Weld lines are a kind of Achilles heel of plastics. Re-balancing entire manufacturing lines may be required to effectively deliver and sustain SMED excellence. Fracture behavior of weld lines in injection molded components loaded under real operating conditions. 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. 1. The following are the reasons. 1. Some of the common fixes for weld lines include: Increase the resin temperature to ensure both sides of the weld line are liquid when colliding. S. วัตถุดิบ พลาสติก PMPA ( อะคริลิก ) เกรด A. Plast. To prevent weld lines, increase the pressure and temperature. It is important to investigate the weld line because the weld line area can. Recently, injection molding process has generated growing interest, exhibiting great potential to easily fabricate unique polymeric materials for industrial applications. 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. For thick-walled parts, slow injection rates result in more uniform polymer distribution . This study describes how the weld line was formed on the part. He now teaches courses in injection molding and plastic part design at the Polymers Center of Excellence and UNC-Charlotte in Charlotte, N. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. For example, filled resins and ABS are more likely to. Weld line defects are a common part defect that occurs when the injected plastic flows around a solid piece of the mold and does not knit back together. 9 – Over Packing. This thermal field was transferred to an injection molding flow solver to compare simulations and experimental results from the high speed video, both with and without the effect of induction heating. A weld line region is typically filled at the end of an injection stroke or during the pressure phase. Designers can easily set up and perform analysis with only a few clicks. <Materials> Pre-dry thoroughly. Because of the ever-increasing requirements for parts performance, lots of researchers have perf. The Solutions for Poor Welding Lines. During injection. . 020 0. We have various types and models available. Facebook. 21: Weld line failure caused by hoop stresses. Known also as knit lines and. The edge gate is the most popular and straightforward injection mold gate design. Weld line defects in injection molding is a line or lines on the part surface that caused the part looking ugly or cuased part lifetime, or even broken easily. 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. An evaluation model based on artificial neural network method. For multiple gate and complex part. The formation of weld lines and their location along the flow path is a well-studied phenomenon in conventional injection molding; however, only a few papers are devoted to micro-injection molding [11,13,14,15,16]. Raising the mold temperature will keep the material molten longer, resulting in stronger weld lines and even elimination of weld lines. Fig 13:- Detailed view of weld lines. Clamping unit berfungsi untuk memegang dan mengatur gerakan mold unit, serta gerakan ejector saat melepas benda dari molding unit, pada clamping unit lah kita bisa mengatur berapa panjang gerakan molding saat dibuka dan seberapa panjang ejector harus bergerak. Flow Lines. Injection molding could be applied with many polymer materials, such as. A meld line is defined as the re-merging of two flow fronts. 3 Materials Polypropylene (PP) and. Effects of fillers and/or reinforcements on weld-line strength of nylon 6/6. Weld lines often generate mechanically weak areas, because of the unfavorable perpendicular orientation of the macromolecules, fibers and/or other fillers to the direction of the main flow. To explore the formation of. In recent years, researchers have. of micro injection molding process simulation by technology update and progress. 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. Weld lines can compromise the strength and aesthetics of the part, so it’s important to carefully design the mold and. In injection molding, it is often important to maintain consistent color throughout the part. Meld and knit lines are actually both different types of weld lines. 000 0. Weld-line is a weak area which reduces the strength of the part locally. From Understanding Weld-line Integrity by Sabic Innovative Plastics, p. Redesign the mold to prevent the weld line. Weld line strength is influenced by the temperature at which the weld line is formed and the pressure exerted on the weld until the part freezes, (pressure is 0 at the weld line). 18 ชิ้นงานเกิดเป็นเส้นรอยประสาน Weld line. 1. 020 0. Flow analysis of the weld line formation during injection mold filling of thermoplastics. The weld lines in blow molding occur wherever the pari son knits together in the head, mold tacking areas and mold parting pinch-off region. 1. Munich, Germany: Carl Hanser Verlag, 1994. Weld lines may appear like seams or scratches, but that is not what they are. It is possible to pre. Short Shot Short Shot adalah suatu kondisi dimana, plastik leleh yang akan diinjeksikan kedalam cavity tidak mencapai kapasitas yang ideal atau sesuai settingan mesin. also utilized the co-injection molding technique to study the flow of polypropylene at the weld line behind an obstacle in injection molding; the weld line can be seen clearly from the Fig. The strength of the weld-line area can be increased by optimizing injection molding process parameters like melt temperature, injection speed, packing pressure, changing gate type and location, etc. The second technique, cascade injection moulding, can produce parts free from weld lines. Weld lines are among the most critical structural defects in parts made by the injection molding of fiber-reinforced thermoplastics, explained Sirmax in a press release. Our weld line injection molding is essential for the best result of finished molded products. The thermo. 