Resin cools as it is injected into a mold. The chart below shows recommended wall thicknesses for common injection molding resins. Koelling, Ronald C. The relationship between processing conditions, morphological structure and mechanical properties of knit lines of an injection molded semi-crystalline thermoplastic. With ABS injection molding, you get the collective benefits and properties of three monomers. The process involves feeding the material into a press, where it is cooled or heated as per. 197 in. The diameter of the secondary runner would be the diameter of the tertiary runner times the number of branches to the 1/3 power (cube root). The total amount of scrap being produced during injection molding will usually be higher than that for compression molding because of the additional material loss created. The injection of molding compound into the parts through one or two gates may produce parts that have knit lines. Inadequate injection pressure can result in knit lines and a surface that. Cold weld line or known as “knit line” isWeld Line defect analysis, the most common of many defects in injection moulding products. Be wary of saving too much weight or you might end up with: cracking. During injection, support pillars keep closed the two halves of the plastic injection mold. ABOUT THE AUTHOR. To learn more about us or to get a quote, click here or call 1-888-893-1587 now. Find out more by calling 573-437-4154 today or email us. Product designers encounter a wide range of challenges when creating and developing molded parts, such as stress factors, warp, and those pesky knit lines. 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. spelling: injection molding) is a process for producing parts by injecting molten material into a mould, or mold. They occur when melt flow fronts collide in a mold cavity. Learn how to troubleshoot weld lines in injection molding. Most failures occur at what are called “weld lines” or “knit lines”. Knit lines don’t. Avoid adding threads directly on your injection molded part. 1 in. The influence of knit-lines on the tensile properties of injection molded parts. Knit lines, also called parting lines, are any lines where two resin flows meet and may or may not be visible. Bad habits can cause many different problems with injection molding machines, and flow lines are included in that. Knit line strength is improved since. 18/06/2021. These knit-lines are well-known as particularly critical regions in the mold when mechanically loaded. Mold Venting. Disadvantage: May rust if improperly stored. This will helpTroubleshooting Injection Molding Weld Lines. Highly ScalableVacuum on the mold does help and many times eliminates the weld line. When the mold adopts the multi-gate pouring scheme, the plastic melt. The point I am making here is, if you’re injecting 14. Reduce the screw speed and adjust the backpressure. But add 30% glass and weld-line strength retention drops to only 34% as high as the compound with no weld line. 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. Support pillar suppliers can help determine the. 1. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. Meld and knit lines are actually both different types of weld lines. To prevent swirling, perform tests whenever possible and use pre-compounded resin to ensure identical color match across parts. com Three terms that often get mixed up in injection molding are weld, meld and knit lines. By altering the part design, it may be possible to just have one flow front, and avoid multiple flow fronts having to come together. The part weight x number of cavities + runner weight should. Plastic injection molding has long been an affordable and efficient process for producing custom prototypes and end-use production parts. They occur when melt flow fronts collide in a mold cavity. Product designers encounter a wide range of challenges when creating and developing molded parts, such as stress factors, warp, and those pesky knit lines. These materials have beenDetermining the correct tonnage provides a foundation that must be rock-solid to avoid flash and damage. LOCATION: Along any parting line. A meld line occurs when two moving melt fronts converge and flow parallel to each other. Knit lines, also known as weld lines, are fine lines that resemble hairline fractures or cracks. Knit lines. ”. TWIM=Thin Wall Injection Molding; TSL=Toys,Sports and Leisure; NB=No Break; IMR=Inter Material Replacement. Depending on the design of the mould and the material being injected, a knit line may: present no problem at all, be a cosmetic issue, or cause a potentially. Steven. A poor knit line can cause only cosmetic blemishes or it can significantly weaken the structural integrity of a part. Very high quality and an extreme fit may. Participating in DFM and mold flow analysis is a good way to achieve this. The packing pins are similar in construction to mold ejector pins and may also be mold ejector pins depending on mold configuration. 156 x 1. To avoid these defects, manufacturers can check molds for the following: Low Mold Temperature: A mold temperature that’s too low will cause the material temperature to drop fast. (for example, a hole on the plastic part), the knit line will be unavoidable. Increase injection speed and pressure: Faster-moving materials will meet more quickly so one doesn’t cool too soon. Weld or knit lines occur when melt flow fronts collide in a mold cavity. 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 fact, for a 32-cavity mold, the flow rate in this example drops down to 0. 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. Weld Lines. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. This can enable the manufacturer to increase the molten plastic temperature at the front of each flow and avoid the occurrence of weld lines. More about the knit lines in injection molding. They again get resolidified along the surface. Three terms that often get mixed up are weld, meld, and knit lines. Weld lines typically appear in a part when an obstruction of some kind separates the melt flow and prevents it from "knitting" together. weak knit lines and fracture points. 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. With over 50 years of experience, Universal Plastic Mold can help you avoid (or at least minimize) knit lines in your molded parts. Learn more about the process by reading this white paper. directly! FCS Group, based in Taiwan, was established 40 years ago and is well known in Asia as a quality manufacturer of machinery, offering several lines of injection molding machines and other specialty and customized equipment. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. Orientation of these knit (weld) lines, are perpendicular to the tensile stresses, applied to the ring (Figure 6-8). On the other end of the scale, a desktop injection molding machine with 5 tons of force can cost between $30,000-50,000. 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. Parts molded with ABS are susceptible to forming knit lines, which are visible lines on the surface of the part. 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. injection molding. Parts as thin as 0. ”. Venting. 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. Designers are able to specify seamless design features with compression molding. placed usually in the areas last to fill, near knit lines, as well as on the runner system. Left: L-shaped perform. Gate size can be increased or moved to a section with greater wall thickness to help eliminate. Additional venting along the parting line perimeter will improve overall venting significantly. 827 Holes and Bosses. SEA-LECT Plastics has 16 MILACRON injection molding machines that range from 33-ton with a 2. Polym Compos 1982; 3: 88–96. Here are some reasons why design is important for injection molding. Sink. The mold’s sprue bushing and locating ring is placed in a way that makes sure the injection molding nozzle is properly aligned and centered. 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. Weld / Knit Lines; Assumptions. 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. This is a video excerpt from our Problems & Solutions Course - Weldlines. Surface Finish: The injection molding process may result in visible knit lines or parting lines on the part’s surface. 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. Remove the hardened material from the mold. N174W21430 Alcan Dr Jackson, WI 53037 262-677-9700; 16685. In the world of injection molding, each weld. 3—Another issue with the four-gate design was that knit lines ended on or near mounting holes, causing a. Our plastic injection molding glossary provides key terms. POROUS MOLD MATERIALS. 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. Getting started; Knit Line Injection Molding; Knit Line Injection Molding - China Manufacturers, Factory, Suppliers. 0mm) throughout will ensure that the parts cool evenly and will prevent warping. 1. DFM Helps Prevent Sink Marks In Plastic Injection Molding. Flow Lines Knit or Weld Lines Cavity Gates Table 1 Knit line in a multi-injection-point cavity. Plastic injection molding is the industry’s most common way to manufacture parts. , 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. Prevent Flow and Knit Lines During the Injection Molding Process Timing and temperature are significant contributing factors when it comes to flow and knit line. "As soon as that part or material is stressed, it can be real conducive to fracture, cracking, breaking, just because of the way it's been molded. In fact, knit line strength will decrease with higher filler content and with longer fibers. Change gate locations. Double push filling method. While not always visible, weld lines (aka knit lines) are where two resin flows meet. Neat polypropylene retains nearly 90% of its strength on a properly designed and molded weld line. Venting at Weld Lines. Learn more. 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. Bad habits can cause many different problems with injection molding machines, and flow lines are included in that. If I can answer any questions you may have on optimizing the plastic part design, CNC plastic prototype, mold manufacturing, and injection molding or if I can be of any other help, please feel. injection-molding machine (Arburg allrounder 320C, Germany). Nozzles for Injection Molding Machines. 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. Weld line defects – also known as knit lines – is a defect that occurs when the injected plastic meets within a mold. Gates, vents, sliding cams, pick-out inserts, and any other place where the two sides of. 11) The part design must take into account possible knit line locations and work to direct them away from higher stress areas. 060 and 0. After selecting resin material, the design and process control of injection mold directly influence the quality of formed products. 7. Knit lines are consideredmolding defects, and occur when the mold or/and materialtemperaturesare set too low:. Crossref. As. 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. 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. Direct experience designing molds and parts for injection molding and producing the molds and parts is valuable, relevant experience for design students. 