Mold Surface Research Articles

Metal Additive Manufacturing of Plastic Injection Molds with Conformal Cooling Channels.

Conformal cooling channels (CCCs) are widely used in the plastic injection molding process to improve the product quality and operational performance. Tooling that incorporates CCCs can be fabricated through metal additive manufacturing (MAM). The present work focuses on the MAM of a plastic injection mold insert with different CCC types that are circular, serpentine, and tapered channels with/without body-centered cubic (BCC) lattices. The entire manufacturing process of the mold insert is explained from the design step to the final printing step including the computational thermal & mechanical simulations, performance assessments, and multiobjective optimization. Compared to the traditional channels, conformal cooling channels achieved up to 62.9% better cooling performance with a better thermal uniformity on the mold surface. The optimum mold geometry is decided using the multiobjective optimization procedure according to the multiple objectives of cooling time, temperature non-uniformity, and pressure drop in the channel. Direct Metal Laser Sintering (DMLS) method is used for manufacturing the molds and the quality of the printed molds are analyzed with the X-ray Computed Tomography (X-ray CT) technique. The errors between the design and the printed parameters are less than 5% for the circular and tapered channels while the maximum deviation of the strut diameters of the BCC is 0.06 mm.

Airfoil Surface Forming and Conformity Test Using Laser Tracker

In this study, NACA0018 airfoil surface conformity test was conducted using API tracker3 in combination with SpatialAnalyzer (SA) and modeling software SolidWorks. Plaster of Paris is used as a plug making material and a woven-type fiberglass is used as mold and airfoil surface making material. For airfoil surface analysis, three-dimensional model of the airfoil surface was developed in SolidWorks software and imported in IGES file format to SpatialAnalyzer (SA) software. Then, measurements were taken from manufactured airfoil surface using laser tracker through surface scanning method. Surface conformity test was conducted through fitting of measured points to surface model imported from SolidWorks to SpatialAnalyzer (SA) software. The optimized fit summary result shows that the average fit difference is 0.0 having standard deviation from 0.22224 from the average and zero with RMS of 0.2210. The maximum magnitude of the difference including x and y together is 0.5336 and the minimum −0.5077. Thus, with a given range of surface quality specification, laser tracker is an easy and reliable measurement and inspection tool to be considered.

Research on the End-Face Distribution of Rotational Molding Heating Gun Based on Numerical Simulation Method

The distribution of heating gun ends plays a decisive role in the sidewall properties of finished rotomolded products. To obtain the optimal distribution of the end face of a rotational molding heating gun, the temperature response of the end-face mold under heating gun heating was investigated, and an analysis method based on numerical simulation is proposed. The FDS (fire dynamics simulator) was used to construct a heating model of the heating gun, simulate and obtain a heatmap of the temperature field distribution of a heating gun of Φ30–70 mm, and determine the optimal diameter and heating distance of the heating gun. ANSYS was used to establish the thermal response model of the heat-affected mold, which was combined with the mold structure and thermophysical properties of steel. A temperature field distribution on the inner wall surface of Φ30, Φ50, and Φ70 mm heating guns when heating at each diameter of the end face was obtained and the distribution position of the end face of each diameter heating gun was determined. ANSYS was used to establish the thermal response model of the end-face mold and obtain the temperature field distribution of the inner wall surface of the end-face mold. The size of the heat-affected area of each diameter heating gun was combined, the end-face heating gun distribution was optimized, and the optimal heating gun end-face distribution was obtained. An experimental platform was built, and a validation experiment was set up. Through the analysis and processing of the data of three experiments, the temperature variation curve of each diameter on the inner surface of the end-face mold was obtained. We compare and analyze the simulation and experimental results to determine the feasibility of the FDS + ANSYS method and the correctness and accuracy of the simulation model and the results.

Adaptive Conformal Cooling of Injection Molds Using Additively Manufactured TPMS Structures.

