Weld Line defect analysis, the most common of many defects in injection moulding products. Increase the melting temperature. Fig. 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. Polymer Engineering and Science (2005) There are more references available in the full text version of this article. Ideally, the resin flow will split into two flow fronts to pass around the obstruction and then recombine into a single flow front. 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). Insufficient plasticizing ability of injection molding machine. Simulation of polymer molding filling process with an adaptive weld line capturing algorithm. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. Injection molding is nothing without molds. Bin-Xin Yang Ouyang Jie Supei Zheng Qiang Li Wen Zhou. To prevent weld lines, increase the pressure and temperature. Weld line. [23, 24]. Redesign the mold to prevent the weld line. Munich, Germany: Carl Hanser Verlag, 1994. Injection molding. 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. Neat polypropylene retains nearly 90% of its strength on a properly designed and molded weld line. industry, to deliver intuitive injection mold-ing simulations embedded in NX. Flow lines are off-color lines, streaks, and other patterns that appear on the surface of a part. Weld lines in injection molding are a type of cosmetic defect that detracts from a plastic part’s appearance. 21: Weld line failure caused by hoop stresses. Sink Marks Cause 5: Improper Part Geometry. As the name implies, it is usually positioned along the edge of the workpiece, forming a visible mark at the demarcating line. g. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. 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. + Improve vent inside the mold. For this purpose, the width of the weld line calculated by Sigmasoft is. Its appearance can be improved by adjusting parameters. Weld line and warping are two critical defects for injection-moulded part. S. In some cases, a weld line can also cause a loss of strength and impact resistance. Save. 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. To prevent knit lines, injection molders can increase the temperature of the molten resin to prevent solidification from starting too soon, and increasing injection speeds and pressure are also potential solutions. In the sense that the weld line is better formed before the resin. If the different flow fronts have cooled. This is expected to achieve maximum results while the pressure holding effect will also increase. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. <Materials> Pre-dry thoroughly. 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. With unchangeable and fixed requirements for the final product, their avoidance often proves difficult. Weld lines can significantly reduce ultimate tensile strength (UTS) and fracture strain of talc filled polypropylene (PP). In this paper, aiming at the problem of weld line defects in the injec- tion process of a key phone panel, the injection process is optimized by using Moldflow and drop simulation. and Mosle, H. This study describes how the weld line was formed on the part. It is not always easy to completely eliminate weld lines by simply adjusting the relevant injection mold design or the molding conditions. 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. 1. 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. 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. 1. 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. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. com1. 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. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. Insufficient plasticizing ability of injection molding machine. ResourcesTo study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. The resulting defects don’t stop at flash only. The second technique, cascade injection moulding, can produce parts free from weld lines. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. – Use generous and even. 2011; 509 (2):226–233. Three terms that often get mixed up in injection molding are weld, meld and knit lines. Part design features may cause a material flow to split and rejoin as it flows around design features in a mold. 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. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. One of the factors that determines the quality of injection molded parts is the weld line [50,75,76]. Install an ultrared light inside the hopper. 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). 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. 1. Zhao, X. . 3 and 53. The weld line length was selected as part of the quality index to investigate the effects of gate location on weld. From Understanding Weld-line Integrity by Sabic Innovative Plastics, p. (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. Injection Molding Glossary; Weld Lines; Weld Lines. Insufficient clamp tonnage Increase clamp pressure or move to machine with more tonnage . Article Google Scholar Xie L, Ziegmann G (2009) Influence of processing parameters on micro injection molded weld line mechanical properties of polypropylene (PP). We recently had a few pieces (2-3%) crack after assembly, while in storage (not installed, still in the package). To resolve this issue, rapid heat cycle molding (RHCM) has attracted attention as an innovative PIM technology. Article Google Scholar Deng YM, Zheng D, Lu XJ (2008) Injection moulding optimization of multi-class design variables using a PSO algorithm. Miron MC, Major Z, Adachi T. 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. 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 study focus on the. 015 0. 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. This injection molding defect appears as a black discoloration on the surface of the molded part. Injection-molding machine is the Negri Bossi VE210-1700 with screw. Xie L. in the cavity of the injection mold. 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. Consequently, weld regions have been observed to have inferior mechanical properties compared to the bulk. Int J Adv Manuf Technol 52:131–141. Instead, a line that looks like a seam forms. 