Plastic product classification (according to the physicochemical properties of classification)

Classified by physicochemical properties

    According to a variety of different physical and chemical properties of plastic, you can put plastic into thermosetting plastics and thermoplastic plastics types.

    ⑴ thermosetting plastics

    It refers thermosetting plastics under heat or other conditions can be cured or with insoluble (melt) plastic characteristics, such as phenolics, epoxy plastic. Thermosetting plastic was divided formaldehyde cross-linking and other cross-linking of two types. When heated to soften, harden when cooled, can repeatedly soften and harden and maintain a certain shape. Soluble in certain solvents, having a fusible soluble nature. Thermoplastics with excellent electrical insulation properties, in particular polytetrafluoroethylene (PTFE), polystyrene (PS), polyethylene (PE), polypropylene (PP) has a very low dielectric constant and dielectric loss, should for use as a high-frequency and high-voltage insulation material. Thermoplastic easy molding, but low in heat resistance, easy to creep, with the degree of creep under load, the ambient temperature, the solvent, the humidity varies. To overcome these weaknesses thermoplastics, meet the need of space technology, new energy development and other fields, countries are developing melt molding heat-resistant resin, such as polyether ether ketone (PEEK), polyether sulfone (PES) , polyarylsulfone (PASU), polyphenylene sulfide (PPS) and the like. To them as a matrix resin composite material having high mechanical properties and chemical resistance, thermoforming and welding between energy, interlaminar shear strength is better than epoxy resin. As with PEEK as a matrix resin and carbon fiber composite materials, the fatigue resistance than epoxy / carbon fiber. Its good impact resistance, excellent creep resistance at room temperature, process, and can be used continuously at 240 ~ 270 ℃, it is an ideal high temperature insulation material. It has high strength and hardness at 200 ℃ with PES as a composite material matrix resin and carbon fibers, at -100 ℃ can still maintain good impact resistance; non-toxic, non-flammable, fuming at least, radiation resistance Well, the key components for the spacecraft is expected to use it, but also molding into a radome and the like.

    Formaldehyde-crosslinked plastics include phenolics, aminoplasts (such as urea - formaldehyde - melamine - formaldehyde, etc.).

    Other cross-linked plastics include unsaturated polyesters, epoxy resins, diallyl phthalic acid resins and the like.

    ⑵ thermoplastic plastic

    Refers to thermoplastic plastics can be repeatedly softened by heating and hardened by cooling of the plastic, such as polyethylene, polytetrafluoroethylene or the like within a specific temperature range. Thermoplastic plastic was divided hydrocarbons, vinyl containing polar gene engineering, cellulose and other types. After thermo-forming insoluble infusible form a cured resin molecules by the linear structure of its cross-linked into a network structure. Thermal decomposition will again strengthen damage. Typical phenolic thermosetting plastic, epoxy, amino, unsaturated polyesters, furan, polysiloxane and other materials, as well as newer polyethylene phthalate and propylene carbonate plastic or the like. They have high heat resistance, heat easily deformed and so on. The disadvantage is that the mechanical strength is generally not high, but by adding fillers, made of laminate or molding material to improve its mechanical strength.

  Phenolic resin as the main raw material of thermosetting plastics, such as phenolic molded plastic (commonly known as Bakelite), with a durable, dimensionally stable, resistant to other chemicals in addition to strong base effects and other characteristics. According to different purposes and requirements, the addition of various fillers and additives. Such as requiring high insulation performance of varieties, can be mica or glass fiber as filler; to resistant varieties, may be asbestos or other heat-resistant filler; species such as seismic requirements, various appropriate fiber or rubber filler and a number of toughening agent to produce high toughness materials. Further aniline may also be used, epoxy, polyvinyl chloride, polyamide, polyvinyl acetal-modified phenolic resin, etc. to meet the requirements of different applications. It can also be made with phenolic resin phenolic laminate, which is characterized by high mechanical strength, good electrical properties, corrosion resistance, easy processing, widely used in low-voltage electrical equipment.

  Aminoplast have urea formaldehyde, melamine-formaldehyde, melamine urea formaldehyde. They have a hard, scratch-resistant, colorless, translucent, etc., can be added to products made of bright color pigment, commonly known as Bakelite. Because of its oil, affected by the weak base and an organic solvent (but not acid), long-term use at 70 ℃, short-term resistant to 110 ~ 120 ℃, can be used electrician products. Melamine formaldehyde plastic plastic hardness than urea formaldehyde, have better water resistance, heat resistance, arc resistance, arc resistant insulating material can be used.

  Epoxy resin as the main raw material of thermosetting plastic varieties, many of them with a bisphenol A type epoxy resin as a base of about 90%. It has excellent adhesion, electrical insulation, heat resistance and chemical stability, shrinkage and water absorption, good mechanical strength and other characteristics.

  Unsaturated polyester and epoxy resins can be made of glass steel, it has excellent mechanical strength. Such as unsaturated polyester, glass, steel, good mechanical properties, low density (only 1/5 to 1/4 of steel, aluminum, 1/2), easily processed into a variety of electrical components. Electrical and mechanical properties of plastics to phthalate acrylate resin are better than phenolic and amino thermoset plastic. It is hygroscopic small, products dimensional stability, good moldability acid and boiling water and some organic solvents. Molding plastic suitable for manufacturing complex structure, both have high temperature insulation parts. Usually long-term use in the temperature range of -60 ~ 180 ℃, the heat levels up F grade to H level, higher than the phenolic and amino plastic heat resistance.

  Polysiloxane structure in the form of silicone plastic used more often in Electronics & Electrical Technology. Silicone laminated plastic over glass cloth as reinforcement material; silicone molded plastic over glass fibers and asbestos packing, for the manufacture of high temperature, high or submersible motors, electrical appliances, electronic equipment parts. Such plastics are characterized by a small dielectric constant and tgδ value, by the frequency of small, for electricians and electronics industry corona resistance and arc discharge even cause decomposition, the product is capable of conducting silica rather than carbon black ʱ?? Such materials have outstanding heat resistance, can be used continuously at 250 ℃. The main disadvantage of polysiloxane is low mechanical strength, adhesiveness small, oil poor. Has developed a number of modified silicone polymers, such as plastics, polyester-modified silicone technology has been applied in the electrician. Some plastic both thermoplastic and thermosetting plastics. Such as polyvinyl chloride, usually thermoplastics, Japan has developed a new type of liquid PVC is thermosetting molding temperature of 60 ~ 140 ℃; Lund plastic American called Alex, both thermoplastic processing features, there are the physical properties of thermoset plastics.