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. The data suggest that either local sample thickening or grooves form at knit line when complete section solidification takes place first at weld zone or. Solution: Increase the injection pressure or speed. The utility model relates to a mold structure capable of eliminating the appearance of weld lines of a hole-shaped injection molded product. Compression molding and injection molding are very similar, but they have one major difference. Too cool a melt. Meld and knit lines are actually both different types of weld lines. 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. Strength at the knit line can be as little as 20% of the. 1. 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. 3. Refers to portion of injection molding part that has some taper to make it easier to remove from the mold. Knit and Meld lines are inherent to plastic injection. Parts with abrupt geometry changes or holes are more prone to knit lines. Achieving a high-quality surface finish can be challenging, and other methods, such as polishing or coating, may be required. Let’s stop for a second and think about the logos we usually see on a daily basis. The runner and gate system used in plastic injection molding is responsible for directing molten plastic from the nozzle of the molding machine into the cavity of the tool. As these flow fronts come together. But we can’t talk about the injection molding process without discussing the injection molding machine. The depth of the texture or letters is somewhat limited, and extra draftInjection molding tool design and build for complex parts, with precision tooling and molding capabilities for industries demanding high-quality, critical components. 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. land and using maximum vent depths to get them as close to self-cleaning as possible. Influence of injection-molding parameters on the morphology and mechanical properties of glass fiber-reinforced polypropylene composite. สาเหตุรองของการเกิดปัญหาการเกิดประกายเงิน (silver streak) 1. Using three test materials, polystyrene (PS), polycarbonate (PC) and polyoxymethylene (POM), the relationship between a design and a processing parameter and the effects of the knit-lines on the tensile properties of injection molded plates. 020"). Knit Lines. Exploring common molding defects and. Since our material is injected through a. Vacuum. With the right nozzle, you can boost cycle. One solution is to use optimal wall thickness to help slow cooling during the ABS plastic molding process. The Injection Mold Core A mold core is any member that forms the interior of a plastic part, usually on the "B" side of the mold parting line. 040 and 0. Holes in plastic parts are normally cut with a router (or drilled if round. Moldflow is computer software that is widely used across the plastic injection molding industry to predict and optimize the injection molding process and assist with mold design. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. 0035"Weld lines:Witness line where 2 or more fronts of molten plastic converge, also called knit lines or flow lines, the weld around the holes, the line between the injection gate. 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. 2) Vents in an injection mold should let the air out, but not the liquid plastic. Because injection mold design and processing is complex, a set solution will not solve all problems. Rapid heat-and-cool molding technologies have attracted increasing. POROUS MOLD MATERIALS. 453. It explored the use of. The main types of injection molding defects are: 1. On this page you will find the online, condensed version of this guide, offering quick answers to your injection molding questions. 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 the injection molding process, melting takes place via two factors that work together: shear and heat. To account for variations in viscosity, nylon injection molding machines need to maintain an appropriate injection pressure. Depending on the design of the mold and the material being injected, a knit line may: present no problem at all, be a cosmetic issue, or cause a potentially serious structural problem. Compression-molding is also suitable for ultra-large basic. Weld lines are formed when there is an inability of two or more flow fronts to ‘knit’ or ‘weld,’ together during the molding process. For injection molding of the multi-blade fans and various rotating plastic parts, the complex of multiple gating injection molding tools were used. 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. Meld and knit lines are actually both different types of weld lines. 156 x 2 1/3 = 0. Common causes of flashing in injection moulding. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. A screw-type plunger forces the material into a heated chambe r,. Remove holes if possible. Knit lines, also known as weld lines, are fine lines that resemble hairline fractures or cracks. Inappropriate temperature. Knit Lines. The quality of the answer is directly proportional to the information we have to work with. Bubbles are caused by melting flow fronts colliding in a mold cavity. 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. 