关 键 词：

防护罩 注射 模具设计 塑料 注塑 CAD SW 三维

资源描述：

防护罩注射模具设计-抽芯塑料注塑模含9张CAD及SW三维,防护罩,注射,模具设计,塑料,注塑,CAD,SW,三维

内容简介：

The rmo plasticThe plastic is take the relative molecular mass high synthetic resin as the principal constituent.And joins other chemical additives, may plastifies the formation under certain temperature and the pressure the high polymer composition material.The plastic take synthetic resin as the basic raw material, and regards needs to join the suitable chemical additive.The resin is when being heated softens, has the flowing tendency polymer under the exogenic process.It is in the plastic coheres the function ingredient.The resin has mainly decided the plastic type and the basic decision plastic main performanceIn order to change the chemical additive which the plastic the performance joins to have the padding, the plasticizer and the stabilizer.The plastic variety is many, the performance is also various.Induces, the plastic principal characteristic is as follows: 1. quality light plastic density in the 0.92.3g/cm3 scope, approximately is generally the aluminum 1/2, copper 1/6.2. specific tenacities and are high the plastic the rigidity the intensity and the rigidity although was inferior the metal is better than, but the plastic density is small, therefore its specific tenacity and is quite higher than the rigidity.If the glass fiber reinforced plastics and the carbon fiber reinforced plastics specific tenacity and is all better than the rigidity the steel products, this pseudoplastic commonly used in manufacture satellite, on rocket and missile components.3. chemical stability performance good plastic para acid, chemistry medicines and so on alkali have the good corrosion resistance ability.Therefore, obtains the widespread application in the chemical equipment as well as the manufactured item for daily use.The commonly used anti-corrosive plastic is the rigid polyvinyl chloride, it may process the pipeline, in the vessel and the chemical equipment spare part.4. electric insulation performance good plastic has the superior electric insulation performance and bears the arc characteristic, therefore widely applies in the electrical machinery, in the electric appliance and the electronics industry makes the constructional detail and the insulation material.5. wear-resisting and the anti-attritionperformance good plastic friction coefficient is small, wear resistant, may take the anti-attritionmaterial, like uses for to make the bearing, components and so on gear.6. noise eliminations and attract shake the performance to be good.The plastic makes the transmission friction components, the noise is small, attracts the knocking to be good.The thermoplastic is refers in the specific temperature range internal energy heats up and the hardening by cooling plastic repeatedly.For example: Polyethylene, polypropylene, polystyrene and so on.The thermoplastic craft characteristic has following several kinds:One. ContractilityThe thermoplastic formation contraction form and the thermosetting plastics are similar.The influence thermoplastic formation contraction primary factor has following several aspects:(1) plastic variety: In because the thermoplastic formation process has the change in volume which the crystallization causes, internal stress, models in the residual stress to be big, molecular orientation strong and so on factors, therefore compares the shrinkage with the thermosetting plastics to be big, the directivity is obvious.Moreover, after the drawing of patterns the contraction and post-processing contraction specific heat soundness plastic is also big.(2) models a characteristic: When models a formation, the melt material and the die space surface contact outer layer cools immediately, forms the low density the solid state outer covering.Because the plastic thermal conductivity is bad, causes to model inner layer slow cooling to form contracts the great high density solid state level.Therefore, models a wall to be thicker contracts in a big way.(3) runner form and size: These factor direct influence material flows the direction, the density distribution, guarantees the pressure to make up shrinks the function and the formation time.Uses the direct runner, the runner section big when contracts slightly, but the directivity is obvious.