The specific method is that when the product is just filled and filled in the cavity, the insert. Mold Design. Weld lines are visually undesirable and a plastic part is structurally weak at weld line positions. 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. During injection. 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. A new kind of weld line was. Flow front tracing simulation results for weld line developing process in micro injection molding with Comsol ® Multiphysics 3. Solving one problem can introduce other problems to the injection molding process. Better weld line quality was obtained by Huang. Second, depending on the size of the overflow well, you get a little bit of flow melding together, and that helps strength so that you have some intertwining of the polymer chains. Increase the injection speed and mold/operational temperature to prevent fracture or surface breakdown. These lines can occur at the gate location, where the plastic enters the mold, or anywhere along the flow path. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. The conditions are temperature, injection speed, and injection pressure. They appear on the surface of injection molded parts like lines. GlossFlow-induced fiber orientation and weld lines are com-mon features of the injection molding process. (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. Flow lines. Plastic Injection Molding Process. Weld Line Factors for Thermoplastics. These are caused by the shot of molten plastic moving at different speeds throughout the injection. Except for a few injection molded parts with very simple geometry, they occur on most injection molding parts (the shape is usually a line or V-shaped groove), especially Large complex items requiring the use of multi-gate molds and inserts. Weld-line is a weak area which reduces the strength of the part locally. Weld lines may appear like seams or scratches, but that is not what they are. Many studies were conducted to explain the weakness at the. Poor mold spot Spot mold to ensure fit and vent depths at ~0 . There are various types of injection molding defects that can cause such interruptions in the manufacturing cycle. In the above diagram, the converging flow fronts (indicated by red arrows. A visual mold with variotherm system for weld line study in micro injection molding. CrossRef View in Scopus Google Scholar [17] G. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. The welding angle can be used to differentiate weld lines and meld lines. The thin weld line is the result of weak material bonding, which lowers the strength of the part. but the injection pressure will loss and injection molding pressure of this gate is bigger than that of direct gate. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. The special injection mold is designed and fabricated to produce plaques having stagnation weld-line. Meld and knit lines are actually both different types of weld lines. Weld or knit lines occur when melt flow fronts collide in a mold cavity. 21: Weld line failure caused by hoop stresses. Weld lines can compromise the strength and aesthetics of the part, so it’s important to carefully design the mold. 025 100 120 140 160 180 200 220 240 Mold Temperature (F) LDPE PPAccording to the weld line distribution map of six gate schemes shown in . The thermo-rheological findings were used to investigate the sources of weld line weakness. 020 0. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. Flashes, 3. 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. Adjust the design for the flow pattern to be a single source flow. . A flat product case was considered as an example of a typical aircraft structural element. e. Unless you are manufacturing an extremely simple part with one gate and a unidirectional flow front, your part will have weld lines. 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. The results of. It forces out trapped air pockets and can prevent a vacuum void from occurring. 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. When this fails to happen correctly, a weld line defect occurs. 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. Co-injection molding technique is a useful way to study weld lines, which can offer more detailed information of the. ac. Materials Science. Weld line formation in the injection molding process occurs. Weld Lines. Flow rate is 24 cm3/s. Weld lines can appear on the surface of a molded part where the molten material has converged after splitting off in a mold. Int J Adv Manuf Technol 52:131–141. ). 10. Molding Equipment. Vents in the mold allow the mold to fill. Thus, it. Redesign the mold to. As these flow fronts come together. The second technique, cascade injection moulding, can produce parts free from weld lines. The flow of the material in the injection mould takes place through the gate. Injection molding of large/complicated products are usually prepared by multiple compounds, which produces weldlines once the melt fronts are joined by impingement flow. The molded plastic part may also appear to be rust-colored. 5. In the first, sequential injection moulding, the lines are displaced to noncritical areas of the moulding. Weld-line strength for plastics can vary from 20% to nearly 100% of the strength of the plastic itself. , a post that forms a hole) and then rejoins, or when polymer melt fronts meet, from multiple injection points. 