040 and 0. 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. Thermoplastic Elastomer Molding Guidelines. Those are knit lines, formed when two opposing flows of material join together in the mold cavity. Typically, the wall thickness is somewhere in the neighborhood of 50%-75% of your nominal wall thickness. Thin wall injection molding can produce walls as thin as 0. An injection mold that produces pieces while the final tool is being built. Typically, injection molded parts will be between 0. 3. One common problem that occurs in injection molding is the formation of knit lines. The recommended minimum production volume for injection molding is 500 units. Our glossary of terms provides definitions for a wide range of injection molding terms. Lower the melt and mold temperature to prevent overheating. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. Main causes of knit lines in injection molding: 1. "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. 0 mm) is crucial to ensuring that parts cool evenly. These data were obtained from many andKnit lines in injection molding are common defects of the molded parts. A screw-type plunger forces the material into a heated chambe r,. When the molten plastic meets an obstruction. To avoid walls that are too fat or too thin, designing a wall thickness between 0. As melt temperature, viscosity and abrasiveness rise, tool life will decline. Based on the resin. This configuration positions the injection mechanism at the top of the mold, allowing gravity to play a role in filing the mold cavities. Learn how HPP maximizes these specialized processes. Injection Molding Problems and Solutions (17/17) – Weld or Knit Lines Sep 27, 2022injection-molding machine (Arburg allrounder 320C, Germany). 010 inches. An obstruction such as a core pin or holes will split the material flow and cause a weld line issue to form on the other side. Increasing injection speed. 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. As a result, a rib at the weld line junction can strengthen the bosses at the mold line. They are the result of fundamental physical effects taking place inside of the mold. Short shots and knit lines are two phenomena that are caused by using highly viscousTherefore, changing the edges and corners of the mold core to make it buffer transition and keep the melt flow stable can prevent the occurrence of wavy lines. A meld line occurs when two moving melt fronts converge and flow parallel to each other. thickness with a spacing of about 0. For over four decades, our experienced team and leading edge technology have provided you with tooling solutions from start to finish. To prevent swirling, perform tests whenever possible and use pre-compounded resin to ensure identical color match across parts. Contact Universal Plastic Mold Today. Remove holes if possible. Use the fewest number of gates possible. Such molds or tools aren’t intended to be used in operation. The knit line itself (the vertical line in the middle) is visible in this lighting, but the biggest issue is with the texture. to prevent improperly placed knit lines or sinking in the plastic downstream from the hinge. RE: Knit Line Affect On Material Strength lorelei5607 (Automotive). . Weld Line defect analysis, the most common of many defects in injection moulding products. This performance can ultimately impact many part properties, including surface quality, knit line strength, part ejection force (sticking), dimensions, tolerances. 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 venting stationary inserts or core pins in rib or part details with venting issues, I recommend no more than 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. Operating Conditions • Fast injection fill speeds, supporting short injection times (1–3 s), especially in thin sectionsKnit lines in reaction injection moldings Knit lines in reaction injection moldings Maier, Christian; Hrymak, Andrew N. 020"). Typical Tool Steel for Injection Mold Construction Steel Type Steel Properties Mold Component P-20 Pre-hardened, machines well, high carbon, general-purpose steel. PTI, a plastics and metal parts molder, is a leading developer of the MIM process. The linear mold shrinkage of injection molded parts will vary from 0. BACK TAPER – Reverse draft used in mold to prevent molded articles from drawing freely. 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. These are caused by the shot of molten plastic moving at different speeds throughout the injection. Knit lines, also known as weld lines are areas in the. The cooler flow fronts of the resin aren’t forced into the mold surface texture as well as the hotter resin behind the flow front. weld line in injection molding. These knit-lines are well-known as particularly critical regions in the mold when mechanically loaded. 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. Troubleshooting Injection Molding Weld Lines. 1-3). The point of meeting creates a weak spot because the edges of the molten plastic, already cooling, don’t mix together very well. Knit lines are hard to eliminate for injection molded plastic parts but designers can minimize cosmetic defects. The process is extremely versatile, and can produce very complex shaped parts, with the use of multi-sided molds. Trapped gas is one of the most common causes of part burns, and can also lead to short shots and voids, blemishes and discernible knit lines that weaken the part. They are formed when two or more flow frontKnit Line Injection Molding is a process that allows manufacturers to produce parts more quickly, accurately, and at less cost than traditional injection. 