    ① hydrocarbon plastics. Is a non-polar plastics, crystalline and non-crystalline points, crystalline hydrocarbon plastics include polyethylene, polypropylene, non-crystalline hydrocarbon plastics, including polystyrene and the like.

    ② vinyl plastic containing polar gene. Fluorine plastic, most non-crystalline transparent body, including polyvinyl chloride, polytetrafluoroethylene, polyvinyl acetate and the like. Most vinyl-based monomer may be polymerized using a free radical catalyst.

    ③ engineering thermoplastics. Including polyoxymethylene, polyamide, polycarbonate, ABS, polyphenylene oxide, polyethylene terephthalate, polysulfone, polyether sulfone, polyimides, polyphenylene sulfide and the like. Polytetrafluoroethylene. Modified polypropylene or the like are also included in this range.

    ④ thermoplastic cellulose-based plastics. It includes cellulose acetate, cellulose acetate butyrate, celluloid, cellophane and the like.

Third, according to the processing method of classification

    According to the different kinds of plastic molding methods can be divided into membrane pressure, lamination, injection, extrusion, blow molding, reaction injection molding plastics and other types of plastic.

    Membrane pressure, mostly plastic processing performance and general properties similar to solid plastic plastic; laminated plastic means of fabric impregnated with resin, the laminated, hot materials incorporated as a whole; injection, extrusion and blow mostly plastic properties and processability of thermoplastics with generally similar plastic; means capable of molding plastic under no pressure or little pressure, poured in a mold shaped article can harden into a liquid resin mixture, such as MC nylon; Reaction Injection plastic material with a liquid, the membrane cavity injection pressure, and allowed to react solidified into shaped articles of plastic, such as polyurethane or the like.

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Plastic products category (by using the characteristics of classification)

First, by using the characteristics of classification

Plastic Product Categories

    According to name different types of plastics used feature, usually plastic into common plastics, engineering plastics and specialty plastics three types.

    ① GE Plastics

    Generally refers to the production of large, versatile, forming a good, cheap plastic. GE Plastics has five varieties, namely polyethylene, polypropylene, polyvinyl chloride, polystyrene and ABS. They are thermoplastics.

    ② plastic

    Generally it refers to can withstand external force, has good mechanical properties and resistance to high and low temperature properties, good dimensional stability, can be used as plastics engineering structures, such as polyamide, polysulfone and the like.

    In turn divided into general-purpose engineering plastics engineering plastics and special engineering plastics into two categories.

    General engineering plastics include: polyamides, polyoxymethylene, polycarbonate, modified polyphenylene ether, thermoplastic polyester, ultra high molecular weight polyethylene, methylpentene polymer, vinyl alcohol copolymer.

    Special engineering plastics have crosslinked non-crosslinked type of points. Crosslinked include: polyamino bismaleamic, poly triazine, crosslinked polyimide, heat-resistant epoxy resin and other means. Non-crosslinked include: polysulfone, polyether sulfone, polyphenylene sulfide, polyimide, polyether ether ketone (PEEK), etc.

    ③ special plastic Dongguan, Dongguan website design Dongguan website construction site promotion site optimization Dongguan Dongguan high Po site construction Liaobu Dongguan Dongcheng site construction site construction site construction Dasan Dongguan Shijie Shilong Dongguan website construction site construction site construction Houjie Dongguan Ridge Hill site construction Zhangmutou Tangxia site construction site construction site construction Maoming Maoming Maoming site design site promotion Shenzhen printing stickers printed Shenzhen, Dongguan, Dongguan printing business card printing

    Generally refers to a special function, it can be used for plastic aviation, aerospace and other special applications. Such as fluorine plastic and silicone has outstanding high temperature, self-lubricating and other special functions, reinforced plastics and foams with special properties of high strength, high damping, these plastics are all areas of specialty plastics.

    a strong plastic: reinforced plastic material in the shape can be divided into granular (eg Gaisu reinforced plastics), fibers (such as glass fiber or glass cloth-reinforced plastic), the sheet (such as mica reinforced plastics) three. Press material can be divided Burkina reinforced plastic (such as rags to enhance or asbestos reinforced plastics), inorganic mineral-filled plastic materials (such as quartz or mica filled plastic), fiber reinforced plastics (such as carbon fiber reinforced plastics) three.

    . b Foam: Foam can be divided into rigid, semi-rigid and flexible foams three. Rigid foam no flexibility, compression great hardness, only up to a certain stress was deformed, not restitution after stress relief; soft foam full flexibility, compression hardness is small, it is easily deformed, stress relief after energy restitution, residual deformation small; hard between his soft foam semi-rigid foam between flexibility and other properties.

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Injection mold Features

① core cavity and a three-dimensional profile. External and internal shape of plastic parts by direct molding cavity and core of these complex three-dimensional surface machining more difficult, especially within the cavity molding surface machining blind hole, if the traditional processing methods, not only requiring high skill level of workers, auxiliary fixtures more tools and more, and a long processing period.

② accuracy and surface quality requirements, long service life requirements. Currently dimensional accuracy requirements are generally plastic parts for 1T6? 1T7, dimensional precision surface roughness Ra0.2-0.1um injection mold parts required to achieve 1T5? 1T6, surface roughness Ra0.1um less. Long-life plastic injection mold for mention Gao efficiency and reduce costs necessary to present the life of the injection mold generally require more than one million times. Precision injection molding to use the stiffness of the mold. Increase the thickness of the template Increasing support column or cone positioning

Element to prevent deformation of the mold under pressure, internal pressure can sometimes reach lOOMPa. Top of the device is an important factor affecting the product deformation and dimensional accuracy, so you should choose the best top of the point to make uniform throughout the release. Precision injection molds most used in the structure or spelling mosaic structure, which requires precision mold parts interchangeability are greatly improved.

③ long process, the manufacturing time is tight. For injection molded parts, mostly with other components to form a complete package of products, and in many cases are in other parts have been completed, the eagerly awaiting public on supporting injection molded parts. Because of the product's shape or size of high precision, combined due to the characteristics of the resin material is different, after the completion of mold manufacturing, also requires repeated tryout and revision, enabling developers and delivery time is very tight.

