These are caused by the shot of molten plastic moving at different speeds throughout the injection. Vents in the mold allow the mold to fill. Weld lines typically appear in a part when an obstruction of some kind separates the melt flow and prevents it from "knitting" together. Experimental Setup 2. The terahertz time-domain spectroscopy (THz-TDS) imaging technique was used to detect the weld line defect of an injection-moulded short glass fiber-reinforced composite. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. Remedies: Raise the temperature of the mold or molten plastic. 1. • Move injection locations to make flow fronts meet more obliquely, turning the weld line into a meld line. In the injection molding process, weld line regions occur when a molten polymer flow front is first separated and then rejoined. Sink marks, 2. The plaques are prepared out of 30% glass-filled Polyamide 6 material. Clamping Unit. These are preferred over weld lines as they will normally result in improved cosmetics and structure. 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. Fisa et al. Weld line formation in the injection molding process occurs when two or more melt flow fronts contact each other immediately after the cooling process. Participating in DFM and mold flow analysis is a good way to achieve this. It is important to investigate the weld line because the weld line area can induce potential failure of structural application. Weld line, 5. Kobayashi et al. The three parameters affecting operation were called injection pressure, injection time, and packing pressure which influence the quality of weld line. 000 0. You can expect a mold shrinkage percentage of. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. The authors [5, 6] attempted to reduce the weld lines and clamping force of plastic injection moulding through numerical and experimental investigation, and discovered that the 3D cooling channel. Increase the injection speed and mold/operational temperature to prevent fracture or surface breakdown. Change the gate locations so that the weld lines occur in locations less susceptible to external forces if weld strength is an issue. The difference between a weld and meld line is simply determined by the angle at which the converging flow fronts meet. Weld lines have been one of the common defects puzzling the injection molding industry. wall thickness, gate and runner designs and re-validate the result. They become more critical when particulate fillers are compounded with the polymer. Still, it can be seen to varied degrees depending on mold. Adjust the position of the gate and include a venting slot. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. As compared to a weld line, the flow fronts come together at less than 135 degrees. , 190°C mass and 20°C mold temperature, as well as. View 08 DEFECTS & REMEDIES (61). 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. Here’s how to decrease the chances of weld lines: Increase the temperature of the mold or the molten plastic. This may require higher melt temperature or lower injection speed . Threadline gap in-between part due to improper gate location in complex design parts including excess of holes (multipoint. The relative weld-line strength is defined as the ratio of the strength of specimens with a weld line. [ 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. T. 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 main runner and sub-runner are too thin. Many studies were conducted to explain the weakness at the. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. To elimi- nate weld lines, you can enlarge shrinkage. The position, length, and angle of weld lines are dependent on the. Abstract. Download : Download high-res image (856KB) Download : Download full-size image; Fig. In this work, the residual strength of a fiber-reinforced injection molded part containing a hot weld line—or meld line—was evaluated. When the two such melt flows. That’s the air escaping out of the nozzle until the hose is full of pressurized water. Article Google Scholar Deng YM, Zheng D, Lu XJ (2008) Injection moulding optimization of multi-class design variables using a PSO algorithm. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. Weld line existence reduces the material strength; however, its demerit characteristics. 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. Proper venting is also required to ensure good weld-line quality. (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. Increase the injection speed to reduce the amount of cooling happening in the mold. 2. 015 0. The edge gate is the most popular and straightforward injection mold gate design. + Optimize holding pressure time. Short shots. Proceedings of ANTEC (2000), pp. when two or more melt flow fronts contact each other immediately after the cooling process. But add 30% glass and weld-line strength retention drops to only 34% as high as the compound with no weld. Injection molding plate for mode I testing geometry. Edge Gates. 13 shows the best gate location for which the weld lines . Weld Lines-3 Ways for Detecting and Correcting. (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. First, an injection mold with triangular inserts was built to study the influence of meeting angles on material properties at the weld line. With tighter heat controls, you can keep the material at the proper temperature to make sure the plastic keeps flowing and fills the mold cavity completely. Too high barrel temperature ( abnormal temperature control, deviation of material performance, and increasing cycle time); 8. 2017-01-0481. 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. 2. Weld line injection molding troubleshooting. 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. The Solutions for Poor Welding Lines. Lesson 6: Meld and Weld Lines (Processing) When plastic flows into an injection mold, the internal flow pattern depends on the part design, mold design, and processing factors. 2021年4月23日 / by admin. . 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. when two or more melt flow fronts contact each other immediately after the cooling process. Except for a few injection molded parts with very simple geometry, weld lines occur in most injection molded parts (usually with one line or V-shaped groove), especially in large-scale complex products requiring multi gate mold and inserts. He now teaches courses in injection molding and plastic part design at the Polymers Center of Excellence and UNC-Charlotte in Charlotte, N. In this paper, two different injection molding tests were completed. When the same pressure is maintained or lower than that, the drop in speed shall create the weld lines. For more information on the Factors Affecting the Injection Molding Process. To respond to poor plasticization and uneven melt temperature,. Wavy lines are another feature of weld lines. 