Also known as knit lines. Weld lines, melt lines or Knit lines could be caused by different causes: - Low temperature of molding machine barrel - Inadequate back pressure - Injection pressure or injection speed is too low - Low mold temperature - Small injection gates and/or runners - Improper location of injection gate - Excessive gate land length1. Injection molding is typically a better choice for more complex parts, while compression molding is a great option for relatively simple designs, including ultra-large basic shapes that cannot be produced using extrusion techniques. 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. Flow Lines. Solution: Increase the injection pressure or speed. Parting lines placed at intricate joints. Therefore, with the cooling process, the resin in the central part shrinks and expands to the surface, resulting in insufficient filling in the central part, which is called vacuum. Weld lines are a common imperfection to be found in most plastic injected molded parts. As a result, prototyping is strongly recommended for parts with. Also, since this part will likely be painted or chrome plated, knit lines are a concern. Recent developments were oriented on the analysis of the mechanical performance at local (knit lines and welds) and bulk (molded part) areas, with the influence of molding and welding conditions. 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. Here are some reasons why design is important for injection molding. 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. It is important when selecting an injection molder that the right process conditions are used to reduce or eliminate the effects of. com TYPICAL PROPERTIES MECHANICAL THERMAL OPTICAL. (for example, a hole on the plastic part), the knit line will be unavoidable. Macromol Symp 1988;21/21: 489-500. This image shows a PVC pipe after it was accidentally dropped on the ground. Randy Kerkstra has been in the plastics industry for over 26 years, occupied frequently with troubleshooting injection molding. 0 to 3. Thermoplastic Elastomer Molding Guidelines. Check/add vacuum; Check mold lube; Check/increase venting. After samples have been approved, it’s time to kickoff. Mold Flow Analysis computer. Learn about the key characteristics of common injection molding materials, recommended applications, and how common thermoplastics compare to one another. In fact, for a 32-cavity mold, the flow rate in this example drops down to 0. Weld line defects – also known as knit lines – is a defect that occurs when the injected plastic meets within a mold. Let’s. N174W21430 Alcan Dr Jackson, WI 53037 262-677-9700; 16685. Mold cores can be machined from a solid piece of copper alloy or inserted to aid in construction or allow for easier replacement if a com-ponent would ever be damaged in molding. Move the injection unit away from the mold during short breaks . Learn more. 2) Vents in an injection mold should let the air out, but not the liquid plastic. Reduction of sink can possibly be had by switching to an ABS/PC-blended material. Mold venting should be checked and increased if necessary, injection molding service. Using abrasives in a pressurized air blast to create a surface texture on the part. 5 to 3. In an injection molded structural plastic part, a weld line (also called a knit line) will result in a region of mechanical weakness as soon as the part is submitted to an external load. A poor design can lead to many visual defects in the final part. 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. Dabei erreichen unsere Produkte zufriedene Käufer in mehr als 30 Ländern. turbulent flow of Injection speed set too high. Plastic injection molding is a complex and highly intricate process. 156 x 1. Be wary of saving too much weight or you might end up with: cracking. Weld / Knit Lines; Assumptions. As. The weld line can either be a minor cosmetic issue. A weld line, also known as a knit line, is a visible line or mark that occurs in an injection-molded part where two or more melt fronts meet and fuse together during the molding process. Crossref. Orientation of these knit (weld) lines, are perpendicular to the tensile stresses, applied to the ring (Figure 6-8). BURN MARKS Burn Marks: burn marks can occur when the design of a plastic part, and the subsequent injection mold design, causes air to be trapped during the injection (or filling stage) of the molding cycle. occupied frequently with troubleshooting injection molding. He is currently a tooling manager for a large, multi-plant molding and manufacturing company. Make sure the venting is not too large. Remove holes if possible. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. A wide variety of tool steels are available for injection mold construction. Runner and gates must be balanced. Participating in DFM and mold flow analysis is a good way to achieve this. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. and to identify potential knit lines. 