④ remote design, remote manufacturing. Mold manufacturing is not the ultimate goal, but to present the final product design, mold making factory according to user requirements design and manufacture molds by the user, and in most cases, the products of other manufacturers also produce injection. This situation resulted in the design, mold design and manufacture products, production of products carried out in different places.

⑤ specialization, dynamic combination. Mold production volume is small, generally belong to a single piece of production, but the mold needs a lot of standard parts, large mold, small thimble, these should not and can not just be done by a single manufacturer, and manufacturing process complexity, general equipment and CNC devices use very uneven.

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Injection molding processing considerations (b)

Third, the crystalline thermoplastics no crystallization phenomenon can be divided into crystalline and non-crystalline plastics (also known as amorphous) plastic according condensation occurs when two categories. The so-called phenomenon of crystallization from the molten state to the plastic is condensed, the molecules move independent, completely unordered state, stops the free movement of molecules into, according to a fixed position slightly, and there is a tendency to make the molecular arrangement becomes a formal model phenomenon. As discriminating these two types of standard visual appearance of plastic transparent plastic thick plastic parts, generally crystalline material is opaque or translucent (such as POM, etc.), the amorphous material is transparent (such as PMMA, etc.). But there are exceptions, such as poly (4) methyl pentene to crystalline plastics there is a high transparency, ABS is an amorphous material but not transparent. Design and selection of the injection molding machine mold should pay attention to crystalline plastics have the following requirements and considerations:

① temperature rises to more heat molding temperature required, use the plasticizing capacity of the device.

② release when cooled back of the heat, to cool sufficiently.

③ molten and solid big difference in specific gravity, forming large shrinkage, prone to shrinkage, porosity.

④ cooling fast, low crystallinity, shrinkage, high transparency. The degree of crystallinity and related plastic wall thickness, thickness is slow cooling, high crystallinity, shrink large, good physical properties. So the crystalline material should be required to mold temperature must be controlled.

⑤ significant anisotropy, internal stress. After the release of the molecule has not crystallized continued tendency to crystallize, in energy imbalance, prone to distortion, warping.

⑥ crystallization temperature range is narrow, prone to not melt the end of the injection mold or clogged inlet. Fourth, the heat-sensitive plastic and susceptible to hydrolysis plastic

4.1 heat-sensitive means some plastics are more sensitive to heat, long time at a high temperature heating or inlet cross-section is too small, large shear, solid color temperature increased prone to degradation, decomposition tendency, with this feature plastic called heat-sensitive plastic. Such as hard PVC, polyvinylidene chloride, vinyl acetate copolymer, POM, polychlorotrifluoroethylene and the like. Heat-sensitive plastic decomposition by-products generated when monomers, gaseous, or solid, in particular, some decomposition of the gas on the human body, equipment, molds are stimulated, corrosive or toxic effects. Therefore, mold design, injection molding machines and molding the choice should be noted, should use screw injection molding machine, injection system should be large cross-section, molds and chrome barrel should not be there * angle hysteresis material, must strictly control the molding temperature, plastic the addition of stabilizers, weaken its thermal performance.

4.2 Some plastic (e.g. PC) containing a small amount of water, even, but at a high temperature, high pressure will be decomposed, this performance is called easily hydrolyzable, which must be pre-heated and dried. Fifth, stress cracking and melt fracture

5.1 Some plastic to stress sensitivity, easy to produce internal stress during molding and crisp and easy to crack, plastic parts in the external force or cracking which occurred in a solvent. To this end, in addition to improving additives in the feed opening crack resistance, the raw material should note dried, reasonable choice molding conditions to reduce stress and increase resistance to cracking. And should choose the right shape of plastic parts, inserts and other measures should not be set to minimize the stress concentration. Mold design should increase the stripping slope, choose a reasonable inlet and ejector mechanism, molding material temperature should be appropriately adjusted, mold temperature, injection pressure and cooling time, try to avoid too cold brittle plastic stripping , molded plastic parts also should be treated after improving crack resistance, eliminate stress and prohibiting contact with the solvent.

5.2 When some melting of the polymer melt flow rate at constant flow rate through the nozzle orifice exceeds a certain value, the apparent melt surface transverse cracks called melt fracture, undermine appearance and physical properties of plastic parts. Therefore, in the selection of high melt flow rate polymers and the like, should be increased nozzle, runner, inlet cross-section to reduce the injection speed, material temperature increase. Sixth, thermal properties and cooling rate

6.1 There are different kinds of plastic specific heat, thermal conductivity, heat distortion temperature thermal properties. High specific heat of plastics requires heat, should be used plasticizing capacity of the injection molding machine. High heat distortion temperature plastic cooling time can be as short, releasing early, but after stripping to prevent deformation during cooling. Low thermal conductivity of plastic cooling rate (such as ionic polymers slow cooling rate), it must be cooled sufficiently to strengthen the mold cooling effect. Hot runner mold for low specific heat, high thermal conductivity of plastics. Large specific heat, thermal conductivity, low thermal deformation temperature is low, slow cooling is not conducive to high-speed plastic molding, injection molding machine must use the appropriate and strengthen the mold cooling.

6.2 All kinds of plastic and plastic parts according to their shape characteristics of the types, requirements must maintain proper cooling rate. So mold heating and cooling systems must be set according to molding requirements to maintain a certain mold temperature. When the material temperature should be raised when the mold temperature is cooled to prevent deformation of plastic parts after stripping, reduce cycle time, reduce the crystallinity. When the plastic is not sufficient to heat the mold to maintain a certain temperature, the mold should be provided with a heating system, the mold is maintained at a constant temperature to control the cooling rate, ensure liquidity, improve conditions or to control the filling plastic allowed to cool slowly, thick-walled plastic parts inside and outside to prevent uneven cooling and improve the crystallinity degree. Good liquidity, large forming area, press the uneven temperature materials molding plastic case is sometimes used interchangeably to be heated or cooled or local heating and cooling and use. For this reason the mold should be provided with appropriate cooling or heating system.

