Please read on, stay posted, subscribe, and we welcome you to tell us what you think. We have two unique offers to meet your needs wherever you are in the product lifecycle. Islyn Thomas summarized the need for a particular vent location better than I ever could. Injection molding is the most cost-competitive technology for manufacturing high volumes of identical plastic parts. 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. 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. Short molding cycle, high production efficiency, and easy automation 2. 18/06/2021. Additional venting along the parting line perimeter will improve overall venting significantly. The Jabil Molding Institute empowers employees, customers and suppliers to utilize the most advanced plastics and related manufacturing techniques in the world. Knit Lines 11: 1. Over the years, I have developed two separate “5M” systems. The depth of the texture or letters is somewhat. Weld line. Injection molding a red component, for example, can pose a challenge because at time the component may be too thin for the pigment itself!. [1] Plastic injection molding is the industry’s most common way to manufacture parts. Typical Tool Steel for Injection Mold Construction Steel Type Steel Properties Mold Component P-20 Pre-hardened, machines well, high carbon, general-purpose steel. Computer simulation packages of injection molding have had success in predicting filling behavior in extremely complicated geometries, capable of predicting weld lines’ location exactly. Inappropriate temperature. One of the most common ways of adding venting is by manually machining it into the mold (Figs. A poor knit line can cause only cosmetic blemishes or it can significantly weaken the structural integrity of a part. Weld line defects – also known as knit lines – is a defect that occurs when the injected plastic meets within a mold. • Holes formed by core pins are, in essence, 360° inside corners and should follow. 3 To get the most out of your Xometry Injection Molding experience, we offer the following part Design Guide with. txt) or view presentation slides online. The linear mold shrinkage of injection molded parts will vary from 0. Injection Molding: How to Set Second. Also known as weld lines, knit lines. spelling: injection molding) is a process for producing parts by injecting molten material into a mould, or mold. On the opposite side. For the metal feedstock, injection and mold-wall temperatures were 130 ºC. Factors were ordered. This is the first article in a new series that will examine the injection molding process by breaking down the path a plastic pellet takes as it is transformed from Pellet 2 Part. Weld-lines look like cracks on the appearance of plastic. In the case of mold details, knits will occur on the lee side of a detail. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. 0 mm) is crucial to ensuring that parts cool evenly. 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. Inject the molten material into a mold. Als einer der führenden deutschen Hersteller von Masterbatches stellen wir nicht nur Farb-Masterbatches, Additiv-Masterbatches und funktionelle Kunststoff-Compounds her – wir leben deutsches Forscher-, Ingenieurs- und Unternehmertum. They occur when melt flow fronts collide in a mold cavity. 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. Wavy lines are another feature of weld lines. Take these steps to avoid knit lines. 080" – 0. 5 : 1 and 3. 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. Meld and knit lines are actually both different types of weld lines. The tooling engineer in the mold house will be more into venting, sprue pressure, preheating the mold, cycle times, ejector pin scheme, mold flow, getting a gate location to avoid fill issues or knit lines, excessive flash and molding pressures, and the list goes on. We all know that injection moulding is great for producing both custom prototypes and end-use production parts, but if you are not careful it can cause some. Injection mold design and custom tooling can make or break the success of a finished plastic product. wall thickness, knit lines, draft. RJG announced that its injection molding process control system, CoPilot, will begin offering valve gate control technology for hot runners starting in September 2021. Reduce the injection speed to limit the risk of trapping air inside the mold. Islyn Thomas summarized the need for a particular vent location better than I ever could. 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. To avoid walls that are too fat or too thin, designing a wall thickness between 0. Swirling can increase depending on the material you use, and the texture or polish of injection molding tools. Knit lines. Obstructions in the part create weld lines or knit lines during injection molding. The knit lines are the result of poor molding conditions (likely molding at too low of a temperature). 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. INJECTION MOLDING GUIDE V2. We look forward to offering support and advice on your next project. In injection molded parts, there are 2 types of weld lines: The first type of weld mark is called cold-melt joints and is formed when the melt front enters the cavity with different gates. Increasing injection speed. 