In injection molding, cooling channels are usually manufactured with a straight shape, and thus have low cooling efficiency for a curved mold. Recently, additive manufacturing (AM) was used to fabricate conformal cooling channels that could maintain a consistent distance from the curved surface of the mold. Because this conformal cooling channel was designed to obtain a uniform temperature on the mold surface, it could not efficiently cool locally heated regions (hot spots). This study developed an adaptive conformal cooling method that supports localized-yet-uniform cooling for the heated region by employing micro-cellular cooling structures instead of the typical cooling channels. An injection molding simulation was conducted to predict the locally heated region, and a mold core was designed to include a triply periodic minimal surface (TPMS) structure near the heated region. Two biomimetic TPMS structures, Schwarz-diamond and gyroid structures, were designed and fabricated using a digital light processing (DLP)-type polymer AM process. Various design parameters of the TPMS structures, the TPMS shapes and base coordinates, were investigated in terms of the conformal cooling performance. The mold core with the best TPMS design was fabricated using a powder-bed fusion (PBF)-type metal AM process, and injection molding experiments were conducted using the additively manufactured mold core. The developed mold with TPMS cooling achieved a 15 s cooling time to satisfy the dimensional tolerance, which corresponds to a 40% reduction in comparison with that of the conventional cooling (25 s).

Quantitative Evaluation of Fracture Morphology on 2DP-GFRP by AE Method

The addition of particulate flame retardant to matrix resin is required in order to apply GFRP in the field needed the nonflammability because GFRP doesn’t have fire resistance. However, this method accompanies the increase in resin viscosity. We focused on GFRP that has the two diameter particles added (2DPGFRP) for the compatibility of the suppression of increased viscosity and the grant of non-flammability. In our past study, the 2DPGFRP was showed to have unique mechanical properties that the difference in bending strength depending on which the resin applied surface (Top side) and the mold surface (Bottom surface) is tensile side. That mechanical properties were clarified qualitatively using the AE method etc. in that study. However, the detailed consideration about parameters except the AE count has not been concluded in our past study. The consideration about these parameters is expected to be clarified quantitatively the detailed fracture behavior. In this research, the fracture mechanism on 2DPGFRP was clarified by detailed AE measurement.

Quantitative Evaluation for Effect of Moisture on Fracture of 2DPGFRP by AE Method

The addition of particulate flame retardant to matrix resin is necessary when GFRP with no flammability is applied to the field needed that property. However, that method accompany the increase in resin viscosity. The increase in resin viscosity affects the formability of GFRP and it cause the decline of mechanical properties. Therefore, we focused on GFRP that has the two diameter particles added (2DPGFRP) for the compatibility of the suppression of increased viscosity and the grant of non-flammability. In our past study, the 2DPGFRP was showed to have unique mechanical properties that the difference in bending strength depending on which the resin applied surface (Top side) and the mold surface (Bottom surface) is tensile side. In addition, the origin of fracture on 2DPGFRP is confirmed with the interface of particle/resin instead of the interface of fiber/resin which is the origin of fracture on general GFRP. Furthermore, the origin of fracture was changed from the interface of particle/resin to interface of fiber/resin due to containing moisture into the specimen, and the decline of bending strength by that phenomenon. The quantitative evaluation about this phenomenon is an important issue for the practical application of 2DPGFRP. However, the quantitative reports about that are few. Therefore, in this research, the quantitative evaluation for the effect of moisture for the fracture behavior of 2DPGFRP using the data obtained by AE measurement was conducted.

Investigation of High Adhesion Factors in Adhesion and Peel Tests of Si-DLC Coating and PEEK

Against the background of growing needs for super engineering plastics in CFRTP molding, we verified the effect of Si-DLC on reducing the peel-off strength between molded resin and mold surface. In particular, we focused on whether or not a sufficiently low peel-off strength could be achieved without using a mold release agent by applying Si-DLC to the surface where PEEK material is melted and solidified. The PEEK specimen is given a melting-solidification temperature history on three types of metals or DLC films (SUJ2, Si-DLC, ta-C), and the adhesion interface is peeled off at a peeling temperature after solidification. In SUJ2, the peel-off strength increased monotonically from 8.10 to 21.09 MPa as the peeling temperature increased from 30 °C to 130 °C, which is near the glass transition temperature of PEEK. When Si-DLC was applied, the peeloff strength was not smaller than that of SUJ2.

