Flow lines are lines or streaks visible on the surface of a part. They occur as a result of different flow rates of molten plastic in the mold cavity. Sufficient draft is an important part of any mold design, and quick-turn tooling is no exception. Weld lines are usually pointed out as the weak region in molded parts. 3 the path lines of selected material elements can be observed which are. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. 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 significant part of that is the cooling design, where there are many things to consider. 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. The Smartflow Reynolds Number Calculator is provided as a service to the injection molding community as an easy-to-use online resource. Drain the hopper if you were working with 100% regrind, clean if necessary. On a small four-cavity tool, the part had a U-shaped notch in the center. The edge gate is the most popular and straightforward injection mold gate design. 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. This slight depression is a tiny line called the weld line or knit line. As these flow fronts come together. [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 may also appear as ring-shaped bands on a product’s surface near the entry points of the mold, or “gates”, which the molten material flows through. 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. These lines can occur due to variations in wall thickness, gate location, or the geometry of the part. 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. 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. Solution: If possible, operate the machine on. This article continues our series of troubleshooting reports from one of the leading on-the-spot problem solvers in the molding industry. Otherwise, the heat transfer of. 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. 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. In this study, a fully automated. Flow lines appear as a wavy pattern often of a slightly different color than the surrounding area and generally on narrower sections of the molded component. Flow lines or marks appear as banded discolouration on the surface. 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. Injection molding can be performed with only one of these materials like glass, plastics, etc. 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. This method can be helpful in. But add 30% glass and weld-line strength retention drops to only 34% as high as the compound with no. In the injection molding process, weld line regions occur when a molten polymer flow front is first separated and then rejoined. The plant water system is a critical component of an injection molding facility. Weld lines typically appear in a part when an obstruction of some kind separates the melt flow and prevents it from "knitting" together. Thus, as the flow continues, the two flow fronts may gradually rejoin to. Weld lines in injection molding are formed when two or more flow fronts of molten plastic material meet and merge during the molding process. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. The chart below shows recommended wall thicknesses for common injection molding resins. 750 in. 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. process can be fully completed. How to solve flow lines in injection molded products?Injection molding is a heat-transfer process. However, you can easily prevent such defects by simply adjusting the temperature, flow rate, or other mold parameters. Peering into the Flow. Reasons and solutions. Below are ways through which you can remove and prevent flow lines; a. Minimum turbulent flow would be 12-14 GPM, while numbers in the 20’s would be identified as an excellent flow rate. Within more basic plastic part design plans this plane can be a simple, flat surface, but it is often a complex form that. Mold makers should also pay attention to sprue, runner, or gate design. Injection molding is the most cost-competitive technology for manufacturing high volumes of identical plastic parts. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Let’s take a look at some defects that are caused purely due to faults in the injection mould process. 000 0. Fast injection gives you a glossy part, which is what we wanted in this. Several factors can contribute to shrinkage in injection moulding, including material, part design, mould design and processing parameters. Weld lines are a kind of Achilles heel of plastics. 3). The line actually indicates the parting ‘plane’ that passes through the part. 100 to 0. 004 m, a characteristic velocity ν 0 =0. Secondly, it is easy to form obvious. In narrow fields, a limited amount of molten liquid can solidify and block the flow. How weld lines form. In Fig. The leading edge of the flow, or the melt. Add more cooling circuits. Since these materials behave and respond differently, it is crucial. Weld lines have been one of the common defects puzzling the injection molding industry. Well, what this simply implies is that injection polycarbonate molding makes it possible for you to create a wide range of part sizes. 