LABORATORY REPORTCourse Name Engineering Workshop Course Code EPT183 / 2 Semester 2 SA Instructor’s Name Mohamad Hatta Musa Title of Workshop Injection Moulding Ernie Suzlyana Binti Mohamed Tasuni 151050827 Nor Nafsiah Binti Annuar 151050868 Mark Abstract 10 Introduction 25 Methodology 10 Results & Discussions 35 Conclusions 15 Others (Format, References, Appendix) 5 TOTAL ABSTRACT 100 2015/16 Injection Moulding (IM) is considered to be one of the most prominent processes for mass production of plastic products. One of the biggest challenges facing injection molders today, is to determine the proper settings for the IM process variables. Selecting the proper settings for an IM process is crucial because the behaviour of the polymeric material during shaping is highly influenced by the process variables. Consequently, the process variables govern the quality of the parts produced. The difficulty of optimizing an IM process is that the performance measures usually show conflicting behaviour. Therefore, a compromise must be found between all of the performance measures of interest. This thesis demonstrates a method of achieving six sigma standards in small and medium plastic injection moulding enterprises. A modified six sigma cycle called DAURR (Diagnose, Analyse, Upgrade, Regulate and Review) based on Taguchi method, Regression analysis and Artificial Neural Network has been proposed in this work that can be used to find the best compromises between performance measures in IM, and potentially other polymer processes. Its feasibility was studied with the help of a case study. The method has been employed for the improvement in two quality characteristics (hardness and over shrinkage) of injection-molded nylon-6 kamani bush produced in a small enterprise. After the implementation of the proposed method, targets for improvement are clearly defined with the problems and causes being identified. The process parameters are then optimized for quality characteristics improvements so that the Six Sigma standard is reached. This research work provides methodology so that six sigma approaches can be applied and adjusted according to the requirements of small and medium enterprises (SMEs). This work also presents a novel, general and intelligent approach to multi response process optimization, with a purpose to obtain a single optimum setting of process parameters that meets specifications of all considered, possibly correlated, responses. INTRODUCTION Geometries only limited by mold manufacturability. thanks to its low operational cost. Cons . injection molding remains the most popular manufacturing process for plastic materials in mass production. The mold is then opened and the part is ejected. Pros and Cons of Injection Molding Pros Low costs in mass production High precision Complex parts. It can be used for producing parts from both thermoplastic and thermoset polymers. and the flexibility to make parts with complex shapes. A Typical Injection Molding Process In spite of the relatively expensive tooling cost. The melt is then injected/forced into a chamber formed by a split-die mold.Injection molding is considered one of the most common plastic part manufacturing processes. The melt remains in the mold and is either chilled down to solidify (thermoplastics) or heated up to cure (thermosets). The process usually begins with taking the polymers in the form of pellets or granules and heating them to the molten state. high throughput. The hydraulically powered clamping unit pushes the mold halves together and exerts sufficient force to keep the mold securely closed while the material is injected. Each half of the mold is attached to the injection molding machine and one half is allowed to slide. . High initial setup costs METHODOLOGY Raw material Recycle material Material preparation Drying Pigment colour Injection moulding Mold temperature controller Product The process cycle for injection molding is very short. The time required to close and clamp the mold is dependent upon the machine . It consists of the following four stages: 1. the two halves of the mold must first be securely closed by the clamping unit. This time can be estimated from the dry cycle time of the machine.larger machines (those with greater clamping forces) will require more time. Clamping Prior to the injection of the material into the mold. injection pressure. Injection The raw plastic material. 4. The molten plastic is then injected into the mold very quickly and the buildup of pressure packs and holds the material. Cooling The molten plastic that is inside the mold begins to cool as soon as it makes contact with the interior mold surfaces. However. it will solidify into the shape of the desired part. and injection power. However. The packing of material in the injection stage allows additional material to flow into the mold and reduce the amount of visible shrinkage.2. During this process. Ejection . The cooling time can be estimated from several thermodynamic properties of the plastic and the maximum wall thickness of the part. As the plastic cools. the material is melted by heat and pressure. The amount of material that is injected is referred to as the shot. usually in the form of pellets. is fed into the injection molding machine. The injection time