The differences between knit and meld lines are significant, and they can dramatically impact the part’s structural integrity. C. 2. Molding Equipment. A weld line is often unavoidable. th INTRODUCTION Injection molding is one of the mostWeld Lines in a plastic cover. They are unavoidable even for moderate complex products. Here’s how to decrease the chances of weld lines: Increase the temperature of the mold or the molten plastic. Jiquan Li, Taidong Li, +1 author. An obstruction such as a core pin or holes will split the material flow and cause a weld line issue to form on the other side. Mérillou, J. The Factors that Cause Weld Line in Injection molding Pressure. The Solutions for Poor Welding Lines. Founder, Injection Molding Solutions. Plastics manufactured by injection molding are meant to be durable and reliable, able to hold up to heavy use, high temperatures, or adverse conditions. <Mold> Provide a cold slug well where weld lines occur. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties [3,4,5]. Besides, possibly it would be. Since it is often impossible to avoid weld lines as well as a limited possibility to increase the weld line strength by adjusting the injection molding parameters, a method to predict the weld line strength in the product development process is shown below. Plastic Injection Molding Process. For multiple gate and complex part. Wolfgang Homes, head of the applications department of Eurotool, a manufacturer of hot runner systems, clarified the two methods for IMI, noting that. 4. In this paper, two different injection molding tests were completed. 3. Polymers 2023, 15, 2440 3 of 21. Low mold temperatures are usually employed to decrease cycle molding time and final process costs; however, resulting surface defects include weld lines, sink marks,. To elimi- nate weld lines, you can enlarge shrinkage. micro injection molded weld line’s mechanical properties. Introduction. Figure 2. Co-injection molding technique is a useful way to study weld lines, which can offer more detailed information of the. Fisa et al. As these flow fronts come together. Sink Marks Cause 2: Low Pack and Hold time. 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. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. That helps. In this lesson we will focus on the meld and weld lines. They decrease the. Flash. Weld-line is a weak area which reduces the strength of the part locally. Experimental Setup 2. (1)Injection Machine Poor plasticization and non-uniform melt temperature – appropriately extend the injection molding cycle, to ensure thorough plasticization, and change for a machine with a larger. The solution to an internal part cracking problem is to change the packing pressure. Ejector System (Pötsch, 1995) . 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. Introduction Weld lines are formed during mold filling whenever two separated melt streams recombine. Weld line existence reduces the material strength; however, its demerit characteristics. A weld line (weld point, flow line or a knit line) forms when separate melt fronts travelling in opposite directions meet. Wu CH, Liang WJ (2005) Effects of geometry and injection-molding parameters on weld-line strength. The following are the conclusion drawn from the present research: 1. In this regard, the plasticizing ability of the plastic injection moulding machine should be checked. In conclusion, reducing weld lines in injection molding requires a combination of factors, including adjusting the melt temperature, injection speed, pressure, and gate size, as well as using a hot runner system, modifying the part design, using a different material, reducing the wall thickness, using a mold release agent, and working. Weld lines, generated during injection molding, can significantly reduce the mechanical performance of structures. Injected plates were generated using a double-gated mold under four different process conditions. If the melt temperature is low or the injection speed and pressure are low, you may end up with a more pronounced weld line. Clamping Unit. • Optimize the design of the runner system. Consequently, it causes viscous dissipation which leads to the generation of heat. Micro-injection molding (µIM) is a widespread process for the production of plastic parts with at least one dimension, or feature, in the microscale (conventionally below 500 µm). Mold Design. Adjust the design for the flow pattern to be a single source flow. In this work, the residual strength of a fiber-reinforced injection molded part containing a hot weld line—or meld line—was evaluated. , 2 (3–4) (1988. 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. Shaofei Jiang. Meld lines are formed when two separate flow fronts meets. The structure is more complex with longer molding cycle . Sink Marks 2. Use a less viscous plastic. It will degrade materials performance; 9. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. Azieatul Azrin Dzulkipli and M. Remedies: Raise the temperature of the mold or molten plastic. Weld lines in injection molding are frequently unavoidable. The four sets of plaques are produced by changing the magnitude of packing pressure equal to 60% of filling pressure, with increment of 20% up to 120% of filling pressure. The foundation to any robust process, in my opinion, is based on choosing the correct fill time. in the cavity of the injection mold. How Are They Formed? Molten plastic resin is injected into a mold cavity through an opening known as a gate. This paper presents the. Its appearance can be improved by adjusting parameters. Weld Lines. He now teaches courses in injection molding and plastic part design at the Polymers Center of Excellence and UNC-Charlotte in Charlotte, N. Injected plates were generated using a double-gated mold under four