In a plastic injection-molded component, a knit line occurs when 2 different plastic flows emerge in a mold. Plastic injection molding has long been an affordable and efficient process for producing custom prototypes and end-use production parts. Knit lines are hard to eliminate for injection molded plastic parts but designers can minimize cosmetic defects. The plastic melt that passes through the gate at high speed directly enters the cavity, then contacts the surface of the cavity to solidify, and then is pushed by the subsequent plastic melt, leaving traces of meandering. What is copper electrode in injection mold? hashtag#plasticinjectionmold hashtag#moldmaking "Copper electrode," also known as "electrode," is a common component in mold manufacturing. Disadvantage: May rust if improperly stored. 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. 3. The comment on melt flow index is correct, but, I've molded straight PC down to . It’s also relatively inexpensive. The recommended minimum production volume for injection molding is 500 units. Enlarge gas vents and gates to allow trapped air to escape the mold. ISSUE FACED BY THE INJECTION MOLDING COMPANIES: FLOWLINES (ALSO CALLED WELD LINES OR KNIT LINES) Definition: Streaks, orange skin, or visible flow lines in parts. Which affect parts aesthetics and decrease parts strength. Nicolet Plastics LLC. Refers to portion of injection molding part that has some taper to make it easier to remove from the mold. Hardware components. ABS is a good choice for handheld consumer devices. Other common issues associated with thin walls include uneven cooling, warp, cracks, cosmetic texture inconsistencies, and weak knit lines or fracture points. be impressed by improvements of bubbles (vacuum voids), short shots, unequal thickness, jetting marks, weld lines, knit lines, black streaks, strain 2. Weld/Meld/Knit lines are all terms describing the effect of two or more flow fronts of material joining or meeting together in the part. 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. In the 1947 book, Injection Molding of Plastics, the late Dr. Weld Lines-3 Ways for Detecting and Correcting. When the temperature is not very high, there are chances of premature solidification, which can cause weld lines to form. occupied frequently with troubleshooting injection molding. Main causes of knit lines in injection molding: 1. It allows our molders to monitor fill pressure, cosmetic concerns, and the basic quality of the parts. reduction on the side the part is folding towards. To prevent swirling, perform tests whenever possible and use pre-compounded resin to ensure identical color match across parts. Reducing the size and depth of depressions helps minimize the impact of knit lines. After selecting resin material, the design and process control of injection mold directly influence the quality of formed products. In fact, knit line strength will decrease with higher filler content and with longer fibers. Mold venting should be checked and increased if necessary, injection molding service. If you want to better understand the process of injection molding, there are a few critical terms you need to know. Compression molding can also support large part sizes, and it has a tendency to. The packing pins are sequentially. 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. In this phenomenon, some portions of the mold cavity are filling, while others undergo over. Reduce the injection pressure. Exploring common molding defects and. Plasti-Co ® manufactures a wide range of injection molding nozzles from standard nozzle tips, extended nozzle tips, nozzle bodies, extended nozzles. These lines occurs usually around holes or obstructions and cause locally weak areas in the molded part. In injection molding, it is often important to maintain consistent color throughout the part. Vertical Plastic Injection Molding. Weld lines, also called knit lines, are a defect that occurs with molded parts caused by two different flows of plastic resin that do not adequately join together or weld together correctly during injection molding. . To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. When designing for injection molding, consider these steps to prevent knit lines Resin cools as it is injected into a mold. Direct experience designing molds and parts for injection molding and producing the molds and parts is valuable, relevant experience for design students. Lower the melt and mold temperature to prevent overheating. Contact Universal Plastic Mold Today. Prevent Flow and Knit Lines During the Injection Molding Process. Table 2. This information is intended to be used only as a guideline for designers and processors of modified thermoplastics for injection molding. All the while, the material could be the correct material," Hill says. 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. Depending on the resin, resin temperature, mold temperature, and filling. First, they carry resin to the mold via a runner. AS9100:2016. What Are Cosmetic Standards for Plastic Parts?. 060 in. Injection molding is a popular manufacturing process used to fabricate parts in large volumes. When injection molding a part, a knit. Wall Thickness: The recommended wall thickness for injection molded POM parts is between 0. , Rallis, A. 4. Three terms that often get mixed up in injection molding are weld, meld and knit lines. While injection molding itself is a straightforward process involving melting. So. Slower injection provides less orientation and stress. Injection speed and pressure. 4. , 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. If the plastic has cooled too. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. For instance, three widely used processes are insert molding, overmolding, and undercuts. These lines occur usually around holes or obstructions and cause locally weak areas in the molded part. The injection molding design process, much like all industrial design processes, deals primarily with the creation, look, and feel of a product. Without it, air and gas are trapped in the mold, which compress and heat as the cavity fills. Using three test materials, polystyrene (PS), polycarbonate (PC) and polyoxymethylene (POM), the relationship between a design and a processing parameter. It is best practice to maintain a uniform thickness throughout an injection-molded part. Pitfall #1 – Knit Lines. As the melted plastic fills the mold, there are locations where the molten plastic flow stream separates and then comes back together. POROUS MOLD MATERIALS. Generally, the mold structure is roughly divided into two main parts: fixed half and moving half. In addition, the force of the gas holds the appearance side of the part in contact with. Once the mold is created and the machine is set up, additional parts can be manufactured very fast and at a very low cost. The point of meeting creates a weak spot because the edges of the molten plastic, already cooling, don’t mix together very well. Users will be able to use in-cavity pressure or temperature sensors to control when the valves open or close. One of the most important aspects of hot runner system design is the gate location, which is the point where the molten plastic enters the cavity. Here are some of the most common cosmetic defects and how to avoid or fix them. Injection molding a red component, for example, can pose a challenge because at time the component may be too thin for the pigment itself!. In this paper, a general and efficient approach was proposed for dual-scale infiltration flow balancing based on numerical simulation. 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. Weld lines typically appear in a part when an obstruction of some kind separates the melt flow and prevents it from "knitting" together. When injection molding complex parts, often knit-lines are formed during the mold filling stage. When injection molding a part, a knit line may present no problem, or can cause a serious structural problem. Weld lines defects are formed when two flow fronts are merged together. [8] Bevis, MJ, Reis RL, Cunha AM. Product designers encounter a wide range of challenges when creating and developing molded parts, such as stress factors, warp, and those pesky knit lines. Solution: Increase the injection pressure or speed. Kim, who has worked for hot runner system and auxiliary equipment supplier Yudo-Abiman for 12 years, most recently as. 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. Advantages for your Injection Molding Machine:. Contact us. Shorten the mold cycle time so that any trapped air and resin don’t have a chance to overheat. placed usually in the areas last to fill, near knit lines, as well as on the runner system. The Bottom Line You might have come across the aforementioned terminology before and did not know what any of the words meant. ” Depending on the material you use, the knit lines could be invisible or obvious—work with an injection molding company to figure out. These knit-lines are well-known as particularly critical regions in the mold when mechanically loaded. The Demo Mold helps those new to injection molding easily visualize the process and is a great teaching device for educators. C. TRADITIONAL MACHINES VENTS. 015in wall. H-13 Good general purpose tool steel. The goal is to create a uniform thickness and at the smallest (thinnest) level required. 025 inches per inch, depending on the particular resin, molding conditions, part design, part wall thickness, and direction of flow. suppressed cooling and possibly warp. and Titomanlio, G. Because injection mold design and processing is complex, a set solution will not solve all problems. Learn how material selection, part design, and optimizing process parameters can help eliminate knit lines. In a plastic injection-molded component, a knit line occurs when 2 different plastic flows emerge in a mold. Increase the injection speed. Plating and painting applications usually require slower fill rates to keep orientation low. This design aid shows the mechanics of how the A-side and B-side of a tool work together during the injection molding process to create plastic parts. He is currently a tooling manager for a large, multi-plant molding and manufacturing company. Find out more by calling 573-437-4154 today or email us. PCS Company, Fraser, Michigan, has launched the Polimold Valve Gate Sequencer, providing injection molders with more precise control of the mold-filling sequence when using valve-gate hot runner systems. The knit line itself (the vertical line in the middle) is visible in this lighting, but the biggest issue is with the texture. Demo Mold. To account for variations in viscosity, nylon injection molding machines need to maintain an appropriate injection pressure. In layman’s terms, injection molding boils down to four simple steps: Melt material. Three terms that often get mixed up in injection molding are weld, meld and knit lines. This can dramatically reduce the effects of material changes, according to the injection molding technology company. Remedies: Raise the temperature of the mold or molten plastic. Weld lines are formed when there is an inability of two or more flow fronts to ‘knit’ or ‘weld,’ together during the molding process. Gate size can be increased or moved to a section with greater wall thickness to help eliminate. 