各种常用成形工艺英汉对照塑料成型injection molding 射出成形 （注塑成型）extrusion molding 挤出成形 （挤出成型） calendaring molding 压延成形 （压延成型） hollow(blow) molding 中空(吹出)成形matched mould thermal forming 对模热成形 compression molding 压缩成形 （压制成型） transfer molding 转送成形 （传递模塑成型）slush molding 凝塑成形 （搪塑）rotational molding 离心成形 （滚塑）foam forming 发泡成形 （发泡成型）dip mold 浸渍成形encapsulation molding 注入成形 （封装成型）matched die method 对模成形法compound molding 复合成形laminating method 被覆淋膜成形rubber molding 橡胶成形/tips/tips_process_methods.htm Plastic Processing MethodsPROCESS DESCRIPTIONBlow吹塑 An extruded parison tube of heated thermoplastic is positioned between two halves of an open split mold and expanded against the sides of the closed mold via air pressure. The mold is opened and the part ejected. Low tool and die costs, rapid production rates, and ability to mold fairly complex hollow shapes in one piece.Calendering压延 Dough-consistent thermoplastic mass is formed into a sheet of uniform thickness by passing it through and over a series of heated or cooled rolls. Calenders are also utilized to apply plastic covering to the backs of other materials. Low cost, and sheet materials are virtually free of molded-in stresses.Casting Liquid plastic, which is generally thermoset except for acrylics, is poured into a mold without pressure, cured, and taken from the mold. Cast thermoplastic films are produced via building up the material (either in solution or hot-melt form) against a highly polished supporting surface. Low mold cost, capability to form large parts with thick cross sections, goodsurface finish, and convenient for low-volume production.Centrifugal casting离心浇铸 Reinforcement is placed in mold and is rotated. Resin distributed through pipe; impregnates reinforcement through centrifugal action. Utilized for round objects, particularly pipeCoating被覆 Process methods vary. Both thermoplastics and thermosets widely used in coating of numerous materials. Roller coating similar to calendering process. Spread coating employs blade in front of roller to position resin on material. Coatings also applied via brushing, spraying, and dipping.Cold pressure molding冷压力成型 Similar to compression molding in that material is charged into a split mold; it differs in that it employs no heat, only pressure. Part cure takes place in an oven in a separate operation. Some thermoplastic billets and sheet material are cold formed in a process similar to drop-hammer die forming or fast cold-form stamping of metals. Low-cost matched-tool moldings exist which utilize a rapid exotherm to cure moldings on a relatively rapid cycle. Plastic or concrete tooling can be used. With process comes ability to form heavy ortough-to-mold materials; simple, inexpensive, and often has rapid production rate.Compression molding模压成Principally polymerized thermoset compounds, usuallypre-formed, is positioned in a heated mold cavity; the mold is型 closed (heat and pressure are applied) and the material flows and fills the mold cavity. Heat completes polymerization andthe part is ejected. The process is sometimes used forthermoplastics. Little material waste is attainable; large, bulkyparts can be molded; process is adaptable to rapidautomation (racetrack techniques, etc.)Encapsulation 封装成型 Mixed compound is poured into open molds to surround and envelope components; cure may be at room temperature with heated postcure. Encapsulation generally includes several processes such as potting, embedding and conformal coating.Extrusion molding挤出成型 Widely used for continuous production of film, sheet, tube, and other profiles; also used in conjunction with blow molding. Thermoplastic or thermoset molding compound is fed from a hopper to a screw and barrel where it is heated to plasticity then forwarded, usually via a rotating screw, through a nozzle possessing the desired cross section. Production lines require input and takeoff equipment that can be complex. Low tool cost, numerous complex profile shapes possible, very rapid production rates, can apply coatings or jacketing to core materials (such as wire).Filament Excellentstrength-to-weight. Continuous, reinforcedwinding filaments, usually glass, in the form of roving are saturated with resin and machine-wound onto mandrels having shape ofdesired finished part. Once winding is completed, part andmandrel are cured; mandrel can then be removed throughporthole at end of wound part. High-strength reinforcementscan be oriented precisely in direction where strength isrequired. Good uniformity of resin distribution in finished part;mainly circular objects such as pressure bottles, pipes, androcket cases.Injection molding注塑成型 Very widely used. High automation of manufacturing is standard practice. Thermoplastic or thermoset is heated to plasticity in cylinder at controlled temperature, then forced under pressure through a nozzle into sprues, runners, gates, and cavities of mold. The resin undergoes solidification rapidly, the mold is opened, and the part ejected. High production runs, low labor costs, high repoducibility of complex details, and excellent surface finish.Laminating 层合成型 Material, usually in form of reinforcing cloth, paper, foil, metal, wood, glass fiber, plastic, etc., preimpregnated or coated with thermoset resin (sometimes a thermoplastic) is molded under pressure greater than 1000psi (7Mpa) into sheet, rod, tube or other simple shapes. Excellent dimensional stability offinished product; very economical in large production of parts.Matched-die- molding A variation of the conventional compression molding this process