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. The differences between knit and meld lines are significant, and they can dramatically impact the part’s structural integrity. 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. In this work, the residual strength of a fiber-reinforced injection molded part containing a hot weld line—or meld line—was evaluated. This customary mark is caused by differential rates of cooling in the resin where. The edge gate is the most popular and straightforward injection mold gate design. INJECTION MOULDING DEFECTS 1 DEFECTS 1. 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). 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. A quantitative evaluation of the appearance quality of weld lines in RHCM parts. To elimi- nate weld lines, you can enlarge shrinkage. 6. With Ixef® PARA compounds, the strength of a weld line is typically 90 MPa (13,000 psi). However, research about the computer determination of weld lines in injection molding remains scarce. Increase the injection speed to reduce the amount of cooling happening in the mold. The Influence of Knit-lines on the Tensile Properties of Injection Molded Parts, Polymer Engineering and Science, 23(10): 591-596. Flow marks in injection molding are defects that manifest as a line or series of lines forming a pattern different in color from the other parts of the molded material. 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]. Vacuum voids. Adjust Injection Molding Parameters: Optimizing injection speed, pressure, and temperature can help ensure better melt flow and reduce the likelihood of weld line formation. 7 of the reference. Possible causes: Low temperature or fluidity of melted plastic during injection molding. According to the studies, the most important factor to reduce weld lines is increasing the mold temperature. Weld lines are the unfavorable defect not only in normal injection molding process but in micro injection molding process. Weld line injection molding troubleshooting. Figure 1a illustrates how the weld line is produced when. The weld line is an inevitable defect in the most injection molded components. Abstract. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. Proceedings of ANTEC (2000) Google Scholar [9] S. In injection molding weld lines are formed whenever two flow fronts are joined. In an injection molding process, a weld-line forms when two flow fronts meet each other. When an external load is applied to a weld line region, the part’s potential for mechanical failure is increased. Runner Type Venting Plastic melt and mold temperature Injection speed and pressure Learn how to troubleshoot weld lines in injection molding. 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. The injection molding gate generates heat by dissipation. Weld. 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. Reduce the amount of release agents. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. Weld lines appear as a result of the flow of molten plastic during the injection molding process. If the different flow fronts have cooled. In Fig. + Increase mold temp, or materials’ temp, or holding pressure. 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. 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. This failure causes the product to be damaged during use. 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. 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. (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. 15 it can be found that for the opposite position of melt injection the weld lines forming under higher temperature would produce better plastics. Weld-line is a weak area which reduces the strength of the part locally. It is important to investigate the weld line because the weld line area can induce potential failure of structural application. Weld lines defects are formed when two flow fronts are merged together. In other words, weld lines reduce the mechanical properties of the product. 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. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. In this experiment, several ejector. The spreading mold release agent on the part cavity surface might eventually cumulate at the V-notch groove of the weld line after each injection molding shot. The weld line and the flow pattern of co-injection molding can be seen from Fig. Wang. 18/06/2021. 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. One test mold was used to mold three different materials using heat/cool and conventional molding techniques. This paper presents the. 2) show that the weld line is formed as expected from the middle of the cavity towards the wall. The weld-lines are undesirable from both aesthetic and functional points of view and their effect is different for. (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. Azuddin / Procedia Engineering 184 ( 2017 ) 663 – 672 665 2. 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. 1 m/s, and a zero-shear-rate viscosity η 0 (T 0)=3760 Pas. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. The Weld line result itself has a scale associated with the placement of the weld line that is directly relative to how severe the weld line will be based on the angle in which the two flow fronts meet. To explore the formation of weld lines in injection molding, a. Wu CH, Liang WJ (2005) Effects of geometry and injection-molding parameters on weld-line strength. Figure 1 below shows the development of a weld line. Mostly, this happens when two or more flow fronts do not “knit” during the injection molding process. In the 1947 book, Injection Molding of Plastics, the late Dr. Weld lines are one of the typical quality issues of injection molded parts. My polymer material selection courses 👉 Find Out About Plastics Blog👉 ht. 