005 0. ” What else can you do about weld lines—besides redesigning the mold or gate locations or adjust the flow pattern during fill with sequential valve gating? I recently saw a report on this issue from Moldex3D, the maker of molding simulation software. Certain injection molding processes may not be effective for the production of some parts. It can also aid in material selection since fill. Effects of mold temperature and pressure on shrinkage 0. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. The melting temperature is 217–237 °C, and the thermal. Faster injection increases pressure in front of a flow front. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. If larger gates are used, expect a longer molding cycle time. How to recognize, prevent, and counteract flow lines defects in injection molding? Learn. 10 in Nguyen-Chung et al. When injection molding a part, a knit line may present no problem, or can cause a serious structural problem. The barrel temperature is too high. These flow fronts occur when the molten plastic material encounters obstacles, such as inserts, ribs, or other features within the mold cavity. Flow Linesparticles, during injection molding, will produce visible flow and weld lines. The recommended minimum production volume for injection molding is 500 units. Here are some ways to avoid. Before injection molding, there is a large amount of air in the flow path and the cavity. Flow Lines and Flow Marks. Phone (630) 665-8590. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. However, you can easily prevent such defects by simply adjusting the temperature, flow rate, or other mold parameters. Mold Flow - Position ribs such that the plastic has an optimal flow path. In a weld line, reinforcement fibers. 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 ]. Increase the injection speed and mold/operational temperature to prevent fracture or surface breakdown. 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. 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. Like flow lines, burn marks do not usually compromise the item's integrity, but they may become a problem once the product is burnt to the point of degradation. The primary reason is insufficient plastic fluidity. Thick sections take longer to cool than thin ones. Flow lines. As the name implies, it is usually positioned along the edge of the workpiece, forming a visible mark at the demarcating line. ” Flow marks do not affect component integrity. Flow LinesWeld lines are the def ects in. The streaks form from plastic in the mold overlapping with plastic following it. 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. Manifesting as wavy lines or streaks on the surface of the molding, flow lines generally occur when molten material flows. 182-185, 2013. html. Avoid knit lines when designing a molded part to improve cosmetic appearance and functionality. If the mold itself has cracks or defects, the finished product will also have various problems. 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 can prevent the opportunity for trapping air. 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. There are three stages of flow – laminar, transient and turbulent. Non-uniform cooling of mold causes warping, creating internal stresses within the part and resulting in distortions. injection mould simulation at steady flow rate. 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. It also may be that your injection speed is too low, which will cause the molten plastic to solidify at different rates. Increase the injection speed, pressure, or temperature of the material. Look for signs of stickiness or burning. 4. Venting is required to allow the air in the sprue, runner and cavity to leave the tool as the melt flows into the cavity. Basic Repairs for Warping. Study shows that the root cause of jetting is related to the mold design on the one hand and the viscoelasticity of the material on the other. How a mold is watered is key to a processor's goal of consistency. Our glossary of terms provides definitions for a wide range of injection molding terms. Another advantage to using valve gating is the amount of control it gives you over the injection molding process. The formation of weld lines and their location along the flow path is a well-studied phenomenon in conventional injection molding; however, only a few papers are devoted to micro-injection molding [11,13,14,15,16]. In manufacturing, the Weld line or Knit line or Meld 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. In injection molding, it is often important to maintain consistent color throughout the part. As the material properties of. After exhaustive research, testing and pilot-scale demonstration, the team developed a breakthrough new technology utilizing low constant injection pressure. Solution: Utilize a material that has the stiffest flow possible without causing non-fill. Wavy lines are another feature of weld lines. On thicker sections of the mold, there may be sinks caused by bosses designed into the backside of the surface. 2), the plastic enters the mold at a relatively fast rate and forms the skin. Remedies: Raise the temperature of the mold or molten plastic. Mold flow analysis is a software simulation that can show how resin will fill the mold during the injection molding process. Introduce automation into the injection molding process for improved efficiency. 