Rotational Moulding Process Research Articles

An Integrated Dynamic and Quality Modeling Framework for Batch Processes

This manuscript considers batch process operations and addresses the challenge of identifying a model that synergistically captures the dynamic input–output behavior of continuously measured variables along with the quality variables measured only at batch termination. To this end, an optimization-based framework is developed to identify one model that captures both the dynamics between the inputs and the continuously measured output variables, measurements of which are available at every time step, and the relation between the dynamic “state” information and the terminal quality measurements. Existing approaches either do not identify the dynamic and the quality model simultaneously, or they simply connect the whole trajectory of the process variables with the qualities and do not address the dynamic relationship between the inputs and the process variables. The improved modelling performance of the model obtained from this approach is demonstrated using data from a Uni-axial Rotational Molding process, and compared with existing modelling approaches.

Development and optimization of machine learning models for estimation of mechanical properties of linear low-density polyethylene

A hybrid methodology was developed and implemented for estimation of polymeric mechanical properties in rotational moulding process. The considered polymer in this study is linear low-density polyethylene, known as LLDPE, which has extensive application in plastic industry. The mechanical properties of the polymer were assessed and correlated to the oven residence time to build the predictive model of moulding process. A tiny dataset containing only 25 data rows via a number of machine learning models were assessed. Oven residence time is the only input, while the LLDPE's properties including tensile strength, impact strength, and flexure strength are the outputs considered in the machine learning models. We used tree-based ensemble methods for modeling in this work and they are tuned using FA (Firefly Algorithm) optimizer to find optimal hyper-parameters of them. Finally, the optimal models had shown a great performance to predict the output accurately. For tensile strength, the best model (FA-ET) has an R2 value of 0.9994, this score is 0.9995 for impact strength and 0.9968 for flexure strength. The tree-based models tuned in this study revealed to be robust in estimation of polymeric properties and can be used to obtain the products with the best quality.

QFD-Driven Rotational Moulding Optimization and Quality Control to Reduce Defects and Increase Efficiency in LLDPE Fuel Tank Production

The present study utilized a House of Quality (HoQ) methodology to develop a fuel tank manufactured using the rotational moulding process, employing LLDPE material. In order to methodically tackle this issue, three House of Quality (HoQ) charts were created, outlining consumer demands, functional necessities, and production control parameters. The results of the study emphasize the critical significance of identifying and adapting essential customer requirements, functional prerequisites, and production control parameters throughout the design and production phases of rotational moulded fuel tanks. The inquiry findings emphasized that the major customer requirements were on the provision of a fuel tank that possesses qualities of strength, longevity, reliability, and cost-effectiveness, while also ensuring a prolonged lifespan and an aesthetically pleasing external appearance. Furthermore, it was determined that the material qualities and tank design are the most crucial functional requirements. In addition, the precise regulation of oven temperature and the automation of the moulding process have been identified as crucial control criteria in guaranteeing the quality and functionality of the fuel tanks.

Defect Analysis Through Metallurgical Testing Methods for Linear Low-Density Polyethylene (LLDPE) at Different PIAT Values During Rotational Molding Process

Defect Analysis Through Metallurgical Testing Methods for Linear Low-Density Polyethylene (LLDPE) at Different PIAT Values During Rotational Molding Process

Adaptive Predictive Control Algorithm for Batch Processes: Application to a Rotational Molding Process

The present manuscript addresses the problem of handling process nonlinearity in batch process operations and control via a re-identification-based subspace identification approach deployed within a model predictive control (MPC) framework. In contrast to existing re-identification algorithms for continuous and batch processes, where all of the recent and past experimental data is chosen to re-identify the model, the proposed approach is designed to use the most appropriate subset of the data. In particular, the data for re-identification is determined by first determining the equivalent of a “locator” index from the training data set, and only using the portion of training batches from the locator to batch termination. The idea is to try and build the model using data pertaining to the state-space region that the system is presently passing through. The proposed approach is implemented on a rotational molding lab-scale setup coordinated via an existing model monitoring technique deployed within the MPC, which detects the model mismatch and triggers the re-identification algorithm. Validation data sets are first used to demonstrate the improved model resulting from the proposed re-identification approach, followed by experimental results demonstrating improved closed-loop performance.