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 ventingWhat you should know is that there are various failure modes for injection molding. (1. The utility model relates to a mold structure capable of eliminating the appearance of weld lines of a hole-shaped injection molded product. These lines can manifest as visible marks on the component’s surface and potentially affect its structural integrity. Industrial Knitting Machines. These lines occur usually around holes or obstructions and cause locally weak areas in the molded part. Plastic injection molding has long been an affordable and efficient process for producing custom prototypes and end-use production parts. Nicolet Plastics LLC. Below is a list of items that should be checked both during normal molding operations and if defects are detected. 17. Remedies: Increasing the barrel temperatures will allow the flow fronts to stay hotter longer and. Knit lines generally occur around holes or other obstructions to the melt flow. After the solidification of molten plastic, the finished part is ejected out. Injection molding can be a real challenge if you don’t follow the “Five M’s”: Man, Mold, Machine, Material and Method. It is also one of the most important weapons in a molder’s arsenal for making process changes. Thus, as the flow continues, the two flow fronts may gradually rejoin to make one uninterrupted flow front. Computer simulation packages of injection molding have had success in predicting filling behavior in extremely complicated geometries, capable of predicting weld lines’ location exactly. PROBLEM: FLOWLINES (ALSO CALLED WELD LINES OR KNIT LINES) Definition: Streaks, orange skin, or visible flow lines in parts . Having uniform wall thickness makes it possible for the melted plastic to fill the mold evenly, therefore not creating a part with warp, sink, thin knit lines, or other defects. Solution: People. Weld line, also known as knit line or meld line, is a visible line or mark on the surface of a plastic part where two or more flow fronts of molten plastic meet and fuse together. a specific area on one side lens, a warp line, and a weft line. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. Because they can be shut off independently you can control flow fronts and knit-line locations. Meld and knit lines are actually both different types of weld lines. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection molding processing. Polym Compos 1982; 3: 88–96. 1050 Walnut Ridge Drive. Steven. 27-ounce shot size to 600-ton with a 105-ounce shot size. Contact Us. A weld or meld line is a weakness or visible. Comprehensive. This can result in cosmetic defect or a weak point in the part. The mold maker may think that some minor defects are acceptable, or they may not even consider them from the beginning, which can cause problems when the injection mold is being manufactured. In a plastic injection-molded component, a knit line occurs when 2 different plastic flows emerge in a mold. Highly ScalableVacuum on the mold does help and many times eliminates the weld line. Following lists causes and solutions for weld or knit lines. A poor knit line can cause cosmetic blemishes and significantly weaken the structural integrity of a part. Influence of injection-molding parameters on the morphology and mechanical properties of glass fiber-reinforced polypropylene composite. 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). Notched weld lines then remain near the cavity walls. Depending on the resin, resin temperature, mold temperature, and filling. An injection molding machine having a first mold portion and a second mold portion. The design of the mold, as well as the part being molded, has a significant impact on the success of the process. We originally thought it may be caused by a silicone release agent that was occasionally sprayed on the injection mold, but testing with minimal agent and later built-in slip agent showed no change. Knit lines, also known as weld lines, are fine lines that resemble hairline fractures or cracks. By altering the part design, it may be possible to just have one flow front, and avoid multiple flow fronts having to come together. Injection speed and pressure. Reduce the injection pressure. These knit lines affect the parts aesthetics. suppressed cooling and possibly warp. RELATED CONTENT. Table 2 lists the<br /> properties of common tool steels and the typical mold components for which they are<br /> used. To briefly describe, weld lines are also called knit lines. Weld lines are also known as “stitch lines” or “knit lines”. 6. Koelling, Ronald C. The above guidelines for initial heater band settings are for most injection molded parts. a knit line will form 180°on the opposite side from the gate location. This most often occurs when you have a core or shutoff feature that the plastic needs to flow around. 4. Change gate locations. These are imperfections in the part. 