is difficult to calculate accurately due to the complex and changing flow of the molten plastic into the mold. The mold cannot be opened until the required cooling time has elapsed. the injection time can be estimated by the shot volume. during cooling some shrinkage of the part may occur. and advanced towards the mold by the injection unit. 3. Force must be applied to eject the part because during cooling the part shrinks and adheres to the mold. a mold release agent can be sprayed onto the surfaces of the mold cavity prior to injection of the material. EQUIPMENTS OR APPARATUS Injection molding machines have many components and are available in different configurations. and clamping unit to perform the four stages of the process cycle. the mold can be clamped shut for the next shot to be injected. all injection molding machines utilize a power source. TYPE OF MOLD AND CONSTRUCTION . Once the part is ejected. When the mold is opened. which is attached to the rear half of the mold. a mechanism is used to push the part out of the mold. including a horizontal configuration and a vertical configuration.After sufficient time has passed. RESULT AND DISCUSSION 1. In order to facilitate the ejection of the part. the cooled part may be ejected from the mold by the ejection system. injection unit. a set of 2-plate mold. The time that is required to open the mold and eject the part can be estimated from the dry cycle time of the machine and should include time for the part to fall free of the mold. regardless of their design. However. mold assembly. MACHINE MOULD SPECIFICATION Injection system The injection system consists of a hopper. compressing. and an injection nozzle. melting.Injection mold construction is the process of creating molds that are used to perform injection molding operations using an injection molding machine. runner and gate selection and component ejection system selection. while the three plate mold requires two days. The two plate mold requires a single day in light. 2. These are generally used to produce plastic parts using a core and a cavity. which determines the parting line selection. and packing stages. degassing. Molds are designed as two-plate or three-plate molds. This system confines and transports the plastic as it progresses through the feeding. The mold base size depends on component size and number of cavities to be planned per mold. Mold construction depends on the shape of the component. . depending on the type of component to be manufactured. a reciprocating screw and barrel assembly. injection. Machine mould maximum minimum specification Thickness Mould size 385mm 200mm 270mm x 270mm 76mm Ejector pin stroke 3. Complete filling of the casting cavity. are: Clean molten metal.g. Edge gate: Most suitable for square. . the gate mark is visible in component and no runner is required. rectangular components Ring gate: Most suitable for cylindrical components to eliminate weld line defect Diaphragm gate: Most suitable for hollow. GATE TYPES The two main gate systems are manually trimmed gates and automatically trimmed gates. Smooth filling of the casting cavity. e. Objective of the Gating System : The four main points. The following examples show where they are used: Sprue gate: Used for large components. cylindrical components Tab gate: Most suitable for solid. thick components Submarine gate: Used when auto de-gating is required to reduce cycle time Reverse taper sprue gate (Pin gate): Generally used in three plate molds.: bucket molding (backside cylindrical gate mark visible and can be felt). which enables a proper gating system. Uniform filling of the casting cavity. . 4. Sprue : It is circular in cross section. Complete filling of the cavity makes the metal thin with minimum resistance at the end sections. closed loop. microprocessor controlled machines are the 'norm'. the thermoplastic is melted and then injected into a mould with some form of plunger arrangement. which in turn minimizes the surface instability. Thermoplastic injection moulding requires the transfer of the polymeric material in powder or granule form from a feed hopper to a heated barrel. THE INJECTION MOLDING CYCLE The modern day process has developed and matured significantly to the level where fully automated. It is circular or rectangular in shape. Runner : The runner takes the molten metal from sprue to the casting. In the barrel. It collects the molten metal. Sprue Well : It changes the direction of flow of the molten metal to right angle and passes it to the runner. which is poured. If it has a uniform filling it means that the casting fill is in a controlled manner.The mold cavity must be filled with a clean metal so that it prevents the entry of slag and inclusions into the mold cavity. Ingate: This is the final stage where the molten metal moves from the runner to the mold cavity. The main elements needed for the gating system are as follows: Pouring basin : This is otherwise called as bush or cup. Slag trap : It filters the slag when the molten metal moves from the runner and ingate. The basic injection moulding process steps with a reciprocating screw machine are as follows. although in principle injection moulding is still a relatively simple process. It is also placed in the runner. The molten thermoplastic