Brief Discussion on Domestic Flour Milling Equipment

Yu Mengfa (Taizhou Kaidi Chemical Powder Equipment Co., Ltd.)summary: from the design, manufacture, material selection and heat treatment, marketing and after-sales service of powder-making equipment, the current situation of China's powder-making equipment industry, and put forward a good industry construction advice1 foreword
With the development of powder coating industry, China's domestic powder production equipment has been imitation and its improvement, developed into self-design and professional production, powder ingress equipment design and production has made considerable progressAt present, in addition to the early and a few large-scale powder manufacturers, basically in the use of domestic powder ingenumequipment, with a complete set of production capacity of professional manufacturers have nearly 20, equipment sales are also increasing year by yearWith the deepening of China's political and economic reform, the powder industry and its equipment manufacturing industry will achieve greater developmentpowder coating industry is a new industry, for equipment manufacturers, people have come too late to carry out a variety of in-depth research on the single machine has put forward more and more, higher and higher requirementsNow the environmental awareness and product quality awareness, has made the original kind of low requirements, high prices, high profits of the era no longer exist, leaving us with fierce market competitionHowever, at present, this low-cost market competition is not conducive to the development of enterprises themselves, the author with the attitude of discussion with peers, in order to throw bricks and jade way, to talk about some of our views on domestic powder-making equipment2 equipment designthe design of any product can not be separated from the principle, only the selection of reasonable structure and its parameters, to achieve its design principleHowever, the principle of equipment design is varied, such as extruder, originally with a threaded screw in a smooth cylinder rotation to achieve the purpose of mixing, and then there is damping, reciprocating, twin screw, as well as three screw and multi-screw extruder, is the result of different design principles to choose different structuresWhether the superior structure of a certain equipment is closely related to its design parameters, the same-looking twin screws get different mixing effects and proportional productivity if they have different center distancesThe structural parameters of the extruder include the length ratio, speed, partition and its temperature control range, clearance, internal pressure, exhaust, and the time of stay of the material in the engine cylinderWe found through the various models of various manufacturers to find that the determination of equipment parameters is an organic whole, interrelatedFor example, the design temperature value and the match ingestion gap, screw speed, heating and the way of the slug, processing medium type, whether there is internal cooling, and the position and depth of the probe hole, etcrelated to the design of the melting section temperature should make the molten material melting quickly, at least higher than the softening point, if the design temperature is low, indicating that the melting section of the screw lag, meaning that the length of the diameter is smaller; We have done this test on 58 aircraft: at a distance of 100 to 200mm from the feed port, the temperature value of each 30mm displacement changes to 5 to 10 degrees C, so the design must first determine the melting segment temperature and its gradient distribution, and then set the measuring point position, as well as the shape of the screw element and its arrangement When the machine wear is the gap increases, the feeding capacity decreases, the internal pressure also decreases, and the mixing effect becomes worse It is usually used to reduce the temperature setting of the melting segment to increase the internal pressure in relative to the amount of feed At this time, the actual long diameter ratio is smaller, the non-threaded segment in the melting segment highlights the crushing effect of solid crushing, not only increases power consumption, but also accelerates screw wear, so that the whole machine operation in a bad state China's raw materials, technology level, installation conditions are different from foreign countries, which requires us to carry out equipment design according to the actual situation, for foreign prototype is also good, foreign information is also good, to digest and absorb For example, ACM grinding, the entire unit from the structure and its technical point of view has three levels, one is temperature rise, the other is sealed, three is wind transport Conventional mechanical design temperature control in 30 to 40 degrees C is relatively high, and the characteristics of the paint requirements temperature rise can not be greater than 20 degrees C, otherwise it can not guarantee the normal production at 35 to 38 degrees C summer indoor temperature, we do not advocate by the user to add air conditioning or refrigeration equipment to transform contradictions In addition to the particularity of dust sealing, the sealing problem is also limited by temperature rise We have conducted a separate study of the grinding head, the test found that in order to prevent leakage and added oil seal (choose self-sealing ability of high-speed and minimal grinding of fluorine rubber oil seal), in its high-speed operation generated heat is still far greater than the heat generated in the material crushing, and then we use radial maze and other structures, that is, the use of D-level precision bearings to make it normal operation wind transport is the outline of the grinding process, the air volume and air pressure should be reasonably determined, and then the configuration of fan power, the current common use of blower rather than fan In the whole wind delivery process, the resistance coefficient of the pulse dust ingresss is the largest, and with the increase of powder in the filter bag, the blower may be completely trapped and not wind-resistant phenomenon We have done two experiments on this, one is to use a conventional fan by the cyclone separator to pump air flow and then drum into the dust remover, and the other is to design a new fan The former works well, but it is more troublesome to clean the fan regularly, the latter is more effective, not only to increase the yield (the air volume at this time is effective air volume, less affected by external conditions, so relative lygis is greater), but also reduce spevenia 3 equipment manufacturing market demand to determine that the manufacture of powder equipment can not be a large number of, can only be small batches, or even a single set, but its components processing accuracy is particularly high It is difficult to guarantee quality when machining equipment components on conventional equipment China's mechanical processing industry by the planned economic period of large and complete, small and full system of the impact, has not yet formed a pattern of socialized production, even if some enterprises have some higher-grade processing equipment, but also for a variety of reasons can not be effectively used, the author here on the following three aspects of the discussion 3.1 material selection and its heat treatment most manufacturers now use 38CrMoAl as the main material for extruders We know that extruders (especially gears and shafts in the deceleration gear) require a high strength and a thicker, high hard wear layer, while the strength and wear resistance of 38CrMoTi or 30CrMnSi materials are not as high as those of 30CrMnTi or 30CrMnSi, which is lower than the price In contrast, some mechanically sealed hard rings require