Observations of Polymer Foam Development during Rotational Moulding

Large scale buoyant structures typical of offshore wave energy generation devices may be produced using the rotational foam moulding process. Due to the challenging environmental conditions these parts experience during their lifetime at sea, it is important that the structures are optimised to ensure acceptable mechanical performance. Foams containing large cells suffer a reduction in mechanical properties; therefore, an optimal foam contains small, evenly sized, and well distributed bubbles in large numbers. Due to the lower pressures used in the process, this can be challenging to achieve. Careful selection of material and processing conditions is required to achieve an optimal structure. A unique bench-based rig was used to observe developing foam structures. A camera was used to record the foam height change at intervals. Foam height change was obtained using digital image analysis. Several parameters were studied such as the polymer particle size or the mould pressure for example. In addition to the foam height change, foam density were analysed. It is found that mould pressure, polymer particle size, chemical blowing agent concentration, and polymer rheology may be used to control the foamed structures.

Assessment of processibility and properties of raw post-consumer waste polyethylene in the rotational moulding process

Abstract This paper presents work from an ongoing study into the use of post-consumer waste polymer in the rotational moulding process. Raw plastic recyclate, predominantly consisting of polyethylene, was processed into polymer powders containing an additive package suitable for rotational moulding, with and without the addition of a compatibiliser. Rheological studies on the materials showed very high viscosities at low shear rates in comparison with materials typically used in rotational moulding, which has significant implications for melt flow and bubble removal during the process. It was possible to mould the materials successfully, but poor surface finishes were achieved. Impact strength was drastically lower for recyclate mouldings compared with virgin material. Tensile strength of the recyclate mouldings was reduced compared to virgin polyethylene, but results indicated that optimising the processing conditions could lead to improvements. This work gives some baseline indicators to inform further planned work on optimising processing conditions and identifying viable material compositions.

Rotomoulding release agent preparation for auto part fabrications

As it produces parts with intricate details and finishes, minimal waste, few stress points, and excellent wall thickness uniformity, rotational moulding is one of the commercial shaping processes for manufacturing polymeric automotive parts. Use of a mould release agent is critical for a demoulding approach in rotational moulding, and the main requirement for typical use of a mould release agent is suitability in work environments at very high temperatures (>200 °C). Surprisingly, Thailand has approximately 2000 mould manufacturers, which can be attributed to the high demand for mould release agents; however, a vast majority of release agents are imported from abroad. This research aims to formulate the semi-permanent water-based release agents for shaping engineering plastics via a rotational moulding process. The main functions of the produced release agent include allowing the resin to become attached to the mould wall during the initial heating phase of the moulding cycle, ensuring that the fully molten skin of the rotomoulded part remains in close contact with the mould wall throughout the heating cycle. The rotomoulded part must remain in close contact with the mould wall during the initial part of the cooling cycle until the part has enough cohesion within its structure to resist collapse when the release process begins. The release agent used to aid in the quick release of rotomoulded parts while minimizing surface abrasion damage. First, chemical characterizations were performed using Fourier-transform infrared spectroscopy. Next, processability, surface characteristic, thermal stability, adhesion performance, and rheological characteristic were observed via Fourier-transform infrared spectroscopy, contact angle, thermogravimetric analysis, differential scanning calorimetry, adhesion tester, and rheometer, respectively, to inspect the possibility of using the produced release agents for a rotational moulding process. Experimental results confirm successful formulated rotomoulding release agent, however; the repetition of using a release agent needs further improvements for cost reduction.

Rheological and Thermal Investigation of Industrially Processed Glass Fiber Blended with Linear Low-Density Polyethylene for Rotational Molding Process

Rheological and Thermal Investigation of Industrially Processed Glass Fiber Blended with Linear Low-Density Polyethylene for Rotational Molding Process

Treatment of hemp fibres for use in rotational moulding

The benefit of using alkali-treated hemp fibre as the reinforcement for rotationally moulded polyethylene composites was evaluated in this research. Untreated and alkali-treated hemp fibre were characterised using different techniques such as scanning electron microscopy (SEM), thermal analysis, and Fourier transform infrared spectroscopy (FT-IR). These techniques showed that the alkali treatment removed non-cellulosic components from hemp fibres, which improved their separation and thermal resistance. Composites with alkali-treated fibre resisted the exposure to elevated temperatures for prolonged periods (characteristic of the rotational moulding process) with no apparent signs of thermal degradation, unlike when untreated fibre was used. The effect of using maleic anhydride grafted polyethylene (MAPE) as a coupling agent was also investigated. The addition of 3 wt% MAPE improved the properties tensile strength and Young's modulus of composites with treated hemp fibre, which was attributed to better fibre-matrix adhesion. Different fibre contents were assessed in this research to produce rotationally moulded composites; a poor fibre distribution was observed above 5 wt% fibre content, which resulted in low tensile strength and Young's modulus.