different process conditions. This principle has been implemented on a complex component in the case of the spring-loaded cogwheel shown in Figure 5, for instance. Premature partial solidification of the molten plastic leads to inadequate bonding — the primary cause of weld lines. Unless you are manufacturing an extremely simple part with one gate and a unidirectional flow front, your part will have weld lines. Here we are looking at most common part defect that can come from injection molding called weld line. Meld Lines. Weld lines can significantly reduce ultimate tensile strength (UTS) and fracture strain of talc filled polypropylene (PP). Try to gradually raise the mold temperature and barrel temperature. Weld line formations can be weak if they fall in areas that will bear stress or impact. The Injection Moulding Process is a manufacturing process used for producing parts or components by injecting molten material into the mold cavity. Abstract. The injection molding temperature and the mold temperature were fixed respectively at 230 °C and 50 °C. (3) Adjust the temperature of the barrel and nozzle: the viscosity. + Adjust injection speed. (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. Weld lines have been one of the common defects puzzling the injection molding industry. 1. The appearance quality of plastic parts in weld lines can be improved significantly through the rapid heating cycle molding (RHCM). In this experiment, several ejector. Remedies: Raise the temperature of the mold or molten plastic. One method is the local te mpering of the affected areas to prevent weld lines. There is excess air inside the mold (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 can also be called a knit line. Weld Line defect analysis, the most common of many defects in injection moulding products. Plastic Injection Molding Process. They decrease the. M. Weld line formation in the injection molding process occurs. wall thickness, gate and runner designs and re-validate the result. 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. 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. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. The main types of injection molding defects are: 1. Figure 1a illustrates how the weld line is produced when two melt streams merge during the final filling process. Wu CY, Ku CC, Pai HY (2011) Injection molding optimization with weld line design constraint using distributed multi-population genetic algorithm. Using the conventional method, weld-line depths on the surface ranged from 6 to 13 microns. 1. Weld-line, a common occurrence in plastic injection moulding, is a representative defect compromising mechanical qualities and product appearance [16]. Mold flow marks, also known as flow lines or weld lines, are often caused by variations in the flow of molten plastic material during the injection molding process. Meld and knit lines are actually both different types of weld lines. Provide a gas vent. Figure 1 a illustrates how the weld line is produced when two melt streams merge during the final filling process. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. It occurs when melting plastic material is injected into a mold, it flows through all parts of th. 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. 2017-01-0481. These lines. the meeting angle by optimizing variation over time in the cavity. 3. Optimizing the Injection Parameters. The results of. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. The welding angle can be used to differentiate weld lines and meld lines. Weld lines are a surface defect caused when two or more flow fronts come together during the injection process. Definition: A seam that appears where two areas of molten plastics meet. From Fig. are very minimum. 1 Prediction of weld lines with injection molding simulation softwareReduced frozen skin thickness: High injection speeds also contribute to a thinner frozen skin at the weld line. Gate location should set to avoid weld lines, keep clean of the important position of the products,. Therefore, it is recommended to do a moldflow study prior to the mold being built. The weld line in injection molding is created when two melt streams connect, as shown in Figure 1. The type of resin used during injection molding plays a large role in whether or not a knit line will be present. In the first, sequential injection moulding, the lines are displaced to noncritical areas of the moulding. To explore the formation of weld lines in injection molding, a. 1. 1. Injection molding could be applied with many polymer materials, such as. Injection molding of large/complicated products are usually prepared by multiple compounds, which produces weldlines once the melt fronts are joined by impingement flow. 015 0. (1)Injection Machine Poor plasticization and non-uniform melt temperature – appropriately extend the injection molding cycle, to ensure thorough plasticization, and change for a machine with a larger. 3: Weld Lines. Save. 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. weld lines in injection molded thermoplastic composites. with a characteristic length χ 0 =0. A flat product case was considered as an example of a typical aircraft structural element. 025 100 120 140 160 180 200 220 240 Mold Temperature (F) LDPE PPAccording to the weld line distribution map of six gate schemes shown in . when two or more melt flow fronts contact each other immediately after the cooling process. One common issue that frequently arises during injection molding is the formation of weld lines. Another relevant topic in injection molding is the presence of weld lines (WLs) and their properties, which could lead to part weakness through surface disturbances, optical issues and reduced bonding [21, 22]. Park et al. 