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Information about Molding

Published on November 19, 2008

Author: 521420


Molding Definition : Molding Definition Molding is the process of manufacturing by shaping pliable raw material using a rigid frame or model called a pattern. Molding Terminologies : Molding Terminologies Pattern: A sample or prototype to make some design as is made by a dye. Mold: A mold or mould is a hollowed-out block that is filled with a liquid like plastic, glass, metal, or ceramic raw materials. Moldmaker: The manufacturer who makes the molds is called moldmaker . Release Agent:A release agent is typically used to make removal of the hardened/set substance from the mold easier. Types of Molding : Types of Molding Injection molding Compression molding Transfer molding Extrusion molding Blow molding Rotational molding Shell molding Blow Molding : Blow Molding Blow molding a shape is a common industrial process. The example shown below is of the production of a plastic bottle. The plastics normally used in this process are; polythene, PVC and polypropylene. The Process : The Process Process illustration : Process illustration 1. The plastic is fed in granular form into a 'hopper' that stores it. 2. A large thread is turned by a motor which feeds the granules through a heated section. 3. In this heated section the granules melt and become a liquid and the liquid is fed into a mould. 4. Air is forced into the mould which forces the plastic to the sides, giving the shape of the bottle. 5.  The mould is then cooled and is remove AUTOMATIC PET BLOW MOULDING MACHINE : AUTOMATIC PET BLOW MOULDING MACHINE AUTOMATIC PET BLOW MOULDING MACHINE : AUTOMATIC PET BLOW MOULDING MACHINE Automatic PET Blow Moulding Machines for PET bottle production. Our Automatic PET Blow Moulding Machines have wider wide-mouth capability, faster production rates, and shorter changeover times. Also have features such as preferential heating or heat-setting capability. Our Two stage Plastic PET machines can make bottles from round to flat bottle styles. With our two stage Automatic PET Blow Molding Machines you can produce various different shaped PET containers, such as mineral water bottle, beverage bottle, cosmetics bottle, medicine bottle, pesticide bottle, edible oil bottle, milk bottle, Juice bottle and many more types of Plastic PET Bottles. FEATURES OF AUTOMATIC PET BLOW MOULDING MACHINE : FEATURES OF AUTOMATIC PET BLOW MOULDING MACHINE Quick Mold Change-Over using Mold Cage System. Power Equipped Machine using Air Recovery System. Precise Heating System using Heating Power adjustable in decimals. High Output per Cavity compare to the other Machines. Specially designed feeding system carries the preform automatically. Easy installation and starting. Advanced PLC control system with a use-friendly Control Panel. FEATURES OF AUTOMATIC PET BLOW MOULDING MACHINE : FEATURES OF AUTOMATIC PET BLOW MOULDING MACHINE Smooth and steady operation. Long service life and reliable performance. Independent & simple linear running system. Powerful & Efficient Heating Unit with Precision Control and Convenient Adjusting Device. Equipped with Specially Designed Air Storage Unit. Cooling system to get perfect cooling result. 2. Injection Molding : 2. Injection Molding Materials such as polystyrene, nylon, polypropylene and polythene can be used in a process called injection molding. The Process : The Process Injection Molding : Injection Molding Materials such as polystyrene, nylon, polypropylene and polythene can be used in a process called injection molding. These are thermoplastics - this means when they are heated and then pressured in a mould they can be formed into different shapes. A simple diagram of an injection molding machine is shown below. Injection Molding : Injection Molding Injection Molding : Injection Molding Injection Molding Machine : Injection Molding Machine Injection Molding : Injection Molding A similar desk organizer can be manufactured through injection molding. With this process molten plastic is injected into a steel mould. The steel mould made to great accuracy and it can be reused thousands of times. It is made in two halves so that when the molten plastic has cooled, the two parts can be separated and the plastic desk organizer removed. Thermoplastics such as polystyrene, nylon, polypropylene and polythene are ideal plastics for this type of manufacturing process. Injection Molding : Injection Molding A profile cutter is used to trim away any waste or rough material. This is a high speed cutter which is designed to smooth the edges so that sharp edges are removed. Cutter is shown as Injection Molding : Injection Molding Injection Molding : Injection Molding Although the desk organiser is manufactured in one piece, the tubes look as if they are separate. However, if you look