In some cases, a weld line can also cause a loss of strength and impact resistance. 226-233. Lugs size is 65 х 24 х 4 mm. Weld lines are a kind of Achilles heel of plastics. 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. Clamping Unit. In the case of PC, the model predicts satisfactorily the weld-line strength as a function of injection temperature. Meld and knit lines are actually both different types of weld lines. In the heating step, the heatingOverview of the injection molding process. Weld lines can be caused by many reasons, which covers the various aspects of mold, process, raw materials and product design, etc. 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. Weld-line is a weak area which reduces the strength of the part locally. Weld lines occur when melt flow fronts meet during the injection molding of plastic parts. Weld lines in injection molding are a type of cosmetic defect that detracts from a plastic part’s appearance. Weld lines are a kind of Achilles heel of plastics. Investigate for potential contamination. Increase the melting temperature. This paper presents the. Many researchers had emerged with several. 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. Increase the injection speed. This principle has been implemented on a complex component in the case of the spring-loaded cogwheel shown in Figure 5, for instance. 4. 10 in Nguyen-Chung et al. In order to reduce these weak points, a special ram technique for injection molding, which can be integrated into the mold, was investigated. This consequently produces weld lines. When this fails to happen correctly, a weld line defect occurs. As such, optimizing mold designs should always be incorporated in your production model. Wu CH, Liang WJ (2005) Effects of geometry and injection-molding parameters on weld-line strength. 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. Weld line Weld line dikatakan ketika dua atau lebih aliran lelehan depan. Controlling the mold’s temperature could also minimize the weld line’s effects. [ 18 - 21 ] In addition, the effects. This type of injection molding resolves any trouble caused by undesired welding lines. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. Gava and co-workers implemented an investigation devoted to the de-weld lines in injection molded thermoplastic composites. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. This occurs wherever there is a hole, notch, or any other feature on a part which divides the flow of plastic into 2 separate “flow fronts. The weld line in injection molding is created when two melt streams connect, as shown in Figure 1. “I realized weld -line problems are a very common issue for injection molded parts,” Nicholson told Plastics Technology. Description Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. Short Shot Short Shot adalah suatu kondisi dimana, plastik leleh yang akan diinjeksikan kedalam cavity tidak mencapai kapasitas yang ideal atau sesuai settingan mesin. Melt temperature is 250°C, mold temperature is 110°C. The three parameters affecting operation were called injection pressure, injection time, and packing pressure which influence the quality of weld line. 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. One solution is to prevent the weld lines from forming in regions that are. Jiquan Li, Taidong Li, +1 author. The moldability validation and flow analysis tools enable you to iden-tify and correct potential injection molding problems as you design the product. Try to gradually raise the mold temperature and barrel temperature. It occurs when melting plastic material is injected into a mold, it flows through all parts of th. 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. An injection molding gate is the designed opening in a mold through which molten plastic is introduced into the mold cavity, initiating the process of taking the shape of the desired part. 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. 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. Therefore, the length of flowing weld lines must be additionally defined. These master batches and PP pellets were dry-blended by adjusting the ratio such that the fiber contents were 10, 20, and 30 wt%. The line where two resin flows “knit” or “weld” together during injection molding is called a weld or knit line. It is important to investigate the weld line because the weld line area can induce potential failure of structural application. • Move injection locations to make flow fronts meet more obliquely, turning the weld line into a meld line. G. As compared to a weld line, the flow fronts come together at less than 135 degrees. During injection. Weld line defects are a common part defect that occurs when the injected plastic flows around a solid piece of the mold and does not knit back together. Meld and knit lines are actually both different types of weld lines. , 47 (2008. Learn how to avoid them and what injection molding companies do to prevent them. Weld Line Factors for Thermoplastics. Weld lines can be caused by material flowing around holes or inserts in the part, multiple injection gates or variable wall thickness where hesitation or "race tracking" can occur. The gate vestige for injection molding is usually narrow. [ 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. 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. Weld Line defect analysis, the most common of many defects in injection moulding products. 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. However, even with advanced technologies and precise control, the process is not without its challenges. 2. With unchangeable and fixed requirements for the final product, their avoidance often proves difficult. Weld line is one of the plastic injection molding defects. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. Here are some reasons why design is important for injection molding. The injection molding process can be optimized to maximize weld line strength by increasing. 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. In the end, the total amount of time that running a complete Taguchi DOE (L18) to occupy an injection. Weld Lines. The position, length, and angle of weld lines are dependent on the. Its properties make it possible to create thin-walled parts having close tolerances in fast cycles over long. industry, to deliver intuitive injection mold-ing simulations embedded in NX. The impact behavior of weld-lines in injection molding. 1% higher than the ones without ultrasonic assistant, which indicates that the weld line strength in micro injection molding can be well reinforced by the ultrasonic oscillation due to the fact that ultrasonic oscillation induces better diffusion among the melting. Mold flow analysis is widely employed in mold making industry, utilizing data simulation software, the injection molding process can be simulated and presented on the computer,. Redesign the mold to prevent the weld line. 4. These lines can occur at the gate location, where the plastic enters the mold, or anywhere along the flow path. Try to gradually raise the mold temperature and barrel temperature. This article will introduce you the usage, types, and advantages of the Sequence Injection Timer. 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. (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. Mold flow analysis can predict the location of weld lines. In this study, the effects of injection temperature, injection pressure, and fiber cont. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection. 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. . 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. The strength of the weld-line area can be increased by optimizing injection molding process parameters like melt temperature, injection speed, packing pressure, changing gate type and location, etc. Adjust Injection Molding Parameters: Optimizing injection speed, pressure, and temperature can help ensure better melt flow and reduce the likelihood of weld line formation. 2020-01-1306. Although they often cannot be avoided it’s possible to minimize their cosmetic effects to an acceptable degree through careful product design and. • Reduce runner dimensions and maintain the same flow rate. In our DFM report, we will analyze the possible weld lines. 5. Flow analysis of the weld line formation during injection mold filling of thermoplastics. Powder injection molding comprises several processing steps, and defects may occur in each step if care is not taken. 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. Shaofei Jiang. 2. Thoroughly clean molding machine cylinders. J. They. สาเหตุรองของการเกิดปัญหาการเกิดประกายเงิน (silver streak) 1. 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. This weld line can act as a weak spot in the material. In this regard, the plasticizing ability of the plastic injection moulding machine should be checked. In the RHCM, the mold temperature profile plays a crucial. 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]. A simulation process was conducted to determine the recommended setting of injection moulding parameters and the range of the variable. The. 5. Effects of cavity surface temperature on mechanical properties of specimens with and without a weld line in rapid heat cycle. 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]. Stagnant weld lines are formed when melt streams meet head-on. Increase the mold temperature. Weld line additionally called as knit line, is a defect that occurs when the injected plastic meets within a. The effects of fiber concentration has been studied in detail. 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. 3. 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. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. The optimal process condition is very likely to appear in this second part's fine-tune group. This occurs wherever there is a hole, notch, or any other feature on a part which divides the flow of plastic into 2 separate “flow fronts. 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). Wang. Insufficient plasticizing ability of injection molding machine. 2012. Meld lines are formed when two separate flow fronts meets. Fracture Toughness of Weld Lines in Thermoplastic Injection Molding, Polymer Engineering and Science, 33(15): 996-1001. Tekanan yang kurang mampu untuk mendorong aliran dan kembali pada posisi semula dapat menimbulkan weld line. Injection molding weld lines where two or more flow fronts come together in the mold. Sink Marks Cause 1: Incorrect Melt Temperature. Five injection molding process parameters, including mold temperature, melt temperature, packing pressure, injection. Molding Equipment. Increase the injection speed to reduce the amount of cooling happening in the mold. These are caused by the shot of molten plastic moving at different speeds throughout the injection. This defect occurs due to the temperature and pressure not being high enough, causing premature solidification. For glass-filled grades, the thickness at the weld line can be slightly larger than the nominal value due to lower shrinkage associated with vertical fiber orientation at the weld line cross. In this study, epoxy molding compounds (EMC) filled with glass beads were fabricated with a twin-screw-extruder (TSE) and tempered before further processing to generate different degrees of cross-linking (0–15%) in the compounds. ”Weld Lines in a plastic cover. technical ulletin SPECIALTY POLYME RS Design and Production of Injection Molding Tools. Insufficient plasticizing ability of injection molding machine. After that, the compounds were injection-molded into tensile samples with and without weld lines to. Injection molding can be performed with only one of these materials like glass, plastics, etc. 5. Kagitci YC, Tarakcioglu N (2015) The effect of weld line on tensile strength in a polymer composite part. One of the factors that determines the quality of injection molded parts is the weld line [50,75,76]. 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. 2017-01-0481. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. 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. It is possible to pre. It provides scientific basis for designers toWeld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of injection‐molded parts. Since 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. . 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. Plastic Injection Molding Process. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Weld lines are formed when there is an inability of two or more flow fronts to ‘knit’ or ‘weld,’ together during the molding process. The Influence of Knit-lines on the Tensile Properties of Injection Molded Parts, Polymer Engineering and Science, 23(10): 591-596. 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. % glass fibers – PA6 Aramid SV 30-1ETM (figure 1b). 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. 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. 1. 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. Flow Lines. Or, the part where the weld line is produced shall. In a weld line, reinforcement fibers adopt an orthogonal orientation with respect to the filling direction, which results in a significant reduction in the strength and. The weld lines that occur in injection mouldings are critical areas on which depends on the strength of the mouldings. A weld line occurs when two or more molten plastic flows meet and fuse during the injection molding process, resulting in a visible line on the surface of the molded part. Polym Eng Sci 45(7. 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. Expand. What causes them? The primary cause is weak bondage between two or more flow fronts. These lines are formed when two or more flowing molten plastic streams meet and fuse together, creating a visible line on the surface of the molded part. Insufficient plasticizing ability of injection molding machine. Weld line formation in the injection molding process occurs. Figure 1 below shows the development of a weld line. Weld lines are injection molding defects that can be mitigated by a number of tactics that depend on your part design. A weld line can also be called a knit line. A weld line is often unavoidable. Investigations on WLs in micro injection molded parts were performed in Refs. The edge gate is the most popular and straightforward injection mold gate design. Visualization analysis of flow behavior during weld-line formation in injection molding process. 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. 2. As a result this. C. Its appearance can be improved by adjusting parameters. These flow. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. Weld lines have been one of the common defects puzzling the injection molding industry. Weld lines in injection molding are frequently unavoidable. 3. It is a zone with reduced mechanical properties negatively influencing on the molding behavior in exploitation. This thermal field was transferred to an injection molding flow solver to compare simulations and experimental results from the high speed video, both with and without the effect of induction heating. Ideally, the resin flow will split into two flow fronts to pass around the obstruction and then recombine into a single flow front. This happens when the molten plastic is injected into the mold cavity and flows around an obstacle such as a pin, hole, or protrusion, and then comes back together. A meld line occurs when two moving melt fronts converge and flow parallel to each other. 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. They are unavoidable even for moderate complex products. The defects encountered could be caused by mechanical factors, such as poor mold design and mold manufacturing, or by processing related factors, such as incomplete kneading, inadequate molding pressure, injection. Cited by (41) Effect of mould surface roughness adjustments to increase the flow path length in the injection moulding process. 2. Tekanan. In narrow fields, a limited amount of molten liquid can solidify and block the flow. Consequently, it causes viscous dissipation which leads to the generation of heat. Therefore, it is recommended to do a moldflow study prior to the mold being built. They can affect the strength and appearance of the part, depending on the temperature, pressure, speed, and mold design of the injection molding process. As the weld line can significantly lower the mechanical strength of µIM parts, it is relevant to clarify the position of weld. 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. on conventional reciprocating screw injection molding machines using molding practices standard for filled engineering thermoplastics . The gate is the critical bridge between the runners (the channels through which the molten plastic travels) and the actual mold. g. The formation of weld lines and their location along the flow path is a well-studied phenomenon in conventional injection molding; however, only a few papers are devoted to micro-injection molding [11,13,14,15,16]. Silver Streak. 298 µm and the weld line on the heated region was almost eliminated with the aid of induction heating. It is important to investigate the weld line because the weld line area can induce potential failure of structural application. Plast. Micro injection molded polymeric parts coated with functional thin films/layers show off the promising applications in microsystems area. Weld lines, generated during injection molding, can significantly reduce the mechanical performance of structures. In spite of its cosmetic attributes, a bad knit line can significantly. (1983). With Ixef® PARA compounds, the strength of a weld line is typically 90 MPa (13,000 psi). For those who are new to the injection molding industry, may be confused about this product. The thermo-rheological findings were used to investigate the sources of weld line weakness. An evaluation model based on artificial neural network method. [1-2] investigated the weld line zone of injection molded glass-fiber-filled polypropylene (PP) composites. 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. Weld lines have been one of the common defects puzzling the injection molding industry. Strength at weld the line location and warpage problem in injection molding plastic component were not new problems in injection molding industries. Wavy lines are another feature of weld 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. [23, 24]. Here is a look at the differences between them, the causes of meld and knit line imperfections, and their impact on part durability. Injection Molding Glossary; Weld Lines; Weld Lines. 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. 2. Islyn Thomas summarized the need for a particular vent location better than I ever could. This occurs wherever there is a hole, notch, or any other feature on a part which divides the flow of plastic into 2 separate “flow fronts. Three terms that often get mixed up are weld, meld, and knit lines. 0 mm, is designed to conduct the. This study presents an innovative approach to enhancing weld line strength in advanced polymer injection molding through applying gas-assisted mold temperature control, significantly increasing mold temperature beyond typical values observed in conventional processes. 4. Melt temperature does effect the weld. 9 – Over Packing. The second technique, cascade injection moulding, can produce parts free from weld lines. molding Æ Thermoplastics Æ Weld line Æ Simulation Rheol Acta (2004) 43: 240–245 DOI 10. A weld line develops when two or more flow fronts come together but do not meld completely because of partial solidification. 7 in Kobayashi et al. Crack growth behavior. 1. Flow-induced filler orientation and weld lines are un-avoidable facets of the injection molding process. Information about PA6/PA66 (Nylon) Injection Molding. This failure causes the product to be damaged during use. Burn Marks. 1. At a low volumetric injection flow rate of 33. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. This failure causes the product to be damaged during use. 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. The following are the reasons. 030 0. 3 and 53. The 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). 000 0. In the plastic injection molding industry, we work with materials that are byproducts of oil refinement and molds made of metal casting, so our terminology is bound to be at least slightly confusing. C. Double push filling method. You will have to confirm them before tooling. Gate position in injection mold. Weld lines in injection molding are frequently unavoidable. DescriptionThis insertion ensures the separation of the melt flow. As the plastic flows through the mold it. The resulting defects don’t stop at flash only. 666 Azieatul Azrin Dzulkipli and M. ing weld line properties of injection molded thermo-. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. 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. (1998) for clear photographs. First, an injection mold with triangular inserts was built to study the influence of meeting angles on material properties at the weld line. DYNAPLAST Tbk. The utility model relates to a mold structure capable of eliminating the appearance of weld lines of a hole. 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. Machine Shot Capacity – The maximum volume of resin that can be injected in a single stroke of the injection machine. In this study, the effects of injection temperature, injection pressure, and fiber content on the mechanical properties of weld lines were studied for carbon fiber-reinforced nylon. Inadequate back pressure. , a post that forms a hole) and then rejoins, or when polymer melt fronts meet, from multiple injection points. Weld lines appear as a result of the flow of molten plastic during the injection molding process. * Corresponding author, e-mail: [email protected] an injection molding process, a weld-line forms when two flow fronts meet each other. , Ltd. Increase the mold temperature. Weld lines are a common imperfection to be found in most plastic injected molded parts. identi fy a s urface defect i n th e for m of a weld line, which occurs due to the two injection points at x = 5 mm and 34 mm ( see Fig. Injection molding is nothing without molds. The weld line is then created with a higher flow front temperature and is packed with more pressure. Miron MC, Major Z, Adachi T. 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. <1> As illustrated in Figure 4, the existence of. (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. To increase the sustainability of the process, determinative parameters and their effects should be examined. 2002), the use of simulation approaches (Berti and. This injection molding defect appears as a black discoloration on the surface of the molded part. Injection molding is a manufacturing process that involves injecting molten plastic into a mold cavity to create a specific shape or design. In addition a weld line can be moved to an area where it is less visible. Abstract. 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. 2(a, b). These weld lines occur usually around holes or at the material flow joint area in the injeciton molded part, some welding lins is very small, specially if. 2023年1月3日 / by admin. Consequently, weld regions have been observed to have inferior mechanical properties compared to the bulk. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. As a result this weld line will be a weak point in this part. Three terms that often get mixed up in injection molding are weld, meld and knit 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. Injection-molding machine is the Negri Bossi VE210-1700 with screw. une, 13: 15. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. Weld lines can be a weak spot and have therefore to be taken into consideration in part design. 1. The Factors that Cause Weld Line in Injection molding Pressure. Procedia Mater Sci 2014; 3: 2048–2053. From Understanding Weld-line Integrity by Sabic Innovative Plastics, p. 18/06/2021. Star Rapid offers tips and tricks to improve your prototypes and production parts. replication and poor weld line strength . And how to use the 3 modes of the sequential controller correctly to prevent burn marks, weld line, short shot, and other part defects in injection molding. 030 0. 2) Vents in an injection mold should let the air out, but not the liquid plastic. Compd. These are preferred over weld lines as they will normally result in improved cosmetics and structure. A quantitative evaluation of the appearance quality of weld lines in RHCM parts. If there’s too much mold release, you may require a higher pressure to push it through the machine. 1 Prediction of weld lines with injection molding simulation softwareWeld lines in design for manufacture. Mechanical properties of the weld line defect in micro injection molding for various nano filled polypropylene composites. Threadline gap in-between part due to improper gate location in complex design parts including excess of holes (multipoint. 2. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. Technol. For multiple gate and complex part. 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. Boost time too long Shorten boost time, lower boost pressure, or move transfer to an earlier position . injection molding. In. This method was adopted. + Optimize holding pressure time. Weld lines are visually undesirable and a plastic part is structurally weak at weld line positions. Weld-line is a weak area. Increase the injection speed to reduce the amount of cooling happening in the mold. (+86) 760 2222 2556 enquiry@starrapid. 005 0. 2011; 509 (2):226–233. This may require higher melt temperature or lower injection speed . The microstructure of weld lines is clearly observed from the micrographs. For this purpose, the width of the weld line calculated by Sigmasoft is. To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. 2004; To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. That’s the air escaping out of the nozzle until the hose is full of pressurized water. The injection molding gate generates heat by dissipation. If not, the speed will drop, and it could create weld lines. Thus, it is important to understand (i). Our injection molding company is explaining what these imperfections are, why they can compromise. The melt stream is separated at the part’s cutout and reunited at the other end of the cutout. Here are a few of the most common defects that may occur in plastic injection molding — and how product teams can avoid them. Polyamide-6 (PA-66) was used as. A poor knit line can cause only cosmetic blemishes or it can significantly weaken the structural integrity of a part.