Weld lines are formed when two melt fronts come in contact with each other. The flow disruptor is a small insert introduced inside the injection molding cavity, in the weld line area, and its objective is to mix the melt and disrupt fountain flow in order to blur and. box, along the region of weld line formation (wc, wm, we and wl) and away from the weld line, in a radial position along the flow direction (R), as shown in Figure 2. Remember, by avoiding weld lines, you can lessen operations cost. Flow-induced filler orientation and weld lines are un-avoidable facets of the injection molding process. 1. For the production of these weld‐line specimens, a special mold was used and injection molding parameters were systematically varied, tensile (ISO 527‐2) and impact (ISO 179‐1/1eU. 22 shows how the weld lines are formed when the melt splits around core pins during the injection molding process. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. Furthermore, injection molding was applied by filling these pellets into a micro-injection molding machine (C. Additionally, you can get our free Design Cube, which will provide a physical aid to help understand how knit lines form as well as other injection molding design considerations. He now teaches courses in injection molding and plastic part design at the Polymers Center of Excellence and UNC-Charlotte in Charlotte, N. The injection molding process can be optimized to maximize weld line strength by increasing. In this study, the effects of injection temperature, injection pressure, and fiber cont. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. 000 0. This remains as a challenge for control engineers. High-density PE was also moulded in the same conditions but in a lower temperature range (145 to 220°C). Meld and knit lines are actually both different types of weld lines. This article will introduce you the usage, types, and advantages of the Sequence Injection Timer. Adding vents, using overflows, or using porous metal. This study addresses the effects of injection molding weld line on the fatigue crack resistance of commercial CPVC in the temperature range of −10 to 70 °C. The impact behavior of weld-lines in injection molding. Gate blush, 4. C. But none of the current packages can predict weld lines’ properties qualitatively. 1 Prediction of weld lines with injection molding simulation softwareWeld lines in design for manufacture. 020 0. open access Abstract Micro weld lines are the common problem that occurs for plastic molded parts through injection molding process. In injection molding, it is often important to maintain consistent color throughout the part. Alloys. Just check out some of it on the above lists. Steven. 5. Weld lines occur when melt flow fronts meet during the injection molding of plastic parts. Additionally, you can get our free Design Cube, which will provide a physical aid to help understand how knit lines form as well as other injection molding design considerations. To prevent weld lines, increase the pressure and temperature. If it only affects the appearance, it can change the position of the burn four to change the position of the weld line. Burn Marks. The weld lines that occur in injection mouldings are critical areas on which depends on the strength of the mouldings. Adjust Injection Molding Parameters: Optimizing injection speed, pressure, and temperature can help ensure better melt flow and reduce the likelihood of weld line formation. The weld line length was selected as part of the quality index to investigate the effects of gate location on weld. In narrow fields, a limited amount of molten liquid can solidify and block the flow. This is expected to achieve maximum results while the pressure holding effect will also increase. If there’s too much mold release, you may require a higher pressure to push it through the machine. Weld lines can be caused by many reasons, which covers the various aspects of mold, process, raw materials and product design, etc. Stagnant weld lines are formed when melt streams meet head-on. In an injection molding process, a weld-line forms when two flow fronts meet each other. Plastic part design for injection molding – An introduction. Causes. 2017-01-0481. Introduction. This type of injection molding resolves any trouble caused by undesired welding lines. In the plastic injection molding industry, we work with materials that are byproducts of oil refinement and molds made of metal casting, so our terminology is bound to be at least slightly confusing. These flow fronts occur when the molten plastic material encounters obstacles, such as inserts, ribs, or other features within the mold cavity. As a result this. Unless you are manufacturing an extremely simple part with one gate and a unidirectional flow front, your part will have weld lines. Investigate for potential contamination. A weld line is a mark left on the surface of a plastic injected molded part. Technol. 