Tips for Avoiding Knit Lines in Injection Molding Keeping the proper temperature in the injection molding machine, runners, and within the mold are all key to ensuring. Resin pellets are loaded into a barrel where. Our glossary of terms provides definitions for a wide range of injection molding terms. ABS. Learn how to troubleshoot weld lines in injection molding. 015in wall. They are the result of fundamental physical effects taking place inside of the mold. They again get resolidified along the surface. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. (2) Undesired movement of certain materials in a plastic. Very high quality and an extreme fit may. The resin is transferred to the mold cavity under positive. 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. Raising the mold temperature will keep the material molten longer, resulting in stronger weld lines and even elimination of weld lines. Injection mold design and custom tooling can make or break the success of a finished plastic product. In situ injection molding of continuous fiber reinforced thermoplastic composites is challenged by unbalanced dual-scale infiltration flow due to the pronounced capillary effect. This is a quick rundown on how to handle common features in injection molding designs:What are the advantages of injection molding 1. Trapped gas is one of the most common causes of part burns, and can also lead to short shots and voids, blemishes and discernible knit lines that weaken the part. The main causes of Weld Line or Knit lines are: Convergence of two flowing polymer melt streams during injection molding process: This is the most common cause of weld lines, as the two melt streams coming from different runners or gates in the mold meet and do not fully mix, creating a weak point in the finished product. This article will look at two common venting options—using traditional machined vents and venting through porous materials—to help you decide which is right for your application. Dimensional stability. suppressed cooling and possibly warp. 01 inches between parts fitted together to work best. These knit-lines are well-known as particularly critical regions in the mold when mechanically loaded. Thermoplastic Elastomer Molding Guidelines. A weld line (weld point, flow line or a knit line) forms when separate melt fronts travelling in opposite directions meet. A mold with too few gates is susceptible to cooling problems, but a mold with too many gates. These lines occur usually around holes or obstructions and cause locally weak areas in the molded part. 1513 Sam Bass Rd. Reduce the injection speed to limit the risk of trapping air inside the mold. Additionally. To learn more about us or to get a quote, click here or call 1. The main causes of Weld Line or Knit lines are: Convergence of two flowing polymer melt streams during injection molding process: This is the most common cause of weld lines, as the two melt streams coming from different runners or gates in the mold meet and do not fully mix, creating a weak point in the finished product. Also, since this part will likely be painted or chrome plated, knit lines are a concern. 4271. Understanding Knit Lines in Injection Molding: Causes and Solutions. Weld line defects – also known as knit lines – is a defect that occurs when the injected plastic meets within a mold. Mold bases, ejector plates, and some cavities (if nickel or chrome plated to prevent rust). In plastic part design for injection molding, it is important to design the injection mold so that the molten plastic fills the mold cavity entirely, cools as evenly and as quickly as possible without warping, and functions as intended. Thin wall injection molding can produce walls as thin as 0. When the plastic cools, it takes the shape of the mold and is then ejected and finished. A poor knit line can cause only cosmetic blemishes or it can significantly weaken the structural integrity of a part. Meld and knit lines are actually both different types of weld lines. Ductile Injection Molding 101 - Injection Molding Varying. Also known as string lines. Als einer der führenden deutschen Hersteller von Masterbatches stellen wir nicht nur Farb-Masterbatches, Additiv-Masterbatches und funktionelle Kunststoff-Compounds her – wir leben deutsches Forscher-, Ingenieurs- und Unternehmertum. The knit lines are the result of poor molding conditions (likely molding at too low of a temperature). Flow lines typically manifest as visible marks, often slightly. Hardware components. This configuration positions the injection mechanism at the top of the mold, allowing gravity to play a role in filing the mold cavities. 