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. . The second technique, cascade injection moulding, can produce parts free from weld lines. Article Google Scholar Xie L, Ziegmann G (2009) Influence of processing parameters on micro injection molded weld line mechanical properties of polypropylene (PP). A visible weld line is observed, due to a combina-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. 9. 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. Flow analysis of the weld line formation during injection mold filling of thermoplastics. Munich, Germany: Carl Hanser Verlag, 1994. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. S. Remedies: Raise the temperature of the mold or molten plastic. If the different flow fronts have cooled. A poor knit line. on conventional reciprocating screw injection molding machines using molding practices standard for filled engineering thermoplastics . 015 0. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. Weld Lines are formed when two or more molten polymer flows meet during the injection molding process. In. 2. Reposition gates and runners to allow resin to flow around the obstruction from a. Mobile 0813; Shinko Sellbic Co. Injection molding is one of the most established and well-known methods of plastic processing. This paper analyzes production data from injection molding processes to identify key interactions between the process variables from different material categories using the network inference method called “bagging conservative causal core network” (BC3net). Weld lines. The impact behavior of weld-lines in injection molding. That’s the air escaping out of the nozzle until the hose is full of pressurized water. 6. How Are They Formed? Molten plastic resin is injected into a mold cavity through an opening known as a gate. Plastic part design for injection molding – An introduction. 2. 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-line is a weak area which reduces the strength of the part locally. The flow of the material in the injection mould takes place through the gate. Sink Marks Cause 2: Low Pack and Hold time. 5. Meld lines are formed when two separate flow fronts meets. 005 0. However, even with advanced technologies and precise control, the process is not without its challenges. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. + Increase mold temp, or materials’ temp, or holding pressure. Sink marks are a common type of injection molding defect. Weld line injection molding troubleshooting. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Consultant @ Effinno Technologies, BSME, MBA - Bridge between Plastics Injection Molding Knowledge and Practice. During injection moulding, a weld-line occurs when two or more flow fronts collide in the hollow cavity. 1, right). In a meld line, the plastic comes together at an angle greater than 135 degrees. The thermo-rheological findings were used to investigate the sources of weld line weakness. 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. 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. Flow-induced filler orientation manifests in higher tensile prop-erties in the direction of flow compared to those normal to the direction of flow. These are preferred over weld lines as they will normally result in improved cosmetics and structure. 8. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection. Weld-Line in an injection molded part develops when two or more melt fronts are converged together. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. Mold. 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. Proper venting is also required to ensure good weld-line quality. Weld lines are a common occurrence in injection molding that affects the overall quality and strength of a finished product. สาเหตุรองของการเกิดปัญหาการเกิดประกายเงิน (silver streak) 1. are very minimum. When molten plastic flows, it forms a smooth continuous flow until it meets an obstruction. Bubbles are caused by melting flow fronts colliding in a mold cavity. When two or more streams of plastic meet and fuse. The Problems & Solutions course is designed to train injection molding personnel in. Weld lines have been one of the common defects puzzling the injection molding industry. The molded plastic part may also appear to be rust-colored. 020 0. 1. technical ulletin SPECIALTY POLYME RS Design and Production of Injection Molding ToolsWeld lines have been one of the common defects puzzling the injection molding industry. Its appearance can be improved by adjusting parameters. In order to prepare the weld line specimen by micro injection molding, a mould integrated with visual system and variotherm system was designed and constructed, shown as Fig. reinforcement type and amount in nylon 6/6. Set up the process overflow and use it as the place where the weld line is generated, and then cut off and remove it after forming. Keywords: Flow behavior , Injection molding , Particle tracking , Visualization , Weld-line Article MetricsSimulations and experiments were conducted with gas temperatures of 200–400 °C to investigate the impact of external gas-assisted mold temperature control (Ex-GMTC) on the quality of weld line of molding products. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. Bociaga and Jaruga (2007) investigated flowing weld line in injection process by injection molding machine, which the part surface was observed in reflected light using the optimal microscope and. 5. 015 0. 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. Weld lines can significantly reduce ultimate tensile strength (UTS) and fracture strain of talc filled polypropylene (PP). Sink Marks Cause 5: Improper Part Geometry. Increase the injection speed to reduce the amount of cooling happening in the mold. of micro injection molding process simulation by technology update and progress. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. In injection molding, it is often important to maintain consistent color throughout the part. 1 Prediction of weld lines with injection molding simulation softwareWeld lines in design for manufacture. Amongst weld line. 4If the injection gate is not properly designed, it can cause the formation of defects like sink-mark, warpage, short shot, weld-line, air traps, and other faults [15]. Sink Marks Cause 4: High Mold Temperature. Weld lines can be caused by many reasons, which covers the various aspects of mold, process, raw materials and product design, etc. Ideally, the resin flow will split into two flow fronts to pass around the obstruction and then recombine into a single flow front. Injection Molding Glossary; Weld Lines; Weld Lines. in the cavity of the injection mold. After that, the compounds were injection-molded into tensile samples with and without weld lines to. [ 18 - 21 ] In addition, the effects. G. 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]. But add 30% glass and weld-line strength retention drops to only 34% as high as the compound with no weld. Fracture behavior of weld lines in injection molded components loaded under real operating conditions. A micro-photography study on the cross-section of the weld-line was also carried out. How to Reduce Weld Line in Injection Molding? Weld lines are a common issue that occurs in injection molding. 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. Injection-molding machine is the Negri Bossi VE210-1700 with screw. If the plasticizing ability of the plastics injection molding machine is insufficient, the plastic. Methodology. (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. For thick-walled parts, slow injection rates result in more uniform polymer distribution . Below is one of the examples: !NOTE: if the weld lines is important to the cosmetic surface of your part, please bring this up to your mold maker during quoting phase. Fiber content dependence on. This is expected to achieve maximum results while the pressure holding effect will also increase. DescriptionThis insertion ensures the separation of the melt flow. 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. Weld lines are formed when there is an inability of two or more flow fronts to ‘knit’ or ‘weld,’ together during the molding process. They can affect the strength and appearance of the part, depending on the temperature, pressure, speed, and mold design of the injection molding process. (1) make the mold vent larger at location with weld line; (2) Check if the mold vent is blocked or not or use vacuumized forming. Remedies: Reduce packing and fill rates by adjusting until the part is properly filled with minimum stresses. The position, length, and angle of weld lines are dependent on the. To explore the formation of. Wang, G. (1) Increase the injection pressure and prolong the injection time. Try to gradually raise the mold temperature and barrel temperature. Weld-line is a weak area. 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. With Ixef® PARA compounds, the strength of a weld line is typically 90 MPa (13,000 psi). A weld line can also be called a knit line. In the end, the total amount of time that running a complete Taguchi DOE (L18) to occupy an injection. Gambar 2. In an injection molding process, a weld-line forms when two flow fronts meet each other. When this fails to happen correctly, a weld line defect occurs. Flash. 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. In the 1947 book, Injection Molding of Plastics, the late Dr. Install an ultrared light inside the hopper. Equipment. Injection molding is nothing without molds. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. Remember, by avoiding weld lines, you can lessen operations cost. It is important to investigate the weld line because the weld line area can. In the injection molding process, weld line regions occur when a molten polymer flow front is first separated and then rejoined. Flow marks in injection molding can be avoided if adequate measures are taken. An injection molding gate is a critical component in mold design, acting as the passage through which molten plastic travels from the runners into the mold cavity. Injection moulding (U. Instead, a line that looks like a seam forms. High-density PE was also moulded in the same conditions but in a lower temperature range (145 to 220°C). The main runner and sub-runner are too thin or too long. This study focuses on the analysis of fill time by optimizing the injection molding parameters to reduce the defects that are always found on the plastics part such as poor weld line and part not. Learn how to avoid them and what injection molding companies do to prevent them. 2004; To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. 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. Vertical Plastic Injection Molding Machine [10, 11, 12] 2. The weld line length was selected as part of the quality index to investigate the effects of gate location on weld. Complexities in the design and intricate pathways in the mold can also create flash in injection molded parts. Star Rapid offers tips and tricks to improve your prototypes and production parts. This can allow the. Weld lines are a kind of Achilles heel of plastics. One of the things that can compromise an injection molded part is a weld line, also called a knit 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. The need to minimize fiber breakage, plus the higher viscosity of materials with. These master batches and PP pellets were dry-blended by adjusting the ratio such that the fiber contents were 10, 20, and 30 wt%. Three terms that often get mixed up in the plastic injection molding industry are weld, meld, and knit lines. That helps. Physics. Injection speed is too low. Polymers 2023, 15, 2440 3 of 21. Weld line section presents notch or gloss difference. Designers can easily set up and perform analysis with only a few clicks. Weld line formation in the injection molding process occurs. The gate location should enable the two flow fronts to merge easily and continue to flow beyond the weld line. 6. Alloys. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. The following are the reasons. Weld line strength is influenced by the temperature at which the weld line is formed and the pressure exerted on the weld until the part freezes, (pressure is 0 at the weld line). Polyamide 6 (Lanxess, Durethan B 30 S 000000, non-reinforced, ISO 1874-PA 6, GR, 14-030, Cologne, Germany) was used for this experiment. (3) Adjust the temperature of the barrel and nozzle: the viscosity. Many works deal with weld lines and their dependence on processing parameters for conventional injection molding, but only a few works focus on the weld line in µIM. poor flow fronts that are too cold, this can also lead to a deterioration in the mechanical properties. Zhao, X. 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. Plastics manufactured by injection molding are meant to be durable and reliable, able to hold up to heavy use, high temperatures, or adverse conditions. The injection molding process can be optimized to maximize weld line strength by increasing. In some cases, a weld line can also cause a loss of strength and impact resistance. A visual mold with variotherm system for weld line study in micro injection molding. 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. Unfortunately, the 3D layering process creates ‘weld lines’ (an injection molding term) between layers which is essentially two layers of polymer that meet. + Optimize holding pressure time. This may require higher melt temperature or lower injection speed . Change the gate locations. Weld line Weld line dikatakan ketika dua atau lebih aliran lelehan depan. This failure causes the product to be damaged during use. The definition of weld lines: When multiple plastic flow fronts meet in the cavity after encountering inserts, holes, or areas with inconsistent flow rates or interrupted melt flows, or in the case of gate injection filling, the inability of two or more flow fronts to fully “knit” together will cause the linear weld marks. Article Google Scholar Deng YM, Zheng D, Lu XJ (2008) Injection moulding optimization of multi-class design variables using a PSO algorithm. A tensile test specimen mold, which allows cavity thickness varying from 2. 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]. This can occur when a polymer flow splits to go around an interruption (e. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. Ada berbagai penyebab mengapa weld line bisa muncul pada permukaan produk plastik. Int J Adv Manuf Technol 52:131–141. 666 Azieatul Azrin Dzulkipli and M. 5. 1. Poor weld line Ⅰ. Optimization of Injection Molding Process to Minimize Weld-line and Sink. Bin-Xin Yang Ouyang Jie Supei Zheng Qiang Li Wen Zhou. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. Kondisi ini juga bisa menandakan bahwa mesin injection. 4. 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. Neat polypropylene retains nearly 90% of its strength on a properly designed and molded weld line. Install an ultrared light inside the hopper. Int J Adv Manuf Technol:1–11In addition to the weld line, the exposure of fibers on the molded product surface results in a rough surface, which degrades the appearance of the product. Description Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. Mechanical properties of the weld line defect in micro injection molding for various nano filled polypropylene composites. 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. In injection molding weld lines are formed whenever two flow fronts are joined. Plast. They decrease the. If weld lines are unavoidable due to multiple gates in a moulding, they should be positioned in the non-critical region. 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. 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. Minimize the use of release agent. Weld lines occur when melt flow fronts meet during the injection molding of plastic parts. 2021年4月23日 / by admin. Machine Shot Capacity – The maximum volume of resin that can be injected in a single stroke of the injection machine. Figure 1 below shows the development of a weld line. CrossRef View in Scopus Google Scholar [17] G. (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. If the injection molding speed is too slow, however, there may be an insufficient filling of the mold. To prevent weld lines, increase the pressure and temperature. Because of the ever-increasing requirements for parts performance, lots of researchers have perf. Figure 2. Crack growth behavior. Nguyen-Chung. th INTRODUCTION Injection molding is one of the most Weld lines are a common defect generated in injection molding, which apparently affects the performance of final products, but the available reports on carbon fiber-reinforced thermoplastics are still rather few. In the present work, the micro specimens were investigated. Meld and knit lines are actually both different types of weld lines. 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. Try to gradually raise the mold temperature and barrel temperature. Weld line is one of the plastic injection molding defects. Information about PA6/PA66 (Nylon) Injection Molding. Micro injection molded polymeric parts coated with functional thin films/layers show off the promising applications in microsystems area. 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. As the injection process continues, the two separated melt fronts meet again along the longitudinal section of the plate forming a weld line. weld lines in infill analysis of injection molding simulation was observed [5]. of micro injection molding process simulation by technology update and progress. Adjust the design for the flow pattern to be a single source flow. Munich, Germany: Carl Hanser Verlag, 1994. Procedia Mater Sci 2014; 3: 2048–2053. In the heating step, the heatingOverview of the injection molding process. These lines can weaken the strength of the part, and they can also be unsightly. The Factors that Cause Weld Line in Injection molding Pressure. Flow lines are off-color lines, streaks, and other patterns that appear on the surface of a part. Weld line existence reduces the material strength; however, its demerit characteristics. This month, in our FREE SimTech™ series of webinars, we will explore weld lines and how they develop. Usually it’s a straight line, and often to be found radiating away from a hole, inclusion or other such part feature. Although they often cannot be avoided it’s possible to minimize their cosmetic effects to an acceptable degree through careful product design and. Short Shot Short Shot adalah suatu kondisi dimana, plastik leleh yang akan diinjeksikan kedalam cavity tidak mencapai kapasitas yang ideal atau sesuai settingan mesin. Increase the injection speed. 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. 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]. 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. 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. 2. 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 simulation of mold filling with multi-inlets or an insert in the cavity is pursued with an improved Level Set Method. Weld-line is a weak area which reduces the strength of the part locally. Its design significantly impacts the final product’s appearance, strength, and functionality, making it crucial for manufacturers to understand its intricacies and variations thoroughly. The weld line is an inevitable defect in the most injection molded components. Weld lines represent the region where two separated melt fronts recombine. In order to study the weld line developing process and its influence on mechanical properties in micro injection molding, a visual mold with variotherm system mold was designed and fabricated. A flat product case was considered as an example of a typical aircraft structural element. 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. 1. The main types of injection molding defects are: 1. Our injection molding company is explaining what these imperfections are, why they can compromise. Avient’s Zachary Alderman shares practical tips on designing and injection molding parts utilizing short-fiber reinforcements. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. ”. Weld lines often generate mechanically weak areas, because of the unfavorable perpendicular orientation of the macromolecules, fibers and/or other fillers to the direction of the main flow. Plastic injection molding is a versatile and efficient way to produce durable, detailed parts of endless sizes, shapes, and purposes. The default weld line result recognizes 135º as the maximum angle of collision and as that angle decreases, the severity increases as it. In this paper, a weld line factor (W-L factor) was adopted to. Controlling the mold’s temperature could also minimize the weld line’s effects. Introduction. Figure 1a illustrates how the weld line is produced when two melt streams merge during the final filling process. 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. Injection Molding Glossary; Weld Lines; Weld Lines. [23, 24]. Simulation of polymer molding filling process with an adaptive weld line capturing algorithm. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. <Mold> Increase (or decrease) the size of the runners and gates. Vibration assisted injection molding. Materials Science. The welding angle can be used to differentiate weld lines and meld lines. A meld line is defined as the re-merging of two flow fronts. During injection. 3. 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. They can affect the strength and. Some of the approaches include the application of machine learning methods (Chen 2008; Manjunath and Krishna 2012; Kuo et al. 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. Insufficient plasticizing ability of injection molding machine. Article Google Scholar Deng YM, Zheng D, Lu XJ (2008) Injection moulding optimization of multi-class design variables using a PSO algorithm. The weld line in injection molding is created when two melt streams connect, as shown in Figure 1. 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. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. One common issue that frequently arises during injection molding is the formation of weld lines. The following guidelines have. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. This is a video excerpt from our Problems & Solutions Course - Weldlines. Injection molding plate for mode I testing geometry. The line where two resin flows “knit” or “weld” together during injection molding is called a weld or knit line. Fig 13:- Detailed view of weld lines. <1> As illustrated in Figure 4, the existence of. Meld and knit lines are actually both different types of weld lines. This reduced thickness of the frozen skin further enhances the visual appeal of the. In this regard, the plasticizing ability of the plastic injection moulding machine should be checked. We'll show you how. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. Injection molding is a complex multi-variable, nonlinear and time-varying unsteady process, which makes it more difficult to optimize the process parameters. A new kind of weld line was. 943 µm to 0. สาเหตุรองของการเกิดปัญหาการเกิดประกายเงิน (silver streak) 1. 2(a, b). This is expected to achieve maximum results while the pressure holding effect will also increase. These potential causes include: Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. 1. The type of resin used during injection molding plays a large role in whether or not a knit line will be present. To position weld-line to avoid critical areas for the sake of aesthetics or mechanical strength is the key to the success of bi-injection molding. Weld line existence reduces the material strength; however, its. Ideally, the resin flow will split into two flow fronts to pass around the obstruction and then recombine into a single flow front. Characteristic: Basically, there are PA6 AND PA66(Nylon 6 or Nylon 66), Nylon has tenacious and wearable, self-lubricious and smooth characteristics with non-toxic and antibiosis and high water absorbability. Failure may result due to the assembly torque, or end-use application loads (temperature, creep). 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. Steven. M. In the case of PC, the model predicts satisfactorily the weld-line strength as a function of injection temperature. Weld Line Factors for Thermoplastics. Weld lines are injection molding defects that can be mitigated by a number of tactics that depend on your part design. Flow lines arise when at least two melt fronts meet at an acute an-Weld line is aesthetically unpleasant and affects the mechanical strength of injection molded parts. 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. 2011; 509 (2):226–233. Weld Lines. Kagitci YC, Tarakcioglu N (2015) The effect of weld line on tensile strength in a polymer composite part. The cracking was always located in the weld/knit line and therefore caused by weakness in the bonding of the plastic at. The impact behavior of weld-lines in injection molding. In this lesson we will focus on the meld and weld lines. Sequential valve gate technology. This study focus on the. 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. Known also as knit lines and weld marks, weld lines are difficult to eliminate completely, especially if your injection molded part requires holes. 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. Still, it can be seen to varied degrees depending on mold. An evaluation model based on artificial neural network method. Weld lines are the result of fundamental physical effects taking place inside of the mold tool cavity, they are common imperfection to be found in most plastic injected. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. 010 0. Sink Marks Cause 3: Improper Pack or Hold Pressure. They occur when melt flow fronts collide in a mold cavity. (3-1) Increasing the Resin Temperature at the Weld Line Section. Weld or knit lines result wherever two or more polymer flow fronts unite. Weld lines appear as a result of the flow of molten plastic during the injection molding process. When two or more streams of plastic meet and fuse together, a visible line or weakness is formed on the surface of the finished product. 2) Vents in an injection mold should let the air out, but not the liquid plastic. If it only affects the appearance, it can change the position of the burn four to change the position of the weld line. Computer simulation packages of injection molding have had success in predicting filling behavior in extremely complicated geometries, capable of predicting weld lines’ location exactly. [8,9] It is capable of. Usually it’s a straight line, and often to be found radiating away from a hole, inclusion or other such part feature. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. A meld line occurs when two moving melt fronts converge and flow parallel to each other. Investigations on WLs in micro injection molded parts were performed in Refs. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. Tekanan. This method was adopted. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. To respond to poor plasticization and uneven melt temperature, the molding cycle can be extended to make. Investigate for potential contamination. 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. The microstructure of weld lines is clearly observed from the micrographs. 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. Remedies: Raise the temperature of the mold or molten plastic. gas, which can cause blistering, as well as poor weld lines, warpage and the formation of cold slugs that affect filling and part mechanical properties. Weld lines are formed when two melt fronts come in contact with each other. Alloys. 3. 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. Adjust the design for the flow pattern to be a single source flow. It is important to investigate the weld line because the weld line area can induce potential failure of structural application. Weld lines in injection molding are formed when two or more flow fronts of molten plastic material meet and merge during the molding process. The impact behavior of weld-lines in injection molding. Strength at weld the line location and warpage problem in injection molding plastic component were not new problems in injection molding industries. The problem with ‘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. Polyamide-6 (PA-66) was used as. The Solutions for Poor Welding Lines. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. Expand.