closely they are joined by small ‘fillets’ of plastic. These can be cut, if each part of the desk organiser is to be used separately, or the client wants to split the large desk organiser into a number of smaller pieces (by cutting with a scissors or craft knife). Injection Molding : Injection Molding Injection Molding : Injection Molding Stages of Injection moulding : Stages of Injection moulding Stage 1 Granulated or powdered thermoplastic plastic is fed from a hopper into the Injection Moulding machine.Stage 2The Injection Moulding machine consists of a hollow steel barrel, containing a rotating screw (Archemidial Screw). The screw carries the plastic along the barrel to the mould.Heaters surround the barrel melt the plastic as it travels along the barrel.Stage 3The screw is forced back as the melted plastic collects at the end of the barrel.Once enough plastic has collected a hydraulic ram pushes the screw forward injecting the plastic through a sprue into a mould cavity. The mould is warmed before injecting and the plastic is injected quickly to prevent it from hardening before the mould is full Stages of Injection moulding : Stages of Injection moulding .Stage 4Pressure is maintained for a short time (dwell time) to prevent the material creeping back during setting (hardening). This prevents shrinkage and hollows, therefore giving a better quality product.The moulding is left to cool before removing (ejected) from the mould. The moulding takes on the shape of the mould cavity.The image below shows an an Injection Moulding machine. Mounting the mould and setting the clamping unit : Mounting the mould and setting the clamping unit set mould height on the machine with the clamping unit closed check clamping devices fix mould securely to the lifting tackle, ensuring that the two mould halves remain together, if necessary by bolting lock mould and thoroughly tighten up clamping bolts set clamping force at desired level set mould safety device: low pressure and high pressure set mould opening stroke, with damping. set ejectors Mounting the mould and setting the clamping unit : Mounting the mould and setting the clamping unit set speed of the clamping unit set up the mould safety protection heat up mould to the required temperature bring injection unit into rear position check nozzle radius and diameter check penetration depth of nozzle check the centring of the nozzle to the sprue bushing heat up cylinder set cylinder temperatures (not too high) and screw speed Setting the injection unit : Setting the injection unit after having heated up the cylinder, set nozzle contact force make sure the mould is closed initially set material feed somewhat lower than the required shot weight set the position for change-over to hold-on pressure based on safety side plasticize stepwise under manual control, while observing how the material feeds: this should be consistent and not jerky movements after a short pause, purge out manually and check the melt temperature set injection speed and injection pressure to average values Setting the machine controls : Setting the machine controls set the operational selector switch to manual set injection time, after-pressure time and pause time initially somewhat longer than necessary, then optimize them after a few shot Starting the injection process : Starting the injection process When all settings have been checked, switch over from ‘manual’ to ‘semi-automatic’ mode. In general the settings must be optimized after several shots. Take following steps: increase or reduce metering optimize injection speed observe the material cushion in front of the screw check pressure build-up during injection check cooling time and if possible shorten it set screw r.p.m. to a low value: plastification time should be slightly shorter than cooling time Starting the injection process : Starting the injection process check mould locking force harmonize machine movements to obtain a better balance of speeds, sequence and damping if visually acceptable moldings are being produced, check quality where necessary, optimize and store the various functions record machine setting data ensure that moldings are correctly taken out and transported away ensure quality control aim for a ‘fully-automatic’ machine cycle to ensure uniform molding quality The Injection Moulding-Mould : The Injection Moulding-Mould A mould used for Injection Moulding may cost thousands of pounds to produce however it does turn out to be economical as many thousands of mouldings can be produced from a single mould. This results in the low cost of each moulding.It used to be the case that when a new type of casting was needed a brand new die had to be made. Modern dies and moulds are made from a number of interchangeable parts. This allows the shape of the mould to be altered.The dies or moulds used in this process are made