This model provides the necessary information. In the case of PC, the model predicts satisfactorily the weld-line strength as a function of injection temperature. Weld line. Sink Marks Cause 5: Improper Part Geometry. Download : Download high-res image (856KB) Download : Download full-size image; Fig. Weld or knit lines occur when melt flow fronts collide in a mold cavity. The need to minimize fiber breakage, plus the higher viscosity of materials with. (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. Weld lines may appear like seams or scratches, but that is not what they are. 3. Controlling the mold’s temperature could also minimize the weld line’s effects. Wu CH, Liang WJ (2005) Effects of geometry and injection-molding parameters on weld-line strength. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. If you adjust the ejection mechanism in the mold design, you also can reduce or eliminate your need for mold release agents. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. If 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]. Don’t forget to eliminate entrapped air in the weld line injection molding; otherwise, it’ll create unfilled portions in your part design, causing more weakening. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. Google Scholar | Crossref | ISI. In the above diagram, the converging flow fronts (indicated by red arrows. (3-1) Increasing the Resin Temperature at the Weld Line Section. In some cases, a weld line can also cause a loss of strength and impact resistance. A knit line may be unnoticeable or may look like a crack. T. It occurs when melting plastic material is injected into a mold, it flows through all parts of th. Provide a gas vent. 1. Stop using mold parting agents. 015 0. Weld lines can be caused by many reasons, which covers the various aspects of mold, process, raw materials and product design, etc. Weld lines have been one of the common defects puzzling the injection molding industry. Weld line existence reduces the material strength; however, its demerit characteristics. Mostly, this happens when two or more flow fronts do not “knit” during the injection molding process. There will be too many weld lines ; 6. Weld lines in injection molding are frequently unavoidable. 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. enough to each other to avoid weld line issues. when two or more melt flow fronts contact each other immediately after the cooling process. C. Proceedings of ANTEC (2000) Google Scholar [9] S. The weld line is then created with a higher flow front temperature and is packed with more pressure. 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) properties were measured, and statistical analyses were performed to gain insight on the correlation between melt flow rate and weld-line behavior. weld lines in injection molded thermoplastic composites. In weak material bonding, they will appear as hair-like weld lines. You will have to confirm them before tooling. injection molding. Co-injection molding technique is a useful way to study weld lines, which can offer more detailed information of the. Weld line. Weld lines in injection molding occur when two flow fronts meet and create a visible line on the surface of the molded part. Injected plates were generated using a double-gated mold under four different process conditions. Weld Lines-3 Ways for Detecting and Correcting. 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. Therefore, it is recommended to do a moldflow study prior to the mold being built. Weld lines are weak regions in thermoplastic injection moldings, due to low molecular entanglement and unfavorable orientation. According to the characteristics. This reduced thickness of the frozen skin further enhances the visual appeal of the. the three-plate mold often adopt this kind of gate. The weld line degrades the. They are the result of fundamental physical effects taking place inside of the mold tool cavity. These lines can occur at the gate location, where the plastic enters the mold, or anywhere along the flow path. Possible causes: Low temperature or fluidity of melted plastic during injection molding. One common issue that frequently arises during injection molding is the formation of weld lines. In. Voids and bubbles, 6. Venting at Weld Lines. Features such as sharp corners or undercuts can. One of the things that can compromise an injection molded part is a weld line, also called a knit line. In other words, weld lines reduce the mechanical properties of the product. Vibration assisted injection molding. Abstract. ac. 10 in Nguyen-Chung et al. Design. During injection moulding, a weld-line occurs when two or more flow fronts collide in the hollow cavity. Weld lines in injection molding are frequently unavoidable. The three parameters affecting operation were called injection pressure, injection time, and packing pressure which influence the quality of weld line. In an injection molding process, a weld-line forms when two flow fronts meet each other. 2. Optimizing the Injection Parameters. A weld line is a mark left on the surface of a plastic injected molded part. Weld lines in injection molding are frequently unavoidable. when two or more melt flow fronts contact each other immediately after the cooling process. Thus, it is important to understand (i). 13. This principle has been implemented on a complex component in the case of the spring-loaded cogwheel shown in Figure 5, for instance. Weld Lines-3 Ways for Detecting and Correcting. Carefully consider all the relevant aspects of the mold design specification before. In order to increase the quality of the products manufactured by injection molding, RTC technology can be used to achieve higher mold temperatures. Thus, it. การแก้ไข ชิ้นงานจุดที่เกิดความอ่อนแอบริเวณ weld line คือต้องใช้ความเร็วในการฉีดต่ำในจุด. Adjust the design for the flow pattern to be a single source flow. Adjust Injection Molding Parameters: Optimizing injection speed, pressure, and temperature can help ensure better melt flow and reduce the likelihood of weld line formation. Using the conventional method, weld-line depths on the surface ranged from 6 to 13 microns. Weld lines are a surface defect caused when two or more flow fronts come together during the injection process. Polymers 2023, 15, 2440 3 of 21. Try to gradually raise the mold temperature and barrel temperature. When the two such melt flows. Poor mold spot Spot mold to ensure fit and vent depths at ~0 . 