Weld Lines. Voids . 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. It has larger cross-sectional regions that allow sufficient molten plastic flow into the cavity. Flow lines can be minimized in injection molding by optimizing the design of the part and the mold, as well as the processing conditions. Tip #6: Pick Which Molding Defects Are Acceptable. You can avoid having any weld lines with cascade injection moulding. 5. Polymer Injection Molding: Gas-assisted Molding. 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 are some of the most common scenarios for cracks in injection molded parts: Cracks in the Direction of Flow – If the crack develops in the direction of the plastic’s flow into the mold cavity, the cause is molecular orientation. Here are the top 5 injection molding defects that can occur, and how to solve them: Flow / Weld Lines. 0005 in. 020 0. They can also appear as ring-shaped bands on the surface of a product near the mold’s “gates. When trying to establish process control in plastic injection, watering the tool is a key variable that is often overlooked. 1. Weld lines have been one of the common defects puzzling the injection molding industry. 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. Melt delivery management has a major impact on final part quality and the ultimate success of the production line. A knit line may be unnoticeable or may look like a crack. 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. Flow Line Phenomenon: Surface defect in which wavy streaks form like a ripple centered around the gate. Flow marks, also known as flow lines, are molding defects that can occur in the manufacturing process of injection molding. From the perspective of the mold, when the molten plastic reaches the gate through a larger-sized runner, the flow resistance of the melt is greatly increased because the gate size is usually very small. Steven. Flow lines are a typical problem for injection molding faults that appear as visible streaks or lines on the surface of the molded part. This means that the skin of the part is always formed by. Adjust Injection Molding Parameters: Optimizing injection speed, pressure, and temperature can help ensure better melt flow and reduce the likelihood of weld line formation. This means that the skin of the part is always formed by. S. Water set-up and design are every bit as important as establishing and recording a repeatable process. Figure 1 below shows the development of a weld line. In injection molding weld lines are formed whenever two flow fronts are joined. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. 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. Mold flow analysis is also used to help designers locate difficult spots to fill within the mold. All of these can slow down the plastic flow, causing it to cool too quickly and lose pressure, both of which are the most likely reasons for weld lines in injection molding. If larger gates are used, expect a longer molding cycle time. Increase the injection speed, pressure, or temperature of the material. Weld lines can be a weak spot and have therefore to be taken into consideration in part design. 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. (All Illustrations: S. Flow lines are a defect in injection molding and can be a significant issue for manufacturers. 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. 030 0. Vents have three components. That’s an easy calculation to perform. One way to reduce the changes in speed of the flow front is to tailor the injection-speed profile. The flexibility of rubber and its durability offers manufacturers and engineers ways to design cushioning components and seals. They are typically the same color as the part but are a different tone. This method can be helpful in. (1) Reduction of injection time and shortening of the molding cycle. The production cost is closely related to productivity. As a result this weld line will be a weak point in this part. Vacuum Voids. 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. Apart from the shape, it is important to design ribs for optimal mold performance. The mold designer cannot know your goals without your input, which is why you will be asked to approve a gate and ejector layout prior to manufacturing a mold. Cracking is commonly seen at the weld line area but sometimes on the entire surface. The Mold. Figure 1 presents the shrinkage of polypropylene versus wall thickness in injection molded parts. Sprues are usually tapered, and they come with ends that are bigger at the top. FIG 1 Depiction of fountain flow. Knit and Meld lines are inherent to plastic injection. spelling: injection molding) is a process for producing parts by injecting molten material into a mould, or mold. In a weld line, reinforcement fibers. Heat Input and Cooling Calculator for Injection Molding. Flow Lines and Flow Marks. Here are some ways to avoid. 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. 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. Investigate the mold for signs that a water leak is present, and correct the condition. Reduce the temperature of the mold and plastic being injected. AnalysisInjection moulding simulation with the finite element method is the most advanced technique for designing injection moulds. c. 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. Molds separate into two sides at a parting line, the A side , and the B side , to permit the part to be extracted. In this study, a new specimen design is introduced for the tensile testing of micro parts. What are Flow Lines in Injection Molding? Flow lines, also known as weld lines or knit lines, are discontinuous lines or streaks that appear on the surface of an. Laminar flow in a plastic mold, described by. In injection molding, it is often important to maintain consistent color throughout the part. 