反向旋转型双螺杆挤压机及传动系统的设计20141024开题报告

编号无锡太湖学院毕业设计（论文）相关资料题目： 反向旋转型双螺杆挤压机 及传动系统设计 信机 系 机械工程及自动化专业学 号： 0923184学生姓名： 徐志强 指导教师： 戴宁 （职称：副教授） （职称： ）2013年5月25日目 录一、毕业设计（论文）开题报告二、毕业设计（论文）外文资料翻译及原文三、学生“毕业论文（论文）计划、进度、检查及落实表”四、实习鉴定表无锡太湖学院毕业设计（论文）开题报告题目： 反向旋转型双螺杆挤压机 及传动系统的设计 信机 系 机械工程及自动化 专业学 号： 0923184 学生姓名： 徐志强 指导教师： 戴宁 （职称：副教授 ） （职称： ）2012年11月25日 课题来源反向旋转型双螺杆挤压机及传动系统设计科学依据（包括课题的科学意义；国内外研究概况、水平和发展趋势；应用前景等）（1）课题科学意义双螺杆挤出机是为解决单螺杆挤出机的局限性而发展起来的。与单螺杆挤出机相比，双螺杆挤出机更容易加入带状料，分料及玻璃纤维等物料；物料在机筒内停留时间短；塑化混合效果优良，双螺杆挤出机在我国的应用非常普遍。因此对双螺杆挤出机的进一步研究对我国的经济发展有着极其重要的意义。（2）课题研究状况及其发展前景国内发展：从主机及其塑料制品区分，中国可以制造的挤出机包括单螺杆挤出机，适合于加工各种材料及各种结构的板、片、膜、丝、棒等产品；平行异向旋转双螺杆挤出机和锥形异向旋转双螺杆挤出机，适于加工温度敏感性材料，如PVC板、管、异型材等；平行同向旋转双螺杆挤出机，适于原料共混、填充、脱挥、改性、造料，增加一定装置如熔体泵，可用于直接成型；适于高填充料生产的磨盘挤出机、往复螺杆挤出机等。 在我国的塑料加工中，几乎一半的塑料都是由挤出成型来完成的。在常规但螺旋挤出机组的性能方面，我国已能生产螺杆直径为12-250的多种规格，门类齐全的挤出机组长径比大多为2530。在特种挤出机的研究领域，经我国广大科技工作者的努力已经研制出排气挤出机，电磁动态塑化挤出机，串联式磨盘动态挤出机，等多种型号，目前已进入系列的研发阶段。国际上主要有以下方面：（1）新型挤出混炼技术与设备的开发；（2）大口径管材挤出的导向平行双螺杆机出组，钢塑复合管挤出机组和大型双壁波纹管挤出成型机组的开发研究；（3）符合挤出成型和设备的开发研究；（4）CAD/CAM/CAE技术在塑料工业中的研究；（5）在线检测机自动控制技术应用。可以预测，未来挤出成型技术的发展方向是：高速、高产化；大型化和精密化；实现挤出成型设备的大型化可以降低生产成本。模块化和专业化；模块化生产可以缩短新产品的研发周期，争取更大的市场份额；而专业化生产对保证整期质量、降低成本、加速资金周转都非常有利。智能化和网络化；发达国家的挤出机已普遍采用现代电子和计算机控制技术，这对保证工艺条件的稳定、提高产品的精度都极为有利。高效、多功能化；塑料挤出机的高效主要体现在高产出、低能耗、低制造成本方面。研究内容 熟悉反向旋转型双螺杆挤压机的工作原理。 设计反向旋转型双螺杆挤压机。 掌握反向旋转型双螺杆挤压机传动箱的设计方法。 绘制挤压机及传动系统总装图、部件图和零件图。拟采取的研究方法、技术路线、实验方案及可行性分析研究方法：一是沿用塑料机械的挤压理论，采用移植、修改等方法，设计出挤压机。二是以较为成熟的挤压机原型，应用相似理论，按比例放大或缩小，设计、制造出可供实用的挤压机。三是计算机辅助设计，参照上面的方法，利用计算机进行数据处理，可用AUTO-CAD来绘制部件工作图，也可以利用计算物理学建立挤压机的数学模型，调整不同工况参数，进行模拟和优化。研究计划2012年11月12日-2012年12月31日：按照任务书要求查阅论文相关参考资料，完成毕业设计开题报告书。2013年1月1日-2013年1月27日：学习并翻译一篇与毕业设计相关的英文材料。2013年1月28日-2013年3月3日：毕业实习。2013年3月4日-2013年3月31日：反向旋转型双螺杆挤压机总体结构设计。2013年4月1日-2013年4月14日：传动箱设计。2013年4月15日-2013年4月28日：零件图及三维画图设计。2013年4月29日-2013年5月20日：毕业论文撰写和修改工作。特色或创新之处反向旋转型双螺杆挤压机的传动系统结构紧凑、动力分配合理，满足工作要求。已具备的条件和尚需解决的问题设计方案思路已经非常明确，已经具备使用AUTO_CAD的能力和机械设计方面的知识。 使用AUTO-CAD的能力尚需加强，结构设计能力尚需加强。指导教师意见 指导教师签名：年 月 日教研室（学科组、研究所）意见 教研室主任签名： 年 月 日系意见 主管领导签名： 年 月 日英文原文A simplified twin screw co-rotating food extruder: design, fabrication and testingS.A.M.A.N.S. Senanayake a, B. Clarke b,* Division of Agricultural and Plantation Engineering, The Open University of Sri Lanka, Nawala, Nugegoda, Sri LankaDepartment of Postharvest Technology, School of Agriculture, Food and Environment, SilsoeCollage, Cranfield University, Silsoe, Bedfordshire MK45 4DT,UKReceived 6 July 1998; accepted 10 February 1999AbstractA simplified co-rotating twin screw food extruder was designed, fabricated and tested in England, followed by extensive testing in Sri Lanka. It was built as a model to meet the specific product and financial constraints of less developed countries and was expected to be used in those countries to widen the production capabilities of extruded foods. The machine had an estimated delivery of 10 kg/h and was made mainly with mild steel. Two types of screw were made, one with a constant pitch of 14 mm and the other with varying pitch in segments of 14, 12 and 10 mm. The machine was powered by a 2.2 kW electric motor with electronic speed control .The machine also had electrical heating with a temperature controller and a pressure sensing device. The cost of fabrication of themachine was estimated at 2000 with most of the parts built in a fairly simple workshop. A mixture of rice and dried banana was successfully extruded as a potential snack food and on the basis of maximum expansion the best results was obtained from a barrel temperature of 120C, screw speed 125 rpm, feed moisture 15% and with a die orifice size of 3 mm. When the alternative compress ion screw was tested very similar results were achieved with no significant improvement in product expansion. 