The formation of weld lines and their location along the flow path is a well-studied phenomenon in conventional injection molding; however, only a few papers are devoted to micro-injection molding [11,13,14,15,16]. Materials Science. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. Here we are looking at most common part defect that can come from injection molding called weld line. It has larger cross-sectional regions that allow sufficient molten plastic flow into the cavity. Polymer Engineering and Science (2005) There are more references available in the full text version of this article. on conventional reciprocating screw injection molding machines using molding practices standard for filled engineering thermoplastics . To resolve this issue, rapid heat cycle molding (RHCM) has attracted attention as an innovative PIM technology. The weld-lines are undesirable from both aesthetic and functional points of view and their effect is different for varied materials, process conditions, loadings, forms. 22 shows how the weld lines are formed when the melt splits around core pins during the injection molding process. Weld lines in injection molding are frequently unavoidable. <1> As illustrated in Figure 4, the existence of. Injection molding is a manufacturing process that involves injecting molten plastic into a mold cavity to create a specific shape or design. Weld or knit lines result wherever two or more polymer flow fronts unite. 7 of the reference. 2012. Venting at Weld Lines. Mechanical properties of the weld line defect in micro injection molding for various nano filled polypropylene composites. In. Thus, a right gate design raises polymer temperature to prevent the formation of weld lines and flow marks. They can affect the strength and. Weld lines are the result of fundamental physical effects taking place inside of the mold tool cavity, they are common imperfection to be found in most plastic injection molded parts. Ada berbagai penyebab mengapa weld line bisa muncul pada permukaan produk plastik. The most simple design modification for eliminating the weakening effect of a weld line is to increase the wall thickness in the weld line zone (Figure 4). 1. The parting line in injection molding is which one of the following: (a) the lines formed where polymer melt meets after flowing around a core in the mold, (b) the narrow gate sections where the parts are separated from the runner, (c) where the clamping unit is joined to the injection unit in the molding machine, or (d) where the two mold halves come. Increase the injection speed to reduce the amount of cooling happening in the mold. Bubbles are caused by melting flow fronts colliding in a mold cavity. Weld Line Phenomenon: Surface defect in which the weld, or the part where the flows of melted plastic meet inside the mold, shows up on the surface as a groove or pattern. The strength of the weld-line area can be increased by optimizing injection molding process parameters like melt temperature, injection speed, packing pressure, changing gate type and location, etc. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. th e use of design of e xperiment techniq ue. Plastic Rapid Injection Molding is popular not only in low volume manufacturing but also in large quantities molding, it is the most common way to manufacture plastic parts. Figure 1 below shows the development of a weld line. Redesign the mold to prevent the weld line. Weld lines are among the most critical structural defects in parts made by the injection molding of fiber-reinforced thermoplastics, explained Sirmax in a press release. To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. Key words: weld line strength, thermoplastic composites, injection molding, wall thickness, skin and core layers Department of Materials Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900, Thailand. Meld and knit lines are actually both different types of weld lines. 226-233. Shaofei Jiang. Weld line location. Sink marks are a common type of injection molding defect. There are several possible causes that need to be investigated to troubleshoot weld lines in injection molding. The weld-lines are undesirable from both aesthetic and functional points of view and their effect is different for. 1. The gate location should enable the two flow fronts to merge easily and continue to flow beyond the weld line. Poor weld line Ⅰ. Weld lines in injection molding occur when two flow fronts meet and create a visible line on the surface of the molded part. Known also as knit lines and. Gate position in injection mold. Facebook. We have various types and models available. A weld line refers to a line, notch or color change that is created on the molded part caused by the convergence of two separate flows of molten plastic. A knit line in a plastic injection-molded part is created when two separate plastic flows meet within the mold and "resolidify" along their interface. Int J Adv Manuf Technol 52:131–141. Powder injection molding comprises several processing steps, and defects may occur in each step if care is not taken. Weld lines are formed when two melt fronts come in contact with each other. The. Possible causes: Low temperature or fluidity of melted plastic during injection molding. As these flow fronts come together on the. 5. In injection molded parts, there are 2 types of weld lines: The first type of weld mark is called cold-melt joints and is formed when the melt front enters the cavity with different gates. As a result this weld line will be a weak point in this part. Miron MC, Major Z, Adachi T. injection molding. * Corresponding author, e-mail: fengsjpc@ku. In this way critical areas of the interface in regard to the lack of interdiffusion and the inappropriate molecular orientation were found to be placed near. In. Weld line defects are a common part defect that occurs when the injected plastic flows around a solid piece of the mold and does not knit back together. But add 30% glass and weld-line strength retention drops to only 34% as high as the compound with no weld. They are unavoidable even for moderate complex products. 