5 kN/cm2 (4 T/in2 ) is required. BACKING PLATE – In mold construction, a plate used as a support for the cavity blocks, guide pins, bushings, etc. Weld-lines or knit-lines are formed during the mold filling process when the split melt flow fronts meet at the same downstream location. Depends how hard you want to push it. . The only parts that count are the ones that meet quality standards, and keeping pressure evenly distributed across a mold’s parting lines is one of the many critical tasks to get those good parts molded. Give us a call at (425) 339-0288 or email us at info@sealectplastics. Plasti-Co ® manufactures a wide range of injection molding nozzles from standard nozzle tips, extended nozzle tips, nozzle bodies, extended nozzles. 008 to 0. Legend: a-in. Weld line in injection molding is line where two or more flow molten plastics knit together. 030- to 0. Solution: Increase the injection pressure or speed. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. 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. Called LS IMM Mexico, the subsidiary is based in Monterrey and led by plastics industry veterans Kevin Kim and Fulvio Menconi. 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. The gate location affects the. One common problem that occurs in injection molding is the formation of knit lines. RELATED CONTENT. Over the years, I have developed two separate “5M” systems. 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. 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. Design with Plastics - for Injection Molding process. What Are Knit Lines in Injection Molding, and How Do You Prevent Them? - RJG, Inc. thickness with a spacing of about 0. 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. 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. Depending on the resin, resin temperature, mold temperature, and filling. 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. In spite of its cosmetic attributes, a bad knit line can significantly compromise a part. But add 30% glass and weld-line strength retention drops to only 34% as high as the compound with no weld line. When assessing issues with injection molded parts, we want to make sure some core aspects of molding are checked. 040 and 0. 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. When working with customers, our design guidelines for living hinges are 0. Let’s. In places where the plastic flows around a solid piece of the mold, from a simple circle to forming complex shapes like rings or squares. 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. A meld line occurs when two moving melt fronts converge and flow parallel to each other. For injection molding of the multi-blade fans and various rotating plastic parts, the complex of multiple gating injection molding tools were used. When designing for injection molding, consider these steps to prevent knit lines The Resin Cooling Process. 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. The Goldilocks principle applied to wall thickness. Services Group. Shorten the mold cycle time so that any trapped air and resin don’t have a chance to overheat. 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. The depth of the texture or letters is somewhat limited, and extra draftParts were molded at a maximum injection pressure of 235 MPa, a maximum clamping force of 800 kN, a maximum injection speed of 900 mm/s, and a maximum injection stroke of 120 mm. When designing for injection molding, consider these steps to prevent knit lines Resin cools as it is injected into a mold. A weld or meld line is a weakness or visible. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. CNC-Bearbeitung; Spritzgusswerkzeuge und -teile; Stereolithographie (SLA) Selektives. 0 Items. These lines. Weld lines: Also known as knit lines, these are molding defects that occur when two flow fronts meet without the ability to “weld. opposed to two or more gates. 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. See UNDERCUT. ”. Vertical Plastic Injection Molding. Material contamination, for example, can cause several molding issues. TEFABLOC™ TOSI 431 75A is a high-flow thermoplastic elastomer (TPE) designed for large-part injection molding applications, offering exceptional flexibility and weather resistance. Step 2: The injected molten plastic is cooled followed by the separation of the core and cavities. 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. Commonly seen at the edge of a hole or other cored feature, knit lines are—as a rule—purely cosmetic, but may create a physical failure point if present in an area of the part that receives substantial stress, such as the head of a screw. Imagine a river splitting to go around a rock, then meeting up again on the other side. Commonly seen at the edge of a hole or other cored feature, knit lines are—as a. Wax or ceramic core size or location See Section 3. Users will be able to use in-cavity pressure or temperature sensors to control when the valves open or close. 1 Gate Location. Use the fewest number of gates possible. Submarine Gates. Notched weld lines then remain near the cavity walls. The packing pins are similar in construction to mold ejector pins and may also be mold ejector pins depending on mold configuration. 