(4) formation condition: The mold temperature, the injection pressure, guarantees presses formation conditions and so on the time to have the direct influence to the plastic product contraction, the mold temperature is high, the melt material cools slowly, the density is high, contracts in a big way, especially to crystallization material, because its change in volume is big, the drum contraction is bigger.The mold distributes whether even also directly affects the plastic product various partial contraction quantity size and the directivity.The injection pressure is high, the melt material viscosity is bad, the level the shear stress is small, after the drawing of patterns the rebound resilience is big, the contraction reduces.Guarantees presses the time to contract also influential.Guarantees presses the time long to contract slightly, but the directivity is obvious.Designs when the mold, should act according to each kind of plastic the contraction scope, models a wall thickness, the shape, the feed head form size, according to the experience determined models various part of shrinkage, again calculates the mold die space size.Models to the high accuracy, designs when the mold should leave leeway repairs the mold leeway, revises the mold gradually after the experimental mold, achieved models a size, the precision request and the improvement formation condition.Two. Fluidity1. fluid plastic fluid size, may from the plastic relative molecular mass, the fusing index, the Archimedes spiral line length, the apparent viscosity and the flowing compared to and so on carries on the analysis.The relative molecular mass is small, the fusing index is high, the spiral line length is long, the apparent viscosity is small, flows compared to the big plastic, then the fluidity is good.According to the mold design request, may divide into the commonly used plastic fluidity three kinds:(1) fluidity is good: Has the nylon, the polyethylene, the polystyrene, the polypropylene, the acetyl cellulose. (2) fluidity medium: Has the modified polystyrene, plexiglass, metaformaldehyde.(3) fluidity is bad: Has gathers the carbonic ether, the polyphenylene oxide, gathers the sulphone, the fluorine plastic.2. influence fluid primary factor（1) temperature: Expects warm high then the plastic fluidity increases, but expects the warm convection mobile influence to regard the different plastic different, some influences are big, some influences are small.Therefore in formation time may control the fluidity through the attemperation.（2) pressure: The injection pressure increases fuses the plastic to be big the shear action, its fluidity increases along with it.The polyethylene, the metaformaldehyde extremely is specially sensitive to the pressure response.Therefore time formation may control the fluidity through the adjustment injection pressure.(3) mold structure: The mold casting system form, the size and the arrangement, the cooling system design rationality, melt material flowing factors and so on resistance all directly affect the melt material in die space actual fluidity. Every urges the melt material reduced temperature, the increase flow resistance factor, all can cause the fluidity to reduce.Designs when the mold should act according to uses the plastic the fluidity, selects the reasonable mold structure.Three. CrystallinityThermoplastic according to its condensation when whether there is appears the crystallization phenomenon to be possible to divide into the crystalline plastic and the amorphic substance plastic two big kinds. The plastic crystallization phenomenon is refers to the plastic from the fusing condition to in the condensation process, but the member arranges into the regular model gradually by the out-of-order free motion condition the tendency one kind of phenomenon. In general, the crystalline plastic is not opaque and translucent, the amorphic substance plastic is transparent.But also has the exceptional case, ABS is the amorphic substance plastic, but is not actually transparent.Should pay attention to following several points regarding the crystalline plastic in the mold design and the choice injection machine-hour: (1)Expects the warm rise the quantity of heat which needs to the formation temperature to be many, must select the plastified ability big equipment. (2)When condensation emits the quantity of heat to be big, the mold must cool fully.(3)After models a formation to contract in a big way, easy to have the shrink hole, the blowhole.