solidifies quickly within the mould. If the mold has smooth filling then it helps to reduce the bulk turbulence. It leads the molten metal from the pouring basin to the sprue well. from the ladle. allowing ejection of the component after a pre determined period of cooling time. The mould is clamped shut under pressure within a platen arrangement and is held at a temperature well below the thermoplastic melt point. ii. this provides platen movement and also clamping force when the toggle joint is finally locked over rather like a knuckle arrangement. A check valve is fitted to the front of the screw such as to let material pass through in front of the screw tip on metering (material dosing). The screw is contained within a barrel which has a hardened abrasion resistant inner surface. which moves only by a few millimetres. Present day moulding machines range from around 15 to 4. Mould Close and Clamping The mould is closed within the platen arrangement and clamped using necessary force to hold the mould shut during the plastic injection cycle. In this case a mechanical toggle device. is actuated by a relatively small hydraulic cylinder. and compression ratios from rear to front of around 2 : 1 to 4 : 1 in order to allow for the gradual densification of the thermoplastic material as it melts. Injection At this stage in the machine cycle the helical form injection screw (Figure 1) is in a 'screwed back' position with a charge of molten thermoplastic material in front of the screw tip roughly equivalent to or slightly larger than that amount of molten material required to fill the mould cavity. The second type of general clamping arrangement is referred to as the Toggle Lock. Injection moulding screws are generally designed with length to diameter ratios in the region of 15:1 to 20:1. through to the platen and tool. Alternatively.i. smaller auxiliary pistons may be used to carry out the main movement of the platen and a mechanical blocking arrangement is used to transfer locking pressure from a pressure intensifier at the rear of the machine. but not allow material to flow back over the screw flights on injection. although usually they are of two general types. thus preventing plastic leakage over the face of the mould. Many systems are available for opening/closing and clamping of mould tools.000 metric tonnes available clamping force (150 to 4000 kN). Direct Hydraulic Lock is a system where the moving machine platen is driven by a hydraulic piston arrangement which also generates the required force to keep the mould shut during the injection operation. . which is connected to the rear of the moving platen. and into the moulding tool itself. This time allows the heat in the moulding to dissipate into the mould tool such that the moulding temperature falls to a level where the moulding can be ejected from the mould without excessive . Heat input can therefore be closed loop controlled with a Proportional Integral and Derivative (PID) system. this will help minimise residual stresses in the resultant moulding. Holding pressure may be initiated by one of three methods: by a set time in seconds from the start of the injection fill phase. The screw (non-rotating) is driven forward under hydraulic pressure to discharge the thermoplastic material out of the injection barrel through the injection nozzle. usually with a molten 'cushion' of thermoplastic material in front of the screw tip such that a 'holding' pressure may be maintained on the solidifying material within the mould. thus allowing compensating material to enter the mould as the moulded part solidifies and shrinks. or by the rise in hydraulic pressure as measured by a pressure transducer in the mould itself or in the injection hydraulic system. Holding Pressure and Cooling The screw is held in the forward position for a set period of time. the hold pressure may be decayed to zero. Thermocouple pockets are machined deep into the barrel wall so as to provide a reasonable indication of melt temperature. Once the hold pressure phase has been terminated the mould must be held shut for a set period of cooling time. these are used to primarily heat the thermoplastic material in the barrel to the required processing temperature and make up for heat loss through the barrel wall. iii.Figure 1. As the material solidifies to a point where hold pressure no longer has an effect on the mould packing. by the position of the screw in millimetres from the end of injection stroke. which forms an interface between barrel and mould. due to the fact that. Reciprocating screw injection moulding unit Normally. ceramic resistance heaters are fitted around the barrel wall. during processing most of the heat required for processing is generated through shear imparted by the screw. due to its helical nature. type of component and production rate required. This is referred to as `back pressure' and it helps to homogenise the material and reduce the possibility of unmelted material transferring to the front of the screw. the barrel is recharged with material for the next moulding cycle. iv. The material is gradually transferred forward over the screw flights and progressively melted such that when it arrives in front of the screw tip it should be fully molten and homogenised.distortion or shrinkage. 