4. The mold settings can run flawlessly until employees consistently open the machine for inspections, interrupt cycle times, or cause. By altering the part design, it may be possible to just have one flow front, and avoid multiple flow fronts having to come together. All that considered, for a specific simple part with specific quality requirements. Knit and meld lines are inherent to plastic. The injection molding processing conditions for filling are given in Table 1. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different. The bottom of your rib must also feature a fillet. ” What else can you do about weld lines—besides redesigning the mold or gate locations or adjust the flow pattern during fill with sequential valve gating? I recently saw a report on this issue from Moldex3D, the maker of molding simulation software. 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. 25T-0. Behind the obstruction, the flows try to merge again, but this is made more difficult by a low temperature of the mold surface and a low melt pressure. It’s called sequential valve gating, or SVG. Reduce the injection pressure. As these flow fronts come together. As. Bad habits can cause many different problems with injection molding machines, and flow lines are included in that. In this, work, metal inserts were joined with polyamide 6 by using the injection-molding technique. Dabei erreichen unsere Produkte zufriedene Käufer in mehr als 30 Ländern. In addition, keep these in mind: Scrap rates can range from less than 1 to 5%. Corrosion resistance. High mold temperatures usually provide less residual stress. In an injection molded structural plastic part, a weld line (also called a knit line) will result in a region of mechanical weakness as soon as the part is submitted to an external load. Knit lines, also known as weld lines or meld lines, are visible lines or seams that appear on a molded part where two or more flow fronts meet during the injection molding process. Most failures occur at what are called “weld lines” or “knit lines”. The melt is forced to split up during filling of the cavity. Know about the cause of these lines and the potential solutions. Typically, this fillet radius should be somewhere near 0. May 24th, 2019 Posted in Injection Molding Flaw Repair Preventing Flow Lines, Knit Lines, & Blush Injection molding isn’t an exact science, and there is a lot that can go. Such molds or tools aren’t intended to be used in operation. Submarine gates are another injection molding types of gate that is located below the surface of the part, typically on the underside or back of the part. Find out more by calling 573-437-4154 today or email us. S. Knit Lines: These occur when different flow fronts come together as plastic flows through the part cavities. Gate and Knit Line Locations<br />. Enlarge gas vents and gates to allow trapped air to escape the mold. For example, increasing gate size can improve part filling. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. Injection molding weld lines refer to a line on an injection molded part that is generated where the two halves of the mold come together. 008 to 0. But any. As a result, a rib at the weld line junction can strengthen the bosses at the mold line. Adjust the design for the flow pattern to be a single source flow. Quick Guide to Injection Molding Amodel® polyphthalamide (PPA) equipment Amodel® PPA resins can be processed on conventional injection molding equipment. PAPER ABSTRACT: Desktop injection molding machines and stereolithographic print ed molds make hands-on injection molding production possible in design studio classrooms and labs. Adding a border around an embossed logo is a good way to protect it from abrasion. Three terms that often get mixed up are weld, meld, and knit lines. Even parts with metal inserts can be produced. 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). Because injection mold design and processing is complex, a set solution will not solve all problems. The most common and one of the most challenging injection molding defects are weld and knit lines. Meld and knit lines are actually both different types of weld lines. 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. Injection moulding (U. Injection molding can be a real challenge if you don’t follow the “Five M’s”: Man, Mold, Machine, Material and Method. If life safety is involved, or reliably or efficacy are absolutely required, every part should. 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 adhesiveWeld lines, created in the areas of collision of two flow fronts of plastic in the injection mold cavity, are the reason of lower mechanical properties and a worse surface condition of molded parts. Learn how material selection, part design, and optimizing process parameters can help eliminate knit lines. An undercut is any indentation or protrusion that prohibits an ejection of a part from a one-piece mold. BURN MARKS Burn Marks: burn marks can occur when the design of a plastic part, and the subsequent injection mold design, causes air to be trapped during the injection (or filling stage) of the molding cycle. These seams are known as “knit lines. To prevent swirling, perform tests whenever possible and use pre-compounded resin to ensure identical color match across parts. Knit lines are hard to eliminate for injection molded plastic parts but designers can minimize cosmetic defects. Plastic is then injected at high pressure into the mold, and it solidifies with any surface features or defects in. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. Second, the runner leading to a tab gate takes up real estate within the. When the plastic cools, it takes the shape of the mold and is then ejected and finished. They are formed downstream through holes, and between multiple gate locations. Causes 1. The last cause of flow lines may be the operators running your daily operations. As a result, prototyping is strongly recommended for parts with. 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. Insufficient injection pressure and speed can cause weld lines. A knit line is what happens when plastic flows coming from two different directions meet inside of the mold and solidify. Three terms that often get mixed up in injection molding are weld, meld and knit lines. The Difference Between Knit and Meld Lines–and Why It Matters. PTI has five injection molding presses suitable for MIM. When injection molding complex parts, often knit-lines are formed during the mold filling stage. This continues until the weld lines in plastic injection molding disappear. Flow lines, also known as weld lines or knit lines, are discontinuous lines or streaks that appear on the surface of an injection-molded part. These materials have beenThe wall thicknesses of an injection molded part generally range from 2mm – 4mm (0. While this process is largely efficient and reliable, it's not without its potential issues. This course outlines mold filling and how different gating configurations affect filling. 6 Monate. Proper venting is essential to molding a defect-free part. A. , Rallis, A. 4. Knit lines are a common defect in injection molding that can affect the appearance and performance of plastic parts. injection molding. A knit line is any line, visible or not, where two resin flows meet. com. The knit lines are the result of poor molding conditions (likely molding at too low of a temperature). Mold flow analysis is a software simulation that can show how resin will fill the mold during the injection molding process. A plastic product formed by the injection mold is divided into two parts, and the line separating the product is called the parting line. occupied frequently with troubleshooting injection molding. weld lines may form during the injection molding process and work closely with the plastic injection molder and tool builder to choose the best possible gate location. When injection molding a part, a knit line may present no problem, or can cause a serious structural problem. Typically, injection molded parts will be between 0. Inadequate injection pressure can result in knit lines and a surface that appears corrugated. Weld-line strength for plastics can vary from 20% to nearly 100% of the strength of the plastic itself. Double push filling method. 030 and 0. Which affect parts aesthetics and decrease parts strength. 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. More about the knit lines in injection molding. This type of molding uses a single tool to create both the part's geometry and surface finish in one step. Increase injection speed and pressure: Faster-moving materials will meet more quickly so one doesn’t cool too soon. Reduce clamping force. 6. Those are knit lines, formed when two opposing flows of material join together in the mold cavity. Typical Tool Steel for Injection Mold Construction Steel Type Steel Properties Mold Component P-20 Pre-hardened, machines well, high carbon, general-purpose steel. 847-952-8088. Therefore various injection molding defects can be eliminated. Injection moulding can be performed with a host of materials mainly including metals (for which the process is called die-casting ), glasses, elastomers, confections, and most commonly thermoplastic and. • Standard (general purpose) screws with a compression ratio between 2. Starting in September, the CoPilot process control system developed by RJG will come equipped with valve gate control. 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). Injection molding crush ribs are small, protruding features added to molding designs to support and improve the stability of press-fit connections. These flaws can affect the aesthetic and structural integrity of the. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. Knit lines. Weld lines, also known as knit lines, are lines that appear on the surface of an injection-molded part where two or more flow fronts meet and fuse together. C. Injection molding machines with footprints similar to desktop FDM and SLA 3D printers are now available. Also known as weld lines, knit lines. These defects are not visible, like small. Here are a few of the most common defects that may occur in plastic injection molding — and how product teams can avoid them. Thick sections take longer to cool than thin ones. Other materials, like LCP are great for thin wall micro molding but also notorious for having a bad knit line, potentially snapping from excessive torque in later manufacturing processes. Degassing – Degassing is the simple operation of opening and closing an injection mold to allow any trapped air (or gas) to escape. 