1999 Elsevier Science Ltd. All rights reserved.Keywords: Twin screw extruder; Design; Low cost; Snack food; Continuous cooker; Local construction; Cereal mixturesNomenclaturea Die diameter (mm)B Channel width (mm)C Screw circumference (mm)d Screw core diameterD Outer diameter of screws (mm)H Flight depth (mm)M Moisture content (% wet basis)n Number of fight turnsN Speed angular (rev/min)p Pitch (mm)Q Delivery rate (mm3/min)S Total helical length of screws (mm)t Temperature ()T Residence time (min)a Overlap angle of screw fights (degrees)d Calender gap (mm)e Side clearance (mm)q Product density (g/mm3 )/ Helix angle (degrees)* Corresponding author. Fax: +01525-863277; e-mail: b.clarkecran-eld.ac.uk0260-8774/99/$ see front matter1999 Elsevier Science Ltd. All rights reserved.PII: S 0 2 6 0 - 8 7 7 4 ( 9 9 ) 0 0 0 4 9 71. IntroductionExtrusion cooking is finding ever increasing applications in the food process industry. Apart from providing a means of manufacturing new products, it has successfully revolution is many conventional manufacturing processes (Harlow, 1985, Frame, 1994). Today, extruders come in a wide variety of sizes, shapes and method of operation. There are three types of food extruder found in industry: hydraulic ram, roller and screw type extruders (Frame, 1994). The screw extruders are very different to the other two having special features such as continuous processing and mixing ability. Single and twin screw types are both widely used in the food process industry. Unfortunately, most of the food extruders available in the market are either so costly that less developed countries cannot afford to buy them except by some form of assistance or outside investment or else are not appropriate for the wide variety of materials that need to be processed. As a result the growth of extrusion technology of food into these countries has been hindered despite its many advantages. Fig. 2. Plan drawing of the twin screw extruder with drive system. 1-V belt pulley, 2-gear box, 3-food seal, 4-ange clamp bolt, 5-die plate, 6-die, 7-two segments of the extruder chamber, 8-extruder screw.were made so that they could be externally screwed tothe die plate.2.5. Drive systemThe machine was driven by an electric motor of 2.2kW using a twin belt drive between the motor and a gearbox shown in Fig. 2. The speed reduction in the box was2.08 while an electronic speed controller was used to control the speed continuously over the range required.Fig. 3. Front portion of barrel showing provision for heaters, temperatureand pressure sensors. 1-slots for heaters, 2-end anges, 3-side flanges to barrel, 4-hole for pressure sensor, 5-twin holes to form the barrel.2.5.1. Motor powerIn twin screw extruders the motor power is utilisedmainly to compress and shear the food dough that squeezes through various gaps in the intermeshingscrews and the gap between the screws and the barrel.When dealing with a wide range of foods under dierentprocess conditions the shear resistance can vary widelybecause of changes in the rheological behaviour whichwould prevent accurate estimate of the motor power.Owing to the unknown character therefore of the novelmaterials a motor power was selected based on that usedfor similar materials in similar sized extruders with asafety margin and from exploratory trials in the Brabenderextruder. Rossen and Miller (1973) give a rangeof specic energy consumption gures for di.erent extruderswhich ranged from 0.02 to 0.10 kWh/kg. At 10kg/h throughput this gave a maximum power requirementof 1 kW while the Brabender trials tended to indicatea power requirement of about half of this value.The 2.2 kW, 3 phase AC motor used was amply capableof supplying this power plus all other drive friction losses.2.5.2. Gear boxIn the co-rotating extruder the two screw shafts are driven at the same speed in the same direction. The main problem is that they are very close together. The gearbox was designed to drive two pinions, coupled to the shafts by shear pins, by using a gear wheel of more than double the width of the pinions. In this way the two pinions could t side by side driven simultaneously and maximise their diameter space as shown in Fig. 2. Lubricated phosphor bronze thrust bearings were used to resist the axial load generated by the material along the shaft.2.6. Heating and temperature controlHeating of the barrel to give necessary thermal input for cooking the food was done by two sets of cartridge heaters having capacities of 800 and 1200 W. The heaters were positioned