A well-designed injection-molded part will usually have draft, but the same draft that helps eject a part from the. 4. 3. As a result, the portion has a faint, perhaps undetectable line. 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. High mold temperatures usually provide less residual stress. The melt is forced to split up during filling of the cavity. Considerations: ABS-molded parts will show knit lines and can have sink and voids in thick areas. RELATED CONTENT. INJECTION MOLDING GUIDE V2. Knit and Meld lines are inherent to plastic injection. A parting-line vent. The quality of the answer is directly proportional to the information we have to work with. 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. Injection molding is min-maxed for mass production. 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. Steps involved in Multiple Material Molding. TRADITIONAL MACHINES VENTS. Runner and gates must be balanced. knit line formation, application of draft angle and design for assembly. injection molding. Typical Tool Steel for Injection Mold Construction Steel Type Steel Properties Mold Component P-20 Pre-hardened, machines well, high carbon, general-purpose steel. Rynite® PET is usually processed with melt temperatures between 280 to 285 °C (535 to 545 °F) . Proper venting is essential to molding a defect-free part. The bottom of your rib must also feature a fillet. They appear around holes or seams of an injection. 040-in. The specimens with a weld line at the center were obtained by double gate molding and the specimens without a weld line wereInjection runner too small Increase runner as needed. extend the time between mold maintenance shutdowns. Knit lines. Timing and temperature are significant contributing factors when it comes to flow and knit line defects. Figure 1: D-shaped through-hole in center of gear part accepts the drive shaft. These flaws can affect the aesthetic and structural integrity of the. Gates, vents, sliding cams, pick-out inserts, and any other place where the two sides of. As a result of weak coupling along the knit-line, the weld-line strength can be only about 60% of that of an unreinforced resin. Learn how to troubleshoot weld lines in injection molding. Let’s. 0 to 3. If you have questions about the suitability of the Protolabs process for your optical parts, contact an applications engineer at 877-479-3680. Prevent Flow and Knit Lines During the Injection Molding Process. Reduce the temperature of the mold and plastic being injected. Give us a call at (425) 339-0288 or email us at info@sealectplastics. Very high quality and an extreme fit may. The mold’s sprue bushing and locating ring is placed in a way that makes sure the injection molding nozzle is properly aligned and centered. wall thickness injection molding ribs. BLEED – (1) To give up color when in contact with water or a solvent. 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. Sequential valve gate technology. Knit / Weld Lines. Obstructions in the part create weld lines or knit lines during injection molding. 344. See UNDERCUT. 763-755-7575. With the help of mold flow analysis and mold flow service, mold designers understand how the material fill to position gates better, anticipate where the knit line will appear and locate difficult to fill spots in the injection mold. Weld Lines-3 Ways for Detecting and Correcting. Computer simulation packages of injection molding have had success in predicting filling behavior in extremely complicated geometries, capable of predicting weld lines’ location exactly. ” Depending on the material you use, the knit lines could be invisible or obvious—work with an injection molding company to figure out. Discover why you should avoid knit lines when designing and manufacturing injection moulded parts. When injection molding a part, a knit line may present no problem, or can cause a serious structural problem. These lines. All the while, the material could be the correct material," Hill says. Three terms that often get mixed up in injection molding are weld, meld and knit lines. Our Injection Molding Capabilities • Horizontal Injection Molding up to 3300 TONS • Structural Foam Molding + Structural Web • 1oz to 600oz part capacity. Observation on a “trial and error” basis may be required. Knit lines, holes, part configuration and the talent of your molder all come into play. When injection molding complex parts, often knit-lines are formed during the mold filling stage. Only then can we move on to determining the parting line itself. As a result, prototyping is strongly recommended for parts with. Weld line defects – also known as knit lines – is a defect that occurs when the injected plastic meets within a mold. Typically, this fillet radius should be somewhere near 0. In addition, keep these in mind: Scrap rates can range from less than 1 to 5%. • Holes formed by core pins are, in essence, 360° inside corners and should follow. Bubbles are caused by melting flow fronts colliding in a mold cavity. Understand the causes of knit lines in injection molding and explore effective solutions to minimize their impact. Meld and knit lines are actually both different types of weld lines. By understanding material fill, injection mold designers can better position gates, anticipate where knit lines will appear, and locate difficult to fill spots in the mold. Meld and knit lines are actually both different types of weld lines. The goal is to create a uniform thickness and at the smallest (thinnest) level required. 