Injection Moulding Conditions Research Articles

Optimization of Injection Molding Conditions for Reducing Deformation of Plastic Console Trays for Automobiles: Application of the Taguchi Method

Optimization of Injection Molding Conditions for Reducing Deformation of Plastic Console Trays for Automobiles: Application of the Taguchi Method

Monitoring and modelling the deformation of an aluminium prototype mould insert under different injection moulding and clamping conditions

The conventional material of prototype injection moulds is aluminium. Well-established techniques are available on the applicability of such moulds, yet their operational state is not analysed comprehensively. State monitoring has huge benefits because the mould can be protected from excessive loads and deformations and product quality can be monitored in real time. In this paper, we measured the operational strains, cavity pressure and temperature distribution of prototype injection moulds with the traditional state monitoring method, and analysed the combined effect of holding pressure and clamping force on the operational deformations and cavity pressures. Increasing the clamping force and the holding pressure results in higher operational strains and cavity pressures. The precision of core shift analysis was tested if it can predict operational deformations of aluminium injection moulds. Core shift analysis could accurately predict the maximal deformation but it is inaccurate regarding the time when it occurs. A novel modelling method was also introduced where pressure and temperature results of the injection moulding simulation can be imported into finite element (FE) mechanical simulations. This way, mould deformations can be modelled in mechanical FE simulation environment. The measured operational deformations were compared both with core shift analysis results and with the coupled IM-FE simulation results. Core shift simulation can predict maximal deformations with adequate precision but it does not consider thermal expansion effects properly. In order to improve the accuracy of the simulations, a coupled IM-FE method is necessary, where excellent agreement can be found between the measurements and the calculations. The new, combined modelling technique can improve the accuracy of mould deformation modelling because additional mould material models become available in a professional finite element software. It can be especially useful in the modelling of polymeric mould inserts where stiffness is heavily temperature-dependent and the material creeps.

A Study of Fibre Attrition in the Processing of Long Fibre Reinforced Thermoplastics

Abstract A study has been carried out which demonstrates a technique for measuring long fibre lengths. This technique has been used successfully to discuss subtle differences in the fibre length distributions arising in a range of long fibre reinforced thermoplastics. These new materials were processed using a wide range of injection moulding conditions, including such variables as the injection speeds and the preplasticising screw back pressures. This work proposes mechanisms of fibre attrition in the injection moulding process and makes recommendations for the optimisation of fibre lengths in moulded articles. It is shown that alternative polymer matrices in the long glass fibre attrition. It is also demonstrated that this family of long fibre reinforced thermoplastics can be recycled successfully with considerable fibre length advantages over traditional extrusion precompounded short fibre compounds.

Effect of Injection Molding Conditions of Effective Surface Properties of F-theta Lens

Effect of Injection Molding Conditions of Effective Surface Properties of F-theta Lens

Effect of Injection Molding Conditions on Crystalline Structure and Electrical Resistivity of PP/MWCNT Nanocomposites.

Polypropylene (PP) / multi-walled carbon nanotube (MWCNT) nanocomposites were prepared by melt-mixing and used to manufacture samples by injection molding. The effect of processing conditions on the crystallinity and electrical resistivity was studied. Accordingly, samples were produced varying the mold temperature and injection rate, and the DC electrical resistivity was measured. The morphology of MWCNT clusters was studied by optical and electron microscopy, while X-ray diffraction was used to study the role of the crystalline structure of PP. As a result, an anisotropic electrical behavior induced by the process was observed, which is further influenced by the injection molding processing condition. It was demonstrated that a reduction of electrical resistivity can be obtained by increasing mold temperature and injection rate, which was associated to the formation of the γ-phase and the related inter-cluster morphology of the MWCNT conductive network.