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. Sink marks are a common type of injection molding defect. , 190°C mass and 20°C mold temperature, as well as. Adding vents, using overflows, or using porous metal. The literature on the formation of weld lines, and their consequences, is more abundant on the area of injection molding [5-12] than on extrusion [13]. However, research about the computer determination of weld lines in injection molding remains scarce. 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. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties [3,4,5]. As compared to a weld line, the flow fronts come together at less than 135 degrees. The spreading mold release agent on the part cavity surface might eventually cumulate at the V-notch groove of the weld line after each injection molding shot. Weld lines are a common imperfection to be found in most plastic injected molded parts. (a) (b) Figure 1. 13. Failure may result due to the assembly torque, or end-use application loads (temperature, creep). In this experiment, several ejector. Thus, it is important to understand (i) if the melt is able to fill the cavity up to the weld line location, (ii) where the weld line forms, and (iii) if the weld line is a cold or flowing one. 2. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. In weak material bonding, they will appear as hair-like weld lines. In this paper, a kind of polypropylene (PP) foam plastic parts with special weld lines were obtained by core-back foam injection molding with chemical blowing agent. Insufficient injection pressure and speed can cause weld lines. According to the special features of micro injection molding process compared with normal injection molding process, the main related factors to weld line’s properties were classified as 3 group, named as processing conditions, mold design and structure, external process. The results showed that the tensile strength of PE remains unchanged in the presence of weld lines. Weld lines may occur on a molded part’s surface where, after breaking off into two or more directions in a mold, the molten material has converged. Int. The choosing optimal gate location technique has been developed to set weld lines as far as possible from the region of maximum stresses. The default weld line result recognizes 135º as the maximum angle of collision and as that angle decreases, the severity increases as it. 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. During the plastic injection molding process, one of the biggest challenges is. 2. Weld lines appear as a result of the flow of molten plastic during the injection molding process. Wang et al. (3) Adjust the temperature of the barrel and nozzle: the viscosity. Alter the mold design. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. 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. Weld Lines are formed when two or more molten polymer flows meet during the injection molding process. This happens when the molten plastic is injected into the mold cavity and flows around an obstacle such as a pin, hole, or protrusion, and then comes back together. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. demanding injection molding and end-use requirements. So today we are going to take a look at the five most common defects in injection molding and their solutions. Bubbles are caused by melting flow fronts colliding in a mold cavity. Mold temperature controlInjection mold designers can alter the position of weld line by changing the gate locating. Figure 1 below shows the development of a weld line. Insufficient plasticizing ability of injection molding machine. As the unfavorable defect in micro injection molding parts, weld line brings reduced mechanical and physical properties, especially for nano filled composites. In other words, weld lines reduce the mechanical properties of the product. In Fig. Wavy lines are another feature of weld lines. High-density PE was also moulded in the same conditions but in a lower temperature range (145 to 220°C). This is where the melt fronts divided by an insert, such as a pin or a. Proper venting is also required to ensure good weld-line quality. poor flow fronts that are too cold, this can also lead to a deterioration in the mechanical properties. Therefore, more studies covering this subject are required in order to improve the insight regarding the mechanism involved in the formation of weld lines in extrusion and,From the so-produced materials, specimens with weld lines were produced according to the first test series, but varying the injection molding parameters only twice, between the best and worst settings found in the previous study with the polypropylene types with MFR 8 g/10 min, i. Weld lines cause significant reject rates and are a common problem that all molders face. investigated the impact of injection molding parameters on weld line formation and strength reduction. As a result, the portion has a faint, perhaps undetectable line. This customary mark is caused by differential rates of cooling in the resin where. 001 in . Injection pressures too high Reduce pressure . 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. They are unavoidable even for moderate complex products. Increase the size of the gate and runners to alter the mold design. 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. 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. (2) Adjust the injection speed: high speed allows the melt to reach the confluence without cooling down, and low speed allows time for the air in the cavity to be discharged. Sink marks, 2. 