快速模具集成系統(tǒng)精度保證體系研究-外文文獻

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The fast mould integrates the systematic precision and guarantees that the system is studied Summary : Recommend with RP fast of technology and cast maturity manufacture functional CAE system of products of craft, have analysed the factor influencing precision of the products, has proposed analysing the precision at stage of three main shaping with the non-linear finite element, adopt pattern-recognition theory, error theory, neural network method to deal with the error and feedback the problem, carry on error compensate revise and prediction of machining accuracy , improve final method of product quality. Keyword: CAE; RT; Feedback 1 preface Fast prototype technology (& of Rapid Prototyping Manufacturing, abbreviate RP or RPM as, urged directly by the part CAD model, adopt the material accurate prototype or part manufacturing technology which piles up the complicated three-dimensional entity, it is each on the basis of being dispersed /pile up by shaping manufacturing approach not new-type of the principles. Rapid shaping technique already can make and include resin, plastics, paper, paraffin wax, pottery prototype of material successfully very much, but can only do the function experiment in the limited metal used for substituting really of occasion and other type function parts as the functional part. With increase and constant development of technology of demand, fast prototype technology to fast prototype / direction in which the part is being made develop. Utilize RP technological shaping function part, especially metal a kind of main method of part a switch technology, called the fast technology of mould(RT, Rapid tooling). Because traditional mould complicated consuming time and long costly to make course, become design and bottleneck that make often, use RP technology make fast economic mould become RP main motive force of technical development one of. Paul think from PR to RT shaping the second leap of technical development fast. The final purpose of making and shaping is products and service offered and meet the demands. RP technology become front technology of manufacturing industry with a great deal of superiority their, but because limitation restriction extensive application their of material; Traditional technology such as cast, forge and press and develop for a long time, relatively ripe already, but can't meet the needs of fast flexibility of information age , within future one period, must conbine rapid shaping technique and traditional shaping technology together , realize melting quickly and make. 2 RP and RT system integration New product development most high cost have, man-hour longest stage to make the physical model involved, namely prototype manufacture process. RP technology use fast inspection and fast manufactures of different model that part design for mainly. Its basic principle and forming process are: Designed the computer three-dimensional curved surface entity's model of the necessary part by CAD software first , namely electronic model; According to technological requirement, go on the strata it according to certain thickness , turn the original three-dimension electronic model into two-dimentional level information (sectional information); And then carry on certain treatment of the data after the strata, put into and process parameters, produce the numerical control code; Until computer control, numerical control system process by level way process each thin layer and make they automatic sticking and shaping in succession in an orderly manner. RT changes RP prototype into the technology of the tool and mould with various kinds of methods . A method among them is to change the prototype into a pottery type, utilize the method to cast to change into a metal type . And RT manufacture of technology intergration accurate to cast mould method meet modern industry towards many variety, turn batch request of development into with RP prototype, it known as" it is flexible tool " method 5 ,its craft of routes.3 integrated system make functional precision of product analyse Can find out from CAD final precision of product decide by manufacture error at each stage from model to fast prototype course in products.(1)CAD modeling among the course, because of modeling limitation of software, can describe accurate often as to complicated curved surface; (2)STL division of file among the course, because STL file layout mistake that modelling appear in the course sensitive to geometry, mistake these bring through STL file into and get RP modelling among the craft, some influence RP modelling course 3 these of craft seriously, 4 these . And STL file one approach the wanton surface of the room the triangle with level, therefore can only it is at CAD geometrical property among system therefore 3 on part since express approximate therefore. (3)RP craft through to pile up and succeed the object prototype next life material, a lot of craft course is also following the changing of the material , such as FDM and SLA craft. So, the forming process of RP is not only that the machinery of a material piles up course, a height coupling, non-linear thermodynamics course. There are thes influence factor of the precision of this course: Thickness of material parameter, power of laser, strata, scanning route,etc.. (4)Change precision loss of craft depend on and change craft material, conversion