7 of the reference. Wu CH, Liang WJ (2005) Effects of geometry and injection-molding parameters on weld-line strength. Introduction. This failure causes the product to be damaged during use. Recently hired at plastic injection molding simulation software provider Moldex3D, Nicholson was spurred to undertake the research study following a conversation with a customer experiencing weld-line woes. Maintain a holding pressure that is no more than 1/2 the. Slow down injection speed. The weld line in injection molding is created when two melt streams connect, as shown in Figure 1. Sink Marks Cause 3: Improper Pack or Hold Pressure. 0 mm, is designed to conduct the. 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. This reduced thickness of the frozen skin further enhances the visual appeal of the. Five injection molding process parameters, including mold temperature, melt temperature, packing pressure, injection. <Mold> Increase (or decrease) the size of the runners and gates. 2012. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different directions. A knit line in a plastic injection-molded part is created when two separate plastic flows meet within the mold and "resolidify" along their interface. Injection-molding machine is the Negri Bossi VE210-1700 with screw. In. Weld Lines. Tekanan. The flow of the material in the injection mould takes place through the gate. Weld lines not only affect the appearance and quality of products, but also cause negative influences on the mechanical properties. These are preferred over weld lines as they will normally result in improved cosmetics and structure. Furthermore, injection molding was applied by filling these pellets into a micro-injection molding machine (C. 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. 2. of micro injection molding process simulation by technology update and progress. 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. Figure 1. Materials Science. 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. in the cavity of the injection mold. poor flow fronts that are too cold, this can also lead to a deterioration in the mechanical properties. When this fails to happen correctly, a weld line defect occurs. Participating in DFM and mold flow analysis is a good way to achieve this. Poor weld line quality can lead to short-term or long-term product failures, initiated at the weld line. 18/06/2021. A flow mark is commonly referred to as a flow line occurs during the process of injection molding. Amongst weld line. In this case the two flow fronts will meet and there will be very little molecular orientation across the weld. Slow down injection speed. industry, to deliver intuitive injection mold-ing simulations embedded in NX. Ejector System (Pötsch, 1995) . 22: Weld line formation when melt splits around core pins. , 509 (2) (2011), pp. Weld Lines-3 Ways for Detecting and Correcting. Instead, a line that looks like a seam forms. The utility model relates to a mold structure capable of eliminating the appearance of weld lines of a hole. Miron MC, Major Z, Adachi T. Controlling the mold’s temperature could also minimize the weld line’s effects. Weld lines occur when melt flow fronts meet during the injection molding of plastic 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. Adding vents, using overflows, or using porous metal. warpage, and weld line. Polym Eng Sci 45(7. A weld line is often unavoidable. Weld Line defect analysis, the most common of many defects in injection moulding products. To increase the sustainability of the process, determinative parameters and their effects should be examined. 3. Learn how to avoid them and what injection molding companies do to prevent them. Description Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. 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. The relative weld-line strength is defined as the ratio of the strength of specimens with a weld line and a comparable sample with the same geometry but without the weld line, and this measure mainly depends on the molding conditions, such as melt temperature, mold temperature, and injection pressure [8]. Abstract. Weld-line, a common occurrence in plastic injection moulding, is a representative defect compromising mechanical qualities and product appearance [16]. Boost time too long Shorten boost time, lower boost pressure, or move transfer to an earlier position . In our DFM report, we will analyze the possible weld lines. Miron MC, Major Z, Adachi T. Jiquan Li, Taidong Li, +1 author. Compd. 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. A family of short carbon fiber-reinforced thermoplastic (CFRTP) compounds specifically formulated for injection molding is being used to extend the capabilities of thermoplastic composites in a variety of part sizes and complexities. The impact behavior of weld-lines in injection molding. 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. ” Another. 