(4)Models a wall to be thin, cools quickly, the crystallinity is low, contracts slightly.Models a wall thickness, cools slowly, the crystallinity contracts high in a big way, the physical performance is good.Therefore, should request to the crystalline plastic according to the plastic to control the pattern making to heat. (5)The plastic aeolotropy is obvious, the internal stress is big, after the drawing of patterns models easily to have the distortion warp.(6)The plastic crystallization melting point scope is narrow, easy to occur has not melted the powder to pour into the mold or the jamming feed head. Four. The heat-sensitivity and Shui Minxing the heat-sensitivity is refers to certain plastics to be sensitive to the heat, warm high and in the being heated time long situation can have the color deterioration in the material, falls gathers, decomposition characteristic.Has this kind of characteristic plastic to be called the heat-sensitivity plastic. For example: Metaformaldehyde and so on.In order to prevent the heat-sensitivity plastic appears the color deterioration in the formation process, the decomposition phenomenon, on the one hand may join the heat-stable medicinal preparation in the plastic, on the other hand elected with the screw rod type injection machine, correctly controls the formation temperature and the formation cycle, simultaneously should eliminate the decomposition product promptly, takes the anticorrosion measure to the mold and the equipment. Shui Minxing refers to certain plastics even if only includes the few moisture contents, but in the high temperature, under the high pressure also can have the decomposition characteristic.Must preheat dryly to this pseudoplastic. Five. The stress dehiscence and fusing bursts some plastic counter stress to be sensitive, when formation easy to have the internal stress also the nature crisp easy crack, models can occur under the exogenic process or under the solvent function wipes a row phenomenon.Therefore, besides joins the additive in raw material to enhance the crack resistance, should pay attention dryly to raw material, simultaneously selects the reasonable formation condition and causes to model the shape structure to be as far as possible reasonable. Designs when the mold should increase the drawing of patterns ascent, selects the reasonable feed head and goes against the organization.When formation should adjust the material suitably warm, mold warm, the injection pressure and the cooling time, avoid modelling as far as possible in cold shortness situation the drawing of patterns.After models a formation to have to carry on the post-processing to enhance the crack resistance, eliminates the internal stress. When fuses certainly the index the polymer melt, when constant temperature through spray nozzle, after its speed of flow surpasses certain value, squeezes out the bath surface has the obvious crosswise crack to be called the fusing breakage.Has fusing to burst can affect models a outward appearance and the performance, therefore if choice fusing index high polymer, designs when the mold should increase the spray nozzle, the flow channel and the runner section, reduces the injection speed and enhances the material to heat. Six. The thermal properties and cooling rate each kind of thermoplastic has the different ratio heat capacity, the heat conductivity, thermal properties and so on thermal deformation temperature.Plastic is higher than which the heat capacity when plasticizing the caloric requirement is bigger than, uses the plastified ability big injection machine elected.The thermal deformation temperature high plastic cooling time is short, drawing of patterns morning, after but the drawing of patterns must prevent the cooling strain.The heat conductivity low plastic cooling rate is slow, must cool fully, must strengthen the mold to cool the effect. Each kind of thermoplastic and models a shape according to its variety characteristic, the request maintains the suitable cooling rate.Therefore the mold designs time must according to the formation request establishment heating and the cooling system, controls the mold temperature.The commonly used thermoplastic formation characteristic is as follows: Side1. polyethylene (1) crystalline plastic, the water absorbant small (2) fluidity is extremely good, overflows the value is about 0.02mm, the fluidity is sensitive to the pressure variation.(3) heating time long then easy to have the decomposition4) cooling rate is quick, must cool fully, designs when the mold must suppose the cold slug well and the cooling system.