) are easy to produce. Bubbles are caused by melting flow fronts colliding in a mold cavity. These defects are not visible, like small. After selecting resin material, the design and process control of injection mold directly influence the quality of formed products. Having uniform wall thicknesses between 0. Two major sources of weld lines are multiple gating and flow around pins. Without adequate support pillars, flashing of the parting line faces and bowing of the plates may occur. A knit line is the spot where two flows meet. This makes the casting process as efficient and accurate as possible. Knit lines, also known as weld lines are areas in the molded part where two or more flow fronts converge. (1. It is also where a slide mechanism might meet where it shuts off on one of the mold halves. Learn more. Another name given to weld lines is meld line. Learn about the key characteristics of common injection molding materials, recommended applications, and how common thermoplastics compare to one another. Also known as a knit line, this is the point at which two flow formations meet and are unable to. In spite of its cosmetic attributes, a bad knit line can significantly. Figure 1 Flow Lines Knit or Weld Lines Cavity Gates Table 1 Knit line in a multi-injection-point cavity. As. doc), PDF File (. Last month, in the first part of this two-part installment we focused on the reasons viscosity can change during injection molding. excessive or premature wear at the parting line. In a weld line, reinforcement fibers. Bead Blasting. Meld and knit lines are actually both different types of weld lines. When the temperature is not very high, there are chances of premature solidification, which can cause weld lines to form. For this study, a special injection mold was designed and constructed (Figure 1) in order to produce specimens of various thicknesses (from 2 to 6 mm). 040 and 0. ABOUT THE AUTHOR. While knit lines can be present it does not always mean the structural integrity of the plastic part is compromised. Let’s stop for a second and think about the logos we usually see on a daily basis. Notched weld lines then remain near the cavity walls. Crossref. Weld lines typically appear in a part when an obstruction of some kind separates the melt flow and prevents it from "knitting" together. Circular Loom Machine; Raschel Knitting Machines; Shade Net Making Machinery; Inspection Machines; Non Woven Production Line. In spite of its cosmetic attributes, a bad knit line can significantly compromise a part. The chart below shows recommended wall thicknesses for common injection molding resins. During injection, support pillars keep closed the two halves of the plastic injection mold. Increase the injection speed. Snake Lines: The appearance of snake lines is caused by the formation of a jet effect as the melt travels through a gate and into the mold cavity. In this case it would be 0. 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. For fiber-glass reinforced thermoplastics, the strength in these local areas (knit/weld and meld lines) is less than in bulk areas, dueMolding 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 adhesiveThe best option once you have the approximate tonnage required is to find a molding partner that has machines in that range. incomplete filling or shorts. Knit lines in injection molding are common defects of the molded parts. Swirling can increase depending on the material you use, and the texture or polish of injection molding tools. Excessive mould lubricant. A knit line may only be a cosmetic issue and affect. Know about the cause of these lines and the potential solutions. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. 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. com. Comprehensive. Therefore, with the cooling process, the resin in the central part shrinks and expands to the surface, resulting in insufficient filling in the central part, which is called vacuum. The parting line will always be visible, but can be minimized by its location, draft allowance and part geometry. 156 x 1. 11) The part design must take into account possible knit line locations and work to direct them away from higher stress areas. Islyn Thomas summarized the need for a particular vent location better than I ever could. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. Learn more. Injection moulding is a manufacturing process that melts, injects and sets plastic into a metal mould. Highly ScalableVacuum on the mold does help and many times eliminates the weld line. Anisotropy. Our goal of 100% efficiency, zero scrap and repeatable processes can sometimes be hindered by poor setups or changes in the molding process. Injection molding is a simple and efficient process that produces high-quality plastic parts. Still, they are almost always a cosmetic issue. 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. As these flow fronts come together. An injection mold that produces pieces while the final tool is being built. Circular Loom Machine; Raschel Knitting Machines; Shade Net Making Machinery; Inspection Machines; Non Woven Production Line. com Three terms that often get mixed up in injection molding are weld, meld and knit lines. They again get resolidified along the surface. Temperature is another factor that can cause weld or knit lines in injection molding. 3,000 ton machines can cost $700,000. Soft metals, such as aluminum and beryllium copper, can be used for prototype<br />. The process parameters were fixed as follows: Packing pressure of 40 MPa, injection time of 2. Too cool a melt. Since the intention is to preserve fiber length in LFRTs by reducing. 