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. Knit Lines. This production method is particularly popular when manufacturing in large quantities. A component of the injection-molding machine wherein the resin pellets are melted, compressed and injected into the mold's runner system. Reduce the injection pressure. Thanks to the low air counter pressure in the cavity, this allows injection parameters to be managed in a larger window, optimizing injection time, part aesthetics and mechanical characteristics. Use the fewest number of gates possible. How to Eliminate Knit Lines In Injection Molding - Xcentric Mold Want to learn how to eliminate knit lines that form during the injection molding process? Then. Having uniform wall thicknesses between 0. Plasti-Co ® manufactures a wide range of injection molding nozzles from standard nozzle tips, extended nozzle tips, nozzle bodies, extended nozzles bodies, custom bodies, general purpose to full taper, shut-off, mixing and filtering applications. If the part design’s wall thickness is constant, the magnitude of the plastic’s velocity will be the same at every. The parting line will always be visible, but can be minimized by its location, draft allowance and part geometry. Contact us. Inadequate venting may cause short-shots, poor surface appearance, or weak weld-lines. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. Remedies: Increasing the barrel temperatures will allow the flow fronts to stay hotter longer and. Flow rate and flow speed are cut in half at every runner branch. A weld line, or knit line, occurs when two flows of melted plastic meet and “knit” together. 5. Still, they are almost always a cosmetic issue. Injection molding is capable of producing a lot of aesthetic options as well. com. Such molds or tools aren’t intended to be used in operation. 0 and Table 1). Islyn Thomas summarized the need for a particular vent location better than I ever could. Generally all plastic components should be designed with draft where possible. Weld lines or knit lines and meld lines formed when two melt fronts run into each other or join together can be improved by. This can result in cosmetic defect or a weak point in the part. Meld and knit lines are actually both different types of weld lines. 080" – 0. This type of molding uses a single tool to create both the part's geometry and surface finish in one step. Knit lines are hard to eliminate for injection molded plastic parts but designers can minimize cosmetic defects. Effect of Injection Moulding Conditions on Knit-line Formation, Plastics Rubber Processing and. 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. 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 the process of injecting liquid thermoplastic into a mold. These seams or knit lines are avoided because the molding material flow does not a meet at an interface nor must. This defect is caused from excessive lube or oily stock. Below is a list of items that should be checked both during normal molding operations and if defects are detected. Three terms that often get mixed up in injection molding are weld, meld and knit lines. Troubleshooting Injection Molding Weld Lines. 030- to 0. Also, since this part will likely be painted or chrome plated, knit lines are a concern. 040-in. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. Meld and knit lines are actually both different types of weld lines. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. And like all manufacturing industries, plastic injection molding lines are more profitable the shorter the cycle time — so long as they produce quality parts. Submarine Gates. Causes 1. Knit lines are typically much weaker. After samples have been approved, it’s time to kickoff. Gas trapping/ poor venting. An option to bluing agents, the long established means of gauging pressure distribution, comes via Pressurex, a thin, flexible, plastic film. ) or as thick as 25 mm (1 in. 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. More about the knit lines in injection molding. Using the design cube, learn how knit lines are formed on plastic parts and tips to avoid knit lines in your plastic injection molding design. Knit lines in injection molding are common defects of the molded parts. First, an injection mold with triangular inserts was built to study the influence of meeting angles on material properties at the weld line. Criens}, journal={Materials Chemistry and Physics}, year={1986}, volume={14}, pages={69-83} }A structural automotive sub frame component ( 10 ) that is formed from a sheet molding compound having carbon fibers. plastic recycling machine, blown film extruder, filament extrusion line, injection molding machine, blow molding machine, injection blow molding machine, bag making machine, flexo. Gate design is another critical piece of part function in plastic injection molding. Material. One common problem that occurs in injection molding is the formation of knit lines. That’s the air escaping out of the nozzle until the hose is full of pressurized water. Any of the above can result in “knit lines” on final products, but mold flow analysis prior to mold machining can keep these issues from cropping up at all in iteration and production. Weld Lines-3 Ways for Detecting and Correcting. Understanding types of injection molding process can help to avoid some design challenges early in the process. 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. Bead Blasting. To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. a specific area on one side lens, a warp line, and a weft line. 4. Contact Universal Plastic Mold Today. Weld line. However, the process involves forcing the material through small holes into the mold cavity. Knit lines, holes, part configuration and the talent of your molder all come into play. [8] Bevis, MJ, Reis RL, Cunha AM. Three terms that often get mixed up in injection molding are weld, meld and knit lines. Increasing injection speed. As these flow fronts come together. 