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). 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. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. Increase injection speed and pressure: Faster-moving materials will meet more quickly so one doesn’t cool too soon. Injection molding a red component, for example, can pose a challenge because at time the component may be too thin for the pigment itself!. The injection molding process offers a vast array of plastic resins to work with. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. Understanding Knit Lines in Injection Molding: Causes and Solutions. As a result, prototyping is strongly recommended for parts with. Short molding cycle, high production efficiency, and easy automation 2. Optimizing Mechanical Performance of Injection Molded Multiple Gated Rotating Thermoplastic Components: Part 1 - Consideration of Structural Analysis and Knit Line Effects March 2001 DOI: 10. A weld or meld line is a weakness or visible. Ham Lake, MN 55304. The result is a consistent flow of molten plastic during injection and a quicker filling time. This will helpWeld line. Visual indicating with an finished part that are formed by the junction from two plastic flow fronts. AS9100:2016. But any. Looking to Your Knit Lines with Molding. However, with any practice, when the proper care and planning aren’t taken, problems can occur, and with injection molding, knit lines are one of the most common problems. Undercuts add cost to tooling and molding, which is recommended to eliminate or minimize as possible. This most often occurs when you have a core or shutoff feature that the plastic needs to flow around. A parting-line vent. Injection mold design and custom tooling can make or break the success of a finished plastic product. Molding is a manufacturing process in which resin in a barrel is. Gates, vents, sliding cams, pick-out inserts, and any other place where the two sides of. 3D printed molds in the injection molding process to lower costs and lead time. 2. Knit lines appear to be a faint line or a crack in the finished part after it comes out of the injection mold. This makes the casting process as efficient and accurate as possible. 1050 Walnut Ridge Drive. Demo Mold. Nicolet Plastics LLC. Round Rock, TX 78660. Our Injection Molding Capabilities • Horizontal Injection Molding up to 3300 TONS • Structural Foam Molding + Structural Web • 1oz to 600oz part capacity. Additional venting along the parting line perimeter will improve overall venting significantly. 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. Weld lines are a common imperfection to be found in most plastic injected molded parts. These defects are not visible, like small. com Discover why you should avoid knit lines when designing and manufacturing injection moulded parts. Reducing the size and depth of depressions helps minimize the impact of knit lines. There are several possible causes that need to be investigated to troubleshoot weld lines in injection molding. LS Mtron Injection Molding Machine (IMM) has opened a new business unit in Mexico. 3. reduce mold maintenance cost. This guide to thermoplastics and injection molding material selection is aimed at an engineer who plans to quantitatively analyze a part, determine loads, stresses, strains, and environments and make an optimal material decision based on the analysis. Gate design is another critical piece of part function in plastic injection molding. Following lists causes and solutions for weld or knit lines. – Change the thickness of the product. Meld and knit lines are actually both different types of weld lines. Macromol Symp 1988;21/21: 489-500. For injection molding of the multi-blade fans and various rotating plastic parts, the complex of multiple gating injection molding tools were used. 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). 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. Drying Considerations For both virgin and rework, hopper dryers sized to afford theWhen establishing the parting line, we must first define the shape and position of the parting line on the plastic molded item. 3 To get the most out of your Xometry Injection Molding experience, we offer the following part Design Guide with. An undercut is any indentation or protrusion that prohibits an ejection of a part from a one-piece mold. Self-mating parts. molding run to be sure that the temperature does not exceed the recommended limits . Venting. As the melted plastic fills the mold, there are locations where the molten plastic flow stream separates and then comes back together. When injection molding a part, a knit. Increase the injection speed. Runner Type. Product designers encounter a wide range of challenges when creating and developing molded parts, such as stress factors, warp, and those pesky knit lines. Vacuum on the mold does help and many times eliminates the weld line. The melt is forced to split up during filling of the cavity. 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. The Problems & Solutions course is designed to train injection molding personnel in. For over four decades, our experienced team and leading edge technology have provided you with tooling solutions from start to finish. Core Geometry. 3. PAPER ABSTRACT: Desktop injection molding machines and stereolithographic print ed molds make hands-on injection molding production possible in design studio classrooms and labs. When injection molding a part, a knit line may present no problem, or can cause a serious structural problem. 