3 and 53. Save. The effects of fiber concentration has been studied in detail. For glass-filled grades, the thickness at the weld line can be slightly larger than the nominal value due to lower shrinkage associated with vertical fiber orientation at the weld line cross. when two or more melt flow fronts contact each other immediately after the cooling process. These are preferred over weld lines as they will normally result in improved cosmetics and structure. Adjust the design for the flow pattern to be a single source flow. With Ixef® PARA compounds, the strength of a weld line is typically 90 MPa (13,000 psi). When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. In our DFM report, we will analyze the possible weld lines. 5. Figure 1a illustrates how the weld line is produced when two melt streams merge during the final filling process. Fig. This gives a clue as to. The weld line in injection molding is created when two melt streams connect, as shown in Figure 1. Examples of such failure are shown in Figure 1. Crack growth behavior. examined the relationship between the structural and mechanical qualities in HDPE/PA6 mixture which is molded with weld line and without weld line in plastic injections [6]. 025 100 120 140 160 180 200 220 240 Mold Temperature (F) LDPE PPEffects of mold temperature and pressure on shrinkage 0. Re-balancing entire manufacturing lines may be required to effectively deliver and sustain SMED excellence. 809-814. This paper analyzes production data from injection molding processes to identify key interactions between the process variables from different material categories using the network inference method called “bagging conservative causal core network” (BC3net). Weld line strength vs. Wang, G. The Factors that Cause Weld Line in Injection molding Pressure. In the RHCM, the mold temperature profile plays a crucial. Shaofei Jiang. 2021年4月23日 / by admin. They decrease the. Xie L, Zhu D, Ziegmann G, Steuernagel L (2016) Investigation on correlation between cold/hot weld line mechanical properties and micro injection molding processing parameters. Weld line injection molding troubleshooting. The present work focuses on studying the effect of packing pressure on strength of stagnation weld-line. 0 mm, is designed to conduct the. Increase the injection speed to reduce the amount of cooling happening in the mold. 6. Low mold temperatures are usually employed to decrease cycle molding time and final process costs; however, resulting surface defects include weld lines, sink. 005 0. Weld line formation in the injection molding process occurs. Weld-line is a weak area which reduces the strength of the part locally. As the weld line can significantly lower the mechanical strength of µIM parts, it is relevant to clarify the position of weld. 3. Figure 2. This injection molding defect appears as a black discoloration on the surface of the molded part. The terahertz time-domain spectroscopy (THz-TDS) imaging technique was used to detect the weld line defect of an injection-moulded short glass fiber-reinforced composite. II. 4. Venting at Weld Lines. This reduced thickness of the frozen skin further enhances the visual appeal of the. Many researchers had emerged with several. Tekanan yang kurang mampu untuk mendorong aliran dan kembali pada posisi semula dapat menimbulkan weld line. Gate position in injection mold. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. The gate vestige for injection molding is usually narrow. There are several possible causes that need to be investigated to troubleshoot weld lines in injection molding. Poor weld line quality can lead to short-term or long-term product failures, initiated at the weld line. Weld lines in injection molding are a type of cosmetic defect that detracts from a plastic part’s appearance. Effects of cavity surface temperature on mechanical properties of specimens with and without a weld line in rapid heat cycle. Thus, it is important to understand (i) if the melt is able to fill the cavity up to the weld line location, (ii) where the weld line forms, and (iii) if the weld line is a cold or flowing one. Weld lines are a common defect generated in injection molding, which apparently affects the performance of final products, but the available reports on carbon fiber-reinforced thermoplastics are. During the plastic injection molding process, one of the biggest challenges is. In this mold, a visualization design and a rapid heating/cooling system were integrated, and specimens with different cross section. Sink marks, 2. The Solutions for Poor Welding Lines. Minimize the use of release agent. Weld or knit lines result wherever two or more polymer flow fronts unite. Weld lines can appear on the components when the molten plastics meet each other as they are flowing from two different parts of the mold. • Reduce runner dimensions and maintain the same flow rate. The cracking was always located in the weld/knit line and therefore caused by weakness in the bonding of the plastic at. Problem: Weld lines are formed when plastic resin is forced around an obstruction in a mold tool and reforms on the side opposite the gate. Here we are looking at most common part defect that can come from injection molding called weld line. Redesign the mold to prevent the weld line. The weld line’s strength