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. The occurrence of a weld line means a significant problem both aesthetically and mechanically in the design of injection moulded parts. These flow. Weld Line defect analysis, the most common of many defects in injection moulding products. Weld line formation in the injection molding process occurs when two or more melt flow fronts contact each other immediately after the cooling process. Co-injection molding technique is a useful way to study weld lines, which can offer more detailed information of the. These are preferred over weld lines as they will normally result in improved cosmetics and structure. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. In this regard, Taguchi orthogonal experimental design is adopted, and five processing parameters, the mold temperature, melt temperature, cooling time, packing. Meld and knit lines are actually both different types of weld lines. In addition a weld line can be moved to an area where it is less visible. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. 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 line, 5. C. Weld Lines-3 Ways for Detecting and Correcting. 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. M. It has larger cross-sectional regions that allow sufficient molten plastic flow into the cavity. <Mold> Increase (or decrease) the size of the runners and gates. Controlling the mold’s temperature could also minimize the weld line’s effects. DYNAPLAST Tbk. 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. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. une, 13: 15. 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. Here we are looking at most common part defect that can come from injection molding called weld line. In injection molding, it is often important to maintain consistent color throughout the part. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. [ 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. Adjust Injection Molding Parameters: Optimizing injection speed, pressure, and temperature can help ensure better melt flow and reduce the likelihood of weld line formation. 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. CrossRef View in Scopus Google Scholar [17] G. 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 effects of fiber concentration has been studied in detail. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Wolfgang Homes, head of the applications department of Eurotool, a manufacturer of hot runner systems, clarified the two methods for IMI, noting that. The following are the reasons. It is important to investigate the weld line because the weld line area can induce potential failure of structural application. Thus, it is important to understand (i). Weld lines are visually undesirable and a plastic part is structurally weak at weld line positions. In this way critical areas of the interface in regard to the lack of interdiffusion and the inappropriate molecular orientation were found to be placed near. weld lines in infill analysis of injection molding simulation was observed [5]. They occur when melt flow fronts collide in a mold cavity. [1] Kobayashi et al. Reduce the amount of release agents. The weld line and the flow pattern of co-injection molding can be seen from Fig. Adjust the position of the gate and include a venting slot. 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. The flow disruptor is a small insert introduced inside the injection molding cavity, in the weld line area, and its objective is to mix the melt and disrupt fountain flow in order to blur and. Weld-line, a common occurrence in plastic injection moulding, is a representative defect compromising mechanical qualities and product appearance [16]. Figure 1 below shows the development of a weld line. Injection Molding Glossary; Weld Lines; Weld Lines. of micro injection molding process simulation by technology update and progress. To respond to poor plasticization and uneven melt temperature, the molding cycle can be extended to make. 2. 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]. 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. 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. 0 mm, is designed to conduct the. Weld lines in injection molding are formed when two or more flow fronts of molten plastic material meet and merge during the molding process. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. They decrease the. This article will introduce you the usage, types, and advantages of the Sequence Injection Timer. Threadline gap in-between part due to improper gate location in complex design parts including excess of holes (multipoint. Injection molding is a highly versatile manufacturing process used to produce a wide range of plastic products with precision and efficiency. The strength of the weld-line area can be increased by optimizing injection molding process parameters like melt temperature, injection speed, packing pressure, changing gate type and location, etc. 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 the 1947 book, Injection Molding of Plastics, the late Dr. 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. 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. Plastic Injection Molding Process. 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. th INTRODUCTION Injection molding is one of the mostWeld lines have been one of the common defects puzzling the injection molding industry. 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]. 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. Re-balancing entire manufacturing lines may be required to effectively deliver and sustain SMED excellence. The thermo-rheological findings were used to investigate the sources of weld line weakness. 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. 020 0. วัตถุดิบ พลาสติก PMPA ( อะคริลิก ) เกรด A. Raising the mold temperature will keep the material molten longer, resulting in stronger weld lines and even elimination of weld lines. 3. In the heating step, the heatingOverview of the injection molding process. Munich, Germany: Carl Hanser Verlag, 1994. . (3) Adjust the temperature of the barrel and nozzle: the viscosity. Ejector System (Pötsch, 1995) . 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. The effects of these two injection molding process parameters are explained in terms of their influence on the skin-core morphology observed on the fracture surfaces in the weld zone. Emerging Materials Research. 