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. More about the knit lines in injection molding. Sink Marks Cause 3: Improper Pack or Hold Pressure. Yet a smooth finish sometimes actually highlights flaws like knit lines and blemishes in the part. 040-in. “A knit line in a colored part will result in glaring visual-effect problems, while a knit through a glass-filled part would have a negative effect on both the aesthetics and the performance,” agrees Kurt Weiss, manager of part performance and new material introductions at GE Plastics. CAUSE: 1. Prevent Flow and Knit Lines Through Mold Adjustments. mixed manually and quickly stored in the tank of an injection machine just before the start of the resin injection or (2) the components are stored separately in different tanks of an injection machine with a mixing head. Use a thread with a pitch greater than 0. Mold venting is critical to the quality and consistency of the finished part. These knit lines are usually the weakest areas of the part. 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. This normally occurs around holes or obstructions and causes locally weak areas in the molded parts. Depending on the design of the mold and the material being injected, a knit line may: present no problem at all,. There are times when porous materials like Porcerax are used in problem or backfill areas. However, compression molding often provides poor product consistency and difficulty in controlling flashing, and it is not suitable for some types of parts. There are times when porous materials like Porcerax are used in problem or backfill areas. When venting stationary inserts or core pins in rib or part details with venting issues, I recommend no more than 0. Increase the injection speed. Vacuum. Remedies: Raise the temperature of the mold or molten plastic. 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. Injection molding weld lines refer to a line on an injection molded part that is generated where the two halves of the mold come together. Increase the melt and/or mold temperature. Moisture in the material due to insufficient drying can form at the melt front, forming an interface between the two melt fronts. This production method is particularly popular when manufacturing in large quantities. Mechanical performance of knit lines and welded butt joints – A key factor in designing of multiple gated injection molded and subsequent welded. To prevent knit lines, injection molders can increase the temperature of the molten resin to prevent solidification from starting too soon, and increasing injection speeds and pressure are also potential solutions. 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. This article looks at the issues presented by a weld line in injection molding and the techniques manufacturers can use to avoid them. 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. อุณหภูมิของพลาสติกเหลวสูงเกินไปจนก๊าซหรือความชื้นแยกตัวออกมาได้. With the right nozzle, you can boost cycle. We then. 080" – 0. They again get resolidified along the surface. These materials have beenDetermining the correct tonnage provides a foundation that must be rock-solid to avoid flash and damage. 4. For over four decades, our experienced team and leading edge technology have provided you with tooling solutions from start to finish. 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 adverse effect of knit-line formation on the mechanical properties of thermoplastics has been well documented for unfilled materials. Runner Type. When 2 flows meet, small hair-like discolorations may develop. Snake Lines: The appearance of snake lines is caused by the formation of a jet effect as the melt travels through a gate and into the mold cavity. Three terms that often get mixed up in injection molding are weld, meld and knit lines. Specifically, by having a single, continuous injection outlet 140, molding material can be uniformly distributed throughout mold cavity 120 quickly and consistently without resulting in undesirable molding seams or knit lines. A thermoplastic resin is heated to its melting point and injected into the cavity of an injection mold to produce a specific part geometry. Extreme geometries can cause knit lines. Product designers encounter a wide range of challenges when. By understanding material fill, injection mold designers can better position gates, anticipate where knit lines will appear, and locate difficult to fill spots in the mold. Injection moulding (U. Plastics Injection Molding Expert John Bozzelli covers. Injection molding a part with Class-A surface finish and ribs or bosses has proven an elusive goal for molders, despite their best efforts with conventional injection or internal gas-assist technology. Refers to portion of injection molding part that has some taper to make it easier to remove from the mold. 040 and 0. In places where the plastic flows around a solid piece of the mold, from a simple circle to forming complex shapes like rings or squares. For example, increasing gate size can improve part filling. Mold bases, ejector plates, and some cavities (if nickel or chrome plated to prevent rust). 