5. v. Depending on the type of plastic this can be within a few degrees or over a temperature range. and distance. time. The moulding may free fall into a collection box or onto a transfer conveyer. or by an air operated ejector valve on the face of the mould tool. Screw rotation may be set as one constant speed throughout metering or as several speed stages. Once the moulding is clear from the mould tool. as shown in . or may be removed by an automatic robot. The mould may be connected to a cooling unit or water heater depending on the material being processed. The injection screw rotates and. temperature. Increased shear is imparted to the material by restricting the backward movement of the screw. material in granule or powder form is drawn into the rear end of the barrel from a hopper feed. the complete moulding cycle can be repeated. In this latter case the moulding cycle is fully automatic. The throat connecting the hopper to the injection barrel is usually water cooled to prevent early melting and subsequent material bridging giving a disruption of feed. this is done by restricting the flow of hydraulic fluid leaving the injection cylinder. the operator may intervene at this point in the cycle to remove the moulding manually. Material Dosing or Metering During the cooling phase. Mould temperature control is incorporated into the tool usually via channels for pressurised water flow. The screw rotation speed is usually set in rpm which is measured using a proximity switch at the rear of the screw. In semi-automatic mode. This usually requires the moulding to fall to a temperature below the rubbery transition temperature of the thermoplastic or Tg (glass transition temperature). This is usually carried out with ejector pins in the tool which are coupled via an ejector plate to a hydraulic actuator. Mould Open and Part Ejection When the cooling phase is complete the mould is opened and the moulding is ejected. The molten material transferred in front of the tip progressively pushes the screw back until the required shot size is reached. INJECTION MOLDING CONTROL PARAMETER These parameters fall within four major areas: pressure. This is pressure that is created during the return action of the screw after injecting material. To the troubleshooter. the pressure must be sufficient to inject the plastic material and to hold the mold closed. but there is also pressure found in the clamp unit of the molding machine. Figure 2 Four parameter areas. But. and controlling the weight of the shot by maintaining an accurate density of a given volume of melt. all four areas are important. The maximum setting is needed because anything over that will cause too much shearing of the plastic and result in thermally degraded plastic. removing small amounts of trapped air. In addition. Distance and time will not be discussed here as they are beyond the intended scope of this chapter. In the following section. Based on the requirements of any particular plastic material. with a maximum setting of 300 psi. The screw turns (augers) to bring fresh material into the heating cylinder. PRESSURE Pressure is found primarily in the injection area. This material is placed in front of the screw and nudges the screw backwards. This pressure is used for better mixing of the plastic (especially if colors are added at the press). . A buildup of pressure is created at the front end of the screw. The back pressure setting should start at 50 psi and be increased in 10 psi increments as needed. We will address all of these pressure requirements here.Figure 2. the pressure and temperature areas are the ones most commonly considered during the troubleshooting process. the temperature of the injected plastic and mold must be correctly maintained. BACKPRESSURE The first pressure to consider is backpressure. we will discuss the importance of various facets of the pressure and heat parameter areas. INJECTION PRESSURE The next type of pressure to consider is injection pressure. the amount of clamp pressure required is based on the material being molded. And. And. So. This is the primary pressure for injecting 95% of the molten plastic into the closed mold. the machine should drop into hold pressure. Therefore. only as to when it will be released. and then use all of it. The easier flow materials require less injection pressure. thus they require less clamp pressure. There is no question as to its being released. However. the more fluid it becomes and the lower the pressure can be to fill the mold. we have clamp pressure. Conversely. CLAMP PRESSURE At the other end of the machine. the hotter the plastic. and the greater the reaction when it is released. This pressure is about half of the injection pressure and is used to finish filling the mold by packing the molecules together in an orderly fashion. If valve gating of a hot runner system is used. hold pressure has no more effect on the molecules on the other side of the gate. that stress will be released at some time. the stiffer flow materials will require more injection pressure. Normally. the highest pressure and fastest fill rate are the best condition. the material in the cavity is still molten and will be sucked back out of the cavity. Once that happens. normally in 3 to 4 seconds. The only reason to