Influence of surface roughness of die sinking EDM on mold releasability in compression molding of thermosetting phenol resin

Improvement in metal mold characteristics such as wear resistance, corrosion resistance and mold releasability is essential for plastic molding. In this study, factors of the mold releasability were investigated by quantitative evaluations of adhesion forces between the processed metal mold surfaces and the molded resins in compression molding of thermosetting phenol resin. Die sinking EDM was employed as the processed surfaces of the metal molds. As the mold releasability tests, the molded thermosetting phenol resin onto the EDMed surface was pulled up in the perpendicular direction from the surface. Consequently, the mold releasability could be quantitatively evaluated by measuring a maximum tensile load which means a mold release force when the molded resin is separated from the EDMed surface.Several workpieces with different surface roughness as the EDMed surfaces were prepared by varying discharge currents and pulse durations. As a result of investigations on relationships between surface roughness parameters and measured mold release forces, the mold release forces tended to increase as maximum height roughness RZ and average length RSm of the surface roughness parameters increase. On the other hand, the mold release forces tended to decrease as peak count RPc increases. Accordingly, it is considered that anchor effects become higher with increase of undulation on the EDMed surfaces. Therefore, the undulation is one of the factors affecting the mold releasability, and it would be possible to improve the mold releasability by reducing the undulations on the EDMed surfaces with EDM conditions.

Effects of physical and chemical properties of ceramic hand moulds on natural rubber latex glove film formation

Plaster and stoneware hand moulds were fabricated and used in the NR latex glove preparation. The raw materials characteristics combined to influence the hand mould surface properties through the adhesion-cohesion force, interfacial tension, contact angle, packing density. The stoneware hand mould fired at 800°C, fabricated from a smaller particle size distribution, with high zeta potential and interfacial interaction, and high specific surface area was shown to be superior to the plaster hand mould typically used in making NR latex products. The obtained NR latex films were characterised for various physical properties, namely appearances, thickness, tackiness, porosity, smoothness, optical clarity, and effusion.

Mould Surface Sampling Techniques and Collection Efficiency on Paper-Faced Gypsum Board

Surface sampling techniques for non-viable fungi in building environments are useful tools for investigators in determining hazards to occupants. However, data regarding capture efficiency in this context is limited. Our data demonstrates that collection efficiency of Bio-Tape surface capture medium on paper-faced gypsum board only captures between half and three-quarters of mould present on the surface. Surface sampling using a dry-swab technique showed similar efficiency of capture to tape lift samples. ‘Surface air’ samples had poor collection efficiency and should be avoided where possible in preference to other sampling options. Finally, we propose a sampling strategy based on non-viable microscopy techniques followed by molecular analysis for validation and speciation of samples of interest. Improvements in sampling and data analysis techniques for mould sampling of buildings will aid in providing meaningful results to help building inspectors evaluate health hazards.

High-dose-rate skin brachytherapy with interstitial, surface, or a combination of interstitial and surface mold technique.

PurposeIn order to demonstrate capabilities of brachytherapy in skin cancer treatment, we reviewed clinical outcomes of patients with non-melanoma skin cancer (NMSC) treated with high-dose-rate brachytherapy (HDR-BT) at a single-institution.Material and methodsA surface custom mold (SC), interstitial (IS), or a combination of IS and SC applicator (IS + SC) was used for treatment based on depth of tumor invasion. Contoured growth tumor volume plus a 0.5 cm margin for basal cell carcinomas (BCC) and a 1-1.5 cm margin for squamous cell carcinomas (SCC) was considered a target. A prescription dose of 41.6 Gy in 8 fractions was delivered to BCC, and 46.8 Gy in 9 fractions to SCC.ResultsFrom 2013 to 2018, a total of 751 NMSC patients (534 BCCs and 217 SCCs) were treated with HDR-BT (518 with IS, 225 with SC, and 8 with IS + SC technique). Thirty patients (4%) partially responded to treatment, and 721 patients (96%) had complete responses. Only 3 patients (0.4%) displayed local recurrences. Grade 1, 2, and 3 acute toxicities were observed in 28.0%, 46.7%, and 1.2% of patients, respectively. Grade 1, 2, and 3 late toxicities were observed in 3.3%, 1.3%, and 0.1% of cases. Cosmetic results were excellent in 79.9%, good in 17.8%, fair in 1.7%, and poor in 0.5% of patients.ConclusionsHDR-BT using SC, IS, or IS + SC is an effective treatment for NMSC with good outcomes and cosmetic results in both BCC and SCC.