is reduced when. The injection molding gate generates heat by dissipation. Recently, injection molding process has generated growing interest, exhibiting great potential to easily fabricate unique polymeric materials for industrial applications. Weld line (also known as a knit 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. ). In injection molding weld lines are formed whenever two flow fronts are joined. oped which factors the weld lines into the virtual design of chopped-strand-rein-forced thermoplastic parts. The possibility of the functional thin film for. Sink Marks Cause 1: Incorrect Melt Temperature. + Adjust injection speed. The results showed that the tensile strength of PE remains unchanged in the presence of weld lines. But the unfavorable and unavoidable defect of weld line in micro injection molding part leads to detrimental mechanical and surface properties. In this study the polycarbonate (PC) and carbon fiber (CF) are used as the experimental materials to investigate the impact of injection molding process parameters on tensile strength of weld line. (1)Injection Machine Poor plasticization and non-uniform melt temperature – appropriately extend the injection molding cycle, to ensure thorough plasticization, and change for a machine with a larger. 2-1. Its appearance can be improved by adjusting parameters. Again, consult with professionals as to how you could improve mold designs. Islyn Thomas summarized the need for a particular vent location better than I ever could. Remedies: Raise the temperature of the mold or molten plastic. The formation of weld line in the injection molding method is caused by the product and mold design that is one of the common mistakes. Increase the melting temperature. <Mold> Increase (or decrease) the size of the runners and gates. Weld lines, also known as knit lines, are a common defect in injection molding where two or more flow fronts of molten plastic meet but don’t properly fuse together. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. That’s the air escaping out of the nozzle until the hose is full of pressurized water. Try to gradually raise the mold temperature and barrel temperature. Weld line and warping are two critical defects for injection-moulded part. Flash. In this case the two flow fronts will meet and there will be very little molecular orientation across the weld. From: Polylactic Acid (Second Edition), 2019. % glass fibers – PA6 Aramid SV 30-1ETM (figure 1b). Although they often cannot be avoided it’s possible to minimize their cosmetic effects to an acceptable degree through careful product design and. Conclusion The formation of weld lines in micro injection molding of plastic depends on different parameters such as melt temperature, injection pressure and fabrication method. Procedia Mater Sci 2014; 3: 2048–2053. ac. 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. Weld line Weld line dikatakan ketika dua atau lebih aliran lelehan depan. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. Clamping Unit. Abstract. * Corresponding author, e-mail: [email protected] an injection molding process, a weld-line forms when two flow fronts meet each other. Raising the mold temperature will keep the material molten longer, resulting in stronger weld lines and even elimination of weld lines. “I realized weld -line problems are a very common issue for injection molded parts,” Nicholson told Plastics Technology. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. Instead, a line that looks like a seam forms. 1% higher than the ones without ultrasonic assistant, which indicates that the weld line strength in micro injection molding can be well reinforced by the ultrasonic oscillation due to the fact that ultrasonic oscillation induces better diffusion among the melting. They found that the weld line is a zone between 2 and 8 mm wide extending throughout the thickness in whichTo investigate the effect of hot gas heating in injection molding on the weld line appearance, an experiment was conducted with the molding parameters listed in Table 2. 4If the injection gate is not properly designed, it can cause the formation of defects like sink-mark, warpage, short shot, weld-line, air traps, and other faults [15]. 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 are a common imperfection to be found in most plastic injected molded parts. . The weld line and the flow pattern of co-injection molding can be seen from Fig. That helps. Part design features may cause a material flow to split and rejoin as it flows around design features in a mold. A weld line can appear during the absence of enough pressure to push the plastic flow and then meld. Weld Line Factors for Thermoplastics. Change the gate locations. Gava and co-workers implemented an investigation devoted to the de-weld lines in injection molded thermoplastic composites. These are caused by the shot of molten plastic moving at different speeds throughout the injection. (1) make the mold vent larger at location with weld line; (2) Check if the mold vent is blocked or not or use vacuumized forming. The effects of filling time, packing time, packing pressure, melt temperature, and mold temperature on the ultimate tensile strength (UTS) and the elongation value of the weld. The line where two resin flows “knit” or “weld” together during injection molding is called a weld or knit line. According to the characteristics. Weld lines occur when melt flow fronts meet during the injection molding of plastic parts. 