Mold Surface Temperature Research Articles

Modeling spherulitic and fibrillar crystallization kinetics in injection molding: Analysis of process variables and morphological evolution

Injection molding of polypropylene was conducted using a heating device to control mold surface temperature over time. By varying the temperature and heating times, a significant effect on cavity pressures, temperatures, and morphology distribution in the resulting samples was obtained.The University of Salerno's UNISA code, a simulation model for injection molding, was used to simulate the experimental conditions. This code incorporates a crystallization kinetics model that accounts for the competing formation of spherulites and fibrils from the same amorphous material, considering the effects of temperature, pressure, and flow evolution during different stages of the process.The simulation results showed good agreement with experimental data for temperature evolutions within the mold and pressure variations at critical points during the filling, packing, and cooling stages. Additionally, the simulation consistently predicted the formation of a fibrillar layer near the mold wall. Overall, a comprehensive framework for understanding and simulating the injection molding process is provided, with relevant implications for the optimization of manufacturing conditions and improving part quality.

Global Sensitivity Analysis of Factors Influencing the Surface Temperature of Mold during Autoclave Processing.

During the process of forming carbon fiber reinforced plastics (CFRP) in an autoclave, deeply understanding the global sensitivity of factors influencing mold surface temperature is of paramount importance for optimizing large frame-type mold thermally and enhancing curing quality. In this study, the convective heat transfer coefficient (CHTC), the thickness of composite laminates (TCL), the thickness of mold facesheet (TMF), the mold material type (MMT), and the thickness of the auxiliary materials layer (TAL) have been quantitatively assessed for the effects on the mold surface temperature. This assessment was conducted by building the thermal-chemical curing model of composite laminates and utilizing the Sobol global sensitivity analysis (GSA) method. Additionally, the interactions among these factors were investigated to gain a comprehensive understanding of their combined effects. The results show that the sensitivity order of these factors is as follows: CHTC > MMT > TMF > TCL > TAL. Moreover, CHTC, MMT, and TMF are the main factors influencing mold surface temperature, as the sum of their first-order sensitivity indices accounts for over 97.3%. The influence of a single factor is more significant than that of the interaction between factors since the sum of the first-order sensitivity indices of the factors is more than 78.1%. This study will support the development of science-based guidelines for the thermal design of molds and associated heating equipment design.

Study on the influence of injection molding parameters on the warpage using simulation and Taguchi method

Injection moulding (IM) is a processing technique produced from polymeric products. Warpage defect (WD) is the defect that generally occurs during the IM process due to the inappropriate processing parameters of the melt temperature, mould surface temperature, packing pressure, injection pressure, and packing pressure time. This paper investigates the IM parameters that influence product warpage by combining the simulation, analysis of variance, signal-to-noise analysis, and Taguchi method. The simulation process was performed by Moldflow software. The product material is high-density polyethylene. The WD has been predicted and optimized to enhance product quality. Melt temperature and packing pressure time are the factors that acrimoniously influenced the warpage of the product. The results show that the packing pressure time and melt temperature have the highest effects on the WD by the contributions of 48.94% and 37.48%, respectively. The optimal IM parameters are scanned again with the WD abated at about 1.2%. The mathematical formula has been constructed to predict the WD with the reflection of acceptable values of 86.29%. The research hopes that the results have been applied to designing and fabricating the plastic product in the near future.

Polymer/mold interfacial heat transfer during injection molding

AbstractAn experimental injection molding setup was designed and fabricated. The purpose of the setup is to cast polymer components and estimate the polymer/mold interfacial heat flux transients during injection molding. The mold plate is instrumented with K‐type thermocouples to record its thermal history continuously during the cyclic process. Experiments were performed at a melt injection temperature of 280°C. Velocity and shear rate profiles were determined to assess the flow behavior of the melt. The spatiotemporal heat flux transients at the interface and the mold surface temperature were estimated using measured temperature data inside the mold as input to an inverse heat conduction problem. The estimated boundary heat flux transients were used to numerically simulate the polymer melt's cooling behavior. From the estimated heat flux and surface temperatures, heat transfer coefficients (HTC) were determined. The peak value of the HTC was 5775 W/m2K and occurred at a mold surface temperature of 35.7°C and polymer surface temperature of 47.4°C. The evolution of the air gap at the interface was quantified using an exponential fit. The estimated air gap width corresponding to peak HTC was about 4 μm and increased to about 100 μm towards the end of the solidification. While the peak heat flux is associated with the start of the formation of polymer skin on the mold surface, the peak HTC corresponds to the onset of nucleation of the air gap or a nonconforming contact.Highlights An experimental setup to study heat transfer during injection molding. Spatiotemporal heat flux transients (q) were estimated during injection molding. Polymer temperatures were simulated using q, and HTC was determined. The peak HTC indicated the onset of nucleation of an air gap. Evolution of air gap at the interface was modeled using an exponential fit.