003" - 0. “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. Macromol Symp 1988;21/21: 489-500. Three terms that often get mixed up are weld, meld, and knit lines. Know about the cause of these lines and the potential solutions. There is no need to worry about flow or knit lines that may appear with injection molding. Final Report-Plastic Injection Molding - Free download as Word Doc (. As the polymer resin is injected into a mold, it flows through all parts of the mold. By altering the part design, it may be possible to just have one flow front, and avoid multiple flow fronts having to come together. 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. In a plastic injection-molded component, a knit line occurs when 2 different plastic flows emerge in a mold. The GLS™ Injection Molding Guide provides in-depth information on part design, mold design and processing for styrenic block copolymer (SBC) thermoplastic elastomers (TPEs). These are imperfections in the part. When venting stationary inserts or core pins in rib or part details with venting issues, I recommend no more than 0. Let’s. It is. 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. The area generally has lower strength than the other areas of the part. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. But those key aspects can be viewed differently if you’re auditing mold changes before startup or troubleshooting changes for an already validated process. Reduction of sink can possibly be had by switching to an ABS/PC-blended material. 040-in. Notched weld lines then remain near the cavity walls. The process parameters were fixed as follows: Packing pressure of 40 MPa, injection time of 2. The mold settings can run flawlessly until employees consistently open the machine for inspections, interrupt cycle times, or cause. wall thickness, knit lines, draft. The injection molding design process, much like all industrial design processes, deals primarily with the creation, look, and feel of a product. PROBLEM: FLOWLINES (ALSO CALLED WELD LINES OR KNIT LINES) Definition: Streaks, orange skin, or visible flow lines in parts . . Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. occupied frequently with troubleshooting injection molding. Inject the molten material into a mold. Expand. 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. Sink Marks Cause 5: Improper Part Geometry. The last cause of flow lines may be the operators running your daily operations. Sink Marks Cause 3: Improper Pack or Hold Pressure. Therefore various injection molding defects can be eliminated. excessive or premature wear at the parting line. Three terms that often get mixed up are weld, meld, and knit lines. Learn how to troubleshoot weld lines in injection molding. Obstructions in the part create weld lines or knit lines during injection molding. , Rallis, A. To avoid walls that are too fat or too thin, designing a wall thickness between 0. Different plastics make different types of knit lines. Increase the injection speed. As a result, prototyping is strongly recommended for parts with. Degassing – Degassing is the simple operation of opening and closing an injection mold to allow any trapped air (or gas) to escape. A knit line is the spot where two flows meet. When assessing issues with injection molded parts, we want to make sure some core aspects of molding are checked. Two major sources of weld lines are multiple gating and flow around pins. 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. ABS. 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. Knit line / Meld. Using abrasives in a pressurized air blast to create a surface texture on the part. The injection molding was carried out in a DK-Codim 175/410 injection molding machine. 4. Molding analysis study: An example of the low patterns and knit (weld) lines formation (MoldFlow® data) of injection molded round plastic part with a complex shape and with a ring. thick. Knit lines. The company provides an array of digital manufacturing expertise. Obstructions in the part create weld lines or knit lines during injection molding. Computer simulation packages of injection molding have had success in predicting filling behavior in extremely complicated geometries, capable of predicting weld lines’ location exactly. The gate is the entry point to the part-forming cavity, where plastic material is injected from the molding machine barrel, through the sprue and runner, into the mold. 140 in. injection molding. This makes the casting process as efficient and accurate as possible. , LTD. This will help the mold designer to determine the allowable gate and knit line locations. It is important when selecting an injection molder that the right process conditions are used to reduce or eliminate the effects of. When injection molding complex parts, often knit-lines are formed during the mold filling stage. Learn how HPP maximizes these specialized processes. Weld lines typically appear in a part when an obstruction of some kind separates the melt flow and prevents it from "knitting" together. Industrial Knitting Machines. opposed to two or more gates. An injection mold that produces pieces while the final tool is being built. Anisotropy. 040-in. Weld lines are a common imperfection to be found in most plastic injected molded parts. Sink Marks Cause 4: High Mold Temperature. Poor venting. The knit line itself (the vertical line in the middle) is visible in this lighting, but the biggest issue is with the texture. Possible causes: Low temperature or fluidity of melted plastic during injection molding. Be wary of saving too much weight or you might end up with: cracking. As. TEFABLOC™ TESI 744 TPE compound for injection molding processing provides superior adhesion properties when processed using injection molding.