holes, multi-point injection. Undercuts add cost to tooling and molding, which is recommended to eliminate or minimize as possible. 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. A parting-line vent. opposed to two or more gates. Without it, air and gas are trapped in the mold, which compress and heat as the cavity fills. Obstructions in the part create weld lines or knit lines during injection molding. Gates that are too small can also cause the uneven flow of material or result in knit lines, blemishes that occur where two resin flows meet. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different. Obstructions in the part create weld lines or knit lines during injection molding. LS Mtron Injection Molding Machine (IMM) has opened a new business unit in Mexico. PTI has five injection molding presses suitable for MIM. Injection molding is a popular manufacturing process used to fabricate parts in large volumes. He is currently a tooling manager for a large, multi-plant molding and manufacturing company. Inadequate venting may cause short-shots, poor surface appearance, or weak weld-lines. Knit Lines. Get a free des. This is a video excerpt from our Problems & Solutions Course - Weldlines. What Are Cosmetic Standards for Plastic Parts?. 3D printed molds in the injection molding process to lower costs and lead time. To avoid walls that are too fat or too thin, designing a wall thickness between 0. Unsymmetrical filling makes knit lines in samples, leading to the failure of part, so it must be avoided. 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. For best results, keep thickness variations to within 15% of the nominal wall thickness. 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. Reduce clamping force. These flaws can affect the aesthetic and structural integrity of the. 010 inches. Mold venting is critical to the quality and consistency of the finished part. After selecting resin material, the design and process control of injection mold directly influence the quality of formed products. Observation on a “trial and error” basis may be required. Vertical Plastic Injection Molding. Knit lines form when two or more plastic flow fronts collide and solidify or “knit” during the molding process. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. Reduce the injection pressure. Venting is required to allow the air in the sprue, runner and cavity to leave the tool as the melt flows into the cavity. Figure 1 presents the shrinkage of polypropylene versus wall thickness in injection molded parts. The gate is the entry point to the part-forming cavity, where plastic material is injected from the molding machine barrel, through the sprue and runner, into the mold. Injection Molding Process Guidelines The following is given as a potential process starting point. Weld Lines. Raising the mold temperature will keep the material molten longer, resulting in stronger weld lines and even elimination of weld lines. Advantages for your Injection Molding Machine:. Typical Tool Steel for Injection Mold Construction Steel Type Steel Properties Mold Component P-20 Pre-hardened, machines well, high carbon, general-purpose steel. These are caused by the shot of molten plastic moving at different speeds throughout the injection. In this, work, metal inserts were joined with polyamide 6 by using the injection-molding technique. Material contamination, for example, can cause several molding issues. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. A weld line can also be called a knit line. Increase the injection speed. 2 mm. Knit lines appear to be a faint line or a crack in the finished part after it comes out of the injection mold. Chris Newmarker | Dec 27, 2013. Reduce the temperature of the mold and plastic being injected. The metal parts, made of steel grade. Weld lines typically appear in a part when an obstruction of some kind separates the melt flow and prevents it from "knitting" together. ; Wood, Philip E. Increase the injection speed. Increase injection speed and pressure: Faster-moving materials will meet more quickly so one doesn’t cool too soon. A weld line (weld point, flow line or a knit line) forms when separate melt fronts travelling in opposite directions meet. Brent Strong, p. 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. Enlarge gas vents and gates to allow trapped air to escape the mold. 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. Bubbles are caused by melting flow fronts colliding in a mold cavity. Knit/Weld Lines. Investigate the mold for signs that a water leak is present, and correct the condition. Injection molding is an efficient, often cost-effective way to manufacture custom plastics that are strong, durable, and long-lasting. Understanding Knit Lines in Injection Molding: Causes and Solutions. In this paper, a general and efficient approach was proposed for dual-scale infiltration flow balancing based on numerical simulation. Weld / Knit Lines; Assumptions. A meld line occurs when two moving melt fronts converge and flow parallel to each other. H-13 Good general purpose tool steel. spelling: injection molding) is a process for producing parts by injecting molten material into a mould, or mold. The knit line is generally opposite the gate in thermoset. This can enable the manufacturer to increase the molten plastic temperature at the front of each flow and avoid the occurrence of weld lines. In the injection molding process, knit lines are a common occurrence when two or more plastic flow fronts collide and solidify, resulting in