008 to 0. 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. They appear around holes or seams of an injection molded part, and some may call them “flow lines” or “weld lines”. Meld and knit lines are actually both different types of. If you want to better understand the process of injection molding, there are a few critical terms you need to know. He is currently a tooling manager for a large, multi-plant molding and manufacturing company. CNC-Bearbeitung; Spritzgusswerkzeuge und -teile; Stereolithographie (SLA) Selektives. 847-952-8088. In spite of its cosmetic attributes, a bad knit line can significantly compromise a part. Jabil (formerly Nypro) is uniquely qualified to offer a state-of-the-art curriculum in injection molding and related disciplines, which require highly specialized skills and continuous. a specific area on one side lens, a warp line, and a weft line. BLEED – (1) To give up color when in contact with water or a solvent. H-13 Good general purpose tool steel. This summary represents a key subset of the detailed molding information found in the remainder of this molding guide . N174W21430 Alcan Doctor Jackson, WI 53037 262-677-9700; 16685 State Road 32 Mountain, WE 54149 715-276-4200; Prime. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. Vertical Plastic Injection Molding. The plastic in the ‘flow front’ cannot pass through the core pin, so it flows around the core pin splitting into 2 distinct flow fronts. A special mold provided with a glass window was used in order to directly evaluate the flow progression during the filling phase of the injection molding process in a thin-wall cavity and to. Macromol Symp 1988;21/21: 489-500. Most failures occur at what are called “weld lines” or “knit lines”. Reduce the injection pressure. The injection molding process uses a granular plastic that is gravity fed from a hopper. A poor knit line can cause only cosmetic blemishes or it can significantly weaken the structural integrity of a part. For example, increasing gate size can improve part filling. 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. Solution: Increase the injection pressure or speed. Here are some of the most common cosmetic defects and how to avoid or fix them. 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. Considerations: ABS-molded parts will show knit lines and can have sink and voids in thick areas. As the polymer resin is injected into a mold, it flows through all parts of the mold. Weld-line strength for plastics can vary from 20% to nearly 100% of the strength of the plastic itself. Wavy lines are another feature of weld lines. 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. Weld line. In fact, knit line strength will decrease with higher filler content and with longer fibers. • Standard (general purpose) screws with a compression ratio between 2. 01 inches between parts fitted together to work best. The advantages of compression molding include more isotropic fiber distribution, dimensional stability, and surface finish. Family molds. The comment on melt flow index is correct, but, I've molded straight PC down to . Knit Lines and Resins. Knit lines, also known as weld lines, are fine lines that resemble hairline fractures or cracks. IM: hot or warm knit lines are cause by _____ while cold knit lines are caused by _____. Gate locations can be directly behind or on the edge of the graphic. He is currently a tooling manager for a large, multi-plant molding and manufacturing company. The following are general guidelines for molding acetal. And the lead-time for overmolded and insert molded parts is 15 days, a bit longer than FacFox’ single-part injection molding turnaround, but still much faster than traditional insert molding. This month, we covered an array of topics including injection mold venting, business strategies and runnerless micro molds. Weld lines are a common imperfection to be found in most plastic injected molded parts. (1. Weld Lines-3 Ways for Detecting and Correcting. These flaws can affect the aesthetic and structural integrity of the. Knit lines; Knit lines always occur once 2 melted materials meet with hair-like discolorations. Meld and knit lines are actually both different types of weld lines. This information is intended to be used only as a guideline for designers and processors of modified thermoplastics for injection molding. 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. Flow Lines Knit or Weld Lines Cavity Gates Table 1 Knit line in a multi-injection-point cavity. Also known as weld lines, knit lines. The linear mold shrinkage of injection molded parts will vary from 0. Swirling can increase depending on the material you use, and the texture or polish of injection molding tools. 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. Starting in September, the CoPilot process control system developed by RJG will come equipped with valve gate control. Fig. They are formed downstream through holes, and between multiple gate locations. Knit lines appear to be a faint line or a crack in the finished part after it comes out of the injection mold. When working with customers, our design guidelines for living hinges are 0. Factors were ordered. The Jabil Molding Institute empowers employees, customers and suppliers to utilize the most advanced plastics and related manufacturing techniques in the world. 