Weld lines often generate mechanically weak areas, because of the unfavorable perpendicular orientation of the macromolecules, fibers and/or other fillers to the direction of the main flow. 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. A simulation of mold filling with multi-inlets or an insert in the cavity is pursued with an improved Level Set Method. Neat polypropylene retains nearly 90% of its strength on a properly designed and molded weld line. 2. Plastic Injection Molding Process. . Shaofei Jiang. It provides scientific basis for designers toWeld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of injection‐molded parts. In an injection molding process, a weld-line forms when two flow fronts meet each other. Cited by (41) Effect of mould surface roughness adjustments to increase the flow path length in the injection moulding process. 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. Conventional injection molding is widely used to produce plastic parts, mainly in the automotive industry, due to the high production ratios and quality of. J. This study focuses on the effect of melt temperature on. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. Flow analysis of the weld line formation during injection mold filling of thermoplastics. Injection Molding Glossary; Weld Lines; Weld Lines. Injection Molding Glossary; Weld Lines; Weld Lines. Venting at Weld Lines. on conventional reciprocating screw injection molding machines using molding practices standard for filled engineering thermoplastics . Inadequate back pressure. 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. S. Penyebab Weld Line. 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. 2007; Lotti et al. when two or more melt flow fronts contact each other immediately after the cooling process. Weld Lines-3 Ways for Detecting and Correcting. Weld lines are formed when there is an inability of two or more flow fronts to ‘knit’ or ‘weld,’ together during the molding process. Meld and knit lines are actually both different types of weld lines. The impact behavior of weld-lines in injection molding. Three terms that often get mixed up in injection molding are weld, meld and knit lines. Weld Line defect analysis, the most common of many defects in injection moulding products. Its appearance can be improved by adjusting parameters. Weld line formation in the injection molding process occurs. of micro injection molding process simulation by technology update and progress. Examples of such failure are shown in Figure 1. For glass-filled grades, the thickness at the weld line can be slightly larger than the nominal value due to lower shrinkage associated with vertical fiber orientation at the weld line cross. This model provides the necessary information. 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. Flow marks in injection molding can be avoided if adequate measures are taken. The impact behavior of weld-lines in injection molding. A weld or meld line is a weakness or visible flaw created when two or more flow paths meet during the filling process. 21: Weld line failure caused by hoop stresses. In addition, its tensile strength and stiffness will be sharply decreased. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. Try to gradually raise the mold temperature and barrel temperature. Weld Lines. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. The gate location should enable the two flow fronts to merge easily and continue to flow beyond the weld line. Ideally, the resin flow will split into two flow fronts to pass around the obstruction and then recombine into a single flow front. Injection molding could be applied with many polymer materials, such as. 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. 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. Weld lines are among the most critical structural defects in parts made by the injection molding of fiber-reinforced thermoplastics, explained Sirmax in a press release. To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. Insufficient injection pressure and speed can cause weld lines. This customary mark is caused by differential rates of cooling in the resin where. in the cavity of the injection mold. 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. 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. 22 shows how the weld lines are formed when the melt splits around core pins during the injection molding process. Int J Adv Manuf Technol 52:131–141. If you turn on the spigot to a garden hose, you will hear a hissing sound at the nozzle end for the first few seconds. Tekanan yang kurang mampu untuk mendorong aliran dan kembali pada posisi semula dapat menimbulkan weld line. Key words: weld line strength, thermoplastic composites, injection molding, wall thickness, skin and core layers Department of Materials Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900, Thailand. Again, consult with professionals as to how you could improve mold designs. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. 32–24. 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. Molding Equipment. In this blog post, we will explore the causes of weld lines in. It occurs when melting plastic material is injected into a mold, it flows through all parts of th. 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. 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]. In this study, one injection mold. This study describes how the weld line was formed on the part. Weld lines can be caused by many reasons, which covers the various aspects of mold, process, raw materials and product design, etc. These lines can weaken the strength of the part, and they can also be unsightly. Avient’s Zachary Alderman shares practical tips on designing and injection molding parts utilizing short-fiber reinforcements. It is important to investigate the weld line because the weld line area can induce potential failure of structural application. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. 666 Azieatul Azrin Dzulkipli and M. They are unavoidable even for moderate complex products. Kagitci YC, Tarakcioglu N (2015) The effect of weld line on tensile strength in a polymer composite part. Azuddin / Procedia Engineering 184 ( 2017 ) 663 – 672 Fig. 3. The tensile stresses of the weld lines with ultrasonic functions are 8. We'll show you how. 