1050 Walnut Ridge Drive. Please read on, stay posted, subscribe, and we welcome you to tell us what you think. These structures are often small surfaces of about a tenth of an inch in diameter. The relationship between processing conditions, morphological structure and mechanical properties of knit lines of an injection molded semi-crystalline thermoplastic. Let the molten material cool to a solid-state. Its superior flowability allows for precise and flawless filling of injection molds without the risk of flow marks and knit lines. Because this allows some cooling and thickening of the resin, tab gates require a relatively large opening into the mold cavity. Possible causes: Low temperature or fluidity of melted plastic during injection molding. Weld lines: Also known as knit lines, these are molding defects that occur when two flow fronts meet without the ability to “weld. These lines are the result of the molten plastic material recombining after splitting and flowing around an obstacle in the mold cavity. Mold venting is critical to the quality and consistency of the finished part. Knit lines are a common defect in injection molding that can affect the appearance and performance of plastic parts. As these flow fronts come together. mystagingwebsite. If you have questions about the suitability of the Protolabs process for your optical parts, contact an applications engineer at 877-479-3680. Users will be able to use in-cavity pressure or temperature sensors to control when the valves open or close. Called LS IMM Mexico, the subsidiary is based in Monterrey and led by plastics industry veterans Kevin Kim and Fulvio Menconi. As the melted plastic fills the mold, there are locations where the molten plastic flow stream separates and then comes back together. Depending on the design of the mold and the material being injected, a knit line may: present no problem at all, be a. The example. Randy Kerkstra has been in the plastics industry for over 26 years, occupied frequently with. – Change the thickness of the product. For this study, a special injection mold was designed and constructed (Figure 1) in order to produce specimens of various thicknesses (from 2 to 6 mm). Generally all plastic components should be designed with draft where possible. This will help the mold designer to determine the allowable gate and knit line locations. The areas in the cavity where such buildup tends to be common are at end-of-fill areas, details that trap gas, and knit lines. Mold Flow Analysis computer. When assessing issues with injection molded parts, we want to make sure some core aspects of molding are checked. This information is intended to be used only as a guideline for designers and processors of modified thermoplastics for injection molding. In the 1947 book, Injection Molding of Plastics, the late Dr. The specimens with a weld line at the center were obtained by double gate molding and the specimens without a weld line wereInjection runner too small Increase runner as needed. (1987). When venting stationary inserts or core pins in rib or part details with venting issues, I recommend no more than 0. Injection Pressure 0r Speed Too Low Explanation: If the injection speed or pressure is too low, the molten plastic will not be pushed into the mold cavity fast enough to fill and knit at converging flow fronts because it cools down and solidifies too soon. Adjust the design for the flow pattern to be a single source flow. Three terms that often get mixed up are weld, meld, and knit lines. When assessing issues with injection molded parts, we want to make sure some core aspects of molding are checked. By altering the part design, it may be possible to just have one flow front, and avoid multiple flow fronts having to come together. In a plastic injection-molded component, a knit line occurs when 2 different plastic flows emerge in a mold. 6 Monate. 4. A medical device designer might look up a polymer's physical properties and game out. Injection molding is the process of injecting plastic material into a mold cavity where it cools and hardens to configuration of the cavity — is best used to mass-produce highly accurate, & often complex, 3dimensional (3D) end-use parts and products. ABS (Acrylonitrile Butadiene Styrene) Benefits: ABS is a tough, impact-resistant plastic that is widely used across many different industries. Knit/Weld Lines. 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. 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. Injection molding is a popular manufacturing process used to fabricate parts in large volumes. Valve gates are most efficiently. 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. Our plastic injection molding glossary provides key terms. Drying Considerations For both virgin and rework, hopper dryers sized to afford theWhen establishing the parting line, we must first define the shape and position of the parting line on the plastic molded item. Disadvantage: May rust if improperly stored. ABS is a good choice for handheld consumer devices. We have an elite team that designs for injection molding, rapid prototyping with metal and plastic, and produces world-class products under the same roof. extend the time between mold maintenance shutdowns. Meld and knit lines are actually both different types of weld lines. Weld Lines-3 Ways for Detecting and Correcting. Without it, air and gas are trapped in the mold, which compress and heat as the cavity fills. The knit line is generally opposite the gate in thermoset. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. In a weld line, reinforcement fibers. Mold flow analysis is a software simulation that can show how resin will fill the mold during the injection molding process. [1]Weld Lines. We have two unique offers to meet your needs wherever you are in the product lifecycle. TEFABLOC™ TOSI 431 75A is a high-flow thermoplastic elastomer (TPE) designed for large-part injection molding applications, offering exceptional flexibility and weather resistance. Check the diameter of the ejector pins and the pin hole tolerances, if the tolerance is too wide this could allow. Weld / Knit Lines; Assumptions. Some are: Knit lines (discontinuities where two flows merged, creating a weak point)In some situations where a mold has parting line damage, reducing heat can actually improve flash that was a direct result of that damage. Knit lines are hard to eliminate for injection molded plastic parts but designers can minimize cosmetic defects. Learn how material selection, part design, and optimizing process parameters can help eliminate knit lines. This defect is caused when the polymer resin is injected into a mold and flows around a solid piece and forms when the resin collides back together without completely fusing back together. Figure 1: D-shaped through-hole in center of gear part accepts the drive shaft. incomplete filling or shorts. Knit lines don’t always compromise the structural integrity of plastic parts. It’s economical, efficient, and can produce simple to complex parts with low waste. Imagine a river splitting to go around a rock, then meeting up again on the other side. Knit line / Meld line / Transfer line Discoloured line where two flow fronts meet Mould or material temperatures set too low (the material is cold when they meet, so they don't bond). injection molding. The recommended minimum production volume for injection molding is 500 units. There are several possible causes that need to be investigated to troubleshoot weld lines in injection molding. Plastics Technology article (June 2018): Technical capabilities of the process have advanced to erase former cycle-time penalties, and ongoing developments address creation of a materials database and new applications in hybrid composite injection overmolding. 5. These seams are known as “knit lines. Mold bases, ejector plates, and some cavities (if nickel or chrome plated to prevent rust). Venting at Weld Lines. 2. A screw-type plunger forces the material into a heated chambe r,. Exploring common molding defects and. In the plastic injection moulding industry, we work with materials that are by-products of oil refinement and moulds made of metal casting, so our terminology is bound to be at least slightly confusing. Optimizing Mechanical Performance of Injection Molded Multiple Gated Rotating Thermoplastic Components: Part 1 - Consideration of Structural Analysis and Knit Line Effects March 2001 DOI: 10. Inappropriate temperature. In injection molding, a thermoplastic material is melted to a liquid state and injected into a custom, double-sided mold. Moisture in the material due to insufficient drying can form at the melt front, forming an interface between the two melt fronts. Weld lines are a common imperfection to be found in most plastic injected molded parts. 080" – 0. Back to News Page. S. 3. Knit lines are consideredmolding defects, and occur when the mold or/and materialtemperaturesare set too low:. Long shapes are produced without multiple drops or hot runner systems, eliminating knit lines and lowering tooling costs. Weld / Knit Lines; Assumptions. The Jabil Molding Institute empowers employees, customers and suppliers to utilize the most advanced plastics and related manufacturing techniques in the world. With the help of mold flow analysis and mold flow service, mold designers understand how the material fill to position gates better, anticipate where the knit line will appear and locate difficult to fill spots in the injection mold. If life safety is involved, or reliably or efficacy are absolutely required, every part should. The cooler flow fronts of the resin aren’t forced into the mold surface texture as well as the hotter resin behind the flow front. The areas in the cavity where such buildup tends to be common are at end-of-fill areas, details that trap gas, and knit lines. It’s called sequential valve gating, or SVG. such as knit lines and other imperfections. Commonly seen at the edge of a hole or other cored feature, knit lines are—as a. In the injection molding process, knit lines are a common occurrence when two or more plastic flow fronts collide and solidify, resulting in a visible seam or line on the molded part. Facebook. The injection molding process is fairly simple, plastic resin is heated to its melting point and forced through the machine and into your mold to produce your plastic parts. The last cause of flow lines may be the operators running your daily operations. Venting. Dabei erreichen unsere Produkte zufriedene Käufer in mehr als 30 Ländern. Visual indicating with an finished part that are formed by the junction from two plastic flow fronts. These knit-lines are well-known as particularly critical regions in the mold when mechanically loaded. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. Services Group. The definition of weld lines: When multiple plastic flow fronts meet in the cavity after encountering inserts, holes, or areas with inconsistent flow rates or interrupted melt flows, or in the case of gate injection filling, the inability of two or more flow fronts to fully “knit” together will cause the linear weld marks. The most common and one of the most challenging injection molding defects are weld and knit lines. Wall Thickness: The recommended wall thickness for injection molded POM parts is between 0. These knit lines are formed as molten plastic in the injection mold flows around an obstruction like a feature. Most failures occur at what are called “weld lines” or “knit lines”. For best results, keep thickness variations to within 15% of the nominal wall thickness. Knit lines are a common defect in injection molding that can affect the appearance and performance of plastic parts. 