1. Fig. Figure 1 below shows the development of a weld line. Weld Lines. Sink marks, 2. Abstract. They decrease the. Weld lines defects are formed when two flow fronts are merged together. Poor mold spot Spot mold to ensure fit and vent depths at ~0 . Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. 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. The thermo-rheological findings were used to investigate the sources of weld line weakness. It is not always easy to completely eliminate weld lines by simply adjusting the relevant injection mold design or the molding conditions. Weld-line, a common occurrence in plastic injection moulding, is a representative defect compromising mechanical qualities and product appearance [16]. Weld lines can be caused by many reasons, which covers the various aspects of mold, process, raw materials and product design, etc. The vents must be deep enough to allow the trapped air and gasses to escape but not deep enough to allow the plastic to flash. 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. The following are the conclusion drawn from the present research: 1. 2. In an injection molding process, a weld-line forms when two flow fronts meet each other. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. enough to each other to avoid weld line issues. 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. Molding Equipment. To determine the effect of the weld lines on tensile strength, tensile tests were conducted with the specimens fabricated with NORYL (amorphous blends of. Figure 2. Weld-Line in an injection molded part develops when two or more melt fronts are converged together. 2) Vents in an injection mold should let the air out, but not the liquid plastic. In this paper, a weld line factor (W-L factor) was adopted to. The pressurized air restricts the flow of the plastic resin. Optimizing the injection parameters through combination of adjusting the molding temperature, varying the gate pressure, and increasing the dwell time. It is a well-known fact that weldlines are unavoidable in most injection-molded products of even moderate complexity. 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. 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. This process makes possible to produce a wide range of products with different sizes, shapes, and for varying applications. In injection molding, a V-notch-shaped weld line is generated in the melt front meeting area. 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. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. also utilized the co-injection molding technique to study the flow of polypropylene at the weld line behind an obstacle in injection molding; the weld line can be seen clearly from the Fig. 3 the path lines of selected material elements can be observed which are. 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. For more information on the Factors Affecting the Injection Molding Process. (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. th INTRODUCTION Injection molding is one of the mostWeld Lines in a plastic cover. Change the flow pattern to a single-source flow. 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. From Fig. Quality concerns in injection-molded materials can vary fr. the three-plate mold often adopt this kind of gate. These processing changes will increase chain. Injected plates were generated using a double-gated mold under four different process conditions. Weld Lines-3 Ways for Detecting and Correcting. Weld line defects – also known as knit lines – is a defect that occurs when the injected plastic meets within a mold. injection molding is followed by the welding. In this case the two flow fronts will meet and there will be very little molecular orientation across the weld. Jiquan Li, Taidong Li, +1 author. Process. Vacuum voids. Injection-molding machine is the Negri Bossi VE210-1700 with screw diameter 60 mm. Place a vent in the weld line area to remove the entrapped air. Burn Marks. 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. Gate blush, 4. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. In an injection molding process, a weld-line forms when two flow fronts meet each other. 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. This study focus on the formation of. The parts are molded flat and are slightly stressed once installed in an arced position, but not excessively. “I realized weld -line problems are a very common issue for injection molded parts,” Nicholson told Plastics Technology. Meld and knit lines are actually both different types of weld lines. Still, it can be seen to varied degrees depending on mold. Silver Streak. That’s the air escaping out of the nozzle until the hose is full of pressurized water. (1) Increase the injection pressure and prolong the injection time. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. M. 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]. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. 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. The Problems & Solutions course is designed to train injection molding personnel in. Weld lines not only detract from an injection-molded part’s surface quality, but also significantly reduce its mechanical strength. Wavy lines are another feature of weld lines. Proper venting is also required to ensure good weld-line quality. This special mould has changeable inserts to be able to inject with different gate types (standard, film, special-film, multi gates, etc. Mold temperature controlInjection mold designers can alter the position of weld line by changing the gate locating. when two or more melt flow fronts contact each other immediately after the cooling process. This model provides the necessary information. Edge Gates. Weld lines are a surface defect caused when two or more flow fronts come together during the injection process. 2004; To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. As these flow fronts come together. 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. The conditions are temperature, injection speed, and injection pressure. Injection molding can be performed with only one of these. Weld lines typically appear in a part when an obstruction of some kind separates the melt flow and prevents it from "knitting" together. The line where two resin flows “knit” or “weld” together during injection molding is called a weld or knit line. Vents in the mold allow the mold to fill. The utility model relates to a mold structure capable of eliminating the appearance of weld lines of a hole-shaped injection molded product. 