Large-area transparent biocomposite films based on nanocellulose and nanochitin via horizontal centrifugal casting

In this study, we introduce the horizontal centrifugal casting (HCC) process that enables centrifugal force-assisted, scalable production of large-area (10 in.) polymer composite films based on nanocellulose (CNF) and nanochitin (ChNF). The HCC employs a cylinder mold with its rotation pivot being in a horizontal posture to harness centrifugal force to help flatten the film being cast, from which polymer composite films with excellent uniformity and flatness can be reliably produced in the size of the lateral surface of the cylinder mold. The combination of centrifugal force and horizontal layout of cylinder mold can allow reliable fabrication of large-area self-standing films from both polymeric solution and/or suspension in a scalable and simple fashion, which is a task not readily achieved in common film-forming techniques, such as solvent casting and vacuum filtration. We demonstrate such reliability and versatility of the HCC process by fabricating typical biocomposite films out of both a solution blend of ChNF/silk fibroin and a colloidal suspension of CNF/nanoclay as well as investigating their processing-structure-property relation as an optically transparent composite film targeting for structural component for flexible green optoelectronics and fire-retardant film, respectively.

The Influence of Surface Mycobiota on Sensory Properties of “Istarski pršut” and “Dalmatinski pršut”

This study aimed to identify surface mould species overgrowing the Croatian protected meat products “Istarski pršut” and “Dalmatinski pršut” and their effect on sensory properties. Dry-cured hams were produced in 2018/2019 and obtained from annual fairs. The predominant surface species found on “Dalmatinski pršut” were Aspergillus chevalieri, Penicillium citrinum and Aspergillus cibarius, whereas those overgrowing “Istarski pršut” were Aspergillus proliferans, P. citrinum and Penicillium salamii. The results show species diversity, higher presence, and greater variety of Aspergillus species in “Dalmatinski pršut” in comparison to “Istarski pršut”, and significant variations in 9 of 20 sensory attributes. Principal component analysis revealed a clear distinction between the two, and a large contribution of P. salamii and Penicillium bialowienzense to one principal component. The texture traits, smoky odour, muscle and subcutaneous fatty tissue colour, and mould species found are valuable for product characterisation. The results also indicate that mould species may be responsible for some sensory traits, such as tenderness, juiciness, and lesser freshness.

Effect of Mold Width on the Flow Field in a Slab Continuous-Casting Mold with High-Temperature Velocity Measurement and Numerical Simulation

In this paper, the effects of the width of the mold on the surface velocity, flow field pattern, turbulent kinetic energy distribution, and surface-level fluctuation in the mold were studied with measurement of the flow velocity near the surface of the mold at high temperature with the rod deflection method and numerical calculation with the standard k-ε model coupled with the discrete-phase model (DPM) model for automobile exposed panel production. Under the conditions of low fixed steel throughput of 2.2 ton/min, a nozzle immersion depth of 140 mm, and an argon gas flow rate of 4 L/min, as the width of the mold increases from 880 mm to 1050 mm and 1300 mm, the flow velocity near the surface of the mold decreases. The flow direction changes from the positive velocity with the mold widths of 880 mm and 1050 mm to the unstable velocity with the mold width of 1300 mm. The calculated results are in good agreement with the measured results. The turbulent kinetic energy near the submerged entry nozzle (SEN) gradually increases, and the risk of slag entrainment increases. Under the conditions of high fixed steel throughput of 3.5 ton/min, the SEN immersion depth of 160 mm, and the argon gas flow rate of 10 L/min, as the width of the mold increases from 1600 mm to 1800 mm and 2000 mm, the velocity near the mold surface decreases. The flow velocity at 1/4 of the surface of the mold is positive with the mold width of 1600 mm, while the velocities are negative with the widths of 1800 mm and 2000 mm. The calculated results are basically consistent with the measured results. The high turbulent kinetic energy area near the nozzle expands to a narrow wall, and the risk of slag entrainment is significantly increased. In both cases of low and high fixed steel throughput, the change rules of the flow field in the mold with the width are basically the same. The argon gas flow rate and the immersion depth of SEN should be adjusted reasonably to optimize the flow field in the mold with different widths under the same fixed steel throughput in the practical production.

