NOVEL TECHNIQUES FOR REDUCING COOLING TIME IN POLYMER INJECTION MOULDS USING RAPID TOOLING TECHNOLOGIES

In this research, thermal simulations and injection moulding experiments were performed to compare moulds having cooling channels of circular cross section and those with profiled cross section channels. Studies have been performed on the cooling time reduction in plastic injection moulding by different techniques utilizing thermal simulations and thermal measurements during experiments. Rapid Tooling (RT) technique, which is a manufacturing technique used to produce injection mould tools in a short period of time, has been applied in this research to fabricate injection moulds having circular and profiled conformal cooling channels. Injection moulding experiments for parts was done with these RT moulds using a vertical injection moulding machine. Manufacturing of mould patterns was done using 3-dimensional Printer Rapid Prototyping machine which used wax as the build material. Wax patterns were designed, fabricated and used to fabricate the mould cavity and channels. Aluminum Filled Epoxy material was used for the fabrication of mould cavities having circular conformal cooling channels and profiled conformal cooling channels. As the thermal conductivity of aluminum filled epoxy is much lower than metal moulds, another innovative concept which was embedding a metal insert around the cavity, was also applied for enhancing the heat dissipation. The metal insert was fabricated from aluminum. The concept was tested by fabricating moulds with aluminum inserts. All moulds were tested by injection moulding experiments with embedded thermocouples to measure the temperature of the cavity surface and temperatures were recorded with a data logger. Analysis of the temperature data indicated that the profiled channels had an increased heat dissipation and reduction of cooling time of about 17 percent over the circular channels. With the moulds having aluminum inserts, there was an impressive increase in cooling rate and the cooling time was further reduced by over 50 percent as compared to moulds without inserts

NOVEL TECHNIQUES FOR REDUCING COOLING TIME IN POLYMER INJECTION MOULDS USING RAPID TOOLING TECHNOLOGIES

In this research, thermal simulations and injection moulding experiments were performed to compare moulds having cooling channels of circular cross section and those with profiled cross section channels. Studies have been performed on the cooling time reduction in plastic injection moulding by different techniques utilizing thermal simulations and thermal measurements during experiments. Rapid Tooling (RT) technique, which is a manufacturing technique used to produce injection mould tools in a short period of time, has been applied in this research to fabricate injection moulds having circular and profiled conformal cooling channels. Injection moulding experiments for parts was done with these RT moulds using a vertical injection moulding machine. Manufacturing of mould patterns was done using 3-dimensional Printer Rapid Prototyping machine which used wax as the build material. Wax patterns were designed, fabricated and used to fabricate the mould cavity and channels. Aluminum Filled Epoxy material was used for the fabrication of mould cavities having circular conformal cooling channels and profiled conformal cooling channels. As the thermal conductivity of aluminum filled epoxy is much lower than metal moulds, another innovative concept which was embedding a metal insert around the cavity, was also applied for enhancing the heat dissipation. The metal insert was fabricated from aluminum. The concept was tested by fabricating moulds with aluminum inserts. All moulds were tested by injection moulding experiments with embedded thermocouples to measure the temperature of the cavity surface and temperatures were recorded with a data logger. Analysis of the temperature data indicated that the profiled channels had an increased heat dissipation and reduction of cooling time of about 17 percent over the circular channels. With the moulds having aluminum inserts, there was an impressive increase in cooling rate and the cooling time was further reduced by over 50 percent as compared to moulds without inserts

Prevalence of Sleep Paralysis in the Medical Students of a Local Medical College

Abstract Objective: To find out the prevalence of sleep paralysis among the medical students of a local Pakistani medical college. Methodology: This cross-sectional study was conducted on 107 medical students from, Karachi Institute of Medical Sciences (KIMS), Karachi, Pakistan. Non-probability Convenient Sampling Technique was utilized for this study. Students suffering from any psychiatric illness were excluded from this study. The study was performed after taking permission from the Institutional Ethical Review Committee. Written informed consent was taken from all the students. The data were collected using a pretested predesigned Questionnaire which was consisted of 10 questions related to the common10 happening and symptoms of sleep paralysis. Data were recorded in the form of frequency and percentages and analyzed using SPSS 24. Results: 52% (56 out of 107) participants have had an experience of sleep paralysis. Most of the participants (76.6%) described their experience as an Inability to move. Frequency of experience ranged from 0 to 20 times in the last year. Age at first experience ranged between 10-20 years. Conclusion: We found a high prevalence of sleep paralysis (47.2%) among the medical students at a local Pakistani medical college. Majority of the students experienced the phenomenon multiple times in their life. The students associated the symptoms the factors such as academic stress, anxiety, workload, emotional experiences, sleep deprivation, work routine, sleep pattern, sleep deprivation, fatigue, mental disturbance, studies and routine stress. 37.3% of the students also related the phenomenon to their position of sleep (lying on back). The participants described the experience as a source of great distress. Sleep paralysis needs to be studied, investigated and addressed in context of mental health of the students

Effect of raster angle and infill pattern on the in-plane and edgewise flexural properties of fused filament fabricated acrylonitrile–butadiene–styrene

Fused Filament Fabrication (FFF) is a popular additive manufacturing process to produce printed polymer components, whereby their strength is highly dependent on the process parameters. The raster angle and infill pattern are two key process parameters and their effects on flexural properties need further research. Therefore, the present study aimed to print test specimens with varying raster angles and infill patterns to learn their influence on the in-plane and edgewise flexural properties of acrylonitrile–butadiene–styrene (ABS) material. The results revealed that the highest in-plane and edgewise flexural moduli were obtained when printing was performed at 0 ° raster angle. In comparison, the lowest values were obtained when the printing was executed with a 90 ° raster angle. Regarding the infill pattern, the tri-hexagon pattern showed the largest in-plane modulus, and the quarter-cubic pattern exhibited the greatest edgewise flexural modulus. However, considering both the modulus and load carrying capacity, the quarter-cubic pattern showed satisfactory performance in both planes. Furthermore, scanning electron microscopy was used to investigate the failure modes, i.e., raster rupture, delamination of successive layers and void formation. The failure occurred either due to one or a combination of these modes