a visible seam or line on the molded part. Injection Molding Problems and Solutions (17/17) – Weld or Knit Lines Sep 27, 2022 Injection Molding Problems and Solutions (16/17) – Warpage Sep 15, 2022. Meld and knit lines are actually both different types of weld lines. to prevent improperly placed knit lines or sinking in the plastic downstream from the hinge. Knit Line occurs where different flow fronts of material meet while flowing through the mold. Knit lines are a common defect in injection molding that can affect the appearance and performance of plastic parts. Injection Molding Press. Injection rate plays a role—faster fill times develop more shear, molecular orientation and residual stress. Remove the hardened material from the mold. This performance can ultimately impact many part properties, including surface quality, knit line strength, part ejection force (sticking), dimensions, tolerances. They need the interference of about 0. 030 and 0. A weld or meld line is a weakness or visible. 1-3). Because injection mold design and processing is complex, a set solution will not solve all problems. Its superior flowability allows for precise and flawless filling of injection molds without the risk of flow marks and knit lines. 3. . Ductile Injection Molding 101 - Injection Molding Varying. In layman’s terms, injection molding boils down to four simple steps: Melt material. 18/06/2021. When the molten plastic meets an obstruction. You don't give us much to go on. Extreme geometries can cause knit lines. Our prototype injection molding process helps you cut product development cycles by weeks—sometimes months—and bridge to production with injection-molded parts within days. Some are: Knit lines (discontinuities where two flows merged, creating a weak point)In some situations where a mold has parting line damage, reducing heat can actually improve flash that was a direct result of that damage. Understand the causes of knit lines in injection molding and explore effective solutions to minimize their impact. Basic rule of thumb air in mold must be able to escape at theInjection molding is the predominant manufacturing process used for producing transparent polymer products. Image credit: The Rodon Group. 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. It’s our responsibility to make sure your design comes out of the mold working properly. 763-755-7575. Knit lines and other aesthetic characteristics of the part are strictly related to the plastic’s temperature during molding, so efficient filling time is essential for achieving proper welding lines and quality parts. Islyn Thomas summarized the need for a particular vent location better than I ever could. A machine heats and mixes the plastic until it is in a pliable molten shape, then a screw device turns to force the plastic into an outlet that leads to the mold. Inadequate venting may cause short-shots, poor surface appearance, or weak weld-lines. ”. 250 in. Gates, vents, sliding cams, pick-out inserts, and any other place where the two sides of. When venting stationary inserts or core pins in rib or part details with venting issues, I recommend no more than 0. Runner Type. Take these steps to avoid knit lines. Randy Kerkstra has been in the plastics industry for over 26 years, occupied frequently with. Flow Lines. Cooling Lines, Injection Mold Material has a great impact on injection molded part quality. 3 To get the most out of your Xometry Injection Molding experience, we offer the following part Design Guide with. Notched weld lines then remain near the cavity walls. To learn more about us or to get a quote, click here or call 1-888-893-1587 now. Solution: Increase the injection pressure or speed. txt) or view presentation slides online. They again get resolidified along the surface. A knit line is any line, visible or not, where two resin flows meet. In spite of its cosmetic attributes, a bad knit line can significantly compromise a part. In a plastic injection-molded component, a knit line occurs when 2 different plastic flows emerge in a mold. Shorter knit lines must equate to a stronger part. If the plastic has cooled too. Three terms that often get mixed up in the plastic injection molding industry are weld, meld, and knit lines. 060 and 0. While injection molding itself is a straightforward process involving melting. Here are a few of the most common defects that may occur in plastic injection molding — and how product teams can avoid them. Meld and knit lines are actually both different types of weld lines. The packing pins are similar in construction to mold ejector pins and may also be mold ejector pins depending on mold configuration. There is high defect rate (surface defects/knit line). 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. Knit lines are hard to eliminate for injection molded plastic parts but designers can minimize cosmetic defects. The result is a consistent flow of molten plastic during injection and a quicker filling time. The splay condition can completely cover a part, or it can appear inconsistently in various areas on the part. See UNDERCUT. Weld Lines-3 Ways for Detecting and Correcting. The thermo-rheological findings were used to investigate the sources of weld line weakness. Quick Guide to Injection Molding Amodel® polyphthalamide (PPA) equipment Amodel® PPA resins can be processed on conventional injection molding equipment. 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. 