In our DFM report, we will analyze the possible weld lines. Weld line formation in the injection molding process occurs. Weld lines in injection molding are a type of cosmetic defect that detracts from a plastic part’s appearance. – Use generous and even. 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. 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. 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. 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. The gate is the critical bridge between the runners (the channels through which the molten plastic travels) and the actual mold. As a result, the portion has a faint, perhaps undetectable line. This is expected to achieve maximum results while the pressure holding effect will also increase. Munich, Germany: Carl Hanser Verlag, 1994. * Corresponding author, e-mail: fengsjpc@ku. 2021年4月23日 / by admin. The injection molding gate generates heat by dissipation. Weld lines are formed when two melt fronts come in contact with each other. Despite injection molding being recognized as a robust process for obtaining parts with high geometry accuracy, one last occurrence remains a challenge in micro-injection molding, especially when junctions are. Weld lines represent the region where two separated melt fronts recombine. These lines can occur due to variations in wall thickness, gate location, or the geometry of the part. In this paper, a weld line computer determination method based on filling simulation with surface model is proposed, from which the positions and lengths of the weld lines can be predicted. Polymer Engineering and Science (2005) There are more references available in the full text version of this article. 2011; 509 (2):226–233. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. What Causes Weld Lines in Plastic Injection Molding Parts? I. 2 mm to 1. Voids and bubbles, 6. 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. A weld line is a mark left on the surface of a plastic injected molded part. Learn more about ABS injection molding here. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. Weld lines can compromise the strength and aesthetics of the part, so it’s important to carefully design the mold and. , a post that forms a hole) and then rejoins, or when polymer melt fronts meet, from multiple injection points. Designers can easily set up and perform analysis with only a few clicks. Injection molding. Weld Lines and Fibers There are two basic types of weld lines: the stagnant and the flowing [1]. But the unfavorable and unavoidable defect of weld line in micro injection molding part leads to detrimental mechanical and surface properties. Weld lines may appear like seams or scratches, but that is not what they are. 0 mm, is designed to conduct the. This failure causes the product to be damaged during use. Micro injection molded polymeric parts coated with functional thin films/layers show off the promising applications in microsystems area. JENIS-JENIS DEFECT (CACAT) PADA PRODUK INJECTION MOLDING PT. Again, consult with professionals as to how you could improve mold designs. Wavy lines are another feature of weld lines. 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. 1. Try to gradually raise the mold temperature and barrel temperature. Weld line strength vs. The schematic diagram of a weld line formation is illustrated in Figure 7, where is the welding angle of two melt fronts. Gate position in injection mold. 2002), the use of simulation approaches (Berti and. 3. weld lines in infill analysis of injection molding simulation was observed [5]. Wu CH, Liang WJ (2005) Effects of geometry and injection-molding parameters on weld-line strength. 6. Weld line section presents notch or gloss difference. Weld line Weld line dikatakan ketika dua atau lebih aliran lelehan depan. 2-1. identi fy a s urface defect i n th e for m of a weld line, which occurs due to the two injection points at x = 5 mm and 34 mm ( see Fig. th INTRODUCTION Injection molding is one of the mostWeld lines have been one of the common defects puzzling the injection molding industry. This may require higher melt temperature or lower injection speed . They occur when melt flow fronts collide in a mold cavity. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. 2. Weld-Line in an injection molded part develops when two or more melt fronts are converged together. Xie L, Ziegmann G (2008) A visual mold with variotherm system for weld line studying micro injection molding. Consequently, weld regions have been observed to have inferior mechanical properties compared to the bulk. Adjust Injection Molding Parameters: Optimizing injection speed, pressure, and temperature can help ensure better melt flow and reduce the likelihood of weld line formation. A weld line can also be called a knit line. We investigate the effects of various heating times and. 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. Weld Line defect analysis, the most common of many defects in injection moulding products. 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. Poor weld line quality can lead to short-term or long-term product failures, initiated at the weld line. A weld line is often unavoidable. There are several possible causes that need to be investigated to troubleshoot weld lines in injection molding. In the sense that the weld line is better formed before the resin temperature. Sink marks, 2. With Ixef® PARA compounds, the strength of a weld line is typically 90 MPa (13,000 psi). If the different flow fronts have cooled. In this mold, a visualization design and a rapid heating/cooling system were integrated, and specimens with different cross section. ). Here are some reasons why design is important for injection molding. Thereby creating localized pressure within the mold. Adjust the design for the flow pattern to be a single source flow. Gava and co-workers implemented an investigation devoted to the de-weld lines in injection molded thermoplastic composites. ” Weld Lines in a plastic cover. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. Sink Marks Cause 4: High Mold Temperature. Improper fusion of two fluid flows, a state before weld line. This article will introduce you the usage, types, and advantages of the Sequence Injection Timer. Or, the part where the weld line is produced shall. open access Abstract Micro weld lines are the common problem that occurs for plastic molded parts through injection molding process. This weld line can act as a weak spot in the material. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. 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]. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. Injection molding can be performed with only one of these materials like glass, plastics, etc. 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. The wheel has to be gated at three places on the hub and. Its appearance can be improved by adjusting parameters. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. They are the result of fundamental physical effects taking place inside of the mold tool cavity. Fracture behavior of weld lines in injection molded components loaded under real operating conditions. Weld line strength is important in blow molding as well as injection molding. Change the gate locations. 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. 5. . A quantitative evaluation of the appearance quality of weld lines in RHCM parts. 2. 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. Maintain a holding pressure that is no more than 1/2 the. Usually it’s a straight line, and often to be found radiating away from a hole, inclusion or other such part feature. Tekanan yang kurang mampu untuk mendorong aliran dan kembali pada posisi semula dapat menimbulkan weld line. Weld lines occur when melt flow fronts meet during the injection molding of plastic parts. The need to minimize fiber breakage, plus the higher viscosity of materials with. In manufacturing, the Weld line or Knit line or Meld line is the line where two flow fronts meet when there is the inability of two or more flow fronts to "knit" together, or "weld", during the molding process. 2. 5. Investigations on WLs in micro injection molded parts were performed in Refs. If it only affects the appearance, it can change the position of the burn four to change the position of the weld line. 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. Try to gradually raise the mold temperature and barrel temperature. Adding vents, using overflows, or using porous metal. Plast. Threadline gap in-between part due to improper gate location in complex design parts including excess of holes (multipoint. Set up the process overflow and use it as the place where the weld line is generated, and then cut off and remove it after forming. Article Google Scholar Deng YM, Zheng D, Lu XJ (2008) Injection moulding optimization of multi-class design variables using a PSO algorithm. (1998) for clear photographs. This occurs mainly in the presence of barriers that divide the melt flow in. 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. The microstructure of weld lines is clearly observed from the micrographs. 2-1. T. Mobile 0813; Shinko Sellbic Co. 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. The impact behavior of weld-lines in injection molding. 2004; To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. The impact behavior of weld-lines in injection molding. The next type of injection molding defect is ‘Weld Lines’. 2. 1. This study addresses the effects of injection molding weld line on the fatigue crack resistance of commercial CPVC in the temperature range of −10 to 70 °C. Save. 030 0. Injection pressures too high Reduce pressure . 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. Lugs size is 65 х 24 х 4 mm. In. Figure 1a illustrates how the weld line is produced when two melt streams merge during the final filling process. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. Steven. Clamping Unit. When two or more streams of plastic meet and fuse. This reduced thickness of the frozen skin further enhances the visual appeal of the. injection molded pipe-fittings with and without weld line. Insufficient injection pressure and speed can cause weld lines. Star Rapid offers tips and tricks to improve your prototypes and production parts. 4 at different time steps (legend scale is volume fraction of. 8. 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. , Ltd. Avient’s Zachary Alderman shares practical tips on designing and injection molding parts utilizing short-fiber reinforcements. The effects of fiber concentration has been studied in detail. Plastic injection molding is a versatile and efficient way to produce durable, detailed parts of endless sizes, shapes, and purposes. Abstract and Figures. Meld and knit lines are actually both different types of weld lines. One solution is to prevent the weld lines from forming in regions that are. C. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. He now teaches courses in injection molding and plastic part design at the Polymers Center of Excellence and UNC-Charlotte in Charlotte, N. 005 0. The default weld line result recognizes 135º as the maximum angle of collision and as that angle decreases, the severity increases as it. 2. These master batches and PP pellets were dry-blended by adjusting the ratio such that the fiber contents were 10, 20, and 30 wt%. 5. Weld lines can be caused by several different problems: Low temperature of injection moulding machine barrel. 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). 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 gate location should enable the two flow fronts to merge easily and continue to flow beyond the weld line. In this paper, a weld line factor (W-L factor) was adopted to describe the. 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. 9 – Over Packing. Weld lines in injection molding occur when two flow fronts meet and create a visible line on the surface of the molded part. [ 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. Many works deal with weld lines and their dependence on processing parameters for conventional injection molding, but only a few works focus on the weld line in µIM. 1. An evaluation model based on artificial neural network method. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. On the other hand, the mechanical strength at the weld line area of an injection molding part is always a concern. 1. To increase the sustainability of the process, determinative parameters and their effects should be examined. 