This weld line can act as a weak spot in the material. In this study, we apply the technique of SAW to explore the acoustic properties near injection-weld lines by comparing the velocity of. These weld lines occur usually around holes or at the material flow joint area in the injeciton molded part, some welding lins is very small, specially if. Flashes, 3. The weld line in injection molding is created when two melt streams connect, as shown in Figure 1. To explore the formation of. In this case the two flow fronts will meet and there will be very little molecular orientation across the weld. • Reduce runner dimensions and maintain the same flow rate. Therefore, the investigation on the developing process of weld line would be a significant issue for improving the quality of micro injection molded parts. If the different flow fronts have cooled. Fig. reinforcement type and amount in nylon 6/6. One solution is to prevent the weld lines from forming in regions that are. 2. Its design significantly impacts the final product’s appearance, strength, and functionality, making it crucial for manufacturers to understand its intricacies and variations thoroughly. Weld-line is a weak area which reduces the strength of the part locally. This study examines the impact of injection parameters on the weld line strength of the polyamide 6 and 30% fiberglass (PA6 + 30% FG) composite samples. Molding Equipment. (1) Flash: Extra plastic material in the shape of films or burrs, which appears on the parting surface, around the runner or in the insert crevice. The injection pressure is too lowEffect of the processing conditions on the variations of the bulk temperature, T b , at the end of mold filling at the two locations: in (left) and away (right) from the weld-line (T w , T inj. Vertical Plastic Injection Molding Machine [10, 11, 12] 2. Here are some reasons why design is important for injection molding. poor flow fronts that are too cold, this can also lead to a deterioration in the mechanical properties. <Mold> Increase (or decrease) the size of the runners and gates. The parts are molded flat and are slightly stressed once installed in an arced position, but not excessively. Poor weld line Ⅰ. Gate blush, 4. 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. 3 cc/sec, the weld lines are no longer perceivable above 130 C. , a post that forms a hole) and then rejoins, or when polymer melt fronts meet, from multiple injection points. The effects of these two injection molding process parameters are explained in terms of their influence on the skin-core morphology observed on the fracture surfaces in the weld zone. If there’s too much mold release, you may require a higher pressure to push it through the machine. These potential causes include: Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. Weld Line defect analysis, the most common of many defects in injection moulding products. Therefore, the length of flowing weld lines must be additionally defined. A knit line, also called a weld line, occurs when the liquid plastic moves through the mold and hits more melted plastic and they don’t flow or fuse together. Weld-line yield strength, yield strain, and failure strain of talc-filled polypropylene increase with increasing melt temperature and increasing hold pressure. We have various types and models available. It is a zone with reduced mechanical properties negatively influencing on the molding behavior in exploitation. 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. Weld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of injection‐molded parts. • Move injection locations to make flow fronts meet more obliquely, turning the weld line into a meld line. Raising the mold temperature will keep the material molten longer, resulting in stronger weld lines and even elimination of weld lines. (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. 2011; 509 (2):226–233. Weld Lines. The thermo. Int J Adv Manuf Technol 52:131–141. 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. Shaofei Jiang. One of the things that can compromise an injection molded part is a weld line, also called a knit line. This study focus on the. 2004; To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. The result is part defects such as weld lines, poor finish, or discoloration. 298 µm and the weld line on the heated region was almost eliminated with the aid of induction heating. also utilized the co-injection molding technique to study the flow of polypropylene at the weld line behind an obstacle in injection molding; the weld line can be seen clearly from the Fig. industry, to deliver intuitive injection mold-ing simulations embedded in NX. This reduced thickness of the frozen skin further enhances the visual appeal of the. To prevent weld lines, increase the pressure and temperature. In this regard, the plasticizing ability of the plastic injection moulding machine should be checked. Expand. Weld lines can significantly reduce ultimate tensile strength (UTS) and fracture strain of talc filled polypropylene (PP). Flash. ac. Weld lines may appear like seams or scratches, but that is not what they are. 