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The purpose of this work is to extend the life of plastic injection molds made by stereolithography through the use of gas‐assist technology.

Polypropylene parts were made by injection molding in stereolithography molds with and without gas‐assist technology. The mold life was evaluated by observing the number of parts produced before the breakage of each of small core pins and the ejection force was measured.

When using gas‐assisted injection molding (GAIM), the core pin life was approximately doubled, the average cavity pressure and the average mold temperature were reduced, and there was a three‐fold increase in ejection force. Also, the core pin location had a very dramatic effect on the life.

This study suggests research into understanding the relationship between ejection force and mold failure, testing the mechanical properties of the parts and identifying reliable design rules for parts produced by GAIM. Research into other low pressure injection techniques and the viability of using a wider set of polymer materials also appears promising.

The result of this research encourages molders who have abandoned the use of stereolithography tools after a few unsuccessful attempts to consider using GAIM with stereolithography molds.

This is a novel use of GAIM technology to extend the lives of molds fabricated by stereolithography.

The purpose of this paper is to present the results of an investigation into the effect of injection molding process parameters on the performance of direct metal laser sintered (DMLS) mold in producing quality Zytel nylon 66 plastic parts with consistency in part shrinkage and shot/part weight.

The injection mold for an industrial component (hub gear) was fabricated in EOS M‐250 machine using bronze‐based material. The effect of four injection molding parameters (injection pressure, melt temperature, speed, and injection time) on part shrinkage and weight were studied experimentally using L₉ orthogonal array. The weight of the part just after ejecting from the cavity, and the average shrinkage measured after cooling, were used in grey relational analysis technique to assess the effect of each molding parameter. Further, surface properties such as surface finish, wear, scratch and corrosion resistance tests were conducted on DMLS mold material samples, in order to evaluate its use in rapid manufacturing applications.

The study found that injection speed and melt temperature have significant influence on part weight and shrinkage. The optimized molding process variables were slightly more in the case of DMLS molds as compared with the parameters suggested in the plastic datasheet. Scanning electro microscope (SEM) analysis of the mold surface after producing 5,000 glass filled Nylon 66 (Zytel) moldings did not indicate any surface degradation, confirming the use of DMLS mold in rapid manufacturing of few thousands of moldings.

The grey relational analysis does not compute the effect of any two or more variables together unlike ANNOVA. Second, this study alone is not enough to estimate life of DMLS mold, although 5,000 glass filled nylon 66 moldings are successfully produced without any damage on mold surface.

This investigation demonstrates a generic approach of using grey relational analysis to quantify the effect of different molding process variables on selected quality parameters. This method can be easily extended for new processes and materials. The preliminary tests on surface finish, scratch, wear and corrosion resistance performed on DMLS mold samples have highlighted the need for improving surface properties to enhance their life. The authors are currently working on hard coating of DMLS molds as one of the solutions.

Use of grey relational analysis is new to the problem of injection molding process optimization. Moreover, effect of injection molding parameters on part weight and shrinkage in DMLS mold has not been studied previously. This study helps while considering DMLS molds for manufacturing few thousands of parts.

Injection molding is a very mature technology, but the growth of layer‐build, additive, manufacturing technologies (rapid prototypying) has the potential of expanding injection molding into areas not commercially feasible with traditional molds and molding techniques. This integration of injection molding with rapid prototyping has undergone many demonstrations of potential. What is missing is the fundamental understanding of how the modifications to the mold material and mold manufacturing process impact both the mold design and the injection molding process. This work expanded on an approach to utilize current numerical simulation programs and created a tool for optimizing the creation and use of non‐metal molds for injection molding. Verification and validation work is presented. The model was exercised by studying the effect of varying the thermal conductivity on final‐part distortions. This work clearly showed that one could not obtain reasonable results by simply changing a few input parameters in the current simulations. Although the approach did produce more realistic results, more work will be required for a tool capable of accurate, quantitative predictions.

This purpose of this study is to investigate an effective method to manufacture propellers.

The investment casting process and injection molding process have been applied separately to the rapid prototyping/rapid tooling (RP/RT) to obtain metal (Al‐Si alloy) propellers and plastic (Acrylonitrile butadiene styrene – ABS) propellers. The two different manufacturing processes were compared following the same master model (MM). The Moldflow software is used to optimize the experimental parameters of the molding. Furthermore, a gypsum type of powder is used to produce the RP MM of the propeller according to the Pro‐E software. The RP MM then is filled with a metallic resin material (at room temperature) to obtain a wax mold. Then, this wax mold was coating by dipping the ZrO₂ slurry to improve heat resistant ability, and following solidification, and then filled with metal alloy to obtain metal (Al‐Si alloy) propellers. Another process, the RP MM by dipping the ZrO₂ slurry to increase the heat resistance and then is filled with aluminum alloy and an injection mold can be obtained, the plastic (ABS) propellers can be duplicated. To ensure the precision of dimension and improves the surface roughness for the RT (metallic resin mold and aluminum alloy mold), the contour of the duplicated molds were milling with the high‐speed CNC manufacturing program.