1% higher than the ones without ultrasonic assistant, which indicates that the weld line strength in micro injection molding can be well reinforced by the ultrasonic oscillation due to the fact that ultrasonic oscillation induces better diffusion among the melting. 7 in Kobayashi et al. The weld line length was selected as part of the quality index to investigate the effects of gate location on weld. (3-1) Increasing the Resin Temperature at the Weld Line Section. Here is a look at the differences between them, the causes of meld and knit line imperfections, and their impact on part durability. A visual mold with variotherm system for weld line study in micro injection molding. อุณหภูมิของพลาสติกเหลวสูงเกินไปจนก๊าซหรือความชื้นแยกตัวออกมาได้. According to the characteristics. [ 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. Weld lines can be caused by many reasons, which covers the various aspects of mold, process, raw materials and product design, etc. NX Mold Flow Analysis. Amongst weld line. Therefore, the investigation on the developing process of weld line would be a significant issue for improving the quality of micro injection molded parts. In the end, the total amount of time that running a complete Taguchi DOE (L18) to occupy an injection. Insufficient plasticizing ability of injection molding machine. In this study the polycarbonate (PC) and carbon fiber (CF) are used as the experimental materials to investigate the impact of injection molding process parameters on tensile strength of weld line. Injection pressure or. Therefore, the length of flowing weld lines must be additionally defined. The problem with ‘weld lines. To explore the formation of weld lines in injection molding, a. As the name implies, it is usually positioned along the edge of the workpiece, forming a visible mark at the demarcating line. C. . The welding angle can be used to differentiate weld lines and meld lines. The line where two resin flows “knit” or “weld” together during injection molding is called a weld or knit line. 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. Effect of geometry and injection-molding parameters on weld-line strength. Increase the melting temperature. S. Various measures are taken at production sites to address these problems. This injection molding defect appears as a black discoloration on the surface of the molded part. • Reduce runner dimensions and maintain the same flow rate. Penyebab Weld Line. of micro injection molding process simulation by technology update and progress. The. Which means engineers need to know how to account for this phenomenon in an efficient way. Valve gates also make weld lines less of. The edge gate is the most popular and straightforward injection mold gate design. gas, which can cause blistering, as well as poor weld lines, warpage and the formation of cold slugs that affect filling and part mechanical properties. In injection molded parts, there are 2 types of weld lines: The first type of weld mark is called cold-melt joints and is formed when the melt front enters the cavity with different. Flow Lines. <Mold> Increase (or decrease) the size of the runners and gates. In the RHCM, the mold temperature profile plays a crucial. Park et al. Moldflow is computer software that is widely used across the plastic injection molding industry to predict and optimize the injection molding process and assist with mold design. [1-2] investigated the weld line zone of injection molded glass-fiber-filled polypropylene (PP) composites. Alloys. Co-injection molding technique is a useful way to study weld lines, which can offer more detailed information of the. Furthermore, injection molding was applied by filling these pellets into a micro-injection molding machine (C. 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. Instead, a line that looks like a seam forms. 4. injection molding. Its properties make it possible to create thin-walled parts having close tolerances in fast cycles over long. 809-814. This can occur when a polymer flow splits to go around an interruption (e. Three terms that often get mixed up in injection molding are weld, meld and knit lines. In an injection molding process, a weld-line forms when two flow fronts meet each other. As compared to a weld line, the flow fronts come together at less than 135 degrees. 030 0. In this study, one injection mold. 3 Materials Polypropylene (PP) and. This defect occurs due to the temperature and pressure not being high enough, causing premature solidification. Injection molding could be applied with many polymer materials, such as. 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. 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. When two or more strands of molten plastics meet in the mold, a weld. Wang. To position weld-line to avoid critical areas for the sake of aesthetics or mechanical strength is the key to the success of bi-injection molding. Rapid heat and cool injection molding is an example of a measure to prevent the generation of weld lines. Some of the approaches include the application of machine learning methods (Chen 2008; Manjunath and Krishna 2012; Kuo et al. Weld lines. It is a zone with reduced mechanical properties negatively influencing on the molding behavior in exploitation. In some cases, a weld line can also cause a loss of strength and impact resistance. This is a video excerpt from our Problems & Solutions Course - Weldlines. The formation of weld lines and their location along the flow path is a well-studied phenomenon in conventional injection molding; however, only a few papers are devoted to micro-injection molding [11,13,14,15,16]. Technol. Our injection molding company is explaining what these imperfections are, why they can compromise. Ideally, the resin flow will split into two flow fronts to pass around the obstruction and then recombine into a single flow front. 020 0. Change the gate locations. 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. Flash. 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]. For multiple gate and complex part. Effects of fillers and/or reinforcements on weld-line strength of nylon 6/6. 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. + Optimize holding pressure time. The following guidelines have. replication and poor weld line strength . 