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. Increase the injection speed. The weld line can either be a minor cosmetic issue. They again get resolidified along the surface. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. When the plastic cools, it takes the shape of the mold and is then ejected and finished. The Difference Between Knit and Meld Lines–and Why It Matters. Here are some of the most common cosmetic defects and how to avoid or fix them. It has low shrink and high dimensional stability, and it has good resistance to acids and bases. such as knit lines and other imperfections. 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. Solution: Increase the injection pressure or speed. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. Anisotropy. BACK TAPER – Reverse draft used in mold to prevent molded articles from drawing freely. The melt is forced to split up during filling of the cavity. These flaws can affect the aesthetic and structural integrity of the. S. 5 : 1 and a L/D (length toMold flow analysis is a software simulation which show how the resin fill in the mold in injection molding process. Gating. Weld or knit lines occur when melt flow fronts collide in a mold cavity. 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. These knit-lines are well-known as particularly critical regions in the mold when mechanically loaded. Complex parts can be reproduced with low cost once mold is manufactured. Meld and knit lines are actually both different types of weld lines. Injection speed and pressure. Weld-line strength for plastics can vary from 20% to nearly 100% of the strength of the plastic itself. The Goldilocks principle applied to wall thickness. Meld and knit lines are actually both different types of weld lines. Injection Molding: How to Set Second. The chart below shows recommended wall thicknesses for common injection molding resins. An option to bluing agents, the long established means of gauging pressure distribution, comes via Pressurex, a thin, flexible, plastic film. When designing for injection molding, consider these steps to prevent knit lines The Resin Cooling Process. 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. Three terms that often get mixed up in injection molding are weld, meld and knit lines. Table 2 lists the<br /> properties of common tool steels and the typical mold components for which they are<br /> used. Runner and gates must be balanced. 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. It is typically used for thermoset materials, but can be used with thermoplastics. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. Incorrectly placed single gates may cause knit lines. (1. 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. Draft. (1. Introduction to Knit Line Injection Molding Knit Line Injection Molding is a process that allows manufacturers to produce parts more quickly, accurately, and at less cost than traditional injection molding. TEFABLOC™ TOSI 431 75A is a high-flow thermoplastic elastomer (TPE) designed for large-part injection molding applications, offering exceptional flexibility and weather resistance. As the polymer resin is injected into a mold, it flows through all parts of the mold. • Estimated clamp tonnage of 5. 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. Nicolet Plastics LLC. Injection mold design and custom tooling can make or break the success of a finished plastic product. 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. 1-3). Specifically, Stokes and. There are times when porous materials like Porcerax are used in problem or backfill areas. MINNESOTA. These structures are often small surfaces of about a tenth of an inch in diameter. More about the knit lines in injection molding. With over 50 years of experience, Universal Plastic Mold can help you avoid (or at least minimize) knit lines in your molded parts. Injection moulding (U. The packing pins are similar in construction to mold ejector pins and may also be mold ejector pins depending on mold configuration. Weld line. For non-reinforced or non-filled nylon, the mechanical performance in the knit lines (planes) areas are approximately equal to the mechanical performance of the resin (polyamide) used. After selecting the direction in which the mold hole will be cut, it is much simpler to locate the separating line. Corrosion resistance. injection molding machines using standard industry practices . As a result, the portion has a faint, perhaps undetectable line. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. 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. Dimensional stability. Trapped gas is one of the most common causes of part burns, and it can also lead to short shots and voids, blemishes and discernible knit lines that weaken the part. Knit Lines: Holes in the part will always cause knit lines. Back to News Page. 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. 453. You don't give us much to go on. [1]Weld Lines. Long shapes are produced without multiple drops or hot runner systems, eliminating knit lines and lowering tooling costs. H-13 Good general purpose tool steel. 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. Plastic injection molding is the industry’s most common way to manufacture parts. They need the interference of about 0. Looking to Your Knit Lines with Molding. Monoform parts. As melt temperature, viscosity and abrasiveness rise, tool life will decline. extend the time between mold maintenance shutdowns. The most common and one of the most challenging injection molding defects are weld and knit lines. Flow lines typically manifest as visible marks, often slightly. A weld line can also be called a knit line. Valve gates are most efficiently. The injection molding process offers a vast array of plastic resins to work with. It is also where a slide mechanism might meet where it shuts off on one of the mold halves. Those are knit lines, formed when two opposing flows of material join together in the mold cavity. Notched weld lines then remain near the cavity walls. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary from virtually invisible to something that looks like cracks in the plastic. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. Step 1: The injection of molten plastic into the injection mold from Barrel A. 18/06/2021. Effect of Injection Moulding Conditions on Knit-line Formation, Plastics Rubber Processing and. In situ injection molding of continuous fiber reinforced thermoplastic composites is challenged by unbalanced dual-scale infiltration flow due to the pronounced capillary effect. To avoid walls that are too fat or too thin, designing a wall thickness between 0. Brent Strong, p. txt) or view presentation slides online. When designing for injection molding, consider these steps to prevent knit lines The Resin Cooling Process. Molding Troubleshooting Guide Bond Readout Bond readout is a surface distortion similar to a hump or sink that occurs over a bond line Probable Cause Material Process • Mismatch of compliance between outer panel, inner panel and adhesive • Incompatible thermal expansion coefficients between the SM and the adhesiveIt tells them that you visualized how injection molded parts cool and harden. Shear Controlled Orientation Injection Molding of Polymeric Composites with Enhanced Properties. While injection molding dies are expensive to produce, each die canHowever, they can also create weld lines or knit lines in the part where the flow fronts meet. While this process is largely efficient and reliable, it's not without its potential issues. They again get resolidified along the surface. Molding Troubleshooting Guide Bond Readout Bond readout is a surface distortion similar to a hump or sink that occurs over a bond line Probable Cause Material Process • Mismatch of compliance between outer panel, inner panel and adhesive • Incompatible thermal expansion coefficients between the SM and the adhesiveMolding Troubleshooting Guide Bond Readout Bond readout is a surface distortion similar to a hump or sink that occurs over a bond line Probable Cause Material Process • Mismatch of compliance between outer panel, inner panel and adhesive • Incompatible thermal expansion coefficients between the SM and the adhesiveMost failures of injection molded plastic parts are caused by either improper design of the part or improper design of the mold. Knit lines are formed in injection moulding when two flow fronts meet in the middle of a part (a line where two sides of the plastic are “knit” together). Computer simulation packages of injection molding have had success in predicting filling behavior in extremely complicated geometries, capable of predicting weld lines’ location exactly. 2. 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. This continues until the weld lines in plastic injection molding disappear. In the 1947 book, Injection Molding of Plastics, the late Dr. For injection molding of the multi-blade fans and various rotating plastic parts, the complex of multiple gating injection molding tools were used. Use the fewest number of gates possible. Typical Tool Steel for Injection Mold Construction Steel Type Steel Properties Mold Component P-20 Pre-hardened, machines well, high carbon, general-purpose steel. Having a basic understanding of the injection molding process will aid in understanding how to design for injection molding as well as how to forecast production schedules. Legend: a-in. Knit line Knit line Start of mold filling. Most failures occur at what are called “weld lines” or “knit lines”. Reduce. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic. The relationship between processing conditions, morphological structure and mechanical properties of knit lines of an injection molded semi-crystalline thermoplastic. Considerations: ABS-molded parts will show knit lines and can have sink and voids in thick areas. Reducing the dimensions of the runner system. Vacuum. Knit lines, also known as weld lines are areas in the. It recently obtained a $4. In injection molding terms, these are called “living hinges” and are made right into the design instead of adding them later. Learn Injection Molding Glossary with Plastopia: Using actual molded parts (with images) as examples. 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. Reduce clamping force. The utility model relates to a mold structure capable of eliminating the appearance of weld lines of a hole-shaped injection molded product. In the plastic injection molding industry, we work with materials that are byproducts of oil refinement and molds made of metal casting, so our terminology is bound to be at least slightly confusing. Sequential valve gate technology. Ductile Injection Molding 101 - Injection Molding Varying. "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. Knit / Weld Lines. We wanted to independently assess how a mold would fill and where knit lines would be, instead ofKnit Lines. Mold Venting. It’s our responsibility to make sure your design comes out of the mold working properly. Timing and temperature are significant contributing factors when it comes to flow and knit line defects. These defects are not visible, like small. Knit lines, holes, part configuration and the talent of your molder all come into play. Redesign the mold: Redesigning the mold to. The injection molding process uses a granular plastic that is grav ity fed from a hopper. Inappropriate temperature. Material contamination, for example, can cause several molding issues. Look for signs of stickiness or burning. RELATED CONTENT. 