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. Int J Adv Manuf Technol 52:131–141. Increase the mold temperature. In the first, sequential injection moulding, the lines are displaced to noncritical areas of the moulding. For multiple gate and complex part. Increase the injection speed to reduce the amount of cooling happening in the mold. 2. สาเหตุรองของการเกิดปัญหาการเกิดประกายเงิน (silver streak) 1. The weld lines are an integral part of plastic injection molding and can seldom be prevented, even by specifically planning the mold with inserts for holes or the like. In order to study the weld line developing process and its influence on mechanical properties in micro injection molding, a visual mold with variotherm system mold was designed and fabricated. The second technique, cascade injection moulding, can produce parts free from weld lines. During injection moulding, a weld-line occurs when two or more flow fronts collide in the hollow cavity. Re-balancing entire manufacturing lines may be required to effectively deliver and sustain SMED excellence. Table 2-Glass Fiber Glass Fiber Glass Fiber Glass Fiber 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. M. 6. Mold flow analysis can predict the location of weld lines. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. In this case the two flow fronts will meet and there will be very little molecular orientation across the weld. Again, consult with professionals as to how you could improve mold designs. Three terms that often get mixed up are weld, meld, and knit lines. Wu CY, Ku CC, Pai HY (2011) Injection molding optimization with weld line design constraint using distributed multi-population genetic algorithm. th INTRODUCTION Injection molding is one of the mostWeld lines have been one of the common defects puzzling the injection molding industry. Email him at jhenz@polymer-center. The weld-lines are undesirable from both aesthetic and functional points of view and their effect is different for. Various measures are taken at production sites to address these problems. Weld line and warping are two critical defects for injection-moulded part. During the plastic injection molding process, one of the biggest challenges is. The weld lines in injection molded parts arise as a result of the collision of two fronts of the flowing material, which fills the mold cavity and are sometimes unavoidable [1][2][3] [4]. Sequential valve gate technology. Minimize the use of release agent. Improper fusion of two fluid flows, a state before weld line. Try to gradually raise the mold temperature and barrel temperature. If the plasticizing ability of the plastics injection molding machine is insufficient, the plastic cannot be fully plasticized, resulting in weld lines when filling the mold. 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. One common issue that frequently arises during injection molding is the formation of weld lines. Plastic Injection Molding Process. A poor knit line. These lines can weaken the strength of the part, and they can also be unsightly. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. This defect occurs due to the temperature and pressure not being high enough, causing premature solidification. Equipment. 2. 2. Azuddin / Procedia Engineering 184 ( 2017 ) 663 – 672 Fig. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. The Solutions for Poor Welding Lines. With unchangeable and fixed requirements for the final product, their avoidance often proves difficult. The microstructure of weld lines is clearly observed from the micrographs. Weld Lines are formed when two or more molten polymer flows meet during the injection molding process. The type of resin used during injection molding plays a large role in whether or not a knit line will be present. 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. In addition, its tensile strength and stiffness will be sharply decreased. Weld Line Factors for Thermoplastics. The weld lines in blow molding occur wherever the pari son knits together in the head, mold tacking areas and mold parting pinch-off region. Weld line Weld line dikatakan ketika dua atau lebih aliran lelehan depan. demanding injection molding and end-use requirements. Vibration assisted injection molding. The following are the reasons. Weld line strength is important in blow molding as well as injection molding. 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]. Weld lines represent the region where two separated melt fronts recombine. Neat polypropylene retains nearly 90% of its strength on a properly designed and molded weld line. They decrease the. In order to reduce these weak points, a special ram technique for injection molding, which can be integrated into the mold, was investigated. T. Figure 1 below shows the development of a weld line. 025 100 120 140 160 180 200 220 240 Mold Temperature (F) LDPE PPEffects of mold temperature and pressure on shrinkage 0. In spite of its cosmetic attributes, a bad knit line can significantly. Therefore, the investigation on the developing process of weld line would be a significant issue for improving the quality of micro injection molded parts. 2. Sink marks are a common type of injection molding defect. In narrow fields, a limited amount of molten liquid can solidify and block the flow. As such, optimizing mold designs should always be incorporated in your production model. 000 0. 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. Melt temperature does effect the weld. gas, which can cause blistering, as well as poor weld lines, warpage and the formation of cold slugs that affect filling and part mechanical properties. . Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. They can affect the strength and. Our injection molding company is explaining what these imperfections are, why they can compromise. 1. If you have critical requirements for strength of knit lines, please call a Protolabs applications engineer at 877-479-3680 to discuss, or email at [email protected]. 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. In this regard, Taguchi orthogonal experimental design is adopted, and five processing parameters, the mold temperature, melt temperature, cooling time, packing. 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. In some cases, a weld line can also cause a loss of strength and impact resistance. Maintain a holding pressure that is no more than 1/2 the. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. 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. Melt temperature is 250°C, mold temperature is 110°C. As compared to a weld line, the flow fronts come together at less than 135 degrees. The impact behavior of weld-lines in injection molding. 1% higher than the ones without ultrasonic assistant, which indicates that the weld line strength in micro injection molding can be well reinforced by the ultrasonic oscillation due to the fact that ultrasonic oscillation induces better diffusion among the melting. 18/06/2021. This principle has been implemented on a complex component in the case of the spring-loaded cogwheel shown in Figure 5, for instance. Park et al. Or, the part where the weld line is produced shall. 015 0. Meld and knit lines are actually both different types of weld lines. Weld line problem which occurs in polymer parts produced by plastic injection method and affects appearance and strength on a large scale was researched in this paper. A flat product case was considered as an example of a typical aircraft structural element. This study focuses on the analysis of fill time by optimizing the injection molding parameters to reduce the defects that are always found on the plastics part such as poor weld line and part not. Weld lines not only detract from an injection-molded part’s surface quality, but also significantly reduce its mechanical strength. It occupies a major part in the plastics industry ranking second to plastic extrusion in terms of production and the utilization of both thermoplastic and thermosetting plastic materials. when two or more melt flow fronts contact each other immediately after the cooling process. Joe Henz is a chemical engineer with 30 years of experience in the plastics industry, primarily with GE. An injection molding processor who can analyze the process from the plastics point of view, can quickly solve any molding problem, regardless of the machine or plastic type. Criens, R. Insufficient plasticizing ability of injection molding machine. Fracture behavior of weld lines in injection molded components loaded under real operating conditions. If you have critical requirements for strength of knit lines, please call a Protolabs applications engineer at 877-479-3680 to discuss, or email at [email protected]. II. Short Shot Short Shot adalah suatu kondisi dimana, plastik leleh yang akan diinjeksikan kedalam cavity tidak mencapai kapasitas yang ideal atau sesuai settingan mesin. They can affect the strength and appearance of the part, depending on the temperature, pressure, speed, and mold design of the injection molding process. Gava and co-workers implemented an investigation devoted to the de-weld lines in injection molded thermoplastic composites. In this paper, aiming at the problem of weld line defects in the injec- tion process of a key phone panel, the injection process is optimized by using Moldflow and drop simulation. 2. Computer simulation packages of injection molding have had success in predicting filling behavior in extremely complicated geometries, capable of predicting weld lines’ location exactly. Fatigue crack growth (FCG) tests were conducted on SEN specimens prepared from 100 mm. A meld line occurs when two moving melt fronts converge and flow parallel to each other. อุณหภูมิของพลาสติกเหลวสูงเกินไปจนก๊าซหรือความชื้นแยกตัวออกมาได้. Published 5 July 2019. Insufficient injection pressure and speed can cause weld lines. a) Multi-fiber connector micro injection molding simulation b) 3D simulation of micro gear with 150µm diameter for weld line position prediction c) 3D micro injection molding filling simulation of micro gear with 180µm diameter Fig. 2. This study addresses the effects of injection molding weld line on the fatigue crack resistance of commercial CPVC in the temperature range of −10 to 70 °C. (1) Flash: Extra plastic material in the shape of films or burrs, which appears on the parting surface, around the runner or in the insert crevice. (2011) and Fig. Mold vents should function the same way. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. 9. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. Remedies: Raise the temperature of the mold or molten plastic. Injection molding is nothing without molds. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection. [ 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. A simulation process was conducted to determine the recommended setting of injection moulding parameters and the range of the variable. In this lesson we will focus on the meld and weld lines. How to Reduce Weld Line in Injection Molding? Weld lines are a common issue that occurs in injection molding. 005 0. These flow. In order to prepare the weld line specimen by micro injection molding, a mould integrated with visual system and variotherm system was designed and constructed, shown as Fig. This failure causes the product to be damaged during use. Three terms that often get mixed up in injection molding are weld, meld and knit lines. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. In this study, the effects of injection temperature, injection pressure, and fiber cont. 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. สาเหตุการเกิด weld line คือเมื่อการไหลของพลาสติกมาประสานกันนะจุดใดจุดหนึ่งและจุดนั้นเกิดความแตกต่างของอุณหภูมิในสองทิศทางการไหลจะทำให้เกิด. Investigate for potential contamination. 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. 