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. Thereby creating localized pressure within the mold. Adjust the position of the gate and include a venting slot. There will be too many weld lines ; 6. Change the flow pattern to a single-source flow. Weld lines can be caused by many reasons, which covers the various aspects of mold, process, raw materials and product design, etc. They. Increase the injection speed. If the large molded product is. Try to gradually raise the mold temperature and barrel temperature. Thicker parts require more cooling time and can lead to air becoming trapped in the mold and weld / knit lines to form. 010 0. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. Weld line location. It will degrade materials performance; 9. [ 18 - 21 ] In addition, the effects. 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. 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. In this work, the residual strength of a fiber-reinforced injection molded part containing a hot weld line—or meld line—was evaluated. Move injection locations to make weld lines form closer to the gates. Remedies: Raise the temperature of the mold or molten plastic. Wavy lines are another feature of weld lines. There are several possible causes that need to be investigated to troubleshoot weld lines in injection molding. Change the gate locations. A weld line is a mark left on the surface of a plastic injected molded part. (1) Increase the injection pressure and prolong the injection time. <Materials>Injection moulding (U. They decrease the. (1) Flash: Extra plastic material in the shape of films or burrs, which appears on the parting surface, around the runner or in the insert crevice. 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. In injection molding, a V-notch-shaped weld line [1] is generated in the melt front meeting area. In a weld line, reinforcement fibers adopt an orthogonal orientation with respect to the filling direction, which results in a significant reduction in the strength and. , 190°C mass and 20°C mold temperature, as well as. Using the conventional method, weld-line depths on the surface ranged from 6 to 13 microns. 030 0. Wavy lines are another feature of weld lines. This study focus on the formation of. Gate Placement: Properly positioning the gate can direct the melt flow to minimize weld lines or relocate the weld line to non-visible areas of the part. สาเหตุหลักชิ้นงานพลาสติกเกิดรอยเชื่อมประสาน (weld line) คือ การประสานหรือการรวมตัวกันของพลาสติกเหลวไม่ดีเท่าที่ควรThis insertion ensures the separation of the melt flow. Causes and Remedies of Sink Marks In Injection Molding. Micro weld lines are the common problem that occurs for plastic molded parts through injection molding process. 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]. The weld line is then created with a higher flow front temperature and is packed with more pressure. 3: Weld Lines. Injected plates were generated using a double-gated mold under four different process conditions. wall thickness, gate and runner designs and re-validate the result. The relative weld-line strength is defined as the ratio of the strength of specimens with a weld line. This process makes possible to produce a wide range of products with different sizes, shapes, and for varying applications. So today we are going to take a look at the five most common defects in injection molding and their solutions. Controlling the mold’s temperature could also minimize the weld line’s effects. (2011) and Fig. Yes, it does help, for two reasons: Often the weld line traps air and the ‘dump’ acts as a vent to allow the air to escape. While there are many situations where they are barely perceptible, weldlines represent a potential source of weakness in molded parts. 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. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. Injection molding weld lines where two or more flow fronts come together in the mold. Weld lines are a kind of Achilles heel of plastics. Increase the injection speed. An excess mold release is a major cause of weld line due to two variables: high pressure and speed. Edge Gates. Its properties make it possible to create thin-walled parts having close tolerances in fast cycles over long. 000 0. For multiple gate and complex part. Ideally, the resin flow will split into two flow fronts to pass around the obstruction and then recombine into a single flow front. As the polymer. 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. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. The weld line’s strength is reduced when. 22 shows how the weld lines are formed when the melt splits around core pins during the injection molding process. 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. A simulation of mold filling with multi-inlets or an insert in the cavity is pursued with an improved Level Set Method. Weld lines not only detract from an injection-molded part’s surface quality, but also significantly reduce its mechanical strength. 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. 