1016/0254-0584(86)90019-2 Corpus ID: 136712450; Impact strength of knit-lines in injection moulded parts @article{Criens1986ImpactSO, title={Impact strength of knit-lines in injection moulded parts}, author={R. In the process of injection molding, when the wall thickness of the product is large, the cooling speed of the outer surface is faster than that of the central part. They are formed when two or more flow frontINJECTION MOLDING GUIDE V2. You can avoid knit lines and other problems by creating designs with smooth geometries. Mold analysis tools are used by designers of molded plastic parts and by designers of the mold tools used to manufacture those parts. Meld and knit lines are actually both different types of weld lines. Effect of Injection Moulding Conditions on Knit-line Formation, Plastics Rubber Processing and. This course outlines mold filling and how different gating configurations affect filling. But add 30% glass and weld-line strength retention drops to only 34% as high as the compound with no weld line. plastic recycling machine, blown film extruder, filament extrusion line, injection molding machine, blow molding machine, injection blow molding machine, bag making machine, flexo. the thin blades. Bad habits can cause many different problems with injection molding machines, and flow lines are included in that. Nicolet Plastics LLC. Overall, injection molding is a relatively simple process. Be wary of saving too much weight or you might end up with: cracking. Increasing injection speed. Knit Lines and Resins A knit line is any line, visible or not, where two resin flows meet (see Figure 2). Injection Molding Problems and Solutions (17/17) – Weld or Knit Lines Sep 27, 2022What is copper electrode in injection mold? hashtag#plasticinjectionmold hashtag#moldmaking "Copper electrode," also known as "electrode," is a common component in mold manufacturing. The depth of the texture or letters is somewhat limited, and extra draftInjection molding tool design and build for complex parts, with precision tooling and molding capabilities for industries demanding high-quality, critical components. For over four decades, our experienced team and leading edge technology have provided you with tooling solutions from start to finish. Fewer knit lines are produced and a smaller amount of fiber-length degradation is noticeable when compared to injection molding. The injection molding design process, much like all industrial design processes, deals primarily with the creation, look, and feel of a product. 6 Monate. If I can answer any questions you may have on optimizing the plastic part design, CNC plastic prototype, mold manufacturing, and injection molding or if I can be of any other help, please feel. Polypropylene can be processed over a wide range of mold temperatures; however, for applications where aesthetics are critical, a surface temperature of 80-95˚CSink Marks Cause 1: Incorrect Melt Temperature. Common causes of flashing in injection moulding. They occur when melt flow fronts collide in a mold cavity. When venting stationary inserts or core pins in rib or part details with venting issues, I recommend no more than 0. If you need injection molding expertise, we’re here to help. 5 inches) dispersed throughout the structural automotive sub frame component ( 10 ). For. An injection molding machine having a first mold portion and a second mold portion. 3—Another issue with the four-gate design was that knit lines ended on or near mounting holes, causing a. 1. Swirling can increase depending on the material you use, and the texture or polish of injection molding tools. matte or smooth texture on the part’s surface gives a more desirable aesthetic and hides small imperfections such as knit lines, flow lines, shadow marks, and sink marks that were caused by the mold. 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. Remove holes if possible. Typically, injection molded parts will be between 0. Also discussed are weld and meld lines and their effects on molded. menu. Find out more by calling 573-437-4154 today or email us. These defects are not visible, like small. The injection molding was carried out in a DK-Codim 175/410 injection molding machine. Proper mold cooling can eliminate warp, decrease cycle times, and increase part quality. and to identify potential knit lines. Misra A. A screw-type plunger forces the material into a heated chambe r,. They occur when two resin flows meet at different. 030- to 0. For example, warping, sink marks, drag marks, and knit lines can all impact the visual appeal of the manufactured part. The thickness of the part plays an important role in how difficult the molding process will be. สาเหตุรองของการเกิดปัญหาการเกิดประกายเงิน (silver streak) 1. Solution: People. The mold maker may think that some minor defects are acceptable, or they may not even consider them from the beginning, which can cause problems when the injection mold is being manufactured. Vacuum. 3. A meld line occurs when two moving melt fronts converge and flow parallel to each other. Based on the resin. On this page you will find the online, condensed version of this guide, offering quick answers to your injection molding questions. Knit Line occurs where different flow fronts of material meet while flowing through the mold. The most common location of knit line formation is behind molded-in holes that are made by core pins in the mold. The plastic melt that passes through the gate at high speed directly enters the cavity, then contacts the surface of the cavity to solidify, and then is pushed by the subsequent plastic melt, leaving traces of meandering. CAUSE: 1. When injection molding complex parts, often knit-lines are formed during the mold filling stage. [email protected] 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. One common problem that occurs in injection molding is the formation of knit lines. When assessing issues with injection molded parts, we want to make sure some core aspects of molding are checked. 