1. J. If so, look for an alternative resin. The optimum injection molding parameters to manufacture the product was determined by . The strength of the weld-line area can be increased by optimizing injection molding process parameters like melt temperature, injection speed, packing pressure, changing gate type and location, etc. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. Technol. However, research about the computer determination of weld lines in injection molding remains scarce. Venting at Weld Lines. Consequently, weld regions have been observed to have inferior mechanical properties compared to the bulk. The occurrence of a weld line means a significant problem both aesthetically and mechanically in the design of injection moulded parts. Weld-line, a common occurrence in plastic injection moulding, is a representative defect compromising mechanical qualities and product appearance [16]. Xie L. Weld lines in injection molding are frequently unavoidable. In the first, sequential injection moulding, the lines are displaced to noncritical areas of the moulding. Investigate for potential contamination. 10(a) (please see Fig. (1) Increase the injection pressure and prolong the injection time. Machine Shot Capacity – The maximum volume of resin that can be injected in a single stroke of the injection machine. Three terms that often get mixed up in the plastic injection molding industry are weld, meld, and knit lines. As a result this. In this study, we apply the technique of SAW to explore the acoustic properties near injection-weld lines by comparing the velocity of. [1-2] investigated the weld line zone of injection molded glass-fiber-filled polypropylene (PP) composites. These master batches and PP pellets were dry-blended by adjusting the ratio such that the fiber contents were 10, 20, and 30 wt%. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. 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. 943 µm to 0. Gate position in injection mold. The injection molding simulation software used offers a method for the detection of weld lines that has shown to be only reliable for the detection of stagnating weld lines. technical ulletin SPECIALTY POLYME RS Design and Production of Injection Molding Tools. molding Æ Thermoplastics Æ Weld line Æ Simulation Rheol Acta (2004) 43: 240–245 DOI 10. * Corresponding author, e-mail: fengsjpc@ku. Weld lines can be caused by many reasons, which covers the various aspects of mold, process, raw materials and product design, etc. To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. 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. The three parameters affecting operation were called injection pressure, injection time, and packing pressure which influence the quality of weld line. ing weld line properties of injection molded thermo-. Ideally, the resin flow will split into two flow fronts to pass around the obstruction and then recombine into a single flow front. Injection molding of large/complicated products are usually prepared by multiple compounds, which produces weldlines once the melt fronts are joined by impingement flow. Instead of using flow leaders and deflectors to control the locations of the weld lines, this paper presents an approach to specify the locations of the weld. The design of the mold, as well as the part being molded, has a significant impact on the success of the process. If the different flow fronts have cooled. The resulting defects don’t stop at flash only. Investigate for potential contamination. 2. What causes them? The primary cause is weak bondage between two or more flow fronts. G. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. Alloys. Weld lines can be caused by material flowing around holes or inserts in the part, multiple injection gates or variable wall thickness where hesitation or "race tracking" can occur. 4. 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. If it only affects the appearance, it can change the position of the burn four to change the position of the weld line. In the case of PC, the model predicts satisfactorily the weld-line strength as a function of injection temperature. Materials Science. To position weld-line to avoid critical areas for the sake of aesthetics or mechanical strength is the key to the success of bi-injection molding. NX Mold Flow Analysis. Insufficient clamp tonnage Increase clamp pressure or move to machine with more tonnage . Consequently, it causes viscous dissipation which leads to the generation of heat. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection molding processing. In. A meld line occurs when two moving melt fronts converge and flow parallel to each other. ”Weld Lines in a plastic cover. In this paper, a weld line factor (W-L factor) was adopted to describe the. une, 13: 15. Which means engineers need to know how to account for this phenomenon in an efficient way. 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. Ozcelik studied the influence of the injection parameters and weld line on the mechanical properties of polypropylene (PP) during IM process via the design of experiment (DOE). As the weld line can significantly lower the mechanical strength of µIM parts, it is relevant to clarify the position of weld. This paper presents the. As such, optimizing mold designs should always be incorporated in your production model. 1, right). DYNAPLAST Tbk. 5. This may require higher melt temperature or lower injection speed . 