5 to 3. It explored the use of. A knit line is what happens when plastic flows coming from two different directions meet inside of the mold and solidify. menu. Quotes for 25+ Manufacturing Processes. 11) The part design must take into account possible knit line locations and work to direct them away from higher stress areas. injection molding. Steven. Three terms that often get mixed up are weld, meld, and knit lines. Mold vents should function the same way. 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. Avoid areas where the plastic must suddenly flow upward or downward. Injection Molding Problems and Solutions (17/17) – Weld or Knit Lines Sep 27, 2022 Injection Molding Problems and Solutions (16/17) – Warpage Sep 15, 2022. Plastic injection force exceeding the clamping pressure of the press. Knit lines, also called parting lines, are any lines where two resin flows meet and may or may not be visible. 030- to 0. 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. Multiple gates will always cause knit lines. 160"). Three terms that often get mixed up are weld, meld, and knit lines. Find out more by calling 573-437-4154 today or email us. When injection molding complex parts, often knit-lines are formed during the mold filling stage. Solution: People. With over 50 years of experience, Universal Plastic Mold can help you avoid (or at least minimize) knit lines in your molded parts. Gates, vents, sliding cams, pick-out inserts, and any other place where the two sides of. such as knit lines and other imperfections. 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. Randy Kerkstra has been in the plastics industry for more than 26 years, occupied. 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). RELATED CONTENT. Without adequate support pillars, flashing of the parting line faces and bowing of the plates may occur. Knit and Meld lines are inherent to plastic injection. It’s also relatively inexpensive. There is no need to worry about flow or knit lines that may appear with injection molding. The difference between a knit and meld line is significant, dramatically impacting the part’s structural integrity. Once the mold is created and the machine is set up, additional parts can be manufactured very fast and at a very low cost. 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. Getting started; Knit Line Injection Molding; Knit Line Injection Molding - China Manufacturers, Factory, Suppliers. 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. Knit / Weld Lines. To prevent swirling, perform tests whenever possible and use pre-compounded resin to ensure identical color match across parts. In a weld line, reinforcement fibers. This defect is caused from excessive lube or oily stock. 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. Move the injection unit away from the mold during short breaks . Highly ScalableVacuum on the mold does help and many times eliminates the weld line. In compression molding, molds are closed around the charge, and in injection molding, the charge is injected into a closed mold cavity. Anisotropy. They again get resolidified along the surface. Download : Download full-size image; 3. Typical Tool Steel for Injection Mold Construction Steel Type Steel Properties Mold Component P-20 Pre-hardened, machines well, high carbon, general-purpose steel. 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. Soft metals, such as aluminum and beryllium copper, can be used for prototype<br />. Plastic injection molding has long been an affordable and efficient process for producing custom prototypes and end-use production parts. weak knit lines and fracture points. On this page you will find the online, condensed version of this guide, offering quick answers to your injection molding questions. Expand. Wavy lines are another feature of weld lines. Bubbles are caused by melting flow fronts colliding in a mold cavity. 203 in. Steven. Minimizing or eliminating flow and knit lines is an additional benefit of using this material. Designers are able to specify seamless design features with compression molding. Brent Strong, p. Melt temperature does. Description: Flow lines are streaks, patterns, or lines - commonly off-toned in color - that show up on the prototype part as a consequence of the physical path and cooling profile of the molten plastic as it flows into the injection mold tooling cavity. Contact Us. They are formed downstream through holes, and between multiple gate locations. Using three test materials, polystyrene (PS), polycarbonate (PC) and polyoxymethylene (POM), the relationship between a design and a processing parameter. In the 1947 book, Injection Molding of Plastics, the late Dr. Edge gates, which can include fan and tab-shaped gates, are the most common ways to gate a tool. Increase size of the vents. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. Design bosses with an outer diameter equal 2x the nominal diameter of the screw or insert. 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. Mold venting is critical to the quality and consistency of the finished part. 120 in. Knit Lines: These occur when different flow fronts come together as plastic flows through the part cavities. Circular Loom Machine; Raschel Knitting Machines; Shade Net Making Machinery; Inspection Machines; Non Woven Production Line. Product designers encounter a wide range of challenges when. They are formed when two or more flow frontINJECTION MOLDING GUIDE V2. Knit lines and other aesthetic characteristics of the part are strictly related to the plastic’s temperature during molding, so efficient filling time is essential for achieving proper welding lines and quality parts. Knit Lines. S. . Meld and knit lines are actually both different types of weld lines. 