloy

Mg-7.8Gd-2.7Y-2.0Ag-0.4Zr (wt.%) alloy was prepared by traditional metal mold gravity casting, and then was solutionized and aged. The solution and aging processing were optimized, the microstructure evolution during solution and aging of the alloys was investigated, the isothermal aging hardening process was studied, and the room temperature tensile properties and strengthening mechanism of the alloys were studied. The results show that alloys exhibit obvious double peak aging characteristics during the isothermal aging process due to the precipitation process difference of β′ and γ″, and a higher aging temperature is beneficial to shorten the time to peak hardness. The optimal solution and aging parameters were 510 °C for 6 h and 200 °C for 32 h, respectively. The lattice distortion of α-Mg caused by Ag is much greater than that of Gd and Y, so the strengthening effect of Ag is the most significant. The yield strength, ultimate tensile strength, and elongation of the alloy after the optimized solution and aging process reach 273.1 MPa, 410.7 MPa, and 4.85%, respectively. The contribution of precipitation strengthening to the yield strength of alloy after aging at 200 °C and 225 °C is about 51%.

Preparation of PMMA/SiO2 Composite Sheets for Tribological and Mechanical Tests

This paper aims to prepare PMMA sheets (Polymethyl methacrylate sheets) reinforced with SiO2 nanoparticles (Silicon oxide nanoparticles) to obtain samples for tribological and mechanical tests. PMMA reinforced sheets are prepared by three methods; dissolving, pressing, and casting. In the first method, the pure PMMA granules were dissolved with an organic solvent. The SiO2 nanoparticles were dispersed using a magnetic stirrer. Then, the solution was poured into a glassy mold. In the second method, pure PMMA powder was used, and SiO2 nanoparticles were dispersed using a nanoparticle disperser device; then, the mixture was placed in a metal mold and pressed by a thermo-hydraulic press. While in the third method, pure PMMA resin and hardener were used, and SiO2 nanoparticles were dispersed using an ultrasonic probe machine, and then the mixture was poured into a glassy mold. The three preparation results showed that the obtained sheets were free of bubbles and that their surfaces were of excellent smoothness and could be cut using a laser to obtain the samples required for tribological and mechanical tests such as tensile test, impact test, wear test, surface hardness test, surface roughness test, and scratch resistance test and others.

Mechanical characteristics of Biomaterial Particles Reinforced Epoxy Resin Composites for Automobile Accessories

Abstract In this study, rattan corncob composite materials were developed and their mechanical properties were determined. This was with a view to producing alternative composite materials for automobile applications. Dried corncobs and rattan cane were crushed, treated with caustic alkali NaOH (aq) and transferred into a water bath machine to reduce the hydrophilic nature of the fibres in the polymer. The shredded corncobs and rattans cane were sun-dried after the treatment to remove the moisture content and were further pulverized and sieved to obtain 400μm particle size. Compositions of the particles were varied for seven samples with the binder kept constant at 80wt% of the whole mixture and forming them into particle panels using a metal mould. The process was repeated in order to obtain three replicates to get the exact mean value. The produced panels were tested for density, water absorption, tensile strength and modulus, flexural strength and modulus, and optical microstructure. The results revealed that the densities ranged between 1.06g/cm3 to 1.30g/cm3, the water absorption properties ranged between 0.87% to 4.55%, tensile strength ranged between 42MPa to 90MPa, tensile modulus ranged between 2.2GPa to 5.9GPa, flexural strength ranged between 50MPa to 70MPa and flexural modulus ranged between 1.5GPa to 2.7GPa. It was concluded that the developed composite materials have good mechanical properties and could serve as alternative materials for making automobile accessories like bumpers and spoilers. It could also help in solving the problem of environmental pollution caused by open burning.

Development of Sustainable Artificial Stone Using Granite Waste and Biodegradable Polyurethane from Castor Oil

Brazil is one of the world’s major ornamental stone producers. As a consequence, ornamental stone wastes are generated on a large scale and are usually open air disposed. Thus, it is important to develop novel material reusing these accumulated wastes, aiming to minimize environmental impact. The development of artificial stones made with ornamental stone wastes agglomerated by a synthetic polymer represents an excellent alternative and, therefore, is currently the subject of several works. This work seeks to develop an innovative artificial stone containing 85%wt of granite waste and 15%wt of vegetable polyurethane from castor oil, a biodegradable resin, from a renewable source. The purpose is creating a sustainable material, technically viable to be applied as a civil construction coating. To manufacture the artificial stone plates, granite and polyurethane were mixed and transferred to a metallic mold subjected to vibration, vacuum and, later, hot compression. The artificial stone presented low water absorption (0.13%) and apparent porosity (0.31%) as well as a favorable 17.31 MPa bend strength. These results were confirmed through the excellent particles/matrix adhesion displayed in the micrographs, in addition to great chemical resistance.

Shape and position design of two-step micro-channel on plate during rubber pad forming process based on simulation

Rubber pad forming is an advanced processing technology to form the metal sheet. The micro-channel on the plate can be formed by both rubber pad and the metal mold. With the development of micro-channel, a two-step micro-channel has been applied in more and more fields such as fuel cell bipolar plate. However, little attention was given to the forming strategy for these unique channels. In this paper, the rubber pad forming process is used to form the entire SS304 sheet with two-step channels. In order to design the micro-channel structure with good formability, the main parameters of the two-step micro-channel are discussed through finite element modeling (FEM) and forming experiment. Not only for the geometric parameters for structures like length, width, edge chamfer, and the height ratio of first to second step, but also for the spatial distribution like the number and distance of two-step micro-channels in the entire plate. In addition, MATLAB is used to study the influences on the final forming results because of the various parameters. And then, the plates can be precisely formed when the structure is suitable, while micro-channels with unsuitable structure cannot be formed as designed. Finally, based on the FEM and forming experiment results, a design strategy is provided in the conclusions.

