Blow Moulding Research Articles

Conformal cooling channel design and CAE simulation for rapid blow mould

Blow moulding is one of the most important polymer processing technologies to produce hollow-shaped parts at a short time. The cooling stage takes up approximately two thirds of the complete blow moulding cycle. It becomes the major factor to determine the productivity and the quality of the blow-moulded part. The cooling time and the quality part are controlled by an adequate cooling channel design inside the blow mould. Inappropriate cooling channel design will increase the cooling time after part ejection. Recently, the success of integrating conformal cooling channel (CCC) design in the injection moulding process has been proven by different research publications and practices. The merit of the applications of CCC can also be extended to the existing blow moulding process. In this study, an effective design method is proposed for integrating CCC into the blow mould with the aid of computer-aided design and analysis tools. The fabrication of integrating CCC into the blow mould by rapid tooling technology is explored. Computer-aided engineering simulation is employed to verify the cooling performance of the CCC corresponding to the blow mould surface geometry. The analysed results are compared with those using the traditional straight line-drilled cooling channel (SLDCC) used in the blow moulding process. The results indicated that the cooling time and temperature uniformity of the blow-moulded part can be effectively improved. The proposed CCC design has a shorter cooling time and a lower part temperature than the SLDCC one.

Clariant develops liquid colour technology for polyolefin blow moulding, unveils new UV stabilizer range

Clariant develops liquid colour technology for polyolefin blow moulding, unveils new UV stabilizer range

Numerical Simulation of the Effect of Blowing Pressure on the Blow Molding of HDPE Oil Drum

Abstract: The computational fluid dynamics software POLYFLOW was used to simulate the inflation stage in extrusion blow molding of an HDPE oil drum and calculate the velocity distribution of parsion, the thickness distribution and contact time after inflation. The results show that, the thickness decreases as the blowing pressure increases. The thickness at the bottom and corners of the blown drum is thinner than that at others. The velocity increases as the blowing pressure increases after pinch-off. The parison contacts with the mould earlier as the blowing pressure increases. In the region of the handle, the contact time is the shortest.

A material model for multiaxial stretching and stress relaxation of polypropylene under process conditions

Polypropylene sheets have been stretched at 160°C to a state of large biaxial strain of extension ratio 3, and the stresses then allowed to relax at constant strain. The state of strain is reached via a path consisting of two sequential planar extensions, the second perpendicular to the first, under plane stress conditions with zero stress acting normal to the sheet. This strain path is highly relevant to solid phase deformation processes such as stretch blow moulding and thermoforming, and also reveals fundamental aspects of the flow rule required in the constitutive behaviour of the material. The rate of decay of stress is rapid, and such as to be highly significant in the modelling of processes that include stages of constant strain. A constitutive equation is developed that includes Eyring processes to model both the stress relaxation and strain rate dependence of the stress. The axial and transverse stresses observed during loading show that the use of a conventional Levy–Mises flow rule is ineffective, and instead a flow rule is used that takes account of the anisotropic state of the material via a power law function of the principal extension ratios. Finally the constitutive model is demonstrated to give quantitatively useful representation of the stresses both in loading and in stress relaxation.

Experimental Investigation of Stretch Blow Molding, Part 2: Analysis of Process Variables, Blowing Kinematics, and Bottle Properties

AbstractThe work presented in this paper takes advantage of newly developed instrumentation suitable for in‐process monitoring of an industrial stretch blow molding machine. The instrumentation provides blowing pressure and stretch‐rod force histories along with the kinematics of polymer contact with the mold wall. A design of experiments pattern was used to qualitatively relate machine inputs with these process parameters and the thickness distribution of stretch blow molded PET (polyethylene terephtalate) bottles. Material slippage at the mold wall and thickness distribution is also discussed in relation to machine inputs. The key process indicators defined have great potential for use in a closed loop process control system and validation of process simulations. © 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E436–E450, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21291

DESIGN AND FINITE ELEMENT ANALYSIS OF FRP LPG CYLINDER

This paper entails the design and finite element analysis (FEA) of a LPG cylinder made of E-glass fiber, vinylester resin and HDPE plastic composite The liner of the cylinder is made of HDPE plastic (blow moulding grade) and wound with continuous fiber E-glass composite with vinyl-ester polymer matrix. The cylinder cover is also made of HDPE plastic. The LPG cylinder was designed and tested for burst pressure of 3 MPa. The thickness of the cylinder was established to be 3.5 mm (1.5 mm of liner and 2 mm of FRP composite layer) using Abaqus software based FEA. Various design concepts were worked out alongwith a financial viability analysis. A strong, light, rust proof and semi-transparent LPG cylinder was aimed to be designed in this paper focusing on the use in the South African context.