666 Azieatul Azrin Dzulkipli and M. Valve gates also make weld lines less of. Weld lines are a common defect generated in injection molding, which apparently affects the performance of final products, but the available reports on carbon fiber-reinforced thermoplastics are. 2. Reposition gates and runners to allow resin to flow around the obstruction from a. Consultant @ Effinno Technologies, BSME, MBA - Bridge between Plastics Injection Molding Knowledge and Practice. Our injection molding company is explaining what these imperfections are, why they can compromise. Description Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. 9 – Over Packing. Int J Adv Manuf Technol 52:131–141. Weld lines can appear on the components when the molten plastics meet each other as they are flowing from two different parts of the mold. Additionally, you can get our free Design Cube, which will provide a physical aid to help understand how knit lines form as well as other injection molding design considerations. 2. During the plastic injection molding process, one of the biggest challenges is. For this purpose, the width of the weld line calculated by Sigmasoft is. This reduced thickness of the frozen skin further enhances the visual appeal of the. Injection molding plate for mode I testing geometry. as warpage, shrinkage and weld line of the plastic parts. The microstructure of weld lines is clearly observed from the micrographs. CrossRef View in Scopus Google Scholar [17] G. 1. Flash. Adjust Injection Molding Parameters: Optimizing injection speed, pressure, and temperature can help ensure better melt flow and reduce the likelihood of weld line formation. Polym Eng Sci 45(7):1021–1030. The present work focuses on studying the effect of packing pressure on strength of stagnation weld-line. C. Fellahi et al. Criens, R. The three parameters affecting operation were called injection pressure, injection time, and packing pressure which influence the quality of weld line. In this mold, a visualization design and a rapid heating/cooling system were integrated, and specimens with different cross section. Weld line, 5. Wu CH, Liang WJ (2005) Effects of geometry and injection-molding parameters on weld-line strength. Weld-line is a weak area which reduces the strength of the part locally. in the cavity of the injection mold. Controlling injection molding weld lines with good design and process control. Usually it’s a straight line, and often to be found radiating away from a hole, inclusion or other such part feature. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. We'll show you how. Weld-line is a weak area. Three terms that often get mixed up are weld, meld, and knit lines. Avoid knit lines when designing a molded part to improve cosmetic appearance and functionality. G. Lesson 6: Meld and Weld Lines (Processing) When plastic flows into an injection mold, the internal flow pattern depends on the part design, mold design, and processing factors. 2-1. The weld-lines are undesirable from both aesthetic and functional points of view and their effect is different for varied materials, process conditions, loadings, forms of weld-line, etc. 2. When an external load is applied to a weld line region, the part’s potential for mechanical failure is increased. 2011; 509 (2):226–233. Keywords: Flow behavior , Injection molding , Particle tracking , Visualization , Weld-line Article MetricsSimulations and experiments were conducted with gas temperatures of 200–400 °C to investigate the impact of external gas-assisted mold temperature control (Ex-GMTC) on the quality of weld line of molding products. A weld line is a mark left on the surface of a plastic injected molded part. (2011) and Fig. They can affect the strength and appearance of the part, depending on the temperature, pressure, speed, and mold design of the injection molding process. Microsyst Technol, 14 (6) (2008), pp. Weld Lines and Fibers There are two basic types of weld lines: the stagnant and the flowing [1]. Adjust the position of the gate and include a venting slot. Try to gradually raise the mold temperature and barrel temperature. The following are the reasons. + Move gate (to where it is not visible). In narrow fields, a limited amount of molten liquid can solidify and block the flow. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. Weld lines can be caused by many reasons, which covers the various aspects of mold, process, raw materials and product design, etc. Participating in DFM and mold flow analysis is a good way to achieve this. In an injection molding process, a weld-line forms when two flow fronts meet each other. The design of the mold, as well as the part being molded, has a significant impact on the success of the process. “I realized weld -line problems are a very common issue for injection molded parts,” Nicholson told Plastics Technology. A meld line occurs when two moving melt fronts converge and flow parallel to each other. and Mosle, H. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. That’s the air escaping out of the nozzle until the hose is full of pressurized water. Weld line additionally called as knit line, is a defect that occurs when the injected plastic meets within a. Effects of fillers and/or reinforcements on weld-line strength of nylon 6/6. Flash. Clamping Unit. The cracking was always located in the weld/knit line and therefore caused by weakness in the bonding of the plastic at. The thermo. Since weldline in plastic injection molding (PIM) has an influence on not only the strength but also the surface appearance of a plastic product, it is preferable to reduce it as much as possible for high product quality. [ 18 - 21 ] In addition, the effects of flow behavior of the polymer melt due to the optimal process parameters for the minimization of weld-line effects are an important consideration. This gives a clue as to. The next type of injection molding defect is ‘Weld Lines’. A visual mold with variotherm system for weld line study in micro injection molding. 2-1. What causes them? The primary cause is weak bondage between two or more flow fronts. 6. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. Weld line reduction is one of the major concerns in plastic injection molding (PIM) that results in high surface appearance and high strength of a plastic product. These flow fronts occur when the molten plastic material encounters obstacles, such as inserts, ribs, or other features within the mold cavity. 2. Munich, Germany: Carl Hanser Verlag, 1994. The following are the conclusion drawn from the present research: 1. Weld Lines are formed when two or more molten polymer flows meet during the injection molding process. A family of short carbon fiber-reinforced thermoplastic (CFRTP) compounds specifically formulated for injection molding is being used to extend the capabilities of thermoplastic composites in a variety of part sizes and complexities. This defect occurs due to the temperature and pressure not being high enough, causing premature solidification. In addition, its tensile strength and stiffness will be sharply decreased. Melt temperature is 250°C, mold temperature is 110°C. 13 shows the best gate location for which the weld lines . injection molded pipe-fittings with and without weld line. If the plasticizing ability of the plastics injection molding machine is insufficient, the plastic. com1. Tekanan. Five industry pros with more than 200 years of combined molding experience provide step-by-step best practices on mounting a mold in a horizontal injection molding machine. When two or more strands of molten plastics meet in the mold, a weld. . You will have to confirm them before tooling. This can allow the. In the heating step, the heatingOverview of the injection molding process. Silver Streak. Proper venting is also required to ensure good weld-line quality. Its design significantly impacts the final product’s appearance, strength, and functionality, making it crucial for manufacturers to understand its intricacies and variations thoroughly. In the present study, Moldflow® software is applied to simulate the injection molding of automobile instrument light guide bracket and optimize the injection gate position. 3. Set up the process overflow and use it as the place where the weld line is generated, and then cut off and remove it after forming. However, even with advanced technologies and precise control, the process is not without its challenges. Physics. Injection molding is a highly versatile manufacturing process used to produce a wide range of plastic products with precision and efficiency. Usually it’s a straight line, and often to be found radiating away from a hole, inclusion or other such part feature. ac. Weld line and warping are two critical defects for injection-moulded part. Meld and knit lines are actually both different types of weld lines. In this regard, the plasticizing ability of the plastic injection moulding machine should be checked. Weld lines can be caused by material flowing around holes or inserts in the part, multiple injection gates or variable wall thickness where hesitation or "race tracking" can occur. 5. Mold flow analysis can predict the location of weld lines. The thermo-rheological findings were used to investigate the sources of weld line weakness. Consequently, it causes viscous dissipation which leads to the generation of heat. Short Shot Short Shot adalah suatu kondisi dimana, plastik leleh yang akan diinjeksikan kedalam cavity tidak mencapai kapasitas yang ideal atau sesuai settingan mesin. Weld lines are injection molding defects that can be mitigated by a number of tactics that depend on your part design. Complexities in the design and intricate pathways in the mold can also create flash in injection molded parts. Three terms that often get mixed up in the plastic injection molding industry are weld, meld, and knit lines. Figure 2. 