13 shows the best gate location for which the weld lines . Optimizing the injection parameters through combination of adjusting the molding temperature, varying the gate pressure, and increasing the dwell time. Figure 1 a illustrates how the weld line is produced when two melt streams merge during the final filling process. 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. Venting at Weld Lines. The governing equations for the melt and the air in the cavity are united into…. 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. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. He now teaches courses in injection molding and plastic part design at the Polymers Center of Excellence and UNC-Charlotte in Charlotte, N. The foundation to any robust process, in my opinion, is based on choosing the correct fill time. Alter the mold design. Usually it’s a straight line, and often to be found radiating. To determine the effect of the weld lines on tensile strength, tensile tests were conducted with the specimens fabricated with NORYL (amorphous blends of. Meld lines are formed when two separate flow fronts meets. In order to increase the quality of the products manufactured by injection molding, RTC technology can be used to achieve higher mold temperatures. Jiquan Li, Taidong Li, +1 author. Despite injection molding being recognized as a robust process for obtaining parts with high geometry accuracy, one last occurrence remains a challenge in micro. ” Another. The goal is to create a uniform thickness and at the smallest (thinnest) level required. 1. [ 18 - 21 ] In addition, the effects of flow behavior of the polymer melt due to the optimal process parameters for the minimization of weld-line effects are an important consideration. It has larger cross-sectional regions that allow sufficient molten plastic flow into the cavity. Weld-line is a weak area which reduces the strength of the part locally. Another way to eliminate weld lines in plastic injection molding is to adjust the molding conditions. Which means engineers need to know how to account for this phenomenon in an efficient way. Second, depending on the size of the overflow well, you get a little bit of flow melding together, and that helps strength so that you have some intertwining of the polymer chains. Weld line. They occur when melt flow fronts collide in a mold cavity. Gates should be designed larger than normal and located to minimize weld line formation. So today we are going to take a look at the five most common defects in injection molding and their solutions. 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. Weld lines appear as a result of the flow of molten plastic during the injection molding process. The utility model relates to a mold structure capable of eliminating the appearance of weld lines of a hole-shaped injection molded product. Improper fusion of two fluid flows, a state before weld line. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection. Or increase the number of gates. Injection Molding Know How. When a product is produced through injection molding, a high-powered tool injects melted plastic into a custom, double-sided mold. In this study, the effects of injection temperature, injection pressure, and fiber cont. g. (3) Adjust the temperature of the barrel and nozzle: the viscosity. Weld lines have been one of the common defects puzzling the injection molding industry. 1. * Corresponding author, e-mail: fengsjpc@ku. The weld line degrades the. Weld Line defect analysis, the most common of many defects in injection moulding products. 2017-01-0481. Consultant @ Effinno Technologies, BSME, MBA - Bridge between Plastics Injection Molding Knowledge and Practice. In this study, we apply the technique of SAW to explore the acoustic properties near injection-weld lines by comparing the velocity of (V R) in locations close to and locations distant from the weldAmong defects of injection molding parts, weld lines are the most common defect. 025 100 120 140 160 180 200 220 240 Mold Temperature (F) LDPE PPThree terms that often get mixed up in the plastic injection molding industry are weld, meld, and knit lines. 2. 5. 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. In this study, epoxy molding compounds (EMC) filled with glass beads were fabricated with a twin-screw-extruder (TSE) and tempered before further processing to generate different degrees of cross-linking (0–15%) in the compounds. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties [3,4,5]. The micro tensile part was prepared by the double gate injection. During the plastic injection molding process, one of the biggest challenges is. Injected plates were generated using a double-gated mold under four different process conditions. 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. Double push filling method. This is expected to achieve maximum results while the pressure holding effect will also increase. 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. 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. Unless you are manufacturing an extremely simple part with one gate and a unidirectional flow front, your part will have weld lines. A weld line (weld point, flow line or a knit line) forms when separate melt fronts travelling in opposite directions meet. 2. The resulting defects don’t stop at flash only. Typical injection molding processing temperatures of TPU materials are as follows: IM Zone 60A to 75A 80A to 90A 95A to 75D Rear 315 – 40 ºF45 -370 75 400The weld line in an injection molding product can significantly impact the strength and durability of the last part [12] [13][14][15]. (3) Adjust the temperature of the barrel and nozzle: the viscosity. Knit and meld lines are inherent to plastic. 