Search results

The purpose of this paper is to review available technologies, analyse their features, propose a new approach of 3D sand mould printing based on line forming, introduce the manufacturing principle and show advantages of this approach, especially for larger parts with large Z steps in the build, such as 2 mm stepwise.

This paper introduces 3D sand mould printing, compares and analyses technological process and existing fabrication approaches among available technologies first. Then, a new approach of 3D sand mould printing is proposed to improve build speed. In addition, the proposed system will be analysed or benchmarked against existing systems.

A new approach based on line forming of sand mould printing is put forward by reviewing and analysing available technologies, to improve build speed from the aspect of basic moulding movement instead of optimization of moulding methods and process parameters. The theoretical calculation and analysis shows that build speed can be improved greatly, and it is more suitable for the manufacture of large-scale casting’s sand mould when considering dimensional accuracy and printing error, as well as uniformity of each layer.

The specific implement scheme of line forming and nozzle’s specific structure of this new approach need further study.

Much higher build speed of 3D sand mould printing with new approach brings evident implication for moulds companies and manufacturing industry, having a far-reaching influence on the development of national economy.

This paper reviews available technologies and presents a new approach of 3D sand mould printing for the first time. Analysis of the new approach shows that this new method of sand mould printing can boost build speed greatly. So, its application prospect is great.

The non‐isothermal filling of a powder/binder mixture in metal injection moulding is simulated by the viscoplastic and the heat conduction finite element methods. Proposes a simplified three‐dimensional scheme for the moulding of products with a non‐uniform thickness distribution. The computing time for the simplified three‐dimensional scheme is of the same order as that for two‐dimensional problems. Deals with complex overlapping between the surfaces of the mixture, resulting from the occurrence of jetting during the moulding, by the use of a remeshing scheme. The material flow in metal injection moulding into a rectangular die with a linear thickness distribution is simulated. The jetting behaviour is remarkably influenced by the thickness distribution of the die.

This paper aims to explore the influence of the materials used in moulding blocks of hybrid moulds on the injection moulding setup and the properties of the mouldings.

An instrumented (pressure and temperature) hybrid mould with exchangeable moulding blocks, produced by rapid prototyping and tooling techniques (RPT), was used to produce polypropylene tubular mouldings. The configuration of the mould was varied with combinations of moulding block materials, namely, an epoxy resin composite processed by vacuum casting and steel. The processing conditions were adjusted to obtained steady processing conditions. The mouldings were assessed in terms of the microstructure and the shrinkage.

Due to the properties of the moulding block obtained by RPT being different from tool steel, the injection moulding processing conditions and the plastics parts properties are different when hybrid moulds are used. The cycle time depends on the moulding block properties and must be adjusted to the desired running temperature. The morphology of the mouldings is strongly affected by the thermal properties of the moulding block materials. When different materials are used in the core and the cavity asymmetric structures develop in the part. The shrinkage of the mouldings, when resin cores are used is also affected by the deformation of the core caused by the injection pressure.

This paper makes a contribution to understanding the morphology of semi‐crystalline mouldings obtained using hybrid moulds and enhances the importance of the core deformation on the shrinkage of the mouldings.

Advances in rapid prototyping and machining have resulted in reduced lead times for injection moulding tooling. Comparisons between aluminium and stereolithography (SL) tools are made with regard to the ejection forces required to push mouldings from the tools, heat transfer through the tools and the surface roughness of the tools. The results show that ejection forces for both types of tools are increased when a longer cooling time prior to ejection is used. The ejection forces required from a rough aluminium tool are considerably higher than those from a smooth aluminium tool. SL tools do not appear to be subjected to any smoothing as a result of moulding polypropylene parts. The rubber like nature of the tool’s surface is as a direct consequence of the low glass transition temperature and low thermal conductivity of the tool material. Further potential benefits of the low thermal properties of the tool are discussed.

The purpose of this paper is to provide a demonstration of the application of techniques for robust optimization for improvement of the injection moulding processes in an injection moulding small and medium sized enterprise (SME).

A critical to quality characteristic (CtQ) which is connected to assembly problems is the subject of investigation. The CtQ is not directly measurable. The variation in a dimension of a product, which is correlated to the CtQ, is studied using design of experiments (DoE) and Taguchi methods. A two-cavity mould is used in the injection moulding process. To evaluate the robustness of the process using signal-to-noise analysis, the data were transformed to compensate for the systematic differences between the mould cavities.

The initial results showed that finding optimal process parameter settings commonly valid for both cavities was impossible. After a modification of the mould, the experiments were rerun and optimal settings could be found.