have clamp pressure is to keep the mold closed against injection pressure. If hold pressure is released before the gate freezes. The greater the pressure. thus more clamp pressure. the greater the stress. there will be insufficient pressure to pack the molecules together and uneven shrinkage and cooling will take place. . high pressure will increase molded-in stress. Hold pressure is required until the gate freezes off. remember. HOLDING PRESSURE Once the majority of the plastic (95%) has been injected using standard injection pressure. To determine how much clamp force is needed for a specific product. you should determine the minimum amount of pressure necessary to fill the mold. find the projected area of the part being molded and multiply it by two to six tons for each square inch of projected area. At the very least. holding pressure can be released earlier than with standard surface gating. This shutoff land is simply a wall of steel surrounding the part and is approximately 0. x 5 tons). (as published by the material supplier) so the total force would be only 72 tons (36 sq.003 inches in height and at least 1/4" wide. the total force required would be 180 tons (36 sq. we would only need two tons per sq. the supplier assumes there is a proper shutoff land surrounding the cavity image. or use only a portion of the tonnage available in the press the mold is in. . in. that must be discussed regarding clamp tonnage calculations. x 2 tons). we would need five tons per square inch of area (as published by the polycarbonate supplier). in. But. There is one factor. however. if we were molding polycarbonate for the part shown in Figure 3. Therefore. Reducing the tonnage requirement also reduces the cost to mold the part because we use fewer resources. if we were molding nylon 6/6. A typical shutoff land is shown in Figure 4. So.002/0. we could run the mold in a smaller press.Figure 3 Determining Clamp Force Requirement For example. When the material suppliers state a specific clamp tonnage value (such as five tons per square inch for polycarbonate). in. chances are there is no shutoff land being utilized. We will investigatecontrolling all of these areas. The calculations shown earlier assume there is a shutoff land. and nozzle zones. center. Each is controlled independently of the others. They are the rear. . That allows us to use less total force than if the clamp force is dispersed over the entire face of the mold base. front. the amount of clamp force will be 3 to 4 times as much as with the shutoff land. but heat is also found in the mold and in the heat exchanger of the machine. See Figure 5 for reference.Figure 4 Shutoff Land The purpose of this shutoff land is to concentrate all the clamp force to the area surrounding the cavity. If you use these calculations and the mold flashes easily around the part. Heat is used to soften the plastic to the point of being able to inject it. INJECTION UNIT There are four zones of heat that must be controlled in the injection unit. HEAT The next parameter area we will look at is heat. Without the shutoff land. In most cases. We can determine that temperature by sliding the injection unit back from the mold and injecting material into the air.Figure 5 Injection Unit Heat Zones The injection unit is designed to drag material through the four zones and to heat it gradually as it travels through the heating cylinder. Figure 6 depicts this action. This is called an air shot. or 10 degrees (F) hotter than. the front zone. and the nozzle should be the same as. These lines are connected to a source of temperature-controlled water that circulates through the . The heat should be lower in the rear than in the front. You can find this value for some common materials in the area of our site that discusses Melt Temperatures. The heat is provided at a rate of approximately 50% for each of these devices. It is important to understand. however. that the heat is created by heater bands strapped around the outside of the injection cylinder as well as by the turning action of the screw inside the heating cylinder. but rather the temperature of the steel of the injection unit's heating cylinder. The temperature control units do not measure the actual temperature of the plastic being heated. MOLD TEMPERATURE The most common method used for cooling the plastic once it is injected into the mold is a set of water lines. the heating cylinder will be set at 50 to 100 degrees (F) higher than the melt temperature of the plastic. The plastic must be at the right molding temperature as it leaves the nozzle of the molding machine. This is because the plastic is moving through the heating cylinder at a fairly rapid pace and must absorb enough heat during its travel to get to the desired temperature. Figure 6 Measuring Melt Temperature The temperature at this point should be the temperature requirement published by the material supplier. This is important because the settings for the heating cylinder temperatures must be made higher than the actual melting temperature of the plastic. Modern temperature controls are able to hold a temperature setting to within 1 degree (F). When it falls upon a special plate of the machine that is designed to accept this material (called a purge plate) we can use a pyrometer