Characterization of manufacturability of microstructures for micro-injection moulding of micro devices using star patterns

The replication accuracy of micro features plays a very important role in polymeric micro devices, such as microfluidic and micro optics. However, there is no effective way at the moment for the assessment of manufacturability of such microstructures. This study develops a new method of using a star pattern with a continuous change of width and aspect ratio to characterize the manufacturability of microstructures. The designed patterns have a width from 20 microns to 320 microns with an aspect ratio from 2.5 to 0.156. Concentric markers are designed on the star patterns for the easy identification of achievable feature accuracy under various processes. It is found that the dry etching and electroforming cause a depth error of less than 5%, while the maximum error from injection moulding is 2.8% where the channel aspect ratio is less than 1. However, when the aspect ratio of protrusion microstructures is higher than 1 with a width of 50 µm, insufficient filling occurs under nominal injection moulding conditions with relative error more than 10%. The designed star patterns are proved to be an easy and fast way to determine achievable feature accuracy for polymer micro replication processes, including injection moulding and hot embossing.

Experimental investigation and thermo-mechanical modelling for tool life evaluation of photopolymer additively manufactured mould inserts in different injection moulding conditions

There is a growing interest for integrating additive manufacturing (AM) technology in different manufacturing processes such as injection moulding (IM) due to the possibility of achieving shorter manufacturing times and increased cost effectiveness. This paper evaluates IM inserts fabricated by the AM vat photopolymerisation method. The inserts are directly manufactured with a photopolymer material, integrated on an injection moulding tool and subsequently used for IM. Therefore, particular attention has to be paid in order to develop the soft tooling process chain and the IM experimental procedure as detailed in this study. Different combinations of IM parameters are investigated in this work in order to determine the influence of the various process settings on the inserts’ performance (lifetime, crack propagation, consistency of the mould surface features). The mould inserts were analysed by three-dimensional optical metrology and evaluated with regard to the different surface features that were affected by the IM process. A three-dimensional thermo-mechanical with phase change model for the analysis of the effects of the IM process on the additive manufactured tools was accomplished in the FE software COMSOL Multiphysics. The potential causes for the insert failure are identified both by means of the IM experiments and the numerical model. The developed model could also predict the thermally induced deformations produced in the mould and identify where this phenomenon would eventually lead to defects in the shape of the parts. The influence of three different temperatures of the insert at 25 °C, 50 °C and 100 °C on the failure of the insert was investigated. Also a detailed discussion about the solidification and temperature changes is given.

Replication of Micro- and Nanofeatures in Injection Molding of Two PLA Grades with Rapid Surface-Temperature Modulation.

The production by injection molding of polymeric components having micro- and nanometrical surfaces is a complex task. Generally, the accurate replication of micro- and nanometrical features on the polymeric surface during the injection-molding process is prevented by of the low mold temperature adopted to reduce cooling time. In this work, we adopt a system that allows fast heating of the cavity surface during the time the melt reaches the cavity, and fast cooling after heater deactivation. A nickel insert with micro- and nanofeatures in relief is located on the cavity surface. Replication accuracy is analyzed by Atomic Force Microscopy under different injection-molding conditions. Two grades of polylactic acid with different viscosity have been adopted. The results indicate that the higher the cavity surface temperature is, the higher the replication accuracy is. The viscosity has a significant effect only in the replication of the microfeatures, whereas its effect results are negligible in the replication of nanofeatures, thus suggesting that the interfacial phenomena are more important for replication at a nanometric scale. The evolution of the crystallinity degree on the surface also results in a key factor on the replication of nanofeatures.

Effects of Injection Molding and Storage Conditions on Polypropylene Copolymer

Abstract This work focused on studying the effects of injection molding parameters (cooling time and melt temperature) and storage conditions (annealing versus cooling) on the thermal, mechanical, and optical properties of an ethylene-propylene copolymer made with and without nucleating agents. Preform properties (optical, crystallinity) affect the consistency of the preforms’ reheating via infrared lamps before stretch blow molding. The analysis of detailed preform properties as a result of both injection molding processing and postmolding treatment or preform storage conditions was lacking to correlate with the blow molding performance. This study confirmed that postmolding aging is a significant factor that affects material properties and therefore suggested subsequent blow molding. It also suggested that shorter injection molding cooling time helps to minimize the effects of aging and storage conditions. As expected, with the inclusion of the nucleating agent, clarity, yield strength, and density of the material improved.