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) properties were measured, and statistical analyses were performed to gain insight on the correlation between melt flow rate and weld-line behavior. Defect categories. Flow speed too fast or too slow. 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. Mold is not vented properly causing slow flow at knit lines. The mold settings can run flawlessly until employees consistently open the machine for inspections, interrupt cycle times, or cause temperature. Also, heating the material in the cylinder. [22]. It is therefore important to work with reliable injection mold makers for quality services and products. Too hot and the plastic will start to degrade, but too low and flow marks increase. For the measurement of the crystallinity a DSC analysis was performed. If it is farther down the flow part, increase injection speed to decrease viscosity and allow more packing pressure. Wavy lines are another feature of weld lines. As the name implies, it is usually positioned along the edge of the workpiece, forming a visible mark at the demarcating line. 008 to 0. Injection molding, in addition to extrusion, is the most important technology in the polymer processing industry. Since these materials behave and respond differently, it is crucial. 020 0. Jetting occurs in a molded component when molten material is injected into the mold cavity and starts solidifying before it fills the cavity. In. Weld lines are a common imperfection to be found in most plastic injected molded parts. This slight depression is a tiny line called the weld line or knit line. Flow Lines particles, during injection molding, will produce visible flow and weld lines. Electronic flowmeters featuring FCI (Flow Characteristic Indicator). In the process of injection molding, the quality of the mold plays a decisive role in the quality of the finished product. These benzene rings also increase the viscosity, reduce shrink rate, and increase strength with the exception of knit and/or meld lines. Flow Lines Or Flow Marks. So much. This most often occurs when you have a core or shutoff feature that the plastic needs to flow around. If performing a resin change from one polymer to another a difference in viscosity can cause flow lines or gels. 7 of the reference. Flow marks, also known as flow lines, are molding defects that occur in the manufacturing process of injection molding. 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. Mold Flow - Position ribs such that the plastic has an optimal flow path. Do not keep the hopper full; hand-feed if necessary. Design for Manufacturing (DFM), also known as pre-mold review, is a collaborative process in the injection mold industry where technical negotiations take place to meet customer requirements. Using a thermoplastic that stays in a. In other words, the long-chain polymer. Weld lines are injection molding defects that can be mitigated by a number of tactics that depend on your part design. Molders should make sure the weld line is formed during the first-stage filling of the part, if possible. Check the diameter of the ejector pins and the pin hole tolerances, if the tolerance is too wide this could allow molten plastic to flow down between the pin and hole surface. Flow Lines. Flow rates and a fluid are input to the cooling channels,. 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]. Chart 1: Diameter versus turbulent flow. 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. Flow lines can occur if any of the following affect the mold: A runner, gate, or sprue that is too small for purpose creates more flow resistance. Inadequate cooling time. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. 3,000 ton machines can cost $700,000. To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. 1 Caused By The Quality of Injection Mold. Lastly, you can only acquire the benefits of parting lines in injection molding during plastic production if you design the parting line correctly. 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. plastic mold venting. Add or increase vents as needed. Complexities in the design and intricate pathways in the mold can also create flash in injection molded parts. Cascade Moulding Avoids Weld Lines. Sufficient draft is an important part of any mold design, and quick-turn tooling is no exception. These streaks or patterns can affect a part's aesthetics, value, and. Learn how to troubleshoot weld lines in injection molding. Injection Molding of Multimaterial Systems. The primary cause of cracking is stress and deformation brought on by the external environment, cold mold surfaces, and low injection rates. 3) Poor Preventative Maintenance. Mold surface is too cold. The 7/16-inch size is a happy medium between many small lines and the fact that larger lines don’t particularly increase the heat exchange benefit. These defects are not visible, like small. Non-uniform cooling of mold causes warping, creating internal stresses within the part and resulting in distortions. Lenticular, or Silver Dollar type pigments, are thicker than cornflakes, with a narrower particle size distribution. or too much shear heat burning the material prior to injection. The proposed method is first applied to the simulation of HDPE melt in a classic Poiseuille flow case, and then two. 1．Mold Temperature Too Low. 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]. 3. Several factors contribute to the formation of flow lines, including material properties, mold design, and process parameters. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. Introduce automation into the injection molding process for improved efficiency. In narrow fields, a limited amount of molten liquid can solidify and block the flow. Defects like this make it harder to market the finished parts to the end user. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. Thin walls often increase the pressure required to fill the part, and. Let’s take a look at some defects that are caused purely due to faults in the injection molding process. FLOW – A qualitative description of the fluidity of a plastic material during the process of molding. 5-3. Investigate the mold for signs that a water leak is present, and correct the condition. They are visible on one side of the parts. 7 in Kobayashi et al. Sink Marks. See. 3. Also called “Weld Line. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright. The flow rate should ensure the material does not lose its. On the other end of the scale, a desktop injection molding machine with 5 tons of force can cost between $30,000-50,000. However, FRTP has problems such as the formation of weld lines, the deterioration of appearance due to the exposure of fibers on the molded product surface, and the deterioration of the strength of. Mold Flow - Position ribs such that the plastic has an optimal flow path. Flow lines. These marks remain and are visible in the cooled product. These streaks or patterns can affect a part's aesthetics, value, and overall quality. Flow lines. Thickness –Make the bottom of the boss 60% (0. Weld‐line is a defect that arises in injection molding when two or more flow fronts collide. flow rate, in turn, causes the heat transfer effi ciency of the cooling cha nnels to vary from one. 080" – 0. The co-simulation of mold flow and structure plays an important role in the design of injection molded fiber-reinforced thermoplastic (FRT) parts. Flow lines are surface irregularities, wavy patterns, or a rippled effect, perhaps of a slightly different color, that can appear in injection molded parts. Novel Nozzle Tip Prevents Stringing, Saving Molds & Cycle Time. Leadtime Leader 2024. Mold fill usually takes 0. 0030 in. Lookalikes include surface scratches, scuffs, flow lines, delamination from contamination, and flaking. If I can answer any questions you may have on optimizing the plastic part design, CNC plastic prototype, mold manufacturing, and injection molding or if I can be of any other help, please feel. 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. Prior to this late stage in production, however, 3D printing is much more affordable and flexible for products in the early stages of design. An improper flow rate and injection speed also cause flow marks. It can help you reduce defects, improve quality, and save costs by simulating how. It can also aid in material selection since fill. Occasionally, the molded part has. The flow rate should ensure the material does not lose its. 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 the surface of the finished parts. This most often occurs when you have a core or shutoff. Flow lines are off-color lines, streaks, and other patterns that appear on the surface of a part. 6. Plastic Purity. Injection molding is a great technology for finished production on a massive scale. Flow lines and flow marks. The cause can vary. • Move injection locations to make flow fronts meet more obliquely, turning the weld line into a meld line. Surface Delamination. The most common and one of the most challenging injection molding defects are weld and knit lines. Neat polypropylene retains nearly 90% of its strength on a properly designed and molded weld line. These defects include the following: 1. The main causes for short shots are inappropriate injection pressure and speed. 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. Flow lines. Injection molding flow lines can also be caused by using material that has defects. The melt holds enough temperature to maintain a low enough viscosity. Venting is required to allow the air in the sprue, runner and cavity to leave the tool as the melt flows into the cavity. On average, larger injection molding machinery can cost from $50,000-$200,000 or more. Known as thermolators,. The wavy lines or patterns that form on the surface of the molded object are what we refer to as flow marks. Flow lines are linear grooving or circular ripples on the surface of an injection molded part that indicate the direction of material flow within the cavity. Weld lines can be a weak spot and have therefore to be taken into consideration in part design. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. Mold Flow Analysis. Industry 4. Using cooling simulation to circuit your cooling lines properly. 2. Rubber injection molding is defined as a process where uncured rubber is transformed into a usable product by injecting raw rubber material into a mold cavity made of metal. The accompanying table lists the flow rates for various barrel diameters at various injection velocities. Thus, as the flow continues, the two flow fronts may gradually rejoin to. In any case, you’d prefer to create polycarbonate parts of different sizes; then this is the best technique that you need to use. The Mold. 5 to 2. The injection speed should remain consistent as the plastic enters the mold, otherwise, it will slow down, cool, and cause flow marks. Within more basic plastic part design plans this plane can be a simple, flat surface, but it is often a complex form that. Flow lines can occur if any of the following affect the mold: A runner, gate, or sprue that is too small for purpose creates more flow. Remedies: Raise the temperature of the mold or molten plastic. The line where two resin flows “knit” or “weld” together during injection molding is called a weld or knit line. Incorrect gate positions cause multiple flow fronts that struggle to merge. Conformal cooling channels (CCCs) are a cooling passageway which follows the profile of the mold cavity or core to perform uniform cooling process effectively in the injection molding process. Mold design is a key aspect of injection molding. If you’re seeing flow lines, try extending the. The difference between a knit and meld line is significant, dramatically impacting the part’s structural integrity. One of the best ways to determine part shrinkage for complex components is with a mold flow analysis. Lower speeds allow gas more time to escape through vents. After discussing the injection molding learning process and the underpinning philosophy in the first two parts of this series, Bill Tobin gets to the heart of the matter—the mold—and shares a few tricks of the trade. Improper gate design. Flow Lines. Plastic is injected into a mold at a specific rate of flow—typically in. One cause of flow lines is low injection speed, which can result in the molten plastic cooling too quickly and creating a. This can be caused by a poor mold design, or plastic temperatures, mold temperatures, injection speeds, or. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. 000 0. Peering into the Flow. Flow marks: Flow lines Directionally "off tone" wavy lines or patterns Injection speeds too slow (the plastic has cooled down. The splay condition can completely cover a part, or it can appear inconsistently in various areas on the part. 6T) as thick as the nominal wall. Injection molding machine . Symptoms: Flow lines will typically appear as discolored “bands,” or sometimes “wavy. However, you can easily prevent such defects by simply adjusting the temperature, flow rate, or other mold parameters. Picture the flow of a liquid resin filled with, for example, glass fiber. Weld lines are usually pointed out as the weak region in molded parts. There are two types of weld lines, cold and hot weld line. 005 0. The following are the main elements of a gating system designed for injection molding. Hamstra: For the OEMs, having a good baseline of what our cooling flow and temperature through a mold is going to give us a good optimization into the next supply chain for the injection molders. These defects include the following: 1. com. The leading edge of the flow, or the melt. As far as the mold builders are concerned, having good flow through each circuit and having a good pressure leak test that they can perform is an. The injection molding process involves the injection of a polymer melt into a mold where the melt cools and solidifies to form a plastic product. These flow fronts occur when the molten plastic material encounters obstacles, such as inserts, ribs, or other features within the mold cavity. On thicker sections of the mold, there may be sinks caused by bosses designed into the backside of the surface. The best we can hope for is to pressurize the knit or meld line better through the combination of melt temperature, mold temperature, flow rates, and holding pressures. 1. During the injection molding process, one of the most important requirements of the mold is to deliver melt from the barrel to the cavity. Causes – Remedies. 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. In this lesson we will focus on the meld and weld lines. Figures 3A, B and C depict different examples of “spot” vents. Weld lines may appear like seams or scratches,. In these cases each circuit might remove a different. Here's a list of the commonest injection moulding defects and how you can avoid them: 1. It also may be that your injection speed is too low, which will cause the molten plastic to solidify at different rates. Polycarbonate is a tough, optically clear or opaque, biocompatible plastic with good thermal resistance. 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. The type of gate for manufacturing often depends on the material used and the parts’ shape. These knit lines are formed as molten plastic in the injection mold flows around an obstruction like a feature. Insufficient injection pressure or time. This results in a much greater amount of vent flow area for the compressed air to exhaust through, and still protects the corners. V. In the area of lettering, ribs, domes or sharp wall thickness changes, air which cannot escape quickly enough is swept along, overrun by the melt and embedded. Flow Lines Defect in Injection Molding Process Flow lines can be defined as linear grooving, or circular ripples, on the surface of a molded part that indicate the. While some molds or inserts have simple, straightforward cooling circuits, many have multiple circuits of various sizes and configurations. 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. However, you can easily prevent such defects by simply adjusting the temperature, flow rate, or other mold parameters. On the surface of a molded object, flow lines (also called flow marks) refer to the phenomenon that linear grooves or circular ripples showing the direction of material flow inside the mold cavity. As a result, the lower degree of stress when gating with valve gate systems becomes relevant. Round the corners of the mold where wall thickness increases: This. Plastic Defect # 2: Flow Lines. PartWeld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. The weld line and the flow pattern of co-injection molding can be seen from Fig. Increasing pack or hold pressure helps to eliminate low-pressure conditions at the weld line. Caused by: Non-uniform cooling times and flow rates; excessively narrow part features. Flow Lines The problem with flow lines is that they. How a mold is watered is key to a processor's goal of consistency. 4 Injection Speed. Parting Lines. tall, and 0. 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. injection molding. Round the corners of the mold where wall thickness increases to help keep flow rate consistent and prevent flow lines. This production method is particularly popular when manufacturing in large quantities. Consequently, it causes viscous dissipation which leads to the generation of heat. Increase injection speeds and pressure to ensure the cavities are filled properly. This action could indicate that one portion of the plastic flow will move more quickly than the other. The barrel temperature is too high. When molten plastic moves through an injection mold at different speeds, the resin solidifies at different rates, which causes this type of defect. 