2017-01-0481. 5. Thoroughly clean molding machine cylinders. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. Molding with weld line model Moldex3D was used for calculate the molding of lugs (figure 1). Figure 1 below shows the development of a weld line. Lesson 6: Meld and Weld Lines (Processing) When plastic flows into an injection mold, the internal flow pattern depends on the part design, mold design, and processing factors. These potential causes include: Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. (2) Causes & Countermeasures (See the table below) *Note: Flash also tends to occur when the injection pressure/speed are too high, but molding time is too long and mold temperature is too low. Nguyen-Chung. This failure causes the product to be damaged during use. NX Mold Flow Analysis. Weld line formation in the injection molding process occurs when two or more melt flow fronts contact each other immediately after the cooling process. Sink Marks Cause 3: Improper Pack or Hold Pressure. The following are the conclusion drawn from the present research: 1. Mobile 0813; Shinko Sellbic Co. 025 100 120 140 160 180 200 220 240 Mold Temperature (F) LDPE PPAbstract. Because of the ever-increasing requirements for parts performance, lots of researchers have perf. The effects of these two injection molding process parameters are explained in terms of their influence on the skin-core morphology observed on the fracture surfaces in the weld zone. 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. The impact behavior of weld-lines in injection molding. One of the factors that determines the quality of injection molded parts is the weld line [50,75,76]. In spite of the symmetry of the molding the formed weld line was not straight, due to a slight unbalance of the two injection gates. 1, right). The parting line in injection molding is which one of the following: (a) the lines formed where polymer melt meets after flowing around a core in the mold, (b) the narrow gate sections where the parts are separated from the runner, (c) where the clamping unit is joined to the injection unit in the molding machine, or (d) where the two mold halves come. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Emerging Materials Research. This can allow the. 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. This will produce parts with aExperimental results show that the weld-line strength from a standard test is not applicable in microinjection molding. A quantitative evaluation of the appearance quality of weld lines in RHCM parts. Weld line is one of the plastic injection molding defects. In injection molding, it is often important to maintain consistent color throughout the part. 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. Except for a few very simple injection molded parts, they occur on most injection molded parts (typically in the form of a line or V-groove), especially large complex items that require use of multi-gate molds and inserts. When two or more strands of molten plastics meet in the mold, a weld line will be produced at the junction [1,2]. The weld lines in injection moulded parts arise as a result of the collision of two fronts of the flowing material, which fills the mould cavity and are sometimes unavoidable. Injection molding is a manufacturing process that involves injecting molten plastic into a mold cavity to create a specific shape or design. Second, depending on the size of the overflow well, you get a little bit of flow melding together, and that helps strength so that you have some intertwining of the polymer chains. Figure 1 below shows the development of a weld line. technical ulletin SPECIALTY POLYME RS Design and Production of Injection Molding ToolsWeld lines have been one of the common defects puzzling the injection molding industry. Figure 2. Meld and knit lines are actually both different types of weld lines. The appearance quality of plastic parts in weld lines can be improved significantly through the rapid heating cycle molding (RHCM). This leads to a better molecular chain entanglement, which in turn creates a better weld. In an injection molding process, a weld-line forms when two flow fronts meet each other. Improper fusion of two fluid flows, a state before weld line. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Known also as knit lines and weld marks, weld lines are difficult to eliminate completely, especially if your injection molded part requires holes. Melt temperature does effect the weld. Weld lines appear on the surface of a molded part where the molten material converges after splitting off into two or more directions in a mold. Here is a look at the differences between them, the causes of meld and knit line imperfections, and their impact on part durability. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. For multiple gate and complex part. Adjust the position of the gate and include a venting slot. (1)Injection Machine Poor plasticization and non-uniform melt temperature – appropriately extend the injection molding cycle, to ensure thorough plasticization, and change for a machine with a larger. Kondisi ini juga bisa menandakan bahwa mesin injection. This paper presents the. [8,9] It is capable of. The welding angle can be used to differentiate weld lines and meld lines. Known also as knit lines and. As a defect of micro injection molding parts, weld line is unfavorable since it will influence the surface quality and mechanical properties of micro parts. ABS is a commonly used plastic in injection molding due to its excellent mechanical properties and chemical resistance. As the injection process continues, the two separated melt fronts meet again along the longitudinal section of the plate forming a weld line. Miron MC, Major Z, Adachi T. 3 Materials Polypropylene (PP) and. Many works deal with weld lines and their dependence on processing parameters for conventional injection molding, but only a few works focus on the weld line in µIM. Silver Streak. (2011) and Fig. Thus, it is important to understand (i). C. 3 cc/sec, the weld lines are no longer perceivable above 130 C. Fiber content dependence on. reinforcement type and amount in nylon 6/6. Weld-line is a weak area which reduces the strength of the part locally. g. Plastic part design for injection molding – An introduction. Weld lines not only detract from an injection-molded part’s surface quality, but also significantly reduce its mechanical strength. Flow analysis of the weld line formation during injection mold filling of thermoplastics. 1007/s00397-003-0339-2 ORIGINAL CONTRIBUTIONCauses and Remedies of Sink Marks In Injection Molding. Injection molding plate for mode I testing geometry. Procedia Mater Sci 2014; 3: 2048–2053. The. Insufficient plasticizing ability of injection molding machine. Miron MC, Major Z, Adachi T. Visualization analysis of flow behavior during weld-line formation in injection molding process. Materials Science. If not, the speed will drop, and it could create weld lines. Insufficient injection pressure and speed can cause weld lines. The formation of weld line in the injection molding method is caused by the product and mold design that is one of the common mistakes. Again, consult with professionals as to how you could improve mold designs. 298 µm and the weld line on the heated region was almost eliminated with the aid of induction heating. Therefore, the length of flowing weld lines must be additionally defined. Weld lines have been one of the common defects puzzling the injection molding industry. 3 cc/sec, the weld lines decrease over temperatures up to 150 C, while at higher volumetric injection flow rates of 43. 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. Weld lines in injection molding are frequently unavoidable. For the production of these weld‐line specimens, a special mold was used and injection molding parameters were systematically varied, tensile (ISO 527‐2) and impact (ISO 179‐1/1eU. Try to gradually raise the mold temperature and barrel temperature. 2. Here are a few of the most common defects that may occur in plastic injection molding — and how product teams can avoid them. Weld lines are a common defect generated in injection molding, which apparently affects the performance of final products, but the available reports on carbon fiber-reinforced thermoplastics are still rather few. Injection-molding machine is the Negri Bossi VE210-1700 with screw. If the injection molding speed is too slow, however, there may be an insufficient filling of the mold. The thermo-rheological findings were used to investigate the sources of weld line weakness. Weld lines can be caused by several different problems: Low temperature of injection moulding machine barrel. Poor weld line Ⅰ. If so, look for an alternative resin. injection molding. Penyebab Weld Line. When an external load is applied to a weld line region, the part’s potential for mechanical failure is increased. It is possible to pre. Weld-Line in an injection molded part develops when two or more melt fronts are converged together. สาเหตุรองของการเกิดปัญหาการเกิดประกายเงิน (silver streak) 1. technical ulletin SPECIALTY POLYME RS Design and Production of Injection Molding Tools. Strength measurements should be made to. Injection molding is a complex multi-variable, nonlinear and time-varying unsteady process, which makes it more difficult to optimize the process parameters. Neat polypropylene retains nearly 90% of its strength on a properly designed and molded weld line. Reduce the amount of release agents. The optimum injection molding parameters to manufacture the product was determined by . DescriptionThis insertion ensures the separation of the melt flow. A knit line, also called a weld line, occurs when the liquid plastic moves through the mold and hits more melted plastic and they don’t flow or fuse together. Flow marks in injection molding are defects that manifest as a line or series of lines forming a pattern different in color from the other parts of the molded material. Double push filling method. poor flow fronts that are too cold, this can also lead to a deterioration in the mechanical properties. 