Effect of mold temperature on properties of hybrid biocomposites from semicrystalline polymers and agro-industrial by-products

The surface temperature of the mold is a critical processing parameter that significantly influences the quality of composites during injection molding. Therefore, this study aimed to investigate the effect of mold surface temperature on the properties of hybrid biocomposite materials prepared by incorporating polypropylene-PP with agro-industrial by-products such as rice husks-RH and fique powder-FP using co-rotating twin-screw extrusion and injection molding. While this article focuses on PP as the polymeric matrix, the methodology employed in this study can also be applied to investigate the effect of mold surface temperature on the properties of other polymers used in the production of hybrid composites via injection molding as biobased or biodegradable plastics. The mechanical characterization reveals that the utilization of higher mold temperatures and the hybridization of RH and FP result in an increase in the elastic modulus of up to 30% compared to PP. Also, thermal, viscoelastic, morphological, and HDT characterization revealed that higher surface mold temperature led to changes in PP crystallinity, and a better hybrid biocomposites performance. This study highlights the potential of mold surface temperature controlling and agro-industrial by-products hybridization for the design and production of higher quality and sustainable products using injection molding.

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.

The potential of RHCM technology in injection molding using a simple convention heating and cooling system

In conventional injection molding, low mold temperatures are used; however, the thermal conditions, which vary during the processing, affect the properties of the injection molded parts and the injection molding process parameters. Due to the rapid cooling of the molten polymer against the mold wall, the flow resistance of the molten polymer increases, and the hydraulic injection pressure is directly affected by this. The rapid cooling of the plastic parts affects the quality of the parts, which can result in surface defects.Using the rapid heat cycle molding (RHCM) approach, a simple convection heating and cooling system was added to a conventional injection molding process to study the potential of RHCM technology. We assessed the influence of the mold temperature on the part's morphological features (namely, the frozen layer) and mechanical properties (namely, the Young's modulus), as well as the hydraulic injection pressure.Using RHCM to heat the molding surface up to 100 °C was found to entirely prevent the formation of a frozen layer, with an expected positive effect on the previously mentioned defects. Note that while the decrease of the frozen layer could have been expected to reduce Young's modulus, this did not happen, which is a very positive outcome related to the specific orientation at which the frozen layer is formed and its morphology. The higher the mold surface temperature, the lower the hydraulic injection pressure, which means less strict structural requirements for the mold. These results highlight the potential of RHCM technology in injection molding, namely as a strategy to mitigate or solve molding defects.

Interpretation of the effect of transient process data on part quality of injection molding based on explainable artificial intelligence

This paper proposes an interpretation methodology for the effect of transient process data on quality of injection molded parts. The transient process data measured in the actual processing space have been regarded as the most relevant information to manufacturing processes and product quality. However, its interpretation to pinpoint which feature in the data would affect part quality has traditionally relied on knowledge and understanding of the manufacturing process. The main objective of this method is to reduce the dependency of the transient process data analysis on process knowledge and understanding by using explainable artificial intelligence (XAI). The contribution of the ‘section-wise' features in the transient process data to the quality prediction of machine learning (ML) models was investigated for the first time. The interpretation results of the effect of cavity pressure and mold surface temperature on four different quality factors represented reasonable explanations of the characteristics of the polymer materials, product geometry, and molding process. Due to the intermediate relationship of the transient process data with the user-specified process parameters and the resulting quality variables, the interpretation results can be further utilized to optimize the process and provide the optimal transient process data profile for best part quality.