060 and 0. Knit lines, also known as weld lines are areas in the. Weld / Knit Lines; Assumptions. Refers to portion of injection molding part that has some taper to make it easier to remove from the mold. Example of a gate location in a finished part Example of knit lines in a finished part. Undercuts add cost to tooling and molding, which is recommended to eliminate or minimize as possible. injection molding. The mold settings can run flawlessly until employees consistently open the machine for inspections, interrupt cycle times, or cause temperature. Weld lines may appear like seams or scratches, but that is not what they are. Near-Net-Shape Molding enables us to eliminate knit lines, add undercuts, increase options for geometry and tolerances, and reduce tooling cost for low. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. These knit-lines are well-known as particularly critical regions in the mold when mechanically loaded. A poor design can lead to many visual defects in the final part. The plastics used by injection molding processes are relatively cheap and can be used to achieve a wide variety of properties, so injection molding is popular for creating many packaging and consumer products, like LEGO! A weld line (weld point, flow line or a knit line) forms when separate melt fronts travelling in opposite directions meet. Bad habits can cause many different problems with injection molding machines, and flow lines are included in that. The best we can hope for is to pressurize the knit or meld line better through the combination of melt temperature, mold temperature, flow rates, and holding pressures. This is easier to accomplish on. Plastic injection molding has long been an affordable and efficient process for producing custom prototypes and end-use production parts. A weld line can also be called a knit line. This information is intended to be used only as a guideline for designers and processors of modified thermoplastics for injection molding. matte or smooth texture on the part’s surface gives a more desirable aesthetic and hides small imperfections such as knit lines, flow lines, shadow marks, and sink marks that were caused by the mold. Thick sections take longer to cool than thin ones. 6. It can also aid in material selection since fill. – Change the thickness of the product. Below is a list of items that should be checked both during normal molding operations and if defects are detected. Runner and gates must be balanced. Knit Line – A molding defect resembling a flow-line found at the point where the rubber meets between the injections. The process involves feeding the material into a press, where it is cooled or heated as per. Additionally. (See Fig. Increase the injection speed. The resulting line has the. 2. Bubbles are caused by melting flow fronts colliding in a mold cavity. 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. 040-in. (1987). The influence of knit-lines on the tensile properties of injection molded parts. 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. Depending on the design of the mold and the material being injected, a knit line may: present no problem at all,. You can avoid knit lines and other problems by creating designs with smooth geometries. 1 in. S. Knit Mark – A witness mark on a molded part, often occurring at the midpoint between two transfer or injection sprue locations. As a result, molten plastic takes the injection mold core and cavity shape. Influence of injection-molding parameters on the morphology and mechanical properties of glass fiber-reinforced polypropylene composite. Part Design Summary Bosses:Welds and/or Knit lines can be defined as the inability of two or more flow fronts to “knit” together, or "weld", during the molding process. 120 in. 003" - 0. In addition, the force of the gas holds the appearance side of the part in contact with. 2. Knit lines. 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. The point I am making here is, if you’re injecting 14. 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. Increase the melt and/or mold temperature. Injection molding is an efficient, often cost-effective way to manufacture custom plastics that are strong, durable, and long-lasting. ICOMold is a plastic injection molding company that manufactures plastic injection molded parts. 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. Excessive mould lubricant. Part Shorts No burn marks. To avoid walls that are too fat or too thin, designing a wall thickness between 0. When assessing issues with injection molded parts, we want to make sure some core aspects of molding are checked. Legend: a-in. Achieving a high-quality surface finish can be challenging, and other methods, such as polishing or coating, may be required. First of all, ABS is prone to knit lines — or the places where two flows of plastic resin meet during the manufacturing process. These are imperfections in the part. They occur when two resin flows meet at different. However, compression molding often provides poor product consistency and difficulty in controlling flashing, and it is not suitable for some types of parts. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. The injection of molding compound into the parts through one or two gates may produce parts that have knit lines. In the injection molding process, melting takes place via two factors that work together: shear and heat. Randy Kerkstra has been in the plastics industry for over 26 years, occupied frequently with troubleshooting injection molding. Knit Lines and Resins A knit line is any line, visible or not, where two resin flows meet (see Figure 2). Disadvantage: May rust if improperly stored. Strength at the knit line can be as little as 20% of the. Learn how to troubleshoot weld lines in 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. Obstructions in the part create weld lines or knit lines during injection molding. In the process of injection molding, when the wall thickness of the product is large, the cooling speed of the outer surface is faster than that of the central part. TWIM=Thin Wall Injection Molding; TSL=Toys,Sports and Leisure; NB=No Break; IMR=Inter Material Replacement. Swirling can increase depending on the material you use, and the texture or polish of injection molding tools. The knit line is generally opposite the gate in thermoset. Knit lines are consideredmolding defects, and occur when the mold or/and materialtemperaturesare set too low:. Another name given to weld lines is meld line. There are times when porous materials like Porcerax are used in problem or backfill areas. He is currently a tooling manager for a large, multi-plant molding and manufacturing company. A thermoset injection molding process may save as much as 50% of machine time per shot with a faster cycle time compared to a thermoset compression molding process, allowing molders to produce high quantities of thermoset components per day in multi-cavity tools. Knit lines. Operating Conditions • Fast injection fill speeds, supporting short injection times (1–3 s), especially in thin sectionsGate and Knit Line Locations<br />. 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. 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. ”. a knit line will form 180°on the opposite side from the gate location. 827 Holes and Bosses. 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. In the present work, the micro specimens were investigated. Effect of Injection Moulding Conditions on Knit-line Formation, Plastics Rubber Processing and. All injection molding ultimately comes down to the “Man, Mold, Machine, Material and Method. excessive or premature wear at the parting line. 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. Considerations: ABS-molded parts will show. It is also one of the most important weapons in a molder’s arsenal for making process changes. 0 mm) is crucial to ensuring that parts cool evenly. POROUS MOLD MATERIALS. Fewer knit lines. A poor knit line can cause only cosmetic blemishes or it can significantly weaken the structural integrity of a part. They occur when melt flow fronts collide in a mold cavity. On the other end of the scale, a desktop injection molding machine with 5 tons of force can cost between $30,000-50,000. A thermoplastic resin is heated to its melting point and injected into the cavity of an injection mold to produce a specific part geometry. Final Report-Plastic Injection Molding - Free download as Word Doc (. These seams or knit lines are avoided because the molding material flow does not a meet at an interface nor must. Very high quality and an extreme fit may. S. Knit lines form when two or more plastic flow fronts collide and solidify or “knit” during the molding process. 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. 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-line strength for plastics can vary from 20% to nearly 100% of the strength of the plastic itself. weld line in injection molding. To ensure quality parts, injection molding companies must have the best injection mold design first + (91) 96067-70777 +(971) 547-161-112. Double push filling method. 27-ounce shot size to 600-ton with a 105-ounce shot size. The part is cooled in the mold until it is solid enough to be ejected. Plastics Injection Molding Expert John Bozzelli covers. 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. Here is a look at the. com. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Material contamination, for example, can cause several molding issues. Once the plastic cools, the mold is removed, and the object is ready for post-processing. While this process is largely efficient and reliable, it's not without its potential issues. Because they can be shut off independently you can control flow fronts and knit-line locations. Learn more about the process by reading this white paper. We then. Knit line / Meld line / Transfer line Discoloured line where two flow fronts meet Mould or material temperatures set too low (the material is cold when they meet, so they don't bond). Alter the mold design. Knit lines don’t. Weld lines typically appear in a part when an obstruction of some kind separates the melt flow and prevents it from "knitting" together. The main causes of Weld Line or Knit lines are: Convergence of two flowing polymer melt streams during injection molding process: This is the most common cause of weld lines, as the two melt streams coming from different runners or gates in the mold meet and do not fully mix, creating a weak point in the finished product. This is why the leading edge of the resin flow within a mold is always the coolest area of the resin, and, therefore, the closest to solidifying. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. Weld line. Gate design is another critical piece of part function in plastic injection molding. Increase injection speed and pressure: Faster-moving materials will meet more quickly so one doesn’t cool too soon. So. 