8. Weld-line yield strength, yield strain, and failure strain of talc-filled polypropylene increase with increasing melt temperature and increasing hold pressure. Its properties make it possible to create thin-walled parts having close tolerances in fast cycles over long. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. In addition a weld line can be moved to an area where it is less visible. 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 the result of fundamental physical effects taking place inside of the mold tool cavity, they are common imperfection to be found in most plastic injection molded parts. To determine the effect of the weld lines on tensile strength, tensile tests were conducted with the specimens fabricated with NORYL (amorphous blends of. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. Optimizing the injection parameters through combination of adjusting the molding temperature, varying the gate pressure, and increasing the dwell time. 020 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 is a defect that arises in injection molding when two or more flow fronts collide. [ 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. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. This customary mark is caused by differential rates of cooling in the resin where. Fig 13:- Detailed view of weld lines. Weld lines may occur depending on the product shape and gate positions. Adjust Injection Molding Parameters: Optimizing injection speed, pressure, and temperature can help ensure better melt flow and reduce the likelihood of weld line formation. Weld Lines-3 Ways for Detecting and Correcting. Weld-line strength for plastics can vary from 20% to nearly 100% of the strength of the plastic itself. The quality of the weld line can be improved through optimized processing conditions, increased mold and melt temperatures, and increased injection speed to reduce the viscosity of the polymer. Injected plates were generated using a double-gated mold under four different process conditions. The injection molding temperature and the mold temperature were fixed respectively at 230 °C and 50 °C. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. The 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. Unless you are manufacturing an extremely simple part with one gate and a unidirectional flow front, your part will have weld lines. 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. 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. Flow analysis of the weld line formation during injection mold filling of thermoplastics. A simulation of mold filling with multi-inlets or an insert in the cavity is pursued with an improved Level Set Method. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection. 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. 1. 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. Change the gate locations. 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. ac. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. Flash. One test mold was used to mold three different materials using heat/cool and conventional molding techniques. Int J Adv Manuf Technol 52:131–141. Ghazanfarpour. Increase the injection speed. Fellahi et al. 000 0. 5. 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. 2-1. Melt temperature does effect the weld. Weld lines appear as a result of the flow of molten plastic during the injection molding process. That helps. The primary cause of cracking is stress and deformation brought on by the external environment, cold mold surfaces, and low injection rates. 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. Thus, a right gate design raises polymer temperature to prevent the formation of weld lines and flow marks. Therefore, it is recommended to do a moldflow study prior to the mold being built. 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. ” Another. 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. Weld lines in injection molding are a type of cosmetic defect that detracts from a plastic part’s appearance. Sink marks. A weld or meld line on plastic parts can cause structural problems and/or be visibly unacceptable. There will be too many weld lines ; 6. Google Scholar | Crossref | ISI. To prevent knit lines, injection molders can increase the temperature of the molten resin to prevent solidification from starting too soon, and increasing injection speeds and pressure are also potential solutions. In the case of PC, the model predicts satisfactorily the weld-line strength as a function of injection temperature. From Fig. In spite of its cosmetic attributes, a bad knit line can significantly. When the same pressure is maintained or lower than that, the drop in speed shall create the weld lines. Gambar 2. 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. ac. 2. EasyFill Advanced provides the weld-line temperature distribution and meeting angle prediction. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection molding processing. Weld line existence reduces the material strength; however, its demerit characteristics. A weld line is a mark left on the surface of a plastic injected molded part. (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. GlossFlow-induced fiber orientation and weld lines are com-mon features of the injection molding process. 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. Sink Marks 2. 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. also utilized the co-injection molding technique to study the flow of polypropylene at the weld line behind an obstacle in injection molding; the. . In this case the two flow fronts will meet and. Injection-molding machine is the Negri Bossi VE210-1700 with screw diameter 60 mm. 020 0. In injection molding, a V-notch-shaped weld line [1] is generated in the melt front meeting area. Abstract. Effect of the processing conditions on the variations of the bulk temperature, T b , at the end of mold filling at the two locations: in (left) and away (right) from the weld-line (T w , T inj. Weld lines, created in the areas of collision of two flow fronts of plastic in the injection mold cavity, are the reason of lower mechanical properties and a worse surface condition of molded parts. 