Performance Analysis of Enhanced 3D Printed Polymer Molds for Metal Injection Molding Process

Conventionally, molds for metal injection molding (MIM) process are fabricated using metallic materials using conventional machining processes. Machined metal molds are resilient and therefore could be suitable for mass production of MIM parts. However, with the process of mass production leading to permanent hard tooling, the design is subjected to rigorous testing and iteration before finalization. During design analysis and the iteration process, the demand for MIM parts (part demand) is at low-volume. Therefore, machined metal molds could be costly and time consuming for low volume and customized end-use products. 3D printed molds could be a suitable choice for MIM production for such applications. The present study compares the performance of Fused Deposition Modelling (FDM) 3D printing (3DP) process made polymer molds with an aluminum mold for potential use in MIM process. It was observed that 3DP molds could successfully be used for a limited number of MIM cycles

Thermal Conductivity Augmentation of Epoxy Injection Moulds for Cooling Time Reduction

Polymer injection moulds are generally manufactured with tool steels which give reliable functioning of moulds with long service life. Manufacturing of injection moulds in steel is a lengthy process due to the strength and hardness. If the injection mould is required quickly for a short prototype or production run, one of the good choices is to use Aluminum filled epoxy material, which can give a mould in a very short time using Rapid Tooling (RT) techniques, as compared to a machined tool. Aluminum-filled epoxy tools work best for relatively simple shapes. The benefits of fabricating injection moulds with epoxy resins includes time saving, ability to set at room temperature and ease of machining. But a major drawback of epoxy material is that the cooling time for epoxy injection moulds are still relatively long due to the poor thermal conductivity of epoxy. This paper reports investigation of an innovative idea for enhancing the thermal conductivity for epoxy moulds. The basic concept behind the idea was to embed high thermal conductive metal insert within the mould between the cavity and the cooling channel. This technique will increase the effective thermal conductivity of the epoxy mould, leading to reduction in cooling time for the injection moulded polymer part. By substituting part of the epoxy with low-cost aluminum, a cost advantage is also to be derived, besides increased mould strength. Experimental analysis done in the current study also verified that mould with embedded metal insert has considerable shorter cooling time.Published versio

Rapid Tooling For Powder Injection Moulding Process

Injection Mould tools for various applications like polymer, wax and powder injection moulding (PIM) processes are usually manufactured with metallic materials like aluminum and tool steel which give durability and efficient functioning of moulds and good service life. Manufacturing of injection moulds is a time consuming process due to the geometric complexity of mould and strength of metallic materials. For a short prototype or pre-series run, the injection mould may be needed in a shorter time and less expenditure. For these applications, 3D printing (3DP) and Rapid Tooling (RT) technologies could be a rapid solution for fast and feasible mould development compared to a machined tool. This current study focuses on the development of powder injection moulds using 3DP with Acrylonitrile Butadiene Styrene (ABS) material. ABS 3D printed moulds can be used for design verification and a short production run for PIM process. The current study indicated that the 3D printed injection moulds development was practically fast and serve the purpose of design verification for PIM parts. Some part defects and breaking was observed due to ejection issues. Secondary RT techniques could be applied for fabricating mould that could produce parts for the production phase.Published versio

Influence of Tool Material, Tool Geometry, Process Parameters, Stacking Sequence, and Heat Sink on Producing Sound Al/Cu Lap Joints through Friction Stir Welding

The present study was focused on establishing guidelines for successful friction stir welding of Al alloys and Cu lap joints. Detailed investigations in respect to tool geometry, tool material, work-piece material, welding parameters, stacking sequence, and heat sink were carried out. The soundness of welded joints was tested through microscopic analysis and the lap shear test. The results revealed that the tungsten carbide (WC) tool with square-pin produced sound joints in terms of minimized defects and high strength. Further, the use of heat sink proved as an important pre-requisite when the stacking sequence was inversed (i.e., Cu-Al), and this stacking configuration in comparison with the Al-Cu stacking yielded weaker joints. The influence of the tool welding speed (F, mm/min) was found to depend upon the tool material. A range of tool welding speed (23.5–37.5 mm/min) worked well for the WC tool. However, only two values of welding speed (30 mm/min and 37 mm/min) were observed to be conducive when the tool material was HSCo (high-speed cobalt)-steel. Finally, it was concluded to employ the WC tool with square-pin, a welding speed of 30 mm/min, the rotational speed (S, rpm) of 1500 mm/min, and Al-Cu stacking sequence to successfully process the Al/Cu lap joints

Enhanced polymer rapid tooling for metal injection moulding process

Presently, mold material for metal injection molding (MIM) process is metal and are made through machining. However, machining could be time consuming, costly and skill intensive process to accurately process the mold. Moreover, for the demands when MIM part requirements are in low volume and features are customized, the machined mold is rendered useless once the part demands have been met. 3D printing could be a quick process to make molds from polymers for the customized and low volume MIM cycles. While this 3D printed mold may not be sustainable for mass production, yet they could potentially be viable for small MIM cycles like prototype manufacturing. The present study investigates the performance of polymer molds made form fused deposition modeling (FDM) process for their potential use as direct Rapid Tooling (RT) in MIM process. It was concluded that 3D printed polymer molds could be successfully applied in MIM process for prototype manufacturing and low volume demands of end-use parts.Published versio