method used,etc.. (5)It is the stage that the precision loses the most in the whole craft course that the metal pours the course. Usually, the first several in 10*10 error of stage - 2 mm order of magnitude, and metal solidify size change of course in several even a dozen mm.s of order of magnitude, so, the improvement of the precision of the final products depends on this stage to a great extent. There are thes factor influencing its precision: Material nature, for instance material density, elastic mould amount, heat conduction rate, specific heat, line coefficient of expansion,etc., especially the high temperature hot thing parameter of the metal, the heat transfer characteristic between the metal and type, position of watering, rising head ,etc.. 4 integrate the precision of the systematic products and guarantee the system In the actual production, adopt and try on law come and guarantee final precision of product by mistake often. With the development of technology of the computer and to lowering costs, realizing the requests of digitization, course controllability, necessary to adopt computer integrated manufacturing approach, go on computer simulation emulation study to whole course. CAE (Computer Aided Engineering, project computer auxiliary ) including fairy victory make, flexible manufacturing, at the same time project, make etc. fictitiously. Introduce CAE technology, can draw the craft route again. If regard the middle course as " the black box ", from the craft route to the products of CAD model; This fast, many return circuit error with corresponding course controls and the reponse system.5 errors feedback system research In this CAE system, the error exists at every stages. In CAD modelling , divide in the course of STL file , it is because of the limitation of the modelling software that precision is lost, improve the quality of the software, can reduce the error .At RP prototype fabrication stage , change craft stage and metal to pour stage, involve the hot, strength coupling question, quote the non-linear finite element method , under the three-dimensional flute Karl's coordinate, according to the conservation principle of energy, can draw : (1) Exert hot stress and external force(such as border terms) that temperature cause as the strength load the object and then, try to get total deformation amount. After drawing the errors of every stages, can set up error reponse system . The error reponse system belongs to and closes the control system of the ring . A main content of it is the research that transmits function out of shape. Under it is at flute not three-dimensional Karl coordinate, whether calculate and error after being the out of shape can express for deformation that get for: e(x,y,z) =P ideal (x, y, z)- p reality (x, y,z) (2) If use Δ d (x, y, z) to show the change matrix of the real whole form , g (x, y, z) shows the matrix of controlling, the feedback control of the whole course can be described as: Δ d (x, y, z) =g(x,y,z) e (x, y,z) (3) E (x, y, z) is the algebraical sum of each course, namely, if does not consider the error of CAD modelling course , and e 1 (x, y,z),e 2 (x, y,z),e 3 (x, y,z) show respectively there aren't RP the error, the conversion craft error and the metal of course where the prototypes makes, e(x,y,z) =(x, y,z)+e 3 (x,y, z) (4) The present question is, set up proper g (x, y, z),make Δ d (x, y, z) can disappear to and smaller than range that a certain error allows δ quickly , namely satisfied: <δ of Δ d (x, y, z) (5) G (x, y, z) embodies us to the whole understanding of deforming the course, it must real-time reflection products out of shape with CAD model out of shape coupling relation. And will change with the changes of the border condition out of shape and material parameter . Because the whole course is that more than one variable, complicated three-dimension input more close the control system of the ring non-linearly, perhaps there is a coupling relation between each variable, so, influence g (x, y,z) factor the a lot of,very it it is difficult to be describe with unified mathematics formula, so, the author puts forward the method to use neural network, train g (x, y,z),make Δ d (x, y,z) reach require.Utilize the neural network to have advantage taught oneself to practise, can reduce the error and feedback the demand for the craft data of the question greatly , and benefit systematic expansion. And because close correcting function to the error of system of ring , may cause systematic unstability . Adopt neural self-adaptation of network, learning method, can raise system stupid and getting wonderful. 6 conclusions RP technology is a fast-developing new developing manufacturing technology, RP, and RT integrated system that technology combine together to make functional main method of part with RP technology nowadays, the precision of raising this fast flexible system is nowadays urgent problem that is solved . This text has analysed that influences the factor of the precision of the products in this flexible manufacturing system, have proposed analysing the precision at stage of three main shaping with the non-linear finite element, adopt pattern-recognition theory, error theory, neural network method to deal with the error and feedback the problem, carry on error compensate revise and prediction of machining accuracy , improve final method of product quality. Selected from " the electromechanical project "