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. This special mould has changeable inserts to be able to inject with different gate types (standard, film, special-film, multi gates, etc. Micro-injection molding (µIM) is a widespread process for the production of plastic parts with at least one dimension, or feature, in the microscale (conventionally below 500 µm). Increase the injection speed and mold/operational temperature to prevent fracture or surface breakdown. Injection molding is an efficient manufacturing process for mass-producing parts with complicated geometry. Weld line. 000 0. (1983). Evaluate and optimize your part design The advantages of using the moldflow analysis to avoid potential defect like deformation, shrinkage, welding line etc, part designers can change the wall thickness or enhance the ribs to improve their part design. 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. Weld Lines 5. 298 µm and the weld line on the heated region was almost eliminated with the aid of induction heating. Many studies were conducted to explain the weakness at the. Increase the injection speed. This is a video excerpt from our Problems & Solutions Course - Weldlines. Change the flow pattern to a single-source flow. This injection molding defect appears as a black discoloration on the surface of the molded part. The injection molding simulation software used offers a method for the detection of weld lines that has shown to be only reliable for the detection of stagnating weld lines. Reduce the amount of release agents. Weld lines are one of the typical quality issues of injection molded parts. It has larger cross-sectional regions that allow sufficient molten plastic flow into the cavity. Here are some ways to avoid. Micro weld lines are the common problem that occurs for plastic molded parts through injection molding process. 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 Injection Molding Parameters: Optimizing injection speed, pressure, and temperature can help ensure better melt flow and reduce the likelihood of weld line formation. You can choose material of low viscosity and can increase the injection pressure. In this study, epoxy molding compounds (EMC) filled with glass beads were fabricated with a twin-screw-extruder (TSE) and tempered before further processing to generate different degrees of cross-linking (0–15%) in the compounds. Proceedings of ANTEC (2000), pp. The flow fronts at different times (Fig. Weld-line is a weak area which reduces the strength of the part locally. 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. Gates should be designed larger than normal and located to minimize weld line formation. As the plastic flows through the mold it forms a smooth and continuous flow front. Instead of using flow leaders and deflectors to control the locations of the weld lines, this paper presents an approach to specify the locations of the weld. Effects of mold temperature and pressure on shrinkage 0. Weld lines. 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. Too high barrel temperature ( abnormal temperature control, deviation of material performance, and increasing cycle time); 8. Weld lines are formed when two orThe experiments were performed on an Arburg Allrounder 320C 600-250 injection moulding machine using a two cavity-injection mould (Fig. Heating and cooling mould systems, which cost extremely high, are a typical technology to prevent the weld-line. When two or more streams of plastic meet and fuse together, a visible line or weakness is formed on the surface of the finished product. You will have to confirm them before tooling. consideration in gate location. Flow-induced filler orientation manifests in higher tensile prop-erties in the direction of flow compared to those normal to the direction of flow. This month, in our FREE SimTech™ series of webinars, we will explore weld lines and how they develop. The injection molding process can be optimized to maximize weld line strength by increasing mold and melt temperatures, and by increasing pack pressure at the weld line. Injection Molding Know How. Criens, R. Vents in the mold allow the mold to fill. ) . The need to minimize fiber breakage, plus the higher viscosity of materials with. Weld line formation in the injection molding process occurs when two or more melt flow fronts contact each other immediately after the cooling process. According to the characteristics. Weld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of injection‐molded parts. Melt temperature does effect the weld. A quantitative evaluation of the appearance quality of weld lines in RHCM parts. Weld Line defect analysis, the most common of many defects in injection moulding products. In a weld line, reinforcement fibers adopt an orthogonal orientation with respect to the filling direction, which results in a significant reduction in the strength and. In spite of its cosmetic attributes, a bad knit line can significantly compromise a part. 5. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. Increasing the temperature of the mold or plastic material. Weld lines can be caused by many reasons, which covers the various aspects of mold, process, raw materials and product design, etc. Weld lines are a common occurrence in injection molding that affects the overall quality and strength of a finished product. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. The thermo-rheological findings were used to investigate the sources of weld line weakness. The terahertz time-domain spectroscopy (THz-TDS) imaging technique was used to detect the weld line defect of an injection-moulded short glass fiber-reinforced composite. The second technique, cascade injection moulding, can produce parts free from weld lines. Flow-in-duced fiber orientation manifests in higher tensile properties in the direction of flow compared to normal to the direction of flow [13–15]. ”. In our DFM report, we will analyze the possible weld lines. [1-2] investigated the weld line zone of injection molded glass-fiber-filled polypropylene (PP) composites. Except for a few injection molded parts with very simple geometry, they occur on most injection molding parts (the shape is usually a line or V-shaped groove), especially Large complex items requiring the use of multi-gate molds and inserts. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. That helps. 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. The four sets of plaques are produced by changing the magnitude of packing pressure equal to 60% of filling pressure, with increment of 20% up to 120% of filling. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection. 015 0. ppt from SCIENCE 101 at Symbiosis International University. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. Weld lines are visually undesirable and a plastic part is structurally weak at weld line positions. The special injection mold is designed and fabricated to produce plaques having stagnation weld-line. Fig. In many cases, you will also see that the part is hanging up on the core during ejection. Weld lines represent the region where two separated melt fronts recombine. The governing equations for the melt and the air in the cavity are united into…. To determine the effect of the weld lines on tensile strength, tensile tests were conducted with the specimens fabricated with NORYL (amorphous blends of. Weld Lines-3 Ways for Detecting and Correcting. It forces out trapped air pockets and can prevent a vacuum void from occurring. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. One of the defects observed in injection molding parts is weld line strength, which forms when two or more separate melt fronts traveling from different directions meet and join as the mold cavity is filled. Flashes, 3. Steven. Which means engineers need to know how to account for this phenomenon in an efficient way. The edge gate is the most popular and straightforward injection mold gate design. This paper presents the. 2. In a weld line, reinforcement fibers. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. The injection molding gate generates heat by dissipation. In the injection molding process, weld line regions occur when a molten polymer flow front is first separated and then rejoined. 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]. In an injection molding process, a weld-line forms when two flow fronts meet each other. 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. Weld line formation in the injection molding process occurs. Streaks 3. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. 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. In this study, the effects of injection temperature, injection pressure, and fiber cont. 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. 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. 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. Controlling the mold’s temperature could also minimize the weld line’s effects. 13 shows the best gate location for which the weld lines . If you adjust the ejection mechanism in the mold design, you also can reduce or eliminate your need for mold release agents. Weld lines, created in the areas of collision of two flow fronts of plastic in the injection mold cavity, are the reason of lower mechanical properties and a worse surface condition of molded parts. Wavy lines are another feature of weld lines. As the name implies, it is usually positioned along the edge of the workpiece, forming a visible mark at the demarcating line. A weld or meld line on plastic parts can cause structural problems and/or be visibly unacceptable. The part becomes partially solidified and won’t sufficiently bond where the two halves meet, resulting in. 3 the path lines of selected material elements can be observed which are. ” Another. As a result, the path of the injected melt can be extended, allowing the production of parts with more complex shapes and greater length. Figure 1 below shows the development of a weld line. Azuddin / Procedia Engineering 184 ( 2017 ) 663 – 672 665 2. 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. (2011) and Fig. 2. This study focus on the formation of. 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. The holding pressure was set as approximately equal to the maximum injection pressure obtained at the time of filling the resin. In this study, polypropylene (PP) was compounded respectively with carbon nano fibers (CNFs) and TiO 2 nano particles at various weight fractions (10, 20, 30, 35. Mold vents should function the same way. Mold vents should function the same way. Here is a look at the differences between them, the causes of meld and knit line imperfections, and their impact on part durability. It is normally at the meeting points of two flow fonts. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. Weld lines in injection molding are frequently unavoidable. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Part design features may cause a material flow to split and rejoin as it flows around design features in a mold. 2) show that the weld line is formed as expected from the middle of the cavity towards the wall. Weld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of injection‐molded parts. 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. Weld line is formed when two different melt flows converge, as illustrated in Fig. Weld lines have been one of the common defects puzzling the injection molding industry. To respond to poor plasticization and uneven melt temperature,. T. S. Weld lines not. Kobayashi et al. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. injection molding is followed by the welding. When the two such melt flows. When an external load is applied to a weld line region, the part’s potential for mechanical failure is increased.