5. Injection molding has been the most popular method for making plastic products due to. [1]#TROUBLESHOOTING #FLOWLINES #INJECTIONMOLDINGStudy more about troubleshooting flow lines : lines occur when two flow fronts meet and fuse together in the injection molding process. thick, 0. Flow Rate. #TROUBLESHOOTING #FLOWLINES #INJECTIONMOLDINGStudy more about troubleshooting flow lines :. In Fig. More viscous amorphous materials, such as PC, TPU or PEEK, can have a recommended vent depth range from 0. Flow lines and weld lines are lines or streaks in the final molded part. Flow lines or marks appear as banded discolouration on the surface. Setting the proper pressure on the injectors to push the plastic into the mold with enough speed that the plastic will coat the mold and fuse with other flow lines. 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. They are caused by improper bonding and low injection pressure and speed [ 46 ]. Utilize advanced injection molding machines with increased injection speed and pressure. Mold Design. Consider the following examples of cooling channel configurations in P20 mold steel with a water line diameter (D) of 11. 5° draft to each side of the rib. Flow Lines. The accompanying table lists the flow rates for various barrel diameters at various injection velocities. 0 seconds, depending on part volume, runnergate style and size, cavity location and injection pressure. As the name implies, it is usually positioned along the edge of the workpiece, forming a visible mark at the demarcating line. When incorporating multiple gates it’s important to consider where the flows will meet as the meeting area can cause aesthetic issues and part weakness. It is generally a three phase process comprising filling, packing and cooling phases. Plastic Injection Molding Defects series-Flow Marks or Flow Lines Aug 23, 2019 What should we keep in mind when designing for injection molding?1. Thus, a right gate design raises polymer temperature to prevent the formation of weld lines and flow marks. Flow marks won. In this example, the flow ratio is 80 (10 Fig 2 – The spiral flow chart provides data about maximum flow length based on several Monday, 01 December 2014 Page 1 of 2Automatic in-line process quality control plays a crucial role to enhance production efficiency in the injection molding industry. 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. Flow lines. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. They commonly occur when there is a large variation between cooling speeds of sections of the material as it flows through the mold. Bob Hatch is manager of technical service and customer support for Prime Alliance, the Des Moines-based resin distributor. 020"). At some point in time, it can no. They also can appear as ring-shaped patterns near the entry points of the mold. Countermeasures to Injection. 3). On the contrary, for the conformal cooling. Cooling lines impact. Molds gain streaks through molten plastic cooling and solidifying at different rates. This software simulation can show how a resin will fill the mold during the injection molding process. In this article, a multiscale simulation method of polymer melt injection molding filling flow is established by combining an improved smoothed particle hydrodynamics method and clustered fixed slip-link model. Figure 7 below shows the cooling channels, defined in this case using simple sketch lines. Plastic is injected into a mold at a specific rate of flow—typically in. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. 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. 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. 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. Water cooling pumps coolant through lines on the outside of the mold cavity. 31″) will require more. 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. Circuit Identification. Possible causes: Low temperature of injected melted plastic or slow injection speed during injection molding resulting in low fluidity of plastic inside the mold. The moldability validation and flow analysis tools enable you to iden-tify and correct potential injection molding problems as you design the product. For optimal cooling, these waterlines are located as close as possible to the surface of the molded part. The Analysis and countermeasures of flow lines in injection molded products Read more. 5mm (0. Flow Linesparticles, during injection molding, will produce visible flow and weld lines. Flow lines or marks appear as banded discolouration on the surface. (1. They are evidence of nonuniformity in flow pattern upon entry into the mold. Flow lines are. Flow lines are aesthetic defects that occur on plastic products. Sprue: This is what feeds the molten material into the runner that in tune reaches the casting by passing through the gates. (3) Adjust the temperature of the barrel and nozzle: the viscosity. Reducing injection speed will allow more time for the air to escape from the cavity through the vents, but this leads to other problems, such as short shots (incomplete parts). Plastics manufactured by injection molding are meant to be durable and reliable, able to hold up to heavy use, high temperatures, or adverse conditions. In some areas, the option is evident, while in others, it. Weld lines can compromise the strength and aesthetics of the part, so it’s important to carefully design the mold and. The thermo-rheological findings were used to investigate the sources of weld line weakness. Polycarbonate Injection molding defects. A. Shear; There are two causes of splay brought on by shear. Injection molding tool life is the number of production cycles that an injection mold can complete before it needs to be replaced.