Seven, hygroscopic

Plastics additives due to different degrees of water affinities, so the plastic can be divided into moisture, water and non-absorbent adhesion is not easy to adhere to the two water and feed water content must be controlled within the allowable range within, or in high temperature, high pressure water into the gas or the occurrence of hydrolysis, the resin foaming, poor decreased mobility, appearance and mechanical properties. So hygroscopic plastic must require appropriate heating methods and specifications for preheating, when using to prevent further moisture.

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Injection molding processing considerations (a)

First, the shrinkage in the form of thermoplastic molding shrinkage and calculations mentioned above, thermoplastic molding shrinkage factors are as follows:

1.1 plastic varieties thermoplastic molding process due to the volume change there crystallized form from the inside should be strong, frozen in a plastic residual stress, molecular orientation and strong factor, as compared with the contraction rate than thermoset Large, wide range of shrinkage, clear direction, while shrinkage contraction after molding, an annealing process or the humidity than the thermosetting plastic generally large.

1.2 The properties of the molded plastic parts in contact with the cavity surface melt immediately cooled to form the outer layer of low density solid shell. Due to the poor thermal conductivity of plastic, the inner plastic parts shrink slowly cooled to form large, high-density solid layer. So the wall thickness, cooling slowly, the thickness of the high density shrink large. In addition, the presence or absence of the insert and insert the layout, the number of directly affect the material flow direction, density, size distribution and shrinkage resistance, so characteristic of plastic parts shrink the size, direction greater impact.

1.3 feed inlet form, size, distribution of these factors directly affect the material flow direction, density, pressure and molding time feeding action. Direct feed, feed opening large cross-section (especially thick cross-section) is small but directional shrinkage large feed opening width and a short length directivity small. From the feed or the material flow direction is parallel port near large shrinkage.

1.4 molding conditions Mold temperature is high, the melt is cooled slowly, high density, shrink large, especially for crystalline materials due to high crystallinity, volume changes, so the greater the contraction. Mold plastic parts inside and outside temperature distribution and cooling and density uniformity is also related directly affect the size of each part shrinkage and directivity. The holding pressure and time of contraction greater impact, pressure, long time, small contraction but large directivity. Injection pressure is high, the melt viscosity difference is small, small interlaminar shear stress, elastic rebound after stripping large, it also may be appropriate to reduce the shrinkage, high temperature materials, large shrinkage, but the direction is small. Therefore, the adjustment factors at the time of molding temperature, pressure, injection speed and cooling time may be appropriate to change the plastic shrinkage. Mold design according to shrink the scope of various plastics, plastic wall thickness, shape, size and form feed inlet distribution, empirically determined plastic parts various parts of the shrinkage cavity size calculated again. For high-precision plastic parts and difficult to grasp shrinkage, generally preferable to mold design follows:

① plastic shrinkage take a smaller outer diameter, inner diameter shrinkage rate, whichever is greater, in order to leave room for a revised tryout.

② mold casting system to determine the form, size and molding conditions.

③ after handling plastic parts after treatment to determine the size of the change (measured after 24 hours must stripping).

④ the actual mold shrinkage correction.

⑤ try molding process conditions can be suitably changed slightly amended shrinkage values ​​to meet the requirements of plastic parts.

 Second, liquidity

2.1 thermoplastics mobility size, generally from molecular size, melt index, Archimedes spiral flow length, apparent viscosity and flow ratio (flow length / plastic wall thickness) and a series of index analysis. Small molecular weight, broad molecular weight distribution, poor regularity molecular structure, melt index, spiral flow length is long, the performance of low viscosity, the flow ratio of the fluidity like, name of the same plastic must check the specification determines its flowability applicability in injection molding. Press mold design requirements can be broadly used plastic liquidity into three categories:

① good liquidity PA, PE, PS, PP, CA, poly (4) methyl pentene;

② liquid medium polystyrene series resin (e.g., ABS, AS), PMMA, POM, polyphenylene ether;

③ illiquid PC, hard PVC, polyphenylene oxide, polysulfone, aromatic sulfone, fluorine plastic.

2.2 Liquidity various plastics also differ depending on the forming factors change, the factors that primarily affects the following points:

① high temperature material temperature is increased mobility, but also vary in different plastic, PS (in particular, the impact resistance and higher MFR values), PP, PA, PMMA, modified polystyrene (such as ABS, AS) , PC, CA and other plastics with large temperature changes liquidity. For PE, POM, the temperature increase or decrease their liquidity less affected. Therefore, the former should adjust the temperature in the molding to control liquidity.

② to increase the pressure of the melt injection pressure by the shearing effect, and also increases fluidity, especially more sensitive PE, POM, it should be adjusted to control the flow of the injection pressure during molding.

③ casting mold structure in the form of system, the size, layout, design of the cooling system, the melt flow resistance (e.g. type surface roughness, forehearth section thickness, shape of the cavity, exhaust systems), and other factors have a direct impact to the melt in the cavity The actual flow inside, where lower melt temperatures cause increased resistance to the flow of liquidity is reduced. Mold design should be based on the use of plastic flow, choose a reasonable structure. It can also control the material temperature during molding, mold temperature and injection pressure, injection speed and other factors to regulate the situation properly filled molding needs to meet.

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PP material requirements of injection molding machines and injection molding technology

Plastic raw materials are mainly particles melt processing, flow, cooling after shaping into finished products, is a cooling process after heating, but also to the process of changing the plastic particles from various shapes, the following will illustrate the various stages of the injection angles to process.

1. fuser unit heater (Heater) make raw material particles gradually melting into a fluid-like flow, mainly in various raw materials suitable for temperature control, the increase in temperature tends to become the raw material flow rate, increase efficiency but does not necessarily guarantee yield, We must obtain the appropriate balance. Another case of good results and characteristics of PP heat cracking, make the best material flowing smoothly when all production to die, in order to avoid the charge generating material shortage or reflux phenomenon, reflux representatives of material flow rate is faster than the output will eventually resulting in an average increase flow efficiency increase equal MFR, it is one of the available processing methods, but also caused abnormal distribution MFR may lead to increased stability, resulting in poor rate may increase. However, because the application of PP finished relationship is not very high dimensional precision products, so the impact is not great.