Analysis of ducted fan warpage based on the response surface methodology and a genetic algorithm

AbstractDucted fans with thin‐shelled tubular structures are typically used in unmanned aerial vehicles. However, due to their thinness and heterogeneity, the ducts are prone to warpage deformation, which can adversely affect the aerodynamic characteristics of the fans. In this study, Moldflow software was used to analyze and reduce the warpage deformation of a duct made of 15 wt% glass fiber‐reinforced acrylonitrile butadiene styrene. First, a Taguchi experiment was performed to determine the main factors affecting the warpage: the mold surface temperature, melt temperature, injection pressure, and holding pressure. Subsequently, the response surface methodology (RSM) was employed to define a regression equation and response surface relating the dependent and independent variables, and a genetic algorithm (GA) was used for optimization. The maximum warpage was successfully reduced from 0.2217 to 0.0465 and 0.0578 mm through the RSM and GA analyzes, respectively, and the simulated results were validated by data collected using a COMET L3D system. Finally, the influence of the warpage of the ducted rear deflector on the aerodynamic performance was investigated by performing computational fluid dynamics analysis. The results indicated that curving the rear deflector has a beneficial effect on aerodynamic performance, as it increases velocity, but it also reduces the impact of the torque balance. This paper describes an innovative application method using a specific combination of analysis tools to address the problem of optimizing the design, modeling, and performance of ducted fans. This work can help predict manufacturing results and aerodynamic effectiveness at an early stage.

A Numerical Study on Increasing the Cavity Temperature in Injection Molds

In the injection molding process, the filling process will be easier and, in most cases, the surface quality will be significantly improved if the mold surface temperature is high. However, as the temperature of the mold plates rises, the cooling process takes longer, the injection molding cycle takes longer, and the cost of production rises. The most important thing is to keep the mold temperature under control, which means heating the mold surface to the required temperature while keeping the injection cycle time to a minimum. In this research, hot air was used as the heat source for raising the cavity temperature to over 200 °C with a heating time of 20 s. At the end of heating process, the temperature was collected at 10 points for comparison. In addition, the temperature distribution was also discussed.

Internal Gas-Assisted Mold Temperature Control for Improving the Filling Ability of Polyamide 6 + 30% Glass Fiber in the Micro-Injection Molding Process.

In micro-injection molding, the plastic filling in the cavity is limited by the frozen layer due to the rapid cooling of the hot melt when it comes into contact with the surface of the cavity at a lower temperature. This problem is more serious with composite materials, which have a higher viscosity than pure materials. Moreover, this issue is also more serious with composite materials that have a higher weight percentage of glass filer. In this article, a pre-heating step with the internal gas heating method was used to heat the cavity surface to a high temperature before the filling step to reduce the frozen layer and to improve the filling ability of the composite material (polyamide 6 + 30% glass fiber) in the micro-injection molding process. To heat the cavity surface, an internal gas-assisted mold temperature control (In-GMTC) system was used with a pulsed cooling system. We assessed different mold insert thicknesses (t) and gaps between the gas gate and the heating surface (G) to achieve rapid mold surface temperature control. The heating process was observed using an infrared camera, and the temperature distribution and the heating rate were analyzed. Thereafter, along with the local temperature control, the In-GMTC was used for the micro-injection molding cycle. The results show that, with a gas temperature of 300 °C and a gas gap of 3.5 mm, the heating rate reached 8.6 °C/s. The In-GMTC was also applied to the micro-injection molding process with a part thickness of 0.2 mm. It was shown that the melt flow length had to reach 24 mm to fill the cavity completely. The results show that the filling ability of the composite material increased from 65.4% to 100% with local heating at the melt inlet area when the gas temperature rose from 200 to 400 °C with a 20 s heating cycle.

Dynamic Mold Surface Temperature Control Using Induction and Heater Heating Combined with Coolant Cooling

Abstract In this study, both electrical heater heating and electromagnetic induction heating combined with coolant cooling are developed to achieve a dynamic mold surface temperature control. Simulation tool was also developed by integration of both thermal and electromagnetic analysis modules of ANSYS. The capability and accuracy of simulations on the heater heating and induction heating were verified with experiments. To evaluate the feasibility and efficiency of heater heating and induction heating on the mold surface temperature control, a mold plate, roughly about an inset size of cellular phone housing, installed with five heaters and designed with four cooling channel with coolant running through, was utilized for the demo experiments varying mold surface temperature between 110 °C and 200 °C. During induction heating/cooling case, it takes 4 s to increase mold surface temperature from 110 to 200 °C and it takes another 21 s for mold surface to cool down to 110 °C. The mold plate surface temperature can be raised at about 22.5 °C/s and cooled down at 4.3 °C/s within the mentioned temperature range. Mold plate temperature distribution exhibits good uniformity as well in all stage of heating/cooling process. For heaters heating, it takes 37 s to increase mold surface temperature from 110 to 200 °C and it takes another 30 s for mold surface to cool down to 110 °C. The temperature rising rate is only about 2.4 ° C/s. Induction heating is more efficient in mold surface temperatures control than electrical heating and it does eliminate the weld line mark when applied to a tensile test mold with double gate design prior to melt injection.