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. A good injection mold design will take all of these factors into consideration, ensuring that the final product looks great. Weak weld lines are perhaps the most common and difficult injection molding defect to eliminate. Kaminski, in Specialized Molding Techniques,. These lines can manifest as visible marks on the component’s surface and potentially affect its structural integrity. These seams or knit lines are avoided because the molding material flow does not a meet at an interface nor must. 0mm) throughout will ensure that the parts cool evenly and will prevent warping. Potential Knit Lines • Knit lines occur where to or mold melt fronts come together-Holes, slots, multiple gates, variations in wall thickness-Meld lines occur when the melt comes together in the same flow direction • Knit lines are areas of weakness and should be located in low stress areas . 5 mm (0. Near-Net-Shape production uses injection molding to account for 70-90% of the final geometry of a part. Weld lines are a common imperfection to be found in most plastic injected molded parts. The injection molding was carried out in a DK-Codim 175/410 injection molding machine. The effect of holding variables and of injection and mould temperature was explored. The structural stability of. 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. With over 50 years of experience, Universal Plastic Mold can help you avoid (or at least minimize) knit lines in your molded parts. 156 x 2 1/3 = 0. 3 /sec. Weld lines are formed when there is an inability of two or more flow fronts to ‘knit’ or ‘weld,’ together during the molding process. Knit line strength is improved since. Plastic Injection Molding Part Design Guidelines, Plastic part Design Guidance, Parting Line Draft Undercuts Wall Thickness & Uniformity Bosses Gussets and Ribs Radii and Corners Material Shrinkage Gating Ventings Knit/Weld Lines. Last month, in the first part of this two-part installment we focused on the reasons viscosity can change during injection molding. 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. Polym Compos 1982; 3: 88–96. Resin cools as it is injected into a mold. Mold bases, ejector plates, and some cavities (if nickel or chrome plated to prevent rust). Reduction of sink can possibly be had by switching to an ABS/PC-blended material. (Overpacking. The utility model relates to a mold structure capable of eliminating the appearance of weld lines of a hole-shaped injection molded product. Orientation of these knit (weld) lines, are perpendicular to the tensile stresses, applied to the ring (Figure 6-8). POROUS MOLD MATERIALS. There are times when porous materials like Porcerax are used in problem or backfill areas. Product designers encounter a wide range of challenges when creating and developing molded parts, such as stress factors, warp, and those pesky knit lines. 080" – 0. The packing pins are sequentially. Design. land and using maximum vent depths to get them as close to self-cleaning as possible. 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. Flow Lines. This can enable the manufacturer to increase the molten plastic temperature at the front of each flow and avoid the occurrence of weld lines. In a plastic injection-molded component, a knit line occurs when 2 different plastic flows emerge in a mold. Submarine Gates. While injection molding itself is a straightforward process involving melting thermoplastic resin and injecting it into a mold cavity, knit lines can pose. Injection molding is the most cost-competitive technology for manufacturing high volumes of identical plastic parts. Reduce the injection pressure. After samples have been approved, it’s time to kickoff. 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. Injection moulding (U. They are the result of fundamental physical effects taking place inside of the mold. The above guidelines for initial heater band settings are for most injection molded parts. Knit Lines. 6. land and using maximum vent depths to get them as close to self-cleaning as possible. Troubleshooting Injection Molding Weld Lines. 5-3. Meld and knit lines are actually both different types of weld lines. A weld or meld line is a weakness or visible. 0 and Table 1). A poor knit line can cause cosmetic blemishes and significantly weaken the structural integrity of a part. The pipe underwent brittle fracture into many pieces because of the high residual stresses in the wall of the pipe. The temperature might fall at some places like in the mold, runners leading to the mold and injection molding. In addition to the main factory and development. สาเหตุรองของการเกิดปัญหาการเกิดประกายเงิน (silver streak) 1. 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. Polym. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. Thin wall injection molding can produce walls as thin as 0. Knit lines, also known as weld lines, are fine lines that resemble hairline fractures or cracks. These defects are not visible, like small. A component of the injection-molding machine wherein the resin pellets are melted, compressed and injected into the mold's runner system. From the start of your project, you can count on The Toolroom to exceed your expectations for all of your plastic injection molding needs. The part weight x number of cavities + runner weight should. Meld and knit lines are actually both different types of weld lines. Also known as “stitch lines” or “weld lines”. The present. Learn Injection Molding Glossary with Plastopia: Using actual molded parts (with images) as examples. 