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. 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. One of the things that can compromise an injection molded part is a weld line, also called a knit line. Plastic Injection Molding Process. • Move injection locations to make flow fronts meet more obliquely, turning the weld line into a meld line. Computer simulation packages of injection molding have had success in predicting filling behavior in extremely complicated geometries, capable of predicting weld lines’ location exactly. , 509 (2) (2011), pp. A weld line can appear during the absence of enough pressure to push the plastic flow and then meld. Polymers 2023, 15, 2440 3 of 21. 025 100 120 140 160 180 200 220 240 Mold Temperature (F) LDPE PPAbstract. These are caused by the shot of molten plastic moving at different speeds throughout the injection. In the heating step, the heatingOverview of the injection molding process. Weld lines have been one of the common defects puzzling the injection molding industry. This consequently produces weld lines. 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. Plastics manufactured by injection molding are meant to be durable and reliable, able to hold up to heavy use, high temperatures, or adverse conditions. Strength measurements should be made to. + Adjust injection speed. Injection moulding (U. 010 0. Our weld line injection molding is essential for the best result of finished molded products. 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. 3 and 53. ResourcesTo study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. Reposition gates and runners to allow resin to flow around the obstruction from a. Weld line defects in injection molding is a line or lines on the part surface that caused the part looking ugly or cuased part lifetime, or even broken easily. 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]. Xie L. Weld lines. Injection molding weld lines refer to a line on an injection molded part that is generated where the two halves of the mold come together. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. Sequential valve gate technology. To explore the formation of. 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. A tensile test specimen mold, which allows cavity thickness varying from 2. 9. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. Miron MC, Major Z, Adachi T. th e use of design of e xperiment techniq ue. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. (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. The possibility of the functional thin film for. This defect occurs due to the temperature and pressure not being high enough, causing premature solidification. Weld line existence reduces the material strength; however, its demerit characteristics. The three parameters affecting operation were called injection pressure, injection time, and packing pressure which influence the quality of weld line. Edge Gates. Polyamide 6 (Lanxess, Durethan B 30 S 000000, non-reinforced, ISO 1874-PA 6, GR, 14-030, Cologne, Germany) was used for this experiment. After that, the compounds were injection-molded into tensile samples with and without weld lines to. From Understanding Weld-line Integrity by Sabic Innovative Plastics, p. Procedia Mater Sci 2014; 3: 2048–2053. Nguyen-Chung. 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. Proper venting is also required to ensure good weld-line quality. Unless you are manufacturing an extremely simple part with one gate and a unidirectional flow front, your part will have weld lines. Ideally, the resin flow will split into two flow fronts to pass around the obstruction and then recombine into a single flow front. The flow of the material in the injection mould takes place through the gate. However, even with advanced technologies and precise control, the process is not without its challenges. Emerging Materials Research. Weld line injection molding troubleshooting. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. Weld-line is a weak area which reduces the strength of the part locally. Weld line formation in the injection molding process occurs. สาเหตุการเกิด weld line คือเมื่อการไหลของพลาสติกมาประสานกันนะจุดใดจุดหนึ่งและจุดนั้นเกิดความแตกต่างของอุณหภูมิในสองทิศทางการไหลจะทำให้เกิด. In this study, the effects of injection temperature, injection pressure, and fiber cont. Bociaga and Jaruga (2007) investigated flowing weld line in injection process by injection molding machine, which the part surface was observed in reflected light using the optimal microscope and. Gambar 2. 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. 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. Problem: Weld lines are formed when plastic resin is forced around an obstruction in a mold tool and reforms on the side opposite the gate. Flow marks in injection molding can be avoided if adequate measures are taken. Materials Science. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. Inadequate back pressure. A new kind of weld line was. สาเหตุรองของการเกิดปัญหาการเกิดประกายเงิน (silver streak) 1. Crack growth behavior. In this study, we apply the technique of SAW to explore the acoustic properties near injection-weld lines by comparing the velocity of. 2. Mechanical properties of the weld line defect in micro injection molding for various nano filled polypropylene composites. Weld Lines-3 Ways for Detecting and Correcting. In injection molding of thermosoftening plastics, an important aspect having a bearing on the quality of articles is the appearance of weld lines that are formed when there are inserts, barriers, molding signs, reinforcements, etc. Examples of such failure are shown in Figure 1. They. Int J Adv Manuf Technol 52:131–141. Fracture behavior of weld lines in injection molded components loaded under real operating conditions. 2. During the plastic injection molding process, one of the biggest challenges is. Siemens PLM Software. 5 mm, 1. วัตถุดิบ พลาสติก PMPA ( อะคริลิก ) เกรด A. 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 Problems & Solutions course is designed to train injection molding personnel in. Weld or knit lines result wherever two or more polymer flow fronts unite. Weld lines in injection molding are frequently unavoidable. (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.