The gate is the critical bridge between the runners (the channels through which the molten plastic travels) and the actual mold. Effect of process parameters on the relative weld line strength From injection molding practice and literature, 1, 3,4 it is generally accepted that: if a weld line forms before the filling is. 7 in Kobayashi et al. Avoid knit lines when designing a molded part to improve cosmetic appearance and functionality. To respond to poor plasticization and uneven melt temperature, the molding cycle can be extended to make. Poor weld line Ⅰ. Thoroughly clean molding machine cylinders. 2-1. 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. In. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. Figure 2. A weld line can also be called a knit line. Change the gate locations. 2. Weld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of injection‐molded parts. Flash. Weld lines are formed when two melt fronts come in contact with each other. Weld Lines. As such, optimizing mold designs should always be incorporated in your production model. As a result this weld line will be a weak point in this part. (3) Adjust the temperature of the barrel and nozzle: the viscosity. , a post that forms a hole) and then rejoins, or when polymer melt fronts meet, from multiple injection points. 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. Injection molding is a highly versatile manufacturing process used to produce a wide range of plastic products with precision and efficiency. สาเหตุรองของการเกิดปัญหาการเกิดประกายเงิน (silver streak) 1. Consequently, weld regions have been observed to have inferior mechanical properties compared to the bulk. When this fails to happen correctly, a weld line defect occurs. 020 0. Powder injection molding comprises several processing steps, and defects may occur in each step if care is not taken. A tensile test specimen mold, which allows cavity thickness varying from 2. 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. Weld lines are visually undesirable and a plastic part is structurally weak at weld line positions. <Materials> Pre-dry thoroughly. A weld line (weld point, flow line or a knit line) forms when separate melt fronts travelling in opposite directions meet. As a result, the portion has a faint, perhaps undetectable line. In an injection molding process, a weld-line forms when two flow fronts meet each other. Weld Lines are formed when two or more molten polymer flows meet during the injection molding process. The Influence of Knit-lines on the Tensile Properties of Injection Molded Parts, Polymer Engineering and Science, 23(10): 591-596. 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. Microsyst Technol. Machine Shot Capacity – The maximum volume of resin that can be injected in a single stroke of the injection machine. Inadequate back pressure. + Increase mold temp, or materials’ temp, or holding pressure. The Factors that Cause Weld Line in Injection molding Pressure. 2. Fig 13:- Detailed view of weld lines. Wang, G. When two or more streams of plastic meet and fuse. The line where two resin flows “knit” or “weld” together during injection molding is called a weld or knit line. , Ltd. The problem with ‘weld lines. Weld Lines. In this paper, a weld line factor (W-L factor) was adopted to. A weld line is a mark left on the surface of a plastic injected molded part. 298 µm and the weld line on the heated region was almost eliminated with the aid of induction heating. Short Shot Short Shot adalah suatu kondisi dimana, plastik leleh yang akan diinjeksikan kedalam cavity tidak mencapai kapasitas yang ideal atau sesuai settingan mesin. technical ulletin SPECIALTY POLYME RS Design and Production of Injection Molding Tools. Visualization analysis of flow behavior during weld-line formation in injection molding process. (1983). Here are a few of the most common defects that may occur in plastic injection molding — and how product teams can avoid them. Wavy lines are another feature of weld lines. C. Nozzle – The nozzle is at the end of the barrel and contacts the injection mold. ABS is a commonly used plastic in injection molding due to its excellent mechanical properties and chemical resistance. You will have to confirm them before tooling. Abstract and Figures. The present work focuses on studying the effect of packing pressure on strength of stagnation weld-line. 666 Azieatul Azrin Dzulkipli and M. Failure may result due to the assembly torque, or end-use application loads (temperature, creep). See moreIncreasing the temperature of the mold or plastic material. Slow down injection speed. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. Flow analysis of the weld line formation during injection mold filling of thermoplastics. A meld line occurs when two moving melt fronts converge and flow parallel to each other. The edge gate is the most popular and straightforward injection mold gate design. Injection molding is nothing without molds. 1. This failure causes the product to be damaged during use. What Causes Weld Lines in Plastic Injection Molding Parts? I. Sink Marks Cause 4: High Mold Temperature. The optimal process condition is very likely to appear in this second part's fine-tune group. First, an injection mold with triangular inserts was built to study the influence of meeting angles on material properties at the weld line. on conventional reciprocating screw injection molding machines using molding practices standard for filled engineering thermoplastics . This gives a clue as to. Weld line is formed when two different melt flows converge, as illustrated in Fig. Star Rapid offers tips and tricks to improve your prototypes and production parts. 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. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. Weld lines can. Shaofei Jiang. The weld line refers to the process in which the liquid material is divided into two or more flows in the cavity during the injection process and merged together after a period of time [51,77,78,79]. Figure 2. Wavy lines are another feature of weld lines. Characteristic: Basically, there are PA6 AND PA66(Nylon 6 or Nylon 66), Nylon has tenacious and wearable, self-lubricious and smooth characteristics with non-toxic and antibiosis and high water absorbability. Recently, injection molding process has generated growing interest, exhibiting great potential to easily fabricate unique polymeric materials for industrial applications. In the case of PC, the model predicts satisfactorily the weld-line strength as a function of injection temperature. Injection-molding machine is the Negri Bossi VE210-1700 with screw. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection molding processing. With Ixef® PARA compounds, the strength of a weld line is typically 90 MPa (13,000 psi). Double push filling method. (3-1) Increasing the Resin Temperature at the Weld Line Section. Weld line and warping are two critical defects for injection-moulded part. In the RHCM, the mold temperature profile plays a crucial. Flow-induced filler orientation manifests in higher tensile prop-erties in the direction of flow compared to those normal to the direction of flow. 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]. 809-814. Weld lines in injection molding are a type of cosmetic defect that detracts from a plastic part’s appearance. 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. box, along the region of weld line formation (wc, wm, we and wl) and away from the weld line, in a radial position along the flow direction (R), as shown in Figure 2. In spite of the symmetry of the molding the formed weld line was not straight, due to a slight unbalance of the two injection gates. th INTRODUCTION Injection molding is one of the most 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. In our DFM report, we will analyze the possible weld lines. 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. (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. J. 000 0. As the name implies, it is usually positioned along the edge of the workpiece, forming a visible mark at the demarcating line. The main runner and sub-runner are too thin or too long. technical ulletin SPECIALTY POLYME RS Design and Production of Injection Molding ToolsWeld lines have been one of the common defects puzzling the injection molding industry. 5. Crack growth behavior. Cracking and/or Crazing can be defined as a fracture or surface breakage in the material of a molded part, usually found in weld line areas, but also on the surface in general. However, even with advanced technologies and precise control, the process is not without its challenges. Penyebab Weld Line. Weld lines appear as a result of the flow of molten plastic during the injection molding process. Learn how to avoid them and what injection molding companies do to prevent them. 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. 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. Investigate for potential contamination. The optimum injection molding parameters to manufacture the product was determined by . poor flow fronts that are too cold, this can also lead to a deterioration in the mechanical properties. Plastics manufactured by injection molding are meant to be durable and reliable, able to hold up to heavy use, high temperatures, or adverse conditions. Weld line (also known as a knit 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 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). The wheel has to be gated at three places on the hub and. 21: Weld line failure caused by hoop stresses. Our weld line injection molding is essential for the best result of finished molded products. The choosing optimal gate location technique has been developed to set weld lines as far as possible from the region of maximum stresses. 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. Injection molding could be applied with many polymer materials, such as. Weld lines can significantly reduce ultimate tensile strength (UTS) and fracture strain of talc filled polypropylene (PP). The gate location should enable the two flow fronts to merge easily and continue to flow beyond the weld line. Its appearance can be improved by adjusting parameters. An injection molding gate is the designed opening in a mold through which molten plastic is introduced into the mold cavity, initiating the process of taking the shape of the desired part. injection molding. They. Emerging Materials Research. According to the characteristics. The type of resin used during injection molding plays a large role in whether or not a knit line will be present. Weld Lines-3 Ways for Detecting and Correcting. The cracking was always located in the weld/knit line and therefore caused by weakness in the bonding of the plastic at. It is possible to pre. In this study, one injection mold. 1, right). In this regard, the plasticizing ability of the plastic injection moulding machine should be checked. Article Google Scholar Deng YM, Zheng D, Lu XJ (2008) Injection moulding optimization of multi-class design variables using a PSO algorithm. Three terms that often get mixed up in injection molding are weld, meld and knit lines. This may require higher melt temperature or lower injection speed . After that, the compounds were injection-molded into tensile samples with and without weld lines to. Injection Molding Glossary; Weld Lines; Weld Lines. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. Wu CH, Liang WJ (2005) Effects of geometry and injection-molding parameters on weld-line strength. <Mold> Increase (or decrease) the size of the runners and gates. This type of injection molding resolves any trouble caused by undesired welding lines. 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. Mold flow analysis can predict the location of weld lines. In the present work, the micro specimens were investigated. 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. 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. Weld Line Factors for Thermoplastics. 025 100 120 140 160 180 200 220 240 Mold Temperature (F) LDPE PPAbstract. One common issue that frequently arises during injection molding is the formation of weld lines. Weld line existence reduces the material strength; however, its demerit characteristics. Slow down injection speed. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. Because of the ever-increasing requirements for parts performance, lots of researchers have perf. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. 2007; Lotti et al. 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. 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. 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. If the different flow fronts have cooled. 