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. อุณหภูมิของพลาสติกเหลวสูงเกินไปจนก๊าซหรือความชื้นแยกตัวออกมาได้. (1998) for clear photographs. The impact behavior of weld-lines in injection molding. Effects of fillers and/or reinforcements on weld-line strength of nylon 6/6. The Factors that Cause Weld Line in Injection molding Pressure. This can occur when a polymer flow splits to go around an interruption (e. Investigate for potential contamination. 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. Minimize the use of release agent. Meld lines are formed when two separate flow fronts meets. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. 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. Expand. as warpage, shrinkage and weld line of the plastic parts. 5. – Use generous and even. Fracture behavior of weld lines in injection molded components loaded under real operating conditions. Weld lines, generated during injection molding, can significantly reduce the mechanical performance of structures. 4. 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. 3 and 53. Double push filling method. Therefore, it is recommended to do a moldflow study prior to the mold being built. Polyamide 6 (Lanxess, Durethan B 30 S 000000, non-reinforced, ISO 1874-PA 6, GR, 14-030, Cologne, Germany) was used for this experiment. They. poor flow fronts that are too cold, this can also lead to a deterioration in the mechanical properties. This failure causes the product to be damaged during use. The second technique, cascade injection moulding, can produce parts free from weld lines. 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. 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 injected. 1. 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. Fisa et al. Strength measurements should be made to. This paper presents the. NX Mold Flow Analysis. Weld-line is a weak area which reduces the strength of the part locally. JENIS-JENIS DEFECT (CACAT) PADA PRODUK INJECTION MOLDING PT. 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). 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. In an injection molding process, a weld-line forms when two flow fronts meet each other. 2. A knit line may be unnoticeable or may look like a crack. Install an ultrared light inside the hopper. The gate is the critical bridge between the runners (the channels through which the molten plastic travels) and the actual mold. Increase the injection speed. The Solutions for Poor Welding Lines. In an injection molding process, a weld-line forms when two flow fronts meet each other. technical ulletin SPECIALTY POLYME RS Design and Production of Injection Molding Tools. Polyamide-6 (PA-66) was used as. 005 0. The welding angle can be used to differentiate weld lines and meld lines. Kondisi ini juga bisa menandakan bahwa mesin injection. 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. If the different flow fronts have cooled. สาเหตุการเกิด weld line คือเมื่อการไหลของพลาสติกมาประสานกันนะจุดใดจุดหนึ่งและจุดนั้นเกิดความแตกต่างของอุณหภูมิในสองทิศทางการไหลจะทำให้เกิด. We recently had a few pieces (2-3%) crack after assembly, while in storage (not installed, still in the package). Flow-induced filler orientation and weld lines are un-avoidable facets of the injection molding process. Insufficient plasticizing ability of injection molding machine. 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. This method was adopted. With Ixef® PARA compounds, the strength of a weld line is typically 90 MPa (13,000 psi). For multiple gate and complex part. Weld line existence reduces the material strength; however, its demerit characteristics. The thermo-rheological findings were used to investigate the sources of weld line weakness. The schematic diagram of a weld line formation is illustrated in Figure 7, where is the welding angle of two melt fronts. Plastic part design for injection molding – An introduction. Flashes, 3. 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. 1. 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. Plastic part design for injection molding – An introduction. When two or more strands of molten plastics meet in the mold, a weld. Insufficient plasticizing ability of injection molding machine. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Adjust the design for the flow pattern to be a single source flow. A flow mark is commonly referred to as a flow line occurs during the process of injection molding. Weld lines in injection molding are a type of cosmetic defect that detracts from a plastic part’s appearance. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection molding processing. Plast. 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. Adjust the design for the flow pattern to be a single source flow. Weld line Weld line dikatakan ketika dua atau lebih aliran lelehan depan. When an external load is applied to a weld line region, the part’s potential for mechanical failure is increased. This paper evaluates the shrinkage and strength of weld line using Design of Experiment and Response Surface Methodology in multi-objective optimisation utilising the injection moulding parameters. This line does not normally impact the overall shape or dimensions of the item. 015 0. Article Google Scholar Deng YM, Zheng D, Lu XJ (2008) Injection moulding optimization of multi-class design variables using a PSO algorithm. Thus, it is important to understand (i). and most commonly, thermoplastic polymers are used. 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]. The next type of injection molding defect is ‘Weld Lines’. Wu CY, Ku CC, Pai HY (2011) Injection molding optimization with weld line design constraint using distributed multi-population genetic algorithm. How Are They Formed? Molten plastic resin is injected into a mold cavity through an opening known as a gate. Processing OptimizationReduced frozen skin thickness: High injection speeds also contribute to a thinner frozen skin at the weld line. Ejector System (Pötsch, 1995) . Injection pressure or. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. Save. Bubbles are caused by melting flow fronts colliding in a mold cavity. 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 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. 2. Here we are looking at most common part defect that can come from injection molding called weld line. In this study, the effects of injection temperature, injection pressure, and fiber cont. During injection moulding, a weld-line occurs when two or more flow fronts collide in the hollow cavity. 