010 0. Weld Line Factors for Thermoplastics. Flow lines are off-color lines, streaks, and other patterns that appear on the surface of a part. reinforcement type and amount in nylon 6/6. The formation of weld line in the injection molding method is caused by the product and mold design that is one of the common mistakes. Procedia Mater Sci 2014; 3: 2048–2053. Except for a few very simple injection molded parts, they occur on most injection molded parts (typically in the form of a line or V-groove), especially large complex items that require use of multi-gate molds and inserts. Weld lines are a common imperfection to be found in most plastic injected molded parts. Injection Molding Glossary; Weld Lines; Weld Lines. These are preferred over weld lines as they will normally result in improved cosmetics and structure. In the RHCM, the mold temperature profile plays a crucial. In this study, the effects of injection temperature, injection pressure, and fiber content on the mechanical properties of weld lines were studied for carbon fiber-reinforced nylon. With tighter heat controls, you can keep the material at the proper temperature to make sure the plastic keeps flowing and fills the mold cavity completely. 1. An injection molding gate is a critical component in mold design, acting as the passage through which molten plastic travels from the runners into the mold cavity. Avoid knit lines when designing a molded part to improve cosmetic appearance and functionality. Weld lines are formed when there is an inability of two or more flow fronts to ‘knit’ or ‘weld,’ together during the molding process. Slow down injection speed. Machine Shot Capacity – The maximum volume of resin that can be injected in a single stroke of the injection machine. 4 at different time steps (legend scale is volume fraction of. สาเหตุการเกิด weld line คือเมื่อการไหลของพลาสติกมาประสานกันนะจุดใดจุดหนึ่งและจุดนั้นเกิดความแตกต่างของอุณหภูมิในสองทิศทางการไหลจะทำให้เกิด. Compd. Polymers 2023, 15, 2440 3 of 21. When molten plastic flows, it forms a smooth continuous flow until it meets an obstruction. The impact behavior of weld-lines in injection molding. 2. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. are very minimum. This defect occurs due to the temperature and pressure not being high enough, causing premature solidification. Weld lines are a kind of Achilles heel of plastics. Numerical results show that weld lines can be predicted accurately, and the formation and evolution processes of weld line can be shown more clearly by co-injection molding technique. Cited by (41) Effect of mould surface roughness adjustments to increase the flow path length in the injection moulding process. The type of resin used during injection molding plays a large role in whether or not a knit line will be present. Weld lines may appear like seams or scratches, but that is not what they are. Weld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of injection‐molded parts. 005 0. 2 mm to 1. Neat polypropylene retains nearly 90% of its strength on a properly designed and molded weld line. The effects of filling time, packing time, packing pressure, melt temperature, and mold temperature on the ultimate tensile strength (UTS) and the elongation value of the weld. poor flow fronts that are too cold, this can also lead to a deterioration in the mechanical properties. Because of the ever-increasing requirements for parts performance, lots of researchers have perf. Injection speed is too low. Weld lines occur when melt flow fronts meet during the injection molding of plastic parts. examined the relationship between the structural and mechanical qualities in HDPE/PA6 mixture which is molded with weld line and without weld line in plastic injections [6]. This remains as a challenge for control engineers. The weld-lines are undesirable from both aesthetic and functional points of view and their effect is different for varied materials, process conditions, loadings, forms of weld-line, etc. During injection moulding, a weld-line occurs when two or more flow fronts collide in the hollow cavity. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. A simulation process was conducted to determine the recommended setting of injection moulding parameters and the range of the variable. Meld and knit lines are actually both different types of weld lines. Weld lines are a common defect generated in injection molding, which apparently affects the performance of final products, but the available reports on carbon fiber. From: Polylactic Acid (Second Edition), 2019. [ 18 - 21 ] In addition, the effects. – Use generous and even. S. The need to minimize fiber breakage, plus the higher viscosity of materials with. 1. 32–24. The weld line’s strength is reduced when. Weld lines can. An evaluation model based on artificial neural network method. Weld lines appear on the surface of a molded part where the molten material converges after splitting off into two or more directions in a mold. Weld lines in injection molding are formed when two or more flow fronts of molten plastic material meet and merge during the molding process. To position weld-line to avoid critical areas for the sake of aesthetics or mechanical strength is the key to the success of bi-injection molding. Reduce the amount of release agents. Fracture behavior of weld lines in injection molded components loaded under real operating conditions. The weld line in injection molding is created when two melt streams connect, as shown in Figure 1. For multiple gate and complex part. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. This weld line can act as a weak spot in the material. Rapid heat and cool injection molding is an example of a measure to prevent the generation of weld lines. Effects of mold temperature and pressure on shrinkage 0. In an injection molding process, a weld-line forms when two flow fronts meet each other. Ideally, the resin flow will split into two flow fronts to pass around the obstruction and then recombine into a single flow front. Increase the injection speed. This will produce parts with aExperimental results show that the weld-line strength from a standard test is not applicable in microinjection molding. This reduced thickness of the frozen skin further enhances the visual appeal of the. The weld lines that occur in injection mouldings are critical areas on which depends on the strength of the mouldings. <Mold> Increase (or decrease) the size of the runners and gates. A weld or meld line is a weakness or visible flaw created when two or more flow paths meet during the filling process. Clamping unit berfungsi untuk memegang dan mengatur gerakan mold unit, serta gerakan ejector saat melepas benda dari molding unit, pada clamping unit lah kita bisa mengatur berapa panjang gerakan molding saat dibuka dan seberapa panjang ejector harus bergerak. 025 100 120 140 160 180 200 220 240 Mold Temperature (F) LDPE PPAbstract. In the end, the total amount of time that running a complete Taguchi DOE (L18) to occupy an injection. 3. These lines can weaken the strength of the part, and they can also be unsightly. Crack growth behavior. For thick-walled parts, slow injection rates result in more uniform polymer distribution . Adjust the design for the flow pattern to be a single source flow. Xie L. M. And how to use the 3 modes of the sequential controller correctly to prevent burn marks, weld line, short shot, and other part defects in injection molding. In this blog post, we will explore the causes of weld lines in. 2. Weld lines are one of the typical quality issues of injection molded parts. If the different flow fronts have cooled. A good weld typically occurs when the melt temperature where the weld line is formed is no more than 20°C below the injection temperature. The formation of weld line in the injection molding method is caused by the product and mold design that is one of the common mistakes. Three terms that often get mixed up in injection molding are weld, meld and knit lines. Visualization analysis of flow behavior during weld-line formation in injection molding process. Kagitci YC, Tarakcioglu N (2015) The effect of weld line on tensile strength in a polymer composite part. In this paper, a weld line computer determination method based on filling simulation with surface model is proposed, from which the positions and lengths of the weld lines can be predicted. Remedies: Reduce packing and fill rates by adjusting until the part is properly filled with minimum stresses. In recent years new methods for quality prediction and optimization of the injection molding process have been proposed and applied. Plastic Injection Molding Process. Some of the approaches include the application of machine learning methods (Chen 2008; Manjunath and Krishna 2012; Kuo et al. To respond to poor plasticization and uneven melt temperature, the molding cycle can be extended to make. A weld line is often unavoidable. Weld lines have been one of the common defects puzzling the injection molding industry. Weld-line yield strength, yield strain, and failure strain of talc-filled polypropylene increase with increasing melt temperature and increasing hold pressure. Change the gate locations. % glass fibers – PA6 Aramid SV 30-1ETM (figure 1b). A weld line refers to a line, notch or color change that is created on the molded part caused by the convergence of two separate flows of molten plastic. This failure causes the product to be damaged during use. So today we are going to take a look at the five most common defects in injection molding and their solutions. In recent years, researchers have. A knit line in a plastic injection-molded part is created when two separate plastic flows meet within the mold and "resolidify" along their interface. Boost time too long Shorten boost time, lower boost pressure, or move transfer to an earlier position . Weld lines appear as a result of the flow of molten plastic during the injection molding process. In this work, the weldline strength of injection molded short-glass-fiber reinforced polycarbonate was derived by an analytical method of modified rule-of-mixtures as a function of the area fraction between skin and core layers. The weld lines in injection moulded parts arise as a result of the collision of two fronts of the flowing material, which fills the mould cavity and are sometimes unavoidable. Weld lines are a common defect generated in injection molding, which apparently affects the performance of final products, but the available reports on carbon fiber-reinforced thermoplastics are still rather few. Problem: Weld lines are formed when plastic resin is forced around an obstruction in a mold tool and reforms on the side opposite the gate. Procedia Mater Sci 2014; 3: 2048–2053. 