in the grooves made on the top and bottom of the barrel towards the die end as shown in Fig. 3. A single temperature controller was set up together with a thermocouple to sense the temperature inside the barrel very close to die plate. Owing to the shortness of the barrel only one thermocouple was considered necessary. In an early design heaters were also used near to the feed hopper but were not used as they tended to cause premature gelatinization of the starch and blockage of the feed.2.7. Pressure sensorPressure measurements are not so important in the commercial production processes as it cannot be directly controlled to monitor the product characteristics. Neither was such a device needed as a safety measure as this was covered by an overload cut out on the electrical supply. However, in experimental work the measurement of pressure is useful to ascertain the relationship between the pressure and the other controllable parameters such as die size, temperature, moisture content and speed. In this study, a device was built using strain gauges mounted on a small cantilever beam in order to measure the pressure inside the extruder barrel (Fig. 4). A four arm strain gauge bridge was fixed at the point of maximum bending moment. The pressure was tapped from a small hole made in the die end of the barrel in which a plunger, sealed by an O-ring, actuated the cantilever beam to transmit the pressure force. The strain in the beam was detected as a voltage difference. This feature could have been used as an automatic safety cut-out but reliance was placed instead on belt slip in the initial drive stage and the motor itself had an overheating cut-out.Fig. 4. Position of pressure and temperature sensors on the extruder barrel. 1-location of strain gauges on the pressure sensor, 2-cantilever support to plunger, 3-temperature sensor.3. Testing and evaluationA range of rice and banana mixtures were selected as being both novel yet having high potential as processed foods in Sri Lanka. These materials are cheap and common crops in most developing countries and represent an opportunity to produce an attractive, nutritious and tasty snack food. This would provide labour, utilisation of excess perishable fruits in season and a means of storing them for at least one year in appropriate packages. The main product qualities were assessed as part of the same programme and shown to be satisfactory by Gamlath (1995). The rice was prepared in the form of grits (800 lm) and the banana was dried and milled to a similar sized powder which was mixed and flood fed from the feed hopper. Extrusion trials were carried out as given below. Sixteen combinations ofvariable levels were studied in two sets of experiments. In both sets the throughput was measured when the flow became stable.Initial trials indicated no significant difference in performance due to the variable pitch screws as a means of compressing the feed so all subsequent trials and the results quoted in this paper are for the fixed pitch screws. The extrudate diameter was measured using a vernier calliper immediately after extrusion and before any further drying took place which could cause some further reduction in ratio but not to a.ect the general result. All tests were replicated three times making 48 individual trials carried out in a fully randomised formatExperiment 1Fixed settings:Speed (N) 125 rev/minDie size (a) 5 mm diameterVariables:Barrel temperature (t) two levels (100C and 120C)Feed moisture content (M) four levels (15%, 20%,25%, 30%)Experiment 2. This experiment was carried out using fixed settings of barrel temperature and the feed moisture determined in experiment 1 on the basis that maximum product expansion represented the best quality.Fixed settings:Barrel temperature (t).120CFeed moisture content (M).15%3. Testing and evaluationA range of rice and banana mixtures were selected as being both novel yet having high potential as processed foods in Sri Lanka. These materials are cheap and common crops in most developing countries and represent an opportunity to produce an attractive, nutritious and tasty snack