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 material you use, the knit lines could be invisible or obvious—work with an injection molding company to figure out. Last month, in the first part of this two-part installment we focused on the reasons viscosity can change during injection molding. Trapped air in a mold manifests itself as a burn mark on the molded part. - Mold flow analysis to control fill and knit lines. Below is a list of items that should be checked both during normal molding operations and if defects are detected. The injection molding process uses a granular plastic that is gravity fed from a hopper. a knit line will form 180°on the opposite side from the gate location. These defects are not visible, like small. 5. Mold bases, ejector plates, and some cavities (if nickel or chrome plated to prevent rust). But we can’t talk about the injection molding process without discussing the injection molding machine. Weld line. Knit lines; Knit lines always occur once 2 melted materials meet with hair-like discolorations. Very high quality and an extreme fit may. 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. In the 1947 book, Injection Molding of Plastics, the late Dr. H-13 Good general purpose tool steel. 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. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. They are the result of fundamental physical effects taking place inside of the mold. Learn how material selection, part design, and optimizing process parameters can help eliminate knit lines. 120 in. Main causes of knit lines in injection molding: 1. 2. Valve gates are most efficiently. Also, since this part will likely be painted or chrome plated, knit lines are a concern. Other common issues associated with thin walls include uneven cooling, warp, cracks, cosmetic texture inconsistencies, and weak knit lines or fracture points. 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. The example. , 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. 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. Bad habits can cause many different problems with injection molding machines, and flow lines are included in that. 125 inches. These defects are not visible, like small. Specifically, Stokes and. TRADITIONAL MACHINES VENTS. placed usually in the areas last to fill, near knit lines, as well as on the runner system. The differences between knit and meld lines are significant, and they can dramatically impact the part’s structural integrity. Learn Injection Molding Glossary with Plastopia: Using actual molded parts (with images) as examples. The comment on melt flow index is correct, but, I've molded straight PC down to . Facebook. Reducing the size and depth of depressions helps minimize the impact of knit lines. Troubleshooting Injection Molding Weld Lines. Without it, air and gas are trapped in the mold, which compress and heat as the cavity fills. extend mold service life. Check the diameter of the ejector pins and the pin hole tolerances, if the tolerance is too wide this could allow molten plastic to flow down between the pin and hole surface. Mold Flow Analysis computer. IM: hot or warm knit lines are cause by _____ while cold knit lines are caused by _____. This will helpWeld line. knit line formation, application of draft angle and design for assembly. 3. 0 Items. This makes the casting process as efficient and accurate as possible. Computer simulation packages of injection molding have had success in predicting filling behavior in extremely complicated geometries, capable of predicting weld lines’ location exactly. Exploring common molding defects and. On the opposite side. Venting at Weld Lines. 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. It’s economical, efficient, and can produce simple to complex parts with low waste. mystagingwebsite. As. Here are some of the most common cosmetic defects and how to avoid or fix them. Plastic injection molding is the process of injecting molten plastic material into a metal tool which then cools and ejects a plastic part from the machine. Changing the. 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. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection molding processing. 5 : 1 and 3. Weld-line strength for plastics can vary from 20% to nearly 100% of the strength of the plastic itself. This information is intended to be used only as a guideline for designers and processors of modified thermoplastics for injection molding. Weld lines are formed when there is an inability of two or more flow fronts to ‘knit’ or ‘weld,’ together during the molding process. It is typically used for thermoset materials, but can be used with thermoplastics. When the mold adopts the multi-gate pouring scheme, the plastic melt. 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. This type of molding uses a single tool to create both the part's geometry and surface finish in one step. This slight depression is a tiny line called the weld line or knit line. 1. They are the result of fundamental physical effects taking place inside of the mold. They appear around holes or seams of an injection molded part, and some may call them “flow lines” or “weld lines”. It is. Give us a call at (425) 339-0288 or email us at info@sealectplastics. 13758 Johnson Street NE. Learn about the key characteristics of common injection molding materials, recommended applications, and how common thermoplastics compare to one another. Product designers encounter a wide range of challenges when creating and developing molded parts, such as stress factors, warp, and those pesky knit lines. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. A. Injection molding can form complex geometries easily, apply single part with multiple functions. Three terms that often get mixed up in injection molding are weld, meld and knit lines. These defects are not visible, like small. 025 inches per inch, depending on the particular resin, molding conditions, part design, part wall thickness, and direction of flow. Long shapes are produced without multiple drops or hot runner systems, eliminating knit lines and lowering tooling costs. So much. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. When working with customers, our design guidelines for living hinges are 0. They are very much related but independent disciplines. Venting. Knit lines are hard to eliminate for injection molded plastic parts but designers can minimize cosmetic defects. 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. Other Excessive mold release Clean die and use minimal mold release. Remove holes if possible. Reinforcing ribs play a pivotal role in the strength of a plastic part. To account for variations in viscosity, nylon injection molding machines need to maintain an appropriate injection pressure. Injection Molding: How to Set Second. Knit Lines: Holes in the part will always cause knit lines. Weld lines are a common imperfection to be found in most plastic injected molded parts. Multiple gates will always cause knit lines. 25T-0. 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. 18/06/2021. If you want to better understand the process of injection molding, there are a few critical terms you need to know. . Injection molding is the most cost-competitive technology for manufacturing high volumes of identical plastic parts. If debossed pattern is indispensable, it should have a depth of no less than 0. Knit lines don’t. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. Thin walls often lead to material flow problems, which can cause unformed areas. Typically, injection molded parts will be between 0. With over 50 years of experience, Universal Plastic Mold can help you avoid (or at least minimize) knit lines in your molded parts. Incorrectly placed single gates may cause knit lines. In the injection molding process, knit lines are a common occurrence when two or more plastic flow fronts collide and solidify, resulting in a visible seam or line on the molded part. IM: cooling accounts for _____ % of the total cycle time. The Goldilocks principle applied to wall thickness. 4. Depends how hard you want to push it. It happens when the molten plastic material flows around obstacles, such as inserts or cores, and rejoins on the other side. Learn how HPP maximizes these specialized processes. Knit and Meld lines are inherent to plastic injection. There are several possible causes that need to be investigated to troubleshoot weld lines in injection molding. Learn how to troubleshoot weld lines in injection molding. RE: Knit Line Affect On Material Strength lorelei5607 (Automotive). ABS (Acrylonitrile Butadiene Styrene) Benefits: ABS is a tough, impact-resistant plastic that is widely used across many different industries. Flow lines are off-color lines, streaks, and other patterns that appear on the surface of a part. "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. Anisotropy. Understanding Knit Lines in Injection Molding: Causes and Solutions. Change gate locations. From the start of your project, you can count on The Toolroom to exceed your expectations for all of your plastic injection molding needs. CNC-Bearbeitung; Spritzgusswerkzeuge und -teile; Stereolithographie (SLA) Selektives. Plastic injection molding is a complex and highly intricate process. 7584. 5mm (0. Called LS IMM Mexico, the subsidiary is based in Monterrey and led by plastics industry veterans Kevin Kim and Fulvio Menconi. Multiple parts with complex design and differing wall. Moisture in the material due to insufficient drying can form at the melt front, forming an interface between the two melt fronts. 5 : 1 and a L/D (length toMold flow analysis is a software simulation which show how the resin fill in the mold in injection molding process. These knit lines are formed as molten plastic in the injection mold flows around an obstruction like a feature. This most often occurs when you have a core or shutoff feature that the plastic needs to flow around. Such molds or tools aren’t intended to be used in operation. What you should know is that there are various failure modes for injection molding. The injection molding design process, much like all industrial design processes, deals primarily with the creation, look, and feel of a product. As melt temperature, viscosity and abrasiveness rise, tool life will decline. Depending on the design of the mold and the material being injected, a knit line may: present no problem at all, be a. Ideally, a safety strap should be strong enough to prevent the mold from opening under various unforeseen circumstances, but always less than the holding power of the mold clamps and the machine’s mold-opening force. "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. 080" – 0. When injection molding complex parts, often knit-lines are formed during the mold filling stage. A poor knit line can cause only cosmetic blemishes or it can significantly weaken the structural integrity of a part. Weld lines defects are formed when two flow fronts are merged together. The uneven thickness of the product will make the melt flow resistance larger and smaller, resulting in unstable melt flow. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. Degassing – Degassing is the simple operation of opening and closing an injection mold to allow any trapped air (or gas) to escape. In injection molding terms, these are called “living hinges” and are made right into the design instead of adding them later. Mold filling simulation software should be used to ensure that waterExpand. 5. Weld line defects – also known as knit lines – is a defect that occurs when the injected plastic meets within a mold. ABOUT THE AUTHOR. One common problem that occurs in injection molding is the formation of knit lines. ” 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. sheet metal fabrication, rapid tooling, and plastic injection molding. The knit lines are the result of poor molding conditions (likely molding at too low of a temperature). As the melted plastic fills the mold, there are locations where the molten plastic flow stream separates and then comes back together. pdf), Text File (. Edge Gates. Molding parts with multiple gates will almost certainly produce a weld line at right-angles to the line joining the two gates which could cause the weld lines to be exceptionally weak (see Figure 1. 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. Typically, the wall thickness is somewhere in the neighborhood of 50%-75% of your nominal wall thickness. Given the cosmetic requirements, there is a good chance the mold would require. 1. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic. 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. 5 to 3. In situ injection molding of continuous fiber reinforced thermoplastic composites is challenged by unbalanced dual-scale infiltration flow due to the pronounced capillary effect. Inadequate injection pressure can result in knit lines and a surface that appears corrugated. Read on to find out more! 800. While this process is largely efficient and reliable, it's not without its potential issues. 015in wall. These seams are known as “knit lines. 160"). Kim, who has worked for hot runner system and auxiliary equipment supplier Yudo-Abiman for 12 years, most recently as. 344. Knit Lines and Resins. This summary represents a key subset of the detailed molding information found in the remainder of this molding guide . 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. For over four decades, our experienced team and leading edge technology have provided you with tooling solutions from start to finish. Learn more about the process by reading this white paper. During the injection molding process, molten plastic is injected into a mold cavity through a gate. Injection Molding Injection molding is perhaps the most common and important of all plastic processing processes. As these flow fronts come together. A plastic product formed by the injection mold is divided into two parts, and the line separating the product is called the parting line. 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. End-of-arm tooling can make or break a program. 5 mm) is ideal, according to injection molding engineer Jack Rulander of Protolabs in Maple Plain, MN. Short molding cycle, high production efficiency, and easy automation 2. The difference between a knit and meld line is significant, dramatically impacting the part’s structural integrity. A medical device designer might look up a polymer's physical properties and game out. For injection molding of the multi-blade fans and various rotating plastic parts, the complex of multiple gating injection molding tools were used. ABS is a good choice for handheld consumer devices. The mold settings can run flawlessly until employees consistently open the machine for inspections, interrupt cycle times, or cause. Gate and Knit Line Locations<br />. Gate size can be increased or moved to a section with greater wall thickness to help eliminate. Reduce the injection speed to limit the risk of trapping air inside the mold. This article will discuss the importance of injection molding nozzles and what makes a good nozzle for a molding or injection. In plastic part design for injection molding, it is important to design the injection mold so that the molten plastic fills the mold cavity entirely, cools as evenly and as quickly as possible without warping, and functions as intended. Thin wall injection molding can produce walls as thin as 0. As. 3. 4271. When assessing issues with injection molded parts, we want to make sure some core aspects of molding are checked. The linear mold shrinkage of injection molded parts will vary from 0. 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. The Demo Mold helps those new to injection molding easily visualize the process and is a great teaching device for educators. 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. BLEED – (1) To give up color when in contact with water or a solvent. One of the most common ways of adding venting is by manually machining it into the mold (Figs. You don't give us much to go on. 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. All the while, the material could be the correct material," Hill says. ISSUE FACED BY THE INJECTION MOLDING COMPANIES: FLOWLINES (ALSO CALLED WELD LINES OR KNIT LINES) Definition: Streaks, orange skin, or visible flow lines in parts. 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. If you have questions about the suitability of the Protolabs process for your optical parts, contact an applications engineer at 877-479-3680. Gates, vents, sliding cams, pick-out inserts, and any other place where the two sides of. The melt is forced to split up during filling of the cavity.