5 to 3. This line does not normally impact the overall shape or dimensions of the item. The injection molding design process, much like all industrial design processes, deals primarily with the creation, look, and feel of a product. The present. The chart below shows recommended wall thicknesses for common injection molding resins. In addition to the main factory and development. It is caused by the incomplete joining of the uncured. It explored the use of. Don’t forget to eliminate entrapped air in the weld line injection molding; otherwise, it’ll create unfilled portions in your part design, causing more weakening. Meld and knit lines are actually both different types of weld lines. The Bottom Line You might have come across the aforementioned terminology before and did not know what any of the words meant. Plastic melt and mold temperature. Finally, knit lines occur when molten plastic flows around an object and rejoins on the far side, a phenomenon that is quite possible when inserts. In working with the injection molding service offered by Protolabs, you provide. The three dimensional structure is formed of a resin fiber mixture having a resin material infused with carbon fibers having a length of about 12. Knit lines don’t. Injection mold design and custom tooling can make or break the success of a finished plastic product. Increase the mold temperature and reduce the barrel temperature for injection molding of thin-walled products. 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. Inappropriate temperature. 160"). 3 /sec of material into a mold, don’t think the material is going into each cavity of a multi-cavity mold at the same 14. Knit lines, also known as weld lines, are fine lines that resemble hairline fractures or cracks. Knit lines, also known as weld lines are areas in the. A knit line is any line, visible or not, where two resin flows meet. Polym. The defect may be in part appearance or mechanical strength. Crossref. There needs to be a balance between fit of the halves, function of the part, visual quality expectations, and the cost to produce the mold. Venting at Weld 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. [8] Bevis, MJ, Reis RL, Cunha AM. mold venting is at the last filling point, whereby, while the melt flows forward in the cavity, air and gases flow out through the valve. See full list on fathommfg. There are two primary reasons for this occurrence: 1. gate position or runner. PVC pipes are manufactured by an extrusion process. A knit line is what happens when plastic flows coming from two different directions meet inside of the mold and solidify. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. For instance, three widely used processes are insert molding, overmolding, and undercuts. Resin cools as it is injected into a mold. The most common location of knit line formation is behind molded-in holes that are made by core pins in the mold. Additional venting along the parting line perimeter will improve overall venting significantly. Considerations: ABS-molded parts will show knit lines and can have sink and voids in thick areas. These flaws can affect the aesthetic and structural integrity of the. injection molding. Setting that Delta P is the secret to consistent fill time. Numerical results show that weld lines can be predicted accurately, and the formation and evolution processes of weld line can be shown more clearly by co-injection molding technique. It can also aid in material selection since fill. Gating. Let’s. placed usually in the areas last to fill, near knit lines, as well as on the runner system. ABOUT THE AUTHOR. and Titomanlio, G. The most common and one of the most challenging injection molding defects are weld and knit lines. This type of molding uses a single tool to create both the part's geometry and surface finish in one step. Injection Molding: How to Set Second. wall thickness, knit lines, draft. To prevent knit lines, injection molders can increase the temperature of the molten resin to prevent solidification from starting too soon, and increasing injection speeds and pressure are also potential solutions. Whenever possible, vents should be located in the movable half of the mold wherever a gas void or knit line is seen on a part. In compression molding, molds are closed around the charge, and in injection molding, the charge is injected into a closed mold cavity. 