Different gate sizes and locations using flow simulation have been detected for defects reduction such as weld lines and air traps, air traps and warpage can be managed by varying process parameters [17]. A knit line is when two flow fronts come together but, rather than merging, it’s like a head-on collision at a 4-way stop. Certain injection molding processes may not be effective for the production of some parts. In terms of viscosity, higher heat equals faster flow and lower heat equals slower flow. Here are some common remedies for flow lines in injection-molded products: Increase the injection speed, pressure and material temperature to ensure the material fills the mold before cooling. Flow marks are a phenomenon in which a pattern of the flow tracks of the molten plastic remains on the surface of the molded product. Optimize the runner system and locate gates near the thin walls. The location of the crack can tell us a lot about its specific cause. Molds for investment casting are more accurate and have fewer defects, thanks to flow control over wax injection. On the contrary, for the conformal cooling. Give a good distance between mold gates and. Since these materials behave and respond differently, it is crucial. Mold Design. When the gate depth is much smaller than the cavity entrance depth, and the mold filling rate is very high, when the melt flow becomes unstable jet flow, the front jet has solidified and the later flowing melt fills the mold cavity, and the product will be Snake flow lines appear on the surface. Here's a list of the commonest injection moulding defects and how you can avoid them: 1. Reposition gates and runners to allow resin to flow around the obstruction from a different direction. injection molding. It is generally a three phase process comprising filling, packing and cooling phases. In this case the two flow fronts will meet and there will be very little molecular orientation across the weld. Weld line. The edge gate is the most popular and straightforward injection mold gate design. 0010 in. Once you have a cool shell formed the rest of the mold entering absorbs heat from the layer next to the wall. 750 in. FOW Mould is one of the best companies that use injection molding. The most important factors to consider during molding are the mold temperature, melt temperature, and injection pressure and speed. This review process showcases a company’s technical expertise, the capabilities of its design team, and overall quality. 000 0. They can be caused by variations in cooling speeds of the material as it flows through the mold. "Design and Mould Flow Analysis of Injection Mould for Connecting Link," International Journal on Emerging Technologies, vol. 004 m, a characteristic velocity ν 0 =0. Edge Gates. The injection speed has a great impact on the degree of molecular orientation in the component and therefore influences the shrinkage and the development of a joint line. 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. Here’s a rundown of helpful tricks to keep in mind when designing and choosing a material for molded parts with walls: In general, ensuring your design has uniform wall thickness between 0. The recommended minimum production volume for injection molding is 500 units. Injection molding is one of the most significant material processing methods for mass production of plastic products. On-Line Solutions To Injection Molding Problems. Plugged or inadequate vents n Clean plugged or dirty vents, particularly those along the parting line. The splay condition can completely cover a part, or it can appear inconsistently in various areas on the part. Mold makers should also pay attention to sprue, runner, or gate design. Remedies: Raise the temperature of the mold or molten plastic. In other words, the long-chain polymer. After exhaustive research, testing and pilot-scale demonstration, the team developed a breakthrough new technology utilizing low constant injection pressure. This production method is particularly popular when manufacturing in large quantities. Weld lines in injection molding occur when two flow fronts meet and create a visible line on the surface of the molded part. • Optimize the design of the runner system. [22]. Look for signs of stickiness or burning. MMT Chats. Heat Input and Cooling Calculator for Injection Molding. NX Mold Flow Analysis. Results have shown that, although anisotropy is more pronounced in injection moldings, the mean of values for modulus along and at 90° to radial mold flow lines of an optimum modulus cure are the. also utilized the co-injection molding technique to study the flow of polypropylene at the weld line behind an obstacle in injection molding; the weld line can be seen clearly from the Fig. 100 to 0. Melt delivery management has a major impact on final part quality and the ultimate success of the production line. They are also known as flow lines. Flow rates and a fluid are input to the cooling channels,. Mold flow analysis is a software simulation that can show how resin will fill the mold during the injection molding process. 