2. A weld line develops when two or more flow fronts come together but do not meld completely because of partial solidification. C. This model provides the necessary information. [1] Kobayashi et al. Meddad and Fisa [3] found that the weld line is a zone between 2 and 8 mm wide extending throughout the thickness in which the fibers are oriented almost. Amongst weld line. In recent years new methods for quality prediction and optimization of the injection molding process have been proposed and applied. The weld-lines are undesirable from both aesthetic and functional points of view and their effect is different for varied materials, process conditions, loadings, forms. Gate Placement: Properly positioning the gate can direct the melt flow to minimize weld lines or relocate the weld line to non-visible areas of the part. Despite injection molding being recognized as a robust process for obtaining parts with high geometry accuracy, one last occurrence remains a challenge in micro-injection molding, especially when junctions are. Sequential valve gate technology. Weld lines in injection molding are a type of cosmetic defect that detracts from a plastic part’s appearance. A good weld typically occurs when the melt temperature where the weld line is formed is no more than 20°C below the injection temperature. Compd. อุณหภูมิของพลาสติกเหลวสูงเกินไปจนก๊าซหรือความชื้นแยกตัวออกมาได้. CrossRef View in Scopus Google Scholar [17] G. This study presents an innovative approach to enhancing weld line strength in advanced polymer injection molding through applying gas-assisted mold temperature control, significantly increasing mold temperature beyond typical values observed in conventional processes. Compd. This study focus on the. From Understanding Weld-line Integrity by Sabic Innovative Plastics, p. 2023年1月3日 / by admin. It occupies a major part in the plastics industry ranking second to plastic extrusion in terms of production and the utilization of both thermoplastic and thermosetting plastic materials. Maintain a holding pressure that is no more than 1/2 the. In spite of its cosmetic attributes, a bad knit line can significantly. Polymers 2023, 15, 2440 3 of 21. In the sense that the weld line is better formed before the resin. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection. To determine the effect of the weld lines on tensile strength, tensile tests were conducted with the specimens fabricated with NORYL (amorphous blends of. Park et al. For example, filled resins and ABS are more likely to. How Are They Formed? Molten plastic resin is injected into a mold cavity through an opening known as a gate. The defects encountered could be caused by mechanical factors, such as poor mold design and mold manufacturing, or by processing related factors, such as incomplete kneading, inadequate molding pressure, injection. 3. • Optimize the design of the runner system. In the present study, Moldflow® software is applied to simulate the injection molding of automobile instrument light guide bracket and optimize the injection gate position. Numerical results show that weld lines can be predicted accurately, and the formation and evolution processes of weld line can be shown more clearly by co-injection molding technique. The weld line in injection molding is created when two melt streams connect, as shown in Figure 1. This study focuses on the effect of melt temperature on. This study focuses on the analysis of fill time by optimizing the injection molding parameters to reduce the defects that are always found on the plastics part such as poor weld line and part not. By the reflection method and a high speed camera, the visual system can be used to record and observe the forming process of micro weld lines during the. This paper evaluates the shrinkage and strength of weld line using Design of Experiment and Response Surface Methodology in multi-objective optimisation utilising the injection moulding parameters. J. Weld lines represent the region where two separated melt fronts recombine. To explore the formation of. Insufficient clamp tonnage Increase clamp pressure or move to machine with more tonnage . when two or more melt flow fronts contact each other immediately after the cooling process. Fortunately, there are several. Wolfgang Homes, head of the applications department of Eurotool, a manufacturer of hot runner systems, clarified the two methods for IMI, noting that. It has larger cross-sectional regions that allow sufficient molten plastic flow into the cavity. A weld line is a mark left on the surface of a plastic injected molded part. Polym. Miron MC, Major Z, Adachi T. Injection Molding Glossary; Weld Lines; Weld Lines. 3. Its properties make it possible to create thin-walled parts having close tolerances in fast cycles over long. This customary mark is caused by differential rates of cooling in the resin where.