Applying DoE techniques in small and medium-sized injection moulding companies is far from common practice. This case study demonstrates a method to apply DoE with five process parameters which can serve as a standard method to prepare production when a new mould is used for the first time.

The originality is connected to the combination of the applied methods and, in the context of the case study, carried out in an SME unfamiliar with the power of the applied methods. The value of the paper is to demonstrate the power of the most powerful technique in quality engineering to improve an injection moulding process within the context of SMEs. The authors would accentuate the point that the true power becomes visible when this powerful technique is introduced into an organization with very little understanding of the technique. In addition, the case study is valuable to practitioners because it proposes a new scientific and systematic approach to understand and optimize the start-up of the moulding process.

In this work, the changes to stereolithography (SL) resin mechanical properties during the injection moulding process were evaluated. A multi‐impression SL mould was built and used to inject a series of small flat mouldings. The fixed half SL tool insert included recesses to accommodate tensile test specimens. Tensile test specimens made from SL resin were positioned in these recesses and plastic parts were injected. After injecting a predetermined number of mouldings, tensile tests were performed using the tensile test specimens. The results from the tensile tests show that the thermal cycling encountered during the injection moulding process did not significantly affect the mechanical properties of the resin. Observations indicate that decrease in the temperatures encountered in the tool may lead to longer tool life.

Robots have been used on plastic injection moulding machines for many years. Linear robots account for the vast majority of applications but there is a small increase in use of six‐axis articulated arm types for certain applications. This paper discusses the pros and cons for the various types being used and describes the downstream processes that can be incorporated within the automated cell.

The purpose of this study is to demonstrate and characterise a soft-tooled micro-injection moulding process through in-line measurements and surface metrology using a data-intensive approach.

A soft tool for a demonstrator product that mimics the main features of miniature components in medical devices and microsystem components has been designed and fabricated using material jetting technique. The soft tool was then integrated into a mould assembly on the micro-injection moulding machine, and mouldings were made. Sensor and data acquisition devices including thermal imaging and injection pressure sensing have been set up to collect data for each of the prototypes. Off-line dimensional characterisation of the parts and the soft tool have also been carried out to quantify the prototype quality and dimensional changes on the soft tool after the manufacturing cycles.

The data collection and analysis methods presented here enable the evaluation of the quality of the moulded parts in real-time from in-line measurements. Importantly, it is demonstrated that soft-tool surface temperature difference values can be used as reliable indicators for moulding quality. Reduction in the total volume of the soft-tool moulding cavity was detected and quantified up to 100 cycles. Data collected from in-line monitoring was also used for filling assessment of the soft-tool moulding cavity, providing about 90% accuracy in filling prediction with relatively modest sensors and monitoring technologies.

This work presents a data-intensive approach for the characterisation of soft-tooled micro-injection moulding processes for the first time. The overall results of this study show that the product-focussed data-rich approach presented here proved to be an essential and useful way of exploiting additive manufacturing technologies for soft-tooled rapid prototyping and new product introduction.

This paper presents results from the testing and benchmarking of a slip cast 316 stainless steel injection moulding tool. A brief out line of the slip casting process and the test cavity geometry is given as well as a discussion of some of the commercial alternative methods of forming injection moulding cavities. The calculations for the slip cast test cavity cost and lead time are given and comparisons between slip casting tool formation and alternative methods are made. The paper concludes that the slip casting method has potential in replacing some of the other tooling methods.

The purpose of this study is to compare the overall performance of the injection moulding process by using metallic inserts produced by both conventional technologies and selective laser melting (SLM).

A systematic methodology is proposed for prior evaluation of the effectiveness of conformal cooling channels to reduce cycle time and/or to reduce the scrap rate.

The mould was reengineered considering the SLM process and manufactured. Injection trials were carried out to validate expectations provided by injection simulations, which resulted on good quality parts and a significant decrease on cooling time, and, consequently, on the overall cycle time. The minimisation of scrap provided energy savings and time-to-market reduction.

The initial costs for AM tools still pose some doubts on decision-makers. The challenge of this study is to implement the methodology on a small-scale production and still ensure that benefits are achieved.

The case study selected for this research work is based on a parking sensor housing, which is a plastic part assembled on the vehicle’s front and rear bumpers, therefore, with aesthetics concerns. The part produced with the conventional mould exhibits surface defects that, to be minimised (not eliminated), require a longer packing time to diminish the sink marks.

The economic impact of the use of SLM is relevant despite the low batch size for the case study presented. Energy savings are achieved due to scrap reduction and shorter cycle time.

The systematic methodology proposed for prior evaluation of the advantages of conformal cooling is possible to be applied both on small scale and high production series.