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. Mold cooling is one of the most important variables in injection molding. For injection molding of the multi-blade fans and various rotating plastic parts, the complex of multiple gating injection molding tools were used. Trapped air in a mold manifests itself as a burn mark on the molded part. Three terms that often get mixed up in the plastic injection molding industry are weld, meld, and knit lines. The design of the mold, as well as the part being molded, has a significant impact on the success of the process. Flow rate and flow speed are cut in half at every runner branch. doc), PDF File (. In fact, for a 32-cavity mold, the flow rate in this example drops down to 0. This image shows a PVC pipe after it was accidentally dropped on the ground. Check/add vacuum; Check mold lube; Check/increase venting. Figure 1 Flow Lines Knit or Weld Lines Cavity Gates Table 1 Knit line in a multi-injection-point cavity. Additional venting along the parting line perimeter will improve overall venting significantly. This is a video excerpt from our Problems & Solutions Course - Weldlines. Transfer molding also utilizes a press and a mold. Meld and knit lines are actually both different types of weld lines. 2020-01-1306. Knit lines appear to be a faint line or a crack in the finished part after it comes out of the injection mold. 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. Knit lines in injection molding are common defects of the molded parts. Edge Gates. Let’s. However, the process involves forcing the material through small holes into the mold cavity. Many materials can be. Crossref. These defects are not visible, like small. 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. Proper mold cooling can eliminate warp, decrease cycle times, and increase part quality. Weld lines, which are also referred to as knit lines, are among the most common of these blemishes. As melt temperature, viscosity and abrasiveness rise, tool life will decline. Reduce the screw speed and adjust the backpressure. As the melted plastic fills the mold, there are locations where the molten plastic flow stream separates and then comes back together. Also discussed are weld and meld lines and their effects on molded. 030- to 0. Reduce the temperature of the mold and plastic being injected. The goal is to create a uniform thickness and at the smallest (thinnest) level required. Knit lines are hard to eliminate for injection molded plastic parts but designers can minimize cosmetic defects. This article looks at the issues presented by a weld line in injection molding and the techniques manufacturers can use to avoid them. Increase injection speed. In the case of mold. Depends how hard you want to push it. , LTD. Weld lines may appear like seams or scratches,. PROBLEM: FLOWLINES (ALSO CALLED WELD LINES OR KNIT LINES) Definition: Streaks, orange skin, or visible flow lines in parts . These knit lines affect the parts aesthetics, but also they generally decrease the strength of the part. Flow Lines. 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. The structural stability of. Knit lines are typically much weaker. However, the weld line may not continue throughout the flow. 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. From Plastic Materials and Processing by A. 18/06/2021. Meld and knit lines are actually both different types of weld lines. Venting is required to allow the air in the sprue, runner and cavity to leave the tool as the melt flows into the cavity. 3. Prevent Flow and Knit Lines Through Mold Adjustments. When 2 flows meet, small hair-like discolorations may develop. The following are the conclusion drawn from the present research: 1. An option to bluing agents, the long established means of gauging pressure distribution, comes via Pressurex, a thin, flexible, plastic film. Polypropylene Consumer and Injection Molding Containers, Crates, Garden Furniture, Housewares, Luggage, TSL, TWIM lyondellbasell. While knit lines can be present it does not always mean the structural integrity of the plastic part is compromised. While not always visible, weld lines (aka knit lines) are where two resin flows meet. The melt is forced to split up during filling of the cavity. 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. 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. Injection Pressure 0r Speed Too Low Explanation: If the injection speed or pressure is too low, the molten plastic will not be pushed into the mold cavity fast enough to fill and knit at converging flow fronts because it cools down and solidifies too soon. Whereas conventional injection molding uses. 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. "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. occupied frequently with troubleshooting injection molding. Mold filling simulation software should be used to ensure that waterInjection Molding Problems and Solutions (17/17) – Weld or Knit Lines Sep 27, 2022Main causes of knit lines in injection molding: 1. 12515 NE 95th Street , Vancouver, WA 98682 CALL TODAY: 1-800-839-0366Contact FU CHUN SHIN MACHINERY MANUFACTURE CO. Polypropylene can be processed over a wide range of mold temperatures; however, for applications where aesthetics are critical, a surface temperature of 80-95˚CSink Marks Cause 1: Incorrect Melt Temperature. In this case it would be 0. Still, it can be seen to varied degrees depending on mold. 2.