from alloy stainless steel. These special alloy steel moulds are made in a number of parts to allow the mouldings to be easily removed.These steel moulds are initially very expensive to make and are suited to production in quantity where accuracy of size, shape and surface finish is essential. Injection Molding Applications : Injection Molding Applications Injection molding is a manufacturing technique for making parts from plastic material. Heated, fluid plastic is injected at high pressure into a mold, which is the inverse of the desired shape. The steel or aluminum mold is machined with the contours of the final product. Injection molding is used for create a variety of parts, like plastic milk cartons, containers, bottle caps, automotive dashboards, pocket combs, and most other plastic products available today. Injection Molding Applications : Injection Molding Applications Injection molding is the most common method of part manufacturing. AC drives will commonly be used to power the hydraulic oil pressure pump for operating the mold works of an injection-molding machine. Servo drives can be used to operate the injection screw, as precision control is often required for the injection step. Significant energy savings are often realized by replacing hydraulics with electric drive systems on injection molding machines. 3. EXTRUSION Molding : 3. EXTRUSION Molding A machine used to extrude materials is very similar to the injection moulding machine above. A motor turns a thread which feeds granules of plastic through a heater. The granules melt into a liquid which is forced through a die, forming a long 'tube like' shape. The extrusion is then cooled and forms a solid shape. The shape of the die determines the shape of the tube. EXTRUSION Molding : EXTRUSION Molding EXTRUSION Molding Products : EXTRUSION Molding Products 4. Shell molding : 4. Shell molding Shell moulding is a process for producing simple or complex near net shape castings, maintaining tight tolerances and a high degree of dimensional stability. Shell moulding is a method for making high quality castings. These qualities of precision can be obtained in a wider range of alloys and with greater flexibility in design than die-casting and at a lower cost than investment casting. The process was developed and patented by Croning in Germany during World War II and is sometimes referred to as the Croning shell process. Shell molding : Shell molding initially preparing a metal-matched plate mixing resin and sand heating pattern, usually to between 505-550 K inverting the pattern (the sand is at one end of a box and the pattern at the other, and the box is inverted for a time determined by the desired thickness of the mill) curing the shell and baking it removing investment Shell molding : Shell molding inserting cores repeating for the other half assembling the mould pouring the mould removing casting cleaning and trimming EXPERIMENTAL DETAILS : EXPERIMENTAL DETAILS Raw Materials, Equipments Resin coated sand. Chromel Alumel Thermocouple, digital panel meter. Muffle Furnace. 2 Kg Aluminium Silicon Alloy (LM6) scrap. Clay Graphite crucible. Fireclay. Asbestos Gloves, Tongs, safety goggles. THE PROCESS DETAILS : THE PROCESS DETAILS THE PROCESS DETAILS The process was optimized to get a better shell by varying the temperature of the metal pattern, holding time of sand – resin mixture and final curing time of shell and pattern. THE PROCESS DETAILS : THE PROCESS DETAILS A metal pattern having the desired shape of the casting is heated to 180 – 250o C. The pattern is sprayed with a solution of a lubricating agent or a release agent containing silicone to prevent the shell from sticking to the pattern. The sand is put in the dumpbox in sufficient quantity. The pattern is then turned down with its heated face inside the dumpbox. The dumpbox is now inverted so that the sand resin mixture falls on the heated metal pattern face. The sand mixture gets heated up and it softens the resin forming a shell on the pattern. THE PROCESS DETAILS : THE PROCESS DETAILS Initially the resin becomes sticky. Further additional heat cures it. The dump box is again turned to its original position. The excess sand falls in the dump box leaving a shell on the pattern. The pattern along with the shell is again kept in the heating oven. This cures the resin in the sand and shell acquires rigidity. On the pattern ejector pins are provided to strip off the shell. After the shells get cooled the two parts are joined properly to form a mould. Fireclay is applied along the edges of the mould to avoid leakage of the molten metal. Shell mould D was used as it had better thickness and had no breakage. THE PROCESS DETAILS : THE PROCESS DETAILS A 2 kg scrap of Aluminium Silicon alloy (LM6) was charged in a muffle furnace in a clay graphite crucible. The dross floating on the molten alloy was removed by a thin graphite plate. The molten aluminium silicon alloy was poured in the cavity of the shell mould. Later on the shell mould was broken to remove the casting. The use of safety goggles, gloves, shoes is a must to avoid any accident. Applications : Applications -Crankshaft fabrication -Steel casting parts, fittings -Molded tubing fabrication -Hydraulic control housing fabrication -Automotive castings (cylinder head and ribbed cylinder fabrication). 