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. As the plastic flows through the mold it. The welding angle can be used to differentiate weld lines and meld lines. As a result, the portion has a faint, perhaps undetectable line. <Materials> Pre-dry thoroughly. If the plasticizing ability of the plastics injection molding machine is insufficient, the plastic cannot be fully plasticized, resulting in weld lines when filling the mold. This customary mark is caused by differential rates of cooling in the resin where. 2023年1月3日 / by admin. Weld lines are also known as knit lines. 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. But add 30% glass and weld-line strength retention drops to only 34% as high as the compound with no weld. 015 0. Conventional injection molding is widely used to produce plastic parts, mainly in the automotive industry, due to the high production ratios and quality of. A weld or meld line is a weakness or visible flaw created when two or more flow paths meet during the filling process. 2) Vents in an injection mold should let the air out, but not the liquid plastic. Flow marks in injection molding are defects that manifest as a line or series of lines forming a pattern different in color from the other parts of the molded material. 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. Optimization of Injection Molding Process to Minimize Weld-line and Sink. Injection molding is a complex multi-variable, nonlinear and time-varying unsteady process, which makes it more difficult to optimize the process parameters. If the plasticizing ability of the plastics injection molding machine is insufficient, the plastic. Yes, it does help, for two reasons: Often the weld line traps air and the ‘dump’ acts as a vent to allow the air to escape. 020 0. Our weld line injection molding is essential for the best result of finished molded products. Weld lines have been one of the common defects puzzling the injection molding industry. 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. The weld line’s strength is reduced when. Wolfgang Homes, head of the applications department of Eurotool, a manufacturer of hot runner systems, clarified the two methods for IMI, noting that. 1. Crack growth behavior. Materials Science. Participating in DFM and mold flow analysis is a good way to achieve this. Weld lines are one of the typical quality issues of injection molded parts. Polyamide-6 (PA-66) was used as. 4. They occur when melt flow fronts collide in a mold cavity. Jiquan Li, Taidong Li, +1 author. 3. In this study the polycarbonate (PC) and carbon fiber (CF) are used as the experimental materials to investigate the impact of injection molding process parameters on tensile strength of weld line. Weld lines can lower the integrity of the part. Injection molding can be performed with only one of these materials like glass, plastics, etc. It occurs when melting plastic material is injected into a mold, it flows through all parts of th. To explore the formation of weld lines in injection molding, a. Meld lines are formed when two separate flow fronts meets. According to the characteristics. 2017-01-0481. The injection molding process can be optimized to maximize weld line strength by increasing. Micro injection molded polymeric parts coated with functional thin films/layers show off the promising applications in microsystems area. The results showed that the tensile strength of PE remains unchanged in the presence of weld lines. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. (3-1) Increasing the Resin Temperature at the Weld Line Section. Penyebab Weld Line. Investigate for potential contamination. Weld lines are formed when two orAbout Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright. Weld lines may appear like seams or scratches, but that is not what they are. Here are a few of the most common defects that may occur in plastic injection molding — and how product teams can avoid them. Polym. Facebook. From: Polylactic Acid (Second Edition), 2019. The quality of the weld line can be improved through optimized processing conditions, increased mold and melt temperatures, and increased injection speed to reduce the viscosity of the polymer. 809-814. The Problems & Solutions course is designed to train injection molding personnel in. com1. By the reflection method and a high speed camera, the visual system can be used to record and observe the forming process of micro weld lines during the. In the heating step, the heatingOverview of the injection molding process. ”Weld Lines in a plastic cover. In a meld line, the plastic comes together at an angle greater than 135 degrees. Known also as knit lines and weld marks, weld lines are difficult to eliminate completely, especially if your injection molded part requires holes. Weld-line, a common occurrence in plastic injection moulding, is a representative defect compromising mechanical qualities and product appearance [16]. Weld lines are a kind of Achilles heel of plastics. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. Plast. To prevent knit lines, injection molders can increase the temperature of the molten resin to prevent solidification from starting too soon, and increasing injection speeds and pressure are also potential solutions. They are unavoidable even for moderate complex products. Fracture behavior of weld lines in injection molded components loaded under real operating conditions. As the weld line can significantly lower the mechanical strength of µIM parts, it is relevant to clarify the position of weld. The Factors that Cause Weld Line in Injection molding Pressure. These are caused by the shot of molten plastic moving at different speeds throughout the injection. a) Multi-fiber connector micro injection molding simulation b) 3D simulation of micro gear with 150µm diameter for weld line position prediction c) 3D micro injection molding filling simulation of micro gear with 180µm diameter Fig. Adjust the design for the flow pattern to be a single source flow. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection molding processing. For the production of these weld‐line specimens, a special mold was used and injection molding parameters were systematically varied, tensile (ISO 527‐2) and impact (ISO 179‐1/1eU. Polym Eng Sci 45(7):1021–1030. Boost time too long Shorten boost time, lower boost pressure, or move transfer to an earlier position . Effects of cavity surface temperature on mechanical properties of specimens with and without a weld line in rapid heat cycle. The gate location should enable the two flow fronts to merge easily and continue to flow beyond the weld line. Plastic part design for injection molding – An introduction. Sink Marks Cause 2: Low Pack and Hold time. Insufficient plasticizing ability of injection molding machine. The definition of weld lines: When multiple plastic flow fronts meet in the cavity after encountering inserts, holes, or areas with inconsistent flow rates or interrupted melt flows, or in the case of gate injection filling, the inability of two or more flow fronts to fully “knit” together will cause the linear weld marks. Despite injection molding being recognized as a robust process for obtaining parts with high geometry accuracy, one last occurrence remains a challenge in micro-injection molding, especially when junctions are. Weld lines are a common issue in injection molding, and occur when two flow fronts meet and fuse together as the material cools and solidifies. The flow of the material in the injection mould takes place through the gate. as warpage, shrinkage and weld line of the plastic parts. Designers can easily set up and perform analysis with only a few clicks. What causes them? The primary cause is weak bondage between two or more flow fronts. A tensile test specimen mold, which allows cavity thickness varying from 2. Flow lines arise when at least two melt fronts meet at an acute an-Weld line is aesthetically unpleasant and affects the mechanical strength of injection molded parts. Mechanical properties of the weld line defect in micro injection molding for various nano filled polypropylene composites. Some of the approaches include the application of machine learning methods (Chen 2008; Manjunath and Krishna 2012; Kuo et al. 3. The three parameters affecting operation were called injection pressure, injection time, and packing pressure which influence the quality of weld line. Reduce the amount of release agents. Weld line formation in the injection molding process occurs when two or more melt flow fronts contact each other immediately after the cooling process. This paper analyzes production data from injection molding processes to identify key interactions between the process variables from different material categories using the network inference method called “bagging conservative causal core network” (BC3net). [1] Kobayashi et al. The weld line’s strength is reduced when. This type of injection molding resolves any trouble caused by undesired welding lines. An evaluation model based on artificial neural network method. ” Another. The impact behavior of weld-lines in injection molding. The defects encountered could be caused by mechanical factors, such as poor mold design and mold manufacturing, or by processing related factors, such as incomplete kneading, inadequate molding pressure, injection. This article will introduce you the usage, types, and advantages of the Sequence Injection Timer. Plastics manufactured by injection molding are meant to be durable and reliable, able to hold up to heavy use, high temperatures, or adverse conditions. In this mold, a visualization design and a rapid heating/cooling system were integrated, and specimens with different cross section. As these flow fronts come together on the. Alloys. Nozzle – The nozzle is at the end of the barrel and contacts the injection mold. Voids and bubbles, 6. Materials Science. From Understanding Weld-line Integrity by Sabic Innovative Plastics, p. 2020-01-1306. A weld line develops when two or more flow fronts come together but do not meld completely because of partial solidification. Polymers 2023, 15, 2440 3 of 21. Weld-line, a common occurrence in plastic injection moulding, is a representative defect compromising mechanical qualities and product appearance [16]. Flow Lines. 21: Weld line failure caused by hoop stresses. In the sense that the weld line is better formed before the resin temperature. But the unfavorable and unavoidable defect of weld line in micro injection molding part leads to detrimental mechanical and surface properties. 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. 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). It is important to investigate the weld line because the weld line area can. (1) make the mold vent larger at location with weld line; (2) Check if the mold vent is blocked or not or use vacuumized forming. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. Weld line is one of the plastic injection molding defects. 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. Fortunately, there are several. This failure causes the product to be damaged during use. 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. They found that the weld line is a zone between 2 and 8 mm wide extending throughout the thickness in whichTo investigate the effect of hot gas heating in injection molding on the weld line appearance, an experiment was conducted with the molding parameters listed in Table 2. The cracking was always located in the weld/knit line and therefore caused by weakness in the bonding of the plastic at. 2. Figure 1 a illustrates how the weld line is produced when two melt streams merge during the final filling process.