The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
The plastic industry uses advance injection molding technologies to enhance part performance and surface appearance. Rapid heating cooling molding (RHCM) technology has been shown to enhance surface appearance and achieve high mold surface replication. In this article, we examined the physical properties of Polycarbonate and Polycarbonate/ABS to compare conventional injection molding (CIM) and RHCM. The comprehensive study investigated stress-strain properties, weld-line strength, impact performance, and flow length. The results demonstrated that RHCM did not affect the bulk material physical properties. In some cases, the study showed an increase in physical properties for weld-line strength and flow length.
Injection molding parts became more and more complex and especially critical components are subjected to high safety requirements. In this paper a fully functioning injection molding test specimen with integrated condition monitoring was developed by using all-inkjet printed strain gauges and back injecting them. For the printing of electrically conductive traces a commercial available Epson printer and silver nanoparticle dispersion was used. This enables the fabrication of sensor systems without the need of a photo mask. Furthermore the applicability for monitoring injection molding parts with low-cost sensor systems was investigated. Therefore several test specimens with integrated strain gauges were fabricated and tested with a tensile testing machine. With the integrated strain gauge the relative change in resistivity was measured and the resulting strain was then compared to the results of the tensile testing. In this context the gauge factor of the printed conductive traces were characterized.
Modern injection molding machines with state-of-the-art control technology enable plastics-processing companies to operate processes resulting in high part quality and low reject rates. However, external influences such as fluctuations in the material properties may cause the production of bad parts, which is often detected with a time delay, causing high costs. Based on this, the present paper describes a procedure to gain valuable information from the continuously generated process data. It shows how methods for anomaly detection and localization of their underlying root causes can help machine operators identify critical process states more quickly. This in turn leads to lower reject rates and machine down times and thus an enhanced overall process control.
Most would agree that the mold is the heart of the molding process. From those that make them to those who use them, we all want them to last for as long as they were designed. A lot of work goes into striving toward that goal: good design, proper metallurgy selection, configuration, coatings, etc. With all that having been taken into account, why clean the mold with traditional methods that may wear out the parting line and shut-offs? This paper will demonstrate that cleaning tooling with dry ice is a safe, effective and non-abrasive way to clean common injection molds. It will provide molders, not only a way to extend the asset life of the tool, but also to improve quality, increase productivity, lower costs and improve environmental quality. This paper will focus on the first benefit of maintaining the expected life of our molds. Today, high-dollar and often complex molds, are run and maintained in varying degrees of skilled molding shops and tool rooms. Some of the cleaning methods still be utilized can contribute to tool wear.
This paper presents an investigation of the effect of mixing natural Jute fibre and Maleic Anhydrite compatibilizer with recycled Polypropylene (PP) and Polyethylene terephthalate (PET) blends. Recycled plastic has a significant contribution to reduce the environmental issues and encourage the economic benefit. PP and PET polymers are commonly used in the industrial fields, however, they are immiscible and it is difficult to be blended. Two different PP & PET (65/35 and 78/22 v/v %) samples have been blended with 0.5% wt (2 g) Jute fibre and 5% wt (20 g) Maleic anhydride (PP-g-MAH). The mechanical mixing has been done by using twin-screw extruder to get pellets of PP/PET/jute/Maleic Anhydrite, which were used to make test samples with injection moulding machine. The comparative result shows that blend of PP/PET with and without any addition of Maleic anhydride and Jute fibre has enhanced tensile and flexural properties significantly.
With induction heat/cool mold technology it is possible to reach mold temperatures effective for low and high melting polymers with precise temperature control during the injection stage of a molding cycle. This results in enhanced flow behavior of the resins enabling, among others, thin wall molding, enhanced surface replication and generally improved part performance. There is a need to better quantify these effects for various resins. The High Definition Plastics database offers central storage for these quantified benefits according a standardized method and allows easy material selection for a specific design or purpose.
This paper investigates the fabrication of micro-molded features using Moldflow analysis to optimize processing parameters. Melt temperature, mold temperatures, injection velocity, and packing pressure were all examined to help understand the process of microinjection molding. Micro pillar type features with different cross sectional shapes, diameter, and height were investigated using Moldflow® analysis to optimize filling. Critical processing parameters were identified for common thermoplastic polymers such as Polystyrene (PS) and Thermoplastic Polyurethane (TPU).
As per Vikram Bhargava's request I am submitting this abstract as an Invited Speaker. Thanks.A robust process produces parts that are consistent in quality cavity to cavity, shot to shot and run to run despite the natural variations such as that of the machine, material, environment and the operator. A capable process produces parts that are consistent within the required quality requirements. Both these are a requirement for a successful molding operation. To reach to this success, the part design, the mold design, the mold build, the machine selection and the molding process need to be considered all at one time right at the start of the project. Unfortunately, in most cases, a designer designs the part, throws it over the wall to the mold maker who makes the mold and throws it over the wall to the molder who then ends up with a substandard process with several quality issues. The talk will focus on how and why to apply concurrent engineering principles for the success of a project.