5. Plaster Molding : 5. Plaster Molding Design using the plaster of Paris" powder” Form is called plaster molding. Plaster Designs : Plaster Designs Slide 48: Plaster Ceiling Showroom 6. Rotational molding : 6. Rotational molding Rotational molding or moulding is a versatile process for creating many kinds of mostly hollow plastic parts. The phrase is often shortened to rotomolding or rotomoulding. Rotational molding : Rotational molding Process : Process The rotational molding process is a high temperature, low pressure plastic forming process that uses heat and biaxial rotation (i.e. rotation on two axes) to produce hollow, one piece parts. Critics of the process point to its long cycle times- only one or two cycles an hour can typically occur, as opposed to other processes such as injection molding, where parts can be made in a few seconds. The process does have distinct advantages. Manufacturing large, hollow parts such as oil tanks is much easier by rotational molding than any other method. Rotational molds are significantly cheaper than other types of mold. Very little material is wasted using this process, and excess material can often be re-used, making it a very economically and environmentally viable manufacturing process. Process : Process Loading a measured quantity of polymer (usually in powder form) into the mold. Heating the mold in an oven whilst it rotates, until all the polymer has melted and adhered to the mold wall. The hollow part should be rotated through two or more axes, rotating at different speeds, in order to avoid the accumulation of polymer powder. The length of time the mold spends in the oven is critical. Too long and the polymer will degrade, reducing impact strength. If the mold spends too little time in the oven, the polymer melt may be incomplete. The polymer grains will not have time to fully melt and coalesce on the mold wall, resulting in large bubbles in the polymer. This has an adverse effect on the mechanical properties of the finished product. Process : Process Cooling the mold, usually by fan. This stage of the cycle can be quite lengthy. The polymer must be cooled so that it solidifies and can be handled safely by the operator. This typically takes tens of minutes. The part will shrink on cooling, coming away from the mold, and facilitating easy removal of the part. The cooling rate must be kept within a certain range. Very rapid cooling (for example, water spray) would result in cooling and shrinking at an uncontrolled rate, producing a warped part. Removal of the part. Mold Release : Mold Release A good mold release will allow the material to be removed quickly and effectively. Mold releases can reduce cycle times, defects, and browning of finished product. There are many mold releases on the market. Some perform at higher temperatures, some are biodegradable. Others can be hazardous to the environment and the worker. Fortunately, more and more companies are developing user and environmentally safe alternatives. Materials : Materials More than 80% of all the material used is from the polyethylene family. Cross-linked polyethylene (PE); linear low density polyethylene (LLDPE); high density polyethylene (HDPE). Other compounds are PVC plastisols, Nylons, and polypropylene. Natural Materials: It's only been possible relatively recently, but natural materials can also be used. Through the use of real sands and stone chip, sandstone composite can be created which is 80% natural non-processed material. 7. Transfer molding : 7. Transfer molding Transfer molding, like compression molding, is a process where the amount of molding material (usually a thermoset plastic) is measured and inserted before the molding takes place. Transfer molding : Transfer molding This is an automated operation that combines compression-, molding, and transfer-molding processes. This combination has the good surface finish, dimensional stability, and mechanical properties obtained in compression molding and the high-automation capability and low cost of injection molding and transfer molding. Transfer Molding is having a "piston and cylinder"-like device built into the mold so that the rubber is squirted into the cavity through small holes. Transfer molding : Transfer molding A piece of uncured rubber is placed into a portion of the transfer mold called the "pot." The mold is closed and under hydraulic