0 is leading the productivity and efficiency of companies to minimize scrap rates and strive for zero-defect production, especially in the injection molding industry. Flow marks, also known as flow lines or weld lines, are common defects that can occur in plastic molded parts. (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. Complexities in the design and intricate pathways in the mold can also create flash in injection molded parts. Mold Flow - Position ribs such that the plastic has an optimal flow path. FOW Mould is one of the best companies that use injection molding. The position, length, and angle of weld lines are dependent on the gate location, injection speed, injection pressure, mold temperature, and, especially, the direction and degree of the polymer melt velocity in the. 160"). On average, larger injection molding machinery can cost from $50,000-$200,000 or more. The strong molecular. Reposition gates and runners to allow resin to flow around the obstruction from a different direction. One of the best ways to determine part shrinkage for complex components is with a mold flow analysis. There are a few adjustments that you can make to your injection molding process to prevent flow lines, including: Increase the injection speed, pressure, or material temperature: Slow-moving molten plastic is more likely to cool. injection molding. This results in a much greater amount of vent flow area for the compressed air to exhaust through, and still protects the corners. 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. Flow Rate. Flow lines are aesthetic defects that occur on plastic products. They are evidence of nonuniformity in flow pattern upon entry into the mold. It is a well-known fact that weldlines are unavoidable in most injection-molded products of even moderate complexity. On a small four-cavity tool, the part had a U-shaped notch in the center. Mold is not vented properly causing slow flow at knit lines. The process involves the injection of heated, liquefied plastic into a temperature-controlled mold under high pressure. c. Round the corners of the mold where wall thickness increases: This. A mark on a molded piece made by the meeting of two flow fronts during molding. 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. Vacuum Voids. 025 inches per inch, depending on the particular resin, molding conditions, part design, part wall thickness, and direction of flow. This review process showcases a company’s technical expertise, the capabilities of its design team, and overall quality. Midland, MI. Flow lines are surface irregularities, wavy patterns, or a rippled effect, perhaps of a slightly different color, that can appear in injection molded parts. The importance of understanding the causes of flow lines is critical for preventing them from occurring during the injection molding process. At some point in time, it can no. 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. However, the weld line may not continue throughout the flow. Once the mold is created and the machine is set up, additional parts can be manufactured very fast and at a very low cost. Image 4: Top, HDPE streamlined structure. Plastic Injection Molding Process. 010 0. Increase the mold temperature. The plastic pellets must be. In the plastic injection molding industry, we work with materials that are byproducts of oil refinement and molds made of metal casting, so our terminology is bound to be at least slightly confusing. Laminar flow in a plastic mold, described by. (All Illustrations: S. 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. Features such as sharp corners or undercuts can. Haagh, in Encyclopedia of Materials: Science and Technology, 2001 3 Modeling. The production cost is closely related to productivity. So when two. Too hot and the plastic will start to degrade, but too low and flow marks increase. 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. These properties make it ideal for. Accept All. 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. The resulting defects don’t stop at flash only. "Design and Mould Flow Analysis of Injection Mould for Connecting Link," International Journal on Emerging Technologies, vol. Typically, flow lines are caused by the liquid plastic cooling at different rates. This production method is particularly popular when manufacturing in large quantities. Low cushion and hold time. The mold should have a fine matte finish to allow air to vent quickly and the parison to conform to the mold surface while it is still hot. 2. 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. Each material has a maximum flow length for a given injection pressure and wall thickness — this is known as the flow ratio. Sink marks are like little craters formed on an injection-molded product. Consider the following examples of cooling channel configurations in P20 mold steel with a water line diameter (D) of 11. These streaks or patterns can affect a part's aesthetics, value, and. Taking proper care to design the mold properly, avoiding bottlenecks, and changing the number or location of gates can improve performance. What it is:Jan 04, 1999. Plugged or inadequate vents n Clean plugged or dirty vents, particularly those along the parting line. Commercial injection molding simulation packages, such as Moldflow and C-MOLD, have been incorporating GAIM options to provide computerized design and optimization tools for GAIM processes and. How a mold is watered is key to a processor's goal of consistency. 