Blow Molding Process Optimization of Amorphous Alloy Tube Blank Based on DEFORM Software

In recent years, with the increase of the research about forming technology of amorphous alloys, blow molding is explored to process the amorphous shell parts and containers both at home and abroad. Jan Schroers of Yale University found that it can improve the formability of amorphous alloys greatly by adjusting the thickness of plate blank and prefabricating parison. In this article, choosing Zr44Ti11Cu10Ni10Be25 as the study object, plate blanks with variable thickness are prefabricated to optimize the uniformity of the wall thickness of tube blank molded and studies the effects of blowing pressure and material viscosity on the formability of tube blank based on DEFORM software, so as to define the reasonable process parameters, provide theoretic foundation for blow molding process optimization of bulk metallic glasses (BMGs) plate and develop the industry application fields of BMG materials.

Stretch Blow Moulding of Mineral Filled PET

Injection Stretch Blow mouldng is a two step processing that was designed and optimized mainly using unfilled PET resins. This study focuses on stretch blow moulding of a PET filled with a few percent of sub micronic mineral fillers. Based on DSC, DMA, tensile tests as well as blowing on prototype machine main effects of fillers are analysed. It is demonstrated that fillers increases crystallization kinetics resulting in a reduction of the processing range. Difference in strain hardening induced by fillers makes it necessary to adjust blowing temperature. However main effect occurs during heating phase. Temperature within the perform is much less homogeneous than in PET making thermal gradient totally different if heating protocole is kept unchanged. Once heating is controlled to reach to equivalent thermal gradients as for PET blowing is possible and rather equivalent to that of pure PET.

Numerical Simulation of the Viscohyperelastic Behaviour of PET near the Glass Transition Temperature

The presentation deals with the non linear strongly elastic and viscous behaviour of poly ethylene terephthalate near the glass transition temperature and biaxially stretched at high strain rates representative of the injection stretch blow moulding process. A non linear visco-hyperelastic model inspired from [1] and identified from the experimental results of the equi-biaxial tension test [2], have been developed and presented in [3] is implemented into a finite element code developed with Matlab. The thermal behaviour modelling, identification and simulation has also been managed. First, a numerical simulation of 2D plane stress case has been performed involving 2 fields (global velocity V and elastic Cauchy Green tensor Be). Rectangular finite elements with quadratic and linear interpolations have been employed for velocity and the elastic left Cauchy Green tensor. Second, an axi symmetric formulation involving 4 fields (global velocity V, lagrange multiplier p associated with the global incompressibility condition, and multiplier q associated with the incompressibility of the elastic part) has been performed using rectangular elements. Degree of interpolation have been tested for all possible combinations to test the LBB like condition. Both simulations are compared with equi biaxial or sequential biaxial testing in order to reproduce the strain hardening effect and the self-heating observed. The final goal of this work is to perform the free blowing simulation to compare with experimental data. Therefore, we should solve an iterative procedure for a thermo-mechanical equation. At each time step, a four-field approach is adopted for the mechanical part, and a classical heat transfer equation is discretised for the thermal part.

Modification and Development of a Blow Molding Machine

This study is based on the modification and development of a two-liter plastic container blow molding machine into a five-liter one provided with a translucent view stripe. This study considers some objectives including reducing the total cost, increasing the amount of plastic recovery, and raising the desired plastic materials. Proper designs were prepared and directly applied on spot. Tangible results were obtained. Among others, the modification of some components of the machine, e.g. the extruder, has led to the possible reuse of the milled (recovery) and extra material from the manufacturing processes. That was also conducive to an effective reduction in the cost of production to 50% in some cases. Prior to its modification, this old machine was used to produce polyvinyl chloride (PVC) containers that have become prohibited these days for their damaging effect on man’s life. For now, and after modification, it has become possible to use High Density Polyethylene (HDPE) material, a fact that has improved labor conditions, too.