2. Silver Streak. A weld line develops when two or more flow fronts come together but do not meld completely because of partial solidification. Weld lines are formed when two melt fronts come in contact with each other. Injection molded plastic parts have comparatively less strength in the weld line section and they also have an impact on product aesthetics. The optimal process condition is very likely to appear in this second part's fine-tune group. Mold. The results showed that the tensile strength of PE remains unchanged in the presence of weld lines. Insufficient plasticizing ability of injection molding machine. In the RHCM, the mold temperature profile plays a crucial. Known methods to reduce weld-line effects are the optimization of injection molding parameters, enhanced tool temperature, and using special molding tool devices. The Factors that Cause Weld Line in Injection molding Pressure. Molding Equipment. Effect of geometry and injection-molding parameters on weld-line strength. 010 0. Here are a few of the most common defects that may occur in plastic injection molding — and how product teams can avoid them. A visible weld line is observed, due to a combina-The Weld line result itself has a scale associated with the placement of the weld line that is directly relative to how severe the weld line will be based on the angle in which the two flow fronts meet. Equipment. The gate is the critical bridge between the runners (the channels through which the molten plastic travels) and the actual mold. In this blog post, we will explore the causes of weld lines in. Flow marks in injection molding can be avoided if adequate measures are taken. This method was adopted. This study examines the impact of injection parameters on the weld line strength of the polyamide 6 and 30% fiberglass (PA6 + 30% FG) composite samples. T he decreased gloss level at the position of. A weld line is a mark left on the surface of a plastic injected molded part. Micro injection molded polymeric parts coated with functional thin films/layers show off the promising applications in microsystems area. Or, the part where the weld line is produced shall. – Use generous and even. Weld lines form where two or more flow fronts come together and can create a cosmetic or structural problem. But the unfavorable and unavoidable defect of weld line in micro injection molding part leads to detrimental mechanical and surface properties. Weld-line strength for plastics can vary from 20% to nearly 100% of the strength of the plastic itself. Gambar 2. 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. 3. Failure may result due to the assembly torque, or end-use application loads (temperature, creep). Known also as knit lines and weld marks, weld lines are difficult to eliminate completely, especially if your injection molded part requires holes. We'll show you how. From: Polylactic Acid (Second Edition), 2019. One of the factors that determines the quality of injection molded parts is the weld line [50,75,76]. Weld line reduction is one of the major concerns in plastic injection molding (PIM) that results in high surface appearance and high strength of a plastic product. An injection molding processor who can analyze the process from the plastics point of view, can quickly solve any molding problem, regardless of the machine or plastic type. During injection moulding, a weld-line occurs when two or more flow fronts collide in the hollow cavity. (2011) and Fig. 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. Bubbles are caused by melting flow fronts colliding in a mold cavity. 1007/s00397-003-0339-2 ORIGINAL CONTRIBUTIONCauses and Remedies of Sink Marks In Injection Molding. <Mold> Increase (or decrease) the size of the runners and gates. Wolfgang Homes, head of the applications department of Eurotool, a manufacturer of hot runner systems, clarified the two methods for IMI, noting that. In this work, the weldline strength of injection molded short-glass-fiber reinforced polycarbonate was derived by an analytical method of modified rule-of-mixtures as a function of the area fraction between skin and core layers. In the injection molding process, weld line regions occur when a molten polymer flow front is first separated and then rejoined. สาเหตุรองของการเกิดปัญหาการเกิดประกายเงิน (silver streak) 1. For those who are new to the injection molding industry, may be confused about this product. 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. If there’s too much mold release, you may require a higher pressure to push it through the machine. Weld Line defect analysis, the most common of many defects in injection moulding products. 7 in Kobayashi et al. DescriptionThis insertion ensures the separation of the melt flow. 2. Injection pressures too high Reduce pressure . A weld line (weld point, flow line or a knit line) forms when separate melt fronts travelling in opposite directions meet. 6. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. How Are They Formed? Molten plastic resin is injected into a mold cavity through an opening known as a gate. Procedia Mater Sci 2014; 3: 2048–2053. 005 0. Article Google Scholar Deng YM, Zheng D, Lu XJ (2008) Injection moulding optimization of multi-class design variables using a PSO algorithm. In this experiment, several ejector. Methodology. Effect of process parameters on the relative weld line strength From injection molding practice and literature, 1, 3,4 it is generally accepted that: if a weld line forms before the filling is. Remember, by avoiding weld lines, you can lessen operations cost. 