employs two metal molds possessing a close-fitting, telescoping area to seal in the plastic compound being molded and to allow trim of the reinforcement. The mat or preform reinforcement is positioned in the mold and the molds is closed and heated under pressures of 150-400 psi (1-3 Mpa). The mold is then opened and the part is removed.Pultrusion This process is similar to profile extrusion, but it does not provide flexibility and uniformity of product control, and automation. Used for continuous production of simple shapes (rods, tubes, and angles) principally incorporating fiberglass or other reinforcement. High output possible.Rotational molding滚塑成型 A predetermined amount of powdered or liquid thermoplastic or thermoset material is poured into mold; mold is closed, heated, and rotated in the axis of two planes until contents have fused to inner walls of mold; mold is then opened and part is removed. Low mold cost, large hollow parts in one piece can be produced, and molded parts are essentially isotropic in natureSlush molding 搪塑Powdered or liquid thermoplastic material is poured into a mold to capacity; mold is closed and heated for apredetermined time in order to achieve a specified buildup of partially cured material on mold walls; mold is opened and unpolymerized material is poured out; and semifused part is removed from mold and fully polymerized in oven. Low mold costs and economical for small production runs.Thermoforming 热成型Heat-softened thermoplastic sheet is positioned over male or female mold; air is evacuated from between sheet and mold, forcing sheet to conform to contour of mold. Variations are vacuum snapback, plug assist, drape forming, etc. Tooling costs are generally low, large part production with thin sections possible, and often comes out economical for limited part production.Transfer molding传递模塑成型Related to compression and injection molding processes. Thermoset molding compound is fed from hopper into a transfer chamber where it is then heated to plasticity; it is then fed by a plunger through sprues, runners, and gates into a closed mold where it cures; mold is opened and part ejected. Good dimensional accuracy, rapid production rate, and very intricate parts can be produced.Wet-lay up or contact molding Several layers, consisting of a mixture of reinforcement (generally glass cloth) and thermosetting resin are positioned in mold and roller contoured to mold’s shape; assembly isusually oven-cured without the application of pressure. Inspray molding, a modification, resin systems and choppedfiber are sprayed simultaneously from a spray gun against themold surface. Wet-layup parts are sometimes cured underpressure, using vacuum bag, pressure bag, or autoclave, anddepending on the method employed, wet-layup can be calledopen molding, hand layup, sprayup, vacuum bag, pressurebag, or autoclave molding. Little equipment required, efficient,low cost, and suitable for low-volume production of parts./classselection/interpretationscontent.aspPLASTICS MANUFACTURING OR PROCESSING Calendering: Plastic Material is compounded in a Banbury mixer, which is a housing around two eccentric rolls. After the material is introduced a weight is applied to the top of the material and the mechanical motion and heating causes the material to soften and become plastic. This material is dumped and usually goes to "warming" rolls which are usually two roll mills similar to those found in making rubber. From here the material is fed into calender rolls and comes out as a uniform thick sheet. It can be passed through embossing rolls to imprint a pattern. It is then passed over a series of cooling cans, and is wound into rolls.Casting: There are several methods and the most common are discussed below:(a) Cold Casting: Liquid plastics or resins are mixed with inert materials such as clays, limestone or marble chips. The plaster-like material is then trowelled, or otherwise applied to a thick shape or mold. After air curing the item is removed, finished by grinding, sawing or filing.(b) Foam Casting: A mixture of plastics such as Urethane and a foaming agent are introduced into the bottom of a mold, which is closed and clamped. They may be passed through an oven or the reaction of the liquid may cause enough heat to expand and fill the mold. The molds are then opened, the pieces removed and cleaned to remove the flash at the mold parting line. Foam casting can also be done by running the mixed liquid onto paper on a moving conveyor. This is then passed through an oven where it rises and loses any volatiles, and cures. At the end of the oven, the material is cut into a sheet or coiled into rolls.c) Sheet Casting: A liquid plastic such as an Acrylic resin is poured between glass panels which acts as a mold. These are placed in hot vats until the plastic polymerizes and solidifies. The glass is removed, the plastic is cut into strips, and stamped, usually in power presses, to form buckles or buttons for ladies dresses.Extrusion: In this process a continuous flow of molten plastic is formed through a shaped opening called a die, and the plastic is then cooled. Depending on the shape of the opening, many different parts can be made. If the opening is like a ring, a tube or pipe can be made. If the opening is a long thin slit, a sheet may be formed. While the die determines the shape of the plastic flow, many different methods are used "down stream" to make different types of parts. In some instances a cooling bath may be used while at other times air jets, water sprays, fans, vacuum pulling conveyor is used to pull the extrusion along the line. As the part leaves the "take off" it may be sawed to special lengths, coiled, spooled, sheared or punched, depending on the requirements of the piece. Fabrication:Cutting, cementing or heat sealing: Plastic sheets are cut on wood working types of machines, then cemented, glued or heat sealed to form final assemblies. Finished sheets can be cut in the dies of various presses such as is used in the leather, textile or metal forming industries. These parts can be glued, heat sealed, or embossed to form a variety of items such as, file folders, panels for auto interiors, tarpaulins, etc.