Blow Molding Process Optimization of Amorphous Alloy Tube Blank Based on POLYFLOW Software

Aimed at Zr44Ti11Cu10Ni10Be25 amorphous alloy and based on POLYFLOW software, studies the influence of die inlet diameter, blowing pressure and die transition fillet on the blow molding performance of tube blank systemly, and raises a new evaluation index to evaluate the formability of amorphous tube blank, limit height to diameter ratio (LHTDR) . The simulation results indicate that the forming limit of tube blank can be multiple improved with the decrease of die inlet diameter, blowing pressure has a significant effect on the forming limit which can be improved by decreasing the pressure, and the larger of the die transition fillet the higher of the forming limit in certain range. Finally, a set of reasonable process parameters is given which has great significance for guiding the formulation of blow molding process scheme.

New Strategies for Predicting Parison Dimensions in Extrusion Blow Molding

In this work, two new strategies were proposed for predicting the parison thickness and diameter distributions in extrusion blow molding. The first one was a finite-element-based numerical simulation for the parison extruded from a varying die gap. The comparison of simulated and experimental parison thickness distributions indicates that the new method has certain accuracy in predicting the parison thickness from a varying die gap. The second one was an artificial neural network (ANN) approach, the characteristics of which are in sufficient patterns that can be obtained without doing too many experiments. The diameter and thickness swells of the parisons extruded under different flow rates were obtained by a well-designed experiment. The obtained data were then used to train and test the ANN model. The dimension of one location on the parison can provide one pattern to train the ANN model. Trained and tested ANN model can be used to predict the dimensions at any location on the parison within a given range. The proposed two strategies can help search the processing conditions to obtain optimal parison thickness distributions.

CONCURRENT MANUFACTURING SYSTEM OPTIMIZATION FOR TWO-PRODUCT OPERATION

Product/process design and optimization are typically aimed at a single product for a single customer. Such approach, however, often leads to underutilization of available production capacity. It is therefore reasonable for the manufacturer to make an effort to minimize available excess capacity to improve overall facility performance. Excess capacity can be allocated to the production of another product/process design, which can be also independently optimized. However, exploring possible synergies between the two products/processes may bring higher benefits. This paper presents a case where a manufacturing process (plastic blow moulding) was shared among two different products for two different customers, each with a different set of needs. These customer needs were mapped into core value-creating processes, recognizing both the differences in their requirements as well as the similarities in their expectations. Conflicting differences in complexity, production volumes and quality requirements were reconciled using QFD_based approach, and led to improved customer satisfaction and cost performance.

State-of-the-Art of Rotational Moulding Technique and its Application

With the rapid development of plastic products in the world and the increasingly sophistication of plastic technology, rotational moulding (RM), has become the most practical and irreplaceable way of producing the large and super large containers like tanks, tank, etc. Compared with injection moulding and blow moulding, RM has the characteristics of low cost and easy-to-use, and its application has been extended into many domains. The principle of rotational moulding and comparison of raw material by the requirement of rotational moulding is introduced. The paper emphasizes the introduction of state-of-the-art of RM equipment; also it points out the development of RM.

Modelling Behaviour of PET for Stretch and Micro-Blow Moulding Applications Using an Elasto-Visco-Plastic Material Model