(5) shrinkage is big, the directivity is obvious, easy to distort, the warp, the crystallinity and the mold cooling condition affect in a big way to the shrinkage, should control the pattern making warm (6) suitably with the high-pressured injection, expects warm must be even, the packing speed should be quick, guarantees the pressure to have to be full. (7) uses the direct runner injection not suitably, otherwise can increase the internal stress, causes to contract non-uniform and the directivity is obvious.Should pay attention to the choice runner position.2. polypropylene (1) crystalline plastic, the water absorbability is small, easy to have the decomposition. (2) fluidity is extremely good, overflows the value is about 0.03mm（3) cooling rate is quick, the casting system and the cooling system should radiate slowly.(4) shrinkage is big, easy to have the shrink hole obviously, the distortion, the directivity (5) should pay attention to the control formation temperature, expects warm low then the directivity is obvious, the mold warm is lower than 50, the note leaves models a not gloss, easy to have the fusion not to be good, has the flow marking warm, the mold is higher than easy to have the warp and the distortion.(6) models a wall thickness to have to be even, avoids the gap, the acute angle.3. polystyrene (1) amorphic substance plastic, the water absorbability is small, not easy to decompose, the natural crisp easy crack, the thermal-expansion coefficient to be big, easy to have the internal stress side, (2) fluidity is good, overflows the value is 0.03mm (3) suitably with Gao Liaowen, Gao Muwen, injects the pressure lowly, the extension injection time is advantageous in reduces the internal stress, prevents the shrink hole and the distortion(4) may use each form the runner, the runner with models an attachment point to be supposed to transit smoothly.(5) models a wall thickness to be supposed to be even, has not suitably inlays, the gap, the acute angle, each should transit smoothly.The 4.ABS (1) amorphic substance plastic, water absorbant, wants the thorough drying (2) fluidity medium side, overflows the value is 0.04mm(3) with Gao Liaowen, Gao Muwen, the injection pressure also is suitably high (4) mold casting system to have to be small to the material resistance to flow strength, should pay attention to the choice runner the position and the form, the drawing of patterns ascent for 2 above.5. plexiglass (1) amorphic substance plastic, the water absorbability is big, not easy to decompose, the nature is crisp, skin hardness low(2) fluidity medium side, overflows the value is 0.03mm(3) suitably with the high-pressured injection, and uses high material temperate Gao Muwen, may increase the fluidity, reduces the internal stress, reduces the directivity, the improvement transparency and the intensity.(4) mold casting system wants small to the material resistance to flow strength, the drawing of patterns ascent to be supposed the big 6. nylon (1) crystalline plastic, the water absorbability to be big side, easy to decompose (2) fluidity to be extremely good, overflows the value is the 0.02mm (3) shrinkage is big, the directivity is obvious, easy to have the shrink hole and the distortion(4) should pay attention controls the pattern making warm, otherwise and models a performance to the crystallinity influential (5) to be possible to use each form the runner, the runner with models an attachment point to have the smooth transition, the flow channel and runner section size big good, favors takes shape (6) models a wall thickness not to be suitable too thick, and should be even7. metaformaldehyde (1) crystalline plastic, the water absorbability is small, extremely easy to decompose (2) fluidity medium side, overflows the value is 0.04mm, the fluidity to injects the pressure variation to be extremely sensitive (3) crystallinity to be high, when crystallization the change in volume is big, the shrinkage big (4) mold should heat up, the mold temperature is high, and pays attention controls the pattern making correctly warm, guaranteed models a quality, the spray nozzle should alone heat up, and suitable control spray nozzle temperature.