Numerical Simulation and Process Optimization of a 3D Thin-Walled Polymeric Part Using Injection Compression Molding

Abstract Injection compression molding (ICM) is a hybrid injection molding process for manufacturing polymer products with high precision and surface accuracy. In this study, a 3D flow simulation was employed for ICM and injection molding (IM) processes. Initially, the process parameters of IM and ICM were discussed based on the numerical simulations. The IM and ICM processes were compared via numerical simulation by using CAE tools of Moldflow software. The effect of process parameters of mold surface temperature, melting temperature, compression force and injection time on clamping force and pressure at the injection location of molded 3D BJ998MO Polypropylene (MFI 100) part was investigated by Taguchi analysis. In conclusion, it was found that the ICM has a relatively lower filling pressure than ICM, which results in reduced clamping force for producing a 3D thin-walled polymeric part.

An experimental investigation of the cooling and heating performance of a gravity die casting mold with conformal cooling channels

• Conformal cooling was applied successfully in gravity die casting mold. • Cooling efficiency was increased with cooling channels around the pusher pin regions. • Cycle time was reduced by 28% with conformal cooling channel in gravity die casting. • The average grain size of casted parts was reduced by 13.5%. In the gravity die casting process, cooling directly affects the unit cost and microstructure quality of casting products. In the conventional manufacturing methods, cooling channels in gravity casting molds are usually produced linearly in circular profiles. When cooling is not conformal, molding defects such as hot spots and distortions form in the products. This study investigated the effects of cooling channels on the casting steps and final properties of the products in standard and conformal cooling gravity die casting molds. Numerical analysis results were compared with the experimental data and then were verified. The pressure losses in cooling channels, the times for molds to reach the required temperature and the cycle times were all measured. The pressure losses in standard and conformal cooling channels were measured at 5250 Pa and 12100 Pa, respectively. In addition, a more homogeneous mold surface temperature distribution was achieved in the conformal cooling mold, as well as a 28% shorter cycle time. The average particle size of the parts cast with conformal molds was 13.5% smaller than those cast with standard molds. Finally, the mechanical properties of the parts cast with conformal cooling channel molds were found to be better than those cast with standard channel molds.

The Feasibility of an Internal Gas-Assisted Heating Method for Improving the Melt Filling Ability of Polyamide 6 Thermoplastic Composites in a Thin Wall Injection Molding Process.

In thin wall injection molding, the filling of plastic material into the cavity will be restricted by the frozen layer due to the quick cooling of the hot melt when it contacts with the lower temperature surface of the cavity. This problem is heightened in composite material, which has a higher viscosity than pure plastic. In this paper, to reduce the frozen layer as well as improve the filling ability of polyamide 6 reinforced with 30 wt.% glass fiber (PA6/GF30%) in the thin wall injection molding process, a preheating step with the internal gas heating method was applied to heat the cavity surface to a high temperature, and then, the filling step was commenced. In this study, the filling ability of PA6/GF30% was studied with a melt flow thickness varying from 0.1 to 0.5 mm. To improve the filling ability, the mold temperature control technique was applied. In this study, an internal gas-assisted mold temperature control (In-GMTC) using different levels of mold insert thickness and gas temperatures to achieve rapid mold surface temperature control was established. The heating process was observed using an infrared camera and estimated by the temperature distribution and the heating rate. Then, the In-GMTC was employed to produce a thin product by an injection molding process with the In-GMTC system. The simulation results show that with agas temperature of 300 °C, the cavity surface could be heated under a heating rate that varied from 23.5 to 24.5 °C/s in the first 2 s. Then, the heating rate decreased. After the heating process was completed, the cavity temperature was varied from 83.8 to about 164.5 °C. In-GMTC was also used for the injection molding process with a part thickness that varied from 0.1 to 0.5 mm. The results show that with In-GMTC, the filling ability of composite material clearly increased from 2.8 to 18.6 mm with a flow thickness of 0.1 mm.