Diselenide as a Dual Functional Mechanophore Capable of Stress Self-Reporting and Self-Strengthening in Polyurethane Elastomers

Diselenide as a Dual Functional Mechanophore Capable of Stress Self-Reporting and Self-Strengthening in Polyurethane Elastomers

Quality of automotive sand casting with different wall thickness from progressive secondary alloy

Abstract This paperwork is focused on the quality of AlSi6Cu4 casting with different wall thicknesses cast into the metal mold. Investigated are structural changes (the morphology, size, and distribution of structural components). The quantitative analysis is used to numerically evaluate the size and area fraction of structural parameters (α-phase, eutectic Si, intermetallic phases) between delivered experimental material and cast with different wall thicknesses. Additionally, the Brinell hardness is performed to obtain the mechanical property benefits of the thin-walled alloys. This research leads to the conclusion, that the AlSi6Cu4 alloy from metal mold has finer structural components, especially in small wall thicknesses, and thus has better mechanical properties (Brinell hardness). These secondary Al-castings have a high potential for use in the automotive industry, due to the thin thicknesses and thus lightweight of the construction.

Synthesis and properties of foams from a blend of vegetable oil based polyhydroxyurethane and epoxy resin

This article aims to highlight the synthesis of foams from a blend of hydroxyurethane of castor oil and epoxy resin. An epoxidized castor oil of 4% oxirane oxygen was first converted to cyclic carbonate of castor oil at 120°C, 1 atm CO2 pressure and then it was reacted with three different aliphatic diamines to yield amine terminated Polyhydroxyurethane (PHU). Foams were prepared in a metal mould from the blend of PHU, epoxy resin, epoxy hardener and polymethylhydrogensiloxane blowing agent which releases hydrogen gas upon reaction with amine. FTIR and 1H NMR of cyclic carbonate of castor oil and PHU of castor oil were done to confirm their chemical structures. Optical microscopy and scanning electron microscopy of foams was done to assess their cellular morphology along with DSC and TGA to evaluate their thermal properties. Both flexible and rigid type of foams were synthesised in this study. Resilience of flexible foams was inspected using a ball rebound test and compression-recovery test while thermal insulation property was checked by measuring thermal conductivity, thermal diffusivity and R-values of rigid foams from heat transfer study using a heat transfer apparatus.

Depth of cure of 10 resin-based composites light-activated using a laser diode, multi-peak, and single-peak light-emitting diode curing lights

ObjectivesTo evaluate the depth of cure (DOC) of ten contemporary resin-based composites (RBCs), light-cured using different LCUs and exposure times. MethodsThe power, radiant emittance, irradiance, radiant exposure (RE), and beam profiles from a laser (M, Monet), a multi-peak (V, Valo Grand), and single-peak (S, SmartLite Pro) LCU were measured. The DOC was measured using a 6-mm diameter metal mold and a solvent dissolution method to remove the uncured RBC. The length of the remaining RBC was divided by 2. The exposure times were: 1 s and 3 s for M, 10 s and 20 s for V, and 10 s and 20 s for S. Data were analyzed using: Bland-Altman distribution, Pearson's Correlation, and an artificial neural network (ANN) to establish the relative importance of the factors on the DOC (α=0.05; β=0.2). ResultsSignificant differences were found in the DOC achieved by the different LCUs and composites. The laser LCU emitted the highest power, radiant emittance is used above and in the tables and delivered the highest irradiance. However, this LCU used for 1 s delivered the lowest RE and produced the shortest DOC in all ten RBCs. The ANN demonstrated that the RE is the most critical factor for the DOC. Bland-Altman comparisons showed that the DOCs achieved with the laser LCU used for 1 s were between 17 and 34% shorter than the other conditions. ConclusionsAlthough the laser LCU cured all 10 RBCs when used for 1 s, it produced the shallowest DOC, and some RBCs did not achieve their minimum DOC threshold. The RE and not the irradiance was the most important factor in determining the DOC of these 10 RBCs. Clinical significanceDespite delivering high power and irradiance, the laser used for l s delivered a lower radiant exposure than the conventional LCUs used for 10 s. This resulted in a shorter DOC.

Analysis and Advances in Additive Manufacturing as a New Technology to Make Polymer Injection Molds for World-Class Production Systems.

The currently growing demand for metallic and polymeric products has undoubtedly changed the rules of manufacturing, enabling customers to more functionally define their products based on their needs. Nowadays, a new technique for rapid tooling, Additive Manufacturing (AM), can create customized products with more complex geometries and short life cycles (flexibility) in order to keep up with the new variables imposed by the manufacturing environment. In the last two decades, the migration from subtractive manufacturing to AM has materialized such products with reduced costs and cycle times. AM has been recently promoted to develop polymer molds for product manufacturing. This paper reviews the main findings in the literature concerning polymer molds created by AM compared to conventional (metal) molds obtained by subtractive manufacturing. Information about specific topics is scarce or nonexistent, for example, about the characterization of the most commonly injected materials and molds used in this type of technology, their mechanical properties (part and mold), designs for all types of geometries, and costs. These aspects are addressed in this literature review, highlighting the advantages of this alternative manufacturing process, which is considered a desirable technology worldwide.