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. Increase the injection speed to reduce the amount of cooling happening in the mold. Increase the injection speed. Alloys. Injection molding is nothing without molds. Weld lines are the result of fundamental physical effects taking place inside of the mold tool cavity, they are common imperfection to be found in most plastic injection molded parts. Characteristic: Basically, there are PA6 AND PA66(Nylon 6 or Nylon 66), Nylon has tenacious and wearable, self-lubricious and smooth characteristics with non-toxic and antibiosis and high water absorbability. 5 mm, 1. Microsyst Technol, 14 (6) (2008), pp. This article will introduce you the usage, types, and advantages of the Sequence Injection Timer. 2007; Lotti et al. Weld line strength vs. In this paper, a weld line computer determination method based on filling simulation with surface model is proposed, from which the positions and lengths of the weld lines can be predicted. In this paper, a weld line factor (W-L factor) was adopted to. 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. The tensile stresses of the weld lines with ultrasonic functions are 8. In some cases, a weld line can also cause a loss of strength and impact resistance. 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. Sink marks, 2. In this study, the effects of injection temperature, injection pressure, and fiber content on the mechanical properties of weld lines were studied for carbon fiber-reinforced nylon. There are several possible causes that need to be investigated to troubleshoot weld lines in injection molding. The possibility of the functional thin film for. Adjust Injection Molding Parameters: Optimizing injection speed, pressure, and temperature can help ensure better melt flow and reduce the likelihood of weld line formation. Weld Line Factors for Thermoplastics. This principle has been implemented on a complex component in the case of the spring-loaded cogwheel shown in Figure 5, for instance. Depending on the resin, resin temperature, mold temperature, and filling speed, knit lines can vary. injection molding. and Mosle, H. You will have to confirm them before tooling. 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. C. Weld lines can be a weak spot and have therefore to be taken into consideration in part design. Remedies: Raise the temperature of the mold or molten plastic. A weld line occurs when two or more molten plastic flows meet and fuse during the injection molding process, resulting in a visible line on the surface of the molded part. Cracking and/or Crazing can be defined as a fracture or surface breakage in the material of a molded part, usually found in weld line areas, but also on the surface in general. open access Abstract Micro weld lines are the common problem that occurs for plastic molded parts through injection molding process. Plastics manufactured by injection molding are meant to be durable and reliable, able to hold up to heavy use, high temperatures, or adverse conditions. Weld lines, generated during injection molding, can significantly reduce the mechanical performance of structures. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. Wavy lines are another feature of weld lines. Weld lines are a common imperfection to be found in most plastic injected molded parts. Injection pressure or. Miron MC, Major Z, Adachi T. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. Weld lines have been one of the common defects puzzling the injection molding industry. This can allow the. With unchangeable and fixed requirements for the final product, their avoidance often proves difficult. This remains as a challenge for control engineers. According to the weld line distribution map of six gate schemes shown in . Threadline gap in-between part due to improper gate location in complex design parts including excess of holes (multipoint. Edge Gates. The moldability validation and flow analysis tools enable you to iden-tify and correct potential injection molding problems as you design the product. From Understanding Weld-line Integrity by Sabic Innovative Plastics, p. 9. Therefore, the length of flowing weld lines must be additionally defined. 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 of weld-line, etc. Weld lines can. 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. A new kind of weld line was. The impact behavior of weld-lines in injection molding. Microsyst Technol. It is not always easy to completely eliminate weld lines by simply adjusting the relevant injection mold design or the molding conditions. (3-1) Increasing the Resin Temperature at the Weld Line Section. Therefore, the investigation on the developing process of weld line would be a significant issue for improving the quality of micro injection molded parts. At a low volumetric injection flow rate of 33. Mold flow analysis is widely employed in mold making industry, utilizing data simulation software, the injection molding process can be simulated and presented on the computer,. In this study, polypropylene (PP) was compounded respectively with carbon nano fibers (CNFs) and TiO 2 nano particles at various weight fractions (10, 20, 30, 35. 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. 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. Vibration assisted injection molding. A weld line develops when two or more flow fronts come together but do not meld completely because of partial solidification.