Optimization of injection moulding process parameters in the moulding of High Density Polyethylene (HDPE)

In this study, optimal injection moulding conditions for minimum shrinkage during moulding of High Density Polyethylene (HDPE) were obtained by Taguchi method. The result showed that melting temperature of 190OC, injection pressure of 55 MPa, refilling pressure of 85 MPa and cooling time of 11 seconds gave minimum shrinkage for High Density Polyethylene. Cooling time was found to be the factor with most significant effect on the shrinkage of High Density Polyethylene followed by refilling pressure. Injection pressure was found to be the least effective factor.Keywords: High Density Polyethylene (HDPE), Injection Moulding, Process Parameters, Taguchi method.

Residual orientation in injection‐moulded plaques of atactic‐polystyrene I: The effect of processing conditions

Injection moulded polymer articles often have residual macromolecular or crystalline orientation which can have a significant impact on the optical and mechanical properties of the moulded article. Small angle neutron scattering (SANS) was used to measure the molecular shape and orientation of deuterated blends of injection moulded polystyrene. For ∼1‐mm‐thick mouldings of uniform rectangular cross‐section, the eccentricity in the SANS pattern gave a direct measure of the residual molecular orientation over the length scale ∼100–1,500 Å. The residual orientation was found to vary significantly with injection moulding conditions with comparative residual orientation decreasing with decreasing mould fill‐time, and increasing with mould thickness and moulding temperatures. The orientation was found to be a minimum in the centre of the mould and highest near the surface and the average orientation at a particular position in the mould was found to be strongly correlated with the volume of material deposited as a solid skin layer during injection moulding. POLYM. ENG. SCI., 58:1322–1331, 2018. © 2017 Society of Plastics Engineers

Evaluation of the injection moulding conditions in soy/nanoclay based composites

Biocomposites, and generally bio-based plastics, are seen as a promising alternative to conventional plastics because they are based on renewable natural components (eco-friendly) with a lower cost. Biocomposites using soy protein and glycerol were obtained with an injection moulding technique as the thermoprocessing method. Nanoclay (Montmorillonite, MMT-Na+) was included to improve physicochemical properties of novel SPI/MMT nanocomposites prepared by injection moulding, primary attending to water uptake capacity (WUC), but also considering rheological and mechanical properties. The influence of processing conditions has been studied in order to assess the modifications taking place in the microstructure and properties of these nanocomposites. Addition of MMT-Na+ improves mechanical properties and WUC of SPI-based materials, depending on processing conditions. Injection pressure only exerts a slight enhancement of mechanical properties and WUC. However, an increase in mixing time leads to a relevant increase in WUC without impairing the mechanical properties of nanocomposites.

PHBV Crystallization under Injection Molding Conditions: Influence of Packing Pressure and Mold Temperature

PHBV Crystallization under Injection Molding Conditions: Influence of Packing Pressure and Mold Temperature

Self-Assembly and Charge Transport of a Conjugated Polymer on ITO Substrates

The properties of a composite based on a high-density polyethylene Hostalen GD 7255 filled with a 10% addition of a glass powder called Mikrover were studied. The composite was obtained in the process of twin screw extrusion with cold pelletizing. The apparatus included a co-rotating twin-screw extruder with the extruder head equipped with a circular die, as well as a water cooling bath and a pelletizer. The mechanical properties of the composite were studied by producing appropriate specimens in the injection moulding process, at variable cooling times of the injection moulded parts and at variable volume rates of polymer composite flow to the injection mould cavity. The basic strength properties were determined by uniaxial tensile testing, and hardness was determined by the Shore method. It was found that injection moulding conditions influenced the mechanical properties under study. For example, an increase in cooling time was accompanied by an increase in stress at break. An increase in the volume rate of polymer composite flow to the injection mould cavity was accompanied by an increase in hardness, stress at break, tensile strength and strain at break.