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. Take these steps to avoid knit lines. Kaminski, in Specialized Molding Techniques,. suppressed cooling and possibly warp. 827 Holes and Bosses. Specifically, by having a single, continuous injection outlet 140, molding material can be uniformly distributed throughout mold cavity 120 quickly and consistently without resulting in undesirable molding seams or knit lines. This is easier to accomplish on. Release of trapped air in those cases will. To ensure quality parts, injection molding companies must have the best injection mold design first + (91) 96067-70777 +(971) 547-161-112. Flow Lines. S. Also known as “stitch lines” or “weld lines”. Incompletely fused extrusion knit Line. [8] Bevis, MJ, Reis RL, Cunha AM. “A knit line in a colored part will result in glaring visual-effect problems, while a knit through a glass-filled part would have a negative effect on both the aesthetics and the performance,” agrees Kurt Weiss, manager of part performance and new material introductions at GE Plastics. 3 To get the most out of your Xometry Injection Molding experience, we offer the following part Design Guide with. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. The total amount of scrap being produced during injection molding will usually be higher than that for compression molding because of the additional material loss created. They again get resolidified along the surface. Knit lines, also known as weld lines, are fine lines that resemble hairline fractures or cracks. A thermoplastic resin is heated to its melting point and injected into the cavity of an injection mold to produce a specific part geometry. 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. 7. There needs to be a balance between fit of the halves, function of the part, visual quality expectations, and the cost to produce the mold. 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. He is currently a tooling manager for a large, multi-plant molding and manufacturing company. CURE: Run the mold in. Knit lines form during the injection molding process when two resin flows meet. A knit line is what happens when plastic flows coming from two different directions meet inside of the mold and solidify. We complete the part to your precise specifications with CNC Milling operations. For example, increasing gate size can improve part filling. 040-in. 3. Mold Flow Analysis computer. Meld and knit lines are actually both different types of weld lines. There. The defect may be in part appearance or mechanical strength. With ABS injection molding, you get the collective benefits and properties of three monomers. Alter the mold design. Material contamination, for example, can cause several molding issues. Plastic melt and mold temperature. Weld lines defects can also form when the flow fronts from two gates merge or when thick and thin sections in a part cause a flow to split and merge. 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. As a result, molten plastic takes the injection mold core and cavity shape. The relationship between processing conditions, morphological structure and mechanical properties of knit lines of an injection molded semi-crystalline thermoplastic. Many materials can be. When assessing issues with injection molded parts, we want to make sure some core aspects of molding are checked. This picture shows a. Having uniform wall thickness makes it possible for the melted plastic to fill the mold evenly, therefore not creating a part with warp, sink, thin knit lines, or other defects. Using restrictors helps push visible knit lines into less conspicuous areas. These knit-lines are well-known as particularly critical regions in the mold when mechanically loaded. Part Shorts and has burn marks. Causes 1. The adverse effect of knit-line formation on the mechanical properties of thermoplastics has been well documented for unfilled materials. Venting. Bad habits can cause many different problems with injection molding machines, and flow lines are included in that. 18/06/2021. Avoid adding threads directly on your injection molded part. 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. . They are the result of fundamental physical effects taking place inside of the mold. Learn how to troubleshoot weld lines in injection molding. The recommended minimum production volume for injection molding is 500 units. Runner and gates must be balanced. As the polymer resin is injected into a mold, it flows through all parts of the mold. Cold weld line or known as “knit line” isWeld Line defect analysis, the most common of many defects in injection moulding products. When venting stationary inserts or core pins in rib or part details with venting issues, I recommend no more than 0. If the part design’s wall thickness is constant, the magnitude of the plastic’s velocity will be the same at every. injection molding. Koelling, Ronald C. In injection molding, it is often important to maintain consistent color throughout the part. Weld / Knit Lines; Assumptions. Most failures of injection molded plastic parts are caused by either improper design of the part or improper design of the mold. More about the knit lines in injection molding. The knit line itself (the vertical line in the middle) is visible in this lighting, but the biggest issue is with the texture. 6. 4. Redesign the mold: Redesigning the mold to. For instance, three widely used processes are insert molding, overmolding, and undercuts. This slight depression is a tiny line called the weld line or knit line. Knit lines. How to Eliminate Knit Lines In Injection Molding - Xcentric Mold Want to learn how to eliminate knit lines that form during the injection molding process? Then. The effect of holding variables and of injection and mould temperature was explored. Depending on the design of the mould and the material being injected, a knit line may: present no problem at all, be a cosmetic issue, or cause a potentially. Reduce the temperature of the mold and plastic being injected. H-13 Good general purpose tool steel. This defect is caused from excessive lube or oily stock. In places where the plastic flows around a solid piece of the mold, from a simple circle to forming complex shapes like rings or squares. SPI surface finishes are the most common set of injection molding finishing standards around the world with over 12 different grades. Finally, knit lines occur when molten plastic flows around an object and rejoins on the far side, a phenomenon that is quite possible when inserts. A knit line, also. Flow Lines Knit or Weld Lines Cavity Gates Table 1 Knit line in a multi-injection-point cavity. In a plastic injection-molded component, a knit line occurs when 2 different plastic flows emerge in a mold. The wall thicknesses of an injection molded part generally range from 2mm – 4mm (0. 