What you didn’t think was possible with Automatic Water Flow Control. Previous methods of water flow control have proven themselves beneficial to the molding process but come with a series of headaches between setup and monitoring. Automatic water flow control is the next wave of technology in the molding industry. Imagine being able to reap the benefits of water flow control without all the hassle.The key advantage of automatic water flow control over a manually adjustable one is that it permits continuous electronic monitoring and automatic adjustment of proportional control valves to meet preset flow and temperature values. All data can be logged. Already proven in service many times over, the WITTMANN fine regulating valve of the 301 Series performs flow regulation. Generously dimensioned channels in the casing blocks guarantee the lowest possible pressure loss and high flow rates.The net benefit is being able to easily balance temperature and flow through complex tooling pathways, bubblers, thermal pins, conformal cooling and of the like. This leads to a much higher level of process repeatability because an automatic regulator reacts much quicker and with a higher accuracy than most temperature controllers, as well as provides zone control of the tool. A technician can balance the tool to avoid shrinkage or warpage in trouble areas of the tooling, and even balance fill rates. Another benefit is that once you’ve qualified the mold with certain temperature and flow settings, those setting can be saved, allowing an easier setup of the mold. Likewise all of the processing data on the machine for zone temperatures and flows can be tracked. Working with a multi-cavity tool? Great because automatic flow control ensures uniform cavity filling due a modifiable heat profile throughout the mold and it’s cavities. Lastly, if there is degradation in flow due to a blockage or restriction, the system will identify this, its location, and indicate to the operator that there is a problem. This allows a technician to proactively clean a cooling channel before a failure occurs.
The processability of injection molding ultra-high molecular weight polyethylene (UHMWPE) was improved by introducing supercritical nitrogen (scN2) or supercritical carbon dioxide (scCO2) into the polymer melt, which decreased its viscosity and injection pressure while reducing the risk of degradation. When using the special full-shot option of microcellular injection molding (MIM), it was found that the required injection pressure decreased by up to 30% and 35% when scCO2 and scN2 were used, respectively. The mechanical properties in terms of tensile strength, Young’s modulus, and elongation-at-break of the supercritical fluid (SCF)-loaded samples were examined. The rheological properties of regular and SCF-loaded samples were analyzed using parallel-plate rheometry. The results showed that the use of scN2 and scCO2 with UHMWPE and MIM retained the high molecular weight, and thus the mechanical properties of the polymer, while regular injection molding led to signs of degradation.
In this paper, an ultrasound-aided ejection system was designed and tested for various polymers and mold topographies. The use of ultrasound vibration aims at decreasing the ejection friction by reducing its adhesion component, which is controlled by the real contact area developed in the filling phase of the injection molding process. The experiments indicate that the ultrasound vibration reduces the ejection friction up to a maximum of 16%. The effect depends on the polymer used and it increases for rougher mold surface. Moreover, the dependence of ejection friction on mold surface roughness, melt viscosity and elastic modulus at ejection was modeled using the experimental data.
In this study, mold filling simulation crystallization data were compared with experimental data collected with a fast scanning chip calorimeter. This new technique gives the opportunity to collect data at higher cooling rates, which mimic the injection molding process. Experimental data showed that the crystallization temperature depends on the cooling rate, which is neglected in previous models implemented in the simulation software. It is suggested to modify the simulation software crystallization data in order to account for more realistic prediction of the crystallization process and, consequently, microstructure formation affecting properties.
Thermoplastic prepregs that are also known as organo sheets are processed in presses and formed to half shells. Larger components can be produced by joining the half shells, which results in hollow bodies. However, current manufacturing technologies allow only cap profile shaped joints, which cause fiber deflections in the joint plane. This paper shows that overlapping infrared welds in organo sheets enable weld strengths close to the interlaminar shear strengths of the unwelded materials and thus a fiber utilization across the joint plane. By using high welding pressures, a matrix depletion and a change of the fiber alignment in the weld plane may occur which causes low weld strengths. Therefore, criteria for the successful welding were defined various possibilities to the optimization of the weld strengths were investigated.
A newly developed material known as Stylight has been created for design flexibility and lightweighting solutions. Stylight incorporates carbon and glass fibers in an SAN (amorphous polymer) matrix. The SAN matrix allows for a smoother "Class A" finish than traditional thermoformable composite sheets that are normally used hidden structural applications. The glass and carbon fiber also help provide a rigid and tough backbone for structural applications as well. Stylight also provides design flexibility and is able to be painted or covered in decorative film or used with carbon weave pattern.