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. Injection molding can be performed with only one of these. Sink Marks Cause 2: Low Pack and Hold time. Features such as sharp corners or undercuts can. Polym Eng Sci 45(7. Weld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of injection‐molded parts. In this work, the residual strength of a fiber-reinforced injection molded part containing a hot weld line—or meld line—was evaluated. Polym. Weld Lines are formed when two or more molten polymer flows meet during the injection molding process. Weld lines. 18/06/2021. The special injection mold is designed and fabricated to produce plaques having stagnation weld-line. Three terms that often get mixed up in injection molding are weld, meld and knit lines. Polyamide-6 (PA-66) was used as. Insufficient plasticizing ability of injection molding machine. See moreEquipment. Meddad and Fisa [3] found that the weld line is a zone between 2 and 8 mm wide extending throughout the thickness in which the fibers are oriented almost. In this regard, the plasticizing ability of the plastic injection moulding machine should be checked. Controlling the mold’s temperature could also minimize the weld line’s effects. The plastic injection molding process, including thermoplastic injection, is nowadays used in several industrial processes, including in the automotive industry for bowden cables. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. The pressurized air restricts the flow of the plastic resin. The impact behavior of weld-lines in injection molding. Dischler, D. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. They decrease the. In the case of PC, the model predicts satisfactorily the weld-line strength as a function of injection temperature. The Solutions for Poor Welding Lines. Weld lines have been one of the common defects puzzling the injection molding industry. Discoloration. You will have to confirm them before tooling. 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]. 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. Usually it’s a straight line, and often to be found radiating away from a hole, inclusion or other such part feature. In an injection molding process, a weld-line forms when two flow fronts meet each other. Place a vent in the weld line area to remove the entrapped air. 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 gates. The position, length, and angle of weld lines are dependent on the. Effects of cavity surface temperature on mechanical properties of specimens with and without a weld line in rapid heat cycle. 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. The calculation was carried out on a mesh with solid elements obtained in ANSYS Meshing and transferred to Moldex3D by means Rhinoceros. The main runner and sub-runner are too thin. Islyn Thomas summarized the need for a particular vent location better than I ever could. • Optimize the design of the runner system. Introduction Weld lines are formed during mold filling whenever two separated melt streams recombine. In this paper, a weld line factor (W-L factor) was adopted to describe the. 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. 000 0. 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. The plaques are prepared out of 30% glass-filled Polyamide 6 material. To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. 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. M. In this case the two flow fronts will meet and there will be very little molecular orientation across the weld. Short shots. 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. 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. Figure 2. The weld line’s strength is reduced when. Gate Placement: Properly positioning the gate can direct the melt flow to minimize weld lines or relocate the weld line to non-visible areas of the part. In this lesson we will focus on the meld and weld lines. in the cavity of the injection mold. 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. 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. “I realized weld -line problems are a very common issue for injection molded parts,” Nicholson told Plastics Technology. When the polymer resin is injected into a mold, it flows through all portions of the mold cavity. Weld Lines-3 Ways for Detecting and Correcting. John Bozzelli. Sink MarksWeld 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. 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. Ghazanfarpour. 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. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. These potential causes include: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. , less than 0. Weld lines can be a weak spot and have therefore to be taken into consideration in part design. This month, in our FREE SimTech™ series of webinars, we will explore weld lines and how they develop. If you are familiar with any form of scientific injection molding, regardless of the name, then you know one of the first steps is performing a viscosity curve study. This failure causes the product to be damaged during use. 2017-01-0481. As the injection process continues, the two separated melt fronts meet again along the longitudinal section of the plate forming a weld line.