A comparative study of mechanical, dynamic mechanical and morphological characterization of tampico and coir fibre-reinforced LLDPE processed by rotational moulding

Natural fibres find their application as a reinforcing agent for polymer composites to obtain parts with improved mechanical properties. Manufacturing of non-metallic products is incorporated with natural fibres for better strength and to reduce cost. Rotational moulding is a process used for the manufacturing of hollow plastic products, especially water tanks, plastic fuel tanks, barrels, kayaks, refrigerated panels, etc. Incorporation of natural fibres to reinforce polymers in rotational moulding process is a tedious task; since there is no control over fibre and polymer powder mixture, which is rotating bi-axially, it may lead to fibre agglomeration. The present work investigates the mouldability of linear low density polyethylene composites with tampico and coir fibre as the reinforcement agents using a bi-axial rotomoulding machine. NaOH-treated fibres with 5, 10 and 15% by weight have been added to the linear low density polyethylene matrix, and the composites were prepared by rotational moulding process. Mechanical properties such as tensile strength, flexural strength, impact strength and hardness have been investigated. Dynamic mechanical behaviour such as storage modulus, loss modulus and tan δ of the different composites has been investigated with dynamic mechanical analyser. Fractured surfaces were examined qualitatively with the help of a scanning electron microscope for determining the interfacial properties and fibre adhesion between the fibres and the linear low density polyethylene matrix.

Hybrides Rotational-Moulding-Verfahren/Hybrid rotational moulding process – Cost-efficient manufacturing of lightweight components by intrinsic hybridization

Hybride Faserverbund-Metall-Bauteile für Anwendungen als Antriebswellen, Achsen oder Zug-Druck-Stangen besitzen aufgrund ihres hohen Leichtbaugrades ein enormes Potenzial in den unterschiedlichsten Branchen. In diesem Beitrag wird das Rotational-Moulding-Verfahren vorgestellt, mit welchem derartige Bauteile schnell und kostengünstig hergestellt werden können.   Hybrid fibre-composite metal components for applications as drive shafts, axles or tension-compression rods have enormous potential in a wide range of industries due to their lightweight construction properties. This article presents the rotational moulding process to produce such components quickly and economically.

Processing and characterization of HDPE and MDPE processed by rotational moulding

Rotational moulding otherwise called as roto moulding is a process used to produce hollow plastic products with nearly stress free objects with the help of a bi axial rotational moulding machine which rotates the mould in two axes with minimum speed of rotation. Plastic granules pulverized into fine powders are used to produce hollow parts such as water tanks, fuel tanks, kayak boats, refrigerated panel etc. The present work investigates the mouldability of High Density Poly Ethylene (HDPE) and Medium Density Poly Ethylene (MDPE) powders by rotational moulding process. A lab model roto moulding machine has been fabricated. There are two rotating frames – an inner and an outer frame – both rotating about two mutually perpendicular axes. The driving torque is given by a motor. The machine was designed to accommodate a rectangular shape stainless steel mould. Both MDPE and HDPE were processed at three different internal air temperature and the mechanical properties were estimated as per ASTM standards. Both tensile and impact strength were observed to be improved by the increase in internal air temperature. Hardness values observed shows no significant effect on internal air temperature. The MDPE products showed higher impact strength while HDPE products showed higher tensile strength. The morphology of the MDPE and HDPE powders and the microstructure of the products were studied under optical microscope.

Fracture toughness of LLDPE parts using rotational moulding technology

Rotational moulding is a process of producing hollow plastic products. Linear low density polyethylene (LLDPE) is widely used in rotational moulding process. Many rotationally moulded LLDPE products are widely used in outdoor applications such as boats, automobile fuel tanks, body armours etc. From quality characterisation point of view, fracture properties are considered to be critical for rotationally moulded products. Therefore, it is essential to optimise process parameters for rotational moulding process to yield maximum fracture toughness. In this paper, experimental investigations are carried out by planning and performing trials based on design of experiments (DOE). Experimental runs and design of experiments (DOE) analysis revealed non-linear effects of process parameters on fracture toughness. From the experimental investigation, optimum process parameters are proposed which yields maximum fracture toughness for rotationally moulded products. The optimum process parameters are oven temperature: 210°C, oven time: 32 minutes, and cooling medium: water.

The Usage of Recycled Material in Rotational Molding Process for Production of Septic Tank

Rotational molding is the forming process that use in produce large product, complexity product and hollow product with the limitation of process ability and material. Most of the rotational molding is a large product with a longer useful life compare to other technique, so to reused the material from other process can help to increase the competition of rotational molding in the market. This paper chooses recycled HDPE from blowing process due to it generally used by the market and not difficult to find. So in this paper choose to studies the blend of virgin LLDPE (linear low density polyethylene) and recycled HDPE (high density polyethylene) for application in septic tank by rotational molding process. Various ratio of blending were investigated to find the morphology, mechanical properties and the relation of melt flow rate and rheology. Mechanical properties are generally referred to tensile test, hardness test, impact strength and Morphology by Scanning Electron Microscope. Many studies have carried out to investigate about rotational molding forming process control, mold and process condition, some on material ability and new material to used in rotational molding to improve the mechanical properties and various technique in forming by rotational molding. But this article will investigated more about the use of recycled material from other forming technique process (which refer to blowing process in this article) to use in rotational molding process for produce septic tank compare to the commercial quality.