(b) Machining or grinding: Extruded rods, tubes, etc. are machined on lathes, screw machines or grinders to form beads, tubes, balls, etc. as final parts or products.Molding (or Forming): The term "molding" is often applied to operations that do not involve power presses and probably are more accurately described as "forming" or "fabrication." Code 4484 applies to the former; code 4452 to the latter. There are a variety of methods and although not necessarily all-inclusive, the listing below should describe most that would be encountered:(a) Blow Molding: This is a modification of injection molding and presently involves forming in one of two methods. The first involves extruding a tube of heated soft plastic which is gravity fed into the open mold. The operation is timed so that the molds are closed over the material, air is injected into it thereby forcing the plastic to conform to the shape of the mold. The molds are then cooled and the finished part removed. A modification of this is the forming of the soft heated plastic (parison) over a plug through which air is injected forcing the material into the shape of the mold.(b) Cold Molding: This involves coating a mold of metal or wood with a "release" of some type followed by a "gel coat." After this layer of reinforcing material such as glass cloth or fibers and liquid resins are added to build the thickness desired. The items either air dry or cure and are then removed from the mold or form.(c) Compression Molding: Molds are mounted in hydraulic presses, usually with a vertical stroke. Plastic powders, granules, pellets or bricketts are introduced into the lower cavity of the mold, the press is closed and at the end ofthe cycle the press is opened and the parts removed either by hand or by an unloading tray. The parts are finished by cleaning the "flash" at the end of the mold parting line by tumbling, filing, sanding or machining.(d) Dip Molding: This is an outgrowth of the latex dipping industry. Involves dipping a mold into liquid plastic to form a deposit in the shape of the mold. The deposit is then blown from the mold, cut to size and finished.(e) Foam Molding: A set of molds are mounted in a hydraulic or pneumatic press. After the mold is closed, partially expanded beads of polystyrene are blown or sucked into the mold cavities. The molds are heated with steam, the beads expand further to fill the cavities. The molds are then cooled, opened and the finished parts removed.(f) Injection Molding: Hydraulic presses are used to open and close a set of molds. The plastic material in the form of granules or pellets are introduced into the hopper of an extruder. After the press is closed, the extruder forces the molten plastic into the molds through a series of runners and gates to the individual cavities. The molds are cooled by circulating water and opened and the parts removed after sufficient cooling.(g) Rotational Molding: So-called because it involves rotating the molds while in the oven and prior to cooling in a water bath. In the process a measuredamount of liquid is introduced into thin walled metal molds which are then closed and placed in a heated oven. At the same time the molds are rotated so that the liquid comes in contact with the entire inner surface of the mold. After sufficient time, the molds are removed from the oven, opened and the hollow items with an external shape like the inside of the mold are removed. The items are cleaned by using a wire brush and usually decorated with paints or enamels. This method is considered the ideal process for producing completely enclosed hollow parts and used extensively for manufacturing dolls and toys, promotional and premium items, pharmaceutical components, automotive and industrial parts.(h) Slush Molding: See Rotational Molding which is a modification of slush molding and has often replaced it.(i) Transfer Molding: A modified type of compression molding. Instead of loading the thermosetting material directly into the mold, it is first heated to the melting point but below the setting temperature and injected in a liquid state into a closed hot mold. This is accomplished by forcing the liquified material into the orifice of the mold via a pressure cylinder. A big advantage in transfer molding is in the case of complicated parts employing inserts. If a straight compression molding process were employed in such instances, the uneven flow of the compound as pressure is applied would tend to tear inserts from supports. Transfer molding, on the other hand, allows an even flow of the liquified materialthrough the contours of the mold without interference with the position of inserts or other mold parts.