A Study on Post-Processing and Machine Simulation of AC Type 5-Axis Machine Tool for Machining of Mold Surface

A Study on Post-Processing and Machine Simulation of AC Type 5-Axis Machine Tool for Machining of Mold Surface

Comparison of the Flow Field in a Slab Continuous Casting Mold between the Thicknesses of 180 mm and 250 mm by High Temperature Quantitative Measurement and Numerical Simulation

In the present work, the flow field in a slab continuous casting mold with thicknesses of 180 and 250 mm are compared using high temperature quantitative measurement and numerical simulation. The results of the numerical simulation are in agreement with those of the high temperature quantitative measurement, which verifies the accuracy and reliability of the numerical simulation. Under the same working conditions, the velocities near the mold surface with the thickness of 180 mm were slightly higher than those of the mold with the thickness of 250 mm. The flow pattern in the 180 mm thick mold maintains DRF more easily than that in 250 mm thick mold. The kinetic energy of the jet dissipates faster in the 250 mm thick mold than in the 180 mm mold. For double-roll flow (DRF), as the argon gas bubbles can be flushed into the deeper region under the influence of strong jets on both sides, the argon bubbles distribute widely in the mold. For single-roll flow (SRF), as the argon bubbles float up quickly after leaving the side holes, the bubble distribution is more concentrated in the width direction, which may cause violent interface fluctuation and slag entrainment. The fluctuation at the steel-slag interface in the mold with 180 mm thickness is greater than that in the mold with 250 mm thickness but less than 5 mm. The increase of mold thickness may lead to a decrease of the symmetry of the flow field in the thickness direction and uniformity of mold powder layer thickness. In summary, the steel throughput should be increased in the 250 mm thick mold compared with that in the 180 mm thick mold.

Tensile properties of Ti–48Al–2Cr–2Nb alloy having similarly oriented lamellae with fine lamellar spacing facilitated by suction casting

Ti–48Al–2Cr–2Nb (at. pct) billet was prepared by suction casting into a cold steel mould, and its microstructures and mechanical properties at room and elevated temperatures were investigated. The billet featured lamellar microstructure with refined colony sizes, fine interlamellar spacing, and lamellar interfaces nearly parallel to the mould surface with a scatter angle within 30°. Benefitting from this microstructure, the billet showed excellent mechanical properties at temperatures up to 850 °C, with yield strength of 629 ± 29 MPa at ambient temperature, 549 ± 14 MPa at 650 °C, 565 ± 17 MPa at 700 °C, 475 ± 6 MPa at 800 °C and 413 ± 9 MPa at 850 °C, comparable to that of the third-generation TiAl alloys like TNM but much superior to that of most reported cast Ti–48Al–2Cr–2Nb alloys. The total fracture elongation at room temperature and 700 °C were (1.8 ± 0.2) % and (15.9 ± 3.5) %, respectively. Although the fracture at 700 °C occurred in a brittle mode, the tensile samples possessed ductile tensile elongation.