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. Microsyst Technol, 14 (6) (2008), pp. Just check out some of it on the above lists. Information about PA6/PA66 (Nylon) Injection Molding. Consultant @ Effinno Technologies, BSME, MBA - Bridge between Plastics Injection Molding Knowledge and Practice. This model provides the necessary information. Increase the mold temperature. Avoid knit lines when designing a molded part to improve cosmetic appearance and functionality. There are several possible causes that need to be investigated to troubleshoot weld lines in injection molding. They can affect the strength and appearance of the part, depending on the temperature, pressure, speed, and mold design of the injection molding process. In this experiment, several ejector. Increase the injection speed to reduce the amount of cooling happening in the mold. 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. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. (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 Solutions for Poor Welding Lines. 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. Weld lines in injection molding are a type of cosmetic defect that detracts from a plastic part’s appearance. 6. 2002), the use of simulation approaches (Berti and. 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. Usually it’s a straight line, and often to be found radiating away from a hole, inclusion or other such part feature. 5. 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. + Adjust injection speed. Weld line strength is important in blow molding as well as injection molding. Weld lines are a common occurrence in injection molding that affects the overall quality and strength of a finished product. 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. Figure 1a illustrates how the weld line is produced when two melt streams merge during the final filling process. 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. Remedies: Raise the temperature of the mold or molten plastic. These flow fronts occur when the molten plastic material encounters obstacles, such as inserts, ribs, or other features within the mold cavity. Sink Marks Cause 3: Improper Pack or Hold Pressure. Compd. Plastic part design for injection molding – An introduction. Physics. Five injection molding process parameters, including mold temperature, melt temperature, packing pressure, injection. Xie L, Ziegmann G (2008) A visual mold with variotherm system for weld line studying micro injection molding. 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. 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. Change the gate locations. Criens, R. For this purpose, the width of the weld line calculated by Sigmasoft is. They happen when two flow fronts of melted plastic meet and solidify, leaving a visible line on the surface of the part. Injection molding can be performed with only one of these materials like glass, plastics, etc. This is a video excerpt from our Problems & Solutions Course - Weldlines. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. This gives a clue as to how it was formed. Some of the approaches include the application of machine learning methods (Chen 2008; Manjunath and Krishna 2012; Kuo et al. This study focus on the. Ejector System (Pötsch, 1995) . 000 0. com1. 2017-01-0481. 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. 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. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. Nguyen-Chung. Strength at weld the line location and warpage problem in injection molding plastic component were not new problems in injection molding industries. Description Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. Weld lines in injection molding occur when two flow fronts meet and create a visible line on the surface of the molded part. This paper presents the. 2. Various measures are taken at production sites to address these problems. Compd. 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. Methodology. Alloys. 32–24. Weld lines, also known as knit lines, are a common defect in injection molding where two or more flow fronts of molten plastic meet but don’t properly fuse together. Figure 1 below shows the development of a weld line. Increase the injection speed. Plastic part design for injection molding – An introduction. Unless you are manufacturing an extremely simple part with one gate and a unidirectional flow front, your part will have weld lines. Venting at Weld Lines. Here is a look at the differences between them, the causes of meld and knit line imperfections, and their impact on part durability. 18/06/2021. Here are some strategies. <Materials> Pre-dry thoroughly. The impact behavior of weld-lines in injection molding. Therefore, it is recommended to do a moldflow study prior to the mold being built. Wolfgang Homes, head of the applications department of Eurotool, a manufacturer of hot runner systems, clarified the two methods for IMI, noting that. A meld line is defined as the re-merging of two flow fronts. when two or more melt flow fronts contact each other immediately after the cooling process. 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. In the heating step, the heatingOverview of the injection molding process. 9. However, research about the computer determination of weld lines in injection molding remains scarce. 2012. Low mold temperatures are usually employed to decrease cycle molding time and final process costs; however, resulting surface defects include weld lines, sink. 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. 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. 226-233. These lines can occur due to variations in wall thickness, gate location, or the geometry of the part. 3. In this study, the effects of injection temperature, injection pressure, and fiber cont. Polym Eng Sci 45(7. As such, optimizing mold designs should always be incorporated in your production model. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. 7 of the reference. Adjust the design for the flow pattern to be a single source flow. Weld lines Weld lines are weak areas formed by converging flows of plastic that can lead to mechanical part failure if not properly accounted for in the part design. 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. 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. 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. 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. Processing OptimizationReduced frozen skin thickness: High injection speeds also contribute to a thinner frozen skin at the weld line. Fracture behavior of weld lines in injection molded components loaded under real operating conditions. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. Kagitci YC, Tarakcioglu N (2015) The effect of weld line on tensile strength in a polymer composite part. This is expected to achieve maximum results while the pressure holding effect will also increase. These lines can occur at the gate location, where the plastic enters the mold, or anywhere along the flow path. (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. org or visit 80-ton Victor injection molding machine, equipped with an accumulator capable of delivering maximum flow rate of 138 cm 3 /s and providing maximum injection pressure of 210 MPa, is utilized for experiments. Miron MC, Major Z, Adachi T. Weld lines can be caused by several different problems: Low temperature of injection moulding machine barrel. A poor knit line can cause only cosmetic blemishes or it can significantly weaken the structural integrity of a part. Park et al. As a defect of micro injection molding parts, weld line is unfavorable since it will influence the surface quality and mechanical properties of micro parts. 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. Fortunately, there are several. This study presents an innovative approach to enhancing weld line strength in advanced polymer injection molding through applying gas-assisted mold temperature control, significantly increasing mold temperature beyond typical values observed in conventional processes. 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. Meld and knit lines are actually both different types of weld lines. 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. Boost time too long Shorten boost time, lower boost pressure, or move transfer to an earlier position . Materials Science. Weld lines can compromise the strength and aesthetics of the part, so it’s important to carefully design the mold and. The appearance quality of plastic parts in weld lines can be improved significantly through the rapid heating cycle molding (RHCM). Injection molding is a complex multi-variable, nonlinear and time-varying unsteady process, which makes it more difficult to optimize the process parameters. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. – Use generous and even. Known also as knit lines and weld marks, weld lines are difficult to eliminate completely, especially if your injection molded part requires holes. This occurs mainly in the presence of barriers that divide the melt flow in. Injection molding weld lines where two or more flow fronts come together in the mold. Fiber content dependence on. 1. As the weld line can significantly lower the mechanical strength of µIM parts, it is relevant to clarify the position of weld. Molding with weld line model Moldex3D was used for calculate the molding of lugs (figure 1). This injection molding defect appears as a black discoloration on the surface of the molded part. For thick-walled parts, slow injection rates result in more uniform polymer distribution . 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. 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]. This results in a region of a different level of molecular entanglements than the bulk material. This principle has been implemented on a complex component in the case of the spring-loaded cogwheel shown in Figure 5, for instance. Insufficient clamp tonnage Increase clamp pressure or move to machine with more tonnage . Meld Lines. According to the weld line distribution map of six gate schemes shown in . 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 injection molding troubleshooting. The position, length, and angle of weld lines are dependent on the. Edge Gates. Ada berbagai penyebab mengapa weld line bisa muncul pada permukaan produk plastik. These are caused by the shot of molten plastic moving at different speeds throughout the injection. 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. อุณหภูมิของพลาสติกเหลวสูงเกินไปจนก๊าซหรือความชื้นแยกตัวออกมาได้. Plastic part design for injection molding – An introduction. 1. When two or more strands of molten plastics meet in the mold, a weld. [ 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. Usually it’s a straight line, and often to be found radiating away from a hole, inclusion or other such part feature. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. It occurs when melting plastic material is injected into a mold, it flows through all parts of th. Plastic Injection Molding Process. How to Reduce Weld Line in Injection Molding? Weld lines are a common issue that occurs in injection molding. Weld line usually is not allowed on some critical area, and weld line on the part also weaken the strength. With Ixef® PARA compounds, the strength of a weld line is typically 90 MPa (13,000 psi). The need to minimize fiber breakage, plus the higher viscosity of materials with. It is a zone with reduced mechanical properties negatively influencing on the molding behavior in exploitation. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. Here we are looking at most common part defect that can come from injection molding called 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. 2. Therefore, the investigation on the developing process of weld line would be a significant issue for improving the quality of micro injection molded parts. 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). 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. The second technique, cascade injection moulding, can produce parts free from weld lines. This can allow the. Investigations on WLs in micro injection molded parts were performed in Refs. Weld Line Factors for Thermoplastics. 3. oped which factors the weld lines into the virtual design of chopped-strand-rein-forced thermoplastic parts. 5. 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. une, 13: 15. A visible weld line is observed, due to a combina-The Weld line result itself has a scale associated with the placement of the weld line that is directly relative to how severe the weld line will be based on the angle in which the two flow fronts meet. [ 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. Jiquan Li, Taidong Li, +1 author. 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]. ”Weld Lines in a plastic cover. Joe Henz is a chemical engineer with 30 years of experience in the plastics industry, primarily with GE. T he decreased gloss level at the position of. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. 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]. Thereby creating localized pressure within the mold. 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. In narrow fields, a limited amount of molten liquid can solidify and block the flow. That’s the air escaping out of the nozzle until the hose is full of pressurized water. Controlling the mold’s temperature could also minimize the weld line’s effects.