2. Screw PP screw machining vast majority are driven by liquidity, so the design influence of the screw is very large, aperture size affect output volume, the compression ratio can also affect the size of the impact pressure and finished products output volume effect, which also includes a variety of materials (masterbatch, additives and modifier) ​​mixing effect. Material flows mainly by warmer, but turning friction materials to create friction heat will cause liquidity to accelerate, so the flow is smaller than the small screw compression drive, the speed must increase caused by friction heat must be better than the compression ratio of the screw more. So often we say plastic processing no master, try to understand who is the master machine performance. Not just the heater to heat the raw material only, it must be connected to the friction heat and smothering stay time and count. So it is practical problems, problem solving and experience contribute to the production efficiency. Screw mixing effect is particularly good if you need to, sometimes two-stage design different screw or twin-screw and screw is divided into segments to achieve a variety of different forms of mixing effect.

3. The mold or die plastic mold again relies on stereotypes or die, injection molding is a perspective view of the finished mold is also more complex and more to consider the shrinkage problem, others are all flat, strip, needle-like continuous product die If the special shape is classified as abnormal, you need immediate attention cooling stereotypes. Most plastics machinery design are like the syringe, screw extrusion force will drive enormous pressure in small exports, improve production efficiency. When the die is designed to plane how to feed evenly distributed over the entire surface, hanger die design is very important to pay attention to the opportunity to increase the pressure of the gill-type pump stable raw material supply.

4. Cool

In addition to injection mold runner gate perfusion material, there are also design cooling water cooling of the feed. Extrusion molding is against the inner wheel cooling water to achieve cooling effect, except there are air knife, cooling water poured directly on Inflation, and the like hollow blowing cooling.

5. The extension will extend the finished reprocessing enhancement, such as packing tape by varying the rate of front and rear wheel drive that is caused by the effect of the extension, the finished part with extending tensile pull strengthen not easy to tear off, but it very easy to tear the lateral. The molecular weight distribution also extends the Effect of high-speed production when all the pressure has ranged finished product comprises fibers extending vacuum and pressure forming can also be seen as another form of extension.

6. shrink materials have any questions shrinkage, shrinkage stress generated when reason comes from thermal expansion and contraction caused by the crystalline form. Generally easier to overcome thermal expansion and contraction, in the process to extend the cooling time, continuing to do a good job packing, crystalline materials tend to have a greater contraction than the amorphous difference to PP concerned about thousandths Sixteen, but ABS is only about four thousandths, very different in this part of the mold to be overcome, or is often added to reduce shrinkage additive overcome, press out flat LDPE often added to improve the necking problem.

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Injection mold technical requirements

In order to improve the quality of mold quality, minimize mold quality complaints, customer satisfaction to mold, mold manufacturing FAQs summarize, draw conclusions, and the establishment of standards, as required to perform.

Needs to be done between 1 less than 2020 embryos die, a, b board pry the pit; more than 2020 embryos die between the ejector plate template includes all have to do pry the pit.

2. mold guide pins and bushings embryo processing exhaust ducts to prevent the guide pins and bushings strain.

3. The mold may not have sharp corners, need chamfering. Except where specified.

The inner mold and mold parts without consent may not have welding.

5. Mold periphery must be open exhaust ducts in place, the exhaust groove specifications refer to the mold design manual.

6. possible, avoid using grinding machine grinding on the mold, if you must use grinding machining, oil stone province must light (especially sub-surface)

7. The surface treatment of plastic-mold planes must be performed in accordance with the bom table, or other formal notification requirements. Plane of non-rubber processing lines (line cutting, milling machines, cnc gong bed, sparks machine) but also light oil stone province.

8. All material within the mold, the mold base level requirements must be based on purchase orders, or the design review process formally recognized technical requirements. You must provide material proof, if it die, the report must provide a heat treatment. All relevant evidence.

9. mold all around the mold inserts, row position, slant, straight top (push blocks), shovel chicken needs a waist circle pit bit on the bottom or side of the process, and the hardness of the material were carved out.

10. The line position, push block, shovel chicken, jack mouth and other important parts must be easy to wear nitride hardening process.

11. The line position must be located. Positioning methods are slingshot, wave beads, hasco (dme) standard line position clip etc., in accordance with the specific needs of each project requirements. Line position requires layering, wear plate. Layering, wear plate must wear a hard material, we need to add tank.

12. The line position angle pin must be pressed, and not turn loose. Bevel Pillar tail must be processed into hemispherical or truncated conical shape, help ensure normal movement line position. There are two or more than two angle pin, length, size and inclination angle pin must have the same position on the same line.

13. Slant seat must wear a hard material. Slant to processing tank, the lifter seat general use 2510 or cr12 hardened to hrc40-45 degree, because lifter seat by the impact load, it is not too hard otherwise it will break, and positioned at right angles at all corners chamfered c ʱ?? It requires the lifter guide plate (bronze). You may not welding.

14. The flow channel and into the plastic bits need to provincial light # 400-600.

15. thimble, Division tube, shut thimble, lifter and ejector plate to be engraved with the corresponding identification code, easy to install. If the product, thimble location is not level, we need to make tailstocks "d" type or the use of anti-resale key positioning.  

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Injection mold manufacturing characteristics and requirements

Plastic mold production of general machinery products in common, and also that its particularity. Compared with the general machinery manufacturing, mold manufacturing is generally difficult, especially precision molds. As a special technical equipment, mold production and process are the characteristics of the following aspects.

1. Precision mold manufacturing, high quality requirements, not only requires high precision, but also processing good surface quality. In general, working part mold manufacturing tolerances should be controlled within ± 0.011mm, and some even require within micron range, surface defects after tooling requirements are very strict, and the surface of the working portion of the roughness Ra <0.8 um.

2. shape of sophisticated mold part of the work are generally two-dimensional or three-dimensional complex surface (especially mold cavity), rather than the general machining of simple geometric profile.

3. The mold as a single piece, many varieties of each pair of mold can only produce Moi specific shape, size and precision parts. In the manufacturing process as much as possible the use of common tools, common measuring tools and instruments, as much as possible to reduce the number of special tools. In the manufacturing process arrangement requires relatively centralized process to ensure the quality and accuracy mold, simplify management and reduce the process turnaround time.

The high hardness of the material is actually a plastic mold machining tool, its high hardness, usually made of hardened alloy tool steel or carbide and other materials, if manufactured using conventional machining methods, often compare difficult, so mold processing method different from the general machining.

5. Due to the short production cycle and accelerate product replacement market competition becomes more intense, requiring mold production cycles are getting shorter. Mold production management, design and technological work should meet this requirement, to improve the mold design, manufacturing and standardization, in order to shorten the manufacturing cycle.