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. Weld lines defects are formed when two flow fronts are merged together. It happens when the molten plastic material flows around obstacles, such as inserts or cores, and rejoins on the other side. Learn more about the process by reading this white paper. Knit lines are a common defect in injection molding that can affect the appearance and performance of plastic parts. 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 parting-line vent. Mold Flow Analysis computer. Injection Molding Process Guidelines The following is given as a potential process starting point. 4. Enlarge gas vents and gates to allow trapped air to escape the mold. The Problems & Solutions course is designed to train injection molding personnel in. pdf), Text File (. The injection molding process offers a vast array of plastic resins to work with. 1 Gate Location. Edge Gates. Our glossary of terms provides definitions for a wide range of injection molding terms. This performance can ultimately impact many part properties, including surface quality, knit line strength, part ejection force (sticking), dimensions, tolerances. More about the knit lines in injection molding. Venting at Weld Lines. 4. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. As. Generally, the mold structure is roughly divided into two main parts: fixed half and moving half. Reducing the size and depth of depressions helps minimize the impact of knit lines. Knit lines, also known as weld lines are areas in the. 25T-0. It’s called sequential valve gating, or SVG. Change gate locations. This information is intended to be used only as a guideline for designers and processors of modified thermoplastics for injection molding. Undercuts add cost to tooling and molding, which is recommended to eliminate or minimize as possible. This information is intended to be used only as a guideline for designers and processors of modified thermoplastics for injection molding. Weld-lines or knit-lines are formed during the mold filling process when the split melt flow fronts meet at the same downstream location. The injection molding process is on the surface is fairly simple, plastic resin is heated to its melting point and forced into the cavity of the mold to produce a plastic parts. Injection molding is an efficient, often cost-effective way to manufacture custom plastics that are strong, durable, and long-lasting. First, they carry resin to the mold via a runner. Kim, who has worked for hot runner system and auxiliary equipment supplier Yudo-Abiman for 12 years, most recently as. 008 in. This production method is particularly popular when manufacturing in large quantities. The most common and one of the most challenging injection molding defects are weld and knit lines. Plastics Technology article (June 2018): Technical capabilities of the process have advanced to erase former cycle-time penalties, and ongoing developments address creation of a materials database and new applications in hybrid composite injection overmolding. A weld or meld line is a weakness or visible. 0 Items. The area generally has lower strength than the other areas of the part. Nicolet Plastics LLC. Nicolet Plastics LLC. The weld line can either be a minor cosmetic issue. With this option, users can utilize in-cavity pressure or temperature sensors to control when the valves open or close. 008 to 0. In fact, knit line strength will decrease with higher filler content and with longer fibers. Knit lines form when two or more plastic flow fronts collide and solidify or “knit” during the molding process. In plastic injection molding, a parting line is where two halves of a mold meet when closed. This can enable the manufacturer to increase the molten plastic temperature at the front of each flow and avoid the occurrence of weld lines. 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. Injection molding can use thermosets or thermoplastics. • Standard (general purpose) screws with a compression ratio between 2. Short molding cycle, high production efficiency, and easy automation 2. thickness with a spacing of about 0. These knit lines affect the parts aesthetics, but also they generally decrease the strength. The comment on melt flow index is correct, but, I've molded straight PC down to . We ensure customers receive accurate, fast, on-time, sufficient support and services. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. By altering the part design, it may be possible to just have one flow front, and avoid multiple flow fronts having to come together. 