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. Because injection mold design and processing is complex, a set solution will not solve all problems. Gate size can be increased or moved to a section with greater wall thickness to help eliminate. 763-755-7575. In this paper, a general and efficient approach was proposed for dual-scale infiltration flow balancing based on numerical simulation. Weld line in injection molding is line where two or more flow molten plastics knit together. 1-3). Image credit: The Rodon Group. Knit lines, also known as weld lines or meld lines, are visible lines or seams that appear on a molded part where two or more flow fronts meet during the injection molding process. The injection molding process uses a granular plastic that is gravity fed from a hopper. AS9100:2016. Short molding cycle, high production efficiency, and easy automation 2. Use the fewest number of gates possible. All the while, the material could be the correct material," Hill says. Consider adding mold release (can be added to the polymer itself by the polymer vendor) or at machine side Knit lines Weak knit lines Increase melt temperature Mold temperature too cold Increase injection speed Avoid nucleated products if possible Inadequate venting7. and Titomanlio, G. The linear mold shrinkage of injection molded parts will vary from 0. When the mold adopts the multi-gate pouring scheme, the plastic melt. Its superior flowability allows for precise and flawless filling of injection molds without the risk of flow marks and knit lines. Not always a problem, but can cause serious structural issues. Flash: All plastic injection molds contain parting lines, which create the potential for small amounts of molten plastic to escape the mold cavity’s boundaries. And the lead-time for overmolded and insert molded parts is 15 days, a bit longer than FacFox’ single-part injection molding turnaround, but still much faster than traditional insert molding. Thus, as the flow continues, the two flow fronts may gradually rejoin to make one uninterrupted flow front. What causes knit lines? Knit lines are formed when the molten plastic flowing into the mold cavity runs into an obstruction, such as a core pin that forms the through hole on a flange of an enclosure. 5 kN/cm2 (4 T/in2 ) is required. Injection moulding (U. Injection molding a red component, for example, can pose a challenge because at time the component may be too thin for the pigment itself!. A weld line can also be called a knit line. knit lines and parting lines are at the discretion of MIC-ZG. PCS says each module of the Polimold Valve Gate Sequencer controls two zones, with the option to control up to 14. Following lists causes and solutions for weld or knit lines. Typical Tool Steel for Injection Mold Construction Steel Type Steel Properties Mold Component P-20 Pre-hardened, machines well, high carbon, general-purpose steel. Plating and painting applications usually require slower fill rates to keep orientation low. Most failures occur at what are called “weld lines” or “knit lines”. The linear mold shrinkage of injection molded parts will vary from 0. Also known as weld lines, knit lines. 025 inches per inch, depending on the particular resin, molding conditions, part design, part wall thickness, and direction of flow. Swirling can increase depending on the material you use, and the texture or polish of injection molding tools. The advantages of compression molding include more isotropic fiber distribution, dimensional stability, and surface finish. Investigate the mold for signs that a water leak is present, and correct the condition. occupied frequently with troubleshooting injection molding. Steven. To learn more about us or to get a quote, click here or call 1-888-893-1587 now. Fig. This article will look at two common venting options—using traditional machined vents and venting through porous materials—to help you decide which is right for your application. 11) The part design must take into account possible knit line locations and work to direct them away from higher stress areas. On a hydraulic machine you can program hold pressure: For example, if you set 850 psi (59 bar), you will get 850 psi hold pressure for the time you set on. From the start of your project, you can count on The Toolroom to exceed your expectations for all of your plastic injection molding needs. May 24th, 2019 Posted in Injection Molding Flaw Repair Preventing Flow Lines, Knit Lines, & Blush Injection molding isn’t an exact science, and there is a lot that can go. For over four decades, our experienced team and leading edge technology have provided you with tooling solutions from start to finish. (1. Injection Molding Materials When using PolyJet molds, both tool life and part quality will be dependent on the thermoplastic material used during the injection molding process. Knit Lines: Holes in the part will always cause knit lines. Plastic injection molding is the industry’s most common way to manufacture parts. 