Dynamic conformal cooling improves injection molding

To achieve a certain visual quality or acceptable surface appearance in injection-molded components, a higher mold surface temperature is needed. In order to achieve this, injection molds can be dynamically tempered by integrating an active heating and cooling process inside the mold halves. This heating and cooling of the mold halves becomes more efficient when the temperature change occurs closer to the mold surface. Complex channels that carry cold or hot liquids can be manufactured close to the mold surface by using the layer by layer principle of additive manufacturing. Laser powder bed fusion (L-PBF), as an additive manufacturing process, has special advantages; in particular, so-called hybrid tools can be manufactured. For example, complex tool inserts with conformal cooling channels can be additively built on simple, machined baseplates. This paper outlines the thermal simulation carried out to optimize the injection molding process by use of dynamic conformal cooling. Based on the results of this simulation, a mold with conformal cooling channels was designed and additively manufactured in maraging steel (1.2709) and then experimentally tested.

An effect of mold surface temperature on final product properties in the injection molding of high-density polyethylene materials

Mold surface temperature is one of the most critical process parameters in injection molding. This study aimed to determine the effect of mold surface temperature on plastic parts in injection molding of high-density polyethylene materials. Other process parameters were kept constant, and samples were prepared by changing mold surface temperatures by the injection molding method. The samples’ mechanical tests, thermal tests, and gloss measurements by a gloss meter were performed, and the amount of warpage and collapses was measured by a video measuring system. Microstructures were examined under a scanning electron microscope. It was observed that the mold surface temperature increased the crystallization rate, tensile and bending strength of the materials, decreased the thicknesses of the crystal lamella and impact strength, and had an effect on the melting temperature of the crystal. The microstructure investigations demonstrated that as the mold surface temperature increased, the cavity formation in the structure increased, and fibrillation decreased due to expansion and cooling time. It was determined that the amount of collapse and warpage was affected by the mold surface temperature and that the increase in the mold surface temperature decreased the amount of collapse and increased the amount of warpage and surface gloss.

Design and Material Selection of Screw Feeder of Injection Molding Machine

The efficiency of the ‘Injection molding Machine’ lies in the proper designing of screw feeder mechanism. The screw feeding mechanism needs to be setup differently for different materials, molds etc. The proper design includes the work from selecting the appropriate materials, designing for the optimum design, analysis of the designed parts at different flow rates, speed and temperatures. There are various parameters that govern the efficiency of the ’Injection molding Machine’. These parameters include ‘Filling Pressure’, ‘Mold Surface Temperature’, ‘Raw Material Melting Temperature’, ‘Filling Time’ etc.

CAE Analysis for Disposable Mouth Mirror Based on Autodesk Moldflow Plastic Insight

This study is carried out to focus on computer aided engineering analysis on dental toolkit for disposable mouth mirror by using Autodesk Moldflow Insight (AMI) software. Disposable mouth mirror designs contain with a very small and precise features for it handles and fix angle between shank and working area (mirror). A 3D cad model of disposable mouth mirror has been construct and imported to the simulation software. The part has been analysed with thermoplastic material of Polypropylene (PP) as a part material for its light weight and durability. The simulation and analysis by moulding software package is used in order to determine the best range of operating parameter for injection moulding process in furtherance to get the low manufacturing defect. The process parameters that has been selected includes mould surface temperature, melt temperature, flow rate and cooling time during the injection moulding process. At the end, the best range of operating parameters has been proposed and simulates to study the product behaviour.

Characterization of a direct metal printed injection mold with different conformal cooling channels

According to the practical experiences in the injection molding, the knowledge about conformal cooling channel (CCC) is an essential factor that affects productivity and quality of the molded part greatly. In general, the CCC provides a reduction in the cooling time in series production. However, the distance between cooling channel edges of the circular conformal cooling channel (CCCC) and mold cavity edge is not constant. The profiled conformal cooling channel (PCCC) has flat surface of the cooling channel facing the profile of the cavity fully. The distance between cooling channel edges of the PCCC and mold cavity edge is constant. In this study, two maraging steel injection molding tools with two different CCC were designed and fabricated by the direct metal printing technology. The difference between injection mold with PCCC and CCCC on the cooling time of the molded wax pattern, part temperature difference, mold surface temperature difference, and part warpage were numerically investigated using Moldex3D simulation software. It was found that the PCCC seems to be a good candidate in the CCC design and provides a better alternative in the conventional cooling channels. The PCCC reduced the cooling time about 33.33% compared with CCCC under the coolant water temperature of 25 °C. The temperature of 26 °C is the optimal value for the coolant water based on the dimensional accuracy of the wax pattern and energy consumption of the cooling system.