6. When a complete set of production parts need more deputy mold, a mold before the products manufactured are mutually implicated restrict Yi blank mold, mold parts, and only eventually qualified parts, which was a series of mold considered qualified. In the production and scheduling of the mold must take full account of this characteristic.

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Plastic injection molding solutions to problems

In the injection molding process, mainly due to product defects is

1) molding plastic parts design is not

(2) mold design, manufacturing unreasonable;

Nature (3) of the plastic itself;

4) the inappropriate choice of molding process conditions;

(5) injection molding machine model matching unreasonable. Therefore, to solve the problem of plastic injection molding bad, we can start from the injection machine, molding conditions and mold (including product design), plastics and so on. However, the reasons for seeking to defect from the plastic is very difficult, because the defect molded parts are often made in front of several reasons why the mutual coupling formed by the action (see Table 1), it causes the defect depends on the vast project experience and judgment of the technical staff

Countermeasure

1, the rational design of plastic parts

Design of plastic parts to uniform thickness, it is because the molding cycle cooling time is never a given thickness of plastic parts, if a part of the thick, partially affected by the thickness of the cooling time and extended cycle times, reduce the efficiency of the molded ; Also, if uneven wall thickness, is caused by uneven shrinkage, resulting in reduced pit or internal stress, as well as deformation or cracking. Plastic stripping designed to have a certain slope to ensure the smooth stripping of plastic parts. Because the internal stress tends to be concentrated at the intersection of the surface and the surface, i.e., focused on the corner, in order to reduce distortion in the root fillet can design stress dispersion, while also improving the fluidity of the plastic, but also conducive to the release. Sometimes in order to enhance the plastic parts or to increase the fluidity of plastics, set the ribs, pay attention to the stripping direction to be provided with a reverse slope.

2. Improved mold design

Gate design is an important and complex issue, in the form of a direct gate, side gate, submarine gate, gate and other points. How to choose the actual manufacturing arrangement runner, gate type and position, mostly by the shape of plastic parts, dimensional accuracy and appearance requirements and decisions, while its runner-type system is varied. In order to make the plastic filling process ends at the same time, the gate and the runner must be balanced. In the injection molding process, the injection into the mold cavity of the molten plastic temperature is about 200300 ℃, but when removed from the mold cavity after the plastic parts which cure temperature 60 0C or less, the mold temperature is lowered due to the cooling water through the heat away, so a reasonable cooling system directly affects the dimensional accuracy of plastic parts and mechanical properties. In the actual injection mold exhaust problem must also be considered, if the injection mold cavity gas can not be discharged smoothly, will make products bubble, loose, filling dissatisfaction, welding is not strong, the workpiece surface fat bird, or at the time of the injection due produced by high-temperature gas is compressed so that the bottom parts of the charred charring. Common exhaust many ways, for example using an exhaust vent grooves, with the gap such as exhaust. Set the top of the system should be considered in order to avoid distortion, bleaching, catching phenomenon.

3, adjusting the injection molding process

For the different types and grades of plastics, which drying and molding the melt temperature are clearly defined, and therefore in the development of the molding process, according to the specific requirements of products used in plastics, to determine its drying and heating barrel temperature. Pressure is also forming important process parameters, the pressure into the injection pressure and holding pressure in two stages. Injection pressure is pushing the screw will melt into the mold cavity pressure used, packing pressure is nearing completion filling in, inject the melt is cooled and solidified to complement the products due to volume shrinkage caused by replenishment process of pressure used, in molding process, the right choice injection pressure and holding pressure and injection speed, is the key to the success of the molding process. Currently, most computer-controlled injection molding machines, injection to the decentralized approach.

4, the choice of efficient equipment

Selection of the injection molding machine should consider matching the mold clamping force is necessary to meet the requirements can not be too large, each injection is not less than the plastic parts plus runner condensate material weight. Pay attention to regular maintenance of equipment to ensure the normal operation of the production. IV Conclusion

Since the injection molding is a complex process, a lot of factors affecting the molding products, often a result of improved product defects caused by forming factors, may cause another previously insignificant factors stand out, make the product the emergence of new defects. Thus, in the development and adjustment molding process, not only to build pressure, speed, the right combination of temperature and the right choice for screw speed, injection pressure screw each position, holding pressure. Back pressure and cooling time and other issues should be fully valued. Advanced tooling, efficient equipment and reasonable modern injection molding process is the production of three elements. Therefore, in addition to research as a mold designer and mold structure and processing technology, but also a certain amount of injection molding technology, especially for products in the molding process common defects and solutions should have a full understanding.

more information www.chinamoldmaker.org http://cnmoulding.livejournal.com/23266.html

Plastic Injection product problems and solutions (a)

Overflow edge

  For the overflow edge processing should be mainly focused on improving aspects of mold. And in the molding conditions, we can begin to reduce liquidity. Specifically, the following methods may be used:

1) reduce the injection pressure.

2) reducing the temperature of the resin.

4) The use of high viscosity grades of material.

5) lowering the mold temperature.

6) mold surface grinding overflow edge occurred.

7) The harder the steel mold.

8) increase the clamping force.

9) Adjust the exact molds and other parts of the joint surface.

10) increase in die support columns, in order to increase the rigidity.

11) is determined depending on the material of the exhaust ducts of different sizes.

   

Burn

  According to Burns by different reasons machinery, molds or molding conditions caused by the solution adopted is different.

1) mechanical reasons, e.g., due to an abnormal condition caused by overheating of the barrel, the resin pyrolysis, injected into the product after burn

, Or simply because the material in the nozzle and the screw thread, check valve and other parts of the stagnation caused by the resin, after decomposition of color into the products, with dark brown burn scar in the article. At this time, we should clean up the nozzle, screw and barrel.

2) Cause molds, primarily because due to bad exhaust. Such burns generally occurs in a fixed place, easy to distinguish the first case. Then add exhaust ducts should pay attention to take measures such as anti-blow-down bar.

3) in the molding conditions, when the back pressure above 300MPa, the barrel portion would overheat, causing burns. Screw speed

When too high, it will produce heat, generally in the 40 ~ 90r / min range as well. Did not set in exhaust ducts or exhaust ducts is small, the injection speed too high will cause superheated gas burns.

