Fully-automatic micro powder screening method with feedback function

Abstract

The invention discloses a fully-automatic micro powder screening method with a feedback function. In the method, a micro control processor is adopted for generating the random number statistics in normal distribution meeting the standard micro powder granularity, the open degree of an electric control regulation valve is controlled, then, the current granularity distribution data fed back by the equipment are analyzed according to the real-time granularity, the micro control processor is used for carrying out statistics on the current received granularity distribution statistics, the average value and the standard deviation of the current normal distribution statistics are calculated, the results are compared with the standard normal distribution statistics, and a group of new random number sequences are newly generated for correcting the current received normal distribution statistics. Through such as a circulation control system, the sorted granularity precision possibly meets the average value and the standard deviation of the standard normal distribution. When the current micro powder concentration fed back by a real-time granularity sensor is lower than the preset critical value, and the control system can be automatically switched to the setting of the next micro powder granularity, so the fully-automatic screening covering the whole micro powder granularity range is realized.

Description

technical field [0001] The invention relates to a method for screening and differentiation, that is, a method for sorting micropowders with different particle sizes, in particular to a fully automatic screening method for silicon carbide micropowder with feedback. Background technique [0002] In nature, the hardness of silicon carbide is second only to natural diamond and a kind of black corundum. After crushing, silicon carbide particles are high-quality raw materials for the abrasives industry. Silicon carbide particles are commonly referred to as "silicon carbide micropowder" in the industry, and can be used as grinding materials for wire-cutting of silicon wafers required for the production of transistors, integrated circuits and solar cells after being precisely graded by hydraulic power according to their particle size. Silicon carbide micropowder products required for wire cutting of silicon wafers have high requirements for grading accuracy and consistency. The grad...

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Problems solved by technology

[0014] Due to the limited upper and lower running area of ​​the rotor of the glass rotameter 5 and the length of the corresponding scale, and there is an error in the indication (manual visual) reading, its actual accuracy level is low; Experience, greatly affected by experience, emotion, physical strength, etc., the accuracy of the regulating valve is poor, and it varies from person to person. In order to ensure that the overflow flow of water will not be mistaken for particle D due to overshooting 3 (corresponding to the upper boundary of the standard deviation), or the particle D 94 (corresponding to the lower boundary of the standard deviation) above will lead to the failure of this water overflow classification. The common practice of operators in actual production is to choose the mean value of the normal distribution statistical data, that is, D 50 As a fixed value for constant flow control, doing so will cause the following two defects:

[0015] ①In the process of water overflow classification, the allowable flow range of the classification label particle size cannot be traversed, which will inevitably lead to D 3 ~D 94 Micropowder particles within the qualified range are not fully screened and overflow, resulting in waste of resources and low yield;

[0016] ②Constant flow control in the process of water overflow classification can easily lead to the formation of stratification of the micro-powder slurry, which can easily cause the gradual hardening of the micro-powder slurry, thereby increasing the time of water overflow sorting, resulting in an increase in the proportion of energy consumption and water consumption

[0021] 1. The above system periodically changes the flow rate monotonously (up or down) according to the "stepped sawtooth" shape of the opening of the electronically controlled valve, so that the flow rate can traverse all the flow rates within the target specification. However, such periodic changes in the flow rate correspond to The particle size distribution of the fine powder is not strictly normal distribution, but closer to the D 3 and D 94 An average distribution statistic within , cannot concentrate the fine powder screening particle size on the center mean value D 50 Nearby, resulting in a decline in the quality of the particle size distribution of the micropowder sorting;

[0022] 2. The above method has set the particle size distribution range expected to be screened in the initial working parameters of the system, including D 3 ,D 50 ,D 94 and other parameters, and then the system defaults that the sorted micro-powder meets the set range; however, in some special working environments, such as overflow tank outlet congestion or overflow tank inlet pipe damage, the fixed working state of the system will be broken, which will cause the sorted fine powder to not meet the preset value

[0023] 3. The above-mentioned system judges whether the currently screened particle size has been completed according to the fixedly set grading time. The grading time is set according to the particle size grading time of previous experiments as a reference; however, in the industrial environment, every time There may be differences in the working parameters, which will cause the difference between the actual grading time and the given reference grading time; at this time, if the given sorting time is set too short, the current sorting will be incomplete, resulting in The waste of fine powder; if the setting is too long, it will reduce the screening efficiency of the system

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