020"). doc), PDF File (. Weld / Knit Lines; Assumptions. Depending on the material you use, the knit lines could be invisible or obvious—work with an injection molding company to figure out how to reduce the mold lines on your product. One of these is knit lines, also called weld lines. They are the result of fundamental physical effects taking place inside of the mold. Weld lines or knit lines and meld lines formed when two melt fronts run into each other or join together can be improved by. More about the knit lines in injection molding. such as knit lines and other imperfections. Some of the most popular brands include:Harshal Bhogesra has 9+ years of combined experience in molding, customer & supplier development. Bad habits can cause many different problems with injection molding machines, and flow lines are included in that. Inadequate venting may cause short-shots, poor surface appearance, or weak weld-lines. Weld Lines-3 Ways for Detecting and Correcting. land and using maximum vent depths to get them as close to self-cleaning as possible. Meld and knit lines are actually both different types of weld lines. The knit lines are the result of poor molding conditions (likely molding at too low of a temperature). An obstruction such as a core pin or holes will split the material flow and cause a weld line issue to form on the other side. The part is cooled in the mold until it is solid enough to be ejected. Knit Mark – A witness mark on a molded part, often occurring at the midpoint between two transfer or injection sprue locations. The knit line itself (the vertical line in the middle) is visible in this lighting, but the biggest issue is with the texture. Injection Molding Problems and Solutions (17/17) – Weld or Knit Lines Sep 27, 2022What is copper electrode in injection mold? hashtag#plasticinjectionmold hashtag#moldmaking "Copper electrode," also known as "electrode," is a common component in mold manufacturing. 3. It tells them that you visualized how injection molded parts cool and harden. This will helpTroubleshooting Injection Molding Weld Lines. Knit lines are formed in injection molding when two flow fronts meet in the middle of a part (a line where two sides of the plastic are “knit” together). Product designers encounter a wide range of challenges when. Gas trapping/ poor venting. 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. The knit line strength and other packing related properties both aesthetic and functional of injection molded polymeric products is improved by equipping the mold with packing pins. Sink Marks Cause 4: High Mold Temperature. Knit Lines. Observation on a “trial and error” basis may be required. Notched weld lines then remain near the cavity walls. Formation of knit line. Design bosses with an outer diameter equal 2x the nominal diameter of the screw or insert. 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. Remove the hardened material from the mold. Disadvantage: May rust if improperly stored. Also known as a knit line, this is the point at which two flow formations meet and are unable to. Add a 0. Knit lines don’t always compromise the structural integrity of plastic parts. 6. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. Take these steps to avoid knit lines. The goal is to create a uniform thickness and at the smallest (thinnest) level required. Raising the mold temperature will keep the material molten longer, resulting in stronger weld lines and even elimination of weld lines. 0 and Table 1). A screw-type plunger forces the material into a heated chambe r,. Obstructions in the part create weld lines or knit lines during injection molding. Solution: Increase the injection pressure or speed. As these flow fronts come together. ”. 7. The area generally has lower strength than the other areas of the part. A poor knit line can cause only cosmetic blemishes or it can significantly weaken the structural integrity of a part. , 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. Injection molding flow lines typically fall into one of the categories mentioned in the following table: Category: Type of Flow Line: Appearance (What It Looks Like) 1. One of the common defects that can occur in injection molded parts is weld line. Knit Lines and Resins A knit line is any line, visible or not, where two resin flows meet (see Figure 2). Our goal of 100% efficiency, zero scrap and repeatable processes can sometimes be hindered by poor setups or changes in the molding process. The Problems & Solutions course is designed to train injection molding personnel in. Injection molding is an efficient, often cost-effective way to manufacture custom plastics that are strong, durable, and long-lasting. They have their origins in material choice, part design, tooling, and processingIn 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. That’s the air escaping out of the nozzle until the hose is full of pressurized water. Knit lines are typically much weaker. There are processes such as gas assist that do not require the injection unit to pressurize (pack out) the cavity, but for our discussion, we will stay with conventional injection molding. The fluid path has an inlet and a radially continuous, downwardly. Compression-molding is also suitable for ultra-large basic. In a weld line, reinforcement fibers. Rapid heat-and-cool molding technologies have attracted increasing. An injection mold that produces pieces while the final tool is being built. Meld and knit lines are actually both different types of weld lines. POROUS MOLD MATERIALS. Achieving a high-quality surface finish can be challenging, and other methods, such as polishing or coating, may be required. This will help the mold designer to determine the allowable gate and knit line locations. Causes 1. Learn how HPP maximizes these specialized processes. Learn about the key characteristics of common injection molding materials, recommended applications, and how common thermoplastics compare to one another. Knit lines appear to be a faint line or a crack in the finished part after it comes out of the injection mold. For. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. Inject the molten material into a mold. Support pillar suppliers can help determine the. 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. One exception: ribs should be about 50. 040 and 0. Cooling Lines, Injection Mold Material has a great impact on injection molded part quality. Considerations: ABS-molded parts will show. 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. 3—Another issue with the four-gate design was that knit lines ended on or near mounting holes, causing a. 030- to 0. Plastic injection molding is the industry’s most common way to manufacture parts. You don't give us much to go on. Three terms that often get mixed up are weld, meld, and knit lines. A. 060 and 0. This picture shows a. Figure 1 Flow Lines Knit or Weld Lines Cavity Gates Table 1 Knit line in a multi-injection-point cavity. 0 mm) is crucial to ensuring that parts cool evenly. How weld lines form. Dedicated to strict quality management and thoughtful client services, our experienced staff customers are generally available to discuss your demands and guarantee full client pleasure for Knit Line Injection Molding, Electronics. A knit line, also. Misra A. Reduce the temperature of the mold and plastic being injected. Use the fewest number of gates possible. It is. Weld line. incomplete filling or shorts. The cracking was always located in the weld/knit line and therefore caused by weakness in the bonding of the plastic at that line. The Difference Between Knit and Meld Lines–and Why It Matters. Holes in plastic parts are normally cut with a router (or drilled if round. And often, the mold is the same color as the plastic polymer, or can appear that way due to a lack of contrast caused by difficulties lighting the inside of the mold. 2. In injection molding, it is often important to maintain consistent color throughout the part. Incompletely fused extrusion knit Line. These knit-lines are well-known as particularly critical regions in the mold when mechanically loaded. [email protected] 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. The effect of holding variables and of injection and mould temperature was explored. Obstructions in the part create weld lines or knit lines during injection molding. Also known as “stitch lines” or “weld lines”. Anisotropy. Expand. This is easier to accomplish on. 5 inches) dispersed throughout the structural automotive sub frame component ( 10 ). Typically, injection molded parts will be between 0. Reducing the dimensions of the runner system. Learn how to troubleshoot weld lines in injection molding. The packing pins are sequentially. As. As the polymer resin is injected into a mold, it flows through all parts of the mold. They again get resolidified along the surface. Weld lines also can be visible after a part is painted and can cause wrinkles on in-mold-label injection-molded products. These knit-lines are well-known as particularly critical regions in the mold when mechanically loaded. For example, warping, sink marks, drag marks, and knit lines can all impact the visual appeal of the manufactured part. This article will discuss the importance of injection molding nozzles and what makes a good nozzle for a molding or injection. 2. These are caused by the shot of molten plastic moving at different speeds throughout the injection. Additionally. 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. Basic rule of thumb air in mold must be able to escape at theAbstract The knit line structure of injection moulded PA 6 samples was analysed by SEM and optical microscopy. Weld Line Phenomenon: Surface defect in which the weld, or the part where the flows of melted plastic meet inside the mold, shows up on the surface as a groove or pattern. The specific method is that when the product is just filled and filled in the cavity, the insert. These knit-lines are well-known as particularly critical regions in the mold when mechanically. Weld lines often leave witness marks in the moulding surface. The specimens with a weld line at the center were obtained by double gate molding and the specimens without a weld line wereTherefore, changing the edges and corners of the mold core to make it buffer transition and keep the melt flow stable can prevent the occurrence of wavy lines. Without adequate support pillars, flashing of the parting line faces and bowing of the plates may occur. Increase injection speed. Sink Marks Cause 5: Improper Part Geometry. So. Islyn Thomas summarized the need for a particular vent location better than I ever could. Part thickness control is through stacking of.