Warping, deformation

  Injection products, warp, deformation is very difficult problem. Mainly from mold design to address, and to adjust the effect molding conditions is very limited. Warp, causes and solutions of this variation may refer to the following items:

1) residual stresses caused by the molding conditions cause deformation, by reducing injection pressure, improve mold and mold temperature uniformity and increase the resin temperature or the use of annealing method to eliminate stress.

2) the release of stress and deformation caused by bad, it can be solved by increasing the number or area of ​​the push rod, a release gradient methods.

3) As the cooling method is inappropriate, uneven cooling or insufficient cooling time, cooling method and the extension of the adjustable cooling time. For example, you can set up close to the deformation of the cooling circuit in place as possible.

4) For the deformation caused by mold shrinkage, it is necessary to revise the design of the mold. One of the most important to pay attention to the wall thickness is consistent. Sometimes, in the last resort, it had by measuring the deformation of the article, in the opposite direction trimming die, to be corrected. Larger shrinkage resin, a crystalline resin is generally ~ (e.g. polyoxymethylene, nylon, polypropylene, polyethylene and PET resin) than the non-crystalline resin (such as PMMA resin, polyvinyl chloride, polystyrene, ABS resin and AS resin) of deformation. Further, since the glass fiber-reinforced resin having fibers

Bubble

According causes bubbles, solving strategies in the following areas:

1) is larger in wall thickness, the outer surface of the cooling rate faster than the central portion, and therefore, as cooling proceeds, the resin shrinkage side edge of the central portion of the surface of the expansion, the central unit generates less filling. This condition is known vacuum bubbles. Solutions include:

a) according to the thickness, to determine a reasonable gates, runner dimensions. General gate height should be 50% to 60% of the wall thickness.

b) to the gate sealing up, leave some supplementary material injection.

C) injection time should be slightly longer than the gate seal.

d) reducing the injection speed, injection pressure increase,

e) the high melt viscosity grade material.

2) due to the generation of volatile gas bubble caused, the solution are:

a) full pre-drying.

b) reducing the temperature of the resin, to avoid decomposition gas.

3) bubble caused by poor liquidity, can be resolved by increasing the temperature of the mold resin and improve injection speed.

Albino

Whitening phenomenon occurs in the launch of the most important parts of ABS resin article. Stripping ineffective is the main reason. Injection pressure can be reduced, increased stripping slope, increase the number of push rod or area, reducing the surface roughness of the mold and other ways to improve, of course, spray release agent is also a method, but should be careful not to follow the process , such as stamping, painting and other adverse effects

In the process of injection molding, there are still many problems. For example www.injectionmoldchina.com 

http://janelicnmoulding.blogcu.com/plastik-parcalarin-kivrilma/20102371

Injection product problems and solutions (b)

Overflow edge

  For the overflow edge processing should be mainly focused on improving aspects of mold. And in the molding conditions, we can begin to reduce liquidity. Specifically, the following methods may be used:

1) reduce the injection pressure.

2) reducing the temperature of the resin.

4) The use of high viscosity grades of material.

5) lowering the mold temperature.

6) mold surface grinding overflow edge occurred.

7) The harder the steel mold.

8) increase the clamping force.

9) Adjust the exact molds and other parts of the joint surface.

10) increase in die support columns, in order to increase the rigidity.

11) is determined depending on the material of the exhaust ducts of different sizes.

   

Burn

  According to Burns by different reasons machinery, molds or molding conditions caused by the solution adopted is different.

1) mechanical reasons, e.g., due to an abnormal condition caused by overheating of the barrel, the resin pyrolysis, injected into the product after burn

, Or simply because the material in the nozzle and the screw thread, check valve and other parts of the stagnation caused by the resin, after decomposition of color into the products, with dark brown burn scar in the article. At this time, we should clean up the nozzle, screw and barrel.

2) Cause molds, primarily because due to bad exhaust. Such burns generally occurs in a fixed place, easy to distinguish the first case. Then add exhaust ducts should pay attention to take measures such as anti-blow-down bar.

3) in the molding conditions, when the back pressure above 300MPa, the barrel portion would overheat, causing burns. Screw speed

When too high, it will produce heat, generally in the 40 ~ 90r / min range as well. Did not set in exhaust ducts or exhaust ducts is small, the injection speed too high will cause superheated gas burns.

Warping, deformation

  Injection products, warp, deformation is very difficult problem. Mainly from mold design to address, and to adjust the effect molding conditions is very limited. Warp, causes and solutions of this variation may refer to the following items:

1) residual stresses caused by the molding conditions cause deformation, by reducing injection pressure, improve mold and mold temperature uniformity and increase the resin temperature or the use of annealing method to eliminate stress.

2) the release of stress and deformation caused by bad, it can be solved by increasing the number or area of ​​the push rod, a release gradient methods.

3) As the cooling method is inappropriate, uneven cooling or insufficient cooling time, cooling method and the extension of the adjustable cooling time. For example, you can set up close to the deformation of the cooling circuit in place as possible.

4) For the deformation caused by mold shrinkage, it is necessary to revise the design of the mold. One of the most important to pay attention to the wall thickness is consistent. Sometimes, in the last resort, it had by measuring the deformation of the article, in the opposite direction trimming die, to be corrected. Larger shrinkage resin, a crystalline resin is generally ~ (e.g. polyoxymethylene, nylon, polypropylene, polyethylene and PET resin) than the non-crystalline resin (such as PMMA resin, polyvinyl chloride, polystyrene, ABS resin and AS resin) of deformation. Further, since the glass fiber-reinforced resin having fibers

Bubble

According causes bubbles, solving strategies in the following areas:

1) is larger in wall thickness, the outer surface of the cooling rate faster than the central portion, and therefore, as cooling proceeds, the resin shrinkage side edge of the central portion of the surface of the expansion, the central unit generates less filling. This condition is known vacuum bubbles. Solutions include:

a) according to the thickness, to determine a reasonable gates, runner dimensions. General gate height should be 50% to 60% of the wall thickness.

b) to the gate sealing up, leave some supplementary material injection.

C) injection time should be slightly longer than the gate seal.

d) reducing the injection speed, injection pressure increase,

e) the high melt viscosity grade material.

2) due to the generation of volatile gas bubble caused, the solution are:

a) full pre-drying.

b) reducing the temperature of the resin, to avoid decomposition gas.

