Study On Environmental Impact And Characteristic Of Dust Particles In A Machining Workshop

Green manufacturing is a modern manufacturing mode with goals of reducing resource consumption and environmental impacts, which is the embodiment of sustainable development in manufacturing industry, and is also the important technical area and industry development trends concerned extensively by the developed countries.Machining is a typical kind of manufacturing method. Machining systems transform raw material or semi products into qualified final products or semi-final products by machining. Unfortunately, an amount of energy and material is consumed while a lot of solid waste, waste liquid, noise, cutting fluid mist, dust particles are discharged during the machining processes, causing health and security problems in machining workshops. Furthermore, there are a large number of machining workshops in variety industries, so the research on the environmental impacts in machining workshops are important in study on green manufacturing. With the foundation of the National Natural Science Foundation and National Key Project of Scientific and Technical Supporting Programs, this paper mainly studies on the environmental impacts in machining workshop systematicly, and the characteristics of machining dust.Based on the analyses of the system composition of a machining workshop and resource and environmental characteristics of machining systems, a four-layer-structure environmental-impact-oriented operation model of modern machining shops, including operation objective layer, supporting system layer, operation main line layer, bottom-frame layer, and the function of each layer are detailed analysized.Because the environmental impacts in machining workshops are complicated and diversiform, each type of pollunant should be deeply studied, and the problems of machining dust are studied in this paper. On the basis of the analysis of the health harms, security threads and the effect to machine tools and the products'quaulities of machining dust, the architecture framework of machining dust research is built up. And according to the analysis, it is indicated that the exploration of the characteristics of machining dust particles is important, and detailed studies respectively on machine tools and on whole workshop are presented below.According to the analysis, three characteristics of the machining dust emission are concluded and discussed:(1) the dust sources and emission of machining dust are well organized because the machine tools which are the main dust sources are almost fixed; (2) the dust emission process are uncertain and dynamic; (3) the characteristic of spatial distribution during machining, which is detailly studied. Experiments are designed and conducted to measure the dust concentrations at several different spatial spots during machining processes at different cutting speeds near a machine tool. At one hand, intuitive contour lines of the concentrations are acquired through the data process by cubic interpolation. And at the other hand, relative indexes are used to describe the characters of spatial distribution of the dust, the CV(coefficient of variation) for the data at different direction or at the individual direction but different distance away from the cutting spot are calculated. The phenomenons and the experiment results are qualitatively discussed based on the energy transition and airflow fields according to numerical simulation.The machining dust, especially whose sizes are small, can remain suspended in the air for long time and have marked concentration gradients in workshop. The dust distribution states are dynamic in both temporal and spatial dimensions, and the machining workshops have diversified architectural structures, complex working conditions. According to these features, after analysis of the static and dynamic influence factors, this paper proposes a method and establishes a model to estimate the fine dust particles distribution based on COwZ(COMIS(Conjunction of Multizone Infiltration Specialists) with sub-Zones)model when only dry cutting is processed just needing various working parameters. And two key technologies are discussed: the description of the machine tools using sub-zones of COwZ model considering the local obstacle effects of machine tools themselves; description and implementation of dynamic process of cutting dust emission with a new concept of equivalent source strengths. At last, multi-point experiments in a hybrid ventilation machining workshop prove the method is practical. Good agreement was observed between the estimation results and the experimental measurements for the investigated conditions.