Abstract Polyethylene terephthalate (PET) has been widely used in the stretch blow moulding (SBM) process for packaging applications. Finite element analysis has become extensively useful for assessing container designs and enabling the designers to perform analyses earlier in the design cycle to determine the best material and the best structure. However, there are several challenging issues due to various processing parameters and complex material behaviour, which is both temperature and strain-rate dependent. In this paper, we generalize the G'Sell-Jonas law in the three-dimensional (3D) case to model and simulate the elasto-visco-plastic (EVP) behaviour of PET, taking into account strain-hardening and strain-softening. In addition, it is observed that the internal pressure (inside the preform) is significantly different from the nominal pressure (imposed in the blowing device upstream) since the internal pressure and the enclosed volume of the preform are fully coupled. In order to accurately simulate this phenomenon, a thermodynamic model was used to characterize the pressure-volume relationship (PVR). The predicted pressure evolution is therefore more realistic when imposing only the machine power of the blowing device (air compressor or vacuum pump). Mechanical and temperature equilibrium equations are fully nonlinear and solved separately with implicit schemes on the current deformed configuration, which is updated at each time step. Biaxial characterization tests were used to determine the model parameters in order to simulate the SBM process using the PVR. Three industrial case studies, comparing simulated thickness predictions to experimental measurements, will be presented in order to illustrate the applicability of the proposed model.

Optical measurement and modelling of parison sag and swell in blow moulding

Blow moulding is a process whereby a cylindrical parison is extruded first, then pinched between the two halves of a mould and, finally, blown into the product. Parison size and shape result from complex interactions between mandrel and die geometries, processing parameters and viscoelastic properties of the polymeric material. Moreover, parison size changes with time due to sag. An innovative, contactless and online measurement technique of the parison is shown to be an effective tool to measure precisely parison diameter and thickness and to capture dimensional changes with time. This technique employs laser lighting of the parison and hinges on the refractive properties of molten polymer. Images taken with a digital camera are processed to give a precise measurement of diameter and thickness, at different time step during extrusion. Thus, parison swell and sag have been recorded for a commercial HDPE. Influence of processing parameters such as the rotational screw speed or die gap width can be brought forward. From the measurements, thickness swell is found to possess a different behaviour from diameter swell. Moreover, sag has been measured and can be modelled from a Newtonian perspective using one dimensional convected coordinates. Parison sag is shown to be governed by two parameters: an extrusion velocity and a a single coefficient of sagging susceptibility which value has been deduced from experiments.

Numerical Analysis of Green Sand Compaction for Rectanglar Cavity in Blow Molding

Numerical Analysis of Green Sand Compaction for Rectanglar Cavity in Blow Molding

Three-Dimensional Shell Fabrication Using Blow Molding of Bulk Metallic Glass

A blow molding method based on thermoplastic forming of bulk metallic glasses (BMGs) is used to fabricate 3-D microshells. The 3-D microshells are attached to the Si wafer through mechanical locking, which is achieved in the same processing step. Versatile sizes and shapes of the 3-D shells can be precisely controlled. High strength ( >; 1 GPa), elasticity (~ 2%), and controlled surface roughness (<; 2 nm), which are achievable for BMGs, suggest their potential use in devices, including resonators, microlenses, microfluidic, and packaging.

Design and Strength check of Large Blow Molding Machine Rack

Design procedure of large blow moulding machine rack is discussed in the article. A strength checking method is presented. Finite element analysis is conducted in the design procedure by ANSYS software. The actual situation of the rack load bearing is fully considered. The necessary means to simplify the model are done. The dimensional linear element Beam 188 is analyzed. MESH200 is used to mesh. Therefore, it simplifies the analysis process and improves computational efficiency. The maximum deformation of rack is 8.037mm: it is occurred in the position of accumulator head. The result states: it meets the national standard curvature which is not greater than 0.3% of the total channel length; it also meets strength requirement that the maximum stress was 54.112MPa.

Simulation of the stretch blow moulding process: from the modelling of the microstructure evolution to the end-use elastic properties of polyethylene terephthalate bottles

The whole stretch blow-moulding process of PET bottles is simulated at the usual process temperature in order to predict the elastic end-use properties of the bottles. An anisotropic viscoplastic constitutive law, coupled with microscopic variables, is identified from uniaxial tensile tests performed at different strain rates and temperatures. The microstructure evolution is characterised by crystallinity measurements from interrupted tests and frozen samples. For each specimen tested, the Young modulus is measured at room temperature. Numerical simulations of the blow moulding process are run using the C-NEM method. A micromechanical modelling is post-processed after the simulation to predict the elastic properties. Predictions of Young modulus distributions in bottles are in agreement with the ones measured on blow-moulded bottles.