nitride of rust-proof black metal pieces ACM grinding ring and grinding column in operation to withstand the high impact of powder, for the surface of cold hardening provides the conditions, so we may wish to choose the cold hardening more sensitive materials, thereby reducing the heat treatment process, reduce costs we also found in the survey, the domestic extruder with the same screw spindle hardness difference is larger, hardness difference is generally around 20HB, and some even reached 50HB The cylindrical degree of the screw spindle is generally larger, the greater the hardness difference, the greater its value, which indicates that the rough quality is not qualified At the same time, all these ultra-long shafts are treated in the same way as the general quality parts, using box-type electric furnace heating, quenching and tempering, temperature uneven material selection and heat treatment should be comprehensive consideration of the requirements and technical characteristics of the parts, and if there are substitute materials and their processes, they should also comply with the relevant provisions of the State 3.2 process and tooling due to the equipment conditions of each equipment manufacturer, the level of production technology and the ability of managers, there is no exact same process and tooling, the key is to ensure quality For example, ACM grinding graders have roughing - welding - finishing, but also a whole-type roughing - quality - finishing and other processes In contrast, the latter is excellent, but if the former has a very high level of welder, welding and tire mold, welding can be destressed annealing, as well as balancing treatment, which can also ensure quality The latter's blade processing also has milling pins and wire cutting points The surface roughness of wire cutting is better than milling, and the shape tolerance and surface roughness of the blades are one of the main factors affecting the particle size distribution of powder, so wire cutting is better, but if the milling blades are added to the polishing process, it is possible to be better than wire cutting , such as the process of moving shafts, the first round of design is a joint shaft gear, interference with each other can only use 38CrMoAl nitride parts In fact, the deformation of the workpiece after nitride has been excellent So the second round is designed as a separator, the gear and shaft are processed separately, according to their respective requirements to select materials, determine the process So the shift shaft has 38CrMoAl nitride, 20CrMnTi carburizing quenching, 42CrMo nitride and 30CrMnSi or 30CrMnTi carburizing and quenching, and we found that the shaft block of the carburizing parts is The ring groove has the fracture phenomenon, the reason for the analysis is that the process arrangement is not appropriate: the ring groove should be cut out after carburizing, the tail end thread should also be processed after carburizing, otherwise the groove and thread are in the carburecity of the volume expansion, quenching when a lot of stress, prompting the ring groove to break In addition, nitride parts also have stress concentration phenomenon, but the degree is much lighter, nitrogen after sharp edges are particularly fragile, a little impact on the slag, so the thread edited parts, small size flower keys, etc should be isolated from nitride , such as grinding cover, almost all manufacturers are using castings, processing accuracy by the car workers to ensure that its quality is not easy to stabilize, human factors more We used to use shallow pull deep parts, tire mold welded into an internal cooling cover, not only to ensure the final accuracy, but also improve the structural design Whether there is workassembly in the welding of the guide leaf and reflux ring, the quality of artificial arc welding, how the welding deformation control measures are controlled, whether there is de-stress annealing before finishing, etc., all affect the accuracy of these workpieces, and it is these workpieces that determine the performance of the grinding in short, a good design must be reliable process and workwear to ensure, and a good process and workwear, can only be used for good design, otherwise it is only a waste 3.3 assembly because of the high technical content of powder-making equipment, there are many manufacturing links must be carried out in the assembly, otherwise it will greatly increase the cost At the same time, because some parts of the processing accuracy, difficult, must use a combination of machining methods, so the assembly not only in the final, but also in the assembly or component processing has occurred in the design of extruder, in order to improve the performance of equipment, it is necessary to improve the overlap of the screw, which reduces the center distance of the gear In order to ensure gear strength, the need to use high-grade materials and increase the tooth width coefficient In the extruder transfer box parts, almost all of the domestic procurement (by batch restrictions) of the best materials, so the tooth width coefficient is mostly more than the recommended value In order to ensure the carrying capacity of the gears, we must adopt measures such as repair and preparation, which increases the technical content of assembly in the screw design, in order to improve the overall accuracy of the screw, design into one-style best, which in the processing of certainly increased the difficulty, in the assembly also increased the difficulty, because the combination of thread and mixed parts, and the existence of its phase deviation, must be in the assembly through research to ensure in short, the processing accuracy of parts is higher, and in fact, the key processing rate of each manufacturer is relatively low, must be achieved through secondary processing, especially the shape tolerance The secondary processing of powder-making equipment is usually connected with assembly, so the assembly of powder-making equipment is different from the general, specialized production has become imperative 4 marketing and user service in the competition of powder-making equipment, marketing and user services bear the brunt, the factories attach great importance to the construction of marketing team, network marketing personnel, but also pay attention to user services, which is in line with the law of market economy we are here to raise a deeper problem, that is, the extension of user services, how to do a good job of old enterprise skilled equipment technology transformation, this is actually a forgotten corner, the reasons are as follows: First, the old equipment old enterprises are mostly national or large collective nature; In this regard, we have made more attempts, one is the newer existing model of product equipment failure, especially the damage caused by operational failure to carry out repair business, and the other is the same model of technical transformation, such as the early twin screw, long diameter ratio of only 7 to 13, we replace the screw screw, and some damaged parts to repair, even if it is not the factory's products also carry out repair business in short, the development of domestic powder-making equipment is rapid, basic health, especially with the expansion of the powder market, the equipment variety and performance requirements will be more and more, higher and higher In order to ensure the development of the powder coating industry, equipment manufacturing industry in addition to competition, but also should strengthen cooperation to protect the interests of consumers, in technology should be led by the Society, the development of industry standards, especially the standardization of technical performance indicators, in order to standardize the market, promote the technical progress of powder equipment enterprises