(j) Vacuum Molding: Sheets of plastic are softened in an oven, and then placed over a mold of wood or metal. A vacuum is formed in the space between the mold and the plastic sheet, and the plastic is drawn down to take the conformation of the mold. After sufficient cooling time, the piece is removed. The formed part must then be removed from the rest of the sheet by sawing or stamping.Filament Winding: This method is used to produce tanks that can be quite large or ducts for the chemical industry. Usually wooden molds are made and mounted so they can be rotated. Filaments of glass, nylon or other fibrous material are passed through a bath of liquid resin, then spirally wound onto the rotation form until the desired thickness is obtained. After the resin cures, the item is removed from the mold or form.Fluidizing: Low pressure air is passed through very fine solid plastic to cause it to "fluidize." Heated metal parts are then lowered into this plastic. The plastic melts and sticks to the surface of the metal. The temperature and time regulate the thickness of the coating.Plastic Laminating: This process is used in making products such as building panels, kitchen counter tops and restaurant table surfaces, etc. There are twomain processes:(a) High Pressure Laminating: This involves combining together with plastic resins layers of fibrous materials such as fabric, paper, glass fibers or other materials to form a sandwich which is fused in a press under high heat and pressure which serves to cure the plastic and set the laminate into permanent rigid form.(b) Reinforced Materials: This process involves placing pieces of glass fiber cloth or mat, paper or other material, soaked with liquid plastic, on a form or mold the shape of the end product. Although methods differ, it is possible to harden the material into permanent shape at room temperature with little or no pressure. This process makes possible the production of larger plastic products as big as a boat hull or oil truck tank body.Plastisol Processing: Plastisols are dispersions of polyvinyl chloride resin in a plasticizer. Other ingredients include stabilizers, pigments and fillers. There are three methods of molding with vinyl plastisols; rotational, slush and dip. It is possible that some items can be produced by any of the three e.g. bicycle hand grips. Rotational and slush molding are more closely related. Rotational is a modification of slush molding and has often replaced the latter. Dip molding on the other hand is an outgrowth of the latex dipping industry and has come back into being because of the particular qualities of vinyl.Plastic FamiliesThere are two basic families of plastics: Thermoplastic materials and Thermo set materials.Thermoplastics soften and melt upon the addition of heat.Upon removal of heat they then again stiffen and harden into a new shape. The Thermoplastic family is what most people relate to when they think about plastics because of the many domestic products that are produced from them. What red blooded American male does not have first hand experience with this family of plastics when as a child built Revelle models of boats, cars or other objects and then lit them on fire only to end up with an amorphous blob?The injection molding technique was developed to efficiently process this family of plastics into the many useful products we use everyday. Some of the commonly used thermoplastics are polyethylene, polypropylene, polystyrene, PVC, ABS and Nylon to name a few. There are countless other engineered plastic materials and compounds to suit broad varieties of applications.Southwest Plastics has extensive injection molding capabilities for thermoplastic materials.Thermosets harden and cure in the molding process as the molecules actually crosslink in a chemical reaction and set into a final shape. No addition of heat will soften or melt the material. As a result, thermosets have their advantage in any high heat environment where softening or melting cannot be tolerated. Domestically products such as ash trays, cooking utensils and cookware handles are produced from thermosets. Industrially thermosets are used in electrical, electronic and military applications. Some examples of thermoset materials are phenolics, epoxys, melamines and diallylphthalates.Thermosets can be molded using the compression, transfer or injection molding processes.Southwest Plastics has extensive capabilities in molding thermoset materials using all three of these processes.Processing MethodsIn order to transform plastic materials into usable shapes, many methods of processing plastics have been developed including the following: Injection molding, compression molding, transfer molding, blow molding, thermoforming, vaccu-forming, extrusion, and blown film. Each of these processes require specific expertice and skill. Southwest Plastics has expertise in COMPRESSION, TRANSFER, and INJECTION molding.Compression Molding is the first technique developed in the early 1900s to mold Bakelite (phenolic) molding compounds. It is used today to process many varieties of thermoset plastics and composites including phenolic, epoxy, melamine, and diallyl phthalate. The compression molding press is simply a vertically oriented hydraulic press. The compression mold is clamped into the compression molding press, and is simple in that it consists of two halves: the cavity and the force or core on the opposite side. The mold is heated to the temperature as specified by the material manufacturer which is usually around 300° F, and the material is placed directly in the cavity. The mold is then closed under pressure compressing the material and causing it to flow into the void between the