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. Another solution may be to pull a vacuum on the mold just before injection. The thermo-rheological findings were used to investigate the sources of weld line weakness. Several factors contribute to the formation of flow lines, including material properties, mold design, and process parameters. Weld‐line is a defect that arises in injection molding when two or more flow fronts collide. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. Using cooling simulation to circuit your cooling lines properly. Flow lines. Injection molding machine . 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. This results in an incomplete part at the end of injection molding. Weld Line defect analysis, the most common of many defects in injection moulding products. Weld line. They appear around holes or seams of an injection molded part, and some may call them “flow lines” or “weld lines”. Injection molding is a great technology for finished production on a massive scale. Inadequate mold wall thickness leads to uneven cooling and hindered plastic flow, resulting in weld lines. Basic Repairs for Warping. Materials that have physical fillers like glass, carbon, metal flakes, etc. 025 100 120 140 160 180 200 220 240 Mold Temperature (F) LDPE PPFor 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. The material is kept poured into the mold for some time. or too much shear heat burning the material prior to injection. You might have come across the aforementioned terminology before and did not know what any of the words meant. Investigate the mold for signs that a water leak is present, and correct the condition. They appear as waves or lines, usually of a different color tone from the surrounding area. Flow lines appear like off-tone patterns on the surface of your finished parts. The Problems & Solutions course is designed to train in the recognition and analysis. A meld line occurs when two moving melt fronts converge and flow parallel to each other. V. Make sure the venting is not too large. Listed below are some factors to consider when designing ribs for injection-molded parts. 1) Snake flow lines. Weld Lines. 5. This. Flow marks occur as circles or lines that occur around the gate. reduce the ability to positively influence the strength. These data were obtained from many andGenerally, injection molding resins are characterized as having medium, high or very high flow. The difference between a knit and meld line is significant, dramatically impacting the part’s structural integrity. 1). The molding process is the leading cause of defects in injection molding parts. The Bottom Line. Injection molding tool life is the number of production cycles that an injection mold can complete before it needs to be replaced. Incorrect gate positions cause multiple flow fronts that struggle to merge. 060 and 0. Flow lines result from uneven cooling of the plastic within the mold. In this guide, we cover evaluation and also the remedy of flow lines in. Flow Lines. Chart 1: Diameter versus turbulent flow. wide. 6 T) as thick as the nominal wall. • Reduce runner dimensions and maintain the same flow rate. 1. For example, filled resins and ABS are more likely to. Adjust the design for the flow pattern to be a single source flow. Flow lines, also referred to as flow marks or weld lines, are visible lines or patterns on the surface of a plastic component. Height – Make the ribs 3 times the height of the nominal intersecting wall (3T). Flow lines are. Ensure that injection pressures are appropriate (under 70 MPa [10,000 psi]). This injection molding defect appears as black or rust-colored discoloration on the molded part's surface or edge. Symptoms: Flow lines will typically appear as discolored “bands,” or sometimes “wavy. 7 of the reference. (3) Adjust the temperature of the barrel and nozzle: the viscosity. First, excessive injection pressures may be forcing the mold apart. Flow lines, also referred to as flow marks or weld lines, are visible lines or patterns on the surface of a plastic component. Weld lines have been one of the common defects puzzling the injection molding industry. It has larger cross-sectional regions that allow sufficient molten plastic flow into the cavity. 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. In injection molding weldlines are generated when two separate melt streams join either. Burn Marks. Weld lines in injection molding occur when two flow fronts meet and create a visible line on the surface of the molded part. This carbon will hang up in areas and is difficult to remove. Before his present assignment, Bob managed a molding operation for 25. Sources of defect: Material: Material too high viscosity; Method: Injection speed in the critical area too high (too low)Flow lines are one of the most common problems with injection molding. Effects of mold temperature and pressure on shrinkage 0. Causes – Remedies. The primary cause of cracking is stress and deformation brought on by the external environment, cold mold surfaces, and low injection rates. A. This defect compromises aesthetics. Let’s take a look at some defects that are caused purely due to faults in the injection molding process. If the cornflake pigment contains a large amount of fine particles, this will result in a higher definition of flow and weld lines. Countermeasures to Injection. For optimal cooling, these