Influence of Rotational Moulding Process Parameters on Accuracy of Polymer Casts

The present paper describes the experimental tests undertaken to examine the influence of rotational speeds of two axes of the mould on properties of casts produced in the rotational moulding process. The general principles of this polymer processing technology have been described. The main applications have been introduced, and leading advantages and typical disadvantages of rotational moulding process have been told over. Rotational mould's speed around axes was changed, and a thickness of cast walls has been measured also with average surface concentration of colorant in cast walls. Laboratory test stand, processing properties of polymer, also test program and experimental test methodology have been described.

Modelling of an innovative liquid rotational moulding process

An innovative liquid rotational moulding process aiming at using standard injection-moulding polymer grades, shortening cycle times and at accessing more higher-end markets is studied. In this new process, the polymer is melted beforehand in a conventional injection unit and injected into the mould rotating around two axes. This work focus on modelling the liquid polymer flow occurring in this process, as well as providing guidance on the choice of process parameters. First, a stability criterion for rimming flow is derived, defining the process and material parameters space available for a functional process. From this criterion, it appears that initial thickness, and density have a destabilising effect, while liquid viscosity and angular velocity have a stabilising effect. Next, using Lax-Friedrichs scheme, the one-dimensional transient gravity driven liquid film is numerically modelled, linking the total extent of spreading to the frequency of orientation reversals and to the major and minor angular velocities ratio : the closer this ratio to one, the larger the extent of spreading. Then, Computational Fluid Dynamics (CFD) simulations are carried out to take into account three-dimensional features in the moulding of a cube part. Finally, comparison with trials performed on the moulding of the same cube part validates entirely this approach. In particular, some peculiar features of spreading can only be explained and reproduced when employing three-dimensional CFD simulations.

Design of a Plastic Auto’s Door Based on the Rotational Molding Process

In order to reduce the weight of the car, which made molded plastic door through rotational molding process. According to characteristics of rotational molding process, design plastic doors structure using UG software. By contrast the design of traditional sheet metal door, introduces the rotational molding process several key technologies of structure design of door from the simple molding, doors internal strengthening of structures and accessories.

Effect of Cooling Medium on Fracture Toughness of Rotomoulded Product

In day-to-day life, usage of plastics is numerous. It offers variety of benefits compared to other materials in various sectors like house hold applications, agricultural industry, and packaging, etc. There are numerous methods for processing plastics. These include: blow moulding, injection moulding, rotational moulding, transfer moulding and thermoforming. Rotational moulding is a competitive alternative to other plastic manufacturing process, since it offers designers an opportunity to achieve an economic production of stress free products. Many products made by rotational moulding process using linear low density polyethylene (LLDPE) are widely used in outdoor applications such as boats, over head tanks, and car body parts etc. In such applications, fracture properties are considered to be critical from the quality characterization point of view. Selection of appropriate cooling medium plays vital role to enhance the quality of rotomolded products. In this paper, an attempt has been made to investigate the effect of cooling medium on fracture toughness of the rotationally moulded products. Fracture tests are carried out on a compact tension (CT) test specimens prepared as per the ASTM D 6068 (2012). The tests are performed on a universal testing machine. R-curve method is used to determine the fracture toughness (JIC) of rotomoulded products. From the experimental results it is found that rapid cooling method favours better fracture toughness of rotomoulded products. Therefore, it is recommended to use faster cooling aids like water cooling in rotational moulding process to achieve highest fracture toughness.

Impact strength investigation of foamed linear low density polyethylene in rotational moulding process

Rotational moulding of foamed polyethylene has increasingly become an important process in industry. The main focus of this article is to examine the rotomouldability of a foamed polyethylene and their impact strength. As components produced using rotational moulding process are used in outdoor applications (like overhead chemical storage tanks, water storage tanks, automobile fuel tanks, car bodies, etc), impact strength of such products is considered as one of the prime quality feature. The work centres on the use of statistical technique to analyse the impact strength of foamed rotationally moulded products. The investigations are done on a typical linear low density polyethylene (LLDPE) mixed with 6% LLDPE foam material. Experimental runs and analysis based on design of experiments (DOE) revealed nonlinear effects of process parameters on impact strength. It is found that maximum impact strength of the foamed rotomoulded product could be obtained by optimal fixing of process parameters.