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. Mold venting is critical to the quality and consistency of the finished part. Gates that are too small can also cause the uneven flow of material or result in knit lines, blemishes that occur where two resin flows meet. 140 in. 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. Services Group. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. Mold bases, ejector plates, and some cavities (if nickel or chrome plated to prevent rust). TRADITIONAL MACHINES VENTS. Starting with small part size, students learned to think about detailing on a product at thisTable 2. An undercut is any indentation or protrusion that prohibits an ejection of a part from a one-piece mold. Not always a problem, but can cause serious structural issues. 3 To get the most out of your Xometry Injection Molding experience, we offer the following part Design Guide with. Facebook. A screw-type plunger forces the material into a heated chambe r,. Knit lines form when two or more plastic flow fronts collide and solidify or “knit” during the molding process. Depends how hard you want to push it. Injection molding can be a real challenge if you don’t follow the “Five M’s”: Man, Mold, Machine, Material and Method. Remove holes if possible. How weld lines form. Three terms that often get mixed up are weld, meld, and knit lines. The advantages of compression molding include more isotropic fiber distribution, dimensional stability, and surface finish. Possible causes: Low temperature or fluidity of melted plastic during injection molding. pdf), Text File (. Knit lines, also known as weld lines are areas in the molded part where two or more flow fronts converge. Example of a gate location in a finished part Example of knit lines in a finished part. The specific method is that when the product is just filled and filled in the cavity, the insert is used to cut the soft material melt in. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. 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. 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. In this, work, metal inserts were joined with polyamide 6 by using the injection-molding technique. This month, we covered an array of topics including injection mold venting, business strategies and runnerless micro molds. Our Injection Molding Capabilities • Horizontal Injection Molding up to 3300 TONS • Structural Foam Molding + Structural Web • 1oz to 600oz part capacity. Knit Line – A molding defect resembling a flow-line found at the point where the rubber meets between the injections. Given the cosmetic requirements, there is a good chance the mold would require. The injection molding process uses a granular plastic that is gravity fed from a hopper. A knit line is what happens when plastic flows coming from two different directions meet inside of the mold and solidify. 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. S. Injection molding is min-maxed for mass production. 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. Once the mold is created and the machine is set up, additional parts can be manufactured very fast and at a very low cost. This is why the leading edge of the resin flow within a. Changing the. Weld lines: Also known as knit lines, these are molding defects that occur when two flow fronts meet without the ability to “weld. Rynite® PET is usually processed with melt temperatures between 280 to 285 °C (535 to 545 °F) . Mold Venting. Typically, injection molded parts will be between 0. , 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. Reduce the injection speed to limit the risk of trapping air inside the mold. The example. Inadequate injection pressure can result in knit lines and a surface that appears corrugated. Gate locations can be directly behind or on the edge of the graphic. To learn more about us or to get a quote, click here or call 1-888-893-1587 now. 030 and 0. Injection molding can be a real challenge if you don’t follow the “Five M’s”: Man, Mold, Machine, Material and Method. ITAR. Weld-lines or knit-lines are formed during the mold filling process when the split melt flow fronts meet at the same downstream location. These materials have beenThe wall thicknesses of an injection molded part generally range from 2mm – 4mm (0. 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. 11) The part design must take into account possible knit line locations and work to direct them away from higher stress areas. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. A plastic product formed by the injection mold is divided into two parts, and the line separating the product is called the parting line. But any. We have two unique offers to meet your needs wherever you are in the product lifecycle. Knit Lines. Learn more. Our glossary of terms provides definitions for a wide range of injection molding terms. The quality of the answer is directly proportional to the information we have to work with. 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. ; Wood, Philip E. Molding parts with multiple gates will almost certainly produce a weld line at right-angles to the line joining the two gates which could cause the weld lines to be exceptionally weak (see Figure 1. Core out parts to eliminate thick walls. ABS. TEXAS. From the start of your project, you can count on The Toolroom to exceed your expectations for all of your plastic injection molding needs. Bubbles are caused by melting flow fronts colliding in a mold cavity.