22: Weld line formation when melt splits around core pins. . The performance of weld lines in talc filled polypropylene box moldings produced with a. This is particularly true if the wall thickness in the weld is thin – i. (3-1) Increasing the Resin Temperature at the Weld Line Section. Weld-line yield strength, yield strain, and failure strain of talc-filled polypropylene increase with increasing melt temperature and increasing hold pressure. A weld-line is known as a representative defect in the field of plastic injection moulding, and also as a cause of inferior mechanical propensities and poor appearance. It is important to investigate the weld line because the weld line area can induce potential failure of structural application. A poor knit line can cause only cosmetic blemishes or it can significantly weaken the structural integrity of a part. Weld line and warping are two critical defects for injection-moulded part. Micro-injection molding (µIM) is a widespread process for the production of plastic parts with at least one dimension, or feature, in the microscale (conventionally below 500 µm). Specifically, injection-mold lines are often associated with poor mechanical strength. • Reduce runner dimensions and maintain the same flow rate. The parts are molded flat and are slightly stressed once installed in an arced position, but not excessively. 5. 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. Despite injection molding being recognized as a robust process for obtaining parts with high geometry accuracy, one last occurrence remains a challenge in micro. Raising the mold temperature will keep the material molten longer, resulting in stronger weld lines and even elimination of weld lines. The type of resin used during injection molding plays a large role in whether or not a knit line will be present. The weld-lines are undesirable from both aesthetic and functional points of view and their effect is different for. The parting line in injection molding is which one of the following: (a) the lines formed where polymer melt meets after flowing around a core in the mold, (b) the narrow gate sections where the parts are separated from the runner, (c) where the clamping unit is joined to the injection unit in the molding machine, or (d) where the two mold halves come. So today we are going to take a look at the five most common defects in injection molding and their solutions. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. The cracking was always located in the weld/knit line and therefore caused by weakness in the bonding of the plastic at. Premature partial solidification of the molten plastic leads to inadequate bonding — the primary cause of weld lines. Weld-line is a weak area which reduces the strength of the part locally. 2) show that the weld line is formed as expected from the middle of the cavity towards the wall. From Fig. The simulated cold weld line length is consistent with the experimental one when a 115 °C mold temperature is adopted; with lower mold temperatures, the simulated lengths are smaller than the experimental ones—in accordance with the literature on the conventional injection molding process [26,27]—probably because of the definition adopted. CrossRef View in Scopus Google Scholar [17] G. Alter the mold design. Recently, the injection molding of fiber reinforced thermoplastics (FRTP) containing short fibers has been widely carried out to mass-produce molded products with complex shapes. 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. The goal is to create a uniform thickness and at the smallest (thinnest) level required. In injection molding weld lines are formed whenever two flow fronts are joined. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. 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. GlossFlow-induced fiber orientation and weld lines are com-mon features of the injection molding process. Weld line strength is important in blow molding as well as injection molding. 025 mm (0 . In an injection molding process, a weld-line forms when two flow fronts meet each other. Usually it’s a straight line, and often to be found radiating. 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. Weld lines have been one of the common defects puzzling the injection molding industry. Injection-molding machine is the Negri Bossi VE210-1700 with screw diameter 60 mm. Gate blush, 4. Weld lines are where two flow. Weld line, 5. Weld lines are common defects in injection-molded plastic parts that occur when two flow fronts of molten plastic meet and fuse together during the molding process. The four sets of plaques are produced by changing the magnitude of packing pressure equal to 60% of filling pressure, with increment of 20% up to 120% of filling pressure. What are Weld Line Defects? Weld line defects – also known as knit lines – is a defect that occurs when the injected plastic meets within a mold. ), with different mould surface finishes (polished, fine eroded, rough. Expand. technical ulletin SPECIALTY POLYME RS Design and Production of Injection Molding ToolsIncrease the injection speed in order to fill the mold more quickly and ensure the material does not prematurely cool down; in addition, when the speed is adjusted the flow fronts may meet at a different spot and move the weld line location. Article Google Scholar Deng YM, Zheng D, Lu XJ (2008) Injection moulding optimization of multi-class design variables using a PSO algorithm. In narrow fields, a limited amount of molten liquid can solidify and block the flow. This gives a clue as to how it was formed. A knit line in a plastic injection-molded part is created when two separate plastic flows meet within the mold and "resolidify" along their interface. Shaofei Jiang. Try to gradually raise the mold temperature and barrel temperature. In this paper, a weld line factor (W-L factor) was adopted to describe the. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. 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. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. To respond to poor plasticization and uneven melt temperature,. In this study, polypropylene (PP) was compounded respectively with carbon nano fibers (CNFs) and TiO 2 nano particles at various weight fractions (10, 20, 30, 35. Its appearance can be improved by adjusting parameters. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. Streaks 3. This is a video excerpt from our Problems & Solutions Course - Weldlines. This study describes how the weld line was formed on the part. Sink Marks Cause 2: Low Pack and Hold time. Silver Streak. After that, the compounds were injection-molded into tensile samples with and without weld lines to. when two or more melt flow fronts contact each other immediately after the cooling process. This line does not normally impact the overall shape or dimensions of the item. While there are many situations where they are barely perceptible, weldlines represent a potential source of weakness in molded parts. As the polymer. (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. Weld lines: Cold feedstock in the die: Increase injection speed, mold temperature, and feedstock temperature, enlarge gate opening, add venting channels or overflow wells near weld line locations, move gate location, redesign parts to avoid stream partition: Flow mark: Cold feedstock in the dieWeld lines are a common imperfection to be found in most plastic injected molded parts. High-density PE was also moulded in the same conditions but in a lower temperature range (145 to 220°C). A quantitative evaluation of the appearance quality of weld lines in RHCM parts. Weld lines are the unfavorable defect not only in normal injection molding process but in micro injection molding process. The literature on the formation of weld lines, and their consequences, is more abundant on the area of injection molding [5-12] than on extrusion [13]. Sink Marks 2. Weld lines can. It is important to investigate the weld line because the weld line area can induce potential failure of structural application. Flow marks in injection molding can be avoided if adequate measures are taken. Thus, a right gate design raises polymer temperature to prevent the formation of weld lines and flow marks. The injection molding gate generates heat by dissipation. During injection. Where the weld lines are, where the sink marks or voids will be, and how the part warps—all of these are determined by where the molten plastic is injected into the part cavity. Int. There are various types of injection molding defects that can cause such interruptions in the manufacturing cycle. Weld lines, generated during injection molding, can significantly reduce the mechanical performance of structures. Mold vents should function the same way. In injection molding, a V-notch-shaped weld line [1] is generated in the melt front meeting area. 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. Flow lines are lines, waves, or ring patterns that appear on the surface of a part, noted by their slightly different color from the rest of the piece. 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]. 1. Sink marks are a common type of injection molding defect. ac. Weld Lines. Strength measurements should be made to. Int J Adv Manuf Technol 52:131–141. Polym Eng Sci 45(7. Weak weld lines are perhaps the most common and difficult injection molding defect to eliminate. This may require higher melt temperature or lower injection speed . injection molding, (b) weld line and meld line, and (c) injection sample size and shape. 15 shows the frozen layer and weld lines at the end of mold filling. Weld Line Occurrence in Plastic Injection Molded Parts Weld lines, also commonly known as knit lines, may be present in a plastic molded part depending on the partsí geometry. Mold Design. The most common method for the weld-line characterization is mechanical testing by means of a tensile or bend stage [6,7]. 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. Three terms that often get mixed up are weld, meld, and knit lines. also utilized the co-injection molding technique to study the flow of polypropylene at the weld line behind an obstacle in injection molding; the. The plaques are prepared out of 30% glass-filled Polyamide 6 material. 453-455. They are unavoidable even for moderate complex products. 1. th INTRODUCTION Injection molding is one of the most Weld Lines in a plastic cover. micro injection molded weld line’s mechanical properties. (1998) for clear photographs. 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. 3: Weld Lines. 000 0. 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. Possible Sources of Weld/Knit Lines: Temperature from the injection molding machine, runners, and/or the mold itself in order to ensure the plastic resin flows properly;Weld line is one of the plastic injection molding defects. Weld-line is a weak area which reduces the strength of the part locally. This is where the melt fronts divided by an insert, such as a pin or a. A weld line can also be called a knit line. , less than 0. Proceedings of ANTEC (2000), pp. Consultant @ Effinno Technologies, BSME, MBA - Bridge between Plastics Injection Molding Knowledge and Practice. This happens when the molten plastic is injected into the mold cavity and flows around an obstacle such as a pin, hole, or protrusion, and then comes back together. 