waterlines are located as close as possible to the surface of the molded part. Impurity. If the mold temperature is too low, the material temperature will drop very fast, so the injection pressure and the holding pressure will not be high enough to press the solidified layer against the mold surface, thus leaving flow lines along the melt flow direction. It has larger cross-sectional regions that allow sufficient molten plastic flow into the cavity. Depending on the extent, these can become defects in the case of molded products in which their external appearance is an important aspect of quality, such as in the case of home electrical appliances, containers for. Kobayashi et al. Peering into the Flow. 1 Caused By The Quality of Injection Mold. The proposed method is first applied to the simulation of HDPE melt in a classic Poiseuille flow case, and then two. In this lesson we will focus on the meld and weld lines. Possible causes: Low temperature of injected melted plastic or slow injection speed during injection molding resulting in low fluidity of plastic inside the mold. In a plastic injection-molded component, a knit line occurs when 2 different plastic flows emerge in a mold. The injection molding gate generates heat by dissipation. In this study, a new specimen design is introduced for the tensile testing of micro parts. Quality concerns in injection-molded materials can vary fr. 18/06/2021. 0030 in. This “inside-out” flow of the plastic mimics the flow in a water fountain, therefore it is called fountain flow. [22]. 9 – Over Packing. 0005 in. In the process of injection molding, the quality of the mold plays a decisive role in the quality of the finished product. 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]. Weld lines in injection molding are formed when two or more flow fronts of molten plastic material meet and merge during the molding process. Errors like these manifest when processing is done incorrectly. This “inside-out” flow of the plastic mimics the flow in a water fountain, therefore it is called fountain flow. 750 in. 150 in. 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. Novel Nozzle Tip Prevents Stringing, Saving Molds & Cycle Time. If packing around a detail is causing cracks/ shorts/burns on the knit line, reduce the heat to improve knit line seal and strength. 3) Poor Preventative Maintenance. The formation process of weld lines can be described as follows: Injection moulding (U. They are caused by improper bonding and low injection pressure and speed [ 46 ]. Injection Molding (IM) Solutions 1019 Balfour St. 5. This action could indicate that one portion of the plastic flow will move more quickly than the other. 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. Select a plastic that is less prone to shrinkage. So what does the 140F mold temperature give us? The molding technician thought the 140F mold water was OK because the data sheet provided by the material supplier suggested mold temperatures from 75 to 180F. In terms of viscosity, higher heat equals faster flow and lower heat equals slower flow. 2. • Move injection locations to make flow fronts meet more obliquely, turning the weld line into a meld line. with a characteristic length χ 0 =0. Do not keep the hopper full; hand-feed if necessary. At the high end of SOLIDWORKS Plastics simulation in Plastics Premium, mold-level analysis can be performed by representing the runners, cooling channels and a mold body around the cavity. (3) Improving the surface gloss of the product. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. Consequently, it causes viscous dissipation which leads to the generation of heat. Bob Hatch is manager of technical service and customer support for Prime Alliance, the Des Moines-based resin distributor. They can be off-color or discolored material compared to the intended color of the part. RapidDirect – Your Best Injection Molding Partner. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. The formation process of weld lines can be described as. Increase the size of the gate and reduce the thickness of the walls of the molded part. 3. 030 0. If the mold itself has cracks or defects, the finished product will also have various problems. Lookalikes include surface scratches, scuffs, flow lines, delamination from contamination, and flaking. Each needle valve nozzle opens only when the melt front has moved across its gating point. Take these steps to avoid knit lines. S. Ensure sufficient cooling time to avoid locking residual stresses into the part. Bad habits can cause many different problems with injection molding machines, and flow lines are included in that. 005 0. The accompanying table lists the flow rates for various barrel diameters at various injection velocities. wide. Flow Lines. 015 0. 1 m/s, and a zero-shear-rate viscosity η 0 (T 0)=3760 Pas. If the cornflake pigment contains a large amount of fine particles, this will result in a higher definition of flow and weld lines. Leadtime Leader 2024. More about the knit lines in injection molding. 025 100 120 140 160 180 200 220 240 Mold Temperature (F) LDPE PPWhen it comes to injection molding, the chances you might end up making a costly mistake is too high. 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. For instance, the plastic used for gears must be completely smooth. Using a thermoplastic that stays in a.