2. Conclusion The formation of weld lines in micro injection molding of plastic depends on different parameters such as melt temperature, injection pressure and fabrication method. Penyebab Weld Line. Weld lines are also known as knit lines. In this case the two flow fronts will meet and there will be very little molecular orientation across the weld. Recently hired at plastic injection molding simulation software provider Moldex3D, Nicholson was spurred to undertake the research study following a conversation with a customer experiencing weld-line woes. of micro injection molding process simulation by technology update and progress. In manufacturing, the Weld line or Knit line or Meld line is the line where two flow fronts meet when there is the inability of two or more flow fronts to "knit" together, or "weld", during the molding process. This type of injection molding resolves any trouble caused by undesired welding lines. 18/06/2021. This is expected to achieve maximum results while the pressure holding effect will also increase. This consequently produces weld lines. Instead, a line that looks like a seam forms. Unless you are manufacturing an extremely simple part with one gate and a unidirectional flow front, your part will have weld lines. 4If the injection gate is not properly designed, it can cause the formation of defects like sink-mark, warpage, short shot, weld-line, air traps, and other faults [15]. Part design features may cause a material flow to split and rejoin as it flows around design features in a mold. Plastic part design for injection molding – An introduction. Flow Lines. T. This thermal field was transferred to an injection molding flow solver to compare simulations and experimental results from the high speed video, both with and without the effect of induction heating. <Materials> Pre-dry thoroughly. If the different flow fronts have cooled. Although this phenomenon occurs in almost all the commercially important polymer. “I realized weld -line problems are a very common issue for injection molded parts,” Nicholson told Plastics Technology. (2) Causes & Countermeasures (See the table below) *Note: Flash also tends to occur when the injection pressure/speed are too high, but molding time is too long and mold temperature is too low. une, 13: 15. They decrease the. Stagnant weld lines are formed when melt streams meet head-on. Try to gradually raise the mold temperature and barrel temperature. ing weld line properties of injection molded thermo-. Thereby creating localized pressure within the mold. Emerging Materials Research. As the weld line can significantly lower the mechanical strength of µIM parts, it is relevant to clarify the position of weld. Steven. This occurs wherever there is a hole, notch, or any other feature on a part which divides the flow of plastic into 2 separate “flow fronts. These lines are formed when two or more flowing molten plastic streams meet and fuse together, creating a visible line on the surface of the molded part. In this study, one injection mold. Weld lines. Gate Placement: Properly positioning the gate can direct the melt flow to minimize weld lines or relocate the weld line to non-visible areas of the part. The optimum injection molding parameters to manufacture the product was determined by . Meld lines are formed when two separate flow fronts meets. In this lesson we will focus on the meld and weld lines. Plast. The effects of fiber concentration has been studied in detail. 10 in Nguyen-Chung et al. Although they often cannot be avoided it’s possible to minimize their cosmetic effects to an acceptable degree through careful product design and. This study focuses on the effect of melt temperature on. Edge Gates. 48 applied high-frequency induction heating to eliminate weld lines in an injection-molded plastic part, and experimental observation indicated that weld depth was reduced from 2. The thermo-rheological findings were used to investigate the sources of weld line weakness. This customary mark is caused by differential rates of cooling in the resin where. In injection molding of thermosoftening plastics, an important aspect having a bearing on the quality of articles is the appearance of weld lines that are formed when there are inserts, barriers, molding signs, reinforcements, etc. It is important to investigate the weld line because the weld line area can induce potential failure of structural application. The flow disruptor is a small insert introduced inside the injection molding cavity, in the weld line area, and its objective is to mix the melt and disrupt fountain flow in order to blur and. They. Weld lines can be caused by several different problems: Low temperature of injection moulding machine barrel. Fig. Simulation of polymer molding filling process with an adaptive weld line capturing algorithm. Munich, Germany: Carl Hanser Verlag, 1994. Remedies: Raise the temperature of the mold or molten plastic. Article Google Scholar Deng YM, Zheng D, Lu XJ (2008) Injection moulding optimization of multi-class design variables using a PSO algorithm. The optimal process condition is very likely to appear in this second part's fine-tune group. Weld line is formed when two different melt flows converge, as illustrated in Fig.