Production and Characterization of Bioplastics Obtained by Injection Moulding of Various Protein Systems

Bioplastic materials from renewable polymers, like proteins, constitute a highly interesting field for important industrial applications such as packaging, agriculture, etc., in which thermo-mechanical techniques are increasingly being used. This study assesses bioplastic materials produced by injection from blends previously prepared in a batch mixer using various protein concentrates and isolates. A mixing time of 5 min has been selected in order to ensure correct homogenous blends. A comparison between different protein-based specimens was performed by dynamic mechanical thermal analysis, tensile strength, water uptake and transmittance tests. The comparison reveals that the protein nature and the percentage of plasticizer lead to bioplastics with different properties and, consequently, different applications. Protein concentrates and isolates, wastes and surpluses from the food industry, may be useful for producing bioplastics with suitable mechanical properties and processability, as well as biodegradability, by means of suitable mixing and injection moulding conditions.

An experimental investigation of the combined influence of notch size and fibre orientation on the fatigue strength of a short glass fibre reinforced polyamide 6

An experimental study of the fatigue strength of injection moulded short fibre reinforced polyamide plates is presented, which investigated the combined effect of notch tip radius and injection gate position on injection moulded specimens. Fatigue tests were conducted on samples having two symmetric V-shaped notches, with a fillet radius varying from 0.5 to 2 mm. The injection moulding conditions and resulting fibre orientation distribution were varied by injecting the plates longitudinally and laterally. For the same type of injection gate, the influence of the notch root radius appeared to be negligible, with the exception of the smallest radius which had a lower strength. Measurements of fibre orientation showed that the smallest radius modified the local fibre structure, and fatigue crack growth observations showed that the crack propagation phase become dominant with the smallest radius.

Development of crayfish protein-PCL biocomposite material processed by injection moulding

A combination of crayfish flour (CF, with 60% protein) and Polycaprolactone (PCL) was successfully used to prepare biocomposites by a process that consists of two stages: mixing with glycerol (GL) as plasticizer and injection moulding of CF/GL/PCL blends. Mixing rheometry and Differential Scanning Calorimetry (DSC) measurements were found to be useful to select suitable injection moulding conditions. A remarkable enhancement in mechanical properties was found for PCL containing systems, even when crystalline structure remains unaltered. PCL yields a dominant contribution to the elastic response and confer a higher ability to absorb energy before rupture, but also the protein/plasticiser ratio must be considered.

223 Effects of Annealing and Injection Molding Conditions on Tensile Properties of Short Carbon Fiber Reinforced PPS Plastic

223 Effects of Annealing and Injection Molding Conditions on Tensile Properties of Short Carbon Fiber Reinforced PPS Plastic

Process Factor Optimization for Reducing Warpage and Shrinkage in Injection Molding Using Design of Experiments

This Paper Presents the Optimization of Injection Molding Conditions to Minimize the Warpage and Volumetric Shrinkage Using Design of Experiments and Taguchi Optimization Method. Considering the Process Parameters such as Injection Time, Packing Pressure, Packing Pressure Time, and Cooling Time, a Series of Mold Analysis are Performed. Orthogonal Arrays of Taguchi, the Signal-to-Noise(S/N) and Analysis of Variance (ANOVA) are Utilized to Determine the Optimization Parameter Levels and to Find out Principal Processing Parameters on Warpage and Volumetric Shrinkage. from the Results it is Clear that Warpage and Volumetric Shrinkage are Reduced. also, the Dominant Parameters were Cooling Time and Packing Time for Warpage, on the other Hand, the most Important Factor for Shrinkage was Injection Time. from this, it can be Concluded that Taguchi Method is very Suitable to Solve the Warpage and Volumetric Shrinkage Problems in Injection Molding Parts.

Inverse method for the cooling system design in injection moulding – application to a ‘T-shaped’ piece

The designing of the cooling channels in the thermoplastic injection process is one of the most important steps during mould design. Indeed, inappropriate cooling will lead to defects in the piece and a low production rate. In this paper, a new approach for the design of cooling channels is presented. Based on morphological concepts, the idea of regulation by cooling surface is considered. The first part of the methodology leads to the optimal determination of fluid temperature distribution along the cooling surface in order to minimise a cost function composed of two terms linked to the quality of the piece and the productivity of the process. The conjugate gradient algorithm coupled with a Lagrangian approach is implemented for the determination of the optimal fluid temperature distribution. The method is applied to design the cooling system of a ‘T-shaped’ piece, and numerical results are then compared with those available in the literature for the same piece shape and the same injection moulding conditions.