3) bubble caused by poor liquidity, can be resolved by increasing the temperature of the mold resin and improve injection speed.

Albino

Whitening phenomenon occurs in the launch of the most important parts of ABS resin article. Stripping ineffective is the main reason. Injection pressure can be reduced, increased stripping slope, increase the number of push rod or area, reducing the surface roughness of the mold and other ways to improve, of course, spray release agent is also a method, but should be careful not to follow the process , such as stamping, painting and other adverse effects

In the process of injection molding, there are still many problems. For example

www.plastic-injectionmoulding.com 

https://www.liketly.com/blog/170244/injection-processing-products-crack-cause-and-solution/

Design features injection molded parts during the injection process

During the injection molding process, due to the plastic uneven cooling in the mold cavity and uneven shrinkage and molded parts design unreasonable, likely caused by a variety of defective products:

  

Microprinting, weld mark, porosity, deformation, galling, top injury, flash.

  

To obtain high-quality plastic products, we must fully consider the structure of the product design process, the following main structural features combined analysis of injection molded plastic products avoid injection defects.

  

1 mold parting line direction

Each injection product design at the beginning of the first to determine the direction and the mold parting lines, in order to ensure as much as possible to reduce the pulling mechanism and eliminate the effect of the parting line of appearance.

 1.1 mold after determining the direction, product ribs, snap, projections and other structures designed to be consistent with possible mold direction, in order to avoid reducing core pulling patchwork line, extend die life.

1.2 Example: bumper mold direction is generally the vehicle coordinate χ direction, if a model designed to χ axis direction is inconsistent, it must indicate their angle in the product drawing.

  

1.3 mold direction is determined, choose the appropriate parting lines to improve the appearance and performance. 2 stripping slope

A proper draft is to avoid product nap. Smooth surface stripping slope greater than 0.5 degrees, one degree higher than the surface of fine sticks, sticks rough surface is greater than 1.5 degrees.

2 proper draft is to avoid products top injury.

  

3 Deep cavity design requires less than the slope of the outer surface of the inner surface of the slope, to ensure that when the injection mold core without deviation, to obtain a uniform product thickness, and the opening portion of the product to ensure the strength of the material density.

  

3 Product thickness

  3.1 All kinds of plastic have a certain thickness range, generally 0.5 ~ 4mm, when the thickness of more than 4mm, will cause the cooling time is too long, resulting in microprinting and other issues, should consider changing the product mix.

  

3.2 microprinting surface can cause uneven thickness. 3.3 will cause uneven thickness and weld porosity marks.

4 ribs

4.1 to strengthen the rational use of ribs, increase product rigidity and reduce distortion.

 4.2 stiffener product wall thickness must be less than 1/3, otherwise the surface microprinting.

more information www.chinamoldmaker.org 

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Injection molding design issues should be noted

1. Injection should be consistent with the outer surface smooth Requirements: High visibility area, A level surface, the local tangent continuous. Less visible areas, grade B surface, tangent continuous. Invisible area, grade C surface, continuous position.

2. Injection to smooth the edges, and other pieces of gap should be uniform.

3. Surface do striae member draft angle greater than 5 °. Structural strength, reliable, secure and stable installation.

Surface quality interior trim pieces demanding surface defects are not allowed. Most of the current use of injection molding, compression molding process for forming the inner trim, interior trim to consider outside surface should be in the direction of releasing no "negative" to ensure that in the mold design, mold parting lines are not assigned On the surface of the door trim panel, so as to ensure the surface quality of the outer surface of the door trim board. Determine the draft direction injection molded parts should also consider whether there are avoidable negative angle to reduce costs. After the interior molding surface does not allow flawed, sink marks, so the design should guarantee for the wall thickness, ribs strengthen the rational distribution, rib thickness should be less than 1/2 of the maximum can not be greater than 1 / 1.6.

4. Injection skeleton material thickness is generally 2.5-3 mm,

5. In general, small parts with snap, catches connection, large parts or parts to increase the force and increase the need to strengthen the screw connection

Structure. Snap snap connection should consider the amount of axial rebound 0.5 mm, the amount of compression side pressed into 0.75 mm, snap common vias φ8 (φ6.5) card withhold the end of the large diameter φ9.5 (φ8). Brackets size recommended modifications compensation snaps. Where zero is designed components and peripheral parts in contact with the touch should be zero, and should leave enough local non-contact sufficient space; the supporting surface should be considered when designing plastic parts require a larger plane as the bearing surface, if the Omo as a whole by the bearing surface, in the manufacturing process is not easy to meet the requirements.

6. Aperture shape and position size should be rounded, aperture in line with standardized, serialized.

7. Check the manufacturing process: the appearance of molded parts to be uniform thickness; interior trim is a large thin-walled injection molded parts, requiring the materials

Have better liquidity, along with high precision parts and resistance to UV stability, the general use of modified polypropylene. In the structural design of plastic parts, to avoid excessive use acute and right angles, since stress concentration at sharp corners, easy to crack, the impact strength of the workpiece; in order to avoid stress concentration should be used arc transition, which for mold manufacturing, life is very advantageous. General plastic parts each connection should be 0.5-1mm rounded, and large rounded corners imposed transition, to reduce stress, and to ensure consistent wall thickness. Hole vias should generally be designed to avoid ф5 less blind holes. The bottom of the blind hole should be designed hemispherical or conical surface, in order to facilitate the flow of materials, pore size and depth ratio is generally 1: 2-1: 3. The length of the larger parts should minimize the length direction on both sides of the mold slide stroke. Pulling the slider injection should be considered within the smallest space. Plastics welding process should also consider whether it is reasonable. Rib design is reasonable. Plastics welding process is reasonable

8. Structural strength analysis: the force components higher strength material should be used, the part in the force area should consider reinforcing structure,

CAE strength analysis carried out if necessary. In large part locally 160 × 160 range without additional support should be considered when the support structure, or foam support blocks. The rim flange parts generally should be designed, firstly, to increase strength, the second is to avoid the flash. Flanging should be added to the appropriate stripping slope.

9. Motion check: moving parts must be checked for motion to prevent interference and determined movement parting gap.

10. Analysis of the final assembly process must carry out parts assembly process analysis, analysis of parts are smooth installation and removal, mainly to have a removal tool installation space and parts activities smooth place. Parts should normally positioning guide structure.

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