(5) mold casting system must be small to the material resistance to flow strength, the runner section takes big suitably, avoids the dead angle accumulating material 8. to gather the carbonic ether (1) amorphic substance plastic, the water absorbability is small, not easy to decompose side, (2) fluidity is bad, overflows the value is 0.06mm, the fluidity is very sensitive to the temperature change (3) formation shrinkage to be small, models the precision high (4) mold to be supposed to heat up, the mold heats to models the quality influence to be big, should control the pattern making warm (5) fusing temperature to be high correctly, the viscosity is big, the cooling rate is quick, the mold casting system should take thick, short as a principle, and supposes the cold slug well suitably, uses the direct runner(5) fusing temperature is high, the viscosity is big, the cooling rate is quick, the mold casting system should take thick, short as a principle, and supposes the cold slug well suitably, uses the direct runner(6) models a wall not to be suitable too thick, should be even, avoids having the acute angle, the gap 9. gathers the sulphone (1) amorphic substance plastic, the water absorbant big (2) fluidity is bad, is sensitive to the temperature change, the cooling rate is quick(3) formation temperature is high, takes shape suitably with the high pressure.The hypotonia models a surface easy to produce the ripple, the air bubble and the dent, the pressure excessively is high, then the drawing of patterns is difficult.(4) mold must heat up, the mold warm regards wall thickness to decide (5) mold casting system to be supposed to be thick and to be short, radiates slowly, the resistance is small, suitably with goes nonstop to -like the spray nozzle.10. polyphenylene oxide (1) amorphic substance plastic, the water absorbability is small, easy to decompose (2) fluidity to be bad, is sensitive to the temperature change, the coagulation speed is quick, the formation contracts slightly,(3) uses the high-pressured high speed injection suitably, guarantees presses not not suitably with the cooling time has grown.(4) mold must heat up, the mold warm must control, guaranteed models the quality (5) mold feed head taper suitable big and uses pulls the material pole, the casting system must be small to the material resistance to flow strength, uses the direct runner, the flow channel wants stubby 11. to gather the plastic (1) crystalline plastic, the water absorbability is small(2) heat-sensitivity, extremely easy to decompose (3) fluidity to be bad, the fusing temperature is high, the formation temperature range is narrow, wants the high temperature high pressure to take shape (4) mold to be supposed to heat up, and controls the temperature (5) mold casting system to have to be small to the material resistance to flow strength 热塑性塑料塑料是以相对分子质量高的合成树脂为主要成分，并加入其他添加剂，可在一定温度和压力下塑化成型的高分子合成材料。塑料均以合成树脂为基本原料的，并视需要加入适当的添加剂。树脂是在受热时软化，在外力作用下有流动倾向的聚合物。它是塑料中起黏结作用的成分。树脂主要决定了塑料的类型和基本决定塑料的主要性能。为了改变塑料的性能而加入的添加剂有填料，增塑剂和稳定剂。塑料品种繁多，性能也各不相同。归纳起来，塑料的主要特性如下：1质量轻塑料的密度一般在0.92.3g/cm3范围内，约为铝的1/2，铜的1/6。2比强度和比刚度高塑料的强度和刚度虽然不如金属好，但塑料的密度小，所以其比强度和比刚度相当高。如玻璃纤维增强塑料和碳纤维增强塑料的比强度和比刚度都比钢材好，该类塑料常用于制造人造卫星，火箭和导弹上的零件。 3化学稳定性能好塑料对酸，碱等化学药物具有良好的抗腐蚀能力。因此，在化工设备以及日用工业品中得到广泛应用。常用的耐腐蚀塑料是硬质聚氯乙烯，它可以加工成管道，容器和化工设备中的零部件。4电绝缘性能好塑料具有优越的电绝缘性能和耐电弧特性，所以广泛应用于电机，电器和电子工业中做结构零件和绝缘材料。5耐磨和减磨性能好塑料的摩擦系数小，耐磨性强，可以作为减磨材料，如用来制造轴承，齿轮等零件。6消声和吸震性能好。塑料制成的传动摩擦零件，噪声小，吸震性好。热塑性塑料是指在特定温度范围内能反复加热和冷却硬化的塑料。例如：聚乙烯，聚丙烯，聚苯乙烯等。热塑性塑料的工艺特性有以下几种：一收缩性热塑性塑料成型收缩的形式与热固性塑料类似。影响热塑性塑料成型收缩的主要因素有以下几个方面：（1）塑料品种：热塑性塑料成型过程中由于存在结晶化引起的体积变化，内应力强，塑件内的残余应力大，分子取向性强等因素，因此与热固性塑料相比收缩率较大，方向性明显。另外，脱模后收缩和后处理收缩也比热固性塑料大。（2）塑件特性：塑件成型时，熔料与型腔表面接触外层立即冷却，形成低密度的固态外壳。由于塑料导热性差，使塑件内层缓慢冷却而形成收缩大的高密度固态层。因此，塑件壁越厚则收缩越大。（3）浇口形式和尺寸：这些因素直接影响料流方向，密度分布，保压补缩作用及成型时间。采用直接浇口，浇口截面大时收缩小，但方向性明显。（4）成型条件：模具温度，注射压力，保压时间等成型条件对塑料制品收缩均有直接影响，模具温度高，熔料冷却慢，密度高，收缩大，尤其对结晶料，因其体积变化大，鼓收缩更大。模具分布是否均匀亦直接影响到塑料制品各部分收缩量的大小和方向性。注射压力高，熔料黏度差，层间剪切应力小，脱模后弹性回跳大，收缩减小。保压时间对收缩亦有影响。保压时间长则收缩小，但方向性明显。在模具设计时，应根据各种塑料的收缩范围，塑件壁厚，形状，进料口形式尺寸，按经验确定塑件各部分的收缩率，再计算模具型腔尺寸。对高精度塑件，在模具设计时应留有修模余地，通过试模后逐步修正模具，以达到塑件尺寸，精度要求及改善成型条件。二流动性1流动性 塑料流动性的大小，可从塑料的相对分子质量，熔融指数，阿基米德螺旋线长度，表观黏度及流动比等进行分析。相对分子质量小，熔融指数高，螺旋线长度长，表观黏度小，流动比大的塑料，则流动性好。按模具设计要求，可将常用塑料的流动性分为三类：（1）流动性好：有尼龙，聚乙烯，聚苯乙烯，聚丙烯，醋酸纤维素。（2）流动性中等：有改性聚苯乙烯，有机玻璃，聚甲醛。（3）流动性差：有聚碳酸酯，聚苯醚，聚砜，氟塑料。2影响流动性的主要因素（1）温度：料温高则塑料流动性增大，料温对流动性的影响视不同塑料而不同的，有的影响大，有的影响小，。所以在成型时可通过调节温度来控制流动性。（2）压力：注射压力增大则熔融塑料受剪切作用大，其流动性随之增大。特别是聚乙烯，聚甲醛对压力的反应十分敏感。所以成型时可通过调节注射压力来控制流动性。（3）模具结构：模具浇注系统的形式，尺寸和布置，冷却系统设计的合理性，熔料流动的阻力等因素都直接影响到熔料在型腔内的实际流动性。凡促使熔料降低温度，增加流动阻力的因素，都会使流动性降低。在模具设计时应根据所用塑料的流动性，选用合理的模具结构。三结晶性热塑性塑料按其冷凝时有无出现结晶现象可划分为结晶性塑料和非结晶性塑料两大类。塑料的结晶现象是指塑料由熔融状态到冷凝的过程中，分子由无次序的自由运动状态而逐渐排列成为正规模型的倾向的一种现象。一般说来，结晶性塑料是不透明的和半透明的，非结晶性塑料是透明的。但也有例外情况，ABS为非结晶性塑料，但却不透明。对于结晶性塑料在模具设计及选择注射机时应注意以下几点：（1） 料温上升到成型温度所需的热量多，要选用塑化能力大的设备。（2） 冷凝时放出热量大，模具要充分冷却。（3） 塑件成型后收缩大，易发生缩孔，气孔。（4） 塑件壁薄，冷却快，结晶度低，收缩小