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. An undercut is any indentation or protrusion that prohibits an ejection of a part from a one-piece mold. It is typically used for thermoset materials, but can be used with thermoplastics. Wavy lines are another feature of weld lines. Knit lines don’t. (1987). Advantages for your Injection Molding Machine:. In injection molding, a thermoplastic material is melted to a liquid state and injected into a custom, double-sided mold. 3. Understanding Knit Lines in Injection Molding: Causes and Solutions. This design aid shows the mechanics of how the A-side and B-side of a tool work together during the injection molding process to create plastic parts. Adjust the design for the flow pattern to be a single source flow. Check the diameter of the ejector pins and the pin hole tolerances, if the tolerance is too wide this could allow. Usually the parting line of the mold is perpendicular to the mold opening direction of the injection molding machine. Core Geometry. So what does the 140F mold temperature give us? The molding technician thought the 140F mold water was OK because the data sheet provided by the material supplier suggested mold temperatures from 75 to 180F. 250 in. 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. 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. BACK TAPER – Reverse draft used in mold to prevent molded articles from drawing freely. To prevent swirling, perform tests whenever possible and use pre-compounded resin to ensure identical color match across parts. To prevent swirling, perform tests whenever possible and use pre-compounded resin to ensure identical color match across parts. Also known as a knit line, this is the point at which two flow formations meet and are unable to. Plastic injection molding is a complex and highly intricate process. He said, “Vent cavities at weld lines or junction points where two or more material streams meet and fuse into a solid mass. . 2. It allows our molders to monitor fill pressure, cosmetic concerns, and the basic quality of the parts. Anisotropy. Inadequate venting may cause short-shots, poor surface appearance, or weak weld-lines. They occur when melt flow fronts collide in a mold cavity. S. For example, increasing gate size can improve part filling. 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. Our goal of 100% efficiency, zero scrap and repeatable processes can sometimes be hindered by poor setups or changes in the molding process. 140 in. These flaws can affect the aesthetic and structural integrity of the. Multiple gates will always. Flow lines typically manifest as visible marks, often slightly. Still, they are almost always a cosmetic issue. Molding is a manufacturing process in which resin in a barrel is heated to a molten state,. Material contamination, for example, can cause several molding issues. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. It is also where a slide mechanism might meet where it shuts off on one of the mold halves. In fact, knit line strength will decrease with higher filler content and with longer fibers. (If parts are to be molded by Protomold’s rapid injection molding process, our Design Guidelines should be used. Knit Line occurs where different flow fronts of material meet while flowing through the mold. While the presence of knit lines does not always compromise the structural integrity of the plastic part, they are almost always a cosmetic issue. Weld lines may appear like seams or scratches,. The temperature might fall at some places like in the mold, runners leading to the mold and injection molding. Throughout the molding process the press operator visually inspects the molded parts as they come out of the mold for any imperfections such as air trap, knit lines, backrinding, or tearing. Islyn Thomas summarized the need for a particular vent location better than I ever could. The Demo Mold helps those new to injection molding easily visualize the process and is a great teaching device for educators. Figure 1 presents the shrinkage of polypropylene versus wall thickness in injection molded parts. 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. 3. More about the knit lines in injection molding. knit line. Disadvantage: May rust if improperly stored. and 0. Extreme geometries can cause knit lines. Injection moulding (U. The depth of the texture or letters is somewhat. A weld or meld line is a weakness or visible. a knit line will form 180°on the opposite side from the gate location. Knit Line – A molding defect resembling a flow-line found at the point where the rubber meets between the injections. When designing for injection molding, consider these steps to prevent knit lines The Resin Cooling Process. placed usually in the areas last to fill, near knit lines, as well as on the runner system. Lower the melt and mold temperature to prevent overheating. Knit Lines. Multiple parts with complex design and differing wall. Islyn Thomas summarized the need for a particular vent location better than I ever could. 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. Shorter knit lines must equate to a stronger part. When the molten plastic meets an obstruction. com Discover why you should avoid knit lines when designing and manufacturing injection moulded parts. The gate location affects the. These lines occur usually around holes or obstructions and cause locally weak areas in the molded part. 