cavity and the core. The mold is held closed for several minutes (depending on the material used and the wall thickness of the part) while the material is curing or "setting" into the form of the mold surface. The mold is then opened and the part ejected from the mold cavity. Compression molding lends itself to relatively simple parts, but since there are no sprues, runners or gates through which the material must flow, the material can be heavily loaded with a composite of fillers and fibrous reinforcements which remain in a random orientation in the molded part resulting in superior strength properties.Transfer Molding is another method for molding thermoset materials where the design of the part is too complicated or unsuitable for compressionmolding. Transfer molding is often used when metal inserts, studs, connector pins wear plates, electronic components or other parts are molded into the part. With transfer molding, the mold is clamped closed first. The material charge is then loaded into a loading "pot" which is connected to the cavity with a short runner. The material is then "transferred" from the pot to the cavity via the runner under pressure exerted from a plunger which is hydraulically actuated against the material which has been loaded in the pot.Injection molding is a high production method of producing a vast variety of thermoplastic parts into shapes ranging from fairly simple to quite complex. Injection mold cavities are fed with melted plastic material which is forced under high pressure through a sprue which feeds a runner system then through a gate into the cavity. The material is then cooled to the point that the material is solid and then ejected from the mold as a finished part. Certain thermoset materials can also be injection molded after several modifications to the standard injection molding machine are affected. The injection molding machine consists of two basic components: the clamp unit and the injection unit. The clamp unit holds and clamps the tool into position while the injection unit plasticizes and injects the material into the mold which has been positioned by the clamp unit. The clamp force must be sufficient to hold the mold closed against the hydraulic pressure of the material being injected under high pressure bythe injection unit. The rule of thumb is that there must be three tons of clamp force for every square inch of cavity projected area in the mold. Both units are coordinated by a computer controller on the machine which is programmed to efficiently to produce high quantities of consistent quality parts on an automated cycle.Southwest Plastics has been in business for over 50 years and has extensive experience in both thermoset and thermoplastic materials. We have a state of the art facility and offer molding services using compression, transfer and injection molding techniques. Let us work with you on your next project so we can become your "plastics partner"./subpage.asp?cat=3&id=37Da/Pro Rubber, Inc. offers compression molding of rubber compounds. Compression molding consists of a top and bottom plate mold that is machinedto a custom configuration (fig. 1). An elastomer preform is added between the plates and the plates are compressed under heat and pressure for a specific amount of time. The Da/Pro process monitors variables closely and adjusts to compensate for variable differences during each cycle. After the elastomer is cured properly, the mold is opened, the part is removed, the mold cleaned and the cycle repeated.Fig. 1Da/Pro Rubber, Inc. offers transfer molding of rubber compounds. Transfer molding consists of a mold cavity similar to a compression mold. In addition, the mold contains a transfer pot and a ram, where the rubber material is placed before compression. The mold cavity contains transfer holes, which connect to the transfer pot through sprues (fig. 2). During molding, the ram is compressed and compounded rubber material flows through the sprues into the mold cavity where under heat and pressure the rubber compound cures into the mold cavity configuration. Similar to compression molding, the Da/Pro process monitors all variables and compensates for differences during each cycle. After the elastomer is cured properly, the mold cavity is opened, the part is removed, the sprue is removed, the transfer pot and mold cavity are cleaned and the cycle repeated.Fig. 2Each process has advantages and disadvantages. Our experienced staff of engineers, chemists and salesmen can answer all of your questions and concerns with any of your molding needs - contact us.Compression MoldingCompression Molding has been used for many years and is a common method for thermosetting plastics or permanently hardening plastics by heating them. Compression Molding has been used in the auto industry for over 25 years and is employed in the creation of a wide variety of products including phonograph records, rubber tires, roofs, fenders, spoilers and knee replacements, to name just a few.How Does It Work?The first step in Compression Molding is loading a carefully measured amount of the chosen molding compound, called the Charge, into the bottom portion of your preheated mold. The Charge may take the form of powder, pellets, liquid or preform and should be fully formulated requiring no extra preparation to mold.Once the Charge is in place, the two halves of the mold are brought together, forcing the Charge to conform to the shape of the mold. The Charge is compressed and heated until solidified and cured into the。