The advantage of this process is that combining the RP/RT system with the high‐speed CNC machining center enables easy production of injection molds.

This process provides engineers with a quick way to fabricate parts and modify the designs. This study demonstrates that this process provides a practical way to fabricate parts and saves the cost and time which increases market competition. The molds with high precision and good surface roughness were duplicated by the rapid‐prototype technique. Furthermore, this investigation demonstrates that: if the product contains special shapes? The material requires a large amount of cutting? or In the case of expensive and hard to machine materials, the proposed process is the best choice to duplicate cost‐effective mold.

Polymer rapid tooling (PRT) inserts can be used as injection moulding (IM) cavities for prototyping and low volume production but lack the robustness of metal inserts. Metal inserts can withstand high injection pressure and temperature required, whereas PRT inserts may fail under similar parameters. The current method of parameter setting starts with using the highest pressure setting on the machine and then fine-tuning to optimize the process parameters. This method needs modification, as high injection pressures and temperatures can damage the PRT inserts. There is a need for a methodical process to determine the upper limits of moulding parameters that can be used without damaging the PRT inserts.

A case study analysis was performed to investigate the causes of failure in a PRT insert. From this, a candidate set-up process was developed to avoid start-up failure and possibly prolong tool life. This was then tested on a second mould, which successfully avoided start-up failure and moulded 54 parts before becoming unusable due to safety issues.

Process parameters that are critical for tool life are identified as mould temperature, injection pressure, injection speed, hold pressure and cooling time.

This paper presents a novel method for setting IM process parameters for PRT inserts. This has the potential to prevent failure at start up when using PRT inserts and possibly extend the operating life of the PRT inserts.

This paper presents the simulation results of a glass fiber reinforced PA 6,6 composite automotive clutch pedal. The analysis is carried out using Moldflow Plastics Insight (MPI) software to investigate the effects of increasing gate number from 1 to 2 on temperature and pressure. The results of temperature show that for single gate, the temperature was 291.3 °C and for double gate was 292.3 °C. Double gates mold induce higher temperature due to longer runner length. Both designs revealed different hot spots locations indicating probable areas of excess shear heating. The results of pressure (end of fill), for the single gate it was 61.31 MPa and for double gate was 60.73 MPa. Double gates mold reduce the required injection pressure as well as pressure variation, hence a lower volumetric shrinkage. Lower injection pressure produces lower shear rate and shear stress level.

Adhesion has been measured between a powder injection molded (PIM) part and the stereolithography epoxy mold surrounding it after cooling. Analysis of release behavior suggests a link to the thermal properties of the mold material. Subsequent measurements of cooling in the part and at the part/mold interface are consistent with a one‐dimensional heat transfer model. Adhesion development at the part/mold interface shows a complex dependence on the thermal characteristics of both the mold and the PIM feedstock.

Values of parameters such as temperature, humidity, number of plastic products and the location of plastic injection moulds are required to determine the efficiency of plastic injection moulds with a view to improving the quality of the outputs. This article determined the appropriate sensors for the measurement of these essential parameters in the most suitable form of representation of the data to aid a proficient analysis of the data.

The outputs of these sensors were obtained by connecting the sensors to the general-purpose input/output (GPIO) pins of a Raspberry Pi and writing a Python programme for the connected GPIO pins. The values of the outputs of these sensors were represented in a graphical form. The connection of the Raspberry Pi and the sensors were done with a full-sized breadboard and jumper wires. A computer-aided design (CAD) of the connections was produced using Fritzing software.

The appropriate sensors determined are MLX90614 infrared thermometer sensor, DHT11 humidity sensor, pixy2 vision sensor and Neo-6m GPS sensor. This study proposed that the sensors analytic system be applied on an industrial plastic injection mould to measure and display the various parameters of the injection moulds for the purpose of understanding and improving the performance of the injection mould

An electronic system that provides the continuous values of essential parameters of a plastic injection mould in operation.

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder metallurgy and composite material processing are briefly discussed. The range of applications of finite elements on these subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE researchers/users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for 1994‐1996, where 1,370 references are listed. This bibliography is an updating of the paper written by Brannberg and Mackerle which has been published in Engineering Computations, Vol. 11 No. 5, 1994, pp. 413‐55.

In this study, a three‐dimensional (3D) flow model is used to approximate the crystallinity gradients of slowly crystallizing polymers developed in the injection molding process. A generalized second order parallel splitting formula is constructed to achieve both the accuracy and efficiency of the computation. Calculated values of flow‐wise (flow‐thickness plane) and width‐wise (width‐thickness plane) crystallinity distributions are obtained and compared with experimental results. The structure‐oriented simulation method developed is not only capable of describing moldability parameters, but is also able to predict the characteristics of ultimate properties of the final products.