3. You don't give us much to go on. com . IM: cooling accounts for _____ % of the total cycle time. "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. Macromol Symp 1988;21/21: 489-500. Reduce the injection pressure. Macromol Symp 1988;21/21: 489-500. Adjusting features to be suitable for molding will help resin flow well into the mold, allow it to cool evenly, and reduce the chance of cosmetic defects such as sink, knit lines, flash, and warp. Knit Lines. Randy Kerkstra has been in the plastics industry for over 26 years, occupied frequently with. So. All the while, the material could be the correct material," Hill says. land and using maximum vent depths to get them as close to self-cleaning as possible. Tips for Avoiding Knit Lines in Injection Molding Keeping the proper temperature in the injection molding machine, runners, and within the mold are all key to ensuring. These include: Symmetrical parts. How weld lines form. Rynite® PET is usually processed with melt temperatures between 280 to 285 °C (535 to 545 °F) . Looking to Your Knit Lines with Molding. In spite of its cosmetic attributes, a bad knit line can significantly. These flaws can affect the aesthetic and structural integrity of the. The areas in the cavity where such buildup tends to be common are at end-of-fill areas, details that trap gas, and knit lines. Also known as string lines. This defect is caused from excessive lube or oily stock. Knit lines don’t. The area generally has lower strength than the other areas of the part. Figure 1 Flow Lines Knit or Weld Lines Cavity Gates Table 1 Knit line in a multi-injection-point cavity. When injection molding a part, a knit line may present no problem, or can cause a serious structural problem. 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. Extreme geometries can cause knit lines. Table 2 lists the<br /> properties of common tool steels and the typical mold components for which they are<br /> used. In layman’s terms, injection molding boils down to four simple steps: Melt material. Flow Lines. They are the result of fundamental physical effects taking place inside of the mold. This will helpWeld line. BLEED – (1) To give up color when in contact with water or a solvent. If the plastic has cooled too. Our On-demand. Back to News Page. The chart below shows recommended wall thicknesses for common injection molding resins. These defects are not visible, like small. It happens when the molten plastic material flows around obstacles, such as inserts or cores, and rejoins on the other side. Bubbles are caused by melting flow fronts colliding in a mold cavity. Weld lines defects are formed when two flow fronts are merged together. To prevent swirling, perform tests whenever possible and use pre-compounded resin to ensure identical color match across parts. The injection molding process offers a vast array of plastic resins to work with. These lines are the result of the molten plastic material recombining after splitting and flowing around an obstacle in the mold cavity. The Difference Between Knit and Meld Lines–and Why It Matters. Temperature is another factor that can cause weld or knit lines in injection molding. Plating and painting applications usually require slower fill rates to keep orientation low. A parting-line vent. [1]Weld Lines. Hartland, WI 53029. Except for a few very simple injection molded parts, they occur on most injection molded parts (typically in the form of a line or V-groove), especially large complex items that require use of multi-gate molds and inserts. Plastic injection molding has long been an affordable and efficient process for producing custom prototypes and end-use production parts. You don't give us much to go on. Knit lines appear to be a faint line or a crack in the finished part after it comes out of the injection mold. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. It can also aid in material selection since fill. 025 inches per inch, depending on the particular resin, molding conditions, part design, part wall thickness, and direction of flow. Reduce the injection speed to limit the risk of trapping air inside the mold. Plastic melt and mold temperature. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. 025 inches per inch, depending on the particular resin, molding conditions, part design, part wall thickness, and direction of flow. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. Weld Line defect analysis, the most common of many defects in injection moulding products. 1050 Walnut Ridge Drive. Weld lines may appear like seams or scratches, but that is not what they are. , 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. 1513 Sam Bass Rd. Nicolet Plastics LLC. Core Geometry. The company provides an array of digital manufacturing expertise. These data were obtained from many andKnit lines in injection molding are common defects of the molded parts. When injection molding complex parts, often knit-lines are formed during the mold filling stage. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. knit lines and parting lines are at the discretion of MIC-ZG. Soft metals, such as aluminum and beryllium copper, can be used for prototype<br />. Dimensional stability. Solution: Increase the injection pressure or speed. Be wary of saving too much weight or you might end up with: cracking. They again get resolidified along the surface. Mold bases, ejector plates, and some cavities (if nickel or chrome plated to prevent rust). Still, it can be seen to varied degrees depending on mold. Thermoplastic Elastomer Molding Guidelines.