1. 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. Polym Eng Sci 45(7. 2. As the polymer resin is injected into a mold, it flows through all parts of the mold. are very minimum. The weld-lines are undesirable from both aesthetic and functional points of view and their effect is different for. In injection molding weldlines are generated when two separate melt streams join either in multigated molds or as a consequence of flow around. Adjust the design for the flow pattern to be a single source flow. Controlling the mold’s temperature could also minimize the weld line’s effects. 15 shows the frozen layer and weld lines at the end of mold filling. Emerging Materials Research. Flash. Weld lines are where two flow. Weld Line Factors for Thermoplastics. Maintain a holding pressure that is no more than 1/2 the. This is a video excerpt from our Problems & Solutions Course - Weldlines. 7 in Kobayashi et al. They are the result of fundamental physical effects taking place inside of the mold tool cavity. 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]. . As a result this weld line will be a weak point in this part. The Solutions for Poor Welding Lines. avoid weld lines, and facilitate smooth. Lesson 7: Meld and Weld Lines (Part Design) When plastic flows into an injection mold, the internal flow pattern depends on the part design, mold design, and processing factors. Improper fusion of two fluid flows, a state before weld line. In narrow fields, a limited amount of molten liquid can solidify and block the flow. Therefore, it is recommended to do a moldflow study prior to the mold being built. As the plastic flows through the mold it forms a smooth and continuous flow front. In the first stage, the two part halves are injection molded and then, in a second process step outside of the molding machine, they are welded together. poor flow fronts that are too cold, this can also lead to a deterioration in the mechanical properties. 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. Instead, a line that looks like a seam forms. One method is the local te mpering of the affected areas to prevent weld lines. Move injection locations to make weld lines form closer to the gates. A weld line can appear during the absence of enough pressure to push the plastic flow and then meld together. The need to minimize fiber breakage, plus the higher viscosity of materials with. e. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. The Difference Between Knit and Meld Lines–and Why It Matters. The most common and one of the most challenging injection molding defects are weld and knit lines. Heat/cool injection molding has a positive influence on the depth and visibility of weld lines. The most common method for the weld-line characterization is mechanical testing by means of a tensile or bend stage [6,7]. Flow-in-duced fiber orientation manifests in higher tensile properties in the direction of flow compared to normal to the direction of flow [13–15]. During injection moulding, a weld-line occurs when two or more flow fronts collide in the hollow cavity. In many cases, you will also see that the part is hanging up on the core during ejection. But none of the current packages can predict weld lines’ properties qualitatively. What is weld lines. (1) Increase the injection pressure and prolong the injection time. A simulation process was conducted to determine the recommended setting of injection moulding parameters and the range of the variable. Flow Lines and Weld Lines. In injection molding, it is often important to maintain consistent color throughout the part. This study examines the impact of injection parameters on the weld line strength of the polyamide 6 and 30% fiberglass (PA6 + 30% FG) composite samples. The appearance quality of plastic parts in weld lines can be improved significantly through the rapid heating cycle molding (RHCM). A viscosity curve is developed using calculations of the fill time and plastic pressure at. , 2 (3–4) (1988. In this experiment, several ejector. It occurs when melting plastic material is injected into a mold, it flows through all parts of th. 4 at different time steps (legend scale is volume fraction of. They appear on the surface of injection molded parts like lines. To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. 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. To explore the formation of weld lines in injection molding, a. The default weld line result recognizes 135º as the maximum angle of collision and as that angle decreases, the severity increases as it. It has larger cross-sectional regions that allow sufficient molten plastic flow into the cavity. Weld line section presents notch or gloss difference. The hair-like weld line is the. A weld line (weld point, flow line or a knit line) forms when separate melt fronts travelling in opposite directions meet. A poor knit line can cause only cosmetic blemishes or it can significantly weaken the structural integrity of a part. + Improve vent inside the mold. The thin weld line is the result of weak material bonding, which lowers the strength of the part. My polymer material selection courses 👉 Find Out About Plastics Blog👉 ht. Founder, Injection Molding Solutions. Silver Streak. Or increase the number of gates. In this paper, a weld line factor (W-L factor) was adopted to. Adding vents, using overflows, or using porous metal. In our DFM report, we will analyze the possible weld lines. These processing changes will increase chain. Wang. 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. Weld lines can appear on the surface of a molded part where the molten material has converged after splitting off into two or more directions in a mold. Injection pressures too high Reduce pressure . Dischler, D. Weld line defects in injection molding is a line or lines on the part surface that caused the part looking ugly or cuased part lifetime, or even broken easily. The 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]. Figure 1 below shows the development of a weld line. Stop using mold parting agents. Meanwhile, Using more advanced cooling method such as cyclic cooling or conformal cooling. (1) Increase the injection pressure and prolong the injection time. Figure 2. G. This article will review how and why weld lines occur, how mold gates effects weld line location and strength, the importance of material selection and Injection molding weld lines refer to a line on an injection molded part that is generated where the two halves of the mold come together. 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). They occur when melt flow fronts collide in a mold cavity. 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. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. Investigations on WLs in micro injection molded parts were performed in Refs. The injection molding process can be optimized to maximize weld line strength by increasing mold and melt temperatures, and by increasing pack pressure at the weld line. Redesign the mold to prevent the weld line. + Adjust injection speed. Avoid knit lines when designing a molded part to improve cosmetic appearance and functionality. Meld Lines. Bubbles are caused by melting flow fronts colliding in a mold cavity. The gate location should enable the two flow fronts to merge easily and continue to flow beyond the weld line. In this case the two flow fronts will meet and there will be very little molecular orientation across the weld. If the large molded product is. A weld line is often unavoidable. Other possible causes include: Low mold or material temperature; Insufficient holding time or. If the plastic encounters a pin or other obstruction, the plastic flow front must split to form two flow fronts to go around the pin. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Poor mold spot Spot mold to ensure fit and vent depths at ~0 . 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. The calculation was carried out on a mesh with solid elements obtained in ANSYS Meshing and transferred to Moldex3D by means Rhinoceros. The Influence of Knit-lines on the Tensile Properties of Injection Molded Parts, Polymer Engineering and Science, 23(10): 591-596. 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 weld line can act as a weak spot in the material. 080 inches. Weld lines are formed when two or more flow fronts join, as the liquid polymer fills the. They decrease the. This month, in our FREE SimTech™ series of webinars, we will explore weld lines and how they develop. Weld lines defects are formed when two flow fronts are merged together. Flashes, 3. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. 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. The impact behavior of weld-lines in injection molding. Weld-line, a common occurrence in plastic injection moulding, is a representative defect compromising mechanical qualities and product appearance [16]. In a weld line, reinforcement fibers. Fig. Three terms that often get mixed up in injection molding are weld, meld and knit lines. This failure causes the product to be damaged during use. These lines. 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’s strength is reduced when. Weld Line defect analysis, the most common of many defects in injection moulding products. 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. 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. Mold temperature controlInjection mold designers can alter the position of weld line by changing the gate locating. A knit line may be unnoticeable or may look like a crack. Weld lines, generated during injection molding, can significantly reduce the mechanical performance of structures. It will degrade materials performance; 9. When a product is produced through injection molding, a high-powered tool injects melted plastic into a custom, double-sided mold. Weld lines are visually undesirable and a plastic part is structurally weak at weld line positions. This special mould has changeable inserts to be able to inject with different gate types (standard, film, special-film, multi gates, etc. Clamping unit berfungsi untuk memegang dan mengatur gerakan mold unit, serta gerakan ejector saat melepas benda dari molding unit, pada clamping unit lah kita bisa mengatur berapa panjang gerakan molding saat dibuka dan seberapa panjang ejector harus bergerak. 15 it can be found that for the opposite position of melt injection the weld lines forming under higher temperature would produce better plastics. These lines can occur due to variations in wall thickness, gate location, or the geometry of the part. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. (3) Adjust the temperature of the barrel and nozzle: the viscosity. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. Mold vents should function the same way. According to the studies, the most important factor to reduce weld lines is increasing the mold temperature. 3. Plastic Injection Molding Process. 453-455. Sequential valve gate technology. The following are the conclusion drawn from the present research: 1. The part becomes partially solidified and won’t sufficiently bond where the two halves meet, resulting in. The results of. In order to increase the quality of the products manufactured by injection molding, RTC technology can be used to achieve higher mold temperatures. 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. Strength at weld the line location and warpage problem in injection molding plastic component were not new problems in injection molding industries. 4. Discoloration. The weld line’s strength is reduced when. (2011) and Fig. [1-2] investigated the weld line zone of injection molded glass-fiber-filled polypropylene (PP) composites. 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. [1] The best we can hope for is to pressurize the knit or meld line better through the combination of melt temperature, mold temperature, flow rate, and holding pressure. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. In the sense that the weld line is better formed before the resin temperature. With unchangeable and fixed requirements for the final product, their avoidance often proves difficult. Root causes Many factors—including processing conditions, material, part design and mold design—can influence the visibility and strength of a weld line. Here are a few of the most common defects that may occur in plastic injection molding — and how product teams can avoid them. 4. In an injection molding process, a weld-line forms when two flow fronts meet each other. Gate location should set to avoid weld lines, keep clean of the important position of the products,. Weld Lines. a) Multi-fiber connector micro injection molding simulation b) 3D simulation of micro gear with 150µm diameter for weld line position prediction c) 3D micro injection molding filling simulation of micro gear with 180µm diameter Fig.