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. Flow Lines Knit or Weld Lines Cavity Gates Table 1 Knit line in a multi-injection-point cavity. Plastic injection molding is the industry’s most common way to manufacture parts. When injection molding a part, a knit line may present no problem, or can cause a serious structural problem. 015in wall. Once the mold is created and the machine is set up, additional parts can be manufactured very fast and at a very low cost. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. Gating. The knit line itself (the vertical line in the middle) is visible in this lighting, but the biggest issue is with the texture. sheet metal fabrication, rapid tooling, and plastic injection molding. Family molds. Following lists causes and solutions for weld or knit lines. With over 50 years of experience, Universal Plastic Mold can help you avoid (or at least minimize) knit lines in your molded parts. 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. be impressed by improvements of bubbles (vacuum voids), short shots, unequal thickness, jetting marks, weld lines, knit lines, black streaks, strain 2. Reduction of sink can possibly be had by switching to an ABS/PC-blended material. Shear Controlled Orientation Injection Molding of Polymeric Composites with Enhanced Properties. With fast accurate, injection-mold simulations, designing injection-molded products, developing injection molds, and shooting parts is more collaborative, accurate, and efficient, saving time and driving down costs. An injection mold that produces pieces while the final tool is being built. Changing the. Knit lines; Knit lines always occur once 2 melted materials meet with hair-like discolorations. Looking to Your Knit Lines with Molding. 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. [8] Bevis, MJ, Reis RL, Cunha AM. In layman’s terms, injection molding boils down to four simple steps: Melt material. 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. 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. Legend: a-in. Understanding Knit Lines in Injection Molding: Causes and Solutions. 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. 3D printed molds in the injection molding process to lower costs and lead time. It’s economical, efficient, and can produce simple to complex parts with low waste. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary from virtually invisible to something that looks like cracks in the plastic. Injection molding machines with footprints similar to desktop FDM and SLA 3D printers are now available. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. As these flow fronts come together. In spite of its cosmetic attributes, a bad knit line can significantly. Because injection mold design and processing is complex, a set solution will not solve all problems. 040 and 0. even though injection molding temperatures are _____ compared to metals, the thermal expansion of plastics is _____ to _____ times that of metals. Gating. The process is extremely versatile, and can produce very complex shaped parts, with the use of multi-sided molds. opposed to two or more gates. Enlarge gas vents and gates to allow trapped air to escape the mold. Most failures occur at what are called “weld lines” or “knit lines”. Shorten the mold cycle time so that any trapped air and resin don’t have a chance to overheat. 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. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. 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). Mold Venting. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. 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. Adding a border around an embossed logo is a good way to protect it from abrasion. Knit lines are a common defect in injection molding that can affect the appearance and performance of plastic parts. The uneven thickness of the product will make the melt flow resistance larger and smaller, resulting in unstable melt flow. 01 inches between parts fitted together to work best. 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. Thermoplastic Elastomer Molding Guidelines. The most common and one of the most challenging injection molding defects are weld and knit lines. You don't give us much to go on. 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. Press fits for injection-molded parts can be challenging. Weld/Meld/Knit lines are all terms describing the effect of two or more flow fronts of material joining or meeting together in the part. It happens when the molten plastic material flows around obstacles, such as inserts or cores, and rejoins on the other side. Core Geometry. . A knit line is what happens when plastic flows coming from two different directions meet inside of the mold and solidify. Weld lines are formed when there is an inability of two or more flow fronts to ‘knit’ or ‘weld,’ together during the molding process. Ductile Injection Molding 101 - Injection Molding Varying. In a weld line, reinforcement fibers. The linear mold shrinkage of injection molded parts will vary from 0. How weld lines form. Understanding Knit Lines in Injection Molding: Causes and Solutions. Runner Type. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection molding processing. Fictiv can help you avoid injection mold design and plastic part design for injection molding problems. Injection molding is the most widely used method for mass-producing plastic parts. IM: cooling accounts for _____ % of the total cycle time. Knit Mark – A witness mark on a molded part, often occurring at the midpoint between two transfer or injection sprue locations. Effect of Injection Moulding Conditions on Knit-line Formation, Plastics Rubber Processing and. When the mold adopts the multi-gate pouring scheme, the plastic melt. 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. After selecting resin material, the design and process control of injection mold directly influence the quality of formed products. He is currently a tooling manager for a large, multi-plant molding and manufacturing company. A screw-type plunger forces the material into a heated chambe r,. So much. Demo Mold. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. Plating and painting applications usually require slower fill rates to keep orientation low. Because viscosity is a. S. Called LS IMM Mexico, the subsidiary is based in Monterrey and led by plastics industry veterans Kevin Kim and Fulvio Menconi. (1. Direct experience designing molds and parts for injection molding and producing the molds and parts is valuable, relevant experience for design students. Injection Molding. Gates, vents, sliding cams, pick-out inserts, and any other place where the two sides of. Our On-demand. Possible causes: Low temperature or fluidity of melted plastic during injection molding. To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. The knit line is generally opposite the gate in thermoset. Three terms that often get mixed up are weld, meld, and knit lines. 040 and 0. Learn how HPP maximizes these specialized processes. Core out parts to eliminate thick walls. Strength at the knit line can be as little as 20% of the. We have two unique offers to meet your needs wherever you are in the product lifecycle. , under its Advanced Technology Program (ATP). 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. Also discussed are weld and meld lines and their effects on molded. 160"). 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. On the opposite side. If life safety is involved, or reliably or efficacy are absolutely required, every part should. The relationship between processing conditions, morphological structure and mechanical properties of knit lines of an injection molded semi-crystalline thermoplastic. Steven. spelling: injection molding) is a process for producing parts by injecting molten material into a mould, or mold. Fig. A knit line is any line, visible or not, where two resin flows meet. Weld Line defect analysis, the most common of many defects in injection moulding products. Also known as a knit line, this is the point at which two flow formations meet and are unable to connect during injection molding. 030 and 0. This configuration positions the injection mechanism at the top of the mold, allowing gravity to play a role in filing the mold cavities. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. The Difference Between Knit and Meld Lines–and Why It Matters. 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. 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. Below is a list of items that should be checked both during normal molding operations and if defects are detected. You don't give us much to go on. For instance, three widely used processes are insert molding, overmolding, and undercuts. 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. He is currently a tooling manager for a large, multi-plant molding and manufacturing company. The parting line location on the injection mold will have an effect on how the cavity and core (both halves of the injection mold) come together and seal. This is a video excerpt from our Problems & Solutions Course - Weldlines. Look for signs of stickiness or burning. The mold-opening force varies widely depending on the type and size of the molding machine. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. Using three test materials, polystyrene (PS), polycarbonate (PC) and polyoxymethylene (POM), the relationship between a design and a processing parameter. incomplete filling or shorts. And, for those who can work within its limitations, rapid injection molding may be suitable for producing some optical parts (and cost as much as 90 percent less than traditional tooling). Users will be able to use in-cavity pressure or temperature sensors to control when the valves open or close. Reduce the injection pressure. Not always a problem, but can cause serious structural issues. 3. 0 mm) is crucial to ensuring that parts cool evenly. 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. Inappropriate temperature. Mold filling simulation software should be used to ensure that waterExpand. They again get resolidified along the surface. Specifically, Stokes and. 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. Injection molding a red component, for example, can pose a challenge because at time the component may be too thin for the pigment itself!. 1-3). Second, the runner leading to a tab gate takes up real estate within the. In addition, the force of the gas holds the appearance side of the part in contact with.