5 mm) is ideal, according to injection molding engineer Jack Rulander of Protolabs in Maple Plain, MN. 2. Knit lines, also known as weld lines are areas in the molded part where two or more flow fronts converge. 4. 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. "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. This slight depression is a tiny line called the weld line or knit line. Disadvantage: May rust if improperly stored. Very high quality and an extreme fit may. It has low shrink and high dimensional stability, and it has good resistance to acids and bases. Fortunately, there is a technique that provides almost unlimited control over which parts of a tool fill when and how fast. The final molding process may be dependent upon factors. Please read on, stay posted, subscribe, and we welcome you to tell us what you think. Steven. Meld and knit lines are actually both different types of weld lines. So. The weld line can either be a minor cosmetic issue. sinks, knit lines, and shrinkage,” Spalding says. 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. In a plastic injection-molded component, a knit line occurs when 2 different plastic flows emerge in a mold. Its superior flowability allows for precise and flawless filling of injection molds without the risk of flow marks and knit lines. Specific attention to processing details will enhance quality and productivity . Learn Injection Molding Glossary with Plastopia: Using actual molded parts (with images) as examples. such as knit lines and other imperfections. 4. Knit lines may also be called stitch lines, weld lines, or meld lines. 5. With over 50 years of experience, Universal Plastic Mold can help you avoid (or at least minimize) knit lines in your molded parts. The parting lines is where the two injection mold halves (A side and B side) meet. A weld line can also be called a knit line. Image credit: The Rodon Group. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. One of the most common ways of adding venting is by manually machining it into the mold (Figs. 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. 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. As these flow fronts come together. Gates, vents, sliding cams, pick-out inserts, and any other place where the two sides of. The mold settings can run flawlessly until employees consistently open the machine for inspections, interrupt cycle times, or cause. In situ injection molding of continuous fiber reinforced thermoplastic composites is challenged by unbalanced dual-scale infiltration flow due to the pronounced capillary effect. PTI has five injection molding presses suitable for MIM. In a plastic injection-molded component, a knit line occurs when 2 different plastic flows emerge in a mold. When the mold body is closed, the contact surface of the cavity and core plates makes a parting line. 05-million grant for MIM R&D from the National Institute of Standards and Technology (NIST) in Washington, D. The parting line will always be visible, but can be minimized by its location, draft allowance and part geometry. This most often occurs when you have a core or shutoff feature that the plastic needs to flow around. Multiple parts with complex design and differing wall. It happens when the molten plastic material flows around obstacles, such as inserts or cores, and rejoins on the other side. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. Also known as knit lines. We ensure customers receive accurate, fast, on-time, sufficient support and services. It can also aid in material selection since fill. Weld-lines look like cracks on the appearance of plastic. Imagine a river splitting to go around a rock, then meeting up again on the other side. In plastic injection molding, a parting line is where two halves of a mold meet when closed. Multiple gates will always. INJECTION MOLDING GUIDE V2. Learn how material selection, part design, and optimizing process parameters can help eliminate knit lines. Shorter knit lines must equate to a stronger part. A poor knit line can cause only cosmetic blemishes or it can significantly weaken the structural integrity of a part. If you have questions about the suitability of the Protolabs process for your optical parts, contact an applications engineer at 877-479-3680. 4. These data were obtained from many andKnit lines in injection molding are common defects of the molded parts. A medical device designer might look up a polymer's physical properties and game out. Plasti-Co ® manufactures a wide range of injection molding nozzles from standard nozzle tips, extended nozzle tips, nozzle bodies, extended nozzles. Inadequate venting may cause short-shots, poor surface appearance, or weak weld-lines. 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. Not always a problem, but can cause serious structural issues. ” Depending on the material you use, the knit lines could be invisible or obvious—work with an injection molding company to figure out. With this option, users can utilize in-cavity pressure or temperature sensors to control when the valves open or close. Without it, air and gas are trapped in the mold, which compress and heat as the cavity fills. 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. It’s economical, efficient, and can produce simple to complex parts with low waste. 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. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. These knit-lines are well-known as particularly critical regions in the mold when mechanically loaded. While injection molding itself is a straightforward process involving melting. Contact Universal Plastic Mold Today. Complex parts can be reproduced with low cost once mold is manufactured. Over the years, I have developed two separate “5M” systems. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. 3. A weld line (weld point, flow line or a knit line) forms when separate melt fronts travelling in opposite directions meet. Because they can be shut off independently you can control flow fronts and knit-line locations. TEXAS. The depth of the texture or letters is somewhat. Flow lines are off-color lines, streaks, and other patterns that appear on the surface of a part. Depending on the design of the mold and the material being injected, a knit line may: present no problem at all, be a. 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. 040-in. 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. Chris Newmarker | Dec 27, 2013. 5 to 3. 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. 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. 5 : 1 and 3. 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. ISO 9001:2015. Without it, air and gas are trapped in the mold, which compress and heat as the cavity fills. See UNDERCUT. Obstructions in the part create weld lines or knit lines during injection molding. 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. S. • Holes formed by core pins are, in essence, 360° inside corners and should follow. Core out parts to eliminate thick walls. Knit/Weld Lines. A weld line refers to a line, notch or color change that is created on the molded part caused by the convergence of two separate flows of molten plastic. 2 mm. injection molding machines using standard industry practices . Press fits for injection-molded parts can be challenging. This occurs wherever there is a hole, notch, or any other feature on a part which divides the flow of plastic into 2 separate “flow fronts. 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 seams are known as “knit lines. Figure 1: D-shaped through-hole in center of gear part accepts the drive shaft. 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. 008 to 0. 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. Mold venting should be checked and increased if necessary, injection molding service. The Difference Between Knit and Meld Lines–and Why It Matters. Quick Guide to Injection Molding Amodel® polyphthalamide (PPA) equipment Amodel® PPA resins can be processed on conventional injection molding equipment. The packing pins are similar in construction to mold ejector pins and may also be mold ejector pins depending on mold configuration. Here are a few ways to prevent knit lines in your plastic parts: Increase material temperature: Higher temperatures on both materials prevent one section from cooling too quickly. This course outlines mold filling and how different gating configurations affect filling. Once the plastic sets, the mold opens to eject the product. In the case of mold details, knits will occur on the lee side of a detail. One of the most common ways of adding venting is by manually machining it into the mold (Figs. Venting at Weld Lines. 025 inches per inch, depending on the particular resin, molding conditions, part design, part wall thickness, and direction of flow. 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. 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. Plasti-Co® Nozzles for Injection Molding Machines. The relationship between processing conditions, morphological structure and mechanical properties of knit lines of an injection molded semi-crystalline thermoplastic. The area generally has lower strength than the other areas of the part. What Are Cosmetic Standards for 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. Mold bases, ejector plates, and some cavities (if nickel or chrome plated to prevent rust). The best we can hope for is to pressurize the knit or meld line better through the combination of melt temperature, mold temperature, flow rate, and holding pressure. Guideline for Design, Material Selection and General Application of Encapsulation of Electronic Circuit Assembly by Low Pressure Molding with ThermoplasticsThis was usually with a PC/ABS material at knit lines and high fill pressures from thin walls in the part. A well-designed injection-molded part will usually have draft, but the same draft that helps eject a part from the. BACKING PLATE – In mold construction, a plate used as a support for the cavity blocks, guide pins, bushings, etc. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection molding processing. See UNDERCUT. This most often occurs when you have a core or shutoff feature that the plastic needs to flow around. Because injection mold design and processing is complex, a set solution will not solve all problems. It is caused by the incomplete joining of the uncured. Islyn Thomas summarized the need for a particular vent location better than I ever could. But we can’t talk about the injection molding process without discussing the injection molding machine. The temperature might fall at some places like in the mold, runners leading to the mold and injection molding. Degassing – Degassing is the simple operation of opening and closing an injection mold to allow any trapped air (or gas) to escape. These lines. Corrosion resistance. After selecting the direction in which the mold hole will be cut, it is much simpler to locate the separating line. Here are some ways manufacturers can avoid quality issues during the plastic injection molding process: Inadequate Injection/Holding Pressure: If injection and holding.