5T, where T is your nominal wall thickness. weld line in injection molding. To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. The recommended minimum production volume for injection molding is 500 units. The thermoplastic injection molding process at BEPL is a standard process involving an aluminum mold with no heating or cooling lines running through it, which means cycle times are a bit longer. Such molds or tools aren’t intended to be used in operation. RJG announced that its injection molding process control system, CoPilot, will begin offering valve gate control technology for hot runners starting in September 2021. Weld lines typically appear in a part when an obstruction of some kind separates the melt flow and prevents it from "knitting" together. It recently obtained a $4. This range can be affected by the part wall thickness, melt temperature, mold temperature, injection speed, hold/pack pressures and also the time between molding and measuring. reduction on the side the part is folding towards. This most often occurs when you have a core or shutoff feature that the plastic needs to flow around. Knit lines form when two or more plastic flow fronts collide and solidify or “knit” during the molding process. Example of a gate location in a finished part Example of knit lines in a finished part. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. Weld lines are formed when there is an inability of two or more flow fronts to ‘knit’ or ‘weld,’ together during the molding process. . The process is extremely versatile, and can produce very complex shaped parts, with the use of multi-sided molds. Runner and gates must be balanced. 2. Increasing injection speed. In a weld line, reinforcement fibers. a knit line will form 180°on the opposite side from the gate location. The result is a consistent flow of molten plastic during injection and a quicker filling time. They occur when melt flow fronts collide in a mold cavity. Slower injection provides less orientation and stress. Throughout the molding process the press operator visually inspects the molded parts as they come out of the mold for any imperfections such as air trap, knit lines, backrinding, or tearing. The bottom of your rib must also feature a fillet. Plastic injection molding has long been an affordable and efficient process for producing custom prototypes and end-use production parts. Plasti-Co ® manufactures a wide range of injection molding nozzles from standard nozzle tips, extended nozzle tips, nozzle bodies, extended nozzles. Disadvantage: May rust if improperly stored. They are formed when two or more flow frontFor more information on our custom rubber molding services or to speak with one of our knowledgeable professionals, please feel free to Contact Us or complete our online Request For Quote form. We recommend walls to be no less than 40 to 60 percent of adjacent wall thickness, and all should fit within recommended thickness ranges for the selected resin. Injection molding machines with footprints similar to desktop FDM and SLA 3D printers are now available. Injection molding is an excellent way to create plastic parts in bulk, but there are many problems that can cause cosmetic defects ranging from minor to major. The plastic in the ‘flow front’ cannot pass through the core pin, so it flows around the core pin splitting into 2 distinct flow fronts. Knit Mark – A witness mark on a molded part, often occurring at the midpoint between two transfer or injection sprue locations. BACKING PLATE – In mold construction, a plate used as a support for the cavity blocks, guide pins, bushings, etc. Redesign the mold: Redesigning the mold to. Generally, the mold structure is roughly divided into two main parts: fixed half and moving half. The parting line location on the injection mold will have an effect on how the cavity and core (both halves of the injection mold) come together and seal. Weld Lines. They are very much related but independent disciplines. Here are some of the most common cosmetic defects and how to avoid or fix them. 0 and Table 1). . The melt is forced to split up during filling of the cavity. Vacuum on the mold does help and many times eliminates the weld line. Brent Strong, p. Core Geometry. Knit lines are consideredmolding defects, and occur when the mold or/and materialtemperaturesare set too low:. The injection molding process uses a granular plastic that is grav ity fed from a hopper. An injection mold that produces pieces while the final tool is being built. Notched weld lines then remain near the cavity walls. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. Reduce the injection speed to limit the risk of trapping air inside the mold. Behind the obstruction, the flows try to merge again, but this is made more difficult by a low temperature of the mold surface and a low melt pressure. The temperature might fall at some places like in the mold, runners leading to the mold and injection molding. More about the knit lines in injection molding. Weld lines typically appear in a part when an obstruction of some kind separates the melt flow and prevents it from "knitting" together. 847-952-8088. One common problem that occurs in injection molding is the formation of knit lines. Plastic injection molding is the process of injecting molten plastic material into a metal tool which then cools and ejects a plastic part from the machine. The Demo Mold helps those new to injection molding easily visualize the process and is a great teaching device for educators. This makes the casting process as efficient and accurate as possible. More about the knit lines in injection molding. Also discussed are weld and meld lines and their effects on molded. The packing pins are sequentially. Ideally, a safety strap should be strong enough to prevent the mold from opening under various unforeseen circumstances, but always less than the holding power of the mold clamps and the machine’s mold-opening force. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. It explored the use of. Submarine gates are another injection molding types of gate that is located below the surface of the part, typically on the underside or back of the part. Draft. When injection molding a part, a knit line may present no problem, or can cause a serious structural problem. Runner Type. Subscribe to Our Newsletter. Macromol Symp 1988;21/21: 489-500. The thermo-rheological findings were used to investigate the sources of weld line weakness. The company provides an array of digital manufacturing expertise. 1. As a result, prototyping is strongly recommended for parts with. Learn more. This most often occurs when you have a core or shutoff feature that the plastic needs to flow around. One of the most common ways of adding venting is by manually machining it into the mold (Figs. 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. PTI, a plastics and metal parts molder, is a leading developer of the MIM process. Gate design is another critical piece of part function in plastic injection molding. Bubbles are caused by melting flow fronts colliding in a mold cavity. Submarine Gates. In fact, knit line strength will decrease with higher filler content and with longer fibers. This is the first article in a new series that will examine the injection molding process by breaking down the path a plastic pellet takes as it is transformed from Pellet 2 Part. Material contamination, for example, can cause several molding issues. Second, the runner leading to a tab gate takes up real estate within the. They occur when melt flow fronts collide in a mold cavity. In injection molded parts, there are 2 types of weld lines: The first type of weld mark is called cold-melt joints and is formed when the melt front enters the cavity with different gates. A meld line occurs when two moving melt fronts converge and flow parallel to each other. Most issues occur before entry into the mold. When injection molding a part, a knit line may present no problem, or can cause a serious structural problem. Computer simulation packages of injection molding have had success in predicting filling behavior in extremely complicated geometries, capable of predicting weld lines’ location exactly. Discover why you should avoid knit lines when designing and manufacturing injection moulded parts. Design with Plastics - for Injection Molding process. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. In layman’s terms, injection molding boils down to four simple steps: Melt material. BACK TAPER – Reverse draft used in mold to prevent molded articles from drawing freely. Gates, vents, sliding cams, pick-out inserts, and any other place where the two sides of. Knit lines, also known as weld lines are areas in the. Knit lines. Knit lines. Shear Controlled Orientation Injection Molding of Polymeric Composites with Enhanced Properties. (See Fig. Injection Molding Press. Release of trapped air in those cases will. Call 800-985-6750 or email your inquiry to sales@customgasketmfg. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. . PAPER ABSTRACT: Desktop injection molding machines and stereolithographic print ed molds make hands-on injection molding production possible in design studio classrooms and labs. The comment on melt flow index is correct, but, I've molded straight PC down to . They again get resolidified along the surface. ). Here are some ways manufacturers can avoid quality issues during the plastic injection molding process: Inadequate Injection/Holding Pressure: If injection and holding. Heat: Too much heat can have an appearance similar to moisture splay. Weld lines may appear like seams or scratches, but that is not what they are. C. Remove holes if possible. It is best practice to maintain a uniform thickness throughout an injection-molded part. Understanding types of injection molding process can help to avoid some design challenges early in the process. What is copper electrode in injection mold? hashtag#plasticinjectionmold hashtag#moldmaking "Copper electrode," also known as "electrode," is a common component in mold manufacturing. Knit lines, also known as weld lines or meld lines, are visible lines or seams that appear on a molded part where two or more flow fronts meet during the injection molding process. It happens when the molten plastic material flows around obstacles, such as inserts or cores, and rejoins on the other side. 1-3). Meld and knit lines are actually both different types of weld lines. The gate location affects the. Chris Newmarker | Dec 27, 2013. Knit Lines and Resins. Mold venting should be checked and increased if necessary, injection molding service. Vertical Plastic Injection Molding. These defects are not visible, like small. Weld lines are also known as “stitch lines” or “knit lines”. The injection molding process is on the surface is fairly simple, plastic resin is heated to its melting point and forced into the cavity of the mold to produce a plastic parts. Weld Lines-3 Ways for Detecting and Correcting. Increase injection speed and pressure: Faster-moving materials will meet more quickly so one doesn’t cool too soon. Weld-line strength for plastics can vary from 20% to nearly 100% of the strength of the plastic itself. Demo Mold.