2. The mold settings can run flawlessly until employees consistently open the machine for inspections, interrupt cycle times, or cause temperature. A void occurs during cooling while the part is inside or outside the mold. Weld lines appear as a result of the flow of molten plastic during the injection molding process. Round the corners of the mold where wall thickness increases to help keep flow rate consistent and prevent flow lines. As discussed above, one of the things that contribute to plastic injection molding defects like sink marks and flow lines is the type of injection molding machine used. The materials used in the plastic injection molding process can vary in rigidity and pliability, among other differentiating characteristics. 020 0. 3. G. In this regard, the gate form with less shunt should be used, and the gate position should be selected reasonably. These streaks or patterns can affect a part's aesthetics, value, and. Lenticular, or Silver Dollar type pigments, are thicker than cornflakes, with a narrower particle size distribution. The primary reason is insufficient plastic fluidity. Flow marks: Flow lines Directionally "off tone" wavy lines or patterns Injection speeds too slow (the plastic has cooled down. Heat: Too much heat can have an appearance similar to moisture splay. Symptoms: Flow lines will typically appear as discolored “bands,” or sometimes “wavy. Thus, with an injection pressure of 1800 MPa, the flow length with 80°C is 47 mm and accordingly for. 5. As the name implies, it is usually positioned along the edge of the workpiece, forming a visible mark at the demarcating line. com. By contrast, a slow injection speed will give you a matte finish and a cold mold, such as 50F, will give you a more flexible part. The Fill system analyzes the filling of each cavity by sensing the melt presence at the end of flow with a cavity temperature sensor and compares the fill-time. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright. Manifesting as wavy lines or streaks on the surface of the molding, flow lines generally occur when molten material flows. Learn more. 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. A poorly designed or maintained water-cooling system can have a serious impact on production efficiency and cause many maintenance issues. 2), the plastic enters the mold at a relatively fast rate and forms the skin. Inadequate mold wall thickness leads to uneven cooling and hindered plastic flow, resulting in weld lines. Contact us to learn more about SMARTFLOW flowmeters. On that note, we. However, you can easily prevent such defects by simply adjusting the temperature, flow rate, or other mold parameters. Flow marks, also known as flow lines, are molding defects that can occur in the manufacturing process of injection molding. Incorrect gate positions cause multiple flow fronts that struggle to merge. Flow speed too fast or too slow. to 0. There are two types of weld lines, cold and hot weld line. Heat: Too much heat can have an appearance similar to moisture splay. Weld lines represent the region where two separated melt fronts recombine. These marks remain and are visible in the cooled product. Part Design: One of the important rules in part design is to have flow lengths that will let the plastic be fluid enough not just to flow into the end of fill but also until all the packing of the part is achieved. The wall thicknesses of an injection molded part generally range from 2mm – 4mm (0. 2. Here are some common remedies for flow lines in injection-molded products: Increase the injection speed, pressure and material temperature to ensure the material fills the mold before cooling. Injection Molding of Multimaterial Systems. thick, 0. As the weld line can significantly lower the mechanical strength of µIM parts, it is relevant to clarify the position of weld. Thereby creating localized pressure within the mold. Features such as sharp corners or undercuts can. A significant part of that is the cooling design, where there are many things to consider. 160"). ”Poor venting, along with the diesel effect, can also cause the mold to wear on the mold parting lines, resulting in flash (excess plastic) on the injected part. A. Adjust the sprue bushing length: If the face of the sprue bushing is sealing off on the parting line, adjust the length to ensure that nozzle pressure or thermal expansion does not hold the mold open and allow the plastic to flow out. Tatjana Geminger, Stefan Jarka, in Specialized Injection Molding Techniques, 2016. In a weld line, reinforcement fibers. Weld line. Known as thermolators,. A method of melt flow visualization was used to record the weld line location on the surface of molding prepared at the proper injection conditions (method of "record grooves effect" formation. The co-simulation of mold flow and structure plays an important role in the design of injection molded fiber-reinforced thermoplastic (FRT) parts. In this study, a new specimen design is introduced for the tensile testing of micro parts. Purpose: The examination of melt flow lines in injection moulded parts was the purpose of this research, as well as a new method of flow visualization was applied. Water set-up and design are every bit as important as establishing and recording a repeatable process. To avoid these defects, manufacturers can check molds for the following: Low Mold Temperature: A mold temperature that’s too low will cause the material temperature to drop fast. To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. Although injection molding is considered a fairly well-established manufacturing process, several independent parameters must be properly set to achieve a high quality of the molded parts. A knit line in a plastic injection-molded part is created when two separate plastic flows meet within the mold and "resolidify" along their interface. 