to measure the molten plastic temperature. That is true maintenance of temperature. As with the mold. The heat exchanger must then be removed and the copper tubing must be flushed with acid or drilled out with special cleaning equipment. and if it is too hot. but warm enough to keep it from becoming solid too fast. The waterlines are sized and located such that the water pulls heat out of the mold as fast as it is being generated. CONTROL AND CONSISTENCY The two most important things necessary for the molding of the highest quality products at the lowest . the additives in the oil will fall out of solution and clog hydraulic mechanisms causing them to be inoperative or slow to respond. The material supplier is the source that defines the proper mold temperature and this is published information for mold temperature requirements for some common materials). the water is being used to maintain the temperature of the mold and should be the same temperature leaving as entering (within 10 degrees F).mold and pulls out heat that is building up in the mold over time. This is especially true of crystalline (or semi-crystalline) materials. This oil usually must be maintained at a temperature between 100 and 125 degrees (F) for proper use. The belief is that the water is used to pull heat from the plastic and therefore must be hotter when the job is complete. this circulating water pattern is designed to pull heat from the oil as fast as it is being generated. HEAT EXCHANGER The heat exchanger is a sophisticated radiator device that controls the temperature of the hydraulic oil used in the molding machine. That is the definition of maintaining the temperature. One common mistake of most troubleshooters is believing that the water leaving a mold should be hotter than the water entering the mold. Actually. If it is too cool. the molecules do not have a chance to ``bond'' properly and the part will be weak or brittle. this indicates a blockage (such as calcium deposits) in the heat exchanger that is interfering with proper heat transfer. Each plastic family has a specific mold temperature range within which it should be processed for highest quality parts at lowest possible cost. If the plastic solidifies too fast. It must be cool enough to solidify the plastic quickly. the machine actions are sluggish and inconsistent. If the water leaving the heat exchanger is hotter than the water entering it. The oil is passed over a series of copper tubes that have water running through them. If the water leaving the mold is hotter than that entering the mold it means there is still a lot of heat left in the mold and the waterline design is not adequate to pull heat out as fast as it is being generated. the placement and operation of portable cooling fans. ranging from quick and short at the start of a shift and after each break or rest period. The human being works at varying speeds and distances throughout the day. The inconsistent action causes inconsistent cycles and molded parts that vary in quality. singing songs. but primarily in machine actions. Human consistency can be achieved. standardization of mold components. but also such items as the environment in which the parts are molded. One area of major importance is that of any operator-controlled activity such as the opening and closing of a safety gate (often called the operator's gate). Control should be applied to every possible parameter that can be determined. The operators can be instructed in the value of consistent operation and strive for consistency in their personal actions. These include those of the four areas mentioned earlier. not to mention cost. Consistency should be applied wherever possible.possible cost are control and consistency. This is the major reason many molders are utilizing robots or other automated methods of molding. All of this reduces the necessity of troubleshooting activities as fewer defects are being produced. defective parts will be minimized and production costs will be reduced as the quality of the molded parts increases. through proper training and knowledge transfer. tapping feet. however. but slower and longer in between those times. Once control of as many parameters as possible is established and maximum consistency is achieved. . They wish to remove the human tendency towards inconsistency thus improving quality and reducing cost of the molded parts. and any other action that is adjustable or variable. Most machine actions are controlled through electronic devices or computer controls and are extremely consistent. There should be no random or wandering motions or actions. reciting poetry. operation of secondary equipment. When they find a method that works they can be as consistent as the automated molding machine for an entire shift. A conscientious operator (and most are) will find ways of achieving the required consistency by humming tunes. or simply listening for a specific sound produced by the molding machine or mold. But any operator-controlled action tends to be inconsistent due to the nature of human endeavor. 