food. This would provide labour, utilisation of excess perishable fruits in season and a means of storing them for at least one year in appropriate packages. The main product qualities were assessed as part of the same programme and shown to be satisfactory by Gamlath (1995). The rice was prepared in the form of grits (800 lm) and the banana was dried and milled to a similar sized powder which was mixed and flood fed from the feed hopper. Extrusion trials were carried out as given below. Sixteen combinations ofvariable levels were studied in two sets of experiments. In both sets the throughput was measured when the flow became stable.Initial trials indicated no significant difference in performance due to the variable pitch screws as a means of compressing the feed so all subsequent trials and the results quoted in this paper are for the fixed pitch screws. The extrudate diameter was measured using a vernier calliper immediately after extrusion and before any further drying took place which could cause some further reduction in ratio but not to a.ect the general result. All tests were replicated three times making 48 individual trials carried out in a fully randomised formatExperiment 1Fixed settings:Speed (N) 125 rev/minDie size (a) 5 mm diameterVariables:Barrel temperature (t) two levels (100C and 120C)Feed moisture content (M) four levels (15%, 20%,25%, 30%)Experiment 2. This experiment was carried out using fixed settings of barrel temperature and the feed moisture determined in experiment 1 on the basis that maximum product expansion represented the best quality.Fixed settings:Barrel temperature (t).120CFeed moisture content (M).15%Table 1Results of Experiment 1 (Die orifice diameter=5 mm, screw speed=125 rpm)Temperature (C) Feed moisture (%) Throughput (g/s) Expansion ratio Pressure (MN/m2)100 15 3.76 1.01 2.97100 20 2.56 1.00 2.38100 25 2.04 1.00 1.83100 30 1.25 1.00 1.38120 15 2.16 1.06 2.91120 20 2.00 1.05 2.07120 25 1.18 1.01 1.59120 30 1.02 1.00 1.38Variables:Die orifice diameter (a) two levels (3, 4 mm)Speed (N) four levels (100, 125, 150, 175 rev/min)4. Results and discussion4.1. Machine performanceGenerally the extruder performed very satisfactorily.The extrudates produced by the machine were fairly well expanded. During extrusion operations it did not become necessary to dismantle the barrel lengthways by splitting into two halves as it never seized up. In order to clean the screw and barrel the latter barrel was very easily pulled o. from the screws within a few minutes after extrusion. This was in part due to a shorter than usual barrel length. This suggests that the horizontal splitting of the barrel was not essential which would make the machining process of the barrel far easier. No serious difficulties were encountered as far as the operation of the machine is concerned, except initial feedingproblems due to a temperature rise close to the feed hopper. This happened because some heaters were installed a little too close to the feed point so these were later removed and the difficulties were overcome as mentioned earlier. Many extruders have cooling facilities in this region but these were not found to be necessary. Those heaters further from the feed point and close to the die end proved to be sufficient to gelatinize the rice grits. The extrudate was observed to change from a powder at feed to a continuous, expanded extrudate at exit although quantitative assessments of the degree of gelatinization were not carried out.4.2. Extruder settings and product characteristicsIt can be seen from Table 1 and Fig. 5 that the throughput dropped with each increase of feed moisture content at both the barrel temperatures used. When the feed moisture was increased from 15% to 30%, the throughput was reduced by 66.8% and 52.7% at 100 and 120barrel temperatures, respectively. This effect was probably caused by an increase in backflow allowed by the reduced viscosity which the increase in moisture produced. Another important observation made was the variation of product expansion with the pressure and feed moisture content. The expansion was found to