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. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. 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. Criens}, journal={Materials Chemistry and Physics}, year={1986}, volume={14}, pages={69-83} }A structural automotive sub frame component ( 10 ) that is formed from a sheet molding compound having carbon fibers. Bubbles are caused by melting flow fronts colliding in a mold cavity. Part Shorts No burn marks. Below is a list of items that should be checked both during normal molding operations and if defects are detected. More about the knit lines in injection molding. Consider adding mold release (can be added to the polymer itself by the polymer vendor) or at machine side Knit lines Weak knit lines Increase melt temperature Mold temperature too cold Increase injection speed Avoid nucleated products if possible Inadequate ventingWhat you should know is that there are various failure modes for injection molding. 060 and 0. Injection molded plastic begins its journey through the part tooling via an entry section called a. "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. Injection molding is a popular manufacturing process used to fabricate parts in large volumes. While injection molding itself is a straightforward process involving melting thermoplastic resin and injecting it into a mold cavity, knit lines can pose. 3 /sec of material into a mold, don’t think the material is going into each cavity of a multi-cavity mold at the same 14. Injection molding is the cost-effective method and is best suited for higher volumes. Get a free des. The specimens with a weld line at the center were obtained by double gate molding and the specimens without a weld line wereTherefore, 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. TEFABLOC™ TESI 744 TPE compound for injection molding processing provides superior adhesion properties when processed using injection molding. 5-3. . 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. From the start of your project, you can count on The Toolroom to exceed your expectations for all of your plastic injection molding needs. Knit lines, also called parting lines, are any lines where two resin flows meet and may or may not be visible. Weld lines are a common imperfection to be found in most plastic injected molded parts. The part is cooled in the mold until it is solid enough to be ejected. Once the mold is created and the machine is set up, additional parts can be manufactured very fast and at a very low cost. Polym Compos 1982; 3: 88–96. Example of a gate location in a finished part Example of knit lines in a finished part. Learn Injection Molding Glossary with Plastopia: Using actual molded parts (with images) as examples. Description: Flow lines are streaks, patterns, or lines - commonly off-toned in color - that show up on the prototype part as a consequence of the physical path and cooling profile of the molten plastic as it flows into the injection mold tooling cavity. They are formed downstream through holes, and between multiple gate locations. Back to News Page. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. Plastic melt and mold temperature. Additionally. If the load is applied in the transverse direction relative to the knit line, matrix cracking is easily initiated, and the part can fail. In places where the plastic flows around a solid piece of the mold, from a simple circle to forming complex shapes like rings or squares. The Fusion of Weld Lines. Recommended for the bonding of nylon (polyamide) and polypropylene materials, this thermoplastic elastomer delivers wide compatibility and thermal stability, allowing for use in demanding conditions. Final Report-Plastic Injection Molding - Free download as Word Doc (. Mold cores can be machined from a solid piece of copper alloy or inserted to aid in construction or allow for easier replacement if a com-ponent would ever be damaged in molding. Parting lines placed at intricate joints. Raising the mold temperature will keep the material molten longer, resulting in stronger weld lines and even elimination of weld lines. Submarine Gates. 120 in. Injection molding is a plastic manufacturing process to achieve a high production rate. Poor Knit Lines. The main causes of Weld Line or Knit lines are: Convergence of two flowing polymer melt streams during injection molding process: This is the most common cause of weld lines, as the two melt streams coming from different runners or gates in the mold meet and do not fully mix, creating a weak point in the finished product. 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. Thermoplastic Elastomer Molding Guidelines. Learn how HPP maximizes these specialized processes. Prevent Flow and Knit Lines Through Mold Adjustments. A poor knit line can cause cosmetic blemishes and significantly weaken the structural integrity of a part. A poor knit line can cause only cosmetic blemishes or it can significantly weaken the structural integrity of a part. The uneven thickness of the product will make the melt flow resistance larger and smaller, resulting in unstable melt flow. 2. Plastic injection molding is a process where a thermoplastic resin is heated to its melting point and injected into the cavity of an injection mold. To account for variations in viscosity, nylon injection molding machines need to maintain an appropriate injection pressure. There are times when porous materials like Porcerax are used in problem or backfill areas. Inadequate injection pressure can result in knit lines and a surface that. 