2). Wavy lines are another feature of weld lines. Select a plastic that is less prone to shrinkage. Unexpected flow lines, so-called tear drops, occur. Kulkarni) During the fill phase (Fig. In. Higher numbers assure that water flow is adequate, and that turbulent flow is at an acceptable level. When the gate depth is much smaller than the cavity entrance depth, and the mold filling rate is very high, when the melt flow becomes unstable jet flow, the front jet has solidified and the later flowing melt fills the mold cavity, and the product will be Snake flow lines appear on the surface. Surface Delamination. Check that the machine is creating enough clamping force to keep the mold halves together. You might have come across the aforementioned terminology before and did not know what any of the words meant. Flow lines are a defect in injection molding and can be a significant issue for manufacturers. A. 2. Take these steps to avoid knit lines. Troubleshooting Injection Molding Sink Marks. Seven Common Defects and Solutions for PC/ABS injection molding Products,Flow Lines, Pitting,Product Delamination,Stretch Marks. 0010 in. (2) Improving the flow of plastic and facilitating the molding of thin-walled parts. Within more basic plastic part design plans this plane can be a simple, flat surface, but it is often a complex form that. 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. Using cooling simulation to circuit your cooling lines properly. I’ve been noodling that question around in my head for the last three years, since injection machine suppliers like Arburg, Engel, Wittmann Battenfeld and Sumitomo (SHI) Demag started showing up at trade shows with mold-filling displays on their machine controller screens. May 17, 2023. Its popularity is typified by the numerous products produced in this way at the present time. The parting line in injection molding is which one of the following: (a) the lines formed where polymer melt meets after flowing around a core in the mold, (b) the narrow gate sections where the parts are separated from the runner, (c) where the clamping unit is joined to the injection unit in the molding machine, or (d) where the two mold halves come. Allows you to accommodate a variety of part sizes. 3) Poor Preventative Maintenance. Our glossary of terms provides definitions for a wide range of injection molding terms. Raising the temperature of the mold slightly can help to prevent flow lines, as it prevents the molten material from cooling immediately upon impact with the cavity walls. The strong molecular. The main causes for short shots are inappropriate injection pressure and speed. 7 in Kobayashi et al. After four years in development, an injection machine nozzle tip has been commercialized that is said to eliminate problems of stringing and all the compromises. Flow marks can be caused by any or all of the following factors: Slow melt injection speed. Round the corners of the mold where wall thickness increases to help keep flow rate consistent and prevent flow lines. Unless you are manufacturing an extremely simple part with one gate and a unidirectional flow front, your part will have weld lines. thick, 0. After the plastic fills the mold, it cools and solidifies into finished part (s) which can be easily removed when the machine opens up the mold. 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. A method of melt flow visualization was used to record the weld line location on the surface of molding prepared at the proper injection conditions (method of "record grooves effect" formation. Sufficient draft is an important part of any mold design, and quick-turn tooling is no exception. 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. In this guide, we cover evaluation and also the remedy of flow lines in injection molding. Excess Mold Release Poor mold design, including inappropriate mold wall thickness and faulty gate placements, is a common cause of weld line formation in injection molding. 1. Weld lines have been one of the common defects puzzling the injection molding industry. Each needle valve nozzle opens only when the melt front has moved across its gating point. ”. See. For example, filled resins and ABS are more likely to. Inadequate venting may cause short-shots, poor surface appearance, or weak weld-lines. 025 inches per inch, depending on the particular resin, molding conditions, part design, part wall thickness, and direction of flow. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. Optimize the runner system and locate gates near the thin walls. Flow Lines Or Flow Marks. The molding process is the leading cause of defects in injection molding parts. Prior to this late stage in production, however, 3D printing is much more affordable and flexible for products in the early stages of design. In the process of injection molding, the quality of the mold plays a decisive role in the quality of the finished product. Injection moulding (U. Flow marks are caused by a variety of factors in the injection molding making technology, and they happen at the gate. It can help you reduce defects, improve quality, and save costs by simulating how. Meld and knit lines are actually both different types of weld lines. Improper gate design. This. Weld lines are a kind of