Beside the economical production of bipolar and heat exchanger plates made from graphite composites, the stack assembly is of great importance for the further technological development of fuel cell, redox-flow battery and heat exchanger systems. In order to choose a suitable welding method, to evaluate the weldability of the composites and to produce a secure stack assembly, a comprehensive understanding of the welding behavior of the materials is required.This work focuses on the welding of graphite composites using the infrared welding method. To form a material-locking joint during the welding process, a defined melting of the material in the joining area is decisive. Due to the thermal properties of highly filled graphite composites, the welding process differs fundamentally from conventional welding of unfilled or low-filled thermoplastics.To perform a scientific examination of the material heating depending on the heating source, a surface and a contour-following infrared radiator were used. Independent of the radiator type, no high-quality joining connection could be achieved. Due to the high thermal conductivity and the low heat capacity of the graphite compounds, the joining area does not have a sufficiently high temperature after infrared heating. Furthermore, it is not possible to apply a sufficiently high joining force, as deep material heating takes place. As a result, the formation of a material-locking joint is significantly impaired with an increasing graphite content.
This research focuses on the characterization of bioplastics joined using ultrasonic welding and modeling of temperature distributions and interfacial healing. Polylactic acid (PLA), which is typically derived from starch-rich crops such as corn, was studied. While the measurement of activation energy for interfacial healing at weld interfaces of PLA films has been reported, here, this information is used to predict the weld strength of rigid PLA samples welded by ultrasonics. A characterization of the mechanical properties was completed with a tensile test to determine the effects of amplitude, weld velocity and collapse distance on weld strength. From previous interfacial healing activation energy measurements based on an impulse welding method, it was also possible to predict weld strength. It was found that the most influential parameters were weld time, collapse distance and weld velocity. In general, the model predicted weld strength reasonably well with r2 values between 0.77 and 0.78.
Friction Riveting is an innovative and promising joining technology, which can potentially fulfill the industry requirements for sustainable and efficient systems. The objective of this work is to prove the feasibility of Direct-FricRiveting by inserting a metallic rivet through metal-composite overlapped plates and subsequent anchoring in the composite part, which is a challenging configuration with limited knowledge available. The case-study joint configuration used in this work comprised a Ti6Al4V rivet, which joined an overlapped AA2024-T3 upper plate with a 30% short-carbon-fiber-reinforced poly-ether-ether-ketone lower plate, material combination of high interest for the aircraft industry. Evaluation of joint formation, temperature development, microstructural and physicochemical changes in the composite, and mechanical properties were carried out for joints produced under low and high energy input. The feasibility was proved, showing satisfactory mechanical performance under lap shear testing (up to 7 ± 1 kN). Changes of polymer crystallinity and thermo-mechanical decomposition in the composite were shown not to affect the joint mechanical performance and failure behavior, while the plastic deformation at the rivet tip played the major hole. The knowledge gathered in this preliminary work will be further applied to optimize the process, contributing to the development of the Friction Riveting technology and improvement of its industrial applicability.
Ultrasonic welding is an efficient technique for rivetless assembly of thermoplastic composites. To further improve this process, it is necessary to develop numerical simulations. A phenomenon often misevaluated but crucial for accurate process simulations is hammering. It is the loss of contact between sonotrode and upper adherend during the vibration phase. The goal of this paper is twofold: present an experimental procedure to measure the displacement of the sonotrode and upper adherend during welding, and discuss two strategies to quantify amplitude transmission to the upper adherend. This will lead to improvement of predictive models for ultrasonic welding and closer agreement with experimental data.
Laser transmission welding is a complicated process with the coupling effect among the unsteady and uneven temperature field, mechanical force, stress and strain and plastic forming flow. The theory based on the ideal contact surface has not satisfied the requirement of practical production. In this paper, the mathematical model of surface roughness profile was built based on Weierstrass-Mandelbrot (W-M) fractal function, the contour welding process for polycarbonate (PC) was simulated with the idea taking real 3-D topography of contact area into account and the effect of laser scan power on the surface topography with different surface roughness was discussed, a combination of a rotary Gaussian volumetric heat source with a Gaussian distribution of surface heat source was proposed. Finally, finite element simulated results agree well with the experiments in contour welding with PC. The experimental study indicates that the laser absorption rate, the welding temperature and the variation of temperature gradients of rough surface are lower than the smooth one.
According to the theory of laser transmission welding (LTW), a 3D transient finite element temperature field and fluid field coupling model based on volumetric heat source and melting and solidification model were built. The moving volumetric heat source of laser transmission welding and boundary conditions were implemented by programming user-define function file written by C language. The temperature filed and fluid field were obtained considering the influence of clamping force. Then distributions of temperature and fluid in heat affected zone were analyzed. The results show that the heat affected zone of opaque part is bigger than that of transparent part. The node of peak temperature is under the weld bead and lags behind the center of laser beam. In the molten pool, the higher the temperature is, the faster the fluid flows. In the Y-Z and X-Z plane, fluid flows to the solid liquid interface and forms two vortexes. Temperature field and velocity field simulation will help to guide and study on laser transmission welding process.
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