5. Part design features may cause a material flow to split and rejoin as it flows around design features in a mold. The following are the conclusion drawn from the present research: 1. This month, in our FREE SimTech™ series of webinars, we will explore weld lines and how they develop. These lines are formed when two or more flowing molten plastic streams meet and fuse together, creating a visible line on the surface of the molded part. 1. 5. 6. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties [3,4,5]. Low mold temperatures are usually employed to decrease cycle molding time and final process costs; however, resulting surface defects include weld lines, sink marks,. Criens, R. Weld lines are visually undesirable and a plastic part is structurally weak at weld line positions. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. Polym. Steven. 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. The appearance quality of plastic parts in weld lines can be improved significantly through the rapid heating cycle molding (RHCM). The parting line in injection molding is which one of the following: (a) the lines formed where polymer melt meets after flowing around a core in the mold, (b) the narrow gate sections where the parts are separated from the runner, (c) where the clamping unit is joined to the injection unit in the molding machine, or (d) where the two mold halves come together? Avoid knit lines when designing a molded part to improve cosmetic appearance and functionality. The resulting defects don’t stop at flash only. gasket seal leakage where the weld line crosses a gasket. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties [3,4,5]. Fracture Toughness of Weld Lines in Thermoplastic Injection Molding, Polymer Engineering and Science, 33(15): 996-1001. avoid weld lines, and facilitate smooth. Adjust the position of the gate and include a venting slot. This study presents an innovative approach to enhancing weld line strength in advanced polymer injection molding through applying gas-assisted mold. The more gate points there are, the more weld lines will occur. Emerging Materials Research. 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. Weld line is formed when two different melt flows converge, as illustrated in Fig. Here is a look at the differences between them, the causes of meld and knit line imperfections, and their impact on part durability. consideration in gate location. Thicker parts require more cooling time and can lead to air becoming trapped in the mold and weld / knit lines to form. Weld lines can be caused by many reasons, which covers the various aspects of mold, process, raw materials and product design, etc. 1 Prediction of weld lines with injection molding simulation softwareReduced frozen skin thickness: High injection speeds also contribute to a thinner frozen skin at the weld line. According to the special features of micro injection molding process compared with normal injection molding process, the main related factors to weld line’s properties were classified as 3 group, named as processing conditions, mold design and structure, external process. 3. To explore the formation of weld lines in injection molding, a. the meeting angle by optimizing variation over time in the cavity. During the plastic injection molding process, one of the biggest challenges is. 2. Therefore, more studies covering this subject are required in order to improve the insight regarding the mechanism involved in the formation of weld lines in extrusion and,From the so-produced materials, specimens with weld lines were produced according to the first test series, but varying the injection molding parameters only twice, between the best and worst settings found in the previous study with the polypropylene types with MFR 8 g/10 min, i. Weld Lines. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. Figure 1a illustrates how the weld line is produced when two melt streams merge during the final filling process. Weld lines occur when melt flow fronts meet during the injection molding of plastic parts. The gate vestige for injection molding is usually narrow. Increase the injection speed to reduce the amount of cooling happening in the mold. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. Weld. It is a well-known fact that weldlines are unavoidable in most injection-molded products of even moderate complexity. demanding injection molding and end-use requirements. 005 0. In this regard, the plasticizing ability of the plastic injection moulding machine should be checked. Insufficient injection pressure and speed can cause weld lines. 6. and Mosle, H. Materials Science. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. Steven. 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. Our injection molding company is explaining what these imperfections are, why they can compromise. 2(a, b). It will degrade materials performance; 9. One test mold was used to mold three different materials using heat/cool and conventional molding techniques. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. Weld lines are a common defect generated in injection molding, which apparently affects the performance of final products, but the available reports on carbon fiber-reinforced thermoplastics are still rather few. In injection molding, a V-notch-shaped weld line is generated in the melt front meeting area. The flow fronts at different times (Fig. 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. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright. Cracks in Corners – When cracks appear in the corners of plastic parts, the cause is too much plastic shrinkage onto the mold core in that corner. You can choose material of low viscosity and can increase the injection pressure. A weld line is often unavoidable. Ideally, the resin flow will split into two flow fronts to pass around the obstruction and then recombine into a single flow front. Gava and co-workers implemented an investigation devoted to the de-Injection-mold weld lines may or may not be easily identified by naked eye or straightforward optical microscopy. Reduce the amount of release agents. But add 30% glass and weld-line strength retention drops to only 34% as high as the compound with no weld. Unless you are manufacturing an extremely simple part with one gate and a unidirectional flow front, your part will have weld lines. In this work, the residual strength of a fiber-reinforced injection molded part containing a hot weld line—or meld line—was evaluated. 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. One solution is to prevent the weld lines from forming in regions that are. In this regard, the plasticizing ability of the plastic injection moulding machine should be checked. 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. Wang et al. 2. They have their origins in material choice, part design, tooling, and processingIncrease the mold temperature and smooth out any sharp corners or turns in the mold to facilitate even melt flow. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. In many cases, you will also see that the part is hanging up on the core during ejection. ppt from SCIENCE 101 at Symbiosis International University. Weld Lines. Weld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of injection‐molded parts. Weld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of injection‐molded parts. The utility model relates to a mold structure capable of eliminating the appearance of weld lines of a hole-shaped injection molded product. Injection molding could be applied with many polymer materials, such as. 2017-01-0481. Runner Type Venting Plastic melt and mold temperature Injection speed and pressure Learn how to troubleshoot weld lines in injection molding. Redesign the mold to prevent the weld line. The rule is, a higher pressure shall be required to push the material in the machine when there is excess mold. Usually it’s a straight line, and often to be found radiating away from a hole, inclusion or other such part feature. The hair-like weld line is the. How Are They Formed? Molten plastic resin is injected into a mold cavity through an opening known as a gate. Weld line formations can be weak if they fall in areas that will bear stress or impact. Weld Lines. 2) Vents in an injection mold should let the air out, but not the liquid plastic. Although they often cannot be avoided it’s possible to minimize their cosmetic effects to an acceptable degree through careful product design and manufacturing. Weld lines are formed when two orThe experiments were performed on an Arburg Allrounder 320C 600-250 injection moulding machine using a two cavity-injection mould (Fig. Adding vents, using overflows, or using porous metal. e. Here we are looking at most common part defect that can come from injection molding called weld line. The solution to an internal part cracking problem is to change the packing pressure. There are several possible causes that need to be investigated to troubleshoot weld lines in injection molding. 004 m, a characteristic velocity ν 0 =0. Mold flow marks, also known as flow lines or weld lines, are often caused by variations in the flow of molten plastic material during the injection molding process. Amongst weld line. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. As the name implies, it is usually positioned along the edge of the workpiece, forming a visible mark at the demarcating line. Fisa et al. These are caused by the shot of molten plastic moving at different speeds throughout the injection. Save. When a product is produced through injection molding, a high-powered tool injects melted plastic into a custom, double-sided mold. Abstract. Flow LinesThe 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). One of the defects observed in injection molding parts is weld line strength, which forms when two or more separate melt fronts traveling from different directions meet and join as the mold cavity is filled. Double push filling method. Azieatul Azrin Dzulkipli and M. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. This is where the melt fronts divided by an insert, such as a pin or a block, in a mold cavity rejoin each other downstream of the insert. 030 0. Micro-injection molding (µIM) is a widespread process for the production of plastic parts with at least one dimension, or feature, in the microscale (conventionally below 500 µm). A meld line occurs when two moving melt fronts converge and flow parallel to each other. Abstract. 2-1. 7 in Kobayashi et al. The impact behavior of weld-lines in injection molding. In this experiment, several ejector. 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. A new kind of weld line was. They found that the weld line is a zone between 2 and 8 mm wide extending throughout the thickness in whichEffects of mold temperature and pressure on shrinkage 0. Conclusion The formation of weld lines in micro injection molding of plastic depends on different parameters such as melt temperature, injection pressure and fabrication method. carried out to mass-produce molded products with complex shapes. The weld lines that occur in injection mouldings are critical areas on which depends on the strength of the mouldings. Some of these are listed below: Plastic warpage. Wang, G. g. Effects of cavity surface temperature on mechanical properties of specimens with and without a weld line in rapid heat cycle. Insufficient plasticizing ability of injection molding machine. 030 0. Redesign the mold to prevent the weld line. Weld lines appear on the molded part where molten plastic meets. 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.