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. The weld line in injection molding is created when two melt streams connect, as shown in Figure 1. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. Preventing sink marks of injection molded parts using CAE analysis. 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. wall thickness, gate and runner designs and re-validate the result. The welding angle can be used to differentiate weld lines and meld lines. 8. Insufficient plasticizing ability of injection molding machine. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. These lines occur when two or more flow fronts meet and fuse together, resulting in a visible seam on the molded part. Weld-line, a common occurrence in plastic injection moulding, is a representative defect compromising mechanical qualities and product appearance [16]. (1) Increase the injection pressure and prolong the injection time. Weld lines in injection molding are frequently unavoidable. 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. Thicker parts require more cooling time and can lead to air becoming trapped in the mold and weld / knit lines to form. The next type of injection molding defect is ‘Weld Lines’. 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. Unless you are manufacturing an extremely simple part with one gate and a unidirectional flow front, your part will have weld lines. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. Flow front tracing simulation results for weld line developing process in micro injection molding with Comsol ® Multiphysics 3. 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). Double push filling method. Weld lines have been one of the common defects puzzling the injection molding industry. 21: Weld line failure caused by hoop stresses. 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 weld line and the flow pattern of co-injection molding can be seen from Fig. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Redesign the mold to. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. Solving one problem can introduce other problems to the injection molding process. The thin weld line is the result of weak material bonding, which lowers the strength of the part. As the polymer. Expand. 5. Effects of cavity surface temperature on mechanical properties of specimens with and without a weld line in rapid heat cycle. Wolfgang Homes, head of the applications department of Eurotool, a manufacturer of hot runner systems, clarified the two methods for IMI, noting that. This study presents an innovative approach to enhancing weld line strength in advanced polymer injection molding through applying gas-assisted mold. In the above diagram, the converging flow fronts (indicated by red arrows. . Insufficient injection pressure and speed can cause weld lines. 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. Since it is often impossible to avoid weld lines as well as a limited possibility to increase the weld line strength by adjusting the injection molding parameters, a method to predict the weld line strength in the product development process is shown below. Azieatul Azrin Dzulkipli and M. 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. Weld line existence reduces the material strength; however, its demerit characteristics. Weld Line Phenomenon: Surface defect in which the weld, or the part where the flows of melted plastic meet inside the mold, shows up on the surface as a groove or pattern. การแก้ไข ชิ้นงานจุดที่เกิดความอ่อนแอบริเวณ weld line คือต้องใช้ความเร็วในการฉีดต่ำในจุด. 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. 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. 6. 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. There are several possible causes that need to be investigated to troubleshoot weld lines in injection molding. 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. Nguyen-Chung. Investigations on WLs in micro injection molded parts were performed in Refs. Mostly, this happens when two or more flow fronts do not “knit” during the injection molding process. With Ixef® PARA compounds, the strength of a weld line is typically 90 MPa (13,000 psi). In a meld line, the plastic comes together at an angle greater than 135 degrees. It forces out trapped air pockets and can prevent a vacuum void from occurring. Some of these are listed below: Plastic warpage. 5. The specific method is that when the product is just filled and filled in the cavity, the insert. Kobayashi et al. 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. Consultant @ Effinno Technologies, BSME, MBA - Bridge between Plastics Injection Molding Knowledge and Practice. In injection molding weldlines are generated when two separate melt streams join either in multigated molds or as a consequence of flow around. In Fig. Remedies: Reduce packing and fill rates by adjusting until the part is properly filled with minimum stresses. 10(a) (please see Fig. Article Google Scholar Deng YM, Zheng D, Lu XJ (2008) Injection moulding optimization of multi-class design variables using a PSO algorithm. 015 0. The second technique, cascade injection moulding, can produce parts free from weld lines. In our DFM report, we will analyze the possible weld lines. Although they often cannot be avoided it’s possible to minimize their cosmetic effects to an acceptable degree through careful product design and. 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. 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. This failure causes the product to be damaged during use. (3-1) Increasing the Resin Temperature at the Weld Line Section. ppt from SCIENCE 101 at Symbiosis International University. Recently hired at plastic injection molding simulation software provider Moldex3D, Nicholson was spurred to undertake the research study following a conversation with a customer experiencing weld-line woes. Weld or knit lines occur when melt flow fronts collide in a mold cavity. 2-1. 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]. 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. Weld Line defect analysis, the most common of many defects in injection moulding products. In places where the plastic flows around a solid piece of the mold, from a simple circle to forming complex shapes like rings or squares. Strength measurements should be made to. Weld lines. gasket seal leakage where the weld line crosses a gasket. Weld lines are one of the typical quality issues of injection molded parts. 