Papers by Keyword: Weld Line

Abstract: This article deals with the influence of the melt temperature on weld line strength in injection-molded plastic parts. A special mold was created for this investigation to make specimens with a central weld line. The experimental material was polypropylene Sabic PP 90910. Its stress at break is around 16 MPa and its melting temperature is between 200°C and 260°C. In general, the presence of weld lines has a negative impact on mechanical properties. This investigation showed that the strength depends on the melt temperature (160–260°C in this case). Strength was measured using mechanical testing. It was found to increase with the melt temperature, up to 210°C. Above 210°C, degradation of the plastic led to decreasing strengths. A melt temperature range of 190–210°C is therefore optimal for this application. Shear forces and friction were found to play a great role, as they raise the melt temperature during molding. This was confirmed by mold-flow analysis. The melt temperature during molding was up to 18% higher than the initial melt temperature. This investigation has important consequences for the plastic industry. It is relevant to evaluations of the polymer matrix strength in composite materials and the strength of 3D printed parts with multiple weld lines.

Abstract: The welding line characteristics of injection molded parts with various venting systems were researched in this paper under the tensile tests of ISO 527. A mold was designed in such a way that specimens with and without a venting system can be developed separately. Both PA66 and PA66 + 30%GF materials were used in this study. Without the venting system, results showed that the weld line strength was only increased when the injection pressure varied from 0.9 MPa to 1.1 MPa, if continuously increasing the injection pressure, the weld line strength will get the negative effect. When the venting system was used, the decrease of the weld line strength with the high injection pressure was eliminated. With the use of 1.3 MPa injection pressure, when increasing the venting gap from 0.02 mm to 0.10 mm, the weld line strength varied from 10.45 MPa to 11.4 MPa with the PA66 material and from 30.8 MPa to 32.95 MPa with the PA66 + 30%GF material. With the case of without venting system, the air trap at the microstructure of weld lines was clearly observed. This trouble was removed when the venting gap value of 0.10 mm was used.

Abstract: Through injection molding simulation software and examples of injection,This paper analyzes the causes of the weld line when injection molding products, the impact on the quality of products, analysis of the injection mold gate location selection problems and defects produced by principle, think weld line has a great influence on the quality of injection molding, on this basis, put forward in view of the weld line, the influence of the mold gate location selection method in the practical work of is: reasonable choose the location of the gate, to control the degree of weld line, as far as possible to reduce the number of the weld line, or make them produce not important position in the mold. Etc.

Abstract: The topic of this research work was to demonstrate the feasibility of a 3D-MID concept using injection molding technique and investigate the effects of two weld line types on the structure and mechanical properties such as tensile, flexural strength and morphology. In order to obtain more understanding of the bonds between polymer and metals, two different polymer bases of polyphthalamide (PPA) with the same type and amount of filler content were produced by injection molding at the different processing conditions. A mold was designed in such a way that weld and meld line can be produced with different angles by changing as insert inside of the mold. The mechanical properties such as stiffness, tensile strength and flexural strength were determined in tensile and flexural tests, respectively. The results showed in line with the expectation of high reduction on mechanical properties in area where weld/meld lines occurred. The result of tensile test was clearly seen that weld and meld line showed a considerable influence on mechanical properties. The reduction in tensile strength was approximately 58% according to weld line types, whereas in flexural strength was approximately 62%. On the other hand, the effect of the injection times and mold temperatures on the tensile strength were marginal.

Abstract: Designed the weld line quantization algorithm based on the moldflow secondary development of technology, obtained the numerical experimental data of weld line with this. Analyzed of the impact of the relationship between the process parameters and weld line, and optimized the process parameters by orthogonal experimental design. These provided an important basis for the forming process design.

Abstract: An automobile bumper is a large scale thin-wall plastic part. It is difficult for the weld lines of product to be removed by conventional injection method. Five valve gates in sequential injection have been used to control successfully weld lines to the border, but the warp degree of the product is too large. Through grey theory the packing pressure and time of valves opening and closing have been optimized. The grey relational degree have been calculated, the optimal process parameters group have been obtained by variance analysis. The result has been verified successfully in Moldflow software, the warp degree of product has been decreased greatly and satisfied the requirement of industry production. The injection method can be applied in actual production and increase corporate profits.

Abstract: This document describes the principles of the weld line’s generation, formation and points out that the impacts of the product mix, mold structure to the weld line. And a new method of improving products’ weld line was proposed, it adds the plastic materials to the plastic product and loads the insert to the mold to improve the weld line, actually, weld line’s quality was determined not only by adding rubers, loading inserts, but also by other complex methods; However, the approach that was proposed by this paper could solve the weld line’s quality easier than other methods, for it can greatly remove the weld line of the product’s appearance and do not need complicated process parameters. Then the Moldflow software was applied to stimulate the filling process and As a result, the weld line was greatly improved.

Abstract: Plastic moulded parts should have good mechanical properties and free from defects. Tensile behaviour of plastics plays an important role in defining the quality of injection-moulded products. In this study, numerical simulation (Cadmould) was employed to investigate the influence of gate sizes as well as the injection moulding parameters towards the occurrences of weld lines at Acrylonitrile Butadiene Styrene (ABS) specimens. This research begins from the simulation, fabrication of mould, practical injection process and tensile test. The double gates mould was used to present the weld line defects. The result shows that the smaller gate size produces less weld line in plastic parts, which was verified through simulation process. The optimal parameter setting that produced good tensile strength specimens was also validated experimentally in this research

Abstract: In this article, some common defects, which are caused by material properties, and the mechanism of the defects occur are introduced. Author introduces how these defects are treated in conventional process, meanwhile, points out the disadvantages of the process. For the disadvantages, several special processes are introduced, including gas-assisted injection molding, rapid variotherm injection molding and hot runner technology, and their mechanism and advantages.

Abstract: As well known, the weld line defect in injection molding process results detrimental to mechanical properties and surface quality. However, the electrical conductivity of the injection molded part is influenced as well. In this study, in order to reveal the mechanism of the weld line affecting the electrical conductivity of injection molding parts, the conductive polymer composites with various carbon nanofibers filling contents were compounded. Those composites were formed as the tensile samples with and without weld line defects by injection molding process. According to the electrical resistance measurements for the samples, it can be found that at relative low filling content of 10wt%, the weld line contributes to increase the electrical conductivity of the injection molding parts due to its effect on nanofibers’ orientation. However, when the filling content is higher than 20wt%, this effect is not significant any more.