pressure the rubber or plastic is forced through a small hole (the "gate") into the cavity. The mold is held closed while the plastic or rubber cures. The plunger is raised up and the "transfer pad" material may be removed and thrown away. The transfer mold is opened and the part can be removed. The flash and the gate may need to be trimmed. Transfer molding : Transfer molding Transfer molding provides product consistency. Transfer molding has short cycle times. Transfer molding is suited for rubber to metal bonding. Moldings and Applications : Moldings and Applications Casing Casing is the wood trim or moulding applied to openings such as doors, windows and archways. Casings are used to cover the gap between the wall and the frame. Casings are the most visible trim or moulding and as such help define the character of a room. Moldings and Applications : Moldings and Applications Hand Rails Hand Rails are attached along a wall to be used as hand support along a stairwell or hallway. Hand Rails also provide protection for walls in high traffic areas. Moldings and Applications : Moldings and Applications Nosing Nosing is the trim that creates the rounded edge of a stair tread. The finished moulding covers the edge of risers. Moldings and Applications : Moldings and Applications Picture Frame Moulding Picture Frame Moulding is a trim applied to a wall near the top of a ceiling. The top lip supports hooks to hang framed pictures or decorative plates. Picture Frame Molding adds a colonial or warm traditional feel to a room. Moldings and Applications : Moldings and Applications Window Sills Window Sill Moulding is installed below the window sash. Window Sills are sometimes called "window stools." Trim is often added under the Window Sill for a more decorative and finished look. Moldings and Applications : Moldings and Applications Rope Moulding Rope Moulding is a finishing trim with a decorative twisted pattern. Rope molding is often used in compound Crown Mouldings, on mitered cabinet doors and in amny creative, custom designs. Moldings and Applications : Moldings and Applications Door Stop Molding A Door Stop is the trim that prevents the door from closing past the door jamb. The Door Stop molding is applied to one side of an interior door frame or the interior side of a transom or sidelite jamb. Moldings and Applications : Moldings and Applications Dentil Molding Dentil Molding or Strips have a pattern of closely spaced blocks and spaces and are used as a decorative molding, especially in classic architecture. Dentil Moulding is often found around the base of Crown Moulds. Moldings and Applications : Moldings and Applications Crown Moulding Crown Moulding is ususally installed in the corner where the ceiling and wall meet. It is a transitional moulding used to fill gaps and uneven edges or just to add distinction to the room. The moulding can be as large as 15" depending on the style of the room. Mouldings can be combined to make a compound Crown Mold. Moldings and Applications : Moldings and Applications Cove Molding Cove Molding is a smaller, concave molding used where walls and ceilings meet. They are often used as an inside corner guard or to hide joints. sometimes Cove Molding is used as a transitional molding to a mantle or shelf and often in combination with other trim to create beautiful compound moldings. Moldings and Applications : Moldings and Applications Chair Rail Molding Chair Rail molding is attached to a wall about three feet from the floor. Chair rails are intended to protect walls from scuffs and dents from chair backs. Chair Rail molding creates a visual break between the top and bottom of a wall and is used as a beautiful, decorative accent. Moldings and Applications : Moldings and Applications Baseboard Molding Baseboard molding is installed around the perimeter of a room where the walls meet the floor. Base boards fill in the gaps and uneven edges and help protect the walls from kicks and bumps. Visually, baseboards form a foundation for the room. Often many layers of molding are used to create a decorative baseboard design. Moldings and Applications : Moldings and Applications Base Cap Molding Base Caps are used as an addition to regular baseboard molding to create a finished and more complex architectural molding. Moldings and Applications : Moldings and Applications Astragal Molding Astragal molding can be used as a decorative element at the top or base of an architectural column or as framing molding on furniture or woodwork. It is often used as a component of more complex molding and is sometimes attached to one or both doors to close a gap. Moldings and Applications : Moldings and Applications Scribe Moulding Scribe Moulding is a lightweight trim used to cover the seam where two surfaces meet on the same plane.

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