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. Specifically, injection-mold lines are often associated with poor mechanical strength. Download : Download high-res image (856KB) Download : Download full-size image; Fig. Strength at weld the line location and warpage problem in injection molding plastic component were not new problems in injection molding industries. 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. . Wang, G. 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. First, an injection mold with triangular inserts was built to study the influence of meeting angles on material properties at the weld line. (3) Adjust the temperature of the barrel and nozzle: the viscosity. Maintain a holding pressure that is no more than 1/2 the. 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. 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. Weld lines in design for manufacture. 13 shows the best gate location for which the weld lines . Abstract. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright. Part design features may cause a material flow to split and rejoin as it flows around design features in a mold. The rule is, a higher pressure shall be required to push the material in the machine when there is excess mold. These lines. ”. 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. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. Weld line, 5. With unchangeable and fixed requirements for the final product, their avoidance often proves difficult. Wu CH, Liang WJ (2005) Effects of geometry and injection-molding parameters on weld-line strength. 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. Meld lines are formed when two separate flow fronts meets. 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. Dischler, D. This line does not normally impact the overall shape or dimensions of the item. Sink marks are a common type of injection molding defect. In this work, the weldline strength of injection molded short-glass-fiber reinforced polycarbonate was derived by an analytical method of modified rule-of-mixtures as a function of the area fraction between skin and core layers. Improvement of weld line strength in injection molded FRTP articles. 015 0. Weld-line yield strength, yield strain, and failure strain of talc-filled polypropylene increase with increasing melt temperature and increasing hold pressure. Weld lines appear as a result of the flow of molten plastic during the injection molding process. Weld line section presents notch or gloss difference. in the cavity of the injection mold. 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. Weld Lines. [ 18 - 21 ] In addition, the effects. During the plastic injection molding process, one of the biggest challenges is. 2. The hair-like weld line is the. 15 it can be found that for the opposite position of melt injection the weld lines forming under higher temperature would produce better plastics. 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. (a) (b) Figure 1. 2. . Short shots. In. Weld Lines. 15 shows the frozen layer and weld lines at the end of mold filling. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. In this work, the residual strength of a fiber-reinforced injection molded part containing a hot weld line—or meld line—was evaluated. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. Discoloration. 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. This paper presents the. Ejector System (Pötsch, 1995) . 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]. Flow-induced filler orientation manifests in higher tensile prop-erties in the direction of flow compared to those normal to the direction of flow. Introduction. Although they often cannot be avoided it’s possible to minimize their cosmetic effects to an acceptable degree through careful product design and manufacturing. This weld line can act as a weak spot in the material. As the plastic flows through the mold it forms a smooth and continuous flow front. Use a less viscous plastic. Too high barrel temperature ( abnormal temperature control, deviation of material performance, and increasing cycle time); 8. Multiple gating, splitting of the melt flow due to inserts in the cavity or through holes, as well as changes of thickness give rise to points within the structure where the flowing fronts will recombine and weld. 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 in injection molding are a type of cosmetic defect that detracts from a plastic part’s appearance. analyzed the heat transfer during heating and cooling phases of RHCM process. The main runner and sub-runner are too thin. 2020-01-1306. In this regard, the plasticizing ability of the plastic injection moulding machine should be checked. Weld lines have been one of the common defects puzzling the injection molding industry. 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. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. In a weld line, reinforcement fibers. The more gate points there are, the more weld lines will occur. Avoid knit lines when designing a molded part to improve cosmetic appearance and functionality. Weld-line is a weak area which reduces the strength of the part locally. The weld lines in injection molded parts arise as a result of the collision of two fronts of the flowing material, which fills the mold cavity and are sometimes unavoidable [1][2][3] [4]. See moreEquipment. Increase the injection speed to reduce the amount of cooling happening in the mold. A viscosity curve is developed using calculations of the fill time and plastic pressure at. After that, the compounds were injection-molded into tensile samples with and without weld lines to. 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]. 2017-01-0481. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. Mérillou, J. Weld lines are one of the typical quality issues of injection molded parts. When injection molding large products, molding is usually performed with multi-point gates, but weld lines can occur depending on the product shape and gate position. 1. The foundation to any robust process, in my opinion, is based on choosing the correct fill time. 9 – Over Packing. The weld line’s strength is reduced when. The injection molding temperature and the mold temperature were fixed respectively at 230 °C and 50 °C. 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. 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 is expected to achieve maximum results while the pressure holding effect will also increase. A weld line is a mark left on the surface of a plastic injected molded part. <Mold> Provide a cold slug well where weld lines occur. Weld-line is a weak area which reduces the strength of the part locally. Weld line existence reduces the material strength; however, its demerit characteristics. 8. In this paper, two different injection molding tests were completed. In this experiment, several ejector. 3. Definition: A seam that appears where two areas of molten plastics meet. The edge gate is the most popular and straightforward injection mold gate design. but the injection pressure will loss and injection molding pressure of this gate is bigger than that of direct gate. In this regard, the plasticizing ability of the plastic injection moulding machine should be checked. 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 melt stream is separated at the part’s cutout and reunited at the other end of the cutout. The special injection mold is designed and fabricated to produce plaques having stagnation weld-line. 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. Weld lines are the unfavorable defect not only in normal injection molding process but in micro injection molding process. When two or more streams of plastic meet and fuse. + Increase mold temp, or materials’ temp, or holding pressure. The thermo-rheological findings were used to investigate the sources of weld line weakness. Flow Lines. 2. Weld line formation in the injection molding process occurs. Injected plates were generated using a double-gated mold under four different process conditions. Causes and Remedies of Sink Marks In Injection Molding. Effects of mold temperature and pressure on shrinkage 0. The impact behavior of weld-lines in injection molding. In addition a weld line can be moved to an area where it is less visible. If weld lines are unavoidable due to multiple gates in a moulding, they should be positioned in the non-critical region. The rule is, a higher pressure shall be required to push the material in the machine when there is excess mold. Abstract. 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. , 2 (3–4) (1988. 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. There will be too many weld lines ; 6. (3-1) Increasing the Resin Temperature at the Weld Line Section. Injection molding of large/complicated products are usually prepared by multiple compounds, which produces weldlines once the melt fronts are joined by impingement flow. 2. Remedies: Raise the temperature of the mold or molten plastic. Venting at Weld Lines. When the two such melt flows. Google Scholar | Crossref | ISI. Thus, it. Weld lines may appear like seams or scratches, but that is not what they are. 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. This reduced thickness of the frozen skin further enhances the visual appeal of the. Voids and bubbles, 6. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. 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. Islyn Thomas summarized the need for a particular vent location better than I ever could. Try to gradually raise the mold temperature and barrel temperature. The position, length, and angle of weld lines are dependent on the. As the injection process continues, the two separated melt fronts meet again along the longitudinal section of the plate forming a weld line. Gate location should set to avoid weld lines, keep clean of the important position of the products,. As the polymer resin is injected into a mold, it flows through all parts of the mold. They. . 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. Stop using mold parting agents. The Solutions for Poor Welding Lines. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. Which means engineers need to know how to account for this phenomenon in an efficient way. A weld or meld line is a weakness or visible flaw created when two or more flow paths meet during the filling process. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. This gives a clue as to how it was formed. The weld lines that occur in injection mouldings are critical areas on which depends on the strength of the mouldings. GlossFlow-induced fiber orientation and weld lines are com-mon features of the injection molding process. In the 1947 book, Injection Molding of Plastics, the late Dr. The primary cause of cracking is stress and deformation brought on by the external environment, cold mold surfaces, and low injection rates. When the same pressure is maintained or lower than that, the drop in speed shall create the weld lines. Weld lines have been one of the common defects puzzling the injection molding industry. Edge Gates. 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. 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. In weak material bonding, they will appear as hair-like weld lines. Redesign the mold to prevent the weld line. injection molding, (b) weld line and meld line, and (c) injection sample size and shape. Increase the injection speed. T. Injected plates were generated using a double-gated mold under four different process conditions. Besides, possibly it would be. Int. Blistering 4. The most common method for the weld-line characterization is mechanical testing by means of a tensile or bend stage [6,7]. In this paper, a weld line factor (W-L factor) was adopted to describe the. 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. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. Change the gate locations. Amongst weld line. 4. + Improve vent inside the mold. Weld line. 1. Ghazanfarpour. Known also as knit lines and weld marks, weld lines are difficult to eliminate completely, especially if your injection molded part requires holes. (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. The plastic injection molding process, including thermoplastic injection, is nowadays used in several industrial processes, including in the automotive industry for bowden cables. Weld lines can significantly reduce ultimate tensile strength (UTS) and fracture strain of talc filled polypropylene (PP). If the melt temperature is low or the injection speed and pressure are low, you may end up with a more pronounced weld line. Weak weld lines are perhaps the most common and difficult injection molding defect to eliminate. Remedies: Raise the temperature of the mold or molten plastic. Instead, a line that looks like a seam forms. 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. 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 weldSince weldline in plastic injection molding (PIM) has an influence on not only the strength but also the surface appearance of a plastic product, it is preferable to reduce it as much as possible for high product quality. The edge gate is the most popular and straightforward injection mold gate design. 000 0.