1. Poor weld line Ⅰ. The need to minimize fiber breakage, plus the higher viscosity of materials with. The utility model relates to a mold structure capable of eliminating the appearance of weld lines of a hole. In some cases, a weld line can also cause a loss of strength and impact resistance. Wolfgang Homes, head of the applications department of Eurotool, a manufacturer of hot runner systems, clarified the two methods for IMI, noting that. The present work focuses on studying the effect of packing pressure on strength of stagnation weld-line. Here are a few of the most common defects that may occur in plastic injection molding — and how product teams can avoid them. The. Ozcelik studied the influence of the injection parameters and weld line on the mechanical properties of polypropylene (PP) during IM process via the design of experiment (DOE). Weld line usually is not allowed on some critical area, and weld line on the part also weaken the strength. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. In the first, sequential injection moulding, the lines are displaced to noncritical areas of the moulding. In this paper, two different injection molding tests were completed. are very minimum. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. 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. 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]. Fracture behavior of weld lines in injection molded components loaded under real operating conditions. Visualization analysis of flow behavior during weld-line formation in injection molding process. 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. , Ziegmann G. The molded plastic part may also appear to be rust-colored. Effect of geometry and injection-molding parameters on weld-line strength. The microstructure of weld lines is clearly observed from the micrographs. 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. 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. A meld line is defined as the re-merging of two flow fronts. In the 1947 book, Injection Molding of Plastics, the late Dr. 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. Figure 1 a illustrates how the weld line is produced when two melt streams merge during the final filling process. Weld lines in injection molding are frequently unavoidable. 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. In. In recent years new methods for quality prediction and optimization of the injection molding process have been proposed and applied. 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. Ada berbagai penyebab mengapa weld line bisa muncul pada permukaan produk plastik. The Influence of Knit-lines on the Tensile Properties of Injection Molded Parts, Polymer Engineering and Science, 23(10): 591-596. 2. Weld line reduction is one of the major concerns in plastic injection molding (PIM) that results in high surface appearance and high strength of a plastic product. 2011; 509 (2):226–233. 5 mm, 1. This occurs mainly in the presence of barriers that divide the melt flow in. One solution is to prevent the weld lines from forming in regions that are. Procedia Mater Sci 2014; 3: 2048–2053. Weld-line is a weak area which reduces the strength of the part locally. This injection molding defect appears as a black discoloration on the surface of the molded part. It is possible to pre. Article Google Scholar Xie L, Ziegmann G (2009) Influence of processing parameters on micro injection molded weld line mechanical properties of polypropylene (PP). Effects of mold temperature and pressure on shrinkage 0. 015 0. th e use of design of e xperiment techniq ue. It has larger cross-sectional regions that allow sufficient molten plastic flow into the cavity. Equipment. According to the characteristics. 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. Although they often cannot be avoided it’s possible to minimize their cosmetic effects to an acceptable degree through careful product design and. Weld-line is a weak area which reduces the strength of the part locally. A poor knit line. ac. 3. Flow front tracing simulation results for weld line developing process in micro injection molding with Comsol ® Multiphysics 3. That helps. 010 0. 2020-01-1306. 8. 7 in Kobayashi et al. Except for a few very simple injection molded parts, they occur on most injection molded parts (typically in the form of a line or V-groove), especially large complex items that require use of multi-gate molds and inserts. The relative weld-line strength is defined as the ratio of the strength of specimens with a weld line and a comparable sample with the same geometry but without the weld line, and this measure mainly depends on the molding conditions, such as melt temperature, mold temperature, and injection pressure [8]. A weld line is a visible seam where two areas of the molten plastic meet. 2 mm to 1. 0 mm, is designed to conduct the. Fortunately, there are several. 005 0. If weld lines are unavoidable due to multiple gates in a moulding, they should be positioned in the non-critical region. 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. This article will introduce you the usage, types, and advantages of the Sequence Injection Timer. This paper presents the. Weld line additionally called as knit line, is a defect that occurs when the injected plastic meets within a. 2004; To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. Burn Marks. He now teaches courses in injection molding and plastic part design at the Polymers Center of Excellence and UNC-Charlotte in Charlotte, N. Published 5 July 2019. [1] Kobayashi et al. 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. If the plasticizing ability of the plastics injection molding machine is insufficient, the plastic. 7 of the reference. In this regard, the plasticizing ability of the plastic injection moulding machine should be checked. This failure causes the product to be damaged during use. Injection moulding (U. The Solutions for Poor Welding Lines. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. Google Scholar | Crossref | ISI. Sequential valve gate technology. Consequently, it causes viscous dissipation which leads to the generation of heat. For thick-walled parts, slow injection rates result in more uniform polymer distribution . Wang, G. 809-814. Keywords: Flow behavior , Injection molding , Particle tracking , Visualization , Weld-line Article MetricsSimulations and experiments were conducted with gas temperatures of 200–400 °C to investigate the impact of external gas-assisted mold temperature control (Ex-GMTC) on the quality of weld line of molding products. The three parameters affecting operation were called injection pressure, injection time, and packing pressure which influence the quality of weld line. A new kind of weld line was. Xie L. From Understanding Weld-line Integrity by Sabic Innovative Plastics, p. 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. In this regard, Taguchi orthogonal experimental design is adopted, and five processing parameters, the mold temperature, melt temperature, cooling time, packing. 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. Figure 2. Fellahi et al. In the end, the total amount of time that running a complete Taguchi DOE (L18) to occupy an injection. Redesign the mold to prevent the weld line. Weld Line Factors for Thermoplastics. <Mold> Increase (or decrease) the size of the runners and gates. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. The main types of injection molding defects are: 1. Causes. 2-1. In this study, one injection mold. Introduction. But none of the current packages can predict weld lines’ properties qualitatively. Weld lines may appear like seams or scratches, but that is not what they are. Below is one of the examples: !NOTE: if the weld lines is important to the cosmetic surface of your part, please bring this up to your mold maker during quoting phase. The optimum injection molding parameters to manufacture the product was determined by . Therefore, the investigation on the developing process of weld line would be a significant issue for improving the quality of micro injection molded parts. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. 2. From: Polylactic Acid (Second Edition), 2019. Some of the common fixes for weld lines include: Increase the resin temperature to ensure both sides of the weld line are liquid when colliding. Five injection molding process parameters, including mold temperature, melt temperature, packing pressure, injection. Micro injection molded polymeric parts coated with functional thin films/layers show off the promising applications in microsystems area. 2. These are caused by the shot of molten plastic moving at different speeds throughout the injection. 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. Increase the injection speed. The thermo. Participating in DFM and mold flow analysis is a good way to achieve this. This paper presents the. Adding vents, using overflows, or using porous metal. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. C. Lugs size is 65 х 24 х 4 mm. Thoroughly clean molding machine cylinders. In the heating step, the heatingOverview of the injection molding process. Mechanical properties of the weld line defect in micro injection molding for various nano filled polypropylene composites. Weld-line, a common occurrence in plastic injection moulding, is a representative defect compromising mechanical qualities and product appearance [16]. (3) Adjust the temperature of the barrel and nozzle: the viscosity. The weld lines that occur in injection mouldings are critical areas on which depends on the strength of the mouldings. A weld line can appear during the absence of enough pressure to push the plastic flow and then meld. * Corresponding author, e-mail: fengsjpc@ku. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. Therefore, it is recommended to do a moldflow study prior to the mold being built. warpage, and weld line. Three terms that often get mixed up in injection molding are weld, meld and knit lines. Weld Line defect analysis, the most common of many defects in injection moulding products. This study focus on the. Which means engineers need to know how to account for this phenomenon in an efficient way. Ideally, the resin flow will split into two flow fronts to pass around the obstruction and then recombine into a single flow front. Injection molding. C. Low mold temperatures are usually employed to decrease cycle molding time and final process costs; however, resulting surface defects include weld lines, sink. Weld lines can lower the integrity of the part. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. Steven. This reduced thickness of the frozen skin further enhances the visual appeal of the. 2021年4月23日 / by admin. 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. Injection molding is a highly versatile manufacturing process used to produce a wide range of plastic products with precision and efficiency. Investigations on WLs in micro injection molded parts were performed in Refs. The weld line in injection molding is created when two melt streams connect, as shown in Figure 1. This is expected to achieve maximum results while the pressure holding effect will also increase. Sink Marks Cause 1: Incorrect Melt Temperature. The diameter of the hole is 12 mm. 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. A weld line is a mark left on the surface of a plastic injected molded part. 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. Threadline gap in-between part due to improper gate location in complex design parts including excess of holes (multipoint. 000 0. According to the weld line distribution map of six gate schemes shown in . [ 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. As such, optimizing mold designs should always be incorporated in your production model. 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. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. 1. [ 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. In this lesson we will focus on the meld and weld lines. Injection molding weld lines where two or more flow fronts come together in the mold. In recent years, researchers have. <1> As illustrated in Figure 4, the existence of. 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. In this paper, a weld line factor (W-L factor) was adopted to. 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. One of the factors that determines the quality of injection molded parts is the weld line [50,75,76]. Weld lines can be caused by several different problems: Low temperature of injection moulding machine barrel.