Achilles heel of plastics. If during the design and development stage,. Neat polypropylene retains nearly 90% of its strength on a properly designed and molded weld line. spelling: injection molding) is a process for producing parts by injecting molten material into a mould, or mold. (All Illustrations: S. 9 – Over Packing. Flow marks won. During the injection molding process, one of the most important requirements of the mold is to deliver melt from the barrel to the cavity. We started the mold with 100% water circulating at 60°F at a flow rate sufficient for turbulence. Impurity. They may also take the form of ring-shaped patterns when staying close to the mold's entry point, which is the plastic injection nozzle. This carbon will hang up in areas and is difficult to remove. This can be achieved by connecting ribs to each other. (1) Increase the injection pressure and prolong the injection time. Polycarbonate is a tough, optically clear or opaque, biocompatible plastic with good thermal resistance. 1, pp. FLOW – A qualitative description of the fluidity of a plastic material during the process of molding. Polycarbonate injection molding is a process that is used to create polycarbonate products at high production volumes and at a low cost per part by injecting melted plastic pellets into a mold. The plant water system is a critical component of an injection molding facility. They follow the flow of the molten resin from the gate along the finished part. The article has been structured just for you to gain an understanding of the same so that when you plan to buy plastic injection molding, you do understand what it means to do so. 3,000 ton machines can cost $700,000. The following are the main elements of a gating system designed for injection molding. That’s an easy calculation to perform. One of the things that can compromise an injection molded part is a weld line, also called a knit line. This is achieved by using the needle valve nozzles to control mould filling so that only one flow front exists at a time. On thicker sections of the mold, there may be sinks caused by bosses designed into the backside of the surface. , 1 IN, 1 OUT, 2 IN, 2 OUT). In this guide, we cover evaluation and also the remedy of flow lines in. The wavy lines or patterns that form on the surface of the molded object are what we refer to as flow marks. Increase the injection speed. Once the mold is created and the machine is set up, additional parts can be manufactured very fast and at a very low cost. For runny, non-viscous, crystalline resins such as nylon, PE, or PP, the recommended vent depth can range from 0. This “inside-out” flow of the plastic mimics the flow in a water fountain, therefore it is called fountain flow. This continues until the weld lines in plastic injection molding disappear. Short Shots. Injection moulding can be performed with a host of materials mainly including metals (for which the process is called die-casting ), glasses, elastomers, confections, and most commonly thermoplastic and. Thickness – Make the ribs 50% to 60% (0. If the cornflake pigment contains a large amount of fine particles, this will result in a higher definition of flow and weld lines. They are typically the same color as the part but are a different tone. This article continues our series of troubleshooting reports from one of the leading on-the-spot problem solvers in the molding industry. Fig. Molds gain streaks through molten plastic cooling and solidifying at different rates. A special mold provided with a glass window was used in order to directly evaluate the flow progression during the filling phase of the injection molding process in a thin-wall cavity and to. They are evidence of nonuniformity in flow pattern upon entry into the mold. They usually are a slightly different color than the rest of the piece, and typically occur on more narrow sections of the molded item. Prevent Flow and Knit Lines Through Mold Adjustments. Flow Lines particles, during injection molding, will produce visible flow and weld lines. Kulkarni) During the fill phase (Fig. When creating the parting line, the mold design is the first place to look for the appropriate parting line for an injection molded product. The. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. Burn Marks. Understanding the complexities of injection molding flow and solidification is a bit more challenging as. S. Flow Line. Injection molding (or injection moulding) is a widely used manufacturing process in many different industries such as aerospace, automotive, medical, and even. vent the ejector pins and vent the lifters and the parting lines. Thickness –Make the bottom of the boss 60% (0. Flow lines were created during injection moulding process. Use high-quality, temperature-controlled materials for better mold filling. So much. Water cooling pumps coolant through lines on the outside of the mold cavity. Below are ways through which you can remove and prevent flow lines; a. This results in an incomplete part at the end of injection molding. Leadtime Leader 2024. 4) Extended Shutdowns. Impurities in the resin will prevent a smooth flow through the mold. It explored the use of. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. Plastic Injection Molding Process. When a poor-quality plastic that has impurities in it is used for injection molding, it is less likely to flow smoothly through the mold. [1]#TROUBLESHOOTING #FLOWLINES #INJECTIONMOLDINGStudy more about troubleshooting flow lines : lines occur when two flow fronts meet and fuse together in the injection molding process. They commonly occur when there is a large variation between cooling speeds of sections of the material as it flows through the mold. Minimum turbulent flow would be 12-14 GPM, while numbers in the 20’s would be identified as an excellent flow rate. Flow lines. Because you have control over exactly when and how much material enters the tool, you have tighter control of the parameters that go into making a quality part. Flow Rate. It is a type of distortion caused by this premature solidification. Learn how to determine it, and the role of SPI Mold Classes. (1998) for clear photographs. These flow fronts occur when the molten plastic material encounters obstacles, such as inserts, ribs, or other features within the mold cavity. Impurity. g. . They appear as visible lines or streaks on the surface of the molded part and can negatively impact its aesthetics and mechanical properties. also utilized the co-injection molding technique to study the flow of polypropylene at the weld line behind an obstacle in injection molding; the weld line can be seen clearly from the Fig. 3 the path lines of selected material elements can be observed which are. That’s an easy calculation to perform. Definition: Off-tone streaks, patterns or lines that appear on parts. When combined with low injection pressure, this problem leads to decreasing melt speeds and can cause flow lines. The thermo-rheological findings were used to investigate the sources of weld line weakness. Basic Repairs for Warping. The weld line is then created with a higher flow front temperature and is packed with more pressure. The weld lines are formed when there is an obstacle in the cavity of the injection mold. [12] or the flow lines shown in Ref. Weld lines are formed when there is an inability of two or more flow fronts to ‘knit’ or ‘weld,’ together during the molding process. From a technical point of view, valve gate technology enables the production of low-stress injection molding parts, which almost always meet the requirements of a very low vestige. 6. 7 of the reference. PROBLEM: FLASH ON PARTING LINE There are a few key reasons why flash appears on the parting line of a part. This can be caused by a poor mold design, or plastic temperatures, mold temperatures, injection speeds, or. Thick sections take longer to cool than thin ones. 030 0. According to the design requirements of the back shell of mobile phone and the performance of materials, ABS is selected as the raw material for injection molding in consideration of economy [ 8 ]. 060 and 0. Impurities in the resin will prevent a smooth flow through the mold. Flow Lines. This may involve adjusting the temperature and pressure of the mold, using different mold materials, or adjusting the injection speed or cycle time. For injection molding grades, the MFR (MI) values for polyethylenes are generally determined at 190°C (374°F) using a static load of 2,160 g. Flow lines, also referred to as flow marks or weld lines, are visible lines or patterns on the surface of a plastic component. The last cause of flow lines may be the operators running your daily operations. 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. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. 5mm (0. Mold Flow - Position ribs such that the plastic has an optimal flow path. This slight depression is a tiny line called the weld line or knit line. Adjustments to injection speeds are the best way to determine which of these two are the specific cause. Cracking is commonly seen at the weld line area but sometimes on the entire surface. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. Injection molding gates occur in different forms, taking distinct sizes and shapes – appearing narrow, wide, tapered, etc. There are several factors that can contribute to the formation of weld lines, including: Part design: The design of the part can impact the flow of the material and the likelihood of weld lines forming. We will now look at the problem you are likely to encounter and how to fix them. For instance, the plastic used for gears must be completely smooth. The Analysis and countermeasures of flow lines in injection molded products Read more. Plastic Defect # 2: Flow Lines. Reduce the temperature of the mold and plastic being injected. This can be accomplished by reducing the substance’s viscosity. Some of these factors could be the flow rate, the pressure, or the temperature settings of plastic injection molding. The Table 2 categorically reports Melt Temperature, Injection Pressure and Injection Speed are the main contributors in the defects such as the short-shot, weld-lines, flow marks, burn-marks etc. 7. In injection molding, it is often important to maintain consistent color throughout the part. A knit line may be unnoticeable or may look like a crack. Also called “Weld Line. Help prevent warping with these measures: Raise the mold or material cylinder temperature. These defects include the following: 1. There are several factors that can contribute to the formation of weld lines, including: Part design: The design of the part can impact the flow of the material and the likelihood of weld lines forming. This action could indicate that one portion of the plastic flow will move more quickly than the other. Timing and temperature are significant contributing factors when it comes to flow and knit line defects. 