Large-scale additive manufacturing of self-heating molds

Large-scale material extrusion additive manufacturing technology is becoming the new mainstream technology for scaled-up composite mold and die applications. This paradigm shift in composite processing technology is primarily driven by out-of-autoclave tooling applications, in which fiber reinforced composite molds with scaled-up sizes and embedded heating elements are attractive. The present research describes the design, manufacturing, and testing of self-heating composite molds fabricated via a large-scale pellet extrusion 3D printing machine with an integrated wire co-extrusion tool. Polycarbonate (PC) composites reinforced with carbon fiber (PC/CF; 20 wt.%) and glass fiber (PC/GF; 20 wt.%) were used to fabricate mold parts. Joule heating thermal test results showed that uniform temperatures (~100 °C) were achieved for both PC/CF and PC/GF mold surfaces, using a custom-made feedback control power supply and infrared thermography. Mechanical characterizations, including tensile and flexural testing were performed on the wire-embedded and un-wired PC/CF and PC/GF base specimens to investigate the impact of the fiber reinforcement as well as the embedded wires. In the direction of extrusion, the ultimate tensile stress of PC/CF was 105 MPa, and that of PC/GF was 73 MPa, while the neat PC value was 64 MPa. Inner-bead voids and interfacial gaps were observed and characterized via optical and scanning electron microscopy. The embedded wires and inner bead impacted the mechanical properties of the composites. However, the stiffness of the wire-embedded mold was still satisfactory, proving that the technology can be used to fabricate additively manufactured out-of-oven/autoclave molds.

Basal Cell Carcinoma Treated with High Dose Rate (HDR) Brachytherapy-Early Evaluation of Clinical and Dermoscopic Patterns during Irradiation.

Simple SummaryBasal cell carcinoma (BCC) is the most frequent malignancy of the Caucasian population. High dose rate (HDR) brachytherapy is a re-emerging treatment method for various skin cancers. Dermoscopy is an acknowledged and widely used diagnostic tool providing the bridge between histopathology and clinical examination. Current literature lacks data reporting on the dermoscopic observation of basal cell carcinomas undergoing brachytherapy. In this article, the authors describe clinical and dermoscopic patterns of basal cell carcinomas from 23 patients treated with HDR brachytherapy, and analyse the evolution of BCC structures.Basal cell carcinoma (BCC) is the most frequent malignancy of the Caucasian population. Dermoscopy is an established diagnostic method providing the bridge between clinical and pathological examination. Surface skin high dose rate (HDR) brachytherapy is an organ sparing treatment method used for non-surgical candidates. This prospective study aimed to observe clinical and dermoscopic features and their evolution in 23 patients with pathologically confirmed BCC that have been treated with HDR brachytherapy. In all cases, custom-made surface moulds were used. HDR brachytherapy was performed with 192Ir, dose 45Gy was delivered to the tumour in nine fractions of 5Gy, three times a week. The evolution of clinical and dermoscopic features was followed up at the beginning of treatment, and on the day of every fraction (t1–t9). Dermoscopic evaluation of neoplastic and non-neoplastic structures was based on current diagnostic criteria according to current literature. Univariate logistic regression showed a decreasing number of clinical and pathological features of basal cell carcinoma with every treatment fraction. The effect was more strongly pronounced for cancer-related dermoscopic structures compared with non-neoplastic features. We used multivariate ordinal logistic regression with random effects to prove that the patients’ age corresponds with the tumour’s response to radiation—which may implicate a better response to treatment among older patients. High dose rate brachytherapy decreases the number of clinical and dermoscopic features typical for basal cell carcinoma. The effect is more pronounced among older patients.

The Influence of Surface Quality on Flow Length and Micro-Mechanical Properties of Polycarbonate.

This study describes the influence of polymer flow length on mechanical properties of tested polymer, specifically polycarbonate. The flow length was examined in a spiral shaped mould. The mould cavity’s surface was machined by several methods, which led to differing roughness of the surface. The cavity was finished by milling, grinding and polishing. In order to thoroughly understand the influence of the mould surface quality on the flow length, varying processing parameters, specifically the pressure, were used. The polymer part was divided into several segments, in which the micro-mechanical properties, such as hardness and indentation modulus were measured. The results of this study provide interesting data concerning the flow length, which was up to 3% longer for rougher surfaces, but shorter in cavities with polished surface. These results are in disagreement with the commonly practiced theory, which states that better surface quality leads to greater flow length. Furthermore, evaluation of the micro-mechanical properties measured along the flow path demonstrated significant variance in researched properties, which increased by 35% (indentation hardness) and 86% by indentation modulus) in latter segments of the spiral in comparison with the gate.