6. INJECTION MOLDING PRODUCT DEFECTS Incomplete Fillings: not enough resin to fill the mold completely inadequate injection stroke low injection rate low injection pressure resin viscosity too high exotic geometry Surface Imperfections: moisture or air bubbles in the resin temperature too high causing resin decomposition not enough pressure to fill the mold completely dirty mold Burned Parts: temperature too high polymer trapped and degraded in the nozzle slow chilling cycle Warped Parts uneven mold surface temperature . warping. Using the least wall thickness for the process ensures rapid cooling. 4. and minimum shot weight. Use ribs or gussets to improve part stiffness in bending. 5. 3. or product design requirements. residual stresses. and cycle time costs. The inside corner radius should be a minimum of one material thickness. material costs. thereby saving on part weight. 2. INJECTION MOULDING PRODUCT DESIGN EVALUATION 1. This avoids the use of thick section to achieve the same. Use generous radius at all corners. This will minimize sinking. Use uniform wall thicknesses throughout the part. short cycle times. Use the least thickness compliant with the process. All these result in the least possible part cost. and improve mold fill and cycle times. design flaws parts removed from the mold too early 7. material. The following are some commonly used design elements: . Design parts to facilitate easy withdrawal from the mold by providing draft (taper) in the direction of mold opening or closing. it is useful to understand basic design features and construction of simple injection mould tools (figure 2). However. . Ribs Boss Counter bore/sink Inserts Self-Tapping Screws Snap Latches Living Hinge Mould Design Mould design is in itself an extremely diverse and complicated subject. Cooling channels are machined into the core and cavity plates in order to remove the . Typical mould tool arrangement.Figure 2. these are fixed into a rear ejector plate which is connected to a hydraulic actuator behind the moving platen. In the case of a single impression (cavity) mould. Starting from the injection side. the sprue feeds onto a runner system machined into the tool face that acts as a transfer system to the cavity for the molten material. a location ring is fitted to the back of the rear backing plate. Gates are preferably as small as possible in order to minimise the potential ‘witness’ mark on the component. in the case of a multi impression mould. hardened pins are used to eject the components from the mould. these may be machined directly into solid steel or aluminium plates. In this particular example. In this case the mould simply consists of two halves commonly referred to as the moving (core) half and fixed (cavity) half. Instead the molten material remaining in the hot runner system after injection of a component forms part of the next shot. Many different types of gating may be used to connect the runner system to the mould cavities. It can be seen that a sprue and a cavity form in the mould creates the component shape. this locates and centralises the mould into the fixed platen. or made separately as inserts which may be subsequently fitted to the core and cavity supporting plates. Through the locating ring a sprue bush can be seen. The sprue bush is profiled with a radius to match up with the injection unit nozzle so that material can be directly transferred from the injection unit through to the mould cavity. A profiled ejector pin behind the sprue bush ensures separation of sprue from sprue bush when the mould opens and aids ejection of the runner system. the sprue may feed directly onto the component. Heated or hot runner systems may be incorporated in the fixed half of the mould such that the sprue and runner feed system is constantly molten and therefore not ejected at the end of the cycle. CONCLUSION In conclusion. Through the use of design expert it was shown how some control variables have a strong effect on a specified characteristic. Even though this experiment was a half factorial. were pressure and flow weight. Through design expert it was found that the variables affecting the final weight of the plastic mold injected part the most. This lab was useful in exploring and understanding how different effects on a desired characteristics for a part. a lot of useful data was collected about the different factors and how they interact with each other. we conclude that plastic injection molding is very helpful in making all necessary basic goods like tumblers. while others have little t n effect. Finally. injection molding is an extremely useful tool for mass-producing polymer parts once the parameters for its ideal operation have been ascertained. The complete tool is held together with a system of spacer blocks.process heat from the tool. Each of these factors had a larger impact than the nozzle temperature and dwell time combined. body of the brush etc which attract people with snazzy colours as well as shining and their smoothness. APPENDIX . bolster and backing plates such that it may be bolted directly to the machine platens and is completely rigid and able to resist injection forces. Mould with ejector pin Hopper . Products . org/wiki/Injection_mold_construction#Gate_types .G.Wikipedia.wikipedia. 3rd Revised edition (1 February 1983) Manufacturing Engineering and Technology Serope Kalpakjian. Pye Godwin Books.REFERENCE Injection Mould Design R. the free encyclopedia https://en. 6th Edition Injection mold construction .W.