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. Exploring common molding defects and. 0mm) throughout will ensure that the parts cool evenly and will prevent warping. 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. The last cause of flow lines may be the operators running your daily operations. Using three test materials, polystyrene (PS), polycarbonate (PC) and polyoxymethylene (POM), the relationship between a design and a processing parameter and the effects of the knit-lines on the tensile properties of injection molded plates. Adding draft or slope to vertical walls of a part makes it easier to eject or remove the part from the mold. The melt is forced to split up during filling of the cavity. He is currently a tooling manager for a large, multi-plant molding and manufacturing company. Such molds or tools aren’t intended to be used in operation. Sink Marks Cause 3: Improper Pack or Hold Pressure. 1050 Walnut Ridge Drive. This article looks at the issues presented by a weld line in injection molding and the techniques manufacturers can use to avoid them. Cooling Lines, Injection Mold Material has a great impact on injection molded part quality. Notched weld lines then remain near the cavity walls. Add a 0. Plastic injection molding has long been an affordable and efficient process for producing custom prototypes and end-use production parts. 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. 2. Injection molding is capable of producing a lot of aesthetic options as well. Weld lines are formed when there is an inability of two or more flow fronts to ‘knit’ or ‘weld,’ together during the molding process. Over the years, I have developed two separate “5M” systems. The injection molding machine includes a fluid path extending through the first mold portion. Macromol Symp 1988;21/21: 489-500. Injection moulding (U. POROUS MOLD MATERIALS. Undercuts add cost to tooling and molding, which is recommended to eliminate or minimize as possible. 197 in. Tooling & Injection Molding Services High-Quality Complex Parts. This information is intended to be used only as a guideline for designers and processors of modified thermoplastics for injection molding. A weld or meld line is a weakness or visible. 060 and 0. The diameter of the secondary runner would be the diameter of the tertiary runner times the number of branches to the 1/3 power (cube root). The structural stability of. (knit) line and produces a latent, or obvious, part defect. These knit lines are usually the weakest areas of the part. As. These flaws can affect the aesthetic and structural integrity of the. Anisotropy. 120 in. Some. Knit line / Meld. In this way, the mold supports distribute the force and minimize the stresses on the mold plates. 2. Increase the injection speed. It can be determined by a visible line appearing on the surface of the plastic part where two flows of the plastic meet. POROUS MOLD MATERIALS. The difference between a knit and meld line is significant, dramatically impacting the part’s structural integrity. They have their origins in material choice, part design, tooling, and processingIn the injection molding process, knit lines are a common occurrence when two or more plastic flow fronts collide and solidify, resulting in a visible seam or line on the molded part. On a hydraulic machine you can program hold pressure: For example, if you set 850 psi (59 bar), you will get 850 psi hold pressure for the time you set on. 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. There are two primary reasons for this occurrence: 1. Holes in the part will always cause knit lines. The Mold Tools toolbar provides tools for creating mold tooling (cores, cavities, etc. I am working on a thin PC/ASA injection moulded component which has a tendency to snap at the Knit-point (the final point of travel at which the…Here are a few of the most common defects that may occur in plastic injection molding — and how product teams can avoid them. Resin cools as it is injected into a mold. Weld Line Phenomenon: Surface defect in which the weld, or the part where the flows of melted plastic meet inside the mold, shows up on the surface as a groove or pattern. 120 in. Kurt W. 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 is caused by the incomplete joining of the uncured. No matter the size of a production run, the presence of blemishes on the finished product leads to unhappy clients. It tells them that you visualized how injection molded parts cool and harden. Generally all plastic components should be designed with draft where possible. Injection speed and pressure. PAPER ABSTRACT: Desktop injection molding machines and stereolithographic print ed molds make hands-on injection molding production possible in design studio classrooms and labs. However, compression molding often provides poor product consistency and difficulty in controlling flashing, and it is not suitable for some types of parts. 1 in. DOI: 10. 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. 5. Knit lines, holes, part configuration and the talent of your molder all come into play. Direct experience designing molds and parts for injection molding and producing the molds and parts is valuable, relevant experience for design students. A wide variety of tool steels are available for injection mold construction. Weld lines, also known as knit lines or meld lines, occur when two or more flow fronts meet during the plastic injection molding process. wall thickness, knit lines, draft. Knit/Weld Lines. Part thickness control is through stacking of. 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. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. Crossref. When the mold adopts the multi-gate pouring scheme, the plastic melt.