1. Sink Marks. 015 0. Locally black discolorations of the molded part occur in the area of the weld lines, at the end of the flow path or of individual areas of the molded part (for example, a rib). Increasing pack or hold pressure helps to eliminate low-pressure conditions at the weld line. 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), the plastic enters the mold at a relatively fast rate and forms the skin. Mold flow analysis is a software-enabled process that. Bob Hatch is manager of technical service and customer support for Prime Alliance, the Des Moines-based resin distributor. They are best described as "off tone" wavy lines/streaks or patterns in the molded part around the injection ports. Molds separate into two sides at a parting line, the A side , and the B side , to permit the part to be extracted. Most flow lines don’t impact the functio…Flow lines are a defect in injection molding and can be a significant issue for manufacturers. 3. The process involves the injection of heated, liquefied plastic into a temperature-controlled mold under high pressure. Weld lines may appear like seams or scratches, but that is not what they are. On average, larger injection molding machinery can cost from $50,000-$200,000 or more. The flow line is usually connected to injection specifications, mold and injection material, it can be defined as linear grooving, or round surges, on the surface of an injection molded part that shows the instructions of product flow within the cavity of the mold. SMARTFLOW ® flowmeters effectively and accurately measure flow rate. These streaks or patterns can affect a part's aesthetics, value, and overall quality. Flow Lines: Flow lines on thinner areas of molded components appear as a wavy pattern, often a different color than the surrounding area. Cascade Moulding Avoids Weld Lines. Conventional injection molding is widely used to produce plastic parts, mainly in the automotive industry, due to the high production ratios and quality of injection parts. Lower speeds allow gas more time to escape through vents. They are the result of fundamental physical effects taking place inside of the mold. These flow fronts occur when the molten plastic material encounters obstacles, such as inserts, ribs, or other features within the mold cavity. At some point in time, it can no. Weld lines have been one of the common defects puzzling the injection molding industry. Features such as sharp corners or undercuts can. It has larger cross-sectional regions that allow sufficient molten plastic flow into the cavity. This means that the skin of the part is always formed by. 7 of the reference. More about the knit lines in injection molding. Basic Repairs for Warping. But add 30% glass and weld-line strength retention drops to only 34% as high as the compound with no. He is currently a tooling manager for a large, multi. Fast injection gives you a glossy part, which is what we wanted in this. The mold flow model is usually a single-part model, that is, the FRT part itself, but the mechanics model is often a multi-part model, an assembly of the FRT part and others. Causes: The issue might be varying flow rates as the molten plastic moves through the mold or changes in the thickness of the mold’s walls. The best method of venting this type of part (Fig. Do not keep the hopper full; hand-feed if necessary. For the measurement of the crystallinity a DSC analysis was performed. Conventional injection molding is widely used to produce plastic parts, mainly in the automotive industry, due to the high production ratios and quality of injection parts. When designing a new injection mold, a moldmaker’s main goal should be to put its client in the best position to make quality parts consistently and efficiently. The Reynolds number takes into account the pressure, volume and viscosity of the coolant, the resistance to flow, length and diameter of the channels and the pressure loss in the cir-cuit. When molten plastic moves through an injection mold at different speeds, the resin solidifies at different rates, which causes this type of defect. Picture the flow of a liquid resin filled with, for example, glass fiber. Here are some ways to avoid. In the injection molding process of plastic parts, flow mark is a common defect due to the defects of parts design and injection molding process [4]. The accompanying table lists the flow rates for various barrel diameters at various injection velocities. with a characteristic length χ 0 =0. The speed of an injection moldingRepeat the two previous steps two or three times, starving the screw periodically to allow the screw to rotate without building a shot. Shear; There are two causes of splay brought on by shear. Reduce the injection pressure to prevent overpacking at the gate. Warping. Low-quality and poorly designed molds can also result in flow lines on injection molded parts, particularly those with uneven wall thickness, insufficient lubrication, and poor venting. Add more cooling circuits. They appear as waves or lines, usually of a different color tone from the surrounding area. In this study, a fully automated. If larger gates are used, expect a longer molding cycle time. Pushing the air out or not is the difference between a good part or burns and flow lines.