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. Slow down injection speed. The weld line’s strength is reduced when. Stagnant weld lines are formed when melt streams meet head-on. 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. Burn Marks. The wheel has to be gated at three places on the hub and. Here is a look at the differences between them, the causes of meld and knit line imperfections, and their impact on part durability. A quantitative evaluation of the appearance quality of weld lines in RHCM parts. 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. + Increase mold temp, or materials’ temp, or holding pressure. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. These lines can occur at the gate location, where the plastic enters the mold, or anywhere along the flow path. Xie L, Zhu D, Ziegmann G, Steuernagel L (2016) Investigation on correlation between cold/hot weld line mechanical properties and micro injection molding processing parameters. 3. The injection molding process can be optimized to maximize weld line strength by increasing. 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. 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. In some cases, a weld line can also cause a loss of strength and impact resistance. Nozzle – The nozzle is at the end of the barrel and contacts the injection mold. The present work focuses on studying the effect of packing pressure on strength of stagnation weld-line. Edge Gates. High-density PE was also moulded in the same conditions but in a lower temperature range (145 to 220°C). Mold flow analysis is widely employed in mold making industry, utilizing data simulation software, the injection molding process can be simulated and presented on the computer,. Flow analysis of the weld line formation during injection mold filling of thermoplastics. For thick-walled parts, slow injection rates result in more uniform polymer distribution . To increase the sustainability of the process, determinative parameters and their effects should be examined. Poor weld line Ⅰ. Polyamide 6 (Lanxess, Durethan B 30 S 000000, non-reinforced, ISO 1874-PA 6, GR, 14-030, Cologne, Germany) was used for this experiment. This can allow the. The cracking was always located in the weld/knit line and therefore caused by weakness in the bonding of the plastic at. . 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. as warpage, shrinkage and weld line of the plastic parts. 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. When this fails to happen correctly, a weld line defect occurs. In this study, we apply the technique of SAW to explore the acoustic properties near injection-weld lines by comparing the velocity of. Weld line location. Visualization analysis of flow behavior during weld-line formation in injection molding process. Bubbles are caused by melting flow fronts colliding in a mold cavity. A tensile test specimen mold, which allows cavity thickness varying from 2. Methodology. Machine Shot Capacity – The maximum volume of resin that can be injected in a single stroke of the injection machine. [ 18 - 21 ] In addition, the effects. As the plastic flows through the mold it. This paper presents the. Remedies: Reduce packing and fill rates by adjusting until the part is properly filled with minimum stresses. Voids and bubbles, 6. In an injection molding process, a weld-line forms when two flow fronts meet each other. Injection moulding (U. Weld lines are a common issue in injection molding, and occur when two flow fronts meet and fuse together as the material cools and solidifies. This reduced thickness of the frozen skin further enhances the visual appeal of the. Expand. In the plastic injection molding industry, we work with materials that are byproducts of oil refinement and molds made of metal casting, so our terminology is bound to be at least slightly confusing. Google Scholar | Crossref | ISI. 2020-01-1306. 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. You will have to confirm them before tooling. Crack growth behavior. 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. It is important to investigate the weld line because the weld line area can induce potential failure of structural application. Weld lines have been one of the common defects puzzling the injection molding industry. Melt temperature does effect the weld. 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. As a result this weld line will be a weak point in this part. As a result this. อุณหภูมิของพลาสติกเหลวสูงเกินไปจนก๊าซหรือความชื้นแยกตัวออกมาได้. Weld lines are a kind of Achilles heel of plastics. This may require higher melt temperature or lower injection speed . This remains as a challenge for control engineers. Azuddin / Procedia Engineering 184 ( 2017 ) 663 – 672 Fig. 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 not only detract from an injection-molded part’s surface quality, but also significantly reduce its mechanical strength. Polym Eng Sci 45(7. During injection moulding, a weld-line occurs when two or more flow fronts collide in the hollow cavity. Boost time too long Shorten boost time, lower boost pressure, or move transfer to an earlier position . Lugs size is 65 х 24 х 4 mm. 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. <Mold> Increase (or decrease) the size of the runners and gates. 020 0. ABS is a commonly used plastic in injection molding due to its excellent mechanical properties and chemical resistance. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. Weld lines are a common imperfection to be found in most plastic injected molded parts. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. The design of the mold, as well as the part being molded, has a significant impact on the success of the process. In an injection molding process, a weld-line forms when two flow fronts meet each other. Remedies: Raise the temperature of the mold or molten plastic. The gate vestige for injection molding is usually narrow. This month, in our FREE SimTech™ series of webinars, we will explore weld lines and how they develop. The strength of the weld-line area can be increased by optimizing injection molding process parameters like melt temperature, injection speed, packing pressure, changing gate type and location, etc. Unless you are manufacturing an extremely simple part with one gate and a unidirectional flow front, your part will have weld lines. 6. For those who are new to the injection molding industry, may be confused about this product. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. Gate blush, 4. Nguyen-Chung. Our weld line injection molding is essential for the best result of finished molded products. Silver Streak. The weld lines are an integral part of plastic injection molding and can seldom be prevented, even by specifically planning the mold with inserts for holes or the like. ac. Flash. The. (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. 809-814. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. • Optimize the design of the runner system. There are several possible causes that need to be investigated to troubleshoot weld lines in injection molding. The parts are molded flat and are slightly stressed once installed in an arced position, but not excessively. 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. As these flow fronts come together on the. 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]. Criens, R. 5. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. Weld lines may appear like seams or scratches, but that is not what they are. 2. Amongst weld line. Mold flow analysis can predict the location of weld lines. Effects of cavity surface temperature on mechanical properties of specimens with and without a weld line in rapid heat cycle. Cited by (41) Effect of mould surface roughness adjustments to increase the flow path length in the injection moulding process. Thoroughly clean molding machine cylinders. Kagitci YC, Tarakcioglu N (2015) The effect of weld line on tensile strength in a polymer composite part. As such, optimizing mold designs should always be incorporated in your production model. The Problems & Solutions course is designed to train injection molding personnel in. 2. Three terms that often get mixed up in injection molding are weld, meld and knit lines. In our DFM report, we will analyze the possible weld lines. A knit line may be unnoticeable or may look like a crack. The most common and one of the most challenging injection molding defects are weld and knit lines. 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. 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. 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. Microsyst Technol, 14 (6) (2008), pp. Weld line strength is influenced by the temperature at which the weld line is formed and the pressure exerted on the weld until the part freezes, (pressure is 0 at the weld line). A weld line can also be called a knit line. G. 2. C. According to the characteristics. Vertical Plastic Injection Molding Machine [10, 11, 12] 2. Ada berbagai penyebab mengapa weld line bisa muncul pada permukaan produk plastik. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. These flow fronts occur when the molten plastic material encounters obstacles, such as inserts, ribs, or other features within the mold cavity. 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. • Move injection locations to make flow fronts meet more obliquely, turning the weld line into a meld line. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. In order to study the weld line developing process and its influence on mechanical properties in micro injection molding, a visual mold with variotherm system mold was designed and fabricated. 2. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. Email him at jhenz@polymer-center. + Optimize holding pressure time. 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. Weld lines. Weld lines represent the region where two separated melt fronts recombine. The weld-lines are undesirable from both aesthetic and functional points of view and their effect is different for varied materials, process conditions, loadings, forms of weld-line, etc. 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. As the weld line can significantly lower the mechanical strength of µIM parts, it is relevant to clarify the position of weld. Increase the injection speed to reduce the amount of cooling happening in the mold. The flow of the material in the injection mould takes place through the gate. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. However, research about the computer determination of weld lines in injection molding remains scarce. when two or more melt flow fronts contact each other immediately after the cooling process. Because of the ever-increasing requirements for parts performance, lots of researchers have perf. T he decreased gloss level at the position of. Sink marks are a common type of injection molding defect. The main types of injection molding defects are: 1. Figure 2. Investigate for potential contamination. They found that the weld line is a zone between 2 and 8 mm wide extending throughout the thickness in whichTo investigate the effect of hot gas heating in injection molding on the weld line appearance, an experiment was conducted with the molding parameters listed in Table 2. In this paper, a weld line factor (W-L factor) was adopted to. 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. 1, right). So today we are going to take a look at the five most common defects in injection molding and their solutions. This gives a clue as to. In this study, the effects of injection temperature, injection pressure, and fiber cont. 2. The utility model relates to a mold structure capable of eliminating the appearance of weld lines of a hole. Remember, by avoiding weld lines, you can lessen operations cost. 1. 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. Ideally, the resin flow will split into two flow fronts to pass around the obstruction and then recombine into a single flow front. The definition of weld lines: When multiple plastic flow fronts meet in the cavity after encountering inserts, holes, or areas with inconsistent flow rates or interrupted melt flows, or in the case of gate injection filling, the inability of two or more flow fronts to fully “knit” together will cause the linear weld marks. 4If the injection gate is not properly designed, it can cause the formation of defects like sink-mark, warpage, short shot, weld-line, air traps, and other faults [15]. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability.