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. Jiquan Li, Taidong Li, +1 author. Weld Lines. According to the characteristics. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Polym Eng Sci 45(7. (3-1) Increasing the Resin Temperature at the Weld Line Section. Instead, a line that looks like a seam forms. 6. 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. Weld line section presents notch or gloss difference. The weld line in injection molding is created when two melt streams connect, as shown in Figure 1. It has larger cross-sectional regions that allow sufficient molten plastic flow into the cavity. 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. Injection molding is an efficient manufacturing process for mass-producing parts with complicated geometry. The more gate points there are, the more weld lines will occur. 6. + Optimize holding pressure time. Consultant @ Effinno Technologies, BSME, MBA - Bridge between Plastics Injection Molding Knowledge and Practice. 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. 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. 3. So today we are going to take a look at the five most common defects in injection molding and their solutions. The hair-like weld line is the. Flow-induced filler orientation and weld lines are un-avoidable facets of the injection molding process. A knit line, also called a weld line, occurs when the liquid plastic moves through the mold and hits more melted plastic and they don’t flow or fuse together. 5. A weld line can also be called a knit line. 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 schematic diagram of a weld line formation is illustrated in Figure 7, where is the welding angle of two melt fronts. Problem: Weld lines are formed when plastic resin is forced around an obstruction in a mold tool and reforms on the side opposite the gate. (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. Flow lines are off-color lines, streaks, and other patterns that appear on the surface of a part. Computer simulation packages of injection molding have had success in predicting filling behavior in extremely complicated geometries, capable of predicting weld lines’ location exactly. Poor mold spot Spot mold to ensure fit and vent depths at ~0 . Except for a few injection molded parts with very simple geometry, they occur on most injection molding parts (the shape is usually a line or V-shaped groove), especially Large complex items requiring the use of multi-gate molds and inserts. การแก้ไข ชิ้นงานจุดที่เกิดความอ่อนแอบริเวณ weld line คือต้องใช้ความเร็วในการฉีดต่ำในจุด. 2-1. Weld line. 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. The resulting defects don’t stop at flash only. Sink Marks Cause 1: Incorrect Melt Temperature. (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. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. 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. When the polymer resin is injected into a mold, it flows through all portions of the mold cavity. Fig. Optimizing the injection parameters through combination of adjusting the molding temperature, varying the gate pressure, and increasing the dwell time. As compared to a weld line, the flow fronts come together at less than 135 degrees. Shaofei Jiang. Wang et al. The flow of the material in the injection mould takes place through the gate. Injection molding could be applied with many polymer materials, such as. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. In this study the polycarbonate (PC) and carbon fiber (CF) are used as the experimental materials to investigate the impact of injection molding process parameters on tensile strength of weld line. Weld line formation in the injection molding process occurs when two or more melt flow fronts contact each other immediately after the cooling process. Effects of cavity surface temperature on mechanical properties of specimens with and without a weld line in rapid heat cycle. Injection molding, polypropylene, talc. The three parameters affecting operation were called injection pressure, injection time, and packing pressure which influence the quality of weld line. Weld lines are formed when there is an inability of two or more flow fronts to ‘knit’ or ‘weld,’ together during the molding process. A weld-line is known as a representative defect in the field of plastic injection moulding, and also as a cause of inferior mechanical propensities and poor appearance. Weld lines represent the region where two separated melt fronts recombine. Conventional injection molding is widely used to produce plastic parts, mainly in the automotive industry, due to the high production ratios and quality of. the three-plate mold often adopt this kind of gate. Weld lines can significantly reduce ultimate tensile strength (UTS) and fracture strain of talc filled polypropylene (PP). Vibration assisted injection molding. Wang. Weld lines defects are formed when two flow fronts are merged together. 2) Vents in an injection mold should let the air out, but not the liquid plastic. Steven. Weld-line is a weak area which reduces the strength of the part locally. What is weld lines. 2. The line where two resin flows “knit” or “weld” together during injection molding is called a weld or knit line. These lines can occur due to variations in wall thickness, gate location, or the geometry of the part. 6. Weld lines are formed when two or more flow fronts join, as the liquid polymer fills the. Fig. Fracture Toughness of Weld Lines in Thermoplastic Injection Molding, Polymer Engineering and Science, 33(15): 996-1001. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. Increase the injection speed. [ 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. Weld lines can be caused by many reasons, which covers the various aspects of mold, process, raw materials and product design, etc. Weld lines occur when melt flow fronts meet during the injection molding of plastic parts. (1) Increase the injection pressure and prolong the injection time. Improper fusion of two fluid flows, a state before weld line. 2020-01-1306. 025 mm (0 . 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. 15 it can be found that for the opposite position of melt injection the weld lines forming under higher temperature would produce better plastics. [ 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. 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 5. Weld lines cause significant reject rates and are a common problem that all molders face. Stop using mold parting agents. Mold Design Most conventional mold designs will work with TPU’s. Unless you are manufacturing an extremely simple part with one gate and a unidirectional flow front, your part will have weld lines. Download : Download high-res image (856KB) Download : Download full-size image; Fig. 22: Weld line formation when melt splits around core pins. 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 weld lines that occur in injection mouldings are critical areas on which depends on the strength of the mouldings. Quality concerns in injection-molded materials can vary fr. Redesign the mold to prevent the weld line. Weld lines are a surface defect caused when two or more flow fronts come together during the injection process. 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 specific method is that when the product is just filled and filled in the cavity, the insert. Threadline gap in-between part due to improper gate location in complex design parts including excess of holes (multipoint. The need to minimize fiber breakage, plus the higher viscosity of materials with. 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. consideration in gate location. As a result this weld line will be a weak point in this part. The weld-lines are undesirable from both aesthetic and functional points of view and their effect is different for. During the plastic injection molding process, one of the biggest challenges is. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. An excess mold release is a major cause of weld line due to two variables: high pressure and speed. Redesign the mold to prevent the weld line. The calculation was carried out on a mesh with solid elements obtained in ANSYS Meshing and transferred to Moldex3D by means Rhinoceros. The goal is to create a uniform thickness and at the smallest (thinnest) level required. Park et al. Weld Lines are formed when two or more molten polymer flows meet during the injection molding process. Weld line formation in the injection molding process occurs. With unchangeable and fixed requirements for the final product, their avoidance often proves difficult. the meeting angle by optimizing variation over time in the cavity. Weld lines have been one of the common defects puzzling the injection molding industry. The injection molding gate generates heat by dissipation. During injection. weld lines in injection molded thermoplastic composites. Weld lines not. In this paper, a kind of polypropylene (PP) foam plastic parts with special weld lines were obtained by core-back foam injection molding with chemical blowing agent. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. Gate location should set to avoid weld lines, keep clean of the important position of the products,. 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 lines defects can also form when the flow fronts from two gates merge or when thick and thin sections in a part cause a flow to split and merge. 030 0. 5. If the large molded product is. EasyFill Advanced provides the weld-line temperature distribution and meeting angle prediction. Here’s how to decrease the chances of weld lines: Increase the temperature of the mold or the molten plastic. An excess mold release is a major cause of weld line due to two variables: high pressure and speed. Sink Marks Cause 5: Improper Part Geometry. Injection molding of large/complicated products are usually prepared by multiple compounds, which produces weldlines once the melt fronts are joined by impingement flow. A meld line occurs when two moving melt fronts converge and flow parallel to each other. Weld lines appear on the molded part where molten plastic meets. Weld lines represent the region where two separated melt fronts recombine. A weld line is a mark left on the surface of a plastic injected molded part. 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. 2017-01-0481. 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 results showed that the tensile strength of PE remains unchanged in the presence of weld lines. [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. When an external load is applied to a weld line region, the part’s potential for mechanical failure is increased. Injection Molding Know How. (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. 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. Expand. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. Many studies were conducted to explain the weakness at the. Weld lines typically appear in a part when an obstruction of some kind separates the melt flow and prevents it from "knitting" together. 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. This study describes how the weld line was formed on the part. The type of resin used during injection molding plays a large role in whether or not a knit line will be present. 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. Problem: Weld lines are formed when plastic resin is forced around an obstruction in a mold tool and reforms on the side opposite the gate. 2. A quantitative evaluation of the appearance quality of weld lines in RHCM parts. Flow marks in injection molding are defects that manifest as a line or series of lines forming a pattern different in color from the other parts of the molded material. In spite of its cosmetic attributes, a bad knit line can significantly compromise a part. g. 1 Prediction of weld lines with injection molding simulation softwareReduced frozen skin thickness: High injection speeds also contribute to a thinner frozen skin at the weld line. 015 0. Weld Lines-3 Ways for Detecting and Correcting. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. In this paper, a weld line factor (W-L factor) was adopted to describe the. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. Valve. A new kind of weld line was. As the injection process continues, the two separated melt fronts meet again along the longitudinal section of the plate forming a weld line. In. Sink Marks Cause 4: High Mold Temperature. In injection molding, it is often important to maintain consistent color throughout the part. Move injection locations to make weld lines form closer to the gates. micro injection molded weld line’s mechanical properties. 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. The main types of injection molding defects are: 1. + Adjust injection speed. , 2 (3–4) (1988. Multiple gating, splitting of the melt flow due to inserts in the cavity or through holes, as well as changes of thickness give rise to points within the structure where the flowing fronts will recombine and weld. 6. The main runner and sub-runner are too thin. If the different flow fronts have cooled. In this experiment, several ejector. To elimi- nate weld lines, you can enlarge shrinkage. Abstract. In the injection molding process, weld line regions occur when a molten polymer flow front is first separated and then rejoined. 010 0. when two or more melt flow fronts contact each other immediately after the cooling process. If the injection gate is not properly designed, it can cause the formation of defects like sink-mark, warpage, short shot, weld-line, air traps, and other faults [15]. Therefore, more studies covering this subject are required in order to improve the insight regarding the mechanism involved in the formation of weld lines in extrusion and,From the so-produced materials, specimens with weld lines were produced according to the first test series, but varying the injection molding parameters only twice, between the best and worst settings found in the previous study with the polypropylene types with MFR 8 g/10 min, i. This failure causes the product to be damaged during use. In this paper, two different injection molding tests were completed. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. Weld lines are a reality in the injection moulding of complex parts. The utility model relates to a mold structure capable of eliminating the appearance of weld lines of a hole-shaped injection molded product. When this fails to happen correctly, a weld line defect occurs. View 08 DEFECTS & REMEDIES (61). 5. This is where the melt fronts divided by an insert, such as a pin or a. Weld line injection molding troubleshooting. After that, the compounds were injection-molded into tensile samples with and without weld lines to. Injection molds: (a) mold type A, (b) fixed plate of the mold type B, and (c) moving plate of mold type B The second mold (mo ld type B) was used for the ISO D2 specimen, as shown in Figure 2b,c . They occur when melt flow fronts collide in a mold cavity. Here is a look at the differences between them, the causes of meld and knit line imperfections, and their impact on part durability. Weld line strength is important in blow molding as well as injection molding. Cracks in Corners – When cracks appear in the corners of plastic parts, the cause is too much plastic shrinkage onto the mold core in that corner. Sink MarksWeld lines, also known as knit lines, are a common defect in injection molding where two or more flow fronts of molten plastic meet but don’t properly fuse together. In the above diagram, the converging flow fronts (indicated by red arrows. 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. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. Weld Line Factors for Thermoplastics. 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. 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. Int J Adv Manuf Technol 52:131–141. , 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. Wu CY, Ku CC, Pai HY (2011) Injection molding optimization with weld line design constraint using distributed multi-population genetic algorithm. They are unavoidable even for moderate complex products. That helps. Weld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of injection‐molded parts. 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. Nguyen-Chung. The following are the conclusion drawn from the present research: 1. Weld lines in injection molding are frequently unavoidable. It is possible to pre. , less than 0. 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. See moreEquipment. . The Factors that Cause Weld Line in Injection molding Pressure. A weld or meld line on plastic parts can cause structural problems and/or be visibly unacceptable. 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]. Failure may result due to the assembly torque, or end-use application loads (temperature, creep). 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. Raising the mold temperature will keep the material molten longer, resulting in stronger weld lines and even elimination of weld lines. Injection molding plate for mode I testing geometry. Weld line, 5. 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 Mold In order to study the formation of weld lines, the mold cavities has been. The welding angle can be used to differentiate weld lines and meld lines. 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. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. 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. This line does not normally impact the overall shape or dimensions of the item. Typical injection molding processing temperatures of TPU materials are as follows: IM ZONE 60A TO 75A 80A TO 90A 95A TO 75D REAR 315 – 340 °F 345 – 370 °F 375 – 400 °FTo study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. A viscosity curve is developed using calculations of the fill time and plastic pressure at. M. These lines. Reduce the amount of release agents. Adjust the position of the gate and include a venting slot. In the case of PC, the model predicts satisfactorily the weld-line strength as a function of injection temperature. They become more critical when particulate fillers are compounded with the polymer. 080 inches. They are unavoidable even for moderate complex products. 3: Weld Lines. It is important to investigate the weld line because the weld line area can induce potential failure of structural application. 4. + Improve vent inside the mold. Weld-line is a weak area which reduces the strength of the part locally. Too high barrel temperature ( abnormal temperature control, deviation of material performance, and increasing cycle time); 8. (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. 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. 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. Weld lines in injection molding are a type of cosmetic defect that detracts from a plastic part’s appearance. 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. 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. Design. The hair-like weld line is the result of weak. Cracking and/or Crazing can be defined as a fracture or surface breakage in the material of a molded part, usually found in weld line areas, but also on the surface in general. For example, filled resins and ABS are more likely to. A flat product case was considered as an example of a typical aircraft structural element. They are the result of fundamental physical effects taking place inside of the mold tool cavity. Effects of mold temperature and pressure on shrinkage 0. Simulation of polymer molding filling process with an adaptive weld line capturing algorithm. Streaks 3. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. Prediction of the weld lines in injection molding process using neural networks. This occurs mainly in the presence of barriers that divide the melt flow in. [ 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. 025 100 120 140 160 180 200 220 240 Mold Temperature (F) LDPE PPAccording to the weld line distribution map of six gate schemes shown in . Weld lines appear on the surface of a molded part where the molten material converges after splitting off into two or more directions in a mold. Weld lines 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. Weld line formation in the injection molding process occurs. They decrease the. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection molding processing. In the sense that the weld line is better formed before the resin. My polymer material selection courses 👉 Find Out About Plastics Blog👉 ht. 1. According to the studies, the most important factor to reduce weld lines is increasing the mold temperature. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. If you are familiar with any form of scientific injection molding, regardless of the name, then you know one of the first steps is performing a viscosity curve study. This paper presents the. The next type of injection molding defect is ‘Weld Lines’. Criens, R. 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. This occurs either due to injection through multiple gates or as a conse-รอยประสานของเนื้อพลาสติก Weld line ตอนที่1. (1983). The most common method for the weld-line characterization is mechanical testing by means of a tensile or bend stage [6,7]. Flow front tracing simulation results for weld line developing process in micro injection molding with Comsol ® Multiphysics 3. Specifically, injection-mold lines are often associated with poor mechanical strength. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. Definition: A seam that appears where two areas of molten plastics meet. 15 shows the frozen layer and weld lines at the end of mold filling. In some cases, a weld line can also cause a loss of strength and impact resistance. These lines occur when two or more flow fronts meet and fuse together, resulting in a visible seam on the molded part. 7 of the reference. Edge Gates. 004 m, a characteristic velocity ν 0 =0. Weld line formations can be weak if they fall in areas that will bear stress or impact. Therefore, the. Use a less viscous plastic. Gates should be designed larger than normal and located to minimize weld line formation. Weld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of 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. In this work, the residual strength of a fiber-reinforced injection molded part containing a hot weld line—or meld line—was evaluated. 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. 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. 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. wall thickness, gate and runner designs and re-validate the result. In injection molding, a V-notch-shaped weld line [1] is generated in the melt front meeting area. Its properties make it possible to create thin-walled parts having close tolerances in fast cycles over long. 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 is a video excerpt from our Problems & Solutions Course - Weldlines. Voids and bubbles, 6. 020 0. Here are some strategies. Remedies: Raise the temperature of the mold or molten plastic. The. (1) Increase the injection pressure and prolong the injection time. In an injection molding process, a weld-line forms when two flow fronts meet each other. ). 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. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. Vents in the mold allow the mold to fill. Weld line existence reduces the material strength; however, its demerit characteristics. As a result, the portion has a faint, perhaps undetectable line. An evaluation model based on artificial neural network method. Increase the injection speed. 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. By the reflection method and a high speed camera, the visual system can be used to record and observe the forming process of micro weld lines during the. Alter the mold design. For multiple gate and complex part, molding weld-lines are unavoidable, therefore mechanical behavior of the weld-line needs to be predicted. 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. It occurs when melting plastic material is injected into a mold, it flows through all parts of th. In this study, polypropylene (PP) was compounded respectively with carbon nano fibers (CNFs) and TiO 